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1.
We integrated satellite-tracking data from black-footed albatrosses (Phoebastria nigripes; n = 7) and Laysan albatrosses captured in Alaska (Phoebastria immutabilis; n = 18) with data on fishing effort and distribution from commercial fisheries in the North Pacific in order to assess potential risk from bycatch. Albatrosses were satellite-tagged at-sea in the Central Aleutian Islands, Alaska, and tracked during the post-breeding season, July-October 2005 and 2006. In Alaskan waters, fishing effort occurred almost exclusively within continental shelf and slope waters. Potential fishery interaction for black-footed albatrosses, which most often frequented shelf-slope waters, was greatest with sablefish (Anoplopoma fimbria) longline and pot fisheries and with the Pacific halibut (Hippoglossus stenolepsis) longline fishery. In contrast, Laysan albatrosses spent as much time over oceanic waters beyond the continental shelf and slope, thereby overlapping less with fisheries in Alaska than black-footed albatrosses. Regionally, Laysan albatrosses had the greatest potential fishery interaction with the Atka mackerel (Pleurogrammus monopterygius) trawl fishery in the Western Aleutian Islands and the sablefish pot fishery in the Central Aleutian Islands. Black-footed albatrosses ranged further beyond Alaskan waters than Laysan albatrosses, overlapping west coast Canada fisheries and pelagic longline fisheries in the subarctic transition domain; Laysan albatrosses remained north of these pelagic fisheries. Due to inter-specific differences in oceanic distribution and habitat use, the overlap of fisheries with the post-breeding distribution of black-footed albatrosses is greater than that for Laysan albatrosses, highlighting inter-specific differences in potential vulnerability to bycatch and risk of population-level impacts from fisheries. 相似文献
2.
The flesh-footed shearwater (Puffinus carneipes) is a medium-sized seabird (ca. 700 g) that is incidentally killed during longline fishing operations. We examined the levels of bycatch in Australia’s Eastern Tuna and Billfish Fishery and developed a model to examine the impact of this fishery on the eastern Australian population of flesh-footed shearwaters, which breeds at only one site, Lord Howe Island. Observed bycatch rates for flesh-footed shearwaters were 0.378 birds/1000 hooks for night sets, and 0.945 birds/1000 hooks for day sets. The mean number of birds killed from 1998 to 2002 was estimated to be 1794-4486 birds per year, with the estimated total killed over this period ranging from 8972 to 18,490 birds. Models incorporating both density-independent and density-dependent scenarios were applied to levels of bycatch representative of that observed in the fishery. Density-independent scenarios showed that fishing mortality levels caused declines in the majority of simulated populations. In contrast, density-dependent scenarios produced populations that were more resilient to fishing mortalities. Although some modelling scenarios led to population growth, under most stochastic simulations median population halving and quasi-extinction times were less than 55 and 120 years, respectively. We conclude that the level of bycatch observed in the fishery is most likely unsustainable and threatens the survival of the Lord Howe Island population. This situation can be improved only with the development and implementation of mitigation measures that will halt or greatly reduce the level of bycatch currently observed. Improved knowledge on a range of demographic parameters for the species, combined with a clearer idea of the at-sea distribution of breeding and non-breeding shearwaters, will greatly assist in improving understanding and the management of this population. 相似文献
3.
Albatross movements and foraging grounds during the post-breeding dispersal are poorly understood, despite their important conservation implications. We tracked four female black-footed albatrosses (Phoebastria nigripes) for 100 days during their summer (July-September, 1997-1999) post-breeding dispersal off California, and compared their movements to the distribution of fishing effort from the Japanese Eastern Pacific Ocean (EPO) longline fishery. The tracked birds foraged largely along the transition zone between the California Current and the Central Pacific Gyre, and spent 25, 24, and 51% of their time at sea within the 200-mile exclusive economic zones (EEZs) of the USA and Mexico, and the high seas (international waters) respectively. The satellite-tracked birds occupied subtropical waters (18-20 °C) targeted by longline fisheries for tuna (Thunnus spp.) and broad-bill swordfish (Xiphias gladius), and ranged disproportionately farther during daylight hours, when tuna fisheries operate. The available data suggest that albatrosses overlap temporally and spatially with longline fisheries in the northeast Pacific Ocean. However, this research cannot directly evaluate whether black-footed albatross bycatch occurs in these fisheries. The coarse temporal (monthly) and spatial (1°×1°) resolution of the fisheries data, and the dynamic nature of the fishing effort inhibited a fine-scale analysis of albatross overlap with longline fisheries. While we documented substantial spatial overlap between albatross distributions and the Japanese EPO longline fishing effort during the 1980s, we found no co-occurrence during the 1990s. This study illustrates the value of satellite telemetry to assess national conservation responsibilities, and to identify potential interactions of protected species with fisheries not currently monitored by observer programs. Furthermore, our results underscore the need to exercise caution when interpreting satellite telemetry data for conservation purposes, because of the highly dynamic nature of pelagic fisheries. 相似文献
4.
The endangered Tristan albatross Diomedea dabbenena is restricted to Gough and Inaccessible Islands. The species is killed as bycatch by longline fisheries in the South Atlantic, but the impact of this mortality is unknown. We satellite tracked 38 breeding Tristan albatrosses and assessed the seasonal and annual at-sea distribution of these birds in relation to reported pelagic longline fishing effort. These birds ranged across the South Atlantic from 50°W to 15°E with most (97%) daytime satellite fixes between latitudes 30°S and 45°S. Considerable fishing effort occurred within the same latitudes. Although there was no correlation between their at-sea distributions, there was a broad overlap between birds and fishing effort. Estimated bycatch rates for Tristan albatross and other Diomedea species in the South Atlantic, and the spatio-temporal overlap between birds and hooks, yield a predicted annual mortality of 471-554 birds, sufficient to cause population decreases of 3.6-4.3% per year. An index of bird × hook interactions (proportional density of birds multiplied by number of hooks by decadal period for each 5° square of longitude and latitude) indicated that 47% of annual interactions occurred in areas around Gough Island, and 11% and 15% of interactions in areas of the west and east Atlantic, respectively. There were also within seasonal differences in the key areas of overlap. The fishing fleets of Taiwan and Japan are likely to be responsible for most interactions based upon the reported magnitude of effort expended in the South Atlantic by these fleets. Ensuring that licensed fishing vessels within the Tristan da Cunha Exclusive Economic Zone (EEZ) operate using best-practise mitigation measures and with fisheries observer programs, could reduce the potential bycatch mortality of breeding Tristan albatrosses in this region by nearly one third. Thorough implementation of international agreements is required in areas of the high seas where most remaining interactions are predicted to occur. 相似文献
5.
A demersal longline fishery for Patagonian toothfish (Dissostichus eleginoides) that commenced off the Prince Edward Islands during 1996 has killed significant proportions of locally breeding albatrosses and petrels. As one of a suite of mitigation measures, we tested the efficacy of a Mustad underwater setting funnel to reduce incidental mortality of seabirds. The funnel, which deploys the longline 1-2 m beneath the sea surface, was used on 52% of 1714 sets (total effort 5.12 million hooks) over a 2-year period. Used in conjunction with a bird-scaring line, overall seabird bycatch rate was low (0.022 birds per 1000 hooks), and was dominated by white-chinned petrels (Procellaria aequinoctialis) (88% of the 114 birds killed). Bycatch rate was three times lower when the funnel was used both by day and at night. Daytime catch rates with the funnel were less than those attained during night sets without the funnel. In conjunction with other mitigation measures, underwater setting offers a significant reduction in seabird mortality in this fishery and could increase fishing efficiency by allowing daytime setting. However, small numbers of albatrosses were caught during daytime sets with the funnel, and its use for daytime sets should be closely monitored. 相似文献
6.
Bird mortality in fishing gear is a global conservation issue and it is recognised that bycatch in industrial longline and trawl fisheries threatens several seabird species. Little is known however about the effects of bycatch in small-scale gillnet fisheries on bird populations. Here we review 30 studies reporting bird bycatch in coastal gillnet fisheries in the Baltic Sea and the North Sea region in order to assess the magnitude of this problem and potential effects on bird populations. All species of diving birds that occur in the study region, including divers (loons), grebes, sea ducks, diving ducks, auks and cormorants, have been reported as dying in fishing nets. The cumulative bycatch estimate extracted from several localized studies providing such information, suggests that about 90,000 birds die in fishing nets annually, a number that is almost certainly a substantial underestimate. We conclude that it is likely that between 100,000 and 200,000 waterbirds are killed per year. Geographic and temporal patterns of bycatch generally matched species distribution and periods of presence. Also, bycatch rates varied depending on species’ foraging technique and were influenced by net parameters and fishing depth. To evaluate effects of additive mortality on bird populations, we applied the Potential Biological Removal (PBR) concept to three species with the most extensive bycatch information. Agreeing with PBR assumptions we conclude that bycatch is a matter of concern for at least two of the three assessed species. We suggest that bycatch research in Europe and beyond should aim at unification of principles for bycatch assessment, setting new standards for the monitoring of waterbird populations so that vital rates and mortality data are recorded, and implementing quantifiable criteria for evaluating effects of fisheries bycatch. 相似文献
7.
We conducted a satellite tracking study of the endangered short-tailed albatross (Phoebastria albatrus) to determine post-breeding season distribution, the amount of time spent within exclusive economic zones of Pacific Rim countries, and assess factors affecting spatial and temporal overlap with commercial fisheries in Alaska. We obtained 6709 locations for 14 albatrosses (131-808 locations and 51-138 days of tracking per bird). Albatrosses ranged widely throughout the North Pacific Rim, spending the majority of time within the exclusive economics zones of Japan, Russia (Kuril Islands and Kamchatka Peninsula), and the United States (Aleutian Islands and Bering Sea, Alaska). We found evidence for gender and age-related differences in distribution and, therefore, potential interaction with regional fisheries. Overall, albatrosses spent the greatest proportion of time within the Alaska exclusive economic zone. Within Alaska, albatrosses occurred most frequently in fishery management zones that encompassed the Aleutian Islands, Bering Sea, and south of the Alaska Peninsula. Short-tailed albatrosses had the greatest potential overlap with fisheries that occurred along continental shelf break and slope regions, e.g., longlining for sablefish (Anoplopoma fimbria), where albatrosses occurred most often. Some birds, however, also made frequent excursions onto the extensive Bering Sea shelf, suggesting significant potential for interactions with the large-scale walleye pollock (Theragra chalcogramma) and Pacific cod (Gadus macrocephalus) fisheries. Alaskan longline fishing fleets have been proactive in using seabird deterrent devices, however, our data further emphasize that such efforts beyond the Alaska exclusive economic zone would provide a greater conservation benefit for this species. 相似文献
8.
We studied the interaction between seabirds and warp cables in the high-seas Argentine hake Merluccius hubbsi trawl fishery operating in Golfo San Jorge, Argentina, and tested the efficacy of a simple mitigation measure designed to reduce mortality at warp cables. Observations were made onboard hake trawlers during the height of the fishing season, between December 2004 and April 2005. Thirteen seabird species used food made available by fishing operations. The most frequent and abundant seabirds (% occurrence, mean maximum number per haul) were the Kelp gull Larus dominicanus (98.1%, 348.5) and the Black-browed albatross Thalassarche melanophrys (96.1%, 132.2). Contacts with warp cables were recorded for six species in 81.4% of hauls, with a mean number of contacts per haul of 14.4 ± 23.8 (range = 0-127). A total of 53 individuals were killed due to interactions with nets and cables, resulting in a total cable mortality rate of 0.14 birds/haul. Considering the fishery’s fishing effort, the estimated total number of birds killed during the study was 2703 (CV = 0.8), of which 306 (CV = 0.9) were killed due to contacts with warp cables (255 Kelp gulls and 51 Black-browed albatross). The tested device consisted of a plastic cone attached to each warp cable. In hauls with mitigation device, the number of contacts was reduced by 89% and no seabirds were killed. Mean distances between seabirds and cables were significantly larger in hauls with than without mitigation device (2.6 vs 0.9 m). The proposed device could be easily applied in this and other trawl fisheries operating in Argentine waters. Increased effort should be placed in implementing mitigation measures and the monitoring of cable related mortality associated to high-seas trawlers operating in the Argentine Continental Shelf. 相似文献
9.
Kimberly S. Dietrich Julia K. Parrish Edward F. Melvin 《Biological conservation》2009,142(11):2642-2656
The incidental catch of seabirds in longline fisheries is a global conservation concern. In Alaska, annual seabird bycatch in demersal longline fisheries ranged between 10,300 and 26,300 birds (1995–2001). We explore the relationship between four categories of potential forcing factors (temporal, spatial, environmental, and fisheries-related) and seabird bycatch rates in Alaska demersal longline fisheries to provide practical management alternatives that could significantly reduce seabird bycatch.Separate generalized linear or additive models (GLM or GAM, respectively) were created for several combinations of seabird group, fishery and large geographic region. Across nearly all models, “vessel” was the most influential factor explaining seabird bycatch rate variation. Rather than a single variable, vessel is an amalgam of unmeasured forcing factors many of which could not be separated out in this data set (e.g., longline sink rate, vessel setting speed, line deployment location relative to propeller direction). A separate vessel-specific analysis also supported the multivariate results that performance of an individual vessel is overwhelmingly important (i.e., some vessels have consistently high or low bycatch rates from year to year). Therefore, vessel-specific performance is a critical management option.The effects of temporal (annual, month, and breeding phenology) and spatial variables were also moderately influential on seabird bycatch rates. Our results suggest that seasonal adjustments in the Alaska longline fishery have potential for overall bycatch reductions, but vague seabird management objectives could have huge unintended and undesirable consequences when implementing temporal adjustments. Other variables (environmental and other fishing-related factors) were frequently significant but contributed a small amount to overall explained deviance.Based on this study, we conclude that a vessel-specific management approach would be the most effective and efficient means to reduce seabird bycatch in Alaska. 相似文献
10.
David J. Anderson Kathryn P. Huyvaert Dana R. Wood Cynthia L. Gillikin Barrie J. Frost Henrik Mouritsen 《Biological conservation》2003,110(3):165-373
Albatross populations worldwide are threatened by incidental takes in longline fishery operations. The recent establishment of the Galápagos Marine Reserve (GMR) is relevant to the longline bycatch issue, as it prohibits industrial longlining in the vicinity of the major nesting site of waved albatrosses (Phoebastria irrorata). However, the legality of the fishing protections is being challenged, highlighting a need for data on use of the GMR by albatrosses. We used satellite tracking over a total of four breeding seasons to determine the distribution of waved albatrosses inside and outside the GMR, and thereby assess the degree of protection that GMR provisions offer to this species. During the incubation period, breeding adults made commuting trips from the nesting island (Isla Española) to the Peruvian upwelling zone, traveling north, east, and south after leaving the nest. During the brooding period, the distribution contracted markedly, and most satellite fixes were within the GMR. During the rearing period, breeders performed both long trips outside the GMR and short trips within. The southeastern portion of the GMR is used throughout the incubation, brooding, and early rearing periods by breeding waved albatrosses. Indirect information from non-breeding adults indicates that they are likely to use the waters of the GMR extensively. 相似文献
11.
Miguel Donoso 《Biological conservation》2010,143(11):2672-2684
Data are presented on sea turtles caught in the Chilean longline fishery targeting swordfish, Xiphias gladius, in international waters off Chile. A total of 10,604,059 hooks from 7976 sets were observed, representing 94% of the total number of hooks fished between 2001 and 2005. Leatherbacks, Dermochelys coriacea, (n = 284) and loggerheads, Caretta caretta, (n = 59) were the most common species captured. Leatherbacks were caught in less than 4% of the sets, with an overall mean of 0.0268 turtles per 1000 hooks. Loggerheads were caught in less than 1% of the sets with a mean catch rate of 0.0056 turtles per 1000 hooks. Most leatherbacks (97.5% of total) were caught between 24°S and 38°S, while loggerheads were caught primarily in the northern portion of the area fished, between 24°19′S and 25°31′S. All loggerheads were dehooked where appropriate and released alive. A total of two leatherbacks were found dead. Despite the low catch rate of leatherbacks, the potential impact of this fishery on the severely depleted nesting populations in the eastern Pacific could be significant when combined with other fisheries and threats in the region. The very low mortality of bycaught sea turtles observed in our study is encouraging and suggests that there are opportunities for further reducing harmful effects of swordfish longline fishing on sea turtles. Results of spatial analysis of loggerhead bycatch relative to fishing effort show that closure of the northernmost fishing area would eliminate the majority of the loggerhead bycatch. 相似文献
12.
Longline fisheries have expanded throughout the world's oceans since major commercial distant-water pelagic fleets began fishing for tuna and tuna-like species in the early 1950s. Along with the more recent development and expansion of demersal longline fleets for species such as Patagonian toothfish, these vessels are a major source of mortality to several species of seabird. Vessels can set many thousands of baited hooks in a day across many kilometres of water. These waters are often used as foraging areas by wide-ranging seabirds. Attracted by baits and offal, the birds can be caught on the baited hooks and subsequently drown. To provide a greater understanding of the potential impact of the Southern Ocean's longline fleets on seabird populations, this paper describes the trends in longline effort of the major pelagic and demersal fisheries in southern waters. The total reported effort from all longline fleets south of 30°S has been well over 250 million hooks per year since the early 1990s. However the spatial and temporal distribution of this effort has not been constant. While effort from the Japanese pelagic distant-water longline fleet declined through the 1990s, the Taiwanese fleet expanded dramatically. Likewise demersal fishing for toothfish increased markedly during the mid-1990s. These fisheries, along with substantial illegal longline fisheries, may be placing the long-term viability of many Southern Ocean species of seabird in jeopardy. 相似文献
13.
J.E. Moore T.M. Cox R.L. Lewison R. Bjorkland L.B. Crowder I. Ayissi P. Espeut N. Pilcher B. Solarin 《Biological conservation》2010,143(3):795-805
Recent case studies have highlighted high bycatch mortality of sea turtles and marine mammals in artisanal fisheries, but in most countries there are few data on artisanal fishing effort, catch, or bycatch. With artisanal fisheries comprising >95% of the world’s fishermen, this knowledge gap presents a major challenge to threatened species conservation and sustainable fisheries initiatives. We report on results from an intensive pilot study to evaluate whether interview surveys can be effective in assessing fishing effort and threatened species bycatch. Fisheries and bycatch data from interviews with >6100 fishermen in seven developing countries were collected in <1 year for approximately USD $47,000, indicating that this approach may rapidly yield coarse-level information over large areas at low cost. This effort provided the first fisheries characterizations for many areas and revealed the widespread nature of high bycatch in artisanal fisheries. Challenges to study design and implementation prevented quantitative estimation or spatial comparisons of bycatch during this pilot research phase, but results suggested that annual sea turtle bycatch may number at least in the low thousands of individuals per country. Annual odontocete bycatch may number at least in the low hundreds per country. Sirenian bycatch occurred in all study areas but was frequent only in West Africa. We discuss lessons learned from this survey effort and present a revised protocol for future interview-based bycatch assessments. 相似文献
14.
Despite the worrying conservation status of several albatross and petrel population, the long-term trends of many populations remain largely unknown and the causes of decline in many cases are known or very strongly suspected to be incidental mortality in fisheries. Here we combine long-term monitoring of population trends, breeding success and band recoveries to examine the past and current status of five species of albatrosses and giant petrels breeding at the same site: sooty albatross (Phoebetria fusca), light-mantled albatross (Phoebetria palpebrata), wandering albatross (Diomedea exulans), northern giant (Macronectes halli) and southern giant petrels (Macronectes giganteus) on Possession Island, Crozet archipelago. We identified three groups of trends over a 25-years period (1980-2005) suggesting common underlying causes for these species in relation to their bioclimatic foraging ranges. The Antarctic species - light-mantled albatross and southern giant petrel - appeared stable and increased recently, the Sub-Antarctic species - wandering albatross and northern giant petrel - declined with intermediate periods of increase, and finally the subtropical species - sooty albatross - declined all over the period. Breeding success, indicative of environmental conditions, showed two kinds of pattern (low and fluctuating versus high and/or increasing) which were consistent with oceanographic variations as found in a previous study. We present the analysis of fisheries-related recoveries, indicative of fisheries bycatch risks showing specific catch rates. No direct relationship between population trends and longline fishing effort was detected, probably because census data alone are not sufficient to capture the potentially complex response of demographic parameters of different life stages to environmental variation. This study highlights the contrasted changes of procellariiform species and the particularly worrying status of the subtropical sooty albatrosses, and in a lesser extent of Sub-Antarctic species. 相似文献
15.
Bycatch of common guillemots (Uria aalge) appears to be the single most serious threat to the population, and the proportion of recoveries of ringed birds in fishing gear, compared with other finding circumstances, has significantly increased during a 28 year period (P<0.01). Out of 1952 ringed common guillemots reported found between 1972 and 1999 in the Baltic Sea, 980 (50.2%) were caught in fishing gear. The bycatch in set gillnets for cod (Gadus morhua) constituted 22.3%, drift gillnets for salmon (Salmo salar) 65.5%, and other fishing gear 12.2%. The proportion of recoveries in cod gillnets has significantly increased during the study period (P<0.05), while no clear trend was observed in the recoveries in salmon gillnets. The Swedish fishing effort follows a similar pattern for cod but has decreased for salmon. The observed increased use of cod gillnets in the Baltic Sea may have contributed to the observed decrease in adult survival rate, and we provide two different estimates suggesting that significant proportions of the guillemot population are caught annually in the Baltic Sea gillnet fishery. We suggest several available techniques to reduce bycatch in the Baltic Sea fishery. 相似文献
16.
Industrial longline fisheries are considered worldwide as the main threat to albatross and petrel populations, particularly at open oceans. However, inside countries’ EEZ artisanal fleets account for a significant fishing effort and eventually, could represent a major threat to these species than industrial fishing. Here we provide the first assessment of incidental mortality in two artisanal fleets in southern Chile, targeting Austral hake and Patagonian toothfish, which accounts for 0.9 and 20 millions hooks/year, respectively. Fishing techniques of these fleets have many particularities that made their operation markedly different from the more known industrial longliners, therefore their characteristics and sink rates are thoroughly described. By-catch rates (BPUE) estimated were low: 0.030 and 0.047 birds per 1000 hooks in hake and toothfish fisheries, respectively, despite that no mitigation measured was in use. These low results may reflect the fast sink rate profile of the particular longline type used by these fisheries, although the low abundance of species present may influence too. Both fleets use a modified longline having secondary hook-lines placed vertical along the mother line, each having a weight that increases significantly its sink rate, reaching 0.33 and 0.69-0.22 m s−1 in the hake and toothfish longlines, respectively. Considering the big fishing effort deployed by the artisanal toothfish fleet, recommendations on mitigation measures are given for each fishery to further improve their fishing techniques. 相似文献
17.
As large, long-lived seabirds with delayed and slow reproduction, albatrosses have low intrinsic mortality rates and are especially vulnerable to extinction from extrinsic sources of mortality such as fishery bycatch. Leg-band recovery information for waved albatrosses revealed mortality from both incidental catch and intentional catch for human consumption. Annual adult survival in 1999-2005, estimated from capture-mark-recapture data, was lower than historical estimates. This recent increase in adult mortality probably contributed to recent and dramatic shrinkage of the breeding population; periodic matrix models confirm that population growth rate is most sensitive to changes in adult survival. Banding data and recovery information also suggest that capture by fisheries is male-biased, which should reduce fecundity in this species with obligate bi-parental care. This new documentation of bycatch, harvesting, and associated demographic consequences provides reason for serious concern about the persistence of the single breeding population of the waved albatross. 相似文献
18.
Fisheries are increasingly adopting ecosystem approaches to better manage impacts on non-target species. Although deliberate dumping of plastics at sea is banned, not all fisheries legislation prohibits discarding of gear (hooks and line) in offal, and compliance is often unknown. Analysis of a 16 year dataset collected at South Georgia indicated that the amount of gear found in association with wandering albatrosses was an order of magnitude greater than in any other species, reflecting their wider foraging range and larger gape. Unlike other taxa, most gear associated with grey-headed albatrosses was from squid and not longline fisheries, and mistaken for natural prey rather than the result of direct interaction. Observed rates of foul-hooking (entanglement during line-hauling) were much higher in giant petrels and wandering albatrosses than black-browed albatrosses, and no grey-headed albatross was affected. The index of wandering albatross gear abundance showed two peaks, the most recent corresponding with a substantial increase in the number of multifilament snoods (gangions), suggesting that the widespread adoption of a new longline system (Chilean mixed) may have been responsible. Although all identified gear was demersal, given the widespread use of similar hooks, little could be assigned to a specific fishery. Stomach content analysis suggested that 1300-2048 items of gear are currently consumed per annum by the wandering albatross population. Many hooks are completely digested by chicks, long-term effects of which are entirely unknown. We suggest a number of management approaches for addressing the problem of gear discarding, and guidelines for monitoring schemes elsewhere. 相似文献
19.
Bycatch from pelagic longline fisheries has contributed to widespread population declines of turtles, sharks and other pelagic fishes. While large-scale estimates are needed to understand cumulative impacts on these highly migratory species, detailed information on targeting, setting, and discarding practices is needed to develop bycatch mitigation approaches. Data from qualitative fishers’ knowledge interviews with Canadian Atlantic pelagic longline captains was used to evaluate current bycatch estimation methods and to identify bycatch mitigation opportunities. Interviewed longline captains reported blue sharks (Prionace glauca) were common bycatch during swordfish-targeted sets, but were sometimes absent from tuna-targeted sets. Discrepancies between longline captains’ observations and bycatch assessment methods identified needed improvements to data collection methods. Longline captains reported innovative uses of turtle dehooking gear, which two-thirds of interviewed captains had used to release other bycatch species in addition to turtles. Longline captains reported techniques for discarding pelagic stingray (Pteroplatytrygon violacea), a common bycatch species in Pacific, Atlantic and Mediterranean pelagic longline fisheries. Therefore, such techniques could decrease fisheries impacts globally. While there can be major conservation benefits from fishers’ knowledge research, one-quarter of the active longline captains that we contacted declined interviews because they did not trust the larger research process. We urge conservation biologists to carefully design fishers’ knowledge research taking into account the often politicized context. Failure to do so may jeopardize future research and conservation efforts. 相似文献
20.
Interactions between seabirds and longline fishing can cause incidental bird mortality and reduced gear efficiency. The potential for solving these problems by using a bird-scaring streamer line and a line shooter was investigated in commercial longlining in the northern Atlantic off the coast of Norway. We compared the bycatch rate of northern fulmars Fulmarus glacialis, the loss rate of baits to fulmars and the catch rates of fish target species among lines set with either of these mitigation measures, a combination of both and no mitigation measure. A total of 58,420 hooks were set in each of the four treatments. No birds were caught using the bird-scaring line alone and a single fulmar was caught when the bird-scaring line was used in combination with the line shooter. In contrast, 32 fulmars were caught in sets with no mitigation device and thirteen in sets with the line shooter alone. Losses of mackerel bait were reduced when the bird-scaring line was used, but not by using the line shooter alone. Longlines set with the line shooter reached 3 m depth 15% faster then lines set without the line shooter; beyond this depth sinking rates were similar (about 15 cm s−1). Fish catch did not vary significantly among setting methods. These results should also be applicable to the bycatch of Fulmarus spp. in demersal longline fisheries worldwide. 相似文献