Using fisher‐contributed secondary fins to fill critical shark‐fisheries data gaps

Abstract

Developing-world shark fisheries are typically not assessed or actively managed for sustainability; one fundamental obstacle is the lack of species and size-composition catch data. We tested and implemented a new and potentially widely applicable approach for collecting these data: mandatory submission of low-value secondary fins (anal fins) from landed sharks by fishers and use of the fins to reconstruct catch species and size. Visual and low-cost genetic identification were used to determine species composition, and linear regression was applied to total length and anal fin base length for catch-size reconstruction. We tested the feasibility of this approach in Belize, first in a local proof-of-concept study and then scaling it up to the national level for the 2017-2018 shark-fishing season (1,786 fins analyzed). Sixteen species occurred in this fishery. The most common were the Caribbean reef (Carcharhinus perezi), blacktip (C. limbatus), sharpnose (Atlantic [Rhizoprionodon terraenovae] and Caribbean [R. porosus] considered as a group), and bonnethead (Sphyrna cf. tiburo). Sharpnose and bonnethead sharks were landed primarily above size at maturity, whereas Caribbean reef and blacktip sharks were primarily landed below size at maturity. Our approach proved effective in obtaining critical data for managing the shark fishery, and we suggest the tools developed as part of this program could be exported to other nations in this region and applied almost immediately if there were means to communicate with fishers and incentivize them to provide anal fins. Outside the tropical Western Atlantic, we recommend further investigation of the feasibility of sampling of secondary fins, including considerations of time, effort, and cost of species identification from these fins, what secondary fin type to use, and the means with which to communicate with fishers and incentivize participation. This program could be a model for collecting urgently needed data for developing-world shark fisheries globally.

Extinction risk, reconstructed catches, and management of chondrichthyan fishes in the Western Central Atlantic Ocean

“…Some recent studies have begun to fill these gaps by monitoring small-scale fisheries landings (e.g., Guyana – Kolmann et al, 2017; Venezuela – Marquez et al, 2019; Panama – Návalo et al, 2021). In the Belizean shark fishery, for example, a new low-cost method of analyzing fisher-contributed secondary shark fins was successful in determining species and size composition of catches and may prove valuable across the WCA in the future (Quinlan et al, 2021). More research on fishing effort, catch, and baseline abundance data is required to assess populations and adapt management priorities (Bizzarro et al, 2009; Kyne et al, 2012; Pérez-Jiménez & Mendez-Loeza, 2015).…”

“…In Venezuela, overfishing of shallow water stocks has led to deepwater (200–800 m) fishing north of Isla de Margarita and Paria Peninsula (eastern region, near Trinidad) and along the coast of Falcón (western region, near Aruba), where endemic and near-endemic species of deepwater sharks, rays, and chimaeras are now caught (OM Lasso-Alcalá, unpublished data ). Deepwater sharks are also targeted in Honduras (Baremore et al, 2016) and caught off Saba Bank (de Graaf et al, 2017), Curaçao (Van Beek et al, 2013), Belize (Quinlan et al, 2021), northern Cuba (Ruiz-Abierno et al, 2021), and the southern Gulf of Mexico (Pérez-Jiménez & Mendez-Loeza, 2015). In the northern Gulf of Mexico, deep reef-fish longline fisheries and shrimp trawl fisheries also catch deepwater sharks as bycatch, most of which are discarded (Scott-Denton et al, 2011; Scott-Denton & Williams, 2013; Zhang et al, 2014), and, in The Bahamas, recreational fishers often catch small deepwater sharks while targeting red snappers with electric reels (BS Talwar, pers.…”

“…). Across these WCA fisheries, the Dusky Smoothhound ( Mustelus canis , Triakidae; NT), Cuban Dogfish ( Squalus cubensis , Squalidae ; LC), Atlantic Sixgill Shark ( Hexanchus vitulus , Hexanchidae ; LC), Sharpnose Sevengill Shark ( Heptranchias perlo , Hexanchidae; NT), Night Shark (EN), gulper sharks ( Centrophorus spp., Centrophoridae; EN where assessed), and some catsharks (Scyliorhinidae; LC) are the most common deepwater species in landings (Baremore et al, 2021; de Graaf et al, 2017; Hacohen-Domené et al, 2020; Marquez et al, 2019; Quinlan et al, 2021; Scott-Denton et al, 2011; Van Beek et al, 2013).…”

Phylogeography and population genetics of the cryptic bonnethead shark Sphyrna aff. tiburo in Brazil and the Caribbean inferred from mtDNA markers

“…Bonnethead sharks are an important component of the fisheries in Latin‐American countries including Mexico, Belize, Guatemala, Costa Rica and Panama (Díaz‐Jaimes et al ., 2021; Harper et al ., 2014; Quinlan et al ., 2021). In Brazil, bonnethead populations have reportedly collapsed due to overexploitation and habitat destruction (Bressan et al ., 2009; Cortes et al ., 2016; Reis‐Filho et al ., 2014).…”

“…In Brazil, bonnethead populations have reportedly collapsed due to overexploitation and habitat destruction (Bressan et al ., 2009; Cortes et al ., 2016; Reis‐Filho et al ., 2014). Nonetheless, outside of the U.S.A. bonnethead populations are not directly assessed, and their fisheries are not actively managed for sustainability (Díaz‐Jaimes et al ., 2021; Quinlan et al ., 2021; Simpfendorfer & Dulvy, 2017), which means that the species status is underestimated throughout most of its range.…”