Ecological regionalization of Zalophus californianus rookeries, as a tool for conservation in the Gulf of California

Abstract

There are 13 rookeries of California sea lions (Zalophus c. californianus) in the Gulf of California, 6 of which reflected the existence of 3 genetically distinct groups, Northern, Central and Southern. Up to now, however, the sea lion population of Mexico as been treated as a single unit. The aim of the present study was to explore the existence of a regionalized spatial pattern of Zalophus c. californianus rookeries in the Gulf, in order to contribute to their conservation and management. The following 9 ecologic-biogeochemical parameter databases were analyzed: population censuses, metal content in bone, Leptospira spp., stable isotopes (d15N and d13C), ostheoarthritis, diet and 2 environmental variables (local SST and Chl-a concentration). The exploration involved examining the geographic distribution of each variable, recompiling the regional structure discovered in previous studies and applying multivariate analysis. Using individual variables, the rookeries could be structured into 2 or 3 groups. Using Leptospira and the environmental parameters, the northern rookeries associated with those of the central Gulf, leaving the south as another group. The metals and diet yielded a segregation of the northern rookeries and a regrouping of those in the central and southern Gulf. Osteoarthrytis and stable isotopes distributions also lead to a center-south association, but with 2 groups in the north.