The small-scale shark fisheries in the southern Gulf of Mexico: Understanding their heterogeneity to improve their management

Fisheries targeting sharks in the southern Gulf of Mexico are generally restricted to a few months or fish in several months but participate in other fisheries. Sharks are also part of the by-catch in most fisheries that use gill nets or longlines. The fisheries targeting sharks include the following: (1) a gill net fishery for Rhizoprionodon terraenovae and Sphyrna tiburo in April–June and August–September, respectively, off of northern Campeche; (2) a gill net fishery for Carcharhinus leucas in November–March off of central and southern Campeche; (3) a longline fishery for C. leucas, Carcharhinus plumbeus and Sphyrna lewini throughout the year off of the Tabasco state; (4) a longline fishery for C. leucas by medium-sized boats from the state of Yucatan; and (5) a fishery with gill nets for Carcharhinus limbatus off of the central coast of Tabasco in April–May. The decline in shark catches over the last two decades in Mexico prompted a series of management measures, including the restricted issuance of fishing licenses, gear regulations and closed seasons. Fishery management includes all shark species, but does not consider species-specific differences in life history, the regional seasonality of the target fisheries, or differences in the gear types that are used to target small or large sharks. We recommend the establishment of separate management measures for small and large shark fisheries because, in addition to differences in the biological productivity of the target species, these two fisheries differ in the type of gear used and the seasonality and region in which the fishing occurs. The fishery for R. terraenovae off of northern Campeche has characteristics (same period and area over many years, catch composition dominated by adults and the target species accounts for 80–90% of the catch) that enable population assessments and the evaluation of the efficacy of management measures. Further restrictions on the use of gear types that target large sharks are recommended due to the vulnerability of those species (e.g., C. leucas).