Dissertations / Theses on the topic 'Clupeidae'

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The objective of this project was to evaluate the utilization of the sardine protein hidrolysate as a feeding stimulant for silver catfish. For this porpose, the following stimulants were evaluated: 1. Nile tilapia aqueous muscle extract; 2. Low degree of hidrolysis (DH) sardine waste protein hidrolyzate; 3. High DH sardine waste protein hidrolyzate; 4. Diluted (10% of concentration) high DH sardine waste protein hidrolyzate and 5. control by using only distilled water. Fish were individually evaluated. After 48 hours of fasting, the behavior was recorded on video for a basal period of 2 minutes, and for more 18 minutes after the substances inoculation. The experimental design was completely randomized with three treatments and twenty repetitions. The inoculation of high and low DH hidrolyzates increased the barbells moving time. The diluted high DH hidrolisate provide the same results of the low DH hidrolysate, but the average did not differed from destiled water (negative control) and the tilapia muscle extract. The fish locomotion increased in relation to the basal period, but did not differ between the treatments. On the other hand, the stimulants inoculation interfered in the number of times that the fish crossed the division line in the middle of the aquarium. The movement increase in the fish movement to one side to 12 another of the aquarium was higher with high and low DH hidrolysates. From this result, it is possible to conclude that the sardine waste protein hidrolysate protein was efficient to stimulate the feeding associated behavior in juvenile jundiá
O objetivo deste projeto foi avaliar a utilização do hidrolisado proteico de sardinha como atrativo na alimentação do jundiá. Para isto os seguintes atrativos alimentares foram avaliados: 1. extrato aquoso de músculo de tilápia do Nilo; 2. hidrolisado proteico de sardinha com baixo grau de hidrolise (GH); 3. hidrolisado proteico de sardinha com alto GH; 4. hidrolisado proteico de sardinha com alto GH diluído (10% da concentração) e 5. controle usando somente água destilada. Os peixes foram avaliados individualmente. Após jejum de 48 horas o comportamento foi registrado em vídeo por um período basal de 2 minutos, e por mais 18 minutos após a inoculação do atrativo. O delineamento foi inteiramente casualizado com três tratamentos e vinte repetições. A inoculação dos hidrolisados com alto e baixo GH aumentou o tempo de movimentação dos barbilhões. O hidrolisado com alto GH diluído proporcionou os mesmos resultados que o hidrolisado com baixo GH , mas as médias não diferiram das obtidas para a água destilada (controle negativo) e do extrato de músculo. A locomoção dos peixes aumentou em relação ao período basal, mas não diferiu entre os tratamentos. Por outro lado a aplicação dos atrativos interferiu no número de vezes que os peixes cruzaram a linha divisória do meio do aquário. O incremento na movimentação 10 de um lado para outro do aquário foi maior (P<0,05) para os hidrolisados com alto e baixo GH. A partir deste resultado é possível concluir que o hidrolisado proteico foi eficiente para estimular o comportamento associado à alimentação em juvenis de jundiá

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The objective of this study was to evaluate the use of soluble and insoluble fractions of protein hydrolysates of different waste sardines (Clupeidae), on the performance of juvenile catfish. We tested two types of muscle hydrolyzate, soluble fraction and insoluble assessed individually (WSF and FIM) and combined with each other (WSF + END), and two types of viscera hydrolyzed soluble fraction of natural guts and industrialized (FSVN FSVI E) . The experimental design was completely randomized with five treatments (type hydrolyzate) and five repetitions. The juveniles are kept in tanks of 30 liters with densidadel 8 fish per tank, to which were cultured for 56 days. The results were analyzed using parametric variance analysis (ANOVA) and subjected to the Duncan test (5% significance). The final best results, weight gain, feed conversion and protein efficiency ratio were obtained with the diet containing a combination of soluble and insoluble fractions of the hydrolyzate muscle, and the diet containing the soluble fraction of the hydrolyzate of industrial offal. A diet containing hydrolyzed soluble industrial viscera was also the most consumed by the animals. A diet containing hydrolyzed insoluble muscle was the one that gave the worst results consumption. The worst feed conversion was obtained for the diet containing the soluble hydrolyzed muscle. Survival, body composition and ammonia excretion did not differ between treatments. The best performance results are obtained using crude hydrolysates which combine the benefits of both fractions. The degree of hydrolysis has a direct effect on feed intake. Furthermore, it was shown that soluble hydrolysates can be used at high levels of inclusion, from which nutrients are adequately balanced diets
O objetivo deste trabalho foi avaliar a utilização das frações solúveis e insolúveis de hidrolisados proteicos de diferentes resíduos de sardinha (Sardinella sp.), sobre o desempenho de juvenis de jundiá. Foram testados dois tipos de hidrolisado de músculo, fração solúvel e insolúvel avaliadas individualmente (FSM e FIM) e combinadas entre si (FSM+FIM), e dois tipos de hidrolisado de vísceras, fração solúvel de vísceras natural e industrializada (FSVN E FSVI). O delineamento experimental foi inteiramente casualizado com cinco tratamentos (tipos de hidrolisado) e cinco repetições. Os juvenis foram mantidos em aquários de 30 litros, com densidade de 8 peixes por aquário, ao qual foram cultivados por 56 dias. Os resultados foram analisados por meio de Análise de Variância Paramétrica (ANOVA), e submetidos ao teste de Duncan (5% de significância). Os melhores resultados de peso final, ganho de peso, conversão alimentar e taxa de eficiência proteica foram obtidas com a dieta contendo a combinação das frações solúveis e insolúveis do hidrolisado de músculo, e com a dieta contendo a fração solúvel do hidrolisado de vísceras industrial. A dieta contendo hidrolisado solúvel de vísceras industrial também foi a mais consumida pelos animais. A dieta contendo o hidrolisado insolúvel de músculo foi a que proporcionou os piores resultados de consumo. A pior conversão alimentar foi obtida para a dieta contendo o hidrolisado solúvel de músculo. A sobrevivência, a composição corporal e a excreção de amônia não diferiram entre os tratamentos. Os melhores resultados de desempenho são obtidos com hidrolisados brutos que combinam os benefícios das duas frações. O grau de hidrólise tem efeito direto sobre o consumo de ração. Além disso, foi demonstrado que os hidrolisados solúveis podem ser utilizados em níveis elevados de inclusão, desde que os nutrientes das dietas sejam adequadamente balanceados

Suite a une presentation de la region de trinidad (bolivie), plus particulierement des milieux aquatiques et des caracteristiques physico-chimiques des eaux, l'aspect piscicole est aborde grace aux donnees des peches commerciales mais surtout a l'aide de nos peches experimentales. Notre contribution a la connaissance de la faune ichtyologique du bassin du mamore est essentiellement basee sur l'etude de pellona castelnaeana. En parallele, nous avons analyse partiellement la biologie d'un autre clupeidae: pellona flavipinnis. Apres une etude des caracteres systematiques, la biologie des deux clupeidae est abordee par leur repartition spatio-temporelle et les peuplements piscicoles associes. L'etude de la reproduction a permis de definir les modalites, le lieu et l'epoque de la ponte, mais aussi de mettre en evidence l'existence d'un hermaphrodisme protandre. Le role de predateur ichtyophage exclusif a ete confirme. La croissance, abordee par l'otolithometrie et confirmee par la methode de pauly et david, fait ressortir l'existence d'une croissance differente suivant le sexe et un arret de croissance lie a la reproduction. L'ensemble des resultats obtenus, ce qui est connu du milieu et des autres especes, ainsi qu'un essai de prediction de la production potentielle de p. Castelnaeana sont utilises pour proposer des amenagements qui permettraient de mieux exploiter et gerer la grande richesse piscicole de la region de trinidad

Phylogeographic patterns of coastal organisms with different life histories and breeding strategies may reveal patterns not consistent with the current delineation of the biogeographic provinces around South Africa. The subdivision of the South African coastline into these three main climatological or biogeographic regions: namely the cool temperate west coast, the warm temperate south coast and the subtropical east coast, is based on average seawater temperatures and hydrological conditions. Genealogies of two estuarine fish species Atherina breviceps, a marine breeder, and Gilchristella aestuaria, an estuarine spawner, were reconstructed using mitochondrial DNA (mtDNA) control region sequences. The study comprised two components, an assessment of a small dataset of both fish species to compare their population structure along the South African coastline and a more comprehensive investigation of the phylogeography of G. aestuaria collected from 21 estuaries around the coast. The comparative study of A. breviceps and G. aestuaria indicate different population distribution patterns along the South African coastline. Results of the A. breviceps analysis demonstrate substantial gene flow due to the random mixing of alleles, while the comparative G. aestuaria dataset indicates a more structured population and considerably less gene flow. The G. aestuaria population demonstrates geographic separation into four groups, namely the west coast (Great Berg), Bot (south coast), Seekoei (south coast) and east coast (Bushmans, Kasouga and Cefane). Results from the larger G. aestuaria dataset indicate that the phylogeographic patterns observed during this study do not conform to existing biogeographic boundaries along the southern African coastline. The delineation identified during this study between the warm temperate and subtropical regions is further south than originally perceived and this southward extension can be ascribed to the prevailing hydrology. The life history patterns and ecology of these two estuarine fish species appears key to understanding their population structure. These factors interact with environmental characteristics such as physical oceanography and the distribution of estuaries (along the coastline) to explain the observed distribution patterns and population structure of A. breviceps and G. aestuaria.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2011.
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Os padrões associados às condições ambientais e a distribuição espaço-temporal dos estágios iniciais da savelha, B. pectinata, e de seu desenvolvimento no estuário da Lagoa dos Patos foram investigados através de dados históricos. Dois outros experimentos complementares foram realizados: um para avaliar as técnicas de medição (tradicional e por imagem) em larvas de peixes; e, outro, para investigar o efeito dos principais conservantes (álcool 70 % e formaldeído 3,6%) sobre as larvas de savelha. Diferença significativa na medição de larvas de peixes entre ambas as técnicas não foi observada, e os coeficientes de variação foram similares, o que sugere que as técnicas produzem o mesmo resultado médio, apesar do ganho de precisão pela técnica de análise por imagem. Um encolhimento significativo foi observado para ambos os conservantes, e os fatores de correção para as larvas de B. pectinata em formaldeído foi CP vivo = 1,0799 × CP pós-conservação, e em álcool foi CP vivo = 1,1415×CP pós-conservação. No período de 1975 a 2009, um total de 10479 ovos e 14066 larvas e juvenis foram coletados através de amostragens planctônicas, e também amostrados parâmetros da água (salinidade e temperatura). As larvas foram medidas e classificadas de acordo com seu estágio de desenvolvimento. Cada estágio de desenvolvimento foi caracterizado pelo seu intervalo de tamanho, onde a menor larva em estágio vitelínico mediu 2,16 mm, e o maior juvenil teve 43,25 mm. As análises dos padrões de distribuição indicam desova fora da Lagoa dos Patos, em salinidade mais elevada, sendo importantes períodos sazonais para os ovos o inverno, primavera e início de verão, e posteriormente ocorre um transporte para dentro da região estuarina nos estágios mais iniciais de desenvolvimento, associados a valores menores de salinidade e temperatura. A distribuição dos juvenis indicou um retorno para a região costeira, e neste estágio o outono foi um período muito importante. Estes resultados são importantes para o conhecimento desta espécie, e serão úteis para o planejamento no gerenciamento deste recurso.
Patterns associated to environmental conditions and to the spatial and temporal distributions of the early stages of Argentine menhaden, B. pectinata, and of its development in the Patos Lagoon estuary were investigated using historical records. Two other complementary experiments were performed: one to evaluate the measurement techniques (traditional and image) in larval fishes; and, other, to investigate the effect of main conservatives (alcohol 70 % and formaldehyde 3.6 %) over Argentine menhaden larvae. Significant difference in the measurement of fish larvae between techniques was not observed, and the coefficients of variation were similar, suggesting that these two techniques produce the same average result, despite the gain in precision by image analysis technique. A significant shrinkage was observed for both preservatives, and the correction factors for B. pectinata larvae in formaldehyde was SL live= 1.0799 × SL post-conservation, and in alcohol was SL live= 1.1415 × SL post-conservation. From 1975 to 2009 a total of 10479 eggs and 14066 fish larvae and juveniles were collected at plankton surveys, and sampled water parameters (salinity and temperature), too. Larvae were measured and classified according to their developmental stage. Each development stage was characterized by its size range, which the smallest yolk-sac larvae measured 2.16 mm, and the largest juveniles had 43.25 mm. Analysis of the distributional pattern indicate spawning outside the Patos Lagoon, in high salinities, being important seasonal period for the eggs the winter, spring and early summer, and after occur a transport to the inner estuarine region in the earlier developmental stages, associated to lesser temperature and salinity values. Distribution of juveniles indicated a return to the coastal region, and in this stage the autumn was a very important period. These results are important for knowledge this specie, and will be useful for planning the management of this resource.

Deux mille specimens ont ete examinés. Les résultats obtenus ont permis d'introduire la synonymie entre odaxothrissa et cynothrissa d'une part et entre microthrissa et poecilothrissa d'autre part. Le genre pellonula est confirmé et comprend deux espèces valides. Des synonymies sont établies. Au sein du genre microthrissa deux sous-genres ont été reconnus. Le nombre des genres valides des clupeidae dulcaquicole de l'ouest et du centre du continent africain a été réduit a dix. Une nouvelle clé générique a été établie ainsi qu'un cladogramme hypothétique représentant leur phylogénie

This investigation examined the adequacy of the forage base to meet current demand of piscivores in Smith Mountain Lake, Virginia. Surplus production, or the maximum sustainable supply, of alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) were determined using data on the biomass, growth, and mortality of each species. Mean hydroacoustic alewife biomass from 1993-1998 was 37 kg/ha and mean gizzard shad cove rotenone biomass from 1990-1997 was 112 kg/ha. Mean annual alewife surplus production was determined to be 73 kg/ha and mean annual gizzard shad surplus production totaled 146 kg/ha.

Bioenergetics modeling and population density estimates were utilized to derive the annual food consumption (realized demand) of the two most popular sport fish in the system, striped bass (Morone saxatilis) and largemouth bass (Micropterus salmoides). The striped bass population consumed 46 kg/ha of alewife and 27 kg/ha of gizzard shad annually. Largemouth bass ate 9 kg/ha of alewife and 15 kg/ha of gizzard shad annually. Annual consumption by ancillary predators was estimated to be 13 kg/ha of alewife and 35 kg/ha of gizzard shad.

Prey supply to predators is limited by morphology, behavior, and distribution. The cumulative effect on prey availability of these three factors, in addition to consumption by other predators, was quantified. For largemouth bass, available supply of alewife and gizzard shad exceeded demand by 20% and 53% respectively. For striped bass, available supply of gizzard shad surpassed demand by 30% but available alewife supply was only 4% greater than demand. Annual demand of all predators was 94% of total available clupeid supply.

Striped bass stockings were increased by 50% in 1998 and will remain at this level in the near future. A predator-prey simulation model of alewife and striped bass populations was developed to explore the consequences of increased predator demand. This model incorporated dependencies between alewife abundance and mortality and the mortality, abundance, and growth of striped bass. Model output showed that a 50% stocking increase has a near-zero probability of increasing the mean annual number of legal and citation striped bass in Smith Mountain Lake.
Ph. D.

Tidal freshwater wetlands provide valuable ecosystem services such as nutrient cycling, coastal flood control, and reproductive habitat for early life stages of economically and ecologically important fishes. The nutrient rich environments that tidal freshwater wetlands occur in support high levels of primary productivity of phytoplankton and vegetation that provide essential reproductive habitat for anadromous clupeid fishes (Alosa spp., Brevoortia tyrannus) in Chesapeake Bay tributaries. Seasonal retention of clupeid eggs and larvae within tidal freshwater habitats may enhance early growth, survival, and year class strength. The primary goal of the present study was to characterize the relative importance of tidal freshwater wetlands to the early life history stages of anadromous, migratory, and resident clupeid fishes in the lower James River. From 2014-2018, conical tow nets were used to collect ichthyoplankton samples from representative locations within the tidal freshwater marsh-creek complex of Curles Neck Creek, Virginia during the period of February through May. Boat electrofishing was used to sample juvenile target clupeids within the marsh-creek complex during March through November 2014-2018. A strong positive correlation between larval and juvenile Blueback Herring and Atlantic Menhaden, supported the hypothesis of seasonal in-system retention. This was the first published study to describe spatial and temporal patterns of occurrence of clupeid fishes with varying life history strategies in a tidal freshwater marsh and highlighted the importance of tidal freshwater marshes as nursery habitat.

Les paramètres de croissance de poissons pélagiques et démersaux ont été étudiés durant la période de 1990 à 2015 dans le but d’examiner l’impact de facteurs biotiques comme la densité-dépendance, le recrutement, la mortalité totale et de facteurs abiotiques tels que l’intensité d’upwelling, la température et la concentration en chlorophylle a. Les paramètres d’histoire de vie des espèces peuvent varier selon les espèces, d’une région à l’autre, et dans le temps au sein d’une même région en raison de leur plasticité et de la pression de la pêche. Une comparaison inter-espèces et inter-régions a été réalisée. Le modèle non linéaire à effets mixtes a été utilisé pour différentes populations de l’Océan Atlantique afin d’établir les paramètres de croissance aux niveaux individuel et de la population. Les variations des paramètres de croissance d’une sélection d’espèces ont été mises en corrélation avec des facteurs biotiques et abiotiquesLes espèces (Sardinella aurita, sardinelle ronde, Atherinella brasiliensis, tinicalo, Merlangius merlangus, merlan, Melanogrammus aeglefinus, églefin et Solea solea, sole) montrent des réponses différentes aux facteurs biotiques et abiotiques. Au niveau spatial pour le merlan et l’églefin, la croissance est affectée par la latitude et la température, tandis qu’au niveau temporel la croissance du merlan est affectée par la température et la densité. Il y avait un intérêt pour savoir si les variables morphométriques et le diamètre de l’otolithe de tinicalo étaient de bons indicateurs de la croissance : c’est la longueur standard qui a présenté
The impact of biotic factors such as density-dependent processes, recruitment, total mortality, and abiotic factors such as upwelling intensity, temperature and chlorophyll a concentration on the variation of growth parameters of pelagic and demersal fish were studied during the periods 1990 - 2008 (pelagic) and 1971 - 2015 (demersal). Life history parameters vary according to the species and from one region to another and over time within a given area because of their plasticity and the high fishing pressure. Interspecies and inter-regional comparison were carried out. Non-linear mixed effects models were used on different fish species of the Atlantic Ocean in order to estimate the growth parameters at the individual and population levels. Variations in growth parameters of selected species were correlated with biotic and abiotic factors.Selected species (Sardinella aurita, round sardinella, Xenomelaniris brasiliensis, tinicalo, Merlangus merlangus, whiting, Melanogrammus aeglefinus, haddock and Solea solea, sole) showed different responses to biotic and abiotic factors. Regardind the spatial component for whiting and haddock, the variation of growth parameters was affected by latitude and temperature. Concerning the temporal component, whiting was affected by temperature and density-dependent processes. There was also an interest to know if the morphometric variables and the diameter of the otolith of Atherinella brasilensis were good growth indicators. Among the morphometric parameters examined, the standard length-Age relationship showed the best fit (r2 = 0.90), foll

The abundance and distribution of small pelagic fish in coastal upwelling systems fluctuate in response to environmental or biotic factors acting on larval stages. Anchovies (Engraulis spp.) have evolved flexible adaptive strategies to maximise recruitment in such environments. Spawning usually occurs throughout coastal and shelf regions, however the relative importance of inshore/offshore waters for spawning and the survival of eggs and larvae is poorly understood. The objectives of this study were to 1-identify the locations, and season, of anchovy (Engraulis australis) spawning in South Australia; 2-determine the oceanographic and biotic characteristics (e.g sea-surface temperature and chlorophyll a levels,) of gulf and shelf waters during the spawning season of this species, and 3-determine the relative importance of gulf and shelf waters for anchovy spawning and larval recruitment. Ichthyoplankton and oceanographic surveys encompassing a total of 128,700 km² were conducted and anchovies were captured at locations throughout this area. Anchovy eggs were found throughout gulf and shelf waters, with highest densities recorded in northern areas of Spencer Gulf and Gulf St Vincent where sea surface temperatures (SST) were 24–26°C. Spawning appeared to peak between 0000 and 0100 hours. Otolith increment counts were used to age larval, juvenile and adult anchovies from both shelf and gulf waters. In the northern Spencer Gulf only smaller, young fish up to 1 year of age occurred, where there were eggs and young larvae (< 10mm) at high density. These anchovies spawned relatively small batches of eggs (c. 855 per fish) approximately every 3 days over an area of approximately 4,898 km². The daily egg production method (DEPM), used to estimate an adult biomass for the northern Spencer Gulf gave an estimate of 25,374 tonnes. The southern gulf area was inhabited by 1, 2 and 3 year old fish, whereas over the continental shelf, where upwelling occurs, 3, 4, and 5 year old fish were found. In these cooler, deeper, shelf waters, where the larger, older, anchovies are found, lower egg densities occurred despite individuals producing much larger batches of eggs (ca. 15,572 per fish) approximately every 7 days. In shelf waters, the highest egg densities were recorded at inshore sampling stations. Spawning by older fish took place over a far greater area of ca. 44,618 km² with an estimated adult biomass of 101,522 tonnes. Unlike in the gulf waters, larvae > 10 mm total length (TL) were mainly found with the largest larvae, > 15 mm TL, being collected from shelf waters near up-welling zones where SSTs were relatively low (< 20°C) and levels of chlorophyll a (chl a) relatively high. The high levels of larval abundance in the upwelling zones may reflect higher levels of recruitment to later stages in these areas compared with the gulfs. Gonosomatic indices, together with egg and larval densities, indicated that the peak spawning season was from January to March. This coincided with the enhanced period of productivity in shelf waters due to up-welling events. However, these highly variable environments can be highly dispersive with resulting high egg and larval mortalities and are generally dominated by sardines (Sardinops spp.). In addition to the shelf population young fish are also present in the relatively stable gulf environment. This population may act as a reserve of anchovy in South Australia from which the population may expand under favourable conditions. When the population of dominant sardines (S. sagax) are reduced, it appears that the subordinate anchovies, represented by older age-classes, are able to utilise offshore environments which may then provide additional spawning and nursery areas for this species.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2011

 Fishways designed for salmonids in temperate rivers have often been successful, but similar fishways provided for non-salmonid species in tropical and sub- tropical rivers have frequently failed. In 1970 a salmonid style fishway was built on a tidal barrage on the sub -tropical Fitzroy River, in Queensland, north-eastern Australia. Despite modifications to the design in 1987 assessment of the fishway in 1978 and 1992 demonstrated that it was ineffective; particularly as few barramundi (Lates calcarifer [Centropomidae]) were found at the top of the fishway. The inadequacy of the design appeared to be related to very high water velocities and turbulence within the fishway pools. Consequently, since construction of the tidal barrage many catadromous fish populations (species that live in freshwater but breed in saltwater) have declined in the freshwater reaches of the Fitzroy River. 

In 1994 the fishway was modified to a vertical -slot design. The study reported in this thesis is an assessment of the effectiveness of the new design from 1995 to 1997. In 38 paired samples taken at the top and bottom of the fishway, over 16 months, 29 fish species and over 23,000 fish were collected at a maximum rate of 3,400 per day. At the top of the fishway 15,471 individuals were collected and 7594 at the bottom. The migratory population consisted of 4 marine species, 9 diadtomous species and 16 potamodromous species. Common species using the fishway included blue -catfish (Arius graeffei [Ariidae]), bony herring (Nematalosa erebi [Clupeidae]), striped mullet (Mugil cephalus [Mugilidae]), barramundi, and long -finned eels (Anguilla reinhardtii [Anguillidae]). Shrimp  Macrobrachium australiense [Palaemonidae]), juvenile crabs (Varuna litterata [Grapsidae]) and long -finned elvers did not ascend the full length of the fishway and specific fishways for these species are recommended. Fish between 25 and 640 mm in length ascended the fishway, although the passage of smaller size classes of immature fish was restricted which may be important for the sustainability of these migratory populations. The bulk of the biomass (71% at the top and 66% at the bottom) was made up of the diadromous blue -catfish of which 81 % were immature. Furthermore, a number of other common fish species were represented mostly by juveniles, including striped mullet, bony herring and barramundi. 

This study is the first record of barramundi successfully migrating through an in situ fishway in that no significant difference was found between the size of fish at the top and bottom. A major finding was that 95% of the barramundi from the fishway were immature fish (200-640 mm long), but significantly larger barramundi (maximum length 980 mm) were captured by angling near the base of the fishway. Nevertheless, enlargement of vertical -slot width from 0.15 m to 0.45 m only encouraged a small number of larger fish (890 mm maximum length) to enter. Interestingly, very small barramundi (45-163 mm long) were also absent from the fishway, but these were found in a small tidal tributary below the barrage. Very young barramundi appear to inhabit specific off - channel habitat before migrating in the main river at a larger size. The implications of these results are that 150 mm slot widths are suitable for barramundi and that different life stages have different migratory requirements.   

Species long-term persistence is to a great extent contingent on the ability of populations to mount variable responses to perturbations; the breadths of which are largely dependent on the amount of heritable variation present at the population level. However, populations are not necessarily equivalent in their amount of genetic variation, or in their responses to future environmental conditions, and information about the magnitude and spatial distribution of intraspecific genetic variation is integral to conservation planning, and preserving species evolutionary potential. Using neutral molecular markers, I demonstrate that latitude is an important determinant of the amount and spatial distribution of genetic variation within and among Nearctic fishes. Latitudinal declines observed among species were mirrored by declines within species, and encourage a cautionary approach for interspecific comparisons and inferences of broad spatial patterns of genetic variation when data for individual species are obtained from only a portion of their range. I subsequently examined the magnitude and spatial distribution of microsatellite based variation for 33 spawning runs from across the range of American shad (Alosa sapidissima). Sequential reductions of intraspecific genetic variation with latitude were observed among spawning runs from formerly glaciated regions; consistent with stepwise post-glacial range expansion, and successive population founder events. Canadian populations exhibited temporally stable genetic differentiation characterized by a significant pattern of isolation by distance, and exhibited evidence of metapopulation structure. Although isolation by distance was observed among U.S. spawning runs, population structure was comparatively weak; a possible consequence of increased levels of gene flow (human-mediated or natural). Different spatial patterns of population structure were detected across the species’ range, but are not likely due to alternative reproductive strategies (iteroparity vs. semelparity). Rather, these different patterns probably reflect different management strategies in Canada (no stocking) and the United States (stocking), alternative glacial histories, or combinations thereof. Reciprocal patterns of genetic diversity and differentiation observed across the species’ range suggests that U.S spawning runs contribute more to diversity and less to differentiation than Canadian spawning runs. These results have implications for future shad restoration efforts, and the long-term persistence of the species.