Estuarine dependency in a marine fish evaluated with otolith chemistry

Life-long strontium patterns in otoliths of the sciaenid Micropogonias furnieri caught in the southwestern Atlantic Ocean were examined to evaluate estuarine dependency and habitat use. Otolith Sr concentrations were on average 820 +/- A 55 mu g g(-1) for freshwater, 1,751 +/- A 101 mu g g(-1) for estuarine, and ranged from 2,000 to over 4,000 mu g g(-1) for marine waters. The examination of life-long otolith Sr revealed that 71 % of the marine-sampled fish moved toward brackish waters from age 0 to age 1, and that estuarine egress ranged from ages 2.1 to 4.1 years depending on the sampling area. Three different long-term patterns of Sr accumulation were observed and inferred to be the result of ontogeny and habitat shifts. Given that an estuarine Sr signature was consistently present in all sampled fish, M. furnieri is suggested to be a true estuarine-dependent species during its early life history.