Artisanal fishing activities and their documented interactions with juvenile white sharks inside a nursery area

Abstract

Juvenile white sharks distribute in coastal nursery areas, which are essential for population growth. Bahía Sebastián Vizcaíno (BSV), Mexico, is a white shark nursery area in the north‐eastern Pacific. Despite existing regulations forbidding the capture of white sharks, incidental catches still occur in some areas. Artisanal fisheries constitute one of the most important economic activities in BSV, yet no formal description of either these fisheries or the incidental catch of juvenile white sharks exists due to the poor data reporting system, thus preventing a clear understanding of the implications of these catches for the white shark population of the north‐eastern Pacific. Artisanal fishing activities and their interactions with juvenile white sharks in BSV are described based on fishermen's knowledge. Artisanal fisheries in BSV are multi‐specific, targeting mostly bottom‐related species (e.g. white seabass and California halibut) that are also common prey for juvenile white sharks. These activities are the only source of income for the majority of fishermen in BSV and are conducted throughout the year, with gillnets being the main fishing gear. White sharks are incidentally caught in bottom gillnets mainly during the summer, although another peak in incidental catch was recorded during winter, possibly related to the presence of juvenile white sharks from California, USA. The most common size of juvenile white sharks incidentally caught was <2 m in the nearshore areas close to the mouth of the Ojo de Liebre Lagoon; larger juveniles (~3 m) were caught in areas near Cedros, Natividad, and San Benito Islands. The multi‐specific nature of BSV artisanal fisheries and their socio‐economic value, and the high post‐release survival of juvenile white sharks suggest that future regulatory actions should focus on the release of incidentally caught live juvenile white sharks and the involvement of the BSV fishing community to increase the effectiveness of management efforts.

Interannual Nearshore Habitat Use of Young of the Year White Sharks Off Southern California

“…Previous studies that have addressed YOY white sharks from this Northeast Pacific population have identified the SCB as an important resource that provides nursery habitat for these sharks, and that habitat selection is driven by temperature, depth, and distance to shore (Klimley, 1985;Dewar et al, 2004;Weng et al, 2007b;Lowe et al, 2012;Lyons et al, 2013;White et al, 2019). However, the geographic range of YOYs and juveniles of this population extends to at least the southern tip of Baja California ∼1200 km (Weng et al, 2012), with specific nursery habitat identified toward the southern extent of the latitudinal range of this population, in Bahía de Sebastián Vizcaíno, Mexico (Oñate-González et al, 2017;Tamburin et al, 2019;García-Rodríguez and Sosa-Nishizaki, 2020). These studies, based upon data derived from satellite telemetry, remote sensing, and fisheries interactions, have been restricted to broad-scale observations of environmental drivers of habitat use and selection.…”

Stable Isotope Analysis of Juvenile White Sharks Inside a Nursery Area Reveals Foraging in Demersal-Inshore Habitats and Trophic Overlap With Sympatric Sharks

“…their stomach contents (Santana-Morales et al, 2012;García-Rodríguez and Sosa-Nishizaki, 2020). Hence, demersal prey may not have been fully representative of the shark's food sources.…”

“…However, they are caught incidentally in the nearshore areas of BSV as well as within Ojo de Liebre Lagoon (OLL), a semi-enclosed hypersaline shallow estuary located within the bay system (García-Rodríguez and Sosa-Nishizaki, 2020). These catches occur when local artisanal fishers target high-value species that are part of the white shark's diet (Santana-Morales et al, 2012;García-Rodríguez and Sosa-Nishizaki, 2020).…”

An illicit artisanal fishery for North Pacific white sharks indicates frequent occurrence and high mortality in the Gulf of California

“…However, prohibition of white shark catch (DOF, 2007(DOF, , 2014 has made the targeted fishery clandestine, not inactive. Increased enforcement has been a challenge in the Gulf, making monitoring, data collection, and enforcement difficult (Ainsworth et al, 2012;Cinti et al, 2010;García-Rodríguez & Sosa-Nishizaki, 2020;Hernandez & Kempton, 2003;Lluch-Cota et al, 2007); regular monitoring with fishermen involvement may improve conservation efforts (García-Rodríguez & Sosa-Nishizaki, 2020). Based on effective gillnet restrictions off California (Lowe et al, 2012), gear modifications or restrictions may reduce white shark bycatch (García-Rodríguez & Sosa-Nishizaki, 2020), while allowing adaptable artisanal fishers to utilize alternative gear and/or adjacent regions.…”

“…White shark-specific legislation has moved from a listing as "threatened" (DOF, 2002), to illegal targeting/trade (DOF, 2007), to illegal possession and mandatory release of incidental catch (DOF, 2014). Lack of reporting and monitoring is an ongoing challenge (Arreguín-Sánchez & Arcos-Huitrón, 2007;Cisneros-Montemayor et al, 2013;García-Rodríguez & Sosa-Nishizaki, 2020;Hernandez & Kempton, 2003), and incidental catch still occurs in American and Mexican fisheries (Oñate-González et al, 2017). A recent white shark status review under the Endangered Species Act by the National Oceanic & Atmospheric Administration (NOAA) (Dewar et al, 2013) recognized that additional mortality of adult females may occur in the Gulf, but at uncertain levels (García-Rodríguez & Sosa-Nishizaki, 2020) which precludes incorporation in population assessments.…”