The artisanal elasmobranch fishery on the east coast of Baja California, Mexico: Characteristics and management considerations

Wd Smith,Gm Cailliet,Jj Bizzarro

doi:10.7773/cm.v35i2.1534

Abstract

The Mexican elasmobranch fishery ranks among the most important in the world, but details associated with fishing effort and species composition are generally unavailable, particularly for the extensive artisanal fishery. Seasonal surveys were conducted during 1998–1999 in the state of Baja California to determine the extent and activities of the artisanal elasmobranch fishery along its Gulf of California coast. Artisanal fishermen were highly opportunistic, and temporally switched targets depending on the local abundance of teleost, invertebrate, and elasmobranch fisheries resources. At least 17 species of shark, 13 species of ray, and 2 species of skate were identified among the 4495 specimens observed. Small, coastal sharks and rays were typically landed with bottom set gillnets during all surveyed seasons (spring–autumn) and large sharks were targeted with surface set (drift) gillnets during summer and autumn. Sharks and rays contributed similarly to elasmobranch landings, comprising 50.9% and 48.3%, respectively, of the total recorded catch. Overall landings were dominated by mustelid sharks (Mustelus henlei, Mustelus spp.) and the shovelnose guitarfish (Rhinobatos productus), with Alopias pelagicus, Gymnura spp., Heterodontus mexicanus, Mobula munkiana, Myliobatis californica, and Squatina californica also representing important components of the landings. Alopias vulpinus had previously been unreported for the Gulf of California and a new maximum size record was documented for Myliobatis longirostris. Catch rates (mean elasmobranchs/vessel/trip ± standard error) were lowest during autumn (17.4 ± 3.9) and highest in spring (35.3 ± 14.1). Adult, commonly gravid, A. pelagicus, Carcharhinus falciformis, and R. productus females comprised a disproportionately greater component of the landings than did their male counterparts. Given the decades of largely unrestricted exploitation of elasmobranchs in Mexican waters, population declines and shifts in size structure are likely to have occurred among those species with the lowest fecundity and latest ages at maturity.

Highlights

IntroducciónGlobal elasmobranch fisheries are largely unregulated and catch records, when available, are often generalized and lack associated details on effort (Musick et al 2000, Stevens et al 2000)
The eastern Baja California elasmobranch fishery was surveyed in spring, summer, and autumn of 1998 and 1999
A total of 17 artisanal fishing camps were documented on the eastern coast of Baja California over 70 survey days during 1998–1999

Summary

Introduction

IntroducciónGlobal elasmobranch fisheries are largely unregulated and catch records, when available, are often generalized and lack associated details on effort (Musick et al 2000, Stevens et al 2000). Batoid landings have been historically unrecognized or grouped in with other unidentified species as “other species (otras especies)”. These categorizations have been recently improved and are currently collectively designated as “manta rays/rays (mantarrayas/rayas)”. Large sharks (≥1.5 m in total length) are reported as “sharks (tiburón)” and small sharks (≤1.5 m TL) are identified as “small sharks (cazón)”. Based on these aggregate classifications, sharks of the same species may be reported in both shark categories depending on the size of individuals (Castillo-Géniz et al 1998)

Methods

Results

Conclusion