The Use of Laguna Yalahau, Quintana Roo, Mexico as a Primary Nursery for the Blacktip Shark
Robert E. Hueter, J. Leonardo Castillo-Géniz, J. Fernando Márquez-Farias, and John P. Tyminski
Abstract.—Mexican coastal waters of the Gulf of Mexico serve as nursery areas for many shark species and traditional fishing grounds for artisanal fishermen. To characterize the use of these areas as shark nurseries, obtain information on the biology of juvenile sharks and understand the fishing pressure on these resources, a multiyear study was conducted in Laguna Yalahau, a shallow coastal lagoon located on the northeastern corner of the Yucatán Peninsula. Using primarily gill-net surveys and tagging of juvenile sharks during the late spring months of May–June, our binational research team conducted six expeditions inside the lagoon from 1995 to 2001. Sixty-seven species of teleosts, elasmobranchs, and other marine vertebrates consisting of 5,590 individuals were collected during the surveys. We captured 1,384 sharks of which 99% were neonate, young-of-the-year, or older juvenile blacktip sharks Carcharhinus limbatus, confirming that Laguna Yalahau is a primary nursery for that species. Other sharks collected were lemon shark Negaprion brevirostris, bonnethead Sphyrna tiburo, nurse shark Ginglymostoma cirratum, and Atlantic sharpnose shark Rhizoprionodon terraenovae. Using the Petersen method during 2000 and 2001, we estimated the sampled population size of newborn blacktip sharks in the lagoon to be 726 and 1,066, respectively, born to approximately 189 and 277 maternal females, respectively. Over the course of the study, 1,155 sharks were tagged and released. The recapture rate of tagged sharks by artisanal fishermen was 21.9%, more than five times the rate for similar sharks off the Florida coast, and all recaptures came from the coast of the Yucatán Peninsula. In light of this high recapture rate, it appears that Laguna Yalahau serves as a primary nursery for sharks that have been heavily exploited by Mexican artisanal fishermen.