Seabird bycatch vulnerability to pelagic longline fisheries: Ecological traits matter

1. Fisheries bycatch of seabirds presents a serious management problem, and relatively little is known about this problem. In the Western North Atlantic, the issue is complicated by the relatively low effort and coverage of the observer programme and the high uncertainty in species identification.
2. The Western North Atlantic is home to many endemic and endangered seabird populations, and the impact of fishery‐caused seabird bycatch has been of high interest, especially for those species with a low population size; however, species‐specific bycatch estimates have been difficult. From 1992 to 2016, 158 seabirds were observed caught by the US Atlantic pelagic longline fleet; among them, only 80 were identified to species, 25 were identified to family, and the rest – mainly in the older records – were unidentified.
3. In this study, ecological traits of seabirds were used to improve bycatch estimation and provide species‐specific risk analysis to all the potentially affected seabird species in this region. Bayesian state–space modelling was used to accommodate the high level of uncertainty in the species identification process.
4. Seabird bycatch risk was found to be highly dependent on population size. The group of large seabird species was estimated to be two times as vulnerable as the group of mid‐to‐small seabird species, scavenging and plunge‐diving feeding modes were identified as imposing high bycatch risks, and spatial and temporal distribution patterns were also good indicators of bycatch risk. Based on these ecological traits, shearwaters, gulls, gannets, and petrels were identified to potentially suffer from high bycatch in this region. These species, especially those that have not been identified historically, deserve extra attention in the observer programme, and for the implementation of conservation measures of seabirds in this region.

     

Characterization of seabird bycatch in eastern Canadian waters, 1998–2011, assessed from onboard fisheries observer data

相似文献   

Decreasing but still high: bycatch of seabirds in gillnet fisheries along the German Baltic coast

相似文献   

Are bycatch rates sufficient as the principal fishery performance measure and method of assessment for seabirds?

相似文献   

Seabird interactions and by‐catch in the anchovy pelagic trawl fishery operating in northern Argentina

相似文献   

Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery

1. Increasing the sink rate of baited hooks by adding weights in close proximity to the hook is crucial to reduce seabird mortality in pelagic longline fisheries. However, weights placed next to the hook are a cause for concern for fishing crew because they can fly back in the event of a line break, injuring deck crew.
2. Lumo Leads, an alternative weight system designed to slide in the event of a line break, and therefore prevent accidents, were trialled in pelagic longline fisheries off southern Brazil. Four fishing trips were conducted and 26,377 hooks sampled to compare sink rates, seabird bycatch rates and catch rates of target species between three treatments: (1) 60 g Lumo Lead attached at 1.0 m from the hook; (2) 60 g Lumo Lead at 3.5 m; and (3) 60 g leaded swivels at 3.5 m from the hook.
3. A Lumo Lead placed at 1.0 m from the hook resulted in a faster sink rate and caught fewer seabirds (0.11 birds per unit of effort [BPUE]) when compared with a Lumo Lead (0.33 BPUE) or weighted swivel (0.85 BPUE) placed at 3.5 m. The bycatch with Lumo Lead placed at 1.0 m from the hook was 90% lower than the bycatch of Lumo Lead or weighted swivel placed at 3.5 m combined. There was no difference in the catch rates of target species between the three treatments.
4. These findings support a growing body of evidence that placing weights close to the hook reduces seabird bycatch without affecting the catchability of the target species. The high seabird bycatch rates recorded despite night setting and recommended line weighting regimes reinforces the need of simultaneous deployment of a toriline with these other two mitigation measures to reduce seabird bycatch to negligible levels in the south‐west Atlantic.

     

Tori‐lines with weighted branch lines reduce seabird bycatch in eastern South Pacific longline fishery

相似文献   

Identifying the origins of fishing gear ingested by seabirds: a novel multivariate approach

• 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.

     

Sea turtles bycatch in the Adriatic Sea set net fisheries and possible hot‐spot identification

1. Bycatch resulting from fishing activities is the main threat for the conservation of sea turtles in the Mediterranean Sea. Fixed nets are a matter of concern for sea turtles mainly in coastal areas during the neritic stage when both juvenile and adult life stages are affected. Mortality caused by entanglement in set nets is related to forced apnoea due to the high soak time of the nets and consequent drowning.
2. This study investigated the loggerhead turtle bycatch in set net coastal fisheries in the northern Adriatic Sea (General Fisheries Commission for the Mediterranean Geographical Sub‐Area 17, [GSA 17]) through an interview‐based approach, to understand the potential contribution of these fisheries to the general decline of the sea turtle population. A second goal was to identify a possible hot‐spot turtle bycatch area through on‐board observations.
3. The study estimates that more than 5400 turtles are caught in the west GSA 17 each year with the largest number in the summer. A hot‐spot for entanglement was also identified in an area located south of the River Po delta (41.5–69 m depth) during the summer. Sixty‐four turtles were caught over a period of 30 fishing days by either trammel nets and gillnets (0.7 and 0.5 turtle per km of net respectively) and was the greatest number that has been observed anywhere in the Mediterranean.
4. Possible management strategies to reduce bycatch include technical modification to gear setting (such as reducing netting slack and using small meshes), bycatch reducer devices (such as LED UV), and area and seasonal gear restrictions to small‐scale fisheries in areas of greatest concern in the northern Adriatic Sea.

     

Incidental capture of leatherback sea turtles in fixed fishing gear off Atlantic Canada

1. Incidental capture in commercial fishing gear is a threat to many populations of marine megafauna, including sea turtles. While research has largely focused on pelagic longline impacts on sea turtles, fixed‐gear fisheries are a significant, historically understudied source of injury and mortality.
2. The present study assesses the interaction of endangered leatherback sea turtles (Dermochelys coriacea) with fixed‐gear fisheries in high‐latitude seasonal foraging habitat where sub‐adult and adult turtles aggregate.
3. Records of leatherback‐fishery interactions (n = 205) were compiled from databases of publicly‐reported sea turtle sightings in Atlantic Canada (1998–2014) to identify the spatio‐temporal distribution of these events; to identify corresponding fisheries and gear types; and to describe the mechanics and outcomes of entanglements in fixed gear.
4. Most reports came from coastal Nova Scotia (n = 136) and Newfoundland (n = 40), with reporting rates peaking in the mid‐to‐late 2000s. The majority of entanglements were reported during the summer months of July and August when leatherbacks are seasonally resident and several fisheries are active in continental shelf waters.
5. Entanglements were most commonly reported in pot gear (e.g. snow crab, lobster, whelk) and trap nets (e.g. mackerel), reflecting extensive use of polypropylene lines distributed in the upper water column where leatherback foraging activity is concentrated.
6. Given reporting biases and uncertainty regarding post‐release survivorship, entanglement mortalities should be considered a gross underestimate of true mortality rates.
7. This study highlights both the importance of looking beyond pelagic longlines to evaluate leatherback interactions with fixed‐gear fisheries in high‐use continental shelf foraging habitat, and of involving the fishing industry in developing mitigation measures to reduce entanglement rates and associated turtle mortality.