Age, growth and mortality of Lutjanus alexandrei in estuarine and coastal waters of the tropical south-western Atlantic

Abstract

Otolith-based methods were used to determine life history traits of the endemic Brazilian snapper (Lutjanus alexandrei) in estuarine and coastal environments in the south-western Atlantic. Fishes were caught as juveniles inside mangrove-bordered estuaries by traditional corral fisheries whereas adults were captured at sea using motorboats with trap and gill nets. Fish were sampled during landings and 331 otolith pairs were extracted from L. alexandrei. Inshore mangroves comprised individuals of 0–4 years (mean: 2 years), while individuals in deeper reef environments were older (range: 3–22; mean: 8 years), indicating an ontogenetic shift at approximately age 3 or 4. Edge analysis was used to validate the annual deposition in the otoliths, suggesting that opaque growth rings were formed between April and September. Age-at-length data were used to predict L. alexandrei growth rates using the von Bertalanffy growth model from where the parameters were calculated: L∞ = 31 cm, k = 0.24, t0 = −1.26, r2 = 0.97. Mortality rates were estimated for coastal habitats, with Z = 0.22 and S = 0.78 year−1, based on ages 7–17. Additionally, evidence of ontogenetic migration is provided by age and size structure.