Population ecology, life history and diet of the shorthead drum Larimus breviceps in a tropical bight in southeastern Brazil

Abstract

The population biology, life history parameters and diet of the shorthead drum Larimus breviceps were assessed in Caraguatatuba Bight, a shallow non-estuarine environment. Two homogeneous areas, South and North, were selected, avoiding major sources of continental waters. Monthly from October 2003 to October 2004, three random samples were taken by trawling from 800 to 1600 m outward from the waterline. Larimus breviceps was the third most abundant species during the study period, and was considerably more abundant from February to May 2004. Smaller individuals were also more abundant during this period, which we therefore considered the main recruitment period of the species. The predominance of individuals of a limited size range (6–12 cm total length) seems to indicate that the area functions as a nursery for L. breviceps, sheltering late-juvenile individuals. This feature complicated the estimation of life history parameters, but by taking into account the peculiarities of the area and the identification of similar modal progressions during the sampling period, we obtained reasonable values for the parameterization of the von Bertalanffy Growth Model (L∞ = 32.25 cm, K = 0.72, tmax 4.38 y, Z = 12.104). The total mortality index does not reflect mortality rates only, but also the migration of older individuals to other, probably deeper, areas. The diet was based mainly on Crustacea, specifically Decapoda shrimps, with slight seasonal alterations.