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Lakenarine R, Chhetri N, Chhetri N, Senko J. Characterization of small-scale net fisheries off the coast of Guyana. PLoS One 2024; 19:e0306332. [PMID: 38941279 PMCID: PMC11213293 DOI: 10.1371/journal.pone.0306332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 06/14/2024] [Indexed: 06/30/2024] Open
Abstract
Fish stocks have declined rapidly over the past half-century due to the increased demand for seafood and unsustainable fishing practices. The incidental capture of non-target species (bycatch) is a pervasive issue in fisheries management and has led to population declines in non-target species worldwide. The fisheries sector in Guyana currently supports the livelihoods of over 10,000 Guyanese and contributes approximately 2% to the country's GDP. Bycatch is believed to be a major threat to Guyana's marine fisheries, especially the small-scale sector, due to a lack of management infrastructure and limited data and monitoring. Here, we assessed bycatch in Guyana's artisanal gillnet and Chinese seine fisheries through vessel observations and semi-structured interviews with local fishers. Most of the discarded species documented had no commercial importance to the fisheries in Guyana. Although no statistical difference was observed among the bycatch rates in the gillnet and Chinese seine fisheries, the latter generally had more discarded individuals, most of which were juveniles. The Shannon-Weiner diversity index showed a greater diversity of bycatch species in the gillnet fisheries compared to the Chinese seine. Jaccard's similarity index indicated a low similarity among the gear types. Even though most fishers were aware of bycatch, they did not view it as a major issue and were not interested in reducing their discards. We recommend a collaborative approach in exploring solutions to ensure the ecological and socioeconomic sustainability of the fisheries sector.
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Affiliation(s)
- Rovindra Lakenarine
- School for the Future of Innovation in Society, College of Global Futures, Arizona State University, Tempe, Arizona, United States of America
- Department of Biology, Faculty of Natural Sciences, University of Guyana, Georgetown, Guyana
| | - Netra Chhetri
- School for the Future of Innovation in Society, College of Global Futures, Arizona State University, Tempe, Arizona, United States of America
| | - Neha Chhetri
- School for the Future of Innovation in Society, College of Global Futures, Arizona State University, Tempe, Arizona, United States of America
| | - Jesse Senko
- School for the Future of Innovation in Society, College of Global Futures, Arizona State University, Tempe, Arizona, United States of America
- School of Ocean Futures, College of Global Futures, Arizona State University, Tempe, Arizona, United States of America
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2
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Frantz BH, Sepúlveda M, García‐Reyes M, Vega R, Palacios DM, Bedriñana‐Romano L, Hückstädt LA, Santos‐Carvallo M, Davis JD, Hines E. Combining potential and realized distribution modeling of telemetry data for a bycatch risk assessment. Ecol Evol 2024; 14:e11541. [PMID: 38932966 PMCID: PMC11199131 DOI: 10.1002/ece3.11541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 05/12/2024] [Accepted: 05/20/2024] [Indexed: 06/28/2024] Open
Abstract
Establishing marine species distributions is essential for guiding management and can be estimated by identifying potential favorable habitat at a population level and incorporating individual-level information (e.g., movement constraints) to inform realized space use. In this research, we applied a combined modeling approach to tracking data of adult female and juvenile South American sea lions (Otaria flavescens; n = 9) from July to November 2011 to make habitat predictions for populations in northern Chile. We incorporated topographic and oceanographic predictors with sea lion locations and environmentally based pseudo-absences in a generalized linear model for estimating population-level distribution. For the individual approach, we used a generalized linear mixed-effects model with a negative exponential kernel variable to quantify distance-dependent movement from the colony. Spatial predictions from both approaches were combined in a bivariate color map to identify areas of agreement. We then used a GIS-based risk model to characterize bycatch risk in industrial and artisanal purse-seine fisheries based on fishing set data from scientific observers and artisanal fleet logs (2010-2015), the bivariate sea lion distribution map, and criteria ratings of interaction characteristics. Our results indicate population-level associations with productive, shallow, low slope waters, near to river-mouths, and with high eddy activity. Individual distribution was restricted to shallow slopes and cool waters. Variation between approaches may reflect intrinsic factors restricting use of otherwise favorable habitat; however, sample size was limited, and additional data are needed to establish the full range of individual-level distributions. Our bycatch risk outputs identified highest risk from industrial fisheries operating nearshore (within 5 NM) and risk was lower, overall, for the artisanal fleet. This research demonstrates the potential for integrating potential and realized distribution models within a spatial risk assessment and fills a gap in knowledge on this species' distribution, providing a basis for targeting bycatch mitigation outreach and interventions.
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Affiliation(s)
- Bethany H. Frantz
- School of the EnvironmentSan Francisco State UniversitySan FranciscoCaliforniaUSA
| | - Maritza Sepúlveda
- Centro de Investigación y Gestión de Recursos Naturales (CIGREN), Instituto de Biología, Facultad de CienciasUniversidad de ValparaísoValparaísoChile
- Núcleo Milenio de Salmónidos Invasores (INVASAL)Universidad de ConcepciónConcepciónChile
| | | | - Rodrigo Vega
- Instituto de Fomento Pesquero (IFOP)ValparaísoChile
| | - Daniel M. Palacios
- Marine Mammal InstituteOregon State UniversityNewportOregonUSA
- Department of Fisheries, Wildlife and Conservation SciencesOregon State UniversityNewportOregonUSA
| | - Luis Bedriñana‐Romano
- Instituto de Ciencias Marinas y Limnológicas, Facultad de CienciasUniversidad Austral de ChileCasilla, ValdiviaChile
- NGO Centro Ballena AzulValdiviaChile
- Centro de Investigación Oceanográfica COPAS CoastalUniversidad de ConcepciónConcepciónChile
| | - Luis A. Hückstädt
- Centre for Ecology and ConservationUniversity of ExeterCornwallUK
- Institute of Marine SciencesUniversity of California Santa CruzSanta CruzCaliforniaUSA
| | - Macarena Santos‐Carvallo
- Centro de Investigación y Gestión de Recursos Naturales (CIGREN), Instituto de Biología, Facultad de CienciasUniversidad de ValparaísoValparaísoChile
| | - Jerry D. Davis
- School of the EnvironmentSan Francisco State UniversitySan FranciscoCaliforniaUSA
| | - Ellen Hines
- School of the EnvironmentSan Francisco State UniversitySan FranciscoCaliforniaUSA
- Estuary & Ocean Science CenterSan Francisco State UniversityTiburonCaliforniaUSA
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3
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Di Lorenzo M, Calò A, Di Franco A, Milisenda G, Aglieri G, Cattano C, Milazzo M, Guidetti P. Small-scale fisheries catch more threatened elasmobranchs inside partially protected areas than in unprotected areas. Nat Commun 2022; 13:4381. [PMID: 35945205 PMCID: PMC9363485 DOI: 10.1038/s41467-022-32035-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 07/11/2022] [Indexed: 11/09/2022] Open
Abstract
Elasmobranchs are heavily impacted by fishing. Catch statistics are grossly underestimated due to missing data from various fishery sectors such as small-scale fisheries. Marine Protected Areas are proposed as a tool to protect elasmobranchs and counter their ongoing depletion. We assess elasmobranchs caught in 1,256 fishing operations with fixed nets carried out in partially protected areas within Marine Protected Areas and unprotected areas beyond Marine Protected Areas borders at 11 locations in 6 Mediterranean countries. Twenty-four elasmobranch species were recorded, more than one-third belonging to the IUCN threatened categories (Vulnerable, Endangered, or Critically Endangered). Catches per unit of effort of threatened and data deficient species were higher (with more immature individuals being caught) in partially protected areas than in unprotected areas. Our study suggests that despite partially protected areas having the potential to deliver ecological benefits for threatened elasmobranchs, poor small-scale fisheries management inside Marine Protected Areas could hinder them from achieving this important conservation objective.
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Affiliation(s)
- Manfredi Di Lorenzo
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology, Sicily Marine Center, Lungomare Cristoforo Colombo (complesso Roosevelt), 90149, Palermo, Italy.
| | - Antonio Calò
- Department of Earth and Marine sciences (DiSTeM), University of Palermo, Via Archirafi 20-22, 90123, Palermo, Italy
| | - Antonio Di Franco
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology, Sicily Marine Center, Lungomare Cristoforo Colombo (complesso Roosevelt), 90149, Palermo, Italy.
| | - Giacomo Milisenda
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology, Sicily Marine Center, Lungomare Cristoforo Colombo (complesso Roosevelt), 90149, Palermo, Italy
| | - Giorgio Aglieri
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology, Sicily Marine Center, Lungomare Cristoforo Colombo (complesso Roosevelt), 90149, Palermo, Italy
- Department of Earth and Marine sciences (DiSTeM), University of Palermo, Via Archirafi 20-22, 90123, Palermo, Italy
- CoNISMa, Piazzale Flaminio 9, 00196, Rome, Italy
| | - Carlo Cattano
- Stazione Zoologica Anton Dohrn, Department of Integrative Marine Ecology, Sicily Marine Center, Lungomare Cristoforo Colombo (complesso Roosevelt), 90149, Palermo, Italy
- Department of Earth and Marine sciences (DiSTeM), University of Palermo, Via Archirafi 20-22, 90123, Palermo, Italy
- CoNISMa, Piazzale Flaminio 9, 00196, Rome, Italy
| | - Marco Milazzo
- Department of Earth and Marine sciences (DiSTeM), University of Palermo, Via Archirafi 20-22, 90123, Palermo, Italy
- CoNISMa, Piazzale Flaminio 9, 00196, Rome, Italy
| | - Paolo Guidetti
- Department of Integrative Marine Ecology (EMI), Stazione Zoologica Anton Dohrn-National Institute of Marine Biology, Ecology and Biotechnology, Genoa Marine Centre, 16126, Genoa, Italy
- National Research Council, Institute for the Study of Anthropic Impact and sustainability in the Marine Environment (CNR-IAS), Via de Marini 6, 16149, Genova, Italy
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Shiode D, Shiozawa M, Hu F, Tokai T, Hirai Y. A newly developed soft-type turtle releasing device (Soft-TRD) for setnet fisheries. AQUACULTURE AND FISHERIES 2021. [DOI: 10.1016/j.aaf.2020.06.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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5
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A 20-year gap evaluation of the population biology of the crab Hepatus pudibundus in an area overexploited by fisheries. Biologia (Bratisl) 2021. [DOI: 10.2478/s11756-020-00528-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Luck C, Jessopp M, Tully O, Cosgrove R, Rogan E, Cronin M. Estimating protected species bycatch from limited observer coverage: A case study of seal bycatch in static net fisheries. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01213] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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7
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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 2020; 15:e0237835. [PMID: 32817725 PMCID: PMC7446845 DOI: 10.1371/journal.pone.0237835] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 08/04/2020] [Indexed: 11/25/2022] Open
Abstract
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.
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Affiliation(s)
- Gregory M. Verutes
- Faculty of Political and Social Sciences, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
- Campus Do*Mar, International Campus of Excellence, Vigo, Spain
- * E-mail:
| | - Andrew F. Johnson
- MarFishEco Fisheries Consultants, Edinburgh, United Kingdom
- The Lyell Centre, Institute of Life and Earth Sciences, School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, United Kingdom
| | | | | | - Cindy Peter
- Institute of Biodiversity and Environmental Conservation, University Malaysia Sarawak, Sarawak, Malaysia
| | - Long Vu
- Vietnam Marine Megafauna Network, Center for Biodiversity Conservation and Endangered Species, Ho Chi Minh, Vietnam
| | | | - Rebecca L. Lewison
- Department of Biology, San Diego State University, San Diego, CA, United States of America
| | - Ellen M. Hines
- Estuary & Ocean Science Center, San Francisco State University, Tiburon, CA, United States of America
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8
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Choi E, Charles KE, Charles KL, Stewart KM, Morrall CE, Dennis MM. Leatherback Sea Turtle (Dermochelys coriacea) Embryo and Hatchling Pathology in Grenada, with Comparison to St. Kitts. CHELONIAN CONSERVATION AND BIOLOGY 2020. [DOI: 10.2744/ccb-1395.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Esther Choi
- Center for Conservation Medicine and Ecosystem Health, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, St. Kitts, West Indies [; ; ]
| | | | | | - Kimberly M. Stewart
- Center for Conservation Medicine and Ecosystem Health, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, St. Kitts, West Indies [; ; ]
| | | | - Michelle M. Dennis
- Center for Conservation Medicine and Ecosystem Health, Ross University School of Veterinary Medicine, PO Box 334, Basseterre, St. Kitts, West Indies [; ; ]
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9
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Hines E, Ponnampalam LS, Junchompoo C, Peter C, Vu L, Huynh T, Caillat M, Johnson AF, Minton G, Lewison RL, Verutes GM. Getting to the bottom of bycatch: a GIS-based toolbox to assess the risk of marine mammal bycatch. ENDANGER SPECIES RES 2020. [DOI: 10.3354/esr01037] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Marine mammal bycatch poses a particular challenge in developing countries, where data to document bycatch and its effects are often lacking. Using the Bycatch Risk Assessment (ByRA) toolkit, based on InVEST open-source models, we chose 4 field sites in Southeast Asia with varying amounts of data on marine mammals and fishing occurrence: Trat province in the eastern Gulf of Thailand, the Sibu-Tinggi Islands and Kuching Bay, Malaysia, and Kien Giang Biosphere Reserve in southwestern Vietnam. These field sites have similar species of coastal marine mammals, small-scale and commercial fisheries, and support for research from universities and/or management. In Thailand and Kuching, results showed changing patterns of fishing and Irrawaddy dolphin Orcaella brevirostris habitat use across seasons, showing how bycatch risk could change throughout the year. Risk maps for dugongs Dugong dugon in peninsular Malaysia highlighted patterns of bycatch risk concentrated around a mainland fishing pier, and revealed high risk in a northern subregion. In Vietnam, first maps of bycatch risk for the Irrawaddy dolphin showed the highest risk driven by intensive use of gillnets and trawling gear. ByRA pinpointed areas of spatial and seasonal bycatch exposure, and estimated the consequence of bycatch on local species, providing managers with critical information on where to focus bycatch mitigation and meet new global standards for US Marine Mammal Protection Act and other international regulation (e.g. Official Journal of the European Union 2019; Regulation 2019/1241) compliance. The toolbox, a transferable open-source tool, can be used to guide fisheries management, marine mammal conservation, spatial planning, and further research.
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Affiliation(s)
- E Hines
- Estuary & Ocean Science Center, and Department of Geography & Environment, San Francisco State University, Tiburon, CA 94920, USA
| | - LS Ponnampalam
- The MareCet Research Organization, 5, Jalan USJ 12/1B 47630 Subang Jaya, Selangor, Malaysia
| | - C Junchompoo
- Department of Marine and Coastal Resources, Ministry of Natural Resources and Environment, Chaeng Watthana Road, Lak Si District, Bangkok 10210, Thailand
| | - C Peter
- Universiti Malaysia Sarawak, Jalan Datuk Mohammad Musa, 94300 Kota Samarahan, Sarawak, Malaysia
| | - L Vu
- Vietnam Marine Megafauna Network, Center for Biodiversity Conservation and Endangered Species, 24, Street No 13, Lakeview City, Ho Chi Minh City, Vietnam
| | - T Huynh
- Southern Institute of Ecology, Vietnam Academy of Science and Technology, 01 Mac Dinh Chi, Ben Nghe, District 1, Ho Chi Minh City, Vietnam
- Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa, Ishikawa 920-1164, Japan
| | - M Caillat
- Environmental Defense Fund, San Francisco, CA 94105, USA
| | - AF Johnson
- MarFishEco Fisheries Consultants, 67/6 Brunswick Street, Edinburgh EH7 5HT, UK
- The Lyell Centre, Institute of Life and Earth Sciences, School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University, Edinburgh, EH14 4AS, UK
| | - G Minton
- Megaptera Marine Conservation, Laan van Rhemen van Rhemenshuizen 14, 2242 PT Wassenaar, The Netherlands
| | - RL Lewison
- Department of Biology, San Diego State University, CA 92182, USA
| | - GM Verutes
- Faculty of Political and Social Sciences, Universidade de Santiago de Compostela, Praza do Obradoiro, 0, 15705 Santiago de Compostela, A Coruña, Spain
- Campus Do*Mar, International Campus of Excellence, 36310 Vigo, Spain
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10
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Peltier H, Authier M, Dabin W, Dars C, Demaret F, Doremus G, Canneyt OV, Laran S, Mendez-Fernandez P, Spitz J, Daniel P, Ridoux V. Can modelling the drift of bycaught dolphin stranded carcasses help identify involved fisheries? An exploratory study. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2019.e00843] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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11
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Cruz MJ, Machete M, Menezes G, Rogan E, Silva MA. Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores. PeerJ 2018; 6:e4285. [PMID: 29456883 PMCID: PMC5813588 DOI: 10.7717/peerj.4285] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 01/01/2018] [Indexed: 11/20/2022] Open
Abstract
Small-scale artisanal fisheries can have a significant negative impact in cetacean populations. Cetacean bycatch has been documented in the pole-and-line tuna fishery in the Azores with common dolphins being the species more frequently taken. Based on data collected by observers on ∼50% of vessels operating from 1998 to 2012, we investigate the influence of various environmental and fisheries-related factors in common dolphin bycatch and calculate fleet-wide estimates of total bycatch using design-based and model-based methods. Over the 15-year study dolphin bycatch occurred in less than 0.4% of the observed fishing events. Generalized additive modelling results suggest a significant relationship between common dolphin bycatch and duration of fishing events, sea surface temperature and location. Total bycatch calculated from the traditional stratified ratio estimation approach was 196 (95% CI: 186–205), while the negative binomial GAM estimated 262 (95% CI: 249–274) dolphins. Bycatch estimates of common dolphin were similar using statistical approaches suggesting that either of these methods may be used in future bycatch assessments for this fishery. Our work shows that rates of common dolphin bycatch in the pole-and-line tuna fishery in the Azores are low, despite considerable variations between years. Dolphins caught were released alive although the fate of these individuals is unknown. Continued monitoring will provide a better understanding of dolphin bycatch and more accurate estimates essential in the development of potential mitigation measures.
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Affiliation(s)
- Maria João Cruz
- Departamento de Oceanografia e Pescas, Universidade dos Açores, Horta, Açores, Portugal.,MARE-Marine and Environmental Sciences Centre and IMAR-Instituto do Mar, Universidade dos Açores, Horta, Açores, Portugal
| | - Miguel Machete
- MARE-Marine and Environmental Sciences Centre and IMAR-Instituto do Mar, Universidade dos Açores, Horta, Açores, Portugal
| | - Gui Menezes
- Departamento de Oceanografia e Pescas, Universidade dos Açores, Horta, Açores, Portugal.,MARE-Marine and Environmental Sciences Centre and IMAR-Instituto do Mar, Universidade dos Açores, Horta, Açores, Portugal
| | - Emer Rogan
- School of Biological, Earth and Environmental Sciences, University College Cork, Enterprise Centre, Distillery Fields, North Mall, Cork, Ireland
| | - Mónica A Silva
- MARE-Marine and Environmental Sciences Centre and IMAR-Instituto do Mar, Universidade dos Açores, Horta, Açores, Portugal.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
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12
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Kacev D, Sippel TJ, Kinney MJ, Pardo SA, Mull CG. An Introduction to Modelling Abundance and Life History Parameters in Shark Populations. ADVANCES IN MARINE BIOLOGY 2017; 78:45-87. [PMID: 29056143 DOI: 10.1016/bs.amb.2017.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Elasmobranchs play critically important ecological roles throughout the world's oceans, yet in many cases, their slow life histories and interactions with fisheries makes them particularly susceptible to exploitation. Management for these species requires robust scientific input, and mathematical models are the backbone of science-based management. In this chapter, we provide an introductory overview of the use of mathematical models to estimate shark abundance. First, we discuss life history models that are used to understand the basic biology of elasmobranchs. Second, we cover population dynamics models, which are used to make inferences regarding population trend, size, and risk of extinction. Finally, we provide examples of applied models used to assess the status of elasmobranchs in the Northeast Pacific Ocean to guide management for these species. This chapter is not a comprehensive review of quantitative methods, but rather introduces various mathematical tools in fisheries management, with a focus on shark management in the Northeast Pacific Ocean.
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Affiliation(s)
- Dovi Kacev
- Ocean Associates, Inc., Arlington, VA, United States.
| | | | | | - Sebastián A Pardo
- Earth to Ocean Research Group, Simon Fraser University, Burnaby, BC, Canada
| | - Christopher G Mull
- Earth to Ocean Research Group, Simon Fraser University, Burnaby, BC, Canada
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13
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Paso Viola MN, Riccialdelli L, Negri MF, Panebianco MV, Panarello HO, Cappozzo HL. Intra-specific isotope variations of franciscana dolphin Pontoporia blainvillei regarding biological parameters and distinct environments. Mamm Biol 2017. [DOI: 10.1016/j.mambio.2017.03.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Lopes K, Passos L, Rodrigues JG, Koenen F, Stiebens V, Székely T, Dutra A. Sea Turtle, Shark, and Dolphin Bycatch Rates by Artisanal and Semi-Industrial Fishers in Maio Island, Cape Verde. CHELONIAN CONSERVATION AND BIOLOGY 2016. [DOI: 10.2744/cb-1213.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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15
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Vanstreels RE, Hurtado R, Ewbank AC, Bertozzi CP, Catão-Dias JL. Lesions associated with drowning in bycaught penguins. DISEASES OF AQUATIC ORGANISMS 2016; 121:241-248. [PMID: 27786162 DOI: 10.3354/dao03052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Fisheries bycatch, the incidental mortality that occurs as a result of entanglement in fishing gear, is an important conservation threat to penguins and other seabirds. Identification of entanglement and drowning in beach-cast carcasses of seabirds remains a challenge, as it is still unclear what lesions are to be expected in a bycaught seabird. We necropsied 2 Magellanic penguins Spheniscus magellanicus that were entangled and drowned in gillnets. Marked distension of the lungs with foamy red fluid and marked oedema of the dorsal visceral pleura were prominent lesions consistent with those described in cases of 'wet drowning' in humans. On the other hand, the air sacs contained very small quantities of liquid, suggesting that absence of water in the air sacs might not be a reliable sign to exclude drowning. Other relevant findings included cutaneous lacerations and bruising in one bird and cervical and pectoral rhabdomyolysis in both birds. While cutaneous or subcutaneous hematomas may be an indication of bycatch, especially if linear or cross-linear patterns consistent with fishing nets are present, these lesions might not always be discernible and their absence does not suffice to exclude the possibility of entanglement in fishing nets. Additionally, our findings suggest that the histological examination of skeletal muscles, particularly of the neck, may provide additional clues to corroborate the diagnosis of drowning in penguins.
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Affiliation(s)
- Ralph Eric Vanstreels
- Laboratory of Wildlife Comparative Pathology (LAPCOM), School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, 05508-270 SP, Brazil
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McDonald SL, Lewison RL, Read AJ. Evaluating the efficacy of environmental legislation: A case study from the US marine mammal Take Reduction Planning process. Glob Ecol Conserv 2016. [DOI: 10.1016/j.gecco.2015.11.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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17
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18
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Zimmerhackel JS, Schuhbauer AC, Usseglio P, Heel LC, Salinas-de-León P. Catch, bycatch and discards of the Galapagos Marine Reserve small-scale handline fishery. PeerJ 2015; 3:e995. [PMID: 26082874 PMCID: PMC4465951 DOI: 10.7717/peerj.995] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 05/12/2015] [Indexed: 02/03/2023] Open
Abstract
Fisheries bycatch is a significant marine conservation issue as valuable fish are wasted and protected species harmed with potential negative ecological and socio-economic consequences. Even though there are indications that the small-scale handline fishery of the Galapagos Marine Reserve has a low selectivity, information on its bycatch has never been published. We used onboard monitoring and interview data to assess the bycatch of the Galapagos handline fishery by estimating the bycatch ratio, determining species compositions of landings and bycatch, identifying fishers’ reasons for discarding certain individuals, and revealing historical trends in the bycatch ratio. The estimated bycatch ratio as a function of biomass of 0.40 and a diverse species composition of target catch and bycatch confirmed the low selectivity of this fishery. Most individuals were not landed for economic motivations, either because species (77.4%) or sizes (17.7%) are unmarketable or for regulatory reasons (5.9%). We found that bycatch contributes to growth overfishing of some target species because they are discarded or used as bait before reaching their first maturity. Moreover, over half of interviewees perceived a historical decrease in bycatch ratios that was explained by a diversification of the target catch due to the reduction in abundance of the traditionally most important target species. As some target species show signs of overfishing and to date there are no specific regulations for the finfish fishery species in place, we recommend the implementation of a series of management measures to protect critical life stages of overexploited species and to improve the selectivity of the Galapagos handline fishery.
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Affiliation(s)
- Johanna S Zimmerhackel
- Department of Marine Science, Charles Darwin Research Station , Puerto Ayora, Galapagos Islands , Ecuador
| | - Anna C Schuhbauer
- Department of Marine Science, Charles Darwin Research Station , Puerto Ayora, Galapagos Islands , Ecuador ; Fisheries Center, Fisheries Economic Research Unit, The University of British Columbia , Vancouver, British Columbia , Canada
| | - Paolo Usseglio
- Fisheries Ecology Research Lab, University of Hawaii at Manoa , Hawaii , USA ; Fundación In-Nova , Toledo, Castilla la Mancha , Spain
| | - Lena C Heel
- Department of Marine Science, Charles Darwin Research Station , Puerto Ayora, Galapagos Islands , Ecuador ; Institute of Ecology and Environmental Chemistry, Leuphana University Lüneburg , Lüneburg , Germany ; Leibniz Center for Tropical Marine Ecology , Bremen , Germany
| | - Pelayo Salinas-de-León
- Department of Marine Science, Charles Darwin Research Station , Puerto Ayora, Galapagos Islands , Ecuador
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Oksanen SM, Ahola MP, Oikarinen J, Kunnasranta M. A novel tool to mitigate by-catch mortality of baltic seals in coastal fyke net fishery. PLoS One 2015; 10:e0127510. [PMID: 25993534 PMCID: PMC4436298 DOI: 10.1371/journal.pone.0127510] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 04/16/2015] [Indexed: 11/18/2022] Open
Abstract
Developing methods to reduce the incidental catch of non-target species is important, as by-catch mortality poses threats especially to large aquatic predators. We examined the effectiveness of a novel device, a "seal sock", in mitigating the by-catch mortality of seals in coastal fyke net fisheries in the Baltic Sea. The seal sock developed and tested in this study was a cylindrical net attached to the fyke net, allowing the seals access to the surface to breathe while trapped inside fishing gear. The number of dead and live seals caught in fyke nets without a seal sock (years 2008-2010) and with a sock (years 2011-2013) was recorded. The seals caught in fyke nets were mainly juveniles. Of ringed seals (Phoca hispida botnica) both sexes were equally represented, while of grey seals (Halichoerus grypus) the ratio was biased (71%) towards males. All the by-caught seals were dead in the fyke nets without a seal sock, whereas 70% of ringed seals and 11% of grey seals survived when the seal sock was used. The seal sock proved to be effective in reducing the by-catch mortality of ringed seals, but did not perform as well with grey seals.
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Affiliation(s)
- Sari M. Oksanen
- Department of Biology, University of Eastern Finland, Joensuu, Finland
- * E-mail:
| | | | | | - Mervi Kunnasranta
- Department of Biology, University of Eastern Finland, Joensuu, Finland
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20
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Colman LP, Sampaio CLS, Weber MI, de Castilhos JC. Diet of Olive Ridley Sea Turtles,Lepidochelys olivacea,in the Waters of Sergipe, Brazil. CHELONIAN CONSERVATION AND BIOLOGY 2014. [DOI: 10.2744/ccb-1061.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Soykan CU, Eguchi T, Kohin S, Dewar H. Prediction of fishing effort distributions using boosted regression trees. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2014; 24:71-83. [PMID: 24640535 DOI: 10.1890/12-0826.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Concerns about bycatch of protected species have become a dominant factor shaping fisheries management. However, efforts to mitigate bycatch are often hindered by a lack of data on the distributions of fishing effort and protected species. One approach to overcoming this problem has been to overlay the distribution of past fishing effort with known locations of protected species, often obtained through satellite telemetry and occurrence data, to identify potential bycatch hotspots. This approach, however, generates static bycatch risk maps, calling into question their ability to forecast into the future, particularly when dealing with spatiotemporally dynamic fisheries and highly migratory bycatch species. In this study, we use boosted regression trees to model the spatiotemporal distribution of fishing effort for two distinct fisheries in the North Pacific Ocean, the albacore (Thunnus alalunga) troll fishery and the California drift gillnet fishery that targets swordfish (Xiphias gladius). Our results suggest that it is possible to accurately predict fishing effort using < 10 readily available predictor variables (cross-validated correlations between model predictions and observed data -0.6). Although the two fisheries are quite different in their gears and fishing areas, their respective models had high predictive ability, even when input data sets were restricted to a fraction of the full time series. The implications for conservation and management are encouraging: Across a range of target species, fishing methods, and spatial scales, even a relatively short time series of fisheries data may suffice to accurately predict the location of fishing effort into the future. In combination with species distribution modeling of bycatch species, this approach holds promise as a mitigation tool when observer data are limited. Even in data-rich regions, modeling fishing effort and bycatch may provide more accurate estimates of bycatch risk than partial observer coverage for fisheries and bycatch species that are heavily influenced by dynamic oceanographic conditions.
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Raby GD, Donaldson MR, Nguyen VM, Taylor MK, Sopinka NM, Cook KV, Patterson DA, Robichaud D, Hinch SG, Cooke SJ. Bycatch mortality of endangered coho salmon: impacts, solutions, and aboriginal perspectives. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2014; 24:1803-1819. [PMID: 29210239 DOI: 10.1890/13-1885.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We used biotelemetry and human dimensions surveys to explore potential solutions to migration mortality of an endangered population of coho salmon caught as bycatch in an aboriginal beach seine fishery. From 2009 to 2011, 182 wild coho salmon caught as bycatch in the lower Fraser River (Canada) were radio-tagged and tracked as they attempted to complete their migrations to natal spawning areas over 300 km upstream. Failure to survive to reach terminal radio receiving stations averaged 39% over three years. This mortality estimate is low compared to those obtained from telemetry studies on other salmon fisheries in the Fraser River. However, this value is markedly higher than the mortality estimate currently used to manage the fishery's impact. It is also in contrast to the perceptions of the majority of aboriginal fishers, who did not think survival of coho salmon is affected by capture and release from their fishery. Increased probability of survival was associated with lower reflex impairment, which is consistent with previous findings. Reflex impairment was positively correlated with entanglement time, suggesting that greater efforts by the fishers to release bycatch from their nets quickly would minimize post-release mortality. Survey responses by aboriginal fishers also suggested that they are receptive to employing new bycatch handling methods if they are shown to increase post-release survival. However, attempts to facilitate revival of a subset of captured fish using cylindrical in-river recovery bags did not improve migration success. Fisheries managers could use the new information from this study to better quantify impacts and evaluate different harvest options. Since aboriginal fishers were receptive to using alternate handling methods, efforts to improve knowledge on minimizing reflex impairment through reductions in handling time could help increase bycatch survival. Such a direct integration of social science and applied ecology is a novel approach to understanding conservation issues that can better inform meaningful actions to promote species recovery.
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Jannot JE, Holland DS. Identifying ecological and fishing drivers of bycatch in a U.S. groundfish fishery. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2013; 23:1645-1658. [PMID: 24261046 DOI: 10.1890/12-2225.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Fisheries bycatch is driven by both ecological (e.g., area, season) and social (e.g., fisher behavior) factors that are often difficult to disentangle. We demonstrate a method for comparing fishery-dependent bycatch to fishery-independent catch to delineate the influence of ecological and social factors on bycatch and provide insights for bycatch management. We used data from commercial fishing vessels in the U.S. west coast trawl groundfish fishery (fishery-dependent data collected by fisheries observers) and scientific data from the U.S. west coast bottom trawl groundfish survey (fishery-independent data) to compare the relative effects of season, time of day, target group, depth, and latitude on the expected catch of 12 bycatch species of management interest. This comparison highlights two important relationships that help identify drivers of bycatch. First, when the effect of season, time of day, depth, or latitude on bycatch in both the commercial and scientific data is positive, ecological processes are likely strong drivers of bycatch, suggesting technical approaches (e.g., temporal or spatial closures, gear modifications) might effectively control bycatch. Alternatively, when the effects of season, time of day, depth, latitude, or target group appear only in the commercial data (but not in survey data), fisher behavior is likely the stronger driver of bycatch, suggesting a need to strengthen incentives for fishers to change behavior to avoid bycatch (e.g., regulatory quotas). Two other patterns emerge that suggest that fishery bycatch is not associated with temporal, target, or spatial variables, implying that either current incentives to avoid bycatch are working (i.e., when survey expected catch is positively correlated with variables, but fishery catch is not) or bycatch is a product of unstudied or stochastic processes (i.e., variables are not correlated with expected catch in either data set) and continued monitoring is recommended. Our analysis provides managers and fishers with a basic analytical framework to assess bycatch reduction alternatives and methods useful for researchers interested in comparing bycatch before and after a management shift.
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Affiliation(s)
- Jason E Jannot
- Fisheries Resource and Analysis Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Boulevard East, Seattle, Washington 98112, USA.
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LeDain MRK, Larocque SM, Stoot LJ, Cairns NA, Blouin-Demers G, Cooke SJ. Assisted Recovery Following Prolonged Submergence in Fishing Nets Can Be Beneficial to Turtles: An Assessment with Blood Physiology and Reflex Impairment. CHELONIAN CONSERVATION AND BIOLOGY 2013. [DOI: 10.2744/ccb-1022.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Snape RTE, Beton D, Broderick AC, Çiçek BA, Fuller WJ, Özden Ö, Godley BJ. Strand Monitoring and Anthropological Surveys Provide Insight into Marine Turtle Bycatch in Small-Scale Fisheries of the Eastern Mediterranean. CHELONIAN CONSERVATION AND BIOLOGY 2013. [DOI: 10.2744/ccb-1008.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract
AbstractThere is growing awareness that small-scale fisheries may have large impacts on threatened marine fauna. Bycatch of small cetaceans by the Peruvian small-scale driftnet fleet results in the deaths of thousands of animals annually. We sought to assess the effectiveness of acoustic alarms (pingers) for reducing the incidental capture of dolphins and porpoises by this fleet. Forty-three experimental trips (156 fishing sets) and 47 control trips (195 fishing sets) out of Salaverry Port, northern Peru, were observed from April 2009 to August 2011. Twenty-two percent of control sets captured small cetaceans (67 individuals) and 16% of experimental sets had captures of small cetaceans (33 individuals). The bycatch rate of experimental sets was 0.50 individuals km−2h−1, whereas for control sets the rate was 0.80 individuals km−2h−1. This 37% reduction in bycatch rate suggests that pingers may be effective in reducing the bycatch of small cetaceans in this fishery. Catch rates of the fishery's target shark and ray species were unchanged. Given the vast size of this fishery and its current levels of bycatch of small cetaceans (> 10,000 individuals annually), even the modest declines in bycatch we observed could result in reductions in mortality of hundreds or thousands of small cetaceans per annum. Challenges, including increased costs, to large-scale utilization of pingers have yet to be overcome. The harpooning of dolphins for use as bait will also need to be addressed for further reductions in dolphin and porpoise bycatch and mortality to be achievable.
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Koch V, Peckham H, Mancini A, Eguchi T. Estimating at-sea mortality of marine turtles from stranding frequencies and drifter experiments. PLoS One 2013; 8:e56776. [PMID: 23483880 PMCID: PMC3577704 DOI: 10.1371/journal.pone.0056776] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 01/15/2013] [Indexed: 11/19/2022] Open
Abstract
Strandings of marine megafauna can provide valuable information on cause of death at sea. However, as stranding probabilities are usually very low and highly variable in space and time, interpreting the results can be challenging. We evaluated the magnitude and distribution of at-sea mortality of marine turtles along the Pacific coast of Baja California Sur, México during 2010–11, using a combination of counting stranded animals and drifter experiments. A total of 594 carcasses were found during the study period, with loggerhead (62%) and green turtles (31%) being the most common species. 87% of the strandings occurred in the southern Gulf of Ulloa, a known hotspot of loggerhead distribution in the Eastern Pacific. While only 1.8% of the deaths could be definitively attributed to bycatch (net marks, hooks), seasonal variation in stranding frequencies closely corresponded to the main fishing seasons. Estimated stranding probabilities from drifter experiments varied among sites and trials (0.05–0.8), implying that only a fraction of dead sea turtles can be observed at beaches. Total mortality estimates for 15-day periods around the floater trials were highest for PSL, a beach in the southern Gulf of Ulloa, ranging between 11 sea turtles in October 2011 to 107 in August 2010. Loggerhead turtles were the most numerous, followed by green and olive ridley turtles. Our study showed that drifter trials combined with beach monitoring can provide estimates for death at sea to measure the impact of small-scale fisheries that are notoriously difficult to monitor for by-catch. We also provided recommendations to improve the precision of the mortality estimates for future studies and highlight the importance of estimating impacts of small–scale fisheries on marine megafauna.
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Affiliation(s)
- Volker Koch
- Department of Marine Biology, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico.
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Wallace BP, Kot CY, DiMatteo AD, Lee T, Crowder LB, Lewison RL. Impacts of fisheries bycatch on marine turtle populations worldwide: toward conservation and research priorities. Ecosphere 2013. [DOI: 10.1890/es12-00388.1] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Rees ALF, Al-Kiyumi A, Broderick AC, Papathanasopoulou N, Godley BJ. Each to Their Own: Inter-Specific Differences in Migrations of Masirah Island Turtles. CHELONIAN CONSERVATION AND BIOLOGY 2012. [DOI: 10.2744/ccb-1000.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Larocque SM, Watson P, Blouin-Demers G, Cooke SJ. Accidental bait: do deceased fish increase freshwater turtle bycatch in commercial fyke nets? ENVIRONMENTAL MANAGEMENT 2012; 50:31-38. [PMID: 22543581 DOI: 10.1007/s00267-012-9868-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 04/03/2012] [Indexed: 05/31/2023]
Abstract
Bycatch of turtles in passive inland fyke net fisheries has been poorly studied, yet bycatch is an important conservation issue given the decline in many freshwater turtle populations. Delayed maturity and low natural adult mortality make turtles particularly susceptible to population declines when faced with additional anthropogenic adult mortality such as bycatch. When turtles are captured in fyke nets, the prolonged submergence can lead to stress and subsequent drowning. Fish die within infrequently checked passive fishing nets and dead fish are a potential food source for many freshwater turtles. Dead fish could thus act as attractants and increase turtle captures in fishing nets. We investigated the attraction of turtles to decomposing fish within fyke nets in eastern Ontario. We set fyke nets with either 1 kg of one-day or five-day decomposed fish, or no decomposed fish in the cod-end of the net. Decomposing fish did not alter the capture rate of turtles or fish, nor did it alter the species composition of the catch. Thus, reducing fish mortality in nets using shorter soak times is unlikely to alter turtle bycatch rates since turtles were not attracted by the dead fish. Interestingly, turtle bycatch rates increased as water temperatures did. Water temperature also influences turtle mortality by affecting the duration turtles can remain submerged. We thus suggest that submerged nets to either not be set or have reduced soak times in warm water conditions (e.g., >20 °C) as turtles tend to be captured more frequently and cannot withstand prolonged submergence.
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Affiliation(s)
- Sarah M Larocque
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
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Small-scale gill-net fisheries cause massive green turtle Chelonia mydas mortality in Baja California Sur, Mexico. ORYX 2011. [DOI: 10.1017/s0030605310001833] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AbstractThe coastal waters of Baja California Sur, Mexico, include some of the most important foraging grounds of the East Pacific green turtle Chelonia mydas. However, they are also important fishing grounds for artisanal fleets, leading potentially to high levels of bycatch mortality. We studied the impact of a small-scale gill-net fishery at San Ignacio lagoon, north-west Mexico, an important green turtle feeding ground. We conducted mortality censuses and interviewed local fishers to estimate total bycatch mortality at the lagoon. We also used marked drifters and carcasses to estimate stranding probabilities of turtles taken as bycatch. During 2006–2009 we found 262 dead turtles; 96% of the mortality occurred in May–August corresponding to the fishing season for halibut Paralichthys californicus and guitar-fish (Rhinobatus sp.). Stranding probability estimated from drifters was 0.062 (95% confidence interval, CI, 0.035–0.094), yielding a minimum mortality of 3,516 turtles during 2006–2008 (95% CI 2,364–6,057) or 1,172 animals per year. This is probably an underestimate of real mortality as the drifters have higher stranding probabilities than carcasses and most of the nets were set in the lower lagoon where carcasses rarely strand. Interviews with local fishers yielded a similar estimate of 1,087 (95% CI 901–1,286) dead turtles per year. This study is emblematic of the impact of artisanal fleets on marine turtles caused by overlap of fishing and turtle feeding areas. In 2009 strandings declined by > 97%, resulting from a change in fishing practices because of increased vigilance by enforcement authorities, underscoring the importance of law enforcement to protect threatened species.
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Larocque SM, Colotelo AH, Cooke SJ, Blouin-Demers G, Haxton T, Smokorowski KE. Seasonal patterns in bycatch composition and mortality associated with a freshwater hoop net fishery. Anim Conserv 2011. [DOI: 10.1111/j.1469-1795.2011.00487.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
| | - A. H. Colotelo
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology; Carleton University; Ottawa; ON; Canada
| | | | | | - T. Haxton
- Ontario Ministry of Natural Resources; Southern Science & Information Section; Peterborough; ON; Canada
| | - K. E. Smokorowski
- Fisheries and Oceans Canada; Great Lakes Laboratory for Fisheries and Aquatic Sciences; Sault Ste. Marie; ON; Canada
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Alfaro-Shigueto J, Mangel JC, Bernedo F, Dutton PH, Seminoff JA, Godley BJ. Small-scale fisheries of Peru: a major sink for marine turtles in the Pacific. J Appl Ecol 2011. [DOI: 10.1111/j.1365-2664.2011.02040.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Raby GD, Colotelo AH, Blouin-Demers G, Cooke SJ. Freshwater Commercial Bycatch: An Understated Conservation Problem. Bioscience 2011. [DOI: 10.1525/bio.2011.61.4.7] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Abstract
AbstractTurtle trade in the fish markets of Alexandria was reported up to the late 1990s, motivating conservation initiatives and enforcement of legal protection. To assess the current trade and bycatch levels in Alexandria and other ports we carried out an interview survey of 445 people in 2007, mostly fishermen and fishmongers, in 15 coastal cities and fishing ports along the Mediterranean coast of Egypt. The declared catch rates and official fishing fleet statistics suggest that captures of loggerhead Caretta caretta and green turtles Chelonia mydas are in the order of several thousands per year, possibly > 7,000 per year, mainly from trawling, longlining and set nets. Probably several hundred turtles die each year as a consequence of the high mortality rates typical of these fishing gears. In addition, most fishermen from Alexandria and some fishermen from other regions declared that they kill turtles for meat. Regulations and enforcement appear to be ineffective, as turtles are usually killed and consumed on board or only their meat is landed. Some turtles are still traded on the black market in some Alexandria fish markets. The overall mortality probably represents an unsustainable toll on the Mediterranean loggerhead and green turtle populations, and the perception of fishermen is that turtle numbers are declining. Mitigating the identified threats is thus urgent. In particular, intentional killing should be tackled through its cultural drivers, and measures to reduce bycatch mortality need to be tested and implemented.
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Humber F, Godley BJ, Ramahery V, Broderick AC. Using community members to assess artisanal fisheries: the marine turtle fishery in Madagascar. Anim Conserv 2010. [DOI: 10.1111/j.1469-1795.2010.00413.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wallace BP, Lewison RL, McDonald SL, McDonald RK, Kot CY, Kelez S, Bjorkland RK, Finkbeiner EM, Helmbrecht S, Crowder LB. Global patterns of marine turtle bycatch. Conserv Lett 2010. [DOI: 10.1111/j.1755-263x.2010.00105.x] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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