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K.h Nedreaas - One of the best experts on this subject based on the ideXlab platform.
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Relative selectivity of Greenland halibut (Reinhardtius hippoglossoides, Walbaum) by trawls, longlines and Gillnets
Fisheries Research, 1999Co-Authors: Irene Huse, A.c Gundersen, K.h NedreaasAbstract:Abstract Selectivity parameters for Greenland halibut ( Reinhardtius hippoglossoides , Walbaum) were calculated from trawl and gillnet catches in the Norwegian scientific fisheries for greenland halibut. Within the chosen individual areas and seasons, our data show no trend in length distribution with depth. A trouser-trawl selectivity experiment gave an L 50 at 42 cm in a 135 mm codends. A selectivity analysis of the Gillnets using a log normal model showed maximum probability of retention for lengths of 46.8–73.5 cm for 140–220 mm stretched meshes. By using expected catch proportions and life history parameters, the selectivity in longline and trawl was shown to be bell-shaped, both gears losing both the smallest and largest fish. Calculated estimated life-history parameters were biased by sampling gears, giving slower growth and larger L ∞ for females caught in Gillnets. The maturation length ( M 50 ) of female Greenland halibut was largest in trawl catches, smallest for gillnet catches. The sex ratio in the gillnet catches was shown to be a direct function of mesh size. These analyses will provide a better understanding of possible sampling bias when sampling a stock by means of only one type of gear.
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Performance and Biological Implications of a Multi-gear Fishery for Greenland Halibut (Reinhardtius hippoglossoides)
Journal of Northwest Atlantic Fishery Science, 1996Co-Authors: K.h Nedreaas, A V Soldal, A BjordalAbstract:Simultaneous full-scale fishing operations using bottom trawl, gillnet and longline for Greenland halibut (Reinhardtius hippoglossoides, Walbaum) were performed in the Barents Sea (ICES Divisions IIa and IIb) for two weeks in October 1992. The mesh size of the trawl codend was 135 mm, and that of the Gillnets 220 mm. Additionally, seven gillnet fleets of 180 mm mesh size were set for selectivity comparison. The catch rates and the length distributions of the Greenland halibut in the catches taken by trawl, longline and gillnet were different. Gillnets almost exclusively caught fish between 60 and 70 cm, mostly mature females (about 90%). The size distribution taken by longline was wider than that taken by gillnet. Two thirds of the longline catches were females, and the proportion of immature individuals was larger (14–30%) than in the gillnet catches. The trawls, however, caught large amounts of fish between 40 and 60 cm, consisting of almost equal amounts of males and females, and 30–40% immature fish. Gear-specific selection properties were the main reasons for the observed differences. Yield-per-recruit and spawning-stock-biomass-per-recruit analyses showed that fixed gears captured proportionally fewer immature fish, and thus indicated they would provide greater spawning biomass and yield-per-recruit than would trawl gear, for an equivalent reference fishing mortality rate.
Bruno Welter Giraldes - One of the best experts on this subject based on the ideXlab platform.
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artisanal fishing of spiny lobsters with Gillnets a significant anthropic impact on tropical reef ecosystem
Global Ecology and Conservation, 2015Co-Authors: Bruno Welter Giraldes, Angela Zacaron Silva, Fabio M Correa, David SmythAbstract:Abstract Artisanal fishing activity with Gillnets to capture the spiny lobster is a common practice along the coastal reefs of Brazil. This research aims to understand the impact that this artisanal fishing practice is having on the coastal reef systems analysing its associated fauna (bycatch) and the stock of the target species Panulirus echinatus . The study compared an area which was subjected to intense gillnet fishing against one were the practice was absent. The analysis of target species using nocturnal visual census demonstrated a significantly higher number of P. echinatus at the site where gillnet use was virtually absent within three sampled habitats, fringe, cave and soft bottom. The analysis of bycatch species from artisanal fishermen’s gillnet landings recorded 4 lobster species and 10 crab species. These decapod species play an important ecological role as detritivores, herbivorous and first consumers within the reef ecosystem as well as being natural prey items for several reef fishes. The study concludes that this non-discriminatory fishing technique impacts directly on populations of P. echinatus, P. argus and P. laevicauda as well as other lobster and crab species which in-turn indirectly affects the ecological role of the tropical coastal reefs of Brazil.
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Artisanal fishing of spiny lobsters with Gillnets — A significant anthropic impact on tropical reef ecosystem
Elsevier, 2015Co-Authors: Bruno Welter Giraldes, Angela Zacaron Silva, Fabio M Correa, David M. SmythAbstract:Artisanal fishing activity with Gillnets to capture the spiny lobster is a common practice along the coastal reefs of Brazil. This research aims to understand the impact that this artisanal fishing practice is having on the coastal reef systems analysing its associated fauna (bycatch) and the stock of the target species Panulirus echinatus. The study compared an area which was subjected to intense gillnet fishing against one were the practice was absent. The analysis of target species using nocturnal visual census demonstrated a significantly higher number of P. echinatus at the site where gillnet use was virtually absent within three sampled habitats, fringe, cave and soft bottom. The analysis of bycatch species from artisanal fishermen’s gillnet landings recorded 4 lobster species and 10 crab species. These decapod species play an important ecological role as detritivores, herbivorous and first consumers within the reef ecosystem as well as being natural prey items for several reef fishes. The study concludes that this non-discriminatory fishing technique impacts directly on populations of P. echinatus, P. argus and P. laevicauda as well as other lobster and crab species which in-turn indirectly affects the ecological role of the tropical coastal reefs of Brazil
Jon Helge Volstad - One of the best experts on this subject based on the ideXlab platform.
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spatial and temporal variations in seabird bycatch incidental bycatch in the norwegian coastal gillnet fishery
PLOS ONE, 2019Co-Authors: Kim Magnus Baerum, Tycho Ankernilssen, Signe Christensendalsgaard, Kirstin Fangel, T Williams, Jon Helge VolstadAbstract:The general decline of seabird populations worldwide raises large concerns. Although multiple factors are interacting to cause the observed trends, increased mortality from incidental bycatch in fisheries has proven to be important for many species. However, the bulk of published knowledge is derived from longline fisheries, whereas bycatch in gillnet fisheries is less studied and even overlooked in some areas. We present seabird bycatch data from a 10-year time-series of fishery data from the large fleet of small-vessels fishing with Gillnets along the Norwegian coast—a large area and fishery with no prior estimates of seabird bycatch. In general, we document high rates of incidental bycatch (averaging 0.0023 seabirds/net, or approximately 0.08 seabirds/fishing trip). This results in an estimated annual bycatch between 1580 and 11500 (95% CI) birds in this fishery. There was a surprisingly high percentage (43%) of surface-feeding seabirds in the bycatch, with northern fulmar being the most common species. Among the diving seabirds caught, common guillemot was most numerous. Our findings suggest that coastal gillnet fisheries represent a more general threat to a wider range of seabird populations, as opposed to longline fisheries where surface-feeding seabird species seem to dominate the bycatch. The bycatch estimates for the Norwegian gillnet-fishery varied in time, between areas, and with fishing depth and distance from the coast, but we found no clear trends in relation to the type of Gillnets used. The results enabled us to identify important spatio-temporal trends in the seabird bycatch, which can allow for the development and implementation of more specific mitigation measures. While specific time closures might be an efficient option to reduce bycatch for diving seabirds, measures such as gear modification and reduction in release of wastewater during fishing operation are probably a more effective mitigation approach for reducing bycatch of surface-feeding seabirds.
Timothy B. Werner - One of the best experts on this subject based on the ideXlab platform.
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marine mammal bycatch in gillnet and other entangling net fisheries 1990 to 2011
Endangered Species Research, 2013Co-Authors: Randall R. Reeves, Kate Mcclellan, Timothy B. WernerAbstract:Since the 1970s the role of fishery bycatch as a factor reducing, or limiting the recov- ery of, marine mammal populations has been increasingly recognized. The proceedings of a 1990 International Whaling Commission symposium and workshop summarized fishery and bycatch data by region, fishery, and species, and estimated the significance of the 'impacts' of bycatch in passive gear on all cetacean species and subspecies or geographically defined populations. A global review of pinniped bycatch in 1991 concluded that incidental mortality in passive gear had contributed to declines of several species and populations. Here we update the information on cetacean gillnet bycatch, assess bycatch data on marine mammals other than cetaceans (i.e. pin- nipeds, sirenians, and 2 otter species), determine where important data gaps exist, and identify species and populations known or likely to be at high risk from bycatch in Gillnets. We found that at least 75% of odontocete species, 64% of mysticetes, 66% of pinnipeds, and all sirenians and marine mustelids have been recorded as gillnet bycatch over the past 20-plus years. Cetacean bycatch information in some areas has improved, facilitating our ability to identify species and populations at high risk, although major gaps remain. Understanding of the scale of pinniped and sirenian bycatch has also improved, but this bycatch remains poorly documented, especially at the population level. This study reveals how little is known about marine mammal bycatch in Gillnets in much of the world. Even as other significant threats to marine mammals have become better documented and understood, bycatch remains a critical issue demanding urgent attention if there is to be any hope of preventing further losses of marine mammal diversity and abundance, and of protecting, or restoring, ecological health.
David Smyth - One of the best experts on this subject based on the ideXlab platform.
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artisanal fishing of spiny lobsters with Gillnets a significant anthropic impact on tropical reef ecosystem
Global Ecology and Conservation, 2015Co-Authors: Bruno Welter Giraldes, Angela Zacaron Silva, Fabio M Correa, David SmythAbstract:Abstract Artisanal fishing activity with Gillnets to capture the spiny lobster is a common practice along the coastal reefs of Brazil. This research aims to understand the impact that this artisanal fishing practice is having on the coastal reef systems analysing its associated fauna (bycatch) and the stock of the target species Panulirus echinatus . The study compared an area which was subjected to intense gillnet fishing against one were the practice was absent. The analysis of target species using nocturnal visual census demonstrated a significantly higher number of P. echinatus at the site where gillnet use was virtually absent within three sampled habitats, fringe, cave and soft bottom. The analysis of bycatch species from artisanal fishermen’s gillnet landings recorded 4 lobster species and 10 crab species. These decapod species play an important ecological role as detritivores, herbivorous and first consumers within the reef ecosystem as well as being natural prey items for several reef fishes. The study concludes that this non-discriminatory fishing technique impacts directly on populations of P. echinatus, P. argus and P. laevicauda as well as other lobster and crab species which in-turn indirectly affects the ecological role of the tropical coastal reefs of Brazil.