Reproduction, age, growth and mortality of axillary seabream, Pagellus acarne (Sparidae), from the Canarian archipelago

Abstract

Axillary seabream Pagellus acarne (Risso 1826) caught off the Canary Islands from January 1991 to December 1994 were studied. The length range of the catches was between 11 and 31 cm, with a modal distribution between 17 and 21 cm. The overall ratio of males to females was 1:1.74. Males were observed up to a length of 24 cm. Hermaphrodites were recorded at lengths between 15 and 23 cm. The species was characterized by protandric hermaphroditism. The reproductive season extended from October to March, with a peak in spawning activity in December–January. The size at sexual maturity was 15.8 cm total length (2 years old) for males and 19.4 cm total length (3 years old) for females. The total length–total weight relationship for the entire population is described by the parameters a = 0.0068, and b = 3.2401. Otolith age readings showed that the population exploited consisted of 10 age groups (1–10 years), including a very high proportion of individuals between 1 and 4 years old. The von Bertalanffy growth parameters for all individuals were L∞ = 32.98 cm, k = 0.22 years−1, and t0 = −0.87 years. Males grew comparatively slower than females. The instantaneous rates of mortality for all fish were Z = 0.96 years−1, M = 0.30 years−1, and F = 0.66 years−1. The exploitation ratio and the length at first capture were, respectively, E = 0.69 and LC50 = 16.1 cm. The stock is overexploited, therefore measures such as closed seasons or changes in fishing patterns would be desirable to safeguard the spawning stock and recruits.