Relevant bibliographies by topics / Trawling

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers
  6. Reports

Academic literature on the topic 'Trawling'

Author: Grafiati
Published: 4 June 2021
Last updated: 15 June 2025

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Journal articles on the topic "Trawling"

1

Jones, Peter. "The spread of bottom trawling in the British Isles, c.1700–1860." International Journal of Maritime History 30, no. 4 (2018): 681–700. http://dx.doi.org/10.1177/0843871418804486.

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Widespread bottom trawling in British waters has traditionally been dated from the last decades of the 18th century, and its early heartland has most commonly been identified as the Torbay area of Devon. This article shows that, in fact, by the time Torbay became known as a centre for the industry, bottom trawling was already well-known and relatively widespread around much of England and Wales, as well as large parts of Eastern and Southern Ireland. Following on from an earlier contribution in this journal, it also demonstrates that bottom trawling’s unbroken history, going back to at least the first decades of the 17th century, has always been beset by controversy, but that the middle decades of the 19th century saw a sea-change in official attitudes that, in effect, ushered in an era of unfettered expansion in industrial beam trawling by the 1890s.
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Bergman, Magda J. N., and Erik H. Meesters. "First indications for reduced mortality of non-target invertebrate benthic megafauna after pulse beam trawling." ICES Journal of Marine Science 77, no. 2 (2020): 846–57. http://dx.doi.org/10.1093/icesjms/fsz250.

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Abstract Two alternative stimulation techniques to reduce mortality in benthic megafauna were tested relative to standard tickler chain beam trawling: longitudinal electrodes (pulse trawl) and longitudinal chains. Longitudinal chains caused higher mortality than pulse trawling in 3 species. Standard trawling gave higher mortality in Echinocardium cordatum than pulse trawling. Between longitudinal chain and standard trawling were no significant differences. This trend in decreasing mortality from longitudinal, to standard and then pulse trawling was confirmed by a similar decline in: i) numbers of significant species mortalities per trawl type, ii) average mortalities, i.e. longitudinal chain caused 41% more mortality than standard trawling and pulse trawling 43% less, iii) pre- and post-trawling community dissimilarities. A significant majority of species showed higher mortalities after longitudinal than after standard trawling and, conversely, lower mortalities after pulse trawling. Trawls with longitudinal chains instead of cross tickler chains increase megafaunal impact. On the contrary, pulse trawling can reduce the impact, although average mortality remains substantial (25%) even in impoverished benthic test assemblages in the southern North Sea. Power, generally was low and reference areas, free of (pulse) trawling, and inhabited by more vulnerable taxa will facilitate higher powered studies on the impact of standard and alternative trawling techniques.
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Rijnsdorp, A. D., J. G. Hiddink, P. D. van Denderen, et al. "Different bottom trawl fisheries have a differential impact on the status of the North Sea seafloor habitats." ICES Journal of Marine Science 77, no. 5 (2020): 1772–86. http://dx.doi.org/10.1093/icesjms/fsaa050.

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Abstract Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.
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Hinz, Hilmar, Jan G. Hiddink, James Forde, and Michel J. Kaiser. "Large-scale responses of nematode communities to chronic otter-trawl disturbance." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 4 (2008): 723–32. http://dx.doi.org/10.1139/f08-002.

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Nematodes, because of their small size and short life cycles, are thought to be less affected by direct trawling mortality compared with the larger macrofauna. However, nematodes may still be indirectly affected by the physical disturbance of trawling through changing sediment characteristics and food web structure. We determined whether nematode communities on two muddy fishing grounds located in the North Sea and Irish Sea were affected by chronic otter-trawl disturbance and quantified these effects. Nematode abundance, production, and genus richness declined in response to trawling within both areas. Nematode biomass did not respond to trawling intensity. Genus composition was affected by trawling only in the North Sea. The responses in abundance of individual nematode genera to increasing trawling intensity were negative as well as positive. These results indicate that despite their size and fast life cycle, nematodes are affected by intensive trawling on muddy fishing grounds. The loss in secondary production from nematodes can have far-reaching consequences for the integrity of the benthic food web. As bottom trawl fisheries are expanding into ever deeper muddy habitats, the results presented here are an important step towards understanding the global ecosystem effects of bottom trawling.
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Mills, Craig M., Sunny E. Townsend, Simon Jennings, Paul D. Eastwood, and Carla A. Houghton. "Estimating high resolution trawl fishing effort from satellite-based vessel monitoring system data." ICES Journal of Marine Science 64, no. 2 (2006): 248–55. http://dx.doi.org/10.1093/icesjms/fsl026.

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Abstract Mills, C. M., Townsend, S. E., Jennings, S., Eastwood, P. D., and Houghton, C. A. 2007. Estimating high resolution trawl fishing effort from satellite-based vessel monitoring system data. – ICES Journal of Marine Science, 64: 248–255. High resolution estimates of trawling effort are needed to underpin studies of trawling impacts on species, habitats, and ecosystem processes, and to monitor responses to area closure and other management actions. Satellite-based vessel monitoring systems (VMS) were designed for fishery control and enforcement, but they provide potentially valuable source information on spatial and temporal patterns of trawling activity at multiple scales. Based on an analysis of VMS data for UK beam trawlers in the North Sea, a method is described for identifying trawling activity and estimating fishing intensity based on the minimum and maximum potential spatial extent of trawling effort from VMS data. The optimal method for identifying trawling and steaming behaviour combined speed and directionality rules and correctly identified trawling and steaming in 99% and 95% of cases, respectively. Using speed- and directionality-filtered VMS data, trawling effort can be reported as area impacted per unit time per unit area at a range of grid scales from 1 km to 100 km (10 000 km2). Trawling effort is accurately represented at a grid cell resolution of 3 km or less.
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Matriadi, Faisal, Marbawi Marbawi, Chalirafi Chalirafi, and Mariyudi Mariyudi. "EFFECTIVE FISHERIES MANAGEMENT: TO REDUCE ENVIRONMENTAL DAMAGE AND SOCIAL CONFLICTS OF FISHERMEN DUE TO THE USE OF TRAWLING." International Journal of Economic, Business, Accounting, Agriculture Management and Sharia Administration (IJEBAS) 1, no. 2 (2021): 277–94. http://dx.doi.org/10.54443/ijebas.v1i2.80.

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The use of trawling as a fishing tool has long been known to have a very bad impact on the environment and creates social conflict in fishing communities. Likewise, on the North-East coast of Aceh there are still fishermen who use trawlers as fishing gear. On the other hand, the use of trawling is very damaging to the environment and causes social conflicts for fishermen. The cessation of trawling operations also has an economic and social impact on fishermen who have been using trawling for their livelihood. This study tries to explore how the impact of environmental damage and social impacts or fishing conflicts that occur due to the use of trawling and how the social and economic impacts if trawling operations are stopped on the North-East coast of Aceh. The research method was carried out with an exploratory descriptive qualitative approach. The results showed that there was significant environmental damage in the research area, namely in the waters of Lhokseumawe, North Aceh, East Aceh and Langsa. This is marked by the destruction of coral reefs and the reduced population of various types of fish, some of which are even very rare. The use of trawling also has an impact on social conflicts among fishermen which often occur. Meanwhile, the prohibition of trawling also has an impact on the loss of income for trawler fishermen and those who depend on trawling operations for their livelihoods. This study recommends stopping trawling permanently to preserve the aquatic environment and avoid social conflicts with fishing communities. Furthermore, to save trawler fishermen, the government must try to convert trawler fishing gear to fishing gear that is more economical and environmentally friendly.
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Kenchington, E. LR, J. Prena, K. D. Gilkinson, et al. "Effects of experimental otter trawling on the macrofauna of a sandy bottom ecosystem on the Grand Banks of Newfoundland." Canadian Journal of Fisheries and Aquatic Sciences 58, no. 6 (2001): 1043–57. http://dx.doi.org/10.1139/f01-053.

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A 3-year otter trawling experiment was conducted on a deepwater (120–146 m) sandy bottom ecosystem on the Grand Banks of Newfoundland that had not experienced trawling for at least 12 years. The benthic macrofauna were sampled before and after trawling and in reference areas. The 200 grab samples collected contained 246 taxa, primarily polychaetes, crustaceans, echinoderms, and molluscs. Biomass was dominated by propeller clams (Cyrtodaria siliqua) and sand dollars (Echinarachnius parma), while abundance was dominated by the polychaete Prionospio steenstrupi and the mollusc Macoma calcarea. The most prominent feature of the data was a natural decline in the total number of species, the total abundance, and the abundance and biomass of selected species between 1993 and 1995. The only immediate effect of trawling was seen in 1994 when the abundance of 13 species, the biomass of 11 species (mostly polychaetes), and the total abundance per grab were significantly lower. There was little evidence of long-term trawling effects. When trawling disturbance was indicated, it appeared to mimic natural disturbance, shifting the community in the same direction in multidimensional scaling ordination; no distinctive trawling signature was observed. However, the results of this experiment should not be uncritically extrapolated to the impacts of commercial trawling.
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Tanner, Jason E. "The influence of prawn trawling on sessile benthic assemblages in Gulf St. Vincent, South Australia." Canadian Journal of Fisheries and Aquatic Sciences 60, no. 5 (2003): 517–26. http://dx.doi.org/10.1139/f03-044.

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Most experimental studies on the effects of trawling on the benthos use remote sampling techniques and are conducted in recently trawled areas. Thus it is difficult to determine the effects of trawling on previously unfished areas, and the fates of individual animals cannot be followed. In this study, I follow the fates of individuals of several sessile taxa when exposed to experimental trawling in areas that have not been trawled for some 15–20 years. Although there was a significant trawling by location effect for all multivariate analyses and most individual taxa, I found that trawling had an overall negative effect on the benthos. Epifauna at trawled sites decreased in abundance by 28% within 2 weeks of trawling and by another 8% in the following 2–3 months (compared with control sites). Seasonal seagrasses were also less likely to colonise trawled sites than untrawled sites. The persistence of most taxa declined significantly in trawled areas compared with untrawled areas. In contrast to this, the recruitment rates of several taxa into visible size classes increased after trawling, presumably because of a reduction in competition.
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van Denderen, P. Daniël, Niels T. Hintzen, Tobias van Kooten, and Adriaan D. Rijnsdorp. "Temporal aggregation of bottom trawling and its implication for the impact on the benthic ecosystem." ICES Journal of Marine Science 72, no. 3 (2014): 952–61. http://dx.doi.org/10.1093/icesjms/fsu183.

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Abstract Understanding trawling impacts on the benthic ecosystem depends to a large extent on the ability to estimate trawling activity at the appropriate scale. Several studies have assessed trawling at fine spatial scales yearly, largely ignoring temporal patterns. In this study, we analysed these temporal patterns in beam trawl effort intensity at 90 stations of the Dutch continental shelf of the North Sea for a period of 10 years, at a fine temporal (weekly) and spatial (110 × 70 m) scale using Vessel Monitoring by Satellite (VMS) data. Our results show that trawling is aggregated in time and shows clear seasonality, related to the behavior of the fleet and migration patterns of the target fish species. The temporal patterns affect the overall impact on and the recovery of the benthic community, as is illustrated with a benthic population model. Our results imply that trawling impact studies using high-resolution data like VMS should take account of the possibility of temporal aggregation and seasonality in trawling to improve the assessment of the impact of trawling on the population dynamics of benthos.
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Hanna, Jack, Seán Power, Phil O'Keeffe, and Mary Ryan. "Trawling the Past." Books Ireland, no. 194 (1996): 93. http://dx.doi.org/10.2307/20623248.

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Dissertations / Theses on the topic "Trawling"

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Udoff, Geoffrey. "An Alternate Trawling Method: Reduced Bycatch and Benthic Disturbance Achieved with the Wing Trawling System." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2217.

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The Wing Trawling System (WTS) was tested as an alternative to traditional shrimp capture methods in the Gulf. Compared to an otter trawl, this trawl was conceived to reduce bycatch, retain shrimp catch, and minimize seafloor disturbance. Through seventy-one paired tows, the WTS was assessed against a standard otter trawl. The WTS was found to reduce bycatch by 63-65% and reduce shrimp catch by 30-35%. Additionally, I measured the depth of the scars produced by both trawls and quantified the turbidity of the plumes behind them. The scars left by the WTS and the otter trawl were between 9.9 cm-13.6 cm. The turbidity behind the WTS was 18.6 NTU, while the turbidity behind the otter trawl was 206.8 NTU. In conclusion, the WTS offers an alternative to an otter trawl that reduces bycatch and the impact trawling has on the seafloor but results in a significant amount of shrimp loss.
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Alves, Fábio Rui Lima. "Traits of benthic assemblages subjected to different trawling pressure." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/12618.

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Mestrado em Biologia Marinha<br>Over time, fishing techniques improved as a response to the needs of Human populations. Alongside with the increase of fishing activities important changes in the marine ecosystems were also observed (e.g. overexploitation of stocks and habitat loss or degradation). Overfishing, bycatch, discards and ghost-fishing are some of the most discussed impacts of fishing activities, but the effect of bottom trawling should not be underestimated, since it has been proven to have a significant impact of benthic communities. Up to now the knowledge about fisheries impact on deep-sea benthic macrofaunal assemblages is scarce in Europe and, for all we know, even more in Portuguese fishery grounds. However, assessing fisheries impacts on marine ecosystems and ensuring fisheries sustainability is essential to achieve proper management of the sector and for the conservation of marine resources. In this context, the present study was carried out aiming to investigate the impact of continued trawling on benthic macrofaunal assemblages from deep muddy grounds of the burrowing crustacean Nephropsnorvegicus (Norway lobster) by comparing towed and untowed stations regarding their biodiversity, density, biomass, trophic structure, life style and body size spectra. Seven stations were studied along a transect of a highly Fished zone (Area 1, Stations 1 and 2), a Non-fished zone (Area 2, Stations 3, 4 and 5) and another Fished zone (Area 3, stations 6 and 7) during a cruise carried out in September 2012 onboard the RV Garcia del Cid (Consejo Superior de Investigaciones Cientificas) in the framework of the project IMPACT (Universidade do Algarve). In general Fished zones showed decreased heterogeneity and although the results of the multivariate analysis support a significant difference between Fished and Non-fished areas the comparisons of the biodiversity (number of families, H’, EF(n)), density and biomass in Fished and Non-fished zones are inconclusive, inconsistent or even contradict most of the literature predictions. When the trophic structure and life style spectra of the assemblages are compared the decreased heterogeneity of the Fished zones is confirmed but other patterns emerge such as the higher relative contribution of free living organisms, especially meiofaunal predators, grazers and browsers in Fished zones in contrast with the higher relative contribution of tubiculous animals in Non-fished zones, the dominance of deposit feeders over detritus feeders in Fished areas and the presence of large suspension feeders in Non-fished zones. The interpretation of the observed taxonomic and trophic structure of the assemblages is complex and must take into account sources of variability introduced by unwanted alterations of the sampling strategy and habitat heterogeneities in the study area. Overall this study constitutes a good asset for the knowledge of bottom trawling impact on macrofaunal assemblages from deep-sea habitats. It is at this point impossible to estimate the impact of 60 years of bottom trawling and regular monitoring studies are desirable. Some methodological issues arose which can be used as recommendations for future assessments of trawling impacts and monitoring of seafloor integrity: selection of adequate control area(s) must consider habitat heterogeneity, selection of the sampling gear must consider the possible selectivity of smaller samplers; the number of replicates per stations should be sufficiently large to ensure representativeness of biodiversity, abundance and biomass assessment and significance of the comparative tests; and finally, trophic structure, life style and body size spectra showed to be good indicators of change and therefore they should become a more common tool on the assessment of trawling impact.<br>Ao longo do tempo, as artes de pesca têm vindo a evoluir como resposta às crescentes necessidades da população Humana. Ao mesmo tempo que a indústria pesqueira tem vindo a crescer têm-se vindo a observar importantes mudanças nos ecossistemas marinhos (ex. sobreexploração de recursos pesqueiros e perda ou degradação da biodiversidade). A sobre-pesca, pesca de espécies acessórias, rejeições e pesca fantasma são os impactos causados pelas pescas que geram maior preocupação, mas o efeito devastador de pesca de arrasto no fundo oceânico não deve ser subestimado, devido ao seu reconhecido impacto nas comunidades bentónicas. Até aos dias de hoje o conhecimento acerca do impacto em comunidades bentónicas de mar profundo é escasso na Europa e ainda menor em fundos oceânicos Portugueses. Contudo, a avaliação dos impactos da indústria pesqueira em fundos marinhos e nos seus ecossistemas é essencial para obter uma gestão apropriada do setor e para um uso mais sustentável dos recursos biológicos. Neste contexto, este estudo tem como objectivo avaliar o impacto da contínua pressão das pescas de arrasto em comunidades de macrofauna bentónica em fundos lamosos de mar profundo nos habitats do crustáceo Nephrops norvegicus (Lagostim), através da comparação de fundos impactados com fundos nãoimpactados, considerando a análise da biodiversidade, densidade, biomassa, estrutura trófica, espectro de tamanhos e modos de vida. Foram estudadas sete estações ao longo de um transeto, das quais, as primeiras duas estações (estações 1 e 2, área 1) correspondem a uma zona impactada, as seguintes três estações a uma zona não sujeita a pesca de arrasto (estações 3, 4 e 5, área 2,) e, por fim, duas estações (estações 6 e 7, área 3) novamente sujeitas a pressões de pesca de arrasto. A expedição oceanográfica foi realizada em Setembro de 2012 a bordo do navio RV Garcia del Cid (Consejo Superior de Investigaciones Cientificas) inserido no projecto IMPACT (Universidade do Algarve). De um modo geral, as zonas pescadas mostram uma menor heterogeneidade e embora os resultados da análise multivariada suportem uma diferença significante entre zonas pescadas e não-pescadas, as comparações de biodiversidade (número de familias, H’, EF(n)), densidade e biomassa) em zonas pescadas e não-pescadas são inconclusivas, inconsistentes e por vezes contraditórias quando comparadas com a literatura. Quando a estrutura trófica e o estilo de vida das comunidades são comparados, a pequena heterogeneidade nas zonas pescadas é confirmada, mas outros factores emergem, como a contribuição de animais de mobilidade livre, especialmente predadores de meiofauna e raspadores em zonas pescadas, em contraste com a alta contribuição de animais tubículos em zonas não-pescadas, a dominância de detritívoros que se alimentam de matéria orgânica associada ao sedimento sobre detritívoros que se alimentam de matéria orgânica particulada, em zonas pescadas e a presença de grandes suspensívoros em zonas não-pescadas. A interpretação dos resultados taxonómicos e da estrutura trófica é complexa e deve ter em conta variações introduzidas por alterações não esperadas na estratégia de amostragem e diferenças de habitat das zonas estudadas. No geral, este estudo contribui para o conhecimento do impacto de pescas de arrasto em comunidades de macrofauna bentónica de ambientes marinhos profundos. Nestas condições é dificil avaliar quais os efeitos de 60 anos de pressões de pesca de arrasto e futuros estudos são desejáveis. Surgiram alguns problemas metodológicos, o que pode servir como recomendações para futuros estudos de impactos de pesca de arrasto e monitorização da integridade dos fundos oceânicos: uma boa selecção de áreas controlo deve ser considerada; a seleção de tipos de amostradores deve ter em conta a selectividade de amostradores menores; o número de réplicas por estação deve ser suficiente para garantir representatividade da biodiversidade, abundância e biomassa, e a significância de testes comparativos; e por fim, estrutura trófica, espetro de tamanhos e modo de vida mostraram ser bons indicadores de diferenças entre as duas zonas, logo deveriam ser usados mais regularmente na avaliação de impactos de pesca de arrasto.
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Sterling, David J. "Modelling the physics of prawn trawling for fisheries management /." The Gap, Qld. : Sterling Trawl Gear Services, 2005. http://adt.curtin.edu.au/theses/available/adt-WCU20050921.093622.

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Sterling, David John. "Modelling the physics of prawn trawling for fisheries management." Thesis, Curtin University, 2005. http://hdl.handle.net/20.500.11937/2573.

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Management of prawn trawling fisheries is a difficult task due to the competing interests of strongly motivated stakeholders and interest groups. This occurs because prawn trawling operations are technically complex, require large capital investments and exhibit high running costs while owners have limited property rights over the resources that they harvest. Prawn stocks are public resources and are managed with a view to provide maximum benefit to the broad community. Additionally their exploitation also involves the incidental capture of significant numbers of other animals of no commercial value (bycatch) and causes impacts on seabed morphologies, which are involved in many diverse ecosystem processes. At the policy level an intention to manage trawl fisheries in a comprehensive way is backed by a mandated approach that is designed to capture all of the above issues and interests. That approach is termed Ecological Sustainable Development (ESD). The work in this thesis is designed to produce a prediction tool for prawn trawling performance that is based on modelling the physical nature of prawn trawling activities. It is proposed that the resulting tool is essential for working to manage the multi-dimensional aspects of prawn trawling fisheries. Three discrete objectives for the thesis are; to expand and improve an existing Prawn Trawling Performance Model (PTPM) so that it is more accurate and relevant to a broader range of questions, to evaluate the capacity of the PTPM to predict the performance characteristics of real prawn trawling operations in terms of both engineering and catching performance and to investigate the problem space surrounding prawn trawl fisheries to identify and develop applications for the model. A rudimentary PTPM (Sterling 2000b) is expanded through the analysis of further empirical data collected for model and full-scale trawl gear.ght area of improvement to the PTPM were considered and in all cases significant changes were made. The accuracy of the new form of the model is here tested by comparing performance predictions with measurements of trawling performance for a variety of industrial trawl systems operated in the Queensland East Coast Trawl Fishery and also through comparing predicted trawling performance with prawn catches returned for trawlers operating in the Northern Prawn Fishery over the years 1970 to 2000. In the first case, errors in predicting swept area rate, considered an important performance parameter, were less than 5%. Fine scale issues were explored using the available sea mal data and a number of areas of concern within the model are highlighted. These relate to accurately quantifying the forces involved in the interaction of the trawl gear with the seabed and accurately accounting for the interaction between components within trawl systems. In the second case, the results suggest that between 50% and 60% of the variation in the seasonal catching performance of trawlers in the NPF is explained by predictions of swept area rate derived by the PTPM from the available data for that fishery. A comprehensive survey of applications for the PTPM is conducted in context with approaching the management of prawn trawling fisheries using the principles of ESD as defined by the National Strategy for ESD (1992). The Northern Prawn Fishery is used as a case study to explore in finer detail applications for the PTPM. Issues arising from the implementation of some of the applications are discussed.
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Sterling, David John. "Modelling the physics of prawn trawling for fisheries management." Curtin University of Technology, School of Physical Sciences, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16093.

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Management of prawn trawling fisheries is a difficult task due to the competing interests of strongly motivated stakeholders and interest groups. This occurs because prawn trawling operations are technically complex, require large capital investments and exhibit high running costs while owners have limited property rights over the resources that they harvest. Prawn stocks are public resources and are managed with a view to provide maximum benefit to the broad community. Additionally their exploitation also involves the incidental capture of significant numbers of other animals of no commercial value (bycatch) and causes impacts on seabed morphologies, which are involved in many diverse ecosystem processes. At the policy level an intention to manage trawl fisheries in a comprehensive way is backed by a mandated approach that is designed to capture all of the above issues and interests. That approach is termed Ecological Sustainable Development (ESD). The work in this thesis is designed to produce a prediction tool for prawn trawling performance that is based on modelling the physical nature of prawn trawling activities. It is proposed that the resulting tool is essential for working to manage the multi-dimensional aspects of prawn trawling fisheries. Three discrete objectives for the thesis are; to expand and improve an existing Prawn Trawling Performance Model (PTPM) so that it is more accurate and relevant to a broader range of questions, to evaluate the capacity of the PTPM to predict the performance characteristics of real prawn trawling operations in terms of both engineering and catching performance and to investigate the problem space surrounding prawn trawl fisheries to identify and develop applications for the model. A rudimentary PTPM (Sterling 2000b) is expanded through the analysis of further empirical data collected for model and full-scale trawl gear.<br>ght area of improvement to the PTPM were considered and in all cases significant changes were made. The accuracy of the new form of the model is here tested by comparing performance predictions with measurements of trawling performance for a variety of industrial trawl systems operated in the Queensland East Coast Trawl Fishery and also through comparing predicted trawling performance with prawn catches returned for trawlers operating in the Northern Prawn Fishery over the years 1970 to 2000. In the first case, errors in predicting swept area rate, considered an important performance parameter, were less than 5%. Fine scale issues were explored using the available sea mal data and a number of areas of concern within the model are highlighted. These relate to accurately quantifying the forces involved in the interaction of the trawl gear with the seabed and accurately accounting for the interaction between components within trawl systems. In the second case, the results suggest that between 50% and 60% of the variation in the seasonal catching performance of trawlers in the NPF is explained by predictions of swept area rate derived by the PTPM from the available data for that fishery. A comprehensive survey of applications for the PTPM is conducted in context with approaching the management of prawn trawling fisheries using the principles of ESD as defined by the National Strategy for ESD (1992). The Northern Prawn Fishery is used as a case study to explore in finer detail applications for the PTPM. Issues arising from the implementation of some of the applications are discussed.
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Bloomfield, Helen J. "Compliance and control : a multidisciplinary assessment of prohibited trawling areas." Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613446.

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Stella, Leonie. "Trawling deeper seas : the gendered production of seafood in Western Australia /." Access via Murdoch University Digital Theses Project, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040913.155811.

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Magorrian, Bridgeen Helen. "The impact of commercial trawling on the benthos of Strangford Lough." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318751.

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Britton, Adam Robert Corden. "Flight performance, echolocation and prey capture behaviour in trawling Myotis bats." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319104.

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Stella, Leonie C. "Trawling deeper seas: the gendered production of seafood in Western Australia." Thesis, Stella, Leonie C. (1998) Trawling deeper seas: the gendered production of seafood in Western Australia. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/346/.

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This thesis explores the sexual division of labour in three worksites associated with the Western Australian Fishing industry: fishers' households, a seafood processing company and fishing vessels. There has been no previous substantial study of the labour of women in Australian fishing industries. My research has been primarily undertaken by interviewing women and men who work in the Western Australian fishing industry, and my findings are presented through a comparison with overseas literature relative to each site. As I found, in the households of fishermen, women do unpaid and undervalued labour which includes servicing men and children; managing household finances and operating fishing enterprises. In seafood processing companies women are allocated the lowest paid and least rewarding work which is regarded as women's work. On-the factory floor issues of class, race/ ethnicity and gender intersect so that the majority of women employed in hands-on processing work are migrant women from a non-English speaking background. The majority of women who work at sea are cook/ deckhands who are confronted by a rigid sexual division of labour, and work in a hyper-masculine workplace. The few other women who have found a niche which enables them to enjoy an outdoor lifestyle while they earn their own living, are those who work as autonomous independent small boat fishers. In each site there is evidence that women, individually and collectively, exercise some power in determining how and where they work, but they remain marginalised from the more lucrative sites of the industry, and have limited access to economic and social power.
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Books on the topic "Trawling"

1

Nicklin, John. Trawling with the lid off. Aurora, 1996.

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1935-, O'Grady Desmond, ed. Trawling tradition: Translations, 1954-1994. University of Salzburg, 1994.

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Richard, George. An assessment of trawling technology in Canada. Program Planning and Coordination, Fisheries Management, Fisheries and Oceans Canada, 1999.

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Jarvis, Charlotte, ed. Threats to Our Ocean Heritage: Bottom Trawling. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-57953-0.

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Mbuga, James Siwo. Trawling in Lake Victoria: Its history, status, and effects. IUCN Eastern Africa Regional Office, 1998.

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Raja, B. T. Anthony. High-opening bottom trawling in Tamil Nadu, Gujarat and Orissa, India: A summary of effort and impact. Development of Small-Scale Fisheries in the Bay of Bengal, 1987., 1987.

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Fournier, Denis. Recueil de données: Campagne de chalutage à la rencontre de l'estuaire fluvial et moyen du Saint-Laurent en 2001. Société de la faune et des parcs du Québec, 2002.

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Great Britain. Sea Fish Industry Authority., Institut français de recherche pour l'exploitation de la mer., Danish Institute for Fisheries Technology and Aquaculture., and Commission of the European Communities., eds. Les panneaux de chalut: Caractéristiques et mise en œuvre. Editions IFREMER, 1995.

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Alegre, Toni Llabrés. Es bolitx: La pesca de bolitx al port de Maó. Institut Menorquí d'Estudis, 1997.

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Clark, William G. Washington's trawl logbook data, past and present. State of Washington, Dept. of Fisheries, 1986.

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Book chapters on the topic "Trawling"

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Jarvis, Charlotte, and Michael L. Brennan. "History of Trawling and Ecological Impact." In SpringerBriefs in Archaeology. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-57953-0_2.

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AbstractBottom trawling developed from the practice of fishing with a net or long lines, but that older style was able to be more controlled and discriminate in its catch. With bottom trawling, nets are weighted to keep them low along the seafloor and a large beam on deck spreads nets wide to increase catch. Marine biologists and environmentalists have been concerned about trawling since it began. As far back as 1376, the English parliament highlighted the destructive nature of the practice to fish populations and habitats, noting that it ‘runs so heavily and hardly over the ground when fishing that it destroys the flowers of the land’ and takes so many fish ‘to the great damage of the commons and the destruction of the fisheries’ (Petition by the Commons to King Edward III, 1376 seen in Bolster, 2012). This first known mention of trawling calls for the removal of the practice and yet the activity endures. Trawling in Europe continued sporadically through the medieval and early modern periods using mainly the beam trawl method until the early nineteenth century when the industrial revolution pushed the technology further.
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Majcher, Jan, Rory Quinn, Gert Normann Andersen, and David Gregory. "Wreck Sites as Systems Disrupted by Trawling." In SpringerBriefs in Archaeology. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-57953-0_5.

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AbstractThis chapter examines the effects of bottom trawling on shipwreck sites, conceptualising them as process-response systems that achieve a quasi-equilibrium state over time. Disruptions to this state by bottom-contact fishing gear are analysed through examples from recent geophysical surveys in the Irish, Baltic, and North Seas. The study highlights the capabilities and limitations of modern geophysical methods in detecting changes at underwater archaeological sites caused by bottom trawling. Specifically, it addresses the challenges of identifying evidence of disturbance on dynamic seabeds and suggests that detailed analysis of wreck distribution might provide indirect proxies of structural damage due to trawling activities. Furthermore, it emphasises the potential of these disturbances to mobilise hazardous materials, such as unexploded ordnance and fuel from modern shipwrecks, posing an added environmental risk. Acknowledging existing knowledge gaps in the understanding of trawling impacts on underwater cultural heritage and the marine environment, the authors call for more case study research .
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McLoughlin, John. "Trawling for flat superficial bladder tumour." In Top Tips in Urology. John Wiley & Sons, Ltd, 2013. http://dx.doi.org/10.1002/9781118508060.ch109.

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Tang, Ying, Xinsheng Yu, and Ni Wang. "Trawling Pattern Analysis with Neural Classifier." In Lecture Notes in Computer Science. Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11881070_81.

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Jarvis, Charlotte. "Introduction." In SpringerBriefs in Archaeology. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-57953-0_1.

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AbstractTrawling has been recognised as a profoundly damaging practice with lasting negative consequences on seabed ecology and marine life since its first mention in a 1376 parliamentary petition. Mobile fishing gear (including any dredge, trawl, or similar device) is used to tow or push a net with a boat to catch fish. Bottom trawling, in particular, grew from a need to keep up with declining fish stocks and developed further with technological changes and increased demands, though it created ‘anger and resentment’ within the fishing communities (Bolster, 2012, p. 236). All three trawling revolutions—invention, mechanisation, and later deep-water expansion—have been met with controversy and pushback by the public and environmentalists alike (Roberts, 2008).
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Ermida, Maria Pena. "The Duty to Protect Our Ocean Heritage from Bottom Trawling." In SpringerBriefs in Archaeology. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-57953-0_3.

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AbstractThis chapter seeks to provide an overview of the legal framework surrounding the protection of UCH as a part of the Marine Environment within the context of law of the Sea, focusing particularly on the rules regarding bottom trawling.
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Gunnarsson, Guđmunder. "Deep-Water Trawling Techniques Used by Icelandic Fishermen." In Deep-Water Fisheries of the North Atlantic Oceanic Slope. Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-015-8414-2_19.

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Francis, Dileep, Teja Karthik Yadagini, and Resmi Ravindran. "Trawling the Genome: Drug Target Identification in the Postgenomic Era." In Drugs from Nature: Targets, Assay Systems and Leads. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-9183-9_3.

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Menzies, Robert J. "Improved Techniques for Benthic Trawling at Depths Greater than 2000 Meters." In Biology of the Antarctic Seas. American Geophysical Union, 2013. http://dx.doi.org/10.1029/ar001p0093.

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De Simone, Michela, Anna Di Cosmo, Ornella Nonnis, et al. "Analysis of the amphipod syntaxon on hard bottoms anti-trawling structures." In Monitoring of Mediterranean Coastal Areas: Problems and Measurement Techniques. Firenze University Press, 2024. https://doi.org/10.36253/979-12-215-0556-6.16.

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This work is part of an environmental monitoring project conducted by Ispra since 2008, with the installation of two marine cables between the Lazio coast and Sardinia. Following the deployment of anti-trawl tripods, since 2017, a new Ispra monitoring plan was established to assess the integrity of the marine environment. The anti-trawl tripods have been periodically analyzed to examine various aspects of the marine area where they have been installed, including any changes in faunal and algal biodiversity resulting from the introduction of artificial structures. This study involves observing recruitment on the anti-trawl barriers to assess the colonization of artificial substrates introduced into the marine environment.
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Conference papers on the topic "Trawling"

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West, B. "1986 Bering Sea Trawling Impact Project." In OCEANS '87. IEEE, 1987. http://dx.doi.org/10.1109/oceans.1987.1160761.

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Wu, Jie, Chittiappa Muthanna, Hagbart Alsos, Rasmus Juhlin, and Daniel Karunakaran. "Experimental Investigation of Over-Trawlability of an Innovative Arctic Subsea Production Unit (SPU)." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95503.

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Abstract Model tests have been performed to examine the overtrawlability of Subsea7’s Subsea Production Unit (SPU) in SINTEF Ocean’s Ocean Laboratory in November/December 2017. In this test campaign, 50 tests with different SPU orientations and trawling equipment were carried out. Two trawling water depth (100 m and 500 m) were simulated in the model test. Two types of trawl door, i.e. Thyborøn (5.5t) and Poly Ice (3.8t), with Selstad No. 620 type fishing net were used in present test. Overtrawling with a roller clump (7.6t) was also tested. Two trawling speeds of 1.6 m/s and 2.6 m/s and 5 SPU orientations were examined. Force measurements both on the fishing lines, and directly measured on the SPU were used to determine overtrawlability of the SPU. The dynamometer used in present test to measure the forces directly on the SPU is the first time that this type of measurement has been undertaken at SINTEF Ocean at the Ocean Basin facility with fully modelled trawling gear.
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Yu, Xinsheng, Dejun Gong, Ying Tang, and Ni Wang. "Detection of Trawling Patterns in Seabed Images." In OCEANS 2006. IEEE, 2006. http://dx.doi.org/10.1109/oceans.2006.306901.

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Biryukov, A., I. Pustogarov, and R. Weinmann. "Trawling for Tor Hidden Services: Detection, Measurement, Deanonymization." In 2013 IEEE Symposium on Security and Privacy (SP) Conference. IEEE, 2013. http://dx.doi.org/10.1109/sp.2013.15.

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Wu, Xiaopeng, Vegard Longva, Svein Sævik, and Torgeir Moan. "Simulation of Hooking Event in Fish Trawling Operation." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10490.

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Interference between trawl gears and subsea pipelines is an important issue. A special case called hooking, defined as the situation when the trawl gear gets “stuck” under the pipeline, should be a rarely occurring situation. In this case, however, the warp line tension could be high as its breaking strength. This may be detrimental with respect to both fishing vessel safety and pipeline integrity. This calls for a better understanding of the hooking phenomenon. The goal of this study is to develop a proper numerical model to describe the hooking event. The proposed model is based on the finite element method. A special penalty-based contact element that includes the friction effect is utilized to deal with the trawl board and pipeline interaction. The trawl board and seabed (span shoulder) contact is also accounted for in order to simulate the hooking event. To validate the proposed model, numerical simulation results are compared with previous model test results. A rectangular type trawl board was selected as the target object. The pull-over cases with different span height were firstly tested and compared. Then, the hooking event set-ups were modeled. Based on the model tests, there are two most likely scenarios for hooking: 1) a de-stabilized trawl board with small span height; 2) small crossing angle with large span height. The above two cases were both tested by the proposed model. In the first case, the trawl board is towed flat on the seabed. Permanent hooking was successfully obtained in the simulation. Then, two cases with small crossing angle were studied. Hooking event was reproduced in the case of a 20 degree crossing angle by introducing a disturbance on the trawl board. It shows that the proposed model could reproduce the hooking event, provided that the trawl board motion similar to the model test could be obtained. This gives a good basis for further studies.
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Xiao, Yujia. "PassRVAE: Improved Trawling Attacks via Recurrent Variational Autoencoder." In CNSCT 2024: 2024 3rd International Conference on Cryptography, Network Security and Communication Technology. ACM, 2024. http://dx.doi.org/10.1145/3673277.3673295.

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Balash, Cheslav, David Sterling, Matt Broadhurst, Arno Dubois, and Morgan Behrel. "Hydrodynamic Evaluation of a Generic Sail Used in an Innovative Prawn-Trawl Otter Board." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41335.

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In prawn-trawling operations, otter boards provide the horizontal force required to maintain net openings, and are typically low aspect ratio (∼0.5) flat plates operating on the seabed at high angles of attack (AOA; 35–40°). Such characteristics cause otter boards to account for up to 30% of the total trawling resistance, including that from the vessel. A recent innovation is the batwing otter board, which is designed to spread trawls with substantially less towing resistance and benthic impacts. A key design feature is the use of a sail, instead of a flat plate, as the hydrodynamic foil. The superior drag and benthic performance of the batwing is achieved by (i) successful operation at an AOA of ∼20° and (ii) having the heavy sea floor contact shoe in line with the direction of tow. This study investigated the hydrodynamic characteristics of a generic sail by varying its twist and camber, to identify optimal settings for maximum spreading efficiency and stability. Loads in six degrees of freedom were measured at AOAs between 0 and 40° in a flume tank at a constant flow velocity, and with five combinations of twist and camber. The results showed that for the studied sail, the design AOA (20°) provides a suitable compromise between greater efficiency (occurring at lower AOAs) and greater effectiveness (occurring at higher AOAs). At optimum settings (20°, medium camber and twist), a lift-to-drag ratio &gt;3 was achieved, which is ∼3 times more than that of contemporary prawn-trawling otter boards. Such a result implies relative drag reductions of 10–20% for trawling systems, depending on the rig configuration.
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Masu, Lorenzo, Leonardo Cardinali, and Stefania Benucci. "Scraping Damage Hazard Due to Trawling Interference on Subsea Pipelines." In Proceedings of the 29th European Safety and Reliability Conference (ESREL). Research Publishing Services, 2020. http://dx.doi.org/10.3850/978-981-14-8593-0_4064-cd.

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Yu, Fangyi, and Miguel Vargas Martin. "GNPassGAN: Improved Generative Adversarial Networks For Trawling Offline Password Guessing." In 2022 IEEE European Symposium on Security and Privacy Workshops (EuroS&PW). IEEE, 2022. http://dx.doi.org/10.1109/eurospw55150.2022.00009.

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Polanco-Loria, Mario A., Håvar Ilstad, and Erik Levold. "A Numerical-Experimental Approach of Indentation Problem: Part I — Force-Dent Response of Steel Pipes." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61890.

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Accidents by trawling impact have the potential of environmental consequences, in terms of safety, monetary values and reputation. Aware of this situation a technology development plan on “Pipeline subject to high interference loads” has been established at STATOIL in close collaboration with GASSCO. The overall achievement is to adapt and introduce more reliable assessment methods in the load and response of pipelines under a trawling impact scenario. This work includes a review of some known force-indentation models appeared in the literature. Some comments on the recently updated version of the DNV-RP-F111 document. Next, the description of the numerical results of 12 analyses of steel pipes studied is described and based on these results a new force-dent proposal is presented. The proposed equations are validated against experimental tests and the findings indicated fairly good predictions as indicated in the conclusions.
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Reports on the topic "Trawling"

1

Steenbergen, Josien, Mattias van Opstal, Jasper Van Vlasselae, Tony Wilkes, and Tom Bangma. Selectivity of shrimp pulse trawling versustraditional shrimp beam trawling : Results of a baseline and innovation study. Wageningen Marine Research, 2021. http://dx.doi.org/10.18174/560348.

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Turenhout, M. N. J., B. W. Zaalmink, W. J. Strietman, and K. G. Hamon. Pulse trawling in the Netherlands : economic and spatial impact study. Wageningen Economic Research, 2016. http://dx.doi.org/10.18174/396469.

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Sommer, Stefan, and Andrew W. Dale. Field-experiment to determine the short-term impact of bottom trawling on the benthic ecosystem in the German coastal Baltic Sea - Cruise No. AL616, 18.07. – 09.08.2024, Kiel (Germany) – Kiel (Germany), MGF-OSTSEE-2024. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2025. https://doi.org/10.3289/cr_al616.

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Within the BMBF funded second phase of the DAM project „Ausschluss mobiler grund-berührender Fischerei (MGF) in marinen Schutzgebieten der Ostsee – Phase II (MGF-Ostsee-II)“ an experimental field study has been conducted to determine the effects of bottom trawling on the benthic ecosystem of the German coastal Baltic Sea. An area characterized with low fishing activity was selected in the Mecklenburger Bight ca. 5 km north of the town Kühlungsborn based on geo-acoustic and sedimentological criteria. In a part of this area referred to as High Impact area, high intensity trawling was simulated by performing several trawls, whereas in the neighboring control area the sediments were undisturbed. Both areas were repeatedly investigated over a period of 3 weeks using biogeochemical sediment analyses, in situ benthic flux measurements and visual seafloor inspection to determine the response and changes of the benthic ecosystem to the trawling impact. Further biogeochemical analyses were conducted in sediment push cores taken by divers from specific sediment features of trawl mark tracks. In addition, physico-chemical investigations were carried out of the suspended particle plume generated during trawling as well as seafloor imaging to decipher the degree of disturbance and redistribution of sediments possibly affecting benthic communities. A total of 97 stations were sampled, including 38 MUC casts, 18 XOFOS surveys, 10 BIGO, 6 DSR and 7 CTD/water sampling rosette deployments. (Alkor-Berichte AL616)
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van de Wolfshaar, K. E., T. van Kooten, and A. D. Rijnsdorp. Lethal and non-lethal effects of trawling on the benthic invertebrate food web. Wageningen Marine Research, 2020. http://dx.doi.org/10.18174/514206.

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Schram, Edward, and Pieke Molenaar. Direct mortality among demersal fish and benthic organisms in the wake of pulse trawling. Wageningen Marine Research, 2019. http://dx.doi.org/10.18174/504087.

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Schram, Edward, Pieke Molenaar, and Susan de Koning. Direct mortality among demersal fish and benthic organisms in the wake of pulse trawling. Wageningen Marine Research, 2021. http://dx.doi.org/10.18174/541793.

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Sommer, Stefan. Potential effects of the exclusion of bottom fishing in the marine protected areas (MPAs) of the western Baltic Sea – third year observations Cruise No. AL570 22.03. – 11.04.2022, Kiel (Germany) – Kiel (Germany) MGF-OSTSEE-2022. GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, 2022. http://dx.doi.org/10.3289/cr_al570.

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The expedition AL570 with the RV Alkor was carried out within the framework of the interdisciplinary DAM MGF-OSTSEE Project “Potential effects of closure for bottom fishing in the marine protected areas (MPAs) of the western Baltic Sea – baseline observations” funded by the Ministry of Education and Research (BMBF). Within MGF-OSTSEE a consortium of scientists from various institutions investigates how benthic ecosystems in Natura 2000 areas within the German exclusive economic zone develop after the exclusion of bottom trawling. Major goals of the project are i. the initial assessment of the environmental state and its variability in- and outside the three Natura 2000 areas Fehmarnbelt, Oder- and Rönnebank under the ongoing pressure of bottom trawling and ii. the general assessment of the effect of bottom trawling on benthic communities and benthic biogeochemical functioning as well as their development after fishery exclusion. The cruise AL570 concludes a series of three previous expeditions EMB238 (2020) and EMB267/268 (2021) and aimed to survey all components of the benthic food web including prokaryotes, protozoans, meiofauna and macrofauna, as well as sediment properties and biogeochemical processes in selected working areas in- and outside of the MPA. The working program comprised 156 station activities of various gears for biological and biogeochemical sampling of sediments. Solute exchange between the sediment and the water column was investigated using Landers and a novel underwater vehicle the Deep-Sea Rover (DSR) Panta Rhei. Investigations in the water column, seafloor observation and deployments of a dredge supplemented the station work. Due to stormy weather in situ solute fluxe measurements were not performed at the Rönnebank. (Alkor-Berichte ; AL570)
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King, E. L., A. Normandeau, T. Carson, et al. Pockmarks, a paleo fluid efflux event, glacial meltwater channels, sponge colonies, and trawling impacts in Emerald Basin, Scotian Shelf: autonomous underwater vehicle surveys, William Kennedy 2022011 cruise report. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331174.

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A short but productive cruise aboard RV William Kennedy tested various new field equipment near Halifax (port of departure and return) but also in areas that could also benefit science understanding. The GSC-A Gavia Autonomous Underwater Vehicle equipped with bathymetric, sidescan and sub-bottom profiler was successfully deployed for the first time on Scotian Shelf science targets. It surveyed three small areas: two across known benthic sponge, Vazella (Russian Hat) within a DFO-directed trawling closure area on the SE flank of Sambro Bank, bordering Emerald Basin, and one across known pockmarks, eroded cone-shaped depression in soft mud due to fluid efflux. The sponge study sites (~ 150 170 m water depth) were known to lie in an area of till (subglacial diamict) exposure at the seabed. The AUV data identified gravel and cobble-rich seabed, registering individual clasts at 35 cm gridded resolution. A subtle variation in seabed texture is recognized in sidescan images, from cobble-rich on ridge crests and flanks, to limited mud-rich sediment in intervening troughs. Correlation between seabed topography and texture with the (previously collected) Vazella distribution along two transects is not straightforward. However there may be a preference for the sponge in the depressions, some of which have a thin but possibly ephemeral sediment cover. Both sponge study sites depict a hereto unknown morphology, carved in glacial deposits, consisting of a series of discontinuous ridges interpreted to be generated by erosion in multiple, continuous, meandering and cross-cutting channels. The morphology is identical to glacial Nye, or mp;lt;"N-mp;lt;"channels, cut by sub-glacial meltwater. However their scale (10 to 100 times mp;lt;"typicalmp;gt;" N-channels) and the unique eroded medium, (till rather than bedrock), presents a rare or unknown size and medium and suggests a continuum in sub-glacial meltwater channels between much larger tunnel valleys, common to the eastward, and the bedrock forms. A comparison is made with coastal Nova Scotia forms in bedrock. The Emerald Basin AUV site, targeting pockmarks was in ~260 to 270 m water depth and imaged eight large and one small pockmark. The main aim was to investigate possible recent or continuous fluid flux activity in light of ocean acidification or greenhouse gas contribution; most accounts to date suggested inactivity. While a lack of common attributes marking activity is confirmed, creep or rotational flank failure is recognized, as is a depletion of buried diffuse methane immediately below the seabed features. Discovery of a second, buried, pockmark horizon, with smaller but more numerous erosive cones and no spatial correlation to the buried diffuse gas or the seabed pockmarks, indicates a paleo-event of fluid or gas efflux; general timing and possible mechanisms are suggested. The basinal survey also registered numerous otter board trawl marks cutting the surficial mud from past fishing activity. The AUV data present a unique dataset for follow-up quantification of the disturbance. Recent realization that this may play a significant role in ocean acidification on a global scale can benefit from such disturbance quantification. The new pole-mounted sub-bottom profiler collected high quality data, enabling correlation of recently recognized till ridges exposed at the seabed as they become buried across the flank and base of the basin. These, along with the Nye channels, will help reconstruct glacial behavior and flow patterns which to date are only vaguely documented. Several cores provide the potential for stratigraphic dating of key horizons and will augment Holocene environmental history investigations by a Dalhousie University student. In summary, several unique features have been identified, providing sufficient field data for further compilation, analysis and follow-up publications.
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Schmidt, Mark. Dynamics and variability of POC burial in depocenters of the North Sea (Skagerrak), Cruise No. AL561, 2.08.2021 – 13.08.2021, Kiel – Kiel, APOC. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2021. http://dx.doi.org/10.3289/cr_al561.

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The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise. - (Alkor-Berichte ; AL561)
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10

Axenrot, Thomas, Erik Degerman, and Anders Asp. Seasonal variation in thermal habitat volume for cold-water fish populations : implications for hydroacoustic survey design and stock assessment. Department of Aquatic Resources, Swedish University of Agricultural Sciences, 2023. http://dx.doi.org/10.54612/a.5i05rb1iu1.

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Abstract:
For accurate stock assessment, survey design must consider fish behavior and ecology. Yearlings and older individuals of the commercially exploited cold-water species vendace (Coregonus albula) are found below the metalimnion through periods of thermal stratification. These stratification periods generally last for 3-4 months, from the middle of summer to early autumn. In lakes with heterogeneous distribution of depths, the habitat volume for vendace vary drastically within and across years, which affects the distribution and population densities. Variable thermal habitat volumes, with food and oxygen depletion in the hypolimnion through the period of stratification, may act as a population size-regulating factor. Using hydroacoustics in combination with trawl data and temperature profiles, we examined the distribution of vendace through annual periods of thermal stratification. We found that yearling and older vendace these periods were confined to cold-water habitat volumes representing less than 10 % of the total water volume of Lake Mälaren, the third largest lake in Sweden. By introducing stratification to the design of hydroacoustic surveys supported by midwater trawling, seasonal aggregations of fish in temporally restricted thermal habitat volumes can be used to lower survey effort and improve the precision in estimates of population size. Temporally restricted habitat volumes may induce risks for the populations to over-fishing and sensitivity to environmental changes that potentially may call for directed management.
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