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Khaled Echwikhi Imed Jribi Mohamed Nejmeddine Bradai Abderrahmen Bouain 《水产资源保护:海洋与淡水生态系统》2010,20(5):525-530
- 1. Sea turtles may migrate vast distances from their feeding areas to home rookeries where they nest. During these migrations sea turtles are subject to many threats, among which are interactions with pelagic longlines.
- 2. This gear is used frequently in the summer period in the Gulf of Gabes targeting mainly the sandbar shark (Carcharhinus plumbeus). Hooks are baited with mackerel (Scomber scombrus) or pieces of stingray (Dasyatis pastinaca).
- 3. Twenty‐one fishing trips (48 sets with a total of 35 950 hooks deployed) were conducted using onboard observers in the south of the Gulf of Gabes during the months of July, August and September in 2007 and 2008. Stingray and mackerel bait were used in 19 and 29 sets, respectively.
- 4. In total, 29 loggerhead sea turtles (Caretta caretta) were captured; the majority of them were juvenile and active. Turtles were caught at a statistically greater frequency on sets with hooks baited with mackerel than on sets with hooks baited with pieces of stingray.
- 5. The type of bait also affected the catch of the target species by increasing the efficiency when pieces of stingrays were used.
- 6. These results encourage further research into new baits to mitigate turtle catch by longline fisheries without affecting the catch of target species. Copyright © 2010 John Wiley & Sons, Ltd.
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- In order to increase their catches, longliners targeting sharks in the Gulf of Gabes, Tunisia, have increased the number of hooks per basket and have included new bait types instead of mackerel (Scomber scombrus). This paper reports the effects of these changes on catch composition, catch rates, size distribution, life‐stage captures, and mortality at haulback.
- Data from 48 and 96 longline sets, carried out during the shark fishing seasons of 2007 and 2008, with two hooks per basket, and 2016 and 2017, with five hooks per basket, respectively, were examined to assess the effect of gear change. Moreover, the effects of bait types were inspected based on 33 fishing sets using whole mackerel, 19 using salema (Sarpa salpa) halves, and 27 using pieces of stingray (Dasyatis spp.), sampled during 2016 and 2017.
- The species composition indicated that longliners expand the vertical distribution of their hooks to operate from the surface to the bottom. The catches with both longline designs were dominated by sandbar shark (Carcharhinus plumbeus). Despite gear changes, the catch rate of C. plumbeus decreased by 42.21%, suggesting population decline. The size composition indicated a shift towards larger specimens, mainly adult females, which could jeopardize the shark population. Moreover, the mortality of the main species at haulback seems to be affected by the design of the longline.
- The bait used, mainly pieces of stingray, significantly increased the catch rate of sandbar shark, which suggests a greater attractiveness of the new bait; however, fish size and mortality rates at haulback were unchanged in response to bait variation.
- The fishery operates in shark nursery grounds, which exposes these fish (principally C. plumbeus) to considerable exploitation pressure. The new fishing practices intensified the pressure and thus the risk of a rapid depletion of populations. To preserve the shark species in the area, the use of new gear and attractive bait should be banned.
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A cross‐taxa assessment of pelagic longline by‐catch mitigation measures: conflicts and mutual benefits to elasmobranchs 
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下载免费PDF全文 Elasmobranch mortality in pelagic longline fisheries poses a risk to some populations, alters the distribution of abundance between sympatric competitors, changing ecosystem structure, processes and stability. Individual and synergistic effects on elasmobranch catch and survival from pelagic longline gear factors, including methods prescribed to mitigate bycatch of other vulnerable taxa, were determined. Overall relative risk of higher circle vs. J‐shaped hook shark catch rates conditioned on potentially informative moderators, from 30 studies, was estimated using an inverse‐precision weighted mixed‐effects meta‐regression modelling approach. Sharks had a 1.20 times (95% CI: 1.03–1.39) significantly higher pooled relative risk of capture on circle hooks, with two significant moderators. The pooled relative risk estimate of ray circle hook catch from 15 studies was not significant (RR = 1.22, 95% CI: 0.89–1.66) with no significant moderators. From a literature review, wire leaders had higher shark catch and haulback mortality than monofilament. Interacting effects of hook, bait and leader affect shark catch rates: hook shape and width and bait type determine hooking position and ability to sever monofilament leaders. Circle hooks increased elasmobranch catch, but reduced haulback mortality and deep hooking relative to J‐shaped hooks of the same or narrower width. Using fish vs. squid for bait increased shark catch and deep hooking. Pelagic stingray (Pteroplatytrygon violacea) catch and mortality were lower on wider hooks. Using circle instead of J‐shaped hooks and fish instead of squid for bait, while benefitting sea turtles, odontocetes and possibly seabirds, exacerbates elasmobranch catch and injury, therefore warranting fishery‐specific assessments to determine relative risks. 相似文献
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- 1. The global decline of albatrosses (Diomedidae: Procellariiformes) is thought to have occurred largely as a direct result of fishery‐related mortality. Albatrosses and other large petrels interact with fisheries in several ways, including scavenging used bait and discarded offal, which may contain hooks.
- 2. Hooks that are ingested by breeding birds are often fed to chicks which subsequently regurgitate them shortly before fledging.
- 3. In this study a series of mathematical (cladistic, cluster and principal components) analyses are applied to a sample of 241 items of fishing gear (hook, snood and hook/snood unit) collected from seabird nest sites on Bird Island, South Georgia, and 44 reference gear items provided by four South Atlantic regional fisheries.
- 4. The five separate analyses failed to assign most gear to a particular fishery or to identify any consistent annual trends. The homogeneous nature of the material, which was largely derived from the same manufacturers, meant that gear origin could not be determined. This suggests that hooks found at seabird colonies in this, and potentially other regions, will be of limited use in identifying offending fisheries, unless operators are obliged to deploy gear with unique marks in the future.
- 5. Nevertheless, it is suggested that this approach should work effectively where birds interact with a range of fisheries targeting different species using variable gear. This study therefore represents an innovative approach to the characterization of lost fishing gear with potentially widespread application. Copyright © 2010 John Wiley & Sons, Ltd.
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Caitlin K. Frankish Andrea Manica Joan Navarro Richard A. Phillips 《水产资源保护:海洋与淡水生态系统》2021,31(7):1715-1729
- Many seabirds dive to forage, and the ability to use this hunting technique varies according to such factors as morphology, physiology, prey availability, and ambient light levels. Proficient divers are more able to seize sinking baits deployed by longline fishing vessels and may return them to the surface, increasing exposure of other species. Hence, diving ability has major implications for mitigating incidental mortality (bycatch) in fisheries.
- Here, the diving behaviour and activity patterns of the most bycaught seabird species worldwide, the white-chinned petrel (Procellaria aequinoctialis), tracked from Bird Island (South Georgia), are analysed. Three data sources (dives, spatial movements, and immersion events) are combined to examine diverse aspects of at-sea foraging behaviour, and their implications for alternative approaches to bycatch mitigation are considered.
- The tracked white-chinned petrels (n = 14) mostly performed shallow dives (<3 m deep) of very short duration (<5 s), predominantly during darkness, but only 7 and 10% of landings in daylight and darkness, respectively, involved diving, suggesting that surface-seizing is the preferred foraging technique. Nonetheless, individuals were able to dive to considerable depth (max = 14.5 m) and at speed (max = 2.0 m·s−1), underlining the importance of using heavy line-weighting to maximize hook sink rates, and bird-scaring lines (Tori lines) that extend for long distances behind vessels to protect hooks until beyond diving depths.
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Rowan Trebilco Rosemary Gales Emma Lawrence Rachael Alderman Graham Robertson G. Barry Baker 《水产资源保护:海洋与淡水生态系统》2010,20(5):531-542
- 1. Seabirds killed incidentally in Australia's eastern tuna and billfish (ETBF) longline fishery between September 2001 and June 2006 were examined to evaluate species composition and to relate, where possible, capture events to operational and environmental factors.
- 2. During this period 2.129 million hooks on 2202 shots were observed, and 369 birds were reported killed. The majority (78%) of these were flesh‐footed shearwaters (Puffinus carniepes), 53% of which were male and 44% female. Smaller numbers of medium to large sized albatrosses (Diomedeidae, predominantly female) and other shearwaters (Puffinus spp.) and petrels (Pterodroma spp.) dominated the remainder of the bycatch.
- 3. Of the 369 birds reported taken as bycatch, 280 were available for necropsy, and species identifications performed in situ by observers were assessed. While observer identifications were generally correct for common species, performance was poor for less common ones.
- 4. The geographical location (latitude) of shots, season, time of day at which shots were set, and bait type and life status (dead or alive) influenced the seabird bycatch rate. The majority of captures (87% overall) occurred between 30 and 35°S, with bycatch being lowest in winter, and remaining at similar levels across the other seasons.
- 5. The use of live fish bait was generally associated with increased captures of both seabirds overall, and flesh‐footed shearwaters in particular. Copyright © 2010 John Wiley & Sons, Ltd.
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- 1. Circle hooks have rapidly become popular among recreational anglers, based largely on the assumption that their use aids in the conservation of fisheries resources by reducing gut hooking, and hence mortality. In addition, circle hooks are intended to facilitate jaw hooking. Unfortunately, these assumptions have been perpetuated by anecdotal reports with very little rigorous scientific information to support these assertions.
- 2. A number of recently published, forthcoming, and grey literature reports provide an opportunity to review briefly and synthesize research conducted on circle hooks. We surveyed literature databases and also used questionnaires to solicit information from unpublished or in‐progress circle hook research.
- 3. Although among studies the results have been quite disparate, overall the mortality rates were consistently lower for circle hooks than J‐style hooks. In addition, circle hooks were more frequently hooked in the jaw, and less frequently hooked in the gut than conventional hook types. There is no doubt that in some marine fisheries, such as tuna, billfish, and striped bass, capture efficiency remains high and injury and mortality rates are drastically reduced. However, in other species (e.g. bluegill), injury can actually be more severe from circle hooks relative to some other hook types. In other species, such as largemouth bass, circle hooks have minimal conservation benefit, but have reduced capture efficiency relative to conventional hook designs.
- 4. Factors such as hook size, fishing style, fish feeding mode, and mouth morphology all appear to affect the effectiveness of circle hooks. For these reasons, it is difficult to promote the adoption of the use of circle hooks as a panacea for all fish and fisheries. Instead, we recommend that management agencies focus on recommending circle hooks only for instances for which appropriate scientific data exist.
- 5. The recent interest in circle hooks has been beneficial for stimulating interest and research on the role of hook designs in reducing hooking‐related injury and mortality. We encourage tackle manufacturers to continue to develop new hook designs that have the potential to provide conservation benefit to caught and released fish. This paper provides direction to management agencies and outdoor media for disseminating responsible information to anglers regarding the application of circle hooks for conserving fisheries resources.
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Yonat Swimmer Randall Arauz John Wang Jenny Suter Michael Musyl Allan Bolaños Andrés López 《水产资源保护:海洋与淡水生态系统》2010,20(4):445-451
- 1. This study compared the catch rates of targeted dolphinfish or mahimahi (Coryphaena hippurus), and sea turtles and other fish bycatch in a shallow‐set Costa Rican longline fishery using 14/0 circle hooks with and without a 10° offset. The effect of hook offset on hooking location and injury in captured sea turtles, specifically if the hooking was external, in the mouth, or in the esophagus was also evaluated.
- 2. Results were compared from six trips totalling 33 876 hooks with squid (Dosidicus gigas) used as bait. In total, mahimahi catch‐per‐unit‐effort (CPUE, expressed as number caught per 1000 hooks) was similar between hook types (CPUE～52).
- 3. Olive ridley sea turtles (Lepidochelys olivacea) were caught on all 42 sets. In total, 640 olive ridley turtles were caught and released alive. There were no significant differences in the number of sea turtles caught between hooks with and without an offset (CPUE～19) nor between hook type and anatomical hooking location, suggesting similar levels of injury for turtles caught on each hook type.
- 4. These data suggest that a 10° offset on 14/0 circle hooks does not confer any selective advantages over hooks with no offset with respect to capture rates of mahimahi, sea turtles, sharks, or pelagic stingrays in a shallow set pelagic longline fishery. Copyright © 2010 John Wiley & Sons, Ltd.
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Mortality in longline fisheries is a critical global threat to most albatross and large petrel species. Here we identify key principles and approaches to identify and achieve broad use of effective seabird by‐catch avoidance methods. Despite the availability of highly effective and cost‐saving seabird avoidance methods, few longline fleets employ them. Given the political context and capacity of management authorities of the majority of longline fisheries, it is critical to identify seabird avoidance strategies that are not only highly effective, but are also economically viable and commercially practical. Adoption of an international performance standard for longline baited hook–sink rate, and prescribing minimum gear weighting designs that meet this standard that are achievable by all longline fisheries, would be an important step forward towards resolving low use of seabird avoidance methods by vessels, including those in illegal, unregulated and unreported fisheries. Due to differences between fleets, no single seabird avoidance measure is likely to be effective and practical in all longline fisheries. Therefore, testing of seabird avoidance methods in individual fleets is needed to determine efficacy and economic viability. Longline fishers should directly participate in these trials as they have a large repository of knowledge and skills to effectively develop and improve seabird by‐catch avoidance techniques, and this provides industry with a sense of ownership for uptake of effective by‐catch reduction methods. Establishing protected areas containing seabird colonies and adjacent waters within a nation's EEZ can be an expedient method to address seabird by‐catch. However, establishing high seas marine protected areas to restrict longline fishing in seabird foraging areas, which would require extensive and dynamic boundaries and large buffer zones, may not be a viable short‐term solution because of the extensive time anticipated to resolve legal complications with international treaties, to achieve international consensus and political will, and to acquire requisite extensive resources for surveillance and enforcement. Analysis of results of research on seabird avoidance methods reveals that the most reliable comparisons of the efficacy of alternative strategies are from comparing the effectiveness of methods tested in a single experiment. Benefits from standardizing the reporting of seabird by‐catch rates to account for seabird abundance are described. To provide the most precise inputs for seabird population models, estimates of seabird mortality in longline fisheries should account for seabird falloff from hooks before hauling, delayed mortality of seabirds caught but freed from gear, and mortality caused by hooks discarded in offal. 相似文献
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Bechir Saidi Khaled Echwikhi Samira Enajjar Sami Karaa Imed Jribi Mohamed N. Bradai 《水产资源保护:海洋与淡水生态系统》2020,30(6):1172-1181
- This study evaluated the circle hook use as a tool for shark management in the pelagic longline fishery in the Gulf of Gabès.
- The usual J‐hook No. 2 with 10° offset, which has been traditionally used by the fishery, was compared to the 18/0 non‐offset circle hook in an alternating fashion along the main line. In total, 22 experimental longline sets were deployed through the shark fishing seasons of 2016 and 2017 to examine the effects of hook types on the catch composition, the catch rates, the hooking location, and the status at haulback.
- The catch composition differed significantly among hook types. Moreover, an overall increase in catch rates for the main species, the sandbar shark Carcharhinus plumbeus, and the shortfin mako shark Isurus oxyrinchus, was observed when using circle hooks.
- There was no size‐selective effect of circle hooks for the common species. The circle hooks were not effective at reducing at‐haulback mortality of sandbar shark. Conversely, shortfin mako and smooth‐hound shark Mustelus mustelus showed significantly lower relative mortality at haulback with circle hooks than with J‐hooks. Furthermore, circle hooks were more frequently hooked externally than the J‐hooks for the three shark species.
- Results demonstrated that the use of 18/0 non‐offset circle hooks in the pelagic shark longline fishery can reduce mortality at haulback for some species without any benefit for the dominant species, the sandbar shark.
- Overall, it is difficult to promote the adoption of the use of circle hooks as a management measure in this specialized fishery. Management measures focusing on fishing effort controls, fishing closures in critical habitats, and size limits could have significant benefits for the conservation of shark species and may help to improve the sustainability of the shark fishery in the Gulf of Gabès.
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1. The likelihood that seabirds will be hooked and drowned in longline fisheries increases when baited hooks sink slowly. Fishermen target different fishing depths by setting the mainline through a line shooter, which controls the tension (or slackness) in the line. An experiment was conducted in Australia's pelagic longline fishery to test the hypothesis of no difference in sink rates of baited hooks attached to mainline set under varying degrees of tension. 2. Mainline was set in three configurations typically used in the fishery: (a) surface set tight with no slackness astern; (b) surface set loose with 2 s of slack astern; and (c) deep set loose with 7 s of slack astern. 3. Tension on the mainline had a powerful effect on sink rates. Baited hooks on branch lines attached to tight mainlines reached 2 m depth nearly twice as fast as those on the two loose mainline tensions, averaging 5.8 s (0.35 m s?1) compared with 9.9 s (0.20 m s?1) and 11.0 s (0.18 m s?1) for surface set loose and deep set loose tensions, respectively. 4. The likely reason for the difference is propeller turbulence. Tight mainline entered the water aft of the area affected by turbulence whereas the two loose mainlines and the clip ends of branch lines were set directly into it about 1 m astern of the vessel. The turbulence presumably slowed the sink rates of baited hooks at the other end of the branch lines. 5. The results suggest that mainline deployed with a line shooter (as in deep setting) into propeller turbulence at the vessel stern slows the sink rates of baited hooks, potentially increasing their availability to seabirds. Unless mainline can be set to avoid propeller turbulence the use of line shooters for deep setting should not be promoted as an effective deterrent to seabirds. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献