Gotowe bibliografie tematyczne / Demersal Fisheries

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Gotowa bibliografia na temat „Demersal Fisheries”

Autor: Grafiati
Data publikacji: 6 września 2023
Data aktualizacji: 7 września 2023

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Artykuły w czasopismach na temat "Demersal Fisheries"

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Waldo, Staffan, i Anton Paulrud. "ITQs in Swedish demersal fisheries". ICES Journal of Marine Science 70, nr 1 (17.09.2012): 68–77. http://dx.doi.org/10.1093/icesjms/fss141.

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Abstract Waldo, S., and Paulrud, A. 2013. ITQs in Swedish demersal fisheries. – ICES Journal of Marine Science, 70:68–77. Individual transferable quota (ITQ) is a management measure that is widely discussed, not least in the reform of the European Common Fisheries Policy. While the system is expected to reduce overcapacity and improve economic performance, questions are raised concerning the future of small-scale fisheries. This paper uses a model for Swedish fisheries (the Swedish Resource Rent Model for the Commercial Fisheries, SRRMCF) where the economics and fleet structure in a potential Swedish ITQ-system are analysed. The model is an optimization model based on linear programming and data from the European Union's data collection framework. The modelling approach can readily be used by other member states. Three main conclusions can be drawn on how ITQs will affect fisheries: The fishing fleet measured in number of vessels will decrease by approximately 30–50%.Profitability will increase so that the fishing industry will be able to provide competitive wages and make a financial contribution to fisheries management.The system can be designed so that small-scale fisheries are not disadvantaged.
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Dharmadi, Dharmadi, Fahmi Fahmi i William White. "BIODIVERSITY OF SHARKS AND RAYS IN SOUTH EASTERN INDONESIA". Indonesian Fisheries Research Journal 15, nr 2 (24.05.2017): 17. http://dx.doi.org/10.15578/ifrj.15.2.2009.17-28.

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Indonesia has a very diverse shark and ray fauna and is the largest chondrichthyan fisheries in the world. Most of the sharis are caught by longlines and gillnets and rays are caught both as target, e.g. in the tangle net and demersal gillnet fisheries, and as bycatch in other fisheries such as in demersal and drift gittnet, trammel net a-nd long line fisheries.
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Luasunaung, Alfret, Mariane M. Kayadoe, Frangky E. Kaparang i Marvin Lestaluhu. "Analysis of CPUE and Fishing Capacity of demersal fisheries in Kema 2, North Sulawesi, Indonesia". International Journal of Advanced Engineering, Management and Science 8, nr 10 (2022): 22–28. http://dx.doi.org/10.22161/ijaems.810.4.

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Capture fisheries should be a sustainable economic activity aspect to provide good benefits to future resources. Sustainable marine fisheries resources exploitation requires a utilization rate lower than their availability. Therefore, the exploitation rate should not achieve the recovery ability of the resources in certain time. In fishing activities, for instance, there is a guideline not to catch fish over the Total Allowable Catch (TAC), 80% of the MSY. Information on the potency and the fishing capacity of tuna fisheries can be useful for the sustainable management of the resources. Also, this information can be used as a consideration for further management of the potency. There are two purposes of the study: (1) to analyze the CPUE (catch per unit effort) of demersal fisheries in Kema 2, North Sulawesi, for prediction of their potency, and (2) to analyze the efficiency of fishing capacity of the demersal fisheries in Kema 2, The study was done in two stages. The first was done by analyzing the potency using CPUE method (Shaefer models) to obtain the MSY, optimum effort and TAC (total allowable catch); and the second was done by analyzing the fishing capacity of demersal fisheries using DEA method to estimate the efficiency level of the fishing boats and devices in Kema 2. The result showed that the potency of demersal fisheries in Kema 2 was 71,700 tons per year and the optimum effort was 72,964 trips. Fishing capacity in demersal fisheries occurred in Kema 2 for the last 12 years was inefficient, especially for 2001. This may be caused by some factors such as trip operation, fishing duration, oil consumption, crew and operational cost. So, to manage the demersal resources in Kema 2, the TAC should be 57,520 tons per year. Based on the result, to increase the fishing efficiency, we should take into account of above factors. We suppose that the good means is reducing trip operation, fishing duration, oil consumption, crew and operational cost.
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Cohen, Daniel M., Nigel R. Merrett i Richard L. Haedrich. "Deep-Sea Demersal Fish and Fisheries". Copeia 1999, nr 3 (2.08.1999): 843. http://dx.doi.org/10.2307/1447628.

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Zahara, Asha Aulia, Audya Septria Ningrum, Baiq Kharisma Afrilia Putri Zain, Ivonne Siswanty i Selamet Kurniawan Riandinata. "Identifikasi Jenis Ikan Demersal dan Pengelolaan Perikanan Tangkap Berkelanjutan di Pasar Ikan Anaiwoi Kabupaten Kolaka". Journal of Marine Research 12, nr 3 (23.05.2023): 422–30. http://dx.doi.org/10.14710/jmr.v12i3.37074.

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Perikanan tangkap adalah sumber daya yang dapat diakses secara terbuka atau milik bersama yang penggunaannya dapat mengalami penangkapan berlebih atau penangkapan ikan yang merusak jika ditangani tanpa menggunakan konsep yang ramah lingkungan dan berkelanjutan. Penelitian ini bertujuan untuk mengidentifikasi jenis ikan demersal hasil tangkapan nelayan dan mengetahui pengelolaan perikanan tangkap di perairan Desa Anaiwoi. Penelitian dilakukan pada bulan September hingga Oktober 2022 di Pasar Ikan Anaiwoi, Kabupaten Kolaka. Metode yang digunakan adalah metode wawancara dan dokumentasi. Berdasarkan hasil penelitian, terdapat 31 spesies ikan demersal yang termasuk dalam 12 famili. Jenis ikan yang paling dominan ditemukan dari famili Lutjanidae dan Lethrinidae. Secara umum hasil identifikasi perikanan berkelanjutan cukup baik, seperti alat tangkap, jenis kapal ramah lingkungan, lokasi penangkapan dan jenis ikan serta ukuran ikan yang ditangkap. Jenis perahu yang paling banyak digunakan nelayan adalah perahu motor tempel. Alat tangkap yang paling umum digunakan adalah tali pancing.Capture fisheries are openly accessible resources or common property whose use may experience overfishing or destructive fishing if handled without using environmentally friendly and sustainable concepts. This study aims to identify the species of demersal fish caught by fishermen and to determine the management of capture fisheries in the waters of Anaiwoi Village. The research was conducted from September to October 2022 at the Anaiwoi Fish Market, Kolaka District. The method used is the interview and documentation method. Based on the results of the study, there were 31 species of demersal fish belonging to 12 families. The most dominant fish species were found from the Lutjanidae and Lethrinidae families. In general, the identification results of sustainable fisheries are quite good, such as fishing gear, types of environmentally friendly vessels, fishing locations and types of fish and size of fish caught. The type of boat most used by fishermen is the outboard motor. The most commonly used fishing gear is the fishing line.
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Zahara, Asha Aulia, Audya Septria Ningrum, Baiq Kharisma Afrilia Putri Zain, Ivonne Siswanty i Selamet Kurniawan Riandinata. "Identifikasi Jenis Ikan Demersal dan Pengelolaan Perikanan Tangkap Berkelanjutan di Pasar Ikan Anaiwoi Kabupaten Kolaka". Journal of Marine Research 12, nr 3 (23.05.2023): 422–30. http://dx.doi.org/10.14710/jmr.v12i3.37074.

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Perikanan tangkap adalah sumber daya yang dapat diakses secara terbuka atau milik bersama yang penggunaannya dapat mengalami penangkapan berlebih atau penangkapan ikan yang merusak jika ditangani tanpa menggunakan konsep yang ramah lingkungan dan berkelanjutan. Penelitian ini bertujuan untuk mengidentifikasi jenis ikan demersal hasil tangkapan nelayan dan mengetahui pengelolaan perikanan tangkap di perairan Desa Anaiwoi. Penelitian dilakukan pada bulan September hingga Oktober 2022 di Pasar Ikan Anaiwoi, Kabupaten Kolaka. Metode yang digunakan adalah metode wawancara dan dokumentasi. Berdasarkan hasil penelitian, terdapat 31 spesies ikan demersal yang termasuk dalam 12 famili. Jenis ikan yang paling dominan ditemukan dari famili Lutjanidae dan Lethrinidae. Secara umum hasil identifikasi perikanan berkelanjutan cukup baik, seperti alat tangkap, jenis kapal ramah lingkungan, lokasi penangkapan dan jenis ikan serta ukuran ikan yang ditangkap. Jenis perahu yang paling banyak digunakan nelayan adalah perahu motor tempel. Alat tangkap yang paling umum digunakan adalah tali pancing.Capture fisheries are openly accessible resources or common property whose use may experience overfishing or destructive fishing if handled without using environmentally friendly and sustainable concepts. This study aims to identify the species of demersal fish caught by fishermen and to determine the management of capture fisheries in the waters of Anaiwoi Village. The research was conducted from September to October 2022 at the Anaiwoi Fish Market, Kolaka District. The method used is the interview and documentation method. Based on the results of the study, there were 31 species of demersal fish belonging to 12 families. The most dominant fish species were found from the Lutjanidae and Lethrinidae families. In general, the identification results of sustainable fisheries are quite good, such as fishing gear, types of environmentally friendly vessels, fishing locations and types of fish and size of fish caught. The type of boat most used by fishermen is the outboard motor. The most commonly used fishing gear is the fishing line.
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Mason, James, A. W. Newton, D. W. McKay i J. A. M. Kinnear. "Fisheries in the Orkney area". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 87, nr 1-2 (1985): 65–81. http://dx.doi.org/10.1017/s0269727000004164.

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SynopsisFishing has long played an important part in the economy of Orkney. Local vessels are all small, and fish predominantly inshore for shellfish. Demersal and pelagic fish are abundant in the offshore waters around Orkney, but these exposed waters can be fished only by large vessels from more distant ports, so that few fish are landed in the islands.Gadoids, especially haddock, cod and whiting, form the bulk of the demersal fish caught at Orkney. Stocks of all three are giving cause for concern, with declining spawning stock biomass and reduced recruitment. With the coming of processing, more local landing of demersal fish might occur. The closure of the herring fishery in 1977 was followed by a great expansion of mackerel fishing, but with the lifting of the ban west of 4CW in 1981, herring catches have once again become valuable. Because of fishing pressure, landings of both species are subject to quota restrictions.In recent years, the traditional fisheries for lobsters and crabs have been supplemented by a new fishery for scallops. Lobster stocks are now under some pressure. Conditions around Orkney appear suited to farming filter-feeding bivalve molluscs, and culture and marketing of Pacific oysters has started.
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Howard, F. G., D. W. McKay i A. W. Newton. "Fisheries of the Forth, Scotland". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 93, nr 3-4 (1987): 479–94. http://dx.doi.org/10.1017/s0269727000006898.

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SynopsisHistorical aspects of the Firth of Forth fisheries are described, and the present state of the stocks of exploited species is reviewed. The once-substantial pelagic fisheries have declined and now constitute only a minor component of the firth fisheries. Herring fisheries were based on spring spawning herring but the herring now caught in the firth are from stocks of overwintering juveniles of autumn spawning herring. Recent conservation measures have closed many of the firth grounds to herring and sprat fishing. The main demersal species caught are cod, haddock, whiting, plaice and lemon sole. Most landings are from catches made in the middle and outer firths and the North Sea. The demersal pair trawl is now the most important gear used in directed demersal fishing. The most important shellfish fishery is that for the Norway lobster, current landings being valued at £2·4 million. Over-exploitation resulted in a decline in the stocks in the late 1970s. They are now recovering. Recent studies suggest that population characteristics of Norway lobsters are influenced by the physical environment. The firth today is one of the most intensively exploited areas in Scotland for lobster and crabs. Other exploited shellfish include squid, winkles and mussels.
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Apriliani, Izza Mahdiana, Asep Agus Handaka Suryana, Ine Maulina i Rizka Zahra Utami. "Social and cultural characteristics in the development of small-scale fisheries: Case study of Cangkol Village, Cirebon, Indonesia". International Journal of Multidisciplinary Research and Growth Evaluation 4, nr 4 (2023): 842–46. http://dx.doi.org/10.54660/.ijmrge.2023.4.4.842-846.

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An overview of the condition of capture fisheries in an area is a tool for regional management parties in maintaining the sustainability of fishery resources in it. This research is focused on describing in general the area and conditions of capture fisheries in Kampung Cangkol, Cirebon. Residents in the Cangkol Village area have livelihoods as fishermen as much as 0.9% of the population. Within 5 years (2018–2022), the number of fishermen in Cangkol Village has tended to decrease. Nonetheless, the trend in numbers and production value of the catch of Cangkol Village fishermen tend to increase with the catch of demersal fish by the characteristics of sandy and muddy waters.
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Borges, Lisa, Alain F. Zuur, Emer Rogan i Rick Officer. "Modelling discard ogives from Irish demersal fisheries". ICES Journal of Marine Science 63, nr 6 (1.01.2006): 1086–95. http://dx.doi.org/10.1016/j.icesjms.2006.03.017.

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Abstract Annual discard ogives were estimated using generalized additive models (GAMs) for four demersal fish species: whiting, haddock, megrim, and plaice. The analysis was based on data collected on board commercial vessels and at Irish fishing ports from 1995 to 2003. For all species the most important factors influencing annual discard ogives were fleet (combination of gear, fishing ground, and targeted species), mean length of the catch and year, and, for megrim, also minimum landing size. The length at which fish are discarded has increased since 2000 for haddock, whiting, and plaice. In contrast, discarded length has decreased for megrim, accompanying a reduction in minimum landing size in 2000.
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Rozprawy doktorskie na temat "Demersal Fisheries"

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Dimech, Mark. "Conservation of the demersal fisheries resources within 25NM Maltese fisheries management zone". Thesis, Bangor University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496140.

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Ebil, Syazana. "Assessment of demersal fishery resources in Brunei Darussalam". Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/57704/.

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A problem commonly encountered in stock assessments of tropical marine resources in developing countries is data paucity, which invariably results from the lack of both human and economic capacity within the government to implement and maintain programmes for data collection and analysis. With special reference to the demersal fishery of Brunei Darussalam, this thesis examines approaches for extracting useful information from data-poor fisheries to assess the state of resources and inform fishery management actions. By using official fishery statistics, augmented by local ecological knowledge (LEK) obtained from fishers engaged in either the large-scale (LS) or small-scale (SS) fisheries in Brunei, changes in demersal fishery resources over the years were assessed. The sustainability of Brunei’s demersal capture fishery was evaluated in the face of its ongoing development and climate change. Using trophodynamic indicators such as mean trophic level (MTL), Fishing-in- Balance (FiB), trophic spectra (TS) and community structure analyses, LS fishery catches of Brunei between 2000 and 2009 revealed a deteriorating state of the coastal demersal ecosystem. Closer examination of the abundance of overall demersal finfish stocks, using the Catch-Per-Unit-Effort (CPUE) index – standardised for other factors not related to abundance – indicated a declining trend, even when total catches remained stationary, although trends in abundance of the different demersal fish families varied. This rapid significant change in recent years is further supported by fishers’ LEK on relative abundance of Brunei marine resources. The study on LEK has also revealed the ‘shifting baseline syndrome’ (SBS) among currently active fishers and their exploited populations, a phenomenon not previously reported for Brunei fisheries. Findings from the study are synthesised with other information, where a number of key issues and policy options are discussed, and recommendations for the management of the fishery are made. This thesis demonstrates that researchers in data-poor fisheries can utilise different assessment tools, given the resources at their disposal, to assist in the management of marine resources.
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Rice, Edward. "Rory lines : silver lining for seabirds in South Africa's demersal trawl fisheries". Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10902.

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Includes bibliographical references.
Seabird bycatch in commercial fisheries is one of the major factors causing decreases in many seabird populations. In trawl fisheries, high mortalities have been recorded as a result of seabirds being struck by trawl warps (the cables used to tow the trawl net). Tori (bird-scaring) lines have been used to decrease seabird mortality in some trawl fisheries by up to 90%. However, tori lines are not effective at reducing the number of birds that drift towards the trawl warps while feeding on factory discards alongside the vessel. The Albatross Task Force (ATF) helped to develop and test a new device, the Rory Line (RL), to be used in conjunction with tori lines, and designed to reduce warp strikes by placing a physical barrier between the scupper (where factory discards are released) and the danger zone (where the trawl warps enter the water) at the stern of the vessel. This study tests the efficacy of the RL at reducing the number of birds drifting into the danger zone and the number of birds being struck by the trawl warps.
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Isidro, Eduardo Jose Louca Florencio. "Biology and population dynamics of selected demersal fish species of the Azores Archipelago". Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307638.

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Koranteng, Kwame Abu. "The impacts of environmental forcing on the dynamics of demersal fishery resources of Ghana". Thesis, University of Warwick, 1998. http://wrap.warwick.ac.uk/34664/.

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The dynamics of demersal fish species assemblages and stocks on the continental shelf of Ghana, West Africa were investigated using data from trawl surveys conducted between 1963 and 1990, and in relation to marine environmental and nearshore forcing factors. Time series analysis was used to examine the dynamics of the marine environment. Classification and ordination methods were used to identify fish assemblages and to identify factors that determine assemblage formation and dynamics. The response of the identified assemblages to changes in the Ghanaian shelf ecosystem were assessed. Between 1964 and 1992, three distinct environmental time blocks (ETBs) in the continental shelf ecosystem off Ghana were recognised. In the first ETB (i. e. before 1972) sea surface and bottom temperatures were relatively high and salinity was low. The second ETB (1972 - 1982) was characterised by low temperatures, high but stable salinity, reduced rainfall and freshwater input into the sea. In the third ETB (1982 - 1992), the system bore a resemblance to the first block with rising temperatures and decreasing salinity. Six fish species assemblages were identified, namely the supra-thermocline sciaenid and lutjanid assemblages, two sparid assemblages (shallow and deep elements), the deep shelf assemblage and the upper slope assemblage. During ETB I and ETB3, the assemblages were easier to identify using ordination techniques, than during ETB2. Species diversity also decreased during ETB2 especially in waters between 10 and 50 m deep. This behaviour of the assemblagesis attributed to the increase in abundance of Balistes capriscus, a species that dominated the ecosystem for nearly 20 years from about 1971, and the observed environmental changes. The estimated density of demersal fish was higher in the upwelling season than in the thermocline season and decreased from 50 kg ha-1 in 1963-64 to 32.4 kg ha-1 in 1990. The density reached its lowest value of 22.5 kg ha-1 in the period between 1973 and 1977. The potential yield of the total demersal biomass (excluding triggerfish) is estimated to be 36,000 - 55,000 mt per annum. With landed catches exceeding 60,000 mt in some years, it is apparent that the resource is over-exploited. A number of policy options are discussed and recommendations for the management of the fishery are made.
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Walmsley, Sarah Ann. "The assessment and management of bycatch and discards in the South African demersal trawl fishery". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005071.

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Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.
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Currie, Jock. "Historical baselines and a century of change in the demersal fish assemblages on South Africa's Agulhas Bank". Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/27385.

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Accurate interpretation of recent variability observed in fish populations, species compositions, distribution ranges or ecological indicators, depends on knowledge of their past dynamics and historical states. The onset of systematic fisheries data collection typically lagged decades or even centuries behind modern fishing exploits. As a consequence, pre-disturbed reference points and descriptions of subsequent change are rarely available. A remarkably detailed set of historical trawl survey data from South Africa provided such a rare opportunity. Government-funded exploration of the Agulhas Bank fishery potential resulted in meticulously-documented trawl survey data from 1897-1904, when prior human impacts on those resources were negligible. Although they used less effective technology, the information recorded and methods used were similar to modern surveys. This thesis investigated change in demersal fish fauna of the Agulhas Bank and documents comparisons between historical trawl surveys and modern re-enactments at the same locations. In comparing trawl survey catches over multiple decades or among different periods, unquantified changes in fishing power pose a key challenge. The shape, size, materials, mesh sizes and speed at which trawl nets are dragged, interact with the behaviour, size and shape of fish, influencing fishing performance. To accurately compare current catch rates with those of historical trawl surveys, the same trawl gear and methods were carefully replicated in repeat surveys at three sites. An investigation of literature and photographs of the original vessel and equipment were conducted to support the construction of a replica 'Granton' otter trawl net. The net was composed of Manila hemp with a headline length of 27 m (90 ft) and was attached to flat wooden trawl boards. The historical towing speed was estimated as 1.34 m s⁻¹ (2.6 knots). Three parts of the shallow Agulhas Bank that were surveyed 111 years prior, were re-surveyed in 2015. Species composition was contrasted between the historical and re-survey periods by way of unconstrained ordination, permutational multivariate analysis of variance and tests of the homogeneity of multivariate group dispersions. Taxa discerning between periods were identified with similarity percentage analyses. Changes of standardised catch between periods were tested for 27 taxa, using a non-parametric bootstrap approach. Proportions among size-classes, recorded for three taxa, were tested using Fisher's exact test. Results revealed a substantially transformed demersal catch assemblage, where the period effect explained almost half of the measured variance among samples. These changes included the disappearance or heavy depletion of kob (Argyrosomus spp., absent in re-surveys), panga (Pterogymnus laniarius; 2.4% of historical catch abundance) and east coast sole (Austroglossus pectoralis; 4.6% of historical catch abundance), which had jointly contributed 70-84% of historical catch composition. Average re-survey catches were largely made up of gurnards (Chelidonichthys spp.; 3 792% of historical abundance), horse mackerel (Trachurus trachurus; 4 738% of historical abundance), spiny dogfish (Squalus spp.; 3 121% of historical abundance), hake (Merluccius capensis; 558% of historical abundance) and white sea catfish (Galeichthys feliceps; 13 863% of historical abundance). Analysis of available length information confirmed the expectation that fish sizes (specifically M. capensis and A. pectoralis) had declined. This implies that comparisons by weight would be more severe for declined abundances and less severe for those that increased, relative to contrasts of numerical abundance. Habitat preferences as well as geographic and depth distribution appeared to separate the taxa that increased from those that declined. These factors, together with reproductive and growth characteristics, as well as indirect trophic impacts, likely shaped the responses of demersal fauna to fishing and other human impacts during the 111 years between trawl surveys. An assessment of distribution changes of 44 common demersal taxa was undertaken. These analyses were restricted to the last 30 years of trawl survey data as the units and spatio-temporal resolution of prior data were incompatible. Standardised catches were used from annual spring and autumn south coast trawl surveys conducted by the government fisheries department. Geostatistical delta-generalised linear mixed models were used to predict species distribution functions, which were used to calculate annual estimates of latitude/longitude centres of gravity and effective areas occupied by each population. Average trends over the study period (1986-2016) were assessed using a Bayesian state-space model. Of nine species found to have a trend in average location, six moved westward or south-westward, while three moved eastward or north-eastward. Two species showed a trend of contracting spatial extent and one showed an expansion. Across the entire assemblage combined, there was a significant contraction in extent and a westward shift in average location. These assemblage-wide average trends are interpreted to be driven by climate forcing. Fishing impacts are expected to have contributed to the eastward movement in centre of gravity for kob, lesser sandshark (Rhinobatos annulatus) and white stumpnose (Rhabdosargus globiceps). Interpretation of these distribution shifts is hampered by a lack of knowledge on subsurface hydrographic trends on the Agulhas Bank, which is identified as a research priority. My research revealed substantial change in demersal fish communities on South Africa's Agulhas Bank and adds novel insight to the history underlying current states of demersal ecosystems. Valuable additions include a) documentation of the extent to which demersal assemblages have transformed during the last century at three representative inshore sites; b) estimates of current abundances relative to pre-disturbed baselines at those sites, which c) highlights drastic local depletion for certain taxa and d) reveals substantial abundance increases of certain species during the post-industrial fishing period; e) novel evidence of distribution trends in south coast demersal species; and f) identification of trends in the average distribution of the demersal fish assemblage, suspected to be climate-forced. Long-term comparisons, using minimally-disturbed baselines, revealed drastic transformation of the fish assemblage during a century of industrialisation, which points to trawling-induced alteration of benthic habitats and substantial changes in ecosystem structure. Besides the provision of novel historical context for current and future studies and decision-making, this work counters the erosive nature of shifting baselines in South Africa's marine environment.
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Darwall, William Robert Thomas. "Spatial patterns and trophic modelling within the Lake Malawi demersal fish community : conservation and fisheries applications". Thesis, University of Hull, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402706.

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Pembroke, Innes James. "Reducing environmental impacts of fishing : An economic analysis of discarding and technical measures in demersal fisheries". Thesis, University of Portsmouth, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516155.

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Fishing gears, and especially those that are towed across the seabed, can impose a number of impacts on the marine environment. The long term implications of many of these impacts are poorly understood and often hard to quantify from both the ecological and economic perspective (L0kkeborg, 2004). At a global level the general trend towards ecosystem based management (FAO, 2003; Pikitch et al .. 2004) and adopting the precautionary principal (FAO, 1995b, 1996) implies these impacts should be reduced. Within Europe, the focus of management has primarily been on reducing the level of commercially important species being caught incidentally ("bycatch") and subsequently discarded. These reductions have mainly been pursued through the application of restrictions on the type of fishing gear that can be used (generally termed "technical measures"). However, hard management constraints such as technical measures tend to impose increased costs on fishers, primarily through reduced productivity. These create incentives to mitigate the effectiveness of the measures, and may ultimately result in a failure to achieve the management objective. Despite ongoing attempts to reduce these impacts, bycatch and discarding rates are estimated to be in the range of 20% to 60% of catch weight for European fisheries (European Commission, 2007b). This study investigates the importance of individual environmental impacts within the context of European demersal trawl fisheries and then assesses the effects of attempting to reduce one of these impacts, that of bycatch and discarding, through the application of gear based technical measures. Priorities for the reduction of impacts are quantified at the stakeholder group level using the Analytic Hierarchy Process (AHP). The results indicate that Europe's historical focus on reducing primarily commercial discards with technical measures needs to be broadened to account for other non-commercial impacts. The effects of attempting to reduce bycatch and discarding through the application of gear based technical measures are then considered using two case studies. Ex post assessments are undertaken on two fisheries; the UK East coast Crangon crangon (Brown shrimp) fishery and the Belgian large beam trawl fishery. In both instances vessel level productivity was observed to have fallen as a result of taking up bycatch reduction measures with productivity effects estimated to range between -14% and -23%. On the basis of these findings, a review was undertaken of alternative measures that may better account for the set of incentives fishers face. Whilst not yet widely applied in the context of fisheries, their potential tb simultaneously improve both economic performance and resource sustainability means they have been receiving increasing attention (Grafton et al., 2006a). Such measures appear to provide a potential solution to the main issues surrounding command and control type measures and are likely to have application when attempting to reduce discards in fisheries.
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Knuth, Friedrich Alexander. "Exploring the geospatial relationships between demersal fish and seafloor morphometrics along the southeast Atlantic continental shelf". Thesis, College of Charleston, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1585544.

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Marine Protected Areas (MPAs) are successful place-based management tools in protecting Essential Fish Habitat (EFH) from commercial and recreational fishing pressures. In the southeast Atlantic, the morphometric environment of the seafloor has been found to be a control on Essential Fish Habitat (EFH) (Sedberry and Van Dolah 1984). To this end, modern methods of acoustic data acquisition and morphometric analysis of the seascape are promising oceanographic techniques for identifying and delineating EFH. In July, 2013, the NOAA Ship Pisces collected bathymetric, backscatter and water column data for potential habitat sites along the U.S. Southeast Atlantic continental shelf. A total of 205 km2 of seafloor were mapped between Mayport, FL and Wilmington, NC, using the SIMRAD ME70 multibeam echosounder system. In addition, a total of n = 7410 fish presences were recorded within the water column, using the SIMRAD EK 60 split-beam echosounder system. These data were processed in CARIS HIPS, QPS Fledermaus, MATLAB and Echoview. This study provides a morphometric characterization and quantitative assessment of fish present within each survey site and identifies features of the bathymetry that help explain the presence of demersal fish. A total of 106 unique maps were created, illustrating seafloor morphometrics and fish distributions across the seascape. In ArcGIS, 14 morphometrics were generated as candidate explanatory variables for fish abundances in small (5-12 cm), medium (12-29 cm) and large (>29 cm) size classes. We explored fish-seascape interactions at two spatial scales in the GIS using a site-wide and 50 x 50 m grid scale. At the site- wide scale, X¯ Slope (R2 = 0.97), X¯ Slope of Slope (R2 = 0.90) and σ Depth (R2 = 0.87) provided the strongest explanatory power in a bivariate analysis and may be used to help identify EFH at a coarse scale. At a 50 x 50 m grid scale, X¯ Slope, X¯ Slope of Slope and X¯ Backscatter emerged as the strongest contributing variables, when combined in a multivariate analysis. Overall, multivariate model R2 values were low and not predictive, but allow for the identification of variables contributing to the characterization of fish-seascape interactions at a finer scale.

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Książki na temat "Demersal Fisheries"

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Merrett, N. R. Deep-sea demersal fish and fisheries. London: Chapman & Hall, 1997.

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Bay of Bengal Programme. Development of Small-Scale Fisheries., red. The demersal fisheries of Sri Lanka. Madras: Development of Small-Scale Fisheries in the Bay of Bengal, 1985.

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Sivasubramaniam, K. The demersal fisheries of Sri Lanka. Rome: Food and Agriculture Organization, 1986.

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F, Melvin Edward, i Washington Sea Grant Program, red. Solutions to seabird bycatch in Alaska's demersal longline fisheries. Seattle, WA: Washington Sea Grant Program, University of Washington, 2001.

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Sample, Terrance M. Demersal fish and shellfish resources of Norton Sound and adjacent water during 1979. Seattle, Wash: National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Northwest and Alaska Fisheries Center, 1985.

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Newton, Gina. Deep-sea demersal fisheries of the Great Australian Bight: A multivessel trawl Survey. Canberra: A.G.P.S., 1991.

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Arancibia, Hugo. Ecosystem based approach: A comparative assessment of the institutional response in fisheries management within APEC economies : the case of demersal fisheries (Phase 1). [Singapore: APEC Secretariat], 2006.

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Manuel, Haimovici, i Universidade de São Paulo. Instituto Oceanográfico., red. Prospecção pesqueira de espécies demersais com rede de arrasto-de-fundo na Região Sudeste-Sul do Brasil. [São Paulo: Instituto Oceanográfico-USP, 2008.

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Haimovici, Manuel, i Antônio Olinto Ávila-da-Silva. Prospecção pesqueira de espécies demersais com espinhel-de-fundo na zona econômica exclusiva da Região Sudeste-Sul do Brasil. São Paulo: Instituto Oceanográfico-USP, 2004.

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Bernardes, Roberto Ávila. Prospecção pesqueira de recursos demersais com armadilhas e pargueiras na Zona Econômica Exclusiva da Região Sudeste-Sul do Brasil. São Paulo: Instituto Oceanográfico-USP, 2005.

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Części książek na temat "Demersal Fisheries"

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Arnason, R. "A Numerical Model of the Icelandic Demersal Fisheries". W Operations Research and Management in Fishing, 123–51. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-011-3280-0_10.

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Piñeiro-Corbeira, Cristina, Sara Barrientos, Rodolfo Barreiro, Shankar Aswani, José J. Pascual-Fernández i Raquel De la Cruz-Modino. "Can Local Knowledge of Small-Scale Fishers Be Used to Monitor and Assess Changes in Marine Ecosystems in a European Context?" W Human-Nature Interactions, 299–314. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-01980-7_24.

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Significance StatementIn the last decades, many coastal areas have observed dramatic changes in marine ecosystems, due to anthropogenic and environmental alterations. The general absence of long-term data sets in the marine environment and, more specifically, on benthic and demersal communities represents a severe issue for management and conservation. We propose to incorporate the small-scale fishers’ knowledge and science for better policy recommendations, both in terms of fisheries optimization and resource conservation. Based on two different cases of study with diverse ecosystems, we explore the combination of quantitative and qualitative tools, and participative techniques used to incorporate fishers’ local ecological knowledge. The results highlight fishers’ capacity to identify coastal and marine landscapes resources and changes, reinforcing and complementing the scientific assessment.
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Beverton, Raymond J. H., i Sidney J. Holt. "Requirements for the Regulation of the North Sea Demersal Fisheries". W On the Dynamics of Exploited Fish Populations, 419–36. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2106-4_20.

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Mackinson, Steven, Michael Park i Barrie Deas. "Does Slow-Burn Collaboration Deliver Results? Towards Collaborative Development of Multi-Annual Multi-Species Management Plans in North Sea Mixed Demersal Fisheries". W Collaborative Research in Fisheries, 179–91. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-26784-1_11.

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Lehuta, Sigrid, Youen Vermard i Paul Marchal. "A Spatial Model of the Mixed Demersal Fisheries in the Eastern Channel". W Marine Productivity: Perturbations and Resilience of Socio-ecosystems, 187–95. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13878-7_20.

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Sabatella, Rosaria Felicita, Paolo Accadia, Maria Cozzolino, Monica Gambino, Loretta Malvarosa i Evelina Carmen Sabatella. "Socio-Economic Impacts of the Common Fisheries Policy on South and Central Tyrrhenian Sea (GSA 10) Demersal Trawl Fisheries". W New Metropolitan Perspectives, 143–54. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-52869-0_12.

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Mullasseri, Sileesh, i Madhusoodana B. Kurup. "Taxonomic and Phylogenetic Indices of Species Assemblages in the Deep-Sea Demersal Ichthyofauna of the South-eastern Arabian Sea: Simple Measures of Diversity for Marine Ecosystem-Based Management". W Impact of Climate Change on Hydrological Cycle, Ecosystem, Fisheries and Food Security, 341–51. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003299769-33.

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Brander, K. "Demersal Species Fisheries". W Encyclopedia of Ocean Sciences, 718–25. Elsevier, 2001. http://dx.doi.org/10.1006/rwos.2001.0449.

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Brander, K. "Demersal Species Fisheries". W Encyclopedia of Ocean Sciences, 90–97. Elsevier, 2001. http://dx.doi.org/10.1016/b978-012374473-9.00449-5.

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Longhurst, Alan R., i Daniel Pauly. "Species Assemblages in Tropical Demersal Fisheries". W Ecology of Tropical Oceans, 145–83. Elsevier, 1987. http://dx.doi.org/10.1016/b978-0-12-455562-4.50009-4.

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Streszczenia konferencji na temat "Demersal Fisheries"

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Mueter, F. J., i B. L. Norcross. "A Multivariate Approach to Monitoring Changes in Species Composition of a Demersal Fish Community". W Ecosystem Approaches for Fisheries Management. Alaska Sea Grant, University of Alaska Fairbanks, 1999. http://dx.doi.org/10.4027/eafm.1999.42.

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Ivanovic´, Ana, Jianfeng Zhu, Richard Neilson i Finbarr O’Neill. "Physical Impact of a Roller Clump on the Seabed". W ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57978.

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The envionmental impact of towed demersal gears on benthic communities has been of concern for the last couple of decades. Knowledge of the response of benthic habitats to impacts from fishing gears is of great importance to the ecosystem and the long-term management of sustainable fisheries. An on-going EU project, DEGREE (DEvelopment of Fishing Gears with Reduced Effects on the Environment), addresses this concern by focusing on quantifying the environmental and ecological impacts of fishing, developing fishing gears with reduced environmental impact, and assessing the socio-economic consequences of these changes. This paper focuses primarily on the modelling of the interaction between a gear component, the roller clump of a twin trawl, and the seabed in terms of penetration and disturbance of the seabed. A finite element model of this interface has been developed and is able to predict the penetration depth, sediment displacement and the pressure field associated with each gear component. In order to verify these predictions, sea trials have taken place over a range of sediment types at depths accessible to scientific divers using SCUBA diving techniques. This has allowed sampling of the seabed and profiling of the disturbed region for comparison with the model results. Good agreement is found.
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Raporty organizacyjne na temat "Demersal Fisheries"

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van Overzee, H. M. J. Factsheet: Sampling demersal active fisheries through self-sampling (DEMACT2). Stichting Wageningen Research, Centre for Fisheries Research (CVO), 2023. http://dx.doi.org/10.18174/634040.

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van Overzee, H. M. J. Factsheet: Sampling demersal passive fisheries through observer trips (DEMPAS). Stichting Wageningen Research, Centre for Fisheries Research (CVO), 2023. http://dx.doi.org/10.18174/634041.

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van Overzee, H. M. J. Factsheet: Sampling demersal active fisheries through observer trips (DEMACT1). Stichting Wageningen Research, Centre for Fisheries Research (CVO), 2023. http://dx.doi.org/10.18174/634039.

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Hintzen, Niels, Esther Beukhof, Thomas Brunel, Annemiek Eweg, Katell Hamon, Susan de Koning, Arie Mol i Nathalie Steins. Exploring potential ecological impacts of different scenarios for spatial closures and fleet decommissioning for Dutch North Sea demersal fisheries. IJmuiden: Wageningen Marine Research, 2021. http://dx.doi.org/10.18174/544217.

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Hintzen, Niels, i Ulrika Beier. Predicting benthic fauna biomass in the Voordelta under different hypothetical fisheries regimes : Could an expected increase in benthic fauna have occurred within an area protected from demersal trawling if shrimp fisheries should not have increased? IJmuiden: Wageningen Marine Research, 2019. http://dx.doi.org/10.18174/499289.

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