Bycatch Estimates From a Pacific Tuna Longline Fishery Provide a Baseline for Understanding the Long-Term Benefits of a Large, Blue Water Marine Sanctuary

Abstract

Bycatch on pelagic tuna longlines has contributed to population declines in several far-ranging, oceanic species and presents a conservation challenge that area-based management tools are increasingly promoted to address. In January 2020 the Republic of Palau, concerned about the impacts of longline fishing in its waters, closed 80% of its exclusive economic zone to all extractive activities, reserving the remaining 20% for a domestic fishing zone (DFZ). One of a growing number of very large marine protected areas, the Palau National Marine Sanctuary (PNMS) spans ∼500,000 km2 and was established inter alia to allow for the recovery of fish stocks adversely impacted by tuna longline fleets. Given that the main tuna stocks targeted in the western Pacific are not overexploited, the benefits of protection potentially afforded by the sanctuary are likely greater for vulnerable bycatch species. Evaluations of the sanctuary’s performance require, in part, a baseline of historical catch rates and effort distribution in the distant-water fleet (DWF) and locally based fleet (LBF) operating in Palau prior to sanctuary implementation. We describe the fishing effort, catch rates, catch estimates and fishing mortality in Palau’s longline fishery based on logbook, observer and electronic monitoring data. We defined bycatch as any species, retained or discarded, other than targeted tunas. Between 2010 and 2020, 104.8 million hooks were deployed, catching over 2 million individuals from 117 taxa at an overall target:bycatch ratio of 1:1, with a retention rate of ∼62%. Pronounced differences in fishing strategies and spatial distribution of effort between fleets were associated with large variations in catch rates and composition. The LBF had a larger effect on populations of at-risk species relative to the DWF, with higher catch rates and magnitudes for several vulnerable species and higher observable fishing mortality rates (64% vs 50% in the DWF). The sanctuary reshaped Palau’s longline fishery, contracting the fishery’s area and capacity. The relocation of the DFZ eliminated the LBF and constrained the DWF to an area where the fleet’s total catch rates and those of a number of vulnerable species were historically lower relative to former fishing grounds now closed by the sanctuary. Our results highlight the importance of consistent bycatch monitoring and emphasize the need for regional area-based approaches for managing longline fisheries.

Are Italian consumers of canned tuna fish sensitive to environmentally sustainable product attributes?

“…The second sphere includes several environmental reasons that led the UN to officially designate May 2 as World Tuna Day: the reduction of world stocks, that are overfished or at risk of overfishing at least for some tuna species (FAO, 2021; ISSF, 2021); serious natural resource implications due to the fishing methods, resulting in bycatch of nontarget animals and undersized individuals of target species (Jaiteh et al. , 2021;Xie et al.…”

“…The second sphere includes several environmental reasons that led the UN to officially designate May 2 as World Tuna Day: the reduction of world stocks, that are overfished or at risk of overfishing at least for some tuna species (FAO, 2021;ISSF, 2021); serious natural resource implications due to the fishing methods, resulting in bycatch of nontarget animals and undersized individuals of target species (Jaiteh et al, 2021;Xieet al, 2021); the relevance of the environmental impacts along the global supply chain; and finally, the illegal, unreported and unregulated tuna fishing (ISSF, 2021). On the other hand, owing to marine pollution, tunas are exposed to mercury, persistent organic pollutants and to other harmful contaminants that pose health hazards that have been linked to tuna consumption (Miedico et al, 2020;Xie et al, 2021).…”

By-catch of sea turtles in Pacific artisanal fishery: Two points of view: From observer and fishers

“…The bycatch rates obtained in this study (4.3 turtles per 1,000 hooks) are comparable to those extrapolated from the results of Barragań et al (2009) in Machalilla National Parks (Ecuador), which are approximately 4.8 turtles per 1,000 hooks, or those reported by Whoriskey et al (2011) in Costa Rica's Pacific, where bycatch rates were 9.05 per 1000 hooks for olive ridley turtle and 0.35 per 1000 hooks for green turtles. On the other hand, they are relatively higher than those reported by Wang et al (2021) in the Pacific Ocean, Gilman et al (2007) in Hawaii longline fleet or Jaiteh et al (2021) in the western Pacific Ocean (Caroline Islands) with sea turtle bycatch rates ranging from 0 to 0.024/1,000 hooks, 0.094/1,000 hooks and 0.29/1,000 hooks, respectively.…”

Genetic assignment of fisheries bycatch reveals disproportionate mortality among Alaska Northern Fulmar breeding colonies

“…In our study, we show disproportionate take of fulmars from specific colonies in some of the largest fisheries in the United States and provide an example of how GSI can be applied to species with genetically structured populations, some of which are critically endangered. Global longline fisheries accidentally catch a variety of seabirds – notably, albatrosses (e.g., Jiménez et al, 2014 ; Melvin et al, 2019 ) and penguins (Crawford et al, 2017 ) – as well as sea turtles, elasmobranchs, and marine mammals (Jaiteh et al, 2021 ; Thorne et al, 2019 ). In many of these cases, characterizing population‐level impacts of bycatch require that animals are tracked or that a significant portion of the population is banded.…”