Bycatch

Entanglement rates and haulout abundance trends of Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lions on the north coast of Washington state

Allyn EMarina, Scordino JJoseph. Entanglement rates and haulout abundance trends of Steller (Eumetopias jubatus) and California (Zalophus californianus) sea lions on the north coast of Washington state Wells B. PLOS ONE [Internet]. 2020 ;15(8):e0237178. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237178
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Entanglements affect marine mammal species around the globe, and for some, those impacts are great enough to cause population declines. This study aimed to document rates and causes of entanglement and trends in local haulout abundance for Steller and California sea lions on the north coast of Washington from 2010–2018. We conducted small boat surveys to count sea lions and document entangled individuals. Rates of entanglement and entangling material occurrence were compared with records of stranded individuals on the Washington and Oregon coast and with packing bands recorded during beach debris surveys. The rate of entanglement for California sea lions was 2.13%, almost entirely composed of adult males, with a peak rate during June and July potentially due to some entangled individuals not migrating to their breeding grounds. For Steller sea lions, the rate of entanglement was 0.41%, composed of 77% adults (32.4% male, 63.3% female), 17.1% juveniles, 5.9% unknown age, and no pups. Steller sea lions exhibited a 7.9% ± 3.2 rate of increase in abundance at the study haulouts, which was similar to that seen in California sea lions (7.8% ± 4.2); both increases were greater than the population growth rates observed range-wide despite high rates of entanglement. Most entanglements for both species were classified as packing bands, followed by entanglement scars. Salmon flashers were also prevalent and only occurred from June–September during the local ocean salmon troll fishery. Packing band occurrence in beach debris surveys correlated with packing band entanglements observed on haulouts. However, no packing band entanglements were observed in the stranding record and the rate of stranded animals exhibiting evidence of entanglement was lower than expected, indicating that entanglement survival is higher than previously assumed. Future studies tracking individual entanglement outcomes are needed to develop effective, targeted management strategies.

Using GIS and stakeholder involvement to innovate marine mammal bycatch risk assessment in data-limited fisheries

Verutes GM, Johnson AF, Caillat M, Ponnampalam LS, Peter C, Vu L, Junchompoo C, Lewison RL, Hines EM. Using GIS and stakeholder involvement to innovate marine mammal bycatch risk assessment in data-limited fisheries Duplisea DE. PLOS ONE [Internet]. 2020 ;15(8):e0237835. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237835
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Fisheries bycatch has been identified as the greatest threat to marine mammals worldwide. Characterizing the impacts of bycatch on marine mammals is challenging because it is difficult to both observe and quantify, particularly in small-scale fisheries where data on fishing effort and marine mammal abundance and distribution are often limited. The lack of risk frameworks that can integrate and visualize existing data have hindered the ability to describe and quantify bycatch risk. Here, we describe the design of a new geographic information systems tool built specifically for the analysis of bycatch in small-scale fisheries, called Bycatch Risk Assessment (ByRA). Using marine mammals in Malaysia and Vietnam as a test case, we applied ByRA to assess the risks posed to Irrawaddy dolphins (Orcaella brevirostris) and dugongs (Dugong dugon) by five small-scale fishing gear types (hook and line, nets, longlines, pots and traps, and trawls). ByRA leverages existing data on animal distributions, fisheries effort, and estimates of interaction rates by combining expert knowledge and spatial analyses of existing data to visualize and characterize bycatch risk. By identifying areas of bycatch concern while accounting for uncertainty using graphics, maps and summary tables, we demonstrate the importance of integrating available geospatial data in an accessible format that taps into local knowledge and can be corroborated by and communicated to stakeholders of data-limited fisheries. Our methodological approach aims to meet a critical need of fisheries managers: to identify emergent interaction patterns between fishing gears and marine mammals and support the development of management actions that can lead to sustainable fisheries and mitigate bycatch risk for species of conservation concern.

Switching Gillnets to Longlines: An Alternative to Mitigate the Bycatch of Franciscana Dolphins (Pontoporia blainvillei) in Argentina

Berninsone LG, Bordino P, Gnecco M, Foutel M, Mackay AI, Werner TB. Switching Gillnets to Longlines: An Alternative to Mitigate the Bycatch of Franciscana Dolphins (Pontoporia blainvillei) in Argentina. Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2020.00699/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1418755_45_Marine_20200903_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

The franciscana dolphin (Pontoporia blainvillei) is considered the most threatened cetacean in the South Western Atlantic due to bycatch in gillnet fisheries of Argentina, Uruguay, and Brazil. As gillnet fisheries operate in the same areas inhabited by dolphins, methods and strategies to reduce bycatch require particular attention. This study investigated the potential of switching gillnets to bottom longlines to reduce franciscana bycatch rates while maintaining economic returns in a small-scale artisanal fishery in Argentina. Trials were conducted in Bahía Samborombón and Cabo San Antonio between October 2004 and January 2007, in cooperation with artisanal fishermen who simultaneously fished using bottom longlines and gillnets. Target and non-target catch composition, fishing yield, catch size distribution and quality of catch, as well as bycatch of dolphins, sea turtles, and interaction with sea lions were compared between the two fishing methods to assess the profitability of switching fishing gears. Hauls of both gear types deployed simultaneously in the same locations showed similar fish catch composition and catch size with both gears but reduced catch of juvenile fishes in longlines. Bycatch of franciscana in bottom longlines was limited to only one dolphin in three consecutive years of trials, and no direct interaction between turtles and hooks were recorded. The economic analysis showed financially acceptable perspectives under a 5-year scenario. Reducing gillnet effort by switching to bottom longlines appears a practical approach to creating a sustainable fishery that could result in significant mitigation of current bycatch of franciscana dolphins in Argentina. However, implementation requires acceptance and compliance by the artisanal gillnet fishery.

Using GIS and stakeholder involvement to innovate marine mammal bycatch risk assessment in data-limited fisheries

Verutes GM, Johnson AF, Caillat M, Ponnampalam LS, Peter C, Vu L, Junchompoo C, Lewison RL, Hines EM. Using GIS and stakeholder involvement to innovate marine mammal bycatch risk assessment in data-limited fisheries. PLOS ONE [Internet]. 2020 ;15(8):e0237835. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237835
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Fisheries bycatch has been identified as the greatest threat to marine mammals worldwide. Characterizing the impacts of bycatch on marine mammals is challenging because it is difficult to both observe and quantify, particularly in small-scale fisheries where data on fishing effort and marine mammal abundance and distribution are often limited. The lack of risk frameworks that can integrate and visualize existing data have hindered the ability to describe and quantify bycatch risk. Here, we describe the design of a new geographic information systems tool built specifically for the analysis of bycatch in small-scale fisheries, called Bycatch Risk Assessment (ByRA). Using marine mammals in Malaysia and Vietnam as a test case, we applied ByRA to assess the risks posed to Irrawaddy dolphins (Orcaella brevirostris) and dugongs (Dugong dugon) by five small-scale fishing gear types (hook and line, nets, longlines, pots and traps, and trawls). ByRA leverages existing data on animal distributions, fisheries effort, and estimates of interaction rates by combining expert knowledge and spatial analyses of existing data to visualize and characterize bycatch risk. By identifying areas of bycatch concern while accounting for uncertainty using graphics, maps and summary tables, we demonstrate the importance of integrating available geospatial data in an accessible format that taps into local knowledge and can be corroborated by and communicated to stakeholders of data-limited fisheries. Our methodological approach aims to meet a critical need of fisheries managers: to identify emergent interaction patterns between fishing gears and marine mammals and support the development of management actions that can lead to sustainable fisheries and mitigate bycatch risk for species of conservation concern.

Guidelines for the Safe and Humane Handling and Release of Bycaught Small Cetaceans from Fishing Gear

Hamer DJ, Minton G. Guidelines for the Safe and Humane Handling and Release of Bycaught Small Cetaceans from Fishing Gear. Bonn, Germany: UNEP/CMS & WWF; 2020 p. 50. Available from: https://www.cms.int/en/publication/guidelines-safe-and-humane-handling-and-release-bycaught-small-cetaceans-fishing-gear
Freely available?: 
Yes
Summary available?: 
No
Type: Report

These guidelines, in their full text format, are intended to provide fisheries managers at any level, as well as those who work with fisheries to improve their sustainability, with bestpractice methodology on the safe and humane handling and release of small cetaceans accidentally bycaught in fishing gear. They are intended to enable managers and ‘trainers’, as well as anyone involved with fisheries policy or management to understand the rationale and need for ‘best practice’, as well as the science that supports the recommended practices.

The illustrations provided with these guidelines, as well as the bullet-pointed handling notes, can be used to develop 2-page laminated fisher-friendly ‘Flips’ (ready reckoners) that contain clear, concise, bullet-pointed instructions pertinent to each specific fishery.

Mitigation of Elasmobranch Bycatch in Trawlers: A Case Study in Indian Fisheries

Gupta T, Booth H, Arlidge W, Rao C, Manoharakrishnan M, Namboothri N, Shanker K, Milner-Gulland EJ. Mitigation of Elasmobranch Bycatch in Trawlers: A Case Study in Indian Fisheries. Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2020.00571/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1391749_45_Marine_20200730_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Bycatch poses a significant threat to marine megafauna, such as elasmobranchs. India has one of the highest elasmobranch landings globally, through both targeted catch and bycatch. As elasmobranchs contribute to food and livelihood security, there is a need for holistic approaches to bycatch mitigation. We adopt an interdisciplinary approach to critically assess a range of hypothetical measures for reducing elasmobranch capture in a trawler fishery on India’s west coast, using a risk-based mitigation hierarchy framework. Data were collected through landing surveys, interviews and a literature review, to assess the following potential management options for their technical effectiveness and socio-economic feasibility: (1) spatio-temporal closures; (2) net restrictions; (3) bycatch reduction devices (BRDs); and (4) live onboard release. Our study provides the first evidence-based and nuanced understanding of elasmobranch bycatch management for this fishery, and suggestions for future conservation and research efforts. Onboard release may be viable for species like guitarfish, with moderate chances of survival, and was the favored option among interview respondents due to minimal impact on earnings. While closures, net restrictions and BRDs may reduce elasmobranch capture, implementation will be challenging under present circumstances due to the potentially high impact on fisher income. Interventions for live release can therefore be used as a step toward ameliorating bycatch, while initiating longer-term engagement with the fishing community. Participatory monitoring can help address critical knowledge gaps in elasmobranch ecology. Spatio-temporal closures and gear restriction measures may then be developed through a bottom-up approach in the long term. Overall, the framework facilitated a holistic assessment of bycatch management to guide decision-making. Scaling-up and integrating such case studies across different species, fisheries and sites would support the formulation of a meaningful management plan for elasmobranch fisheries in India.

Toward elimination of unwanted catches using a 100 mm T90 extension and codend in demersal mixed fisheries

Robert M, Morandeau F, Scavinner M, Fiche M, Larnaud P. Toward elimination of unwanted catches using a 100 mm T90 extension and codend in demersal mixed fisheries Patterson HM. PLOS ONE [Internet]. 2020 ;15(7):e0235368. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0235368
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Most European fishing fleets will need to drastically reduce their unwanted catches to comply with new rules of the common fisheries policy. A more practical way to avoid increasing on-board sorting time and issues linked to storage capacity is to prevent unwanted catches in the first place. We assessed the selectivity properties of an experimental fishing gear that combined a 100 mm T90 cylinder with 130 meshes in the extension and a 100 mm T90 codend of 33 meshes (experimental gear) compared to a 100 mm diamond mesh extension and codend (control gear) during commercial trips using twin trawls. Analysis of the relative size composition of catches indicated a significantly higher escapement of small fish of several target species (e.g. Lepidorhombus whiffiagonisMelanogrammus aeglefinusRaja spp, and Lophius spp) and non-target species (e.g. Capros aper and Gurnards spp) from the T90 experimental trawl compared to the control trawl (n = 49 hauls), resulting in a significant reduction of unwanted catches of Gadidae, Triglidae, and Caproidae. In contrast, non-negligible commercial losses of small grade target gadoid species were observed. Mixed general linear models showed that the proportion of ray, haddock and anglerfish retained per length class decreased with increased tow duration. The T90 experimental gear will perform at a commercial level when targeting monkfish, megrim, rays and large haddock, however fishers are not likely to use this gear when targeting smaller-bodied species such as cephalopods, small haddock, whiting (Merlangius merlangus) and hake (Merluccius merluccius), because the gear is likely to allow large numbers to escape. Selectivity studies often focus on a short list of target species; however, catches of non-target species under quota can be problematic for some fisheries. For example, under the implementation of the Landing Obligation catches of boarfish could choke the French whitefish demersal fisheries in the Celtic sea, as France has no national quota for that species. The device tested constitutes an efficient solution to mitigate catches for such non-target schooling fish.

Assessing the Effects of Banana Pingers as a Bycatch Mitigation Device for Harbour Porpoises (Phocoena phocoena)

Omeyer LCM, Doherty PD, Dolman S, Enever R, Reese A, Tregenza N, Williams R, Godley BJ. Assessing the Effects of Banana Pingers as a Bycatch Mitigation Device for Harbour Porpoises (Phocoena phocoena). Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/articles/10.3389/fmars.2020.00285/full?utm_source=F-AAE&utm_medium=EMLF&utm_campaign=MRK_1334659_45_Marine_20200521_arts_A
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Bycatch is a significant cause of population declines of marine megafauna globally. While numerous bycatch mitigation strategies exist, acoustic alarms, or pingers, are the most widely adopted strategy for small cetaceans. Although pingers have been shown to be an effective measure for numerous species, there are some concerns about their long-term use. Bycatch is recognized as a persistent problem in waters around Cornwall, United Kingdom, where several cetacean species are resident, with harbour porpoises (Phocoena phocoena) being the most-commonly sighted. In this study, we assessed the effects of a Banana Pinger (Fishtek Marine Limited) on harbour porpoises in Cornwall between August 2012 and March 2013. Two passive acoustic loggers (C-PODs; Chelonia Limited) were deployed 100 m apart to record cetacean activity during cycles of active and inactive pinger periods. Harbour porpoises were 37% less likely to be detected at the C-POD near the pinger when the pinger was active, while they were only 9% less likely to be detected 100 m further away. The effect of the pinger was constant over the study period at both C-PODs despite the temporal variation in harbour porpoise detections. In addition, we found no evidence of reduced pinger effect with changing environmental conditions. Furthermore, harbour porpoise detections at the C-POD near the pinger did not depend on the time elapsed since the pinger turned off, with harbour porpoises returning to the ensonified area with no delay. Together these results suggest that (1) harbour porpoises did not habituate to the pinger over an 8-month period, (2) the pinger effect is very localized, and (3) pinger use did not lead to harbour porpoise displacement over the study period, suggesting an absence of long-term behavioral effects. We suggest that the deployment of pingers on fishing nets would likely reduce net-porpoise interactions, thereby mitigating bycatch of harbour porpoises and potentially other cetacean species. As the small-scale fishery dominates in United Kingdom waters, there is an acute need for cost-effective mitigation strategies with concurrent monitoring to be implemented rapidly in order to address the problem of harbour porpoise, and more generally, cetacean bycatch.

Considerations for transferring an operational dynamic ocean management tool between ocean color products

Welch H, Brodie S, Jacox MG, Robinson D, Wilson C, Bograd SJ, Oliver MJ, Hazen EL. Considerations for transferring an operational dynamic ocean management tool between ocean color products. Remote Sensing of Environment [Internet]. 2020 ;242:111753. Available from: https://www.sciencedirect.com/science/article/pii/S0034425720301231
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Satellite remote sensing data are critical for assessing ecosystem state and evaluating long-term trends and shifts in ecosystem components. Many operational tools rely on continuous streams of remote sensing data, and when a satellite sensor reaches the end of its designed lifespan, these tools must be transferred to a more reliable data stream. Transferring between data streams can produce discontinuities in tool products, and it is important to quantify these downstream impacts and understand the mechanisms that cause discontinuity. To illustrate the complexities of tool transfer, we compare five products for ocean chlorophyll-a, which is a proxy for phytoplankton biomass and an important input for tools that monitor marine biophysical processes. The five chlorophyll-a products included three blended products and two single sensor products from MODIS and VIIRS. We explored the downstream impacts of tool transfer using EcoCast: an operational dynamic ocean management tool that combines real-time predictions from target and bycatch species distribution models to produce integrated surfaces of fishing suitability. EcoCast was operationalized using MODIS chlorophyll-a, and we quantify the impacts of transferring to the intended replacement of MODIS, VIIRS, and test if impacts can be minimized by using a blended chlorophyll-a product instead. Differences between chlorophyll products did not linearly propagate through to the species model predictions and the integrated fishing suitability surfaces. Instead, differences in species model predictions were determined by the shape of chlorophyll-a response curves in the species models relative to chlorophyll-a differences between sensors. However, differences in the integrated fishing suitability surfaces were reduced by canceling of differences from individual species model predictions. Differences in the integrated fishing suitability surfaces were not reduced by transferring to a blended product, highlighting the complexity of transferring operational tools between different remote sensing data products. These results contribute to our general understanding of the mechanisms by which transferring between data streams impacts downstream products. To aid decision-making regarding tool transfer, we developed an interactive web application that allows end-users to explore differences in chlorophyll products within times period and regions of interest.

On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean

Parga ML, Crespo-Picazo JL, Monteiro D, García-Párraga D, Hernandez JA, Swimmer Y, Paz S, Stacy NI. On-board study of gas embolism in marine turtles caught in bottom trawl fisheries in the Atlantic Ocean. Scientific Reports [Internet]. 2020 ;10(1). Available from: https://www.nature.com/articles/s41598-020-62355-7
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Decompression sickness (DCS) was first diagnosed in marine turtles in 2014. After capture in net fisheries, animals typically start showing clinical evidence of DCS hours after being hauled on-board, often dying if untreated. These turtles are normally immediately released without any understanding of subsequent clinical problems or outcome. The objectives of this study were to describe early occurrence and severity of gaseous embolism (GE) and DCS in marine turtles after incidental capture in trawl gear, and to provide estimates of on-board and post-release mortality. Twenty-eight marine turtles were examined on-board fishing vessels. All 20 turtles assessed by ultrasound and/or post-mortem examination developed GE, independent of season, depth and duration of trawl and ascent speed. Gas emboli were obvious by ultrasound within 15 minutes after surfacing and worsened over the course of 2 hours. Blood data were consistent with extreme lactic acidosis, reduced glomerular filtration, and stress. Twelve of 28 (43%) animals died on-board, and 3 of 15 (20%) active turtles released with satellite tags died within 6 days. This is the first empirically-based estimate of on-board and post-release mortality of bycaught marine turtles that has until now been unaccounted for in trawl fisheries not equipped with turtle excluder devices.

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