Dissertations / Theses: 'Cormorant'

1

Winney, Bruce Joseph. "Cormorant population genetics and Turaco phylogenetics." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285767.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Engström, Henri. "Effects of Great Cormorant Predation on Fish Populations and Fishery." Doctoral thesis, Uppsala University, Department of Evolutionary Biology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1506.

Full text

Abstract:

The strong increase in number of Great cormorants Phalacrocorax carbo in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors.

Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community.

Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants.

In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.

APA, Harvard, Vancouver, ISO, and other styles

3

Engström, Henri. "Effects of great cormorant predation on fish populations and fishery /." Uppsala : Acta Universitatis Upsaliensis : Univ-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5164-0/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Botha, Philna. "The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12823.

Full text

Abstract:

Includes bibliographical references.
The bank cormorant Phalacrocorax neglectus is a seabird endemic to the south-western coast of southern Africa and the Benguela Upwelling System and has suffered a decline of more than 50% over three generations. Main threats include displacement by Cape fur seals Arctocephalus pusillus, direct human disturbance, pollution, climate change and food shortage. This thesis focuses on the bank cormorant’s response to food shortage, both directly and indirectly. Four colonies (Jutten Island, Dassen Island, Robben Island and Stony Point) were studied in terms of responses on population level in relation to the spatial distribution of prey surrounding the various colonies, foraging behaviour and breeding success. First, I tested the response of the bank cormorant ’ s population dynamics in relation to the availability of West Coast rock lobster Jasus lalandii in different spatial scales around three colonies (Jutten Island, Dassen Island and Stony Point) over a subset of years. I found that birds at Dassen Island showed the strongest response to the availability of rock lobster. Birds also showed strongest response to the availability of rock lobster in an accumulative distance around colonies, and their largest response was to rock lobster within 30 km distance from the colony. Various aspects including the life - history traits and moulting stages of this particular rock lobster species may be the reason to this response. Second, I present foraging effort data of bank cormorants in localities known to be situated in areas with different prey availability. I found that at Jutten Island, situated in an area where West Coast rock lobster have dramatically decreased, bank cormorants spent significantly longer time at sea than at Robben Island and Stony Point, which were situated in areas where rock lobster were known to be abundant at the time of the study. Third, I tested the effect of food availability on the breeding success of bank cormorants at Jutten Island, Robben Island and Stony Point. There was no significant relationship between food availability and the survival probability of the birds. The number of chicks fledged per successful nest, however was significantly related to the availability of rock lobster during the relevant breeding season, as well as during the relevant month of hatching.

APA, Harvard, Vancouver, ISO, and other styles

5

BUTTU, SIMONE. "Impatto del cormorano Phalacrocorax Carbo Sinensis sulle produzioni ittiche delle lagune sarde." Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266568.

Full text

Abstract:

The work aims to study the feeding habits of the Great Cormorant (Phalacrocorax carbo sinensis, (Blumenbach, 1798), a species wintering in the transitional environments of Sardinia, and to assess the impact of the cormorants colony on fish stocks, considering the different ecological and economic aspects. During the 2012-2015 period, several monitoring and censuses were carried out, in order to assess and identify the roost or feeding areas with the largest number of cormorants in the different lagoons examined. Numerically, during the three years was observed a significant increase in the number of individuals (rk, p <0.05), which was more than 40% between the first monitoring conducted in 2012 and those 2014. Indeed, in December 2011 was recorded a peak of 9637 animals while in December 2014, there were 13536 individuals. A total of 1402 bird flocks of Great Cormorant wintering in the Cabras and Mistras lagoons (central-western Sardinia), in the S'Ena Arrubia lagoon (southeast of Oristano), in the Sant'Antioco lagoon (south-west Sardinia), in the Santa Gilla lagoon (near to Cagliari), in the Colostrai lagoon (southeastern coast of Sardinia), in the Sa Praia pond (south-east coast of Sardinia) were analysed. Through the morphological analysis of undigested hard structures, such as otoliths, it was possible to describe the preyed species, their size and biomass and, thus, the average daily consumption of cormorants. The trophic spectrum was dominated almost exclusively by euryhaline, gregarious fish species. Mugilidae, and particularly Liza ramada, were the most important prey with a very high percentage index of relative importance (%IRI). The average Daily Food Intake (D.F.I.) for the different lagoons examined was estimated to be equal to 386.8. ± 31 g / day. Specifically, the highest daily requirement was found in the Cabras lagoon with a value of 478.4. ± 18 g / day (Buttu et al., 2013a). The overall amount of biomass preyed by the cormorants during the entire wintering season was estimated over 500 tons. The results obtained by the model applied to a predation economically and ecologically acceptable, specifically, indicate that predation in the Cabras lagoon is outside of economically sustainable levels. This kind of study represent a fundamental step for the development of integrated management plans and protection measures, taking into account both the production requirements, and the environmental factors related to these important ecosystems.

APA, Harvard, Vancouver, ISO, and other styles

6

Warke, Gillian M. A. "The ecology and diet of the cormorant Phalacrocorax carbo carbo (L.) in Northern Ireland." Thesis, University of Ulster, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260486.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Childress, R. Brooks. "Breeding biology and ecology of the great cormorant (Phalacrocorax carbo lucidus) at Lake Naivasha, Kenya." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/29776.

Full text

Abstract:

This thesis examines breeding season timing and seasonal declines in reproductive success in piscivores nesting inland near the equator. Also explored are the effects of sexual character intensity and nest-site characteristics on breeding timing, fecundity and mate choice, as well as the effects of resource partitioning between two similar piscivores. P. carbo lucidus is a relatively common, but little-studied, piscivore of sub-Saharan Africa. Lake Naivasha (0Â° 46' S) is reputed to be seasonally-constant in fish production. The colony studied was newly-established in 1995, the first year of the two-year study. At Lake Naivasha, P. carbo lucidus bred primarily during April-June. There was no evidence of a consistent increase in prey in the lake during this period, and the timing did not appear to result from any other consistent environmental-response adaptation. However, the onset of the main rains appeared to be an important stimulant. Based on studies by others, this subspecies breeds during April-June throughout sub-Saharan Africa, irrespective of the local rainfall regime or differences in photoperiod trend. While nesting at Lake Naivasha, a large portion of the colony appeared to forage at other locations. It is suggested that breeding timing at Lake Naivasha may be controlled by the combination of an increase in prey abundance generally throughout sub-Saharan Africa during April-June, the subspecies' nearly 12-month endogenous reproductive cycle, and the onset of the main rains. A significant seasonal decline in reproductive success was observed. Combining the two years, the mean number of chicks fledged by the first third of pairs to start laying (2.9) was significantly greater than that of the last third (1.2). The primary reason appeared to be the greater age (and experience) of the early-breeding pairs. Egg or chick predation did not seem to be an important factor, even for late breeding pairs. Breeding interference by hungry chicks from earlier broods appeared to be an important factor limiting the reproductive success of late-breeding pairs. In the first year of the new colony, the earliest-breeding pairs (first third) preferentially selected canopy-top nest sites (76%) vs. sites below the canopy (24%). They also built significantly larger nests than later-breeding pairs. Canopy-top locations and larger nests had significant positive effects on brood size and fecundity in the colony's first year but not in its second year.

APA, Harvard, Vancouver, ISO, and other styles

8

Meyer, Corlia. "The endangered bank cormorant Phalacrocorax neglectus: the heat is on : understanding the effect of climate change and associated environmental variable changes on the breeding biology and population dynamics of the bank cormorant in the W. C., S. A." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13358.

Full text

Abstract:

Includes bibliographical references.
The bank cormorant Phalacrocorax neglectus was listed as ‘Endangered’ in 2004, following a decrease of more than 60% in the total population from 1975-2011. It ranges from central Namibia to the Western Cape, South Africa, with most of the population occurring on offshore islands in Namibia. The main reason for this study was to determine if climate change could be identified as a factor which has influenced the decreasing numbers of bank cormorants. This involved research on the heat stress behaviour, breeding success and population trends of the bank cormorant in the Western Cape, South Africa. High environmental temperatures resulting in heat stress and storms with associated extreme environmental variables was predicted to cause breeding failures, decreasing breeding success. As a result, climate change can also affect long-term trends in the adult population of the bank cormorant, and this was examined using the population data of nine bank cormorant colonies in the Western Cape, South Africa. A link existed between ambient and operative temperature, and the latter was used for statistical analysis. Mean operative temperatures of over 30°C were experienced. Temperatures were highest at the bank cormorant colony at Robben Island when three colonies were compared (Robben Island, Jutten Island and Stony Point). Increased environmental temperatures resulted in the average bank cormorant increasing its time spent employing thermoregulatory behaviour. Bank cormorants were shown to start gular fluttering at 21°C on average and spend all their time gular fluttering when they experienced an operative temperature of 34.2°C or higher. The birds also started employing this thermoregulatory behaviour at a lower temperature when on eggs or small chicks. During the study period, the breeding success of the bank cormorant was not impacted by high temperatures at the three bank cormorant colonies studied. Wave and wind action, associated with storms, resulted in a lowered reproductive output during the breeding seasons of 2012 and 2013. Both incubation success and chick rearing success did not differ significantly between 2012 and 2013 for the three bank cormorant colonies at Robben Island, Jutten Island and Stony Point. The study of long-term trends in colony sizes of nine bank cormorant colonies in the Western Cape, South Africa revealed a decrease in the bank cormorants breeding population. The decrease could not be directly associated with climate change in the region. An increase in the mean maximum temperatures and a decrease in the annual rainfall did not affect the bank cormorant numbers, but rather the fecundity. This resulted in a lagged effect of climate change on the bank cormorant population. Climate change and extreme weather events can cause massive breeding failures.

APA, Harvard, Vancouver, ISO, and other styles

9

Kelley, Adam. "A population survey and foraging analysis of the Double-crested cormorant (Phalacrocorax auritus) on the Santee lakes, South Carolina." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1220474447/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Cummins, James B. "Adrenergic and Cholinergic Regulation of Cardiovascular Function in Embryonic Neotropic Cormorants (Phalacrocorax basilianus)." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984219/.

Full text

Abstract:

Investigations of cholinergic and adrenergic tone on heart rate (fH) and mean arterial pressure (Pm) during embryonic development have been conducted on numerous avian species. While these investigations have documented that adrenergic tone, a continuous stimulation, on fH and Pm is vital to embryonic development in the birds studied to date, development of cholinergic tone on fH has been shown to vary even within species. Further, past studies have been bias to focus primarily on precocial species while altricial species remain poorly understood in this context. The goal of this investigation was to investigate the role of cholinergic and adrenergic tone on fH and Pm of an altricial species, the neotropic cormorant (P. brasilianus) to address this bias. The embryonic neotropic cormorant possesses B-and-a adrenergic tone on fH and Pm at 70% and 90% incubation while cholinergic tone on fH occurs at 90% incubation. This pattern of control is similar to that previously reported for several species of precocial birds suggesting the development of tonic cardiovascular regulation may be conserved across avian taxa.

APA, Harvard, Vancouver, ISO, and other styles

11

Fildán, Radim. "Ekonomické aspekty ochrany kormorána velkého." Master's thesis, Vysoká škola ekonomická v Praze, 2011. http://www.nusl.cz/ntk/nusl-71917.

Full text

Abstract:

In my thesis I am dealing with problem of predation of great cormorant on fishery supplies in the Czech Republic. In the first part I explain the problem, describe historical development and current status. I also mention situation in other EU countries, which does have some characteristics similar with the Czech Republic. In the end of the first part I will quantify damage caused by cormorant and I will show how this damage could be estimated. In the second part I am applying scheme of institutional analysis called Institutional Analysis and Development. Firstly I will explain this scheme and then I will apply it on the problem of great cormorant in the Czech Republic. Aim of my thesis is to find a recommendation how organizations and institutions should be set in order to help to resolve this issue.

APA, Harvard, Vancouver, ISO, and other styles

12

Pūtys, Žilvinas. "Great Cormorant Phalacrocorax carbo sinensis diet and its effect on the fish populations and their community in the eutrophic Curonian Lagoon ecosystem." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20121130_091544-23785.

Full text

Abstract:

The rapid expansion of Great Cormorant populations during the second part of the 20th century has caused many conflicts, mostly with fisheries. Cormorants are often considered as important reason for depleted fish stocks, although evidences are often insufficient. This study of the Great Cormorant diet took place in the largest Lithuanian colony near Juodkrantė. Important for the impact evaluation cormorant nutrition aspects, including diet composition, its temporal variation and feeding selectivity, were determined. The reliability of pellet analysis for quantitative dietary assessments was evaluated for the first time using a stable isotope mixing model. Great Cormorant impact on spatial fish distribution was also assessed for the first time. Long-term fish community monitoring data were used for Cormorant impact assessment in the Curonian Lagoon. The results of our study are important for providing improved assessments of the long-term effects of Cormorants on fish communities in large, complex, highly productive aquatic systems. The practical significance of this study is its evaluation of competition between cormorants and commercial fishermen, which enables to substantiate the need to regulate cormorant population. Assessments of Cormorant impact on invasive Round Goby populations is also important.
XX amžiaus antroje pusėje didžiųjų kormoranų populiacijos Europoje staigus augimas sukėlė eilę konfliktų, daugiausia su žvejais ir žuvų augintojais. Kormoranai dažnai kaltinami dėl mažėjančių žuvų išteklių, tačiau moksliniais tyrimais pagrįstų įrodymų dažnai trūksta. Šiame tyrime buvo tiriama didžiųjų kormoranų mityba didžiausioje Lietuvoje Juodkrantės kolonijoje. Darbe buvo nustatyti svarbūs kormoranų poveikio vertinimui mitybos aspektai – raciono sudėtis ir jos kitimas laike, mitybos selektyvumas. Pirmą kartą buvo įvertintas atrajų analizės metodo patikimumas raciono sudėties kiekybiniam vertinimui, naudojant stabiliųjų izotopų sudėties analizės metodą. Taip pat pirmą kartą buvo vertinamas didžiųjų kormoranų poveikis žuvų populiacijoms erdvėje. Remiantis daugiamečio monitoringo duomenimis, buvo įvertintas kormoranų poveikis žuvų populiacijoms Kuršių mariose. Šio tyrimo rezultatai leidžia geriau įvertinti didžiųjų kormoranų ilgalaikį poveikį žuvų bendrijoms didelėse sudėtingose aukšto produktyvumo vandens sistemose. Praktinę vertę šiame darbe turi kormoranų ir žvejų verslininkų tiesioginės ir netiesioginės konkurencijos įvertinimas, leidžiantis pagrįsti kormoranų populiacijos reguliavimo priemonių tikslingumą. Svarbus praktiškai yra ir kormoranų poveikio invazinio juodažiočio grundalo populiacijai įvertinimas.

APA, Harvard, Vancouver, ISO, and other styles

13

Felicia, Skorsdal. "Har det skett en förändring i abborrens (Perca fluviatilis) tillväxt i sjön Tåkern mellan år 1978 jämfört med år 2019?" Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166765.

Full text

Abstract:

The growth in perch (Perca fluviatilis) is generally slow but varies depending on living conditions. For instance, growth is more rapid in warmer water temperature and when there is reduced intra- and interspecific competition for food. The cormorant (Phalacrocorax carbo) was established in Lake Tåkern in 1994 and could possibly have an effect on the growth of perch due to predation of small perch and competition for food with larger perch. The aim of this study was to examine whether the growth of perch had changed from year 1978, when a previous study on perch was preformed, to a recent fish survey in 2019 in lake Tåkern. The aim of the study was to assess if any changes in growth could be explained by predation and competition from cormorants. The aim of the study was also to examine whether there was a difference in growth between females and males. The age was determined by using the opercular bone and an age analysis was done to compare the growth between year 1978 and 2019. The results showed that the growth of 1-3-year-old perch was higher in year 1978 than in 2019. This was contrary to the expected outcome, that the predation from cormorants should had decreased competition for young perch in 2019. Previous studies on perch have shown a difference between males and females with an age over 2 years old. However, by the results there is no support that differences between males and females have affected the difference in growth at ages 1-3 years old between 1978 and 2019. As there was no difference between the sexes, any difference in growth between 1978 and 2019 could not be explained by an altered sex ratio. Since there were only a few older individuals 2019 comparison of growth for individuals over 4 years old were not possible to do. The conclusion is that there was no support that cormorants reduced the competition for smaller perch. Cormorants could possibly have contributed to low number of older individuals in 2019.

APA, Harvard, Vancouver, ISO, and other styles

14

Passuni, Saldana Giannina Paola. "A bird-eye view on the spatio-temporal variability of the seasonal cycle in the Northern Humboldt Current System : the case of Guanay cormorant, Peruvian booby and Peruvian pelican." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT161/document.

Full text

Abstract:

Le Système Nord du Courant de Humboldt (SNCH) est le lieu d’une forte activité biologique due à un upwelling côtier intense. Il abrite l’une des plus grandes populations de l’anchois du Pérou soumis à la plus grande pêcherie monospécifique au monde. Le SNCH héberge aussi de grandes et variables, populations d’oiseaux, composées de trois espèces sympatriques productrices de guano : le cormoran guanay (Phalacrocorax bougainvillii), le fou péruvien (Sula variegata) et le pélican péruvien (Pelecanis thagus), qui se nourrissent principalement d’anchois. Dans ce travail, nous examinons les fluctuations de ces trois populations d’oiseaux marins, en nous concentrant sur le cycle saisonnier de leur reproduction, pour aborder les questions suivantes : Dans quelle mesure les saisonnalités de reproduction diffèrent elles entre espèces ? Dans quelle mesure sont-elles plastiques dans le temps et dans l’espace ? Qu’est ce qui, des conditions environnementales et des activités anthropogéniques affecte le plus la reproduction des oiseaux marins ? Nous abordons ces questions en utilisant des données de présence de reproducteurs (1) dans 30 sites péruviens répartis entre 06°S-18°S (2003-2014) ; et (2) dans un site, pendant trois périodes (1952-1968, 1972-1989, 2003-2014). Nous utilisons des covariables environnementales décrivant les conditions océanographiques, l’abondance, l’accessibilité et la condition des proies, ainsi que des covariables décrivant la pression de pêche. Nous utilisons des modèles d’occupation multi-saisonniers pour caractériser la saisonnalité de la reproduction et la relier aux covariables environnementales. Nous utilisons aussi des analyses en composantes principales fonctionnelles pour classifier les différences de saisonnalité entre sites, et des forêts aléatoires de régression pour analyser la contribution relative des covariables à la variabilité de la saisonnalité de reproduction.Nous mettons en évidence qu’en moyenne, la reproduction démarre au cours de l’hiver austral / début de printemps et prend fin en été / début d’automne, ce patron étant plus marqué chez les fous et pélicans que chez les cormorans. La reproduction est calée dans le temps de telle sorte à ce que les jeunes prennent leur indépendance lorsque les conditions de production primaire, d’abondance et d’accessibilité des proies sont maximales. Ce patron est unique en comparaison avec les autres écosystèmes d’upwelling et peut être expliqué par les fortes abondances absolues de proies disponibles tout au long de l’année dans le SNCH.La saisonnalité de reproduction diffère entre les sites de nidification. Les oiseaux se reproduisent plus tôt et avec de plus fortes probabilités lorsque les colonies sont plus grandes, situées sur des îles à moins de 20 km des côtes, aux plus basses latitudes, et présentant une production primaire plus élevée. Alors, la saisonnalité de la reproduction est davantage influencée par les conditions environnementales locales que par les gradients environnementaux de grande échelle.Les oiseaux marins adaptent aussi la saisonnalité de leur reproduction aux changements drastiques causés dans l’écosystème par les changements de régime. Les cormorans font preuve de la plus grande plasticité, en modulant la date te l’amplitude de la saisonnalité de leur reproduction, cela est probablement permis par leur plus grande flexibilité de fourragement. Les dates et amplitudes fixes observées chez les fous peuvent être liées aux spécificités de leur stratégie de fourragement et à des changements de proies lorsque le stock d’anchois est bas. Les différences spécifiques dans les adaptations de la saisonnalité de reproduction permettent aux oiseaux de profiter différemment des conditions locales de proies, et de faire face aux changements de régime avec des stratégies différentes. Une méthodologie de capture-recapture en parallèle des comptages mensuels est proposée pour élargir les horizons de l’évaluation des dynamiques d’une population
The Northern Humboldt Current System (NHCS) is a place of a high biological activity due to an intense coastal upwelling. It supports one of the biggest forage fish populations, the Peruvian anchovy, and the world-leading monospecific fishery in terms of landings. The NHCS also hosts large, although variable, seabird populations, composed among others by three guano-producing sympatric species: the Guanay cormorant (Phalacrocorax bougainvillii), the Peruvian booby (Sula variegata) and the Peruvian pelican (Pelecanus thagus), which all feed primarily on anchovy.In this work we reviewed the fluctuations of these three seabird populations, focusing on the seasonal cycle of their breeding, to address the following questions: How different are the seasonality of reproduction among species? To what extent may they be plastic in space and time? What from the natural environment and the anthropogenic activities impact more the breeding of seabirds?We addressed these questions using the monthly occupancy of breeders (1) in >30 Peruvian sites between 06°S and 18°S and from 2003 to 2014; and (2) in one site during three decadal periods (1952-1968, 1972-1989, 2003-2014). We also used environmental covariates from satellite and at-sea monitoring such as oceanographic conditions, prey abundance, availability and body conditions, and fisheries pressure covariates. We used multiseason occupancy models to characterize the seasonality of breeding and relate it with environmental covariates. We also used functional principal component analysis for classifying the differences in seasonality among sites, and random forest regression for analyzing the relative contribution of covariates in the variability of the seasonal breeding.We found that in average seasonal breeding mainly started during the austral winter/ early spring and ended in summer/ early fall, this pattern being stronger in boobies and pelicans than in cormorants. The breeding onset of seabirds is timed so that fledging independence occurs when primary production, prey conditions and availability are maximized. This pattern is unique compared with other upwelling ecosystems and could be explained by the year-round high abundances of anchovy in the NHCS.The average seasonal breeding may differ among nesting sites. Seabirds breed earlier and are more persistent when colonies are larger, located on islands, within the first 20km of the coast, at lower latitudes and with greater primary production conditions. These results suggest that in the NHCS, the seasonality of breeding is more influenced by local environmental conditions than by large-scale environmental gradients. These results provides critical information to a better coordination of guano extraction and conservancy policies.Seabirds may also adapt the seasonality of their breeding to drastic ecosystem changes caused by regime shifts. We found that the three study species exhibited a gradient of plasticity regarding the seasonality of their breeding. Cormorants showed a greater plasticity, modulating the timing and magnitude on their breeding seasonality. This is probably authorized by the greater foraging flexibility offered its great diving capacities. Fixed onset and magnitudes of breeding in boobies may be related to their specific foraging strategy and/or to changes of prey items when anchovy stock was low. We also suggested that boobies may adapt other fecundity traits as growth rate of chicks to lower abundance of anchovy.The specific differences in the adaptation of seasonal breeding allow seabirds to take profit differently from local prey conditions or to face differently regime shifts. Further researches, implementing a large-scale capture-recapture methodology in parallel with monthly census, are proposed in order to fulfill gaps in the basic knowledge on vital traits (adult survival, first age at reproduction, and juvenile recruitment) which are critical parameters to evaluate the dynamic of a population

APA, Harvard, Vancouver, ISO, and other styles

15

Spjern, Victor. "Hur påverkar storskarv (Phalacrocorax carbo) och skäggdopping (Podiceps cristatus) fisksamhället i grunda, näringsrika sjöar?" Thesis, Linköpings universitet, Biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166546.

Full text

Abstract:

Piscivorous birds are an integrated part of lake and coastline ecosystems. Despite decades of research it is yet unclear what influence fish eating birds have on the fish community. The aim of this literature study was to focus on how two fish eating birds, Great Cormorant and Great Crested Grebe, influence the fish community in shallow and eutrophic lakes. Different types of analysis methods have been used when doing research on the subject, including pellet analysis, stomach content analysis, tagging of fishes by “PIT”-techniques and analysis by observation. Results show that conclusions by studies tend to vary, but generally higher bird density, lower water temperature and a relatively high turbidity contribute to a higher influence on the fish community. Both bird species are opportunistic in their choice of food and catch prey of the species that occur locally. Both species also limit themselves in the prey size, but the choice vary over seasons because of water temperature and the birds requirements in association with breeding and migration. The significant level of influence seems to be when predation is conducted on younger and smaller fishes. The influence on the fish size can also be indirect, where predation on smaller individuals prevent fishes from becoming older and bigger. As studies tend to deviate in conclusion, no general answer to this issue can be given at present. Comprehensive research with several years of full control over both fish-and bird population is needed to find the proper conclusion.

APA, Harvard, Vancouver, ISO, and other styles

16

Hansen, Oliver Kai. "Can cormorants be used as indicators of local fish abundances? : A diet study of cormorants on Gotland." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-447637.

Full text

Abstract:

Human wildlife conflicts can represent missed opportunities for ecological monitoring, including tracking invasive species. The great cormorant Phalacrocorax carbo sinensis is the centre such a conflict, where the lack of concrete scientific evidence is often replaced by anecdotal evidence, leading to the vilification of these birds. The primary aim of this study was to assess the extent of the overlap between cormorant diet and the fish the fishermen are allowed to catch on the North West coast of Gotland, the Baltic seas´ biggest island. To assess cormorant diet, the otoliths in the cormorant pellets were analysed. Secondary aims included assessing the potential to use cormorant diet as a proxy for local fish abundances by comparing it to monitoring fisheries in the same area. Highly contentious species only included cod, herring and flounder, none of which were commonly consumed by cormorants. Cormorants and the monitoring fisheries found comparable proportions of all species except for flatfish herring sprat, sculpin. We conclude that the cormorant poses a relatively low risk to the fishing industry on the North Western coast of Gotland and that they could potentially be used as a sentinel for local fish abundances, including tracking invasive species such as the round goby.

APA, Harvard, Vancouver, ISO, and other styles

17

Oskarsson, Conny, and Bengt-Erik Yngve. "Äter Mellanskarv i Sommen det unika beståndet av röding och öring?" Thesis, Linköping University, Department of Thematic Studies, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2314.

Full text

Abstract:

Detta är ett naturvetenskapligt arbete som omfattas både av en kvantitativ och en kvalitativ undersökning. Syftet med arbetet är att undersöka mellanskarvens födoval i sjön Sommen, samt att närmare studera huruvida det unika beståndet av röding och öring ingår i mellanskarvens födoval. Sommens Fiskevårdsområde har fått tillstånd till skyddsjakt på mellanskarv av Länsstyrelsen och det främsta skälet skulle vara att fågeln prederar röding och öring. Genom att analysera mellanskarvens spyboll och jämföra innehållet med referensfiskar fångade från samma sjö ska vi se om beslutet från Länsstyrelsen är befogat. Insamling av spybollar och referensfiskar utfördes i fält medan analys av spybollar utfördes på laboratorium. I resultatet av undersökningen konstaterades att mellanskarven i Sommen nästan uteslutande äter abborre. I de analyserade spybollarna som omfattas av denna undersökning återfanns inte röding och öring. Detta skulle innebära att Länsstyrelsens beslut om skyddsjakt på mellanskarv i Sommen p.g.a. predation av röding och öring inte är befogad.

APA, Harvard, Vancouver, ISO, and other styles

18

Riordan, Julie Ann. "Competitive Family Dynamics in a Breeding Population of Black-faced Cormorants (Phalacrocorax fuscescens) at Outer Harbour, South Australia." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/366949.

Full text

Abstract:

This study aimed to investigate the competitive family dynamics of breeding Black-faced Cormorants (Phalacrocorax fuscescens) at Outer Harbour, South Australia. Mating and parental care behaviours are complex yet fundamental to family dynamics. Family interactions are highly influenced by access to resources and the degree of relatedness between individuals. Competition between family members is expected to increase when access to resources is limited. Individuals within a family have different degrees of relatedness and thus compete for resources because they do not necessarily share the same reproductive interests. Resource limitation and relatedness are thus sources of intra-familial conflict that was a focus in my study. All family members are affected by resource shortages. Adults insure against reproducing in an uncertain world by laying optimistic clutches. Adults may then play favourites and trim the size of the brood if access to resources decreases. Hatching asynchrony facilitates this brood reduction because adults provide first-hatched core nestlings with physical and developmental advantages over later-hatched marginal nestlings. Core nestlings compete with marginal nestlings by begging and/or using overt aggression to dominate adult food supply, generally resulting in weaker marginal nestlings dying from starvation or siblicide. Marginal nestlings thus bear the brunt of resource shortages.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

APA, Harvard, Vancouver, ISO, and other styles

19

Wright, Gordon Alan. "Cormorants and the Loch Leven trout fishery." Thesis, University of Glasgow, 2002. http://theses.gla.ac.uk/1623/.

Full text

Abstract:

Perceived conflicts between piscivorous birds and commercial freshwater fisheries are common, and such a perception exists at Loch Leven, a wetland of international importance for nature conservation and a famous commercial brown trout Salmo trutta fishery, where Great Cormorants Phalacrocorax carbo have been shot in large numbers. This thesis describes the foraging behaviour of cormorants wintering on Loch Leven. It summarises changes in wintering numbers over a 32 year period, and reviews data on fish populations, fish stocking rates, angling catches and angling effort in order to seek evidence of detrimental impacts of cormorants on the fishery, and beneficial effects of large-scale cormorant shooting. Finally, this thesis considers turnover within the wintering cormorant population, and its implications for cormorant control. Cormorants spent most of the time roosting, and a single peak of feeding activity occurred early in the morning. Compared to early or late winter, cormorants showed higher foraging activity during mid-winter. Both solitary feeding and flock feeding were recorded, with flock feeding predominating. Solitary feeding was distributed over a wide area. The intensity of flock feeding was less evenly distributed, with 36% of grid squares not used. Overall, 78% of flock feeding activity took place in 23% of grid squares and 59% took place in 13% of grid squares. The best predictor of both solitary feeding and flock feeding intensity of use was mean water depth. Mean water depth was also the best predictor of winter brown trout distribution, although winter brown trout distribution was not a predictor of either solitary feeding or flock feeding intensity of use.

APA, Harvard, Vancouver, ISO, and other styles

20

Stone, Laurence Paul. "The development of dive behaviour in the family phalacrocoracidae." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312417.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Valcourt, Julie. "Dynamique spatio-temporelle des cormorandières de la réserve de parc national de l'Archipel-De-Mingan /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2000. http://theses.uqac.ca.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Putman, Brian Seth. "Modeling Flightless Galapagos Seabirds as Impacted by El Nino and Climate Change." NSUWorks, 2014. http://nsuworks.nova.edu/occ_stuetd/24.

Full text

Abstract:

Noteworthy species endemic to the Galapagos Islands off Ecuador are two flightless birds, the Galapagos Penguin (Spheniscus mendiculus) and Flightless Cormorant (Phalacrocrax harrisi). Both adapted increased swimming ability at the cost of flight. This however has limited their ability to find richer feeding grounds in times of low resource availability, or to escape potential predators. Their population numbers, though small, were stable. Stress on this stability has increased since human arrival. Various invasive species from pets, farm animals and rats to even mosquito vectors of avian disease accompanied humans. . El Nino Southern Oscillation or ENSO cycles of warm waters in the Pacific Ocean south of the Equator cause drastic drops in food sources for all Galapagos seabirds. Serious ENSO events in 1983 and 1998 caused some species’ populations to drop by as much as 77%. Periodic less severe cycles may help explain how population recovery has not rebounded to earlier numbers. Reduced chick survival and adult fecundity seem to occur in concert with mild events. With available data and use of a modeling approach, this study focuses and explores their situations. Restoring population stability may include use of models, species monitoring, conservation and limiting invasive species. Usher matrices based on different climate conditions were produced using data combined from current and past census counts and weather. Models are used to compare available census data and test reliable predictors. Climate data from National Oceanic and Atmospheric Administration and the University of Florida provides for testing predictions of current and probable future climate change. Life histories of both species are regarded. Results suggest the current Cormorant population is still stable. The Penguin, however, faces a 20% probability of extinction in 100 years if current conditions remain. Extinction probability rises to 60% if climate change continues to worsen. Interventions such as captive breeding could be suitable for population recovery.

APA, Harvard, Vancouver, ISO, and other styles

23

Gómez, González Victor, and Collado Emilio José Izquierdo. "The Cormoran project: a new concept in commercial aircraft design." Thesis, KTH, Aerodynamik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121357.

Full text

Abstract:

This paper presents a new revolutionary design in commercial aircraft: the conven-tional vertical and horizontal tails are not present as generally known, and their contri-bution to the manoeuvering of the aircraft, namely the presence of the rudder and theelevators, is achieved by locating them at the wingtips and in the canard, respectively.Substituting the horizontal tail with the canard, the possibility of dividing the fuel be-tween the wing (where it is located conventionally) and the canard allows the pilot tochange the center of gravity during the ight with more freedom, while the eect of theelevators continues present. Locating the vertical stabilizers at the wingtips combinesthe eect of the vertical stabilizer and the winglet all in one, with the corresponding lostof weight. In this sense, the aerodynamic, stability and aeroelastic characteristics of anaircraft such as the one described have been analyzed using dierent modules belongingto CEASIOM program, and the results are very encouraging, showing that it is reallyfeasible to change the current concept of the commercial aircraft without penalizing theperformance.

APA, Harvard, Vancouver, ISO, and other styles

24

Skiles, Tom D. "Nutrients, cormorants, and rainbow trout in an urban lake, Reno, NV." abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1456996.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Kuiken, Thijs. "Newcastle disease and other causes of mortality in double-crested cormorants, Phalacrocorax auritus." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32789.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Newson, Stuart E. "Colonisation and range expansion of inland breeding great cormorants Phalacrocorax carbo in England." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325797.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Masiko, Oyena B. "Are Cape Cormorants (Phalacrocorax capensis) losing the competition? Dietary overlap with commercial fisheries." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29731.

Full text

Abstract:

Characterisation of the diet of pelagic feeders can be regarded as key to development of ecosystem-based management plans, conservation of predators as well as understanding of ecological and trophic interactions. Therefore, long term studies on dietary changes provide insights into the nature of competition and overlap between seabirds and fisheries. The Cape Cormorant Phalacrocorax capensis breeds in the Benguela upwelling region of southern Africa. Its population has decreased by over 50% in the three most recent generations resulting in the species being listed as Endangered in the IUCN Red Data List. Its decline has previously been postulated to result from reduced prey availability. In this thesis, I examined and reported on the spatio-temporal distribution of Cape cormorant diet obtained from different colonies over two decades (1988 – 1997 and 1998 – 2007). I further investigated the extent of overlap between the diet composition and sizes of fish eaten by Cape Cormorants and those caught by the purse-seine fishery. Epipelagic fish (Anchovy, Sardine, Horse Mackerel and Redeye) dominated the diet of Cape cormorants at all sites. Anchovy was the most important in the diet in all years except in 1992 and 1993, when Sardine dominated the diet, and in 2007 when ‘other’ fish species (mainly Cape Silverside Atherina breviceps and Southern Mullet Chelon richardsonii) became the most frequently eaten fish. There were decadal variations in the relative numerical abundance of different prey species. Over both decades investigated, the diet was largely dominated by Anchovy and Sardine, with Horse Mackerel contributing more in the second than first decade. There was, however, an increase in the contribution of Anchovy relative to Sardine from the first decade to the second. At all colonies, Cape Cormorants mostly preyed on Anchovies of sizes between 5 and 11cm. Sardines eaten were larger than Anchovies (mostly 11 – 23 cm), with a bimodal distribution in the first decade. However, the few Sardine eaten in the second decade were smaller (4 – 7 cm) perhaps reflecting the length of fish available. There was an overlap in the distribution of fish sizes caught by the fishery and those found in the diet of Cape Cormorants especially in the first decade. However, increased sampling of Cape Cormorant diet is required to more fully understand the extent of competition and overlap with fisheries.

APA, Harvard, Vancouver, ISO, and other styles

28

Kuntz, Grégoire. "Régulations physiologiques chez des grands cormorans, Phalacrocorax carbo, plongeant dans les eaux groenlandaises." Thèse, [Rimouski, Québec] : Université du Québec à Rimouski, 2004.

Find full text

Abstract:

Thèse (M. Sc.) - Université du Québec à Rimouski, 2004.
Rapport présenté à l'Université du Québec à Rimouski comme exigence partielle du programme de maîtrise en gestion de la faune et de ses habitats. Titre de l'écran-titre (visionné le 14 juin 2006). CaQRU CaQRU Bibliogr.: f. 59-65. Publié aussi en version papier. CaQRU

APA, Harvard, Vancouver, ISO, and other styles

29

Le, Gentil Jérôme. "Structuration génétique des populations et spécialisation écologique chez le grand cormoran en expansion géographique en Europe." Rennes 1, 2007. http://www.theses.fr/2007REN1S133.

Full text

Abstract:

The Great Cormorant (Phalacrocorax carbo), actually in expansion is a large colonial piscivorous migrating waterbird. In Europe, two sub-species, carbo and sinensis, are distinguished according to morphological, ecological and geographical criteria. This work has focused on the evolutionary history of populations, the validity of the subdivision in two sub-species, and the ecological specialisation. The main results are: (i) the phylogeographical study shows the existence of a third sub-species in Europe and the convergence of the populations to the western part of Europe; (ii) the analysis of the population structure (microsatellites) show pattern of isolation by distance, with an effect of long-dispersal distance linked to the migratory axis; (iii) the monitoring of the breeding success show that the sinensis subspecies is better adapted to the inland habitat than carbo subspecies
Le Grand Cormoran (Phalacrocorax carbo), est un oiseau colonial piscivore migrateur de grande taille, actuellement en expansion. En Europe, deux sous-espèces, carbo et sinensis, sont distinguées : critères morphologiques, écologiques et géographiques. Ce travail visait à étudier l'histoire évolutive des populations, à tester la pertinence de la sub-division en deux sous-espèces et à vérifier l'hypothèse de spécialisation écologique, grâce à des méthodes moléculaire et de suivi sur le terrain. Les résultats majeurs sont : (i) l'étude phylogéographique (ADNmt) montre l'existence d'une 3^ème sous-espèce européenne et la convergence des populations vers l'ouest de l'Europe ; (ii) l'analyse de la structure de population (microsatellites) montre une isolation par la distance, avec un effet de dispersion longue-distance, en lien avec la migration ; (iii) l'étude du succès reproducteur montre que la sous-espèce sinensis est mieux adaptée au milieu continental que carbo (spécialisation écologique)

APA, Harvard, Vancouver, ISO, and other styles

30

Forzán, María de Jesús. "Pathological effects of Cryptocotyle lingua in double-crested cormorants (Phalacrocorax auritus) treated with dexamethasone." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63258.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Chastant, Jennifer Erin. "POPULATION CHARACTERISTICS OF INTERIOR DOUBLE-CRESTED CORMORANTS BREEDING ACROSS THE SOUTHERN BORDER OF ONTARIO." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-10062008-160410/.

Full text

Abstract:

Interior Double-crested cormorant reproduction was examined on a large geographical scale to evaluate management actions. Three distinct breeding areas across Ontario were selected. Beginning in 2002, over 11,000 pre-fledged cormorants have been marked. During 2006 and 2007, re-observation of banded birds, colony data such as nest, egg, and chick measurements, and island morphology, were collected. Data revealed no significant regional differences in adult size. However, eggs in eastern Lake Ontario (ELO) were larger than North Channel of Lake Huron (NChan) and Lake of the Woods (LOW). Chicks in ELO throughout development were smaller than NChan and LOW. Number of gulls was correlated inversely to cormorant fledge rate. Survival estimates were <20% for young of the year, but increased to >80% after year 2. Elasticity analysis revealed that a 50% reduction in adult survival combined with 100% fecundity reduction would result in a 42% reduction in population growth.

APA, Harvard, Vancouver, ISO, and other styles

32

Davies, John M. "The impact of cormorants (Phalacrocorax carbo L.) on the lower River Ribble fishery, Lancashire." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361521.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Moran, Leah L. K. "Ecosystem Impacts and Space Use of Double-Crested Cormorants in a Southeastern Reservoir System." Thesis, Mississippi State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10841105.

Full text

Abstract:

Double-crested Cormorants are expanding their breeding range to historic wintering and migratory regions, such as Guntersville Reservoir in Alabama. This study lends insight into how cormorants breeding in a temperate ecosystem impact plants, trees, soil and bird communities as well as home range and movement of cormorants during the breeding season and whether they reside on this reservoir year-round. Results suggest that breeding cormorants have a negative impact on this ecosystem and do not move far from colony sites. Stable isotopes from cormorants and prey fish suggest that cormorants are migrating from this system after breeding, potentially to a marine source. This study corroborates past studies of negative impacts of cormorant colonies, and provides novel results of how southeastern cormorants use and move on Guntersville Reservoir. This thesis can provide biologists information on how best to control populations and mitigate impacts on this and other similar southeastern systems.

APA, Harvard, Vancouver, ISO, and other styles

34

Randa, Jacob G. "Diet and Effects of Environmental Stressors on the Altricial Nestlings of Double-Crested Cormorants (Phalacrocorax Auritus)." Thesis, North Dakota State University, 2014. https://hdl.handle.net/10365/26911.

Full text

Abstract:

Double-crested cormorants (Phalacrocorax auritus) are a common species of altricial waterbird found across much of North America. As a piscivorous colonial waterbird, cormorants are often persecuted due to perceived impacts on fisheries. In this study I examined the diet of cormorant nestlings at five cormorant colonies in central North America to answer two questions: 1) Is nestling diet reflective of opportunistic feeding behavior, thus diminishing the likelihood of negative impacts to the fishery? and 2) How do diet and environmental stressors effect the development of cormorant nestlings? By analyzing the caloric content of nestling diet and quantifying environmental stressors such as endoparasite and ectoparasite loads, I found diet was a significant contributor to structural long bone growth in both the wing and tarsus. Diet analysis also corroborated the long held belief that cormorants have highly variable diets reflective of local fish communities and may vary annually as fish assemblages change.
Voyageurs National Park
Ontario Ministry of Natural Resources
Windels, Steve

APA, Harvard, Vancouver, ISO, and other styles

35

Henaux, Viviane. "Dynamique d'une population gérée par l'homme : dispersion, densité-dépendance et destructions hivernales chez le grand cormoran." Montpellier 2, 2006. http://www.theses.fr/2006MON20236.

Full text

Abstract:

Une bonne gestion des espèces en conflit avec l’homme nécessite d’examiner l’interaction entre stratégies de gestion et régulation naturelle. La population nord européenne de grand cormoran s’est fortement multipliée au cours des 30 dernières années, entraînant l’expansion de son habitat du fait de la dispersion d’individus entre colonies. Afin de limiter les dégâts de cet oiseau piscivore dans les piscicultures, la population a été contrôlée à partir de 1992 par des destructions hivernales d’individus. L'objectif de ma thèse était de déterminer l'interaction entre les conséquences intrinsèques de la croissance démographique et les destructions sur la dynamique de la population. Avec un modèle de capture-recapture multiétat combinant réobservations multisite et reprises d’individus bagués, j’ai montré que la dégradation du succès reproducteur et l'augmentation des effectifs a entraîné la dispersion des individus. La prospection permet aux individus qui recrutent de choisir un site plus ou moins éloigné où ils pourront produire plus de jeunes que dans leur site de naissance. Les reproducteurs préfèrent une colonie proche de la précédente afin de profiter de leur expérience avec les sites de nourriture. A partir d'un modèle énergétique tenant compte du budget énergétique journalier des parents et des conditions environnementales, j'ai montré que l’augmentation densité-dépendante de la compétition pour la nourriture dégrade la performance de recherche alimentaire et le succès reproducteur des individus. Combinée aux processus de dispersion, il en résulte une régulation de la croissance de la colonie. Il semble que l’effet des tirs soit partiellement compensé par une diminution densité-dépendante de la mortalité naturelle chez les adultes et les individus de première année. Je suggère que l'intensification des destructions au niveau local permettrait une meilleure résolution des conflits que les quotas nationaux tout en préservant la population de grand cormoran
A good management of species in conflict with man needs to investigate the interplay between management strategies and natural regulation. The North European population of great cormorant strongly multiplied over the last 30 years, leading to the expansion of its breeding range because of the dispersal of individuals among colonies. In order to limit the damages of this fish-eating bird in fisheries, the population was controlled from 1992 as winter culls. The goal of the thesis was to investigate the interplay between intrinsic consequences of the demographic growth and culls on the population dynamics. From a multistate capture-recapture model combinig multisite resightings and recoveries of ringed birds, I showed that declining breeding success and increasing breeding numbers led to the dispersal of individuals. Prospecting allows first-time breeders to disperse to a colony, more or less distant, where they can expect a higher breeding success than in their birth site. Breeders prefer a colony close to their previous site in order to benefit of their experience with foraging sites. From a bioenergetics model considering the daily time-energy budget of parents and environmental conditions, I showed that the density-dependent increase of competition for food alters the foraging and breeding performances of individuals. Combined to dispersal processes, the result is a regulation of colony growth. It appears that the effect of culls was partially compensated by a density-dependent increase of adult and first-year survival. I suggest that the intensification of culls at the local scale will allow a higher reduction of conflicts than national quotas and the preservation of the great cormorant population

APA, Harvard, Vancouver, ISO, and other styles

36

Britton, John Robert. "The impact of cormorants (Phalacrocorax carbo carbo and Phalacrocorax carbo sinensis) on inland fisheries in the UK." Thesis, University of Hull, 1999. http://hydra.hull.ac.uk/resources/hull:7024.

Full text

Abstract:

Cormorants are piscivorous birds with a daily food intake (DFI) of approximately 500 g. They are a protected species under the Wildlife and Countryside Act 1981. In the UK, the number of over-wintering, inland cormorants increased steadily between 1970 and 1987, at a rate of between 5 and 10 % per annum. An increase of 74 % occurred between winter 1987/88 and 1990/91, and the population is still believed to be rising. The population growth was observed in all regions of the UK, on all habitat types. As cormorants exploited new habitats, ornithologists welcomed their increased presence. This contrasts with the views of angling bodies, who assert that the presence of cormorants, feeding daily on their fisheries, has a damaging impact on fish stocks with inevitable financial losses. Due to a lack of effective non-lethal control methods, the angling bodies wish to see the cormorants removed from the protected species list so their inland numbers can be controlled. Ornithologists insist that there is no scientific evidence proving cormorants are damaging to inland fisheries and so are opposed to any culling. A review of previous cormorant studies was undertaken to evaluate information on their ecology, feeding behaviour and predation impact. The general conclusion was no study had been able to prove cormorant predation damages fish populations, because few studies had moved beyond determining the mass of fish removed by the birds over the particular study period. No assessment had been made of the impact of that fish removal on the fish population dynamics and the angling performance of the fishery. This highlighted the requirement for research into the impact of cormorant predation on inland fisheries. This study was formulated to estimate cormorant predation impact on fisheries in a more realistic and robust manner than had previously been undertaken. The principal objective of the study was to integrate fish population and cormorant feeding dynamics data on specific fisheries (study sites) in such a way as to quantify, where possible, the full impacts of the cormorant predation. This required the following criteria at each study site: - evaluation of the historical status of fish and cormorant populations; - determination of the population and community dynamics of the fish stocks; - analysis of the angling effort and angling performance; - identification of the species, and estimation of the numbers and sizes of fish consumed and wounded by cormorants, and comparison with the numbers and sizes of the fish populations present; - determination of the occupancy on, and use by, cormorants at the selected sites. The work programme ran between September 1995 and July 1998, covering three winters of cormorant predation. At each study site, the cormorant feeding dynamics were assessed by detailed feeding observations and cormorant counts. This enabled data to be collected on the species, size and amount of fish being ingested during each foraging bout, and the diurnal and seasonal patterns of cormorant occupancy. As feeding observations were unable to completed at each site everyday, a modelling system was designed, using a Monte Carlo Simulation (MCS), to estimate the number and mass of fish being removed from the site over the whole winter period. The fisheries data were collected by electric fishing, seine netting, hydro-acoustics and angler catch analysis. The actual methods used at each site were dependent upon the physical conditions present. The data were analysed for fish population dynamics, including length frequency of species, year class strength, natural mortality rate and growth indices; and for angling performance, including catch per unit effort and the relative importance of species. Combining site-specific data for the fish species composition, and the length frequency distribution from fisheries surveys and the cormorants' diet, allowed preliminary predation impact assessment. Reconstruction of life tables from the fisheries data allowed integration of the cormorant feeding data from the Monte Carlo Simulation to assess impact in terms of the numbers of fish consumed on subsequent population densities. This enabled the status of the fish population at each study site to be shown, with and without cormorant predation over the three-year period, resulting in a detailed predation impact assessment. The fisheries studied were located in two regions of the UK, the Midlands and the North West of England. This enabled the research to be completed in two distinct geographical areas, with known and established over-wintering cormorant roosts. The Midland study sites were Holme Pierrepont Rowing Course, Colwick Park Trout Lake and the River Trent. The North West study sites were the lower River Ribble and Grimsargh number 3 Reservoir. These sites encompassed cyprinid and salmonid fish populations, and covered riverine and lacustrine fisheries.

APA, Harvard, Vancouver, ISO, and other styles

37

Campbell, Greg Thomas. "Effects of temperature on gular fluttering and evaporative water loss in four sympatric cormorants in southern Africa." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12815.

Full text

Abstract:

Includes bibliographical references.
Climate change continues to cause rising air and sea surface temperatures and changes in precipitation patterns across the globe. Many seabirds will be challenged by increasing temperatures because they must balance conflicting adaptations for dealing with cold environments when foraging and hot environments when nesting. Heat stressed seabirds often gular flutter for thermoregulation, a behaviour that is effective for dissipating heat but expensive in terms of evaporative water loss. This study examined gular fluttering behaviour of four species of southern African cormorants, crowned ( Microcarbo coronatus ), Cape ( Phalacrocorax capensis ), bank ( Phalacrocorax neglectus ), and white-breasted ( Phalacrocorax carbolucidus) cormorants. Results show that gular fluttering is influenced by temperature, body position and body size. Gular fluttering increases with temperature and larger cormorant species spend a greater proportion of time gular fluttering for a given temperature. Threshold temperatures for initiating gular fluttering are lower for large than for small cormorant species. Proportions of time spent gular fluttering are higher when birds are sitting than when crouching over the nest. Water loss shows the same pattern as gular fluttering, with the larger species estimated to lose a higher percentage of their daily water intake. Larger cormorant species can lose as much as 40% of their daily ingested water after eight hours of gular fluttering. These findings indicate that temperature increases from climate change will likely have serious direct impacts on nesting cormorant colonies in southern Africa. Gular fluttering could increase by as much as 25% by 2100 under current projected temperature increases, and increases in water loss could reach nearly 10%. Some species may shift their breeding dates to compensate for increasing temperatures, but if breeding activities are timed to coincide with peaks in their main prey specie s, this may result in poorer diets or increased competition from other species.

APA, Harvard, Vancouver, ISO, and other styles

38

Iznova, Tatjana. "Diversity and ecological properties of Dothideomycetes and Sordariomycetes in alluvial black alder forests and pine forest affected by cormorants." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141230_152629-97973.

Full text

Abstract:

The aim of the study was to investigate the diversity and ecological properties of Dothideomycetes and Sordariomycetes in the alluvial black alder forests and the pine forest affected by cormorants. For the first time in Lithuania, detailed investigations were carried out on the diversity and distribution of Dothideomycetes and Sordariomycetes in the above-mentioned forests. The checklist of the study fungi was complied. 72 Dothideomycetes and Sordariomycetes species new to Lithuania were identified and original descriptions of their morphology were provided. The influence of abiotic factors on the diversity of woody and herbaceous plants fungi was evaluated for the first time in Lithuania. The results of the study enhanced the knowledge about the distribution of Dothideomycetes and Sordariomycetes in the alluvial forests protected in Europe, which may be used to protect the biologic diversity of these habitats. The properties of the diversity and distribution of studied fungi in the pine forest affected by cormorants allow assessing the impact of the hypertrophication, caused by these birds on the pine forest mycobiota.
Darbo tikslas – ištirti dotidėjomicetų (Dothideomycetes) ir sordarijomicetų (Sordariomycetes) įvairovę bei ekologines ypatybes aliuviniuose juodalksnynuose ir kormoranų pažeistame pušyne. Darbe pirmą kartą Lietuvoje detaliai ištirta aliuviniuose juodalksnynuose ir kormoranų pažeistame pušyne dotidėjomicetų ir sordarijomicetų rūšių įvairovė ir paplitimas. Sudarytas šiuose miškuose aptiktų grybų rūšių sąvadas. Išaiškintos 72 naujos Lietuvai tirtų aukšliagrybūnų rūšys ir pateikti originalūs jų morfologijos aprašymai. Pirmą kartą Lietuvoje įvertinta aplinkos veiksnių įtaka sumedėjusių bei žolinių augalų dotidėjomicetų ir sordarijomicetų įvairovei. Darbo rezultatai pagilino žinias apie šių grybų paplitimo dėsningumus Europoje saugomuose aliuviniuose miškuose, kas gali būti panaudota šių buveinių biologinės įvairovės išsaugojimui. Kormoranų pažeistame pušyne nustatyti tirtų grybų rūšinės sudėties ir paplitimo ypatumai leidžia įvertinti šių paukščių sukeliamos hipertrofikacijos poveikį pušyno mikobiotai.

APA, Harvard, Vancouver, ISO, and other styles

39

Wilson, Benjamin Richard. "Improving techniques for quantifying the potential impacts of cormorants (Phalacrocorax carbo L.) and goosanders (Mergus merganser L.) on stillwater and riverine fisheries." Thesis, Liverpool John Moores University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421396.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Holden, Timothy David. "Spatial and temporal variation in the diet and feeding ecology of cormorants (Phalacrocorax carbo L.) at three fisheries in the East Midlands, England." Thesis, Liverpool John Moores University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421408.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Lagström, Christian. "Födosammansättning hos gråsäl (Halichoerus grypus) samt test av flotte för insamling av sälfekalier." Thesis, University of Kalmar, School of Pure and Applied Natural Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-697.

Full text

Abstract:

During the 1960´s and 1970´s the number of grey seals in the Baltic Sea was decreasing rapidly, mostly due to hunting and toxic substances like DDT and PCB. When hunting became less intense and toxic substances decreased in the environment the grey seal population started to increase. Today grey seals are found common in the Baltic Sea and have started to become a big treat and a problem to the fishing industry. The grey seal destroys and enters fishing traps and consumes large quantities of the fish that have been caught.

The knowledge of the grey seal, like abundance and food preferences, is today limited. It is also important to define the position of the grey seal in the ecosystem in the Baltic Sea and to be able to predict changes that could occur if the population would rapidly decrease or increase. This project was therefore started in an attempt to increase the knowledge about the grey seals food preferences. The study was made in tree separate parts. Part one contained analyses of prey remains from stomachs and digestive tract from fourteen individuals put down in two geographically separate areas. The collected material from the seal digestive tract was cleaned and otoliths (hearing stones from fish), scales and back vertebra from fish eaten by the grey seal were sorted out. With the help of hard parts collected from the intestines the food preferences of the seals could be estimated. Eight different species of prey was found. The species were herring (Clupea harengus membras), sprat (Sprattus sprattus), common whitefish (Coregonus spp), perch (Perca fluviatilis), salmon (Salmo salar), trout (Salmo trutta) and roach (Rutilus rutilus). In two of the digestive tracts several individuals of the isopod Saduria entomon were found. No earlier studies describe the isopod as a food source for the grey seals in the Baltic Sea. The findings are therefore unique information. The results showed that during summer the main part of the grey seal diet in the gulf of Sundsvall and in the surrounding coastal area of Hårte was herring and sprat. No significant difference in food preferences was shown between the investigated seals from the gulf of Sundsvall and seals from the surrounding coastal area of Hårte.

The second part was made to investigate if it was possible to build a floating platform that would work as a resting place for the grey seal. The surface of the platform was covered by a layer that keeps the seal scats on the platform so that it could be collected. Otoliths from herring and common whitefish were found on the floating platform. Because the platform could not be under surveillance during the whole study some uncertainties about whether the otoliths found came from grey seal or from resting cormorants or other fish eating birds. However, the otolit size is linearly related to the fish size and this relationship can be used to track the predator. Otoliths from herring taken by grey seals and otoliths found on the platform were significantly bigger than the otoliths originating from the prey of cormorants. The results indicated that the common whitefish size was too big for a full grown cormorant bird to consume. The common whitefish size showed that it probably not had been cormorants that had deposited the otoliths on the platform. The platform method was concluded promising but it needs to be modified in order to work more effective in the future.

In the third part scats were collected from the area of Österåsen to increase the amount of information about the grey seals food preferences.

The knowledge of the grey seals diet in the Baltic Sea is today limited and few similar study’s have earlier been made. The collected scats and otoliths in this project are therefore unique.

2008:Bi 2

APA, Harvard, Vancouver, ISO, and other styles

42

Mathieu, Olivier. "Impact potentiel de la prédation des cormorans à aigrettes (Phalacrocorax auritus) d'une colonie en expansion sur les communautés aquatiques de lacs oligotrophes du bouclier canadien /." Trois-Rivières : Université du Québec à Trois-Rivières, 2005. http://www.uqtr.ca/biblio/notice/resume/24068930R.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Mathieu, Olivier. "Impact potentiel de la prédation des cormorans à aigrettes (Phalacrocorax auritus) d'une colonie en expansion sur les communautés aquatiques de lacs oligotrophes du bouclier canadien." Thèse, Université du Québec à Trois-Rivières, 2005. http://depot-e.uqtr.ca/1514/1/000122644.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Carpentier, Alexandre. "Réponse numérique et fonctionnelle d'un prédateur aux contraintes spatio-temporelles d'utilisation de la ressource alimentaire : le cas du Grand Cormoran et du peuplment ichtyologique du lac de Grand-Lieu." Rennes 1, 2004. http://www.theses.fr/2003REN10135.

Full text

Abstract:

La mise en évidence des facteurs caractérisant une relation prédateur-proie implique le suivi des populations d'un point de vue spatio-temporel, comportemental et quantitatif. La répartition des proies, la communauté piscicole du Lac de Grand-Lieu, suit un gradient de densité centripète décroissant d'une bande littorale étroite vers une zone d'eau libre centrale via une importante surface estivale de macrophytes flottants. La distribution du prédateur, le Grand Cormoran, est peu liée aux densités piscicoles, mais davantage à l'accessibilité à la ressource impliquant des comportements de pêche variables, solitaire ou grégaire. La productivité des macrophytes, tributaires du niveau d'eau, compte parmi les éléments-clés du fonctionnement du système en tant que refuges pour les poissons et obstacles pour les oiseaux. Une simulation du stock piscicole, des prélèvements aviaire et halieutique montrent un équilibre apparent malgré les modifications de l'écosystème dues à l'eutrophisation.

APA, Harvard, Vancouver, ISO, and other styles

45

Lombard, Amanda T. "The thermal implications and ecological consequences of coloration in selected species : tenebrionid beetles (Onymacris bicolor and Onymacris ungui cularis), Cape gannets (Morus capensis) and Cape cormorants (Phalacrocorax capensis)." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/8419.

Full text

Abstract:

Bibliography: leaves 176-192.
The thermal significance of coloration was investigated in two species of Namib Desert tenebrionid beetles and two species of marine birds. Body temperatures and heat fluxes of a black beetle (Onymacris unguicularis) and a beetle with white elytra (Onymacris bicolor) were compared in a wind tunnel in the laboratory. The effects of visible radiation, infrared radiation, conduction, convection, beetle colour and substratum colour on body temperature were analysed. Results showed that body colour has no overall effect on body temperature. Black elytra are warmed more by visible radiation, but colour is not relevant to heat loss by convection, or to heat flux between a beetle and a heated sand substratum, whether by emitted radiation or reflected visible radiation. 0. bicolor absorbs more heat by conduction and free convection from a heated substratum, but differences in shape between the two species may explain this effect. Combining the various modes of heat exchange to simulate natural conditions reveals that the extra heat absorbed by black elytra is readily dissipated by convection, and owing to the increased heating of white beetles from the substratum, heat fluxes between the two beetles balance. Body temperatures of dead and live beetles of both species were also measured in the field. Experiments were conducted on a hot sand substratum in the beetles' natural environment, under both visible (sunny) and infrared (shaded) conditions. Results supported the laboratory experiments, and showed that when temperature differences do occur between black and white beetles, these differences are generally less than 3.5 °C. These differences are small when compared with the ranges of body temperatures experienced by active beetles in the field (± 10 °C). In addition, these temperature differences occur only at low wind speeds (< 2 m s-1). Activity studies in the field showed that beetles choose to be active in high wind speeds, possibly because of the nature of their food source, which is wind-blown detritus. It is concluded that coloration does not have adaptive value in terms of the thermal biology of Namib Desert tenebrionid beetles. Physical properties of the plumages of white Cape gannets (Morus capensis) and black Cape cormorants (Phalacrocorax capensis ) were measured. Black plumages absorb more visible radiation than white plumages in still conditions. However, laboratory experiments with excised plumages showed that at wind speeds of 2 m s-1, cormorant plumages and skins were only 2-3 °C warmer than those of gannets. These differences disappeared at wind speeds of (< 2 m s-1). A biophysical heat transfer model predicted that in still, warm, sunny conditions, cormorants may gain up to 185 of their field metabolic rates, whereas gannets would gain only 42 . Field observations confirmed that nesting cormorants experience greater heat stress than gannets, even though cormorant nests occur in areas of lower micrometeorological temperatures. Cormorants begin to dissipate heat by evaporative water loss (i.e. pant) at lower environmental temperatures than gannets. The thermal consequence of coloration in these two species are that cormorants may have a lower cost of endothermy at temperatures below the thermoneutral zone, but may experience more heat stress during warm conditions; cormorants select cooler and windier nesting sites than gannets; and increased surf ace temperatures of black cormorant plumages may aid evaporative water loss from wet plumages, facilitating wing-drying. However, ptiloerection and wind may interact in the natural environment, negating the differential heating effects of coloration. It is concluded that the thermal implications of colour are negligible in both species, considering the temperate nature of their environment; Colour in both species is best explained by feeding ecology: white coloration is conspicuous to conspecifics and cryptic to prey in plunge divers (gannets), whereas black colour is cryptic to both conspecifics and prey in solitary swimmers (cormorants).

APA, Harvard, Vancouver, ISO, and other styles

46

Iznova, Tatjana. "Dotidėjomicetų (Dothideomycetes) ir sordarijomicetų (Sordariomycetes) įvairovė bei ekologinės ypatybės aliuviniuose juodalksnynuose ir kormoranų pažeistame pušyne." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141230_152613-74783.

Full text

Abstract:

Darbo tikslas – ištirti dotidėjomicetų (Dothideomycetes) ir sordarijomicetų (Sordariomycetes) įvairovę bei ekologines ypatybes aliuviniuose juodalksnynuose ir kormoranų pažeistame pušyne. Darbe pirmą kartą Lietuvoje detaliai ištirta aliuviniuose juodalksnynuose ir kormoranų pažeistame pušyne dotidėjomicetų ir sordarijomicetų rūšių įvairovė ir paplitimas. Sudarytas šiuose miškuose aptiktų grybų rūšių sąvadas. Išaiškintos 72 naujos Lietuvai tirtų aukšliagrybūnų rūšys ir pateikti originalūs jų morfologijos aprašymai. Pirmą kartą Lietuvoje įvertinta aplinkos veiksnių įtaka sumedėjusių bei žolinių augalų dotidėjomicetų ir sordarijomicetų įvairovei. Darbo rezultatai pagilino žinias apie šių grybų paplitimo dėsningumus Europoje saugomuose aliuviniuose miškuose, kas gali būti panaudota šių buveinių biologinės įvairovės išsaugojimui. Kormoranų pažeistame pušyne nustatyti tirtų grybų rūšinės sudėties ir paplitimo ypatumai leidžia įvertinti šių paukščių sukeliamos hipertrofikacijos poveikį pušyno mikobiotai.
The aim of the study was to investigate the diversity and ecological properties of Dothideomycetes and Sordariomycetes in the alluvial black alder forests and the pine forest affected by cormorants. For the first time in Lithuania, detailed investigations were carried out on the diversity and distribution of Dothideomycetes and Sordariomycetes in the above-mentioned forests. The checklist of the study fungi was complied. 72 Dothideomycetes and Sordariomycetes species new to Lithuania were identified and original descriptions of their morphology were provided. The influence of abiotic factors on the diversity of woody and herbaceous plants fungi was evaluated for the first time in Lithuania. The results of the study enhanced the knowledge about the distribution of Dothideomycetes and Sordariomycetes in the alluvial forests protected in Europe, which may be used to protect the biologic diversity of these habitats. The properties of the diversity and distribution of studied fungi in the pine forest affected by cormorants allow assessing the impact of the hypertrophication, caused by these birds on the pine forest mycobiota.

APA, Harvard, Vancouver, ISO, and other styles

47

Andrews, David Wayne. "The foraging ecology of double-crested cormorants in Toronto with perspectives on management /." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45922.

Full text

Abstract:

Thesis (M.Sc.)--York University, 2008. Graduate Programme in Biology.
Typescript. Includes bibliographical references (leaves 45-51). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR45922

APA, Harvard, Vancouver, ISO, and other styles

48

Tung, Calvin Yau Cheung. "Implementation of a dynamic wake distortion model for UTIAS Cormorant helicoptor model." 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=452789&T=F.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Yang, Gong-Heh, and 楊恭賀. "The Strategy Analysis of Kinmen Ecotourism Development－ A Case Study of Kinmen Cormorant Fair." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/rj4y53.

Full text

Abstract:

碩士
銘傳大學
公共事務學系碩士在職專班
94
The aim of this study is to propose the management strategies of Kinmen ecotourism based on the case study of Kinmen’s unique birds of passage, Cormorant. The strategies are divided into three stages, short, mid-term and long-term. The research materials not only include the author’s over ten years work experience in Kinmen National Park but also include fieldwork supported by ecotourism professionals, government authorities and the public. Based on the above information, SWOT analysis is applied to present the internal and external factors of Kinmen Cormorant Fair and SWOT Matrix is then utilized for the development of Management strategies. In conclusion, a blueprint plan is proposed as follows. 1、Short term goal and strategies：Integrate Kinmen local features including Kinmen National Park & Winter Cormorant Fair, military base developed culture, and historic monuments to popularize Kinmen ecotourism and culture identification. 2、Mid-term goal and strategies：Fulfill the preservation of Kinmen’s culture assets through restoration and maintenance of the historic interests. 3、Long term goal and strategies：Link up long-term developed community consensus and specialized culture assets to build up a city with ecotourism, great food and historic interests and to achieve the three-win situation among Kinmen residents, tourists and nature environment for sustainable management. Finally, this paper provides both the guidelines for the management of Kinmen ecotourism and the informative illustration when developing other ecotourism areas in Taiwan.

APA, Harvard, Vancouver, ISO, and other styles

50

Vieite, Beatriz da Silva Pereira Ribeiro. "Fishermen’s knowledge and conservation attitudes: focus on the great cormorant in the Minho River, Portugal." Master's thesis, 2021. http://hdl.handle.net/10773/31918.

Full text

Abstract:

Understanding the attitudes of traditional communities and their local ecological knowledge (LEK) can contribute to better policymaking and more fitting management plans. Thus, this study strived to share the Minho River’s fishermen LEK about great cormorant Phalacrocorax carbo (Linnaeus, 1758), as well as it reveals their conservation attitudes towards this species. We described and analysed interviewees’ LEK qualitatively, while their attitudes were analysed quantitatively through correlation with variables from fishermen’s profile. Fishermen were able to identify cormorant’s ecological characteristics like habitats, prey species, and foraging behaviour. They also showed an overall moderate attitude towards the conservation of great cormorants. The LEK often was supported by published data, but we found diverse information in some topics, such as habitat and diet. We found a significant negative correlation between fishermen’s age and attitudes (p = 0.02), and fishermen who often fished differed significantly from those who rarely fished (p = 0.02). We lastly reaffirm the importance of collecting more scientific data regarding P. carbo population structure in Portugal and the relevance of ethnobiological studies in decision-making.
Compreender as atitudes das comunidades tradicionais e o seu conhecimento ecológico local (CEL) pode contribuir para uma melhor formulação de políticas e planos de gestão mais adequados. Assim, neste estudo procurou-se partilhar o CEL dos pescadores do rio Minho sobre o corvo-marinho-de-faces-brancas Phalacrocorax carbo (Linnaeus, 1758), bem como revelar as suas atitudes conservacionistas em relação a esta espécie. Descrevemos e analisámos qualitativamente o CEL dos entrevistados, e, por outro lado, as suas atitudes foram analisadas quantitativamente através da correlação com variáveis do perfil dos pescadores. Os pescadores foram capazes de identificar as características ecológicas do corvo-marinho como habitats, espécies-presa, e comportamento de alimentação. Mostraram também uma atitude globalmente moderada em relação à conservação dos corvos-marinhos-de-faces-brancas. O CEL foi frequentemente apoiado por dados publicados, mas encontrámos diversas informações em alguns tópicos, tais como habitat e dieta alimentar. Encontrámos uma correlação negativa significativa entre a idade e as atitudes dos pescadores (p = 0,02), e os pescadores que pescavam frequentemente diferem significativamente dos que raramente pescavam (p = 0,02). Por último, reafirmamos a importância de recolher mais dados científicos sobre a estrutura da população de P. carbo em Portugal e a relevância dos estudos etnobiológicos na tomada de decisões.
Mestrado em Biologia Aplicada

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Cormorant'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles