No abstract

Age and growth of the Spanish chub mackerelResumen.-Se analiza la edad y los patrones de crecimiento del estornino Scomber colias en aguas del sur de España, procedentes de dos áreas diferentes, costa Atlántica y Mediterráneo occidental, en el periodo comprendido entre octubre de 2003 y septiembre de 2004. La relación longitud-peso viene dada por la ecuación TW=0,0015 TL 3,5289 (r 2 = 0,99, donde TW= peso total en g, TL=longitud total en mm). La edad se determinó mediante la lectura (conteo e interpretación) de los anillos de crecimiento de otolitos sagitta en 221 ejemplares capturados por la flota comercial andaluza y durante las campañas oceanográficas de prospección de recursos marinos. En los otolitos, anualmente fueron depositados dos anillos, uno opaco y otro hialino. La zona opaca se formó principalmente en primavera y verano, mientras que la zona hialina se formó en otoño e invierno. La relación existente entre el radio del otolito y la longitud del pez, se describe mediante la ecuación: TL = 43,881 * OR 1,245 (r 2 = 0,93, donde OR= radio del otolito). Los parámetros de la curva ajustada de crecimiento de von Bertalanffy fueron estimados para los dos sexos de forma conjunta así como para todo el periodo de estudio (L ∞ = 43 cm, K = 0,27 para el Golfo de Cádiz, y L ∞ = 40 cm, K = 0,37 para el Mar de Alborán, donde L ∞ se define como la talla máxima teórica, y K como la rapidez con la que la curva se torna asintótica). No se han encontrado diferencias de crecimiento entre las distintas áreas de estudio, lo que sugiere que el Estrecho de Gibraltar no supone una barrera geográfica para el normal desarrollo del ciclo vital de esta especie. Por otro lado, gracias a las condiciones medioambientales similares del Mar de Alborán y del Golfo de Cádiz, el Estrecho de Gibraltar es una vía de comunicación importante que permite la existencia de un flujo larval entre el Atlántico y el Mediterráneo.Palabras clave: Scombridae, otolito, parámetros de von Bertalanffy, Estrecho de Gibraltar Abstract.-This paper studies the age and growth patterns of the Spanish chub mackerel Scomber colias off southern Spain collected from two different areas, Atlantic coast and Western Mediterranean, from October 2003 to September 2004. The length-weight relationship was given by TW=0.0015 TL 3.5289 (r 2 = 0.99, where TW= total weight in g, TL= total length in mm). Age was determined by interpreting and counting growth rings on the sagitta otoliths of 221 individuals caught by the commercial Andalusian fleet and during fisheries research surveys. Two rings, one opaque and one hyaline, were laid down each year on the otoliths. The opaque zone was formed during spring and summer and the hyaline one during autumn and winter. The otolith radius-length of the fish relationship was described by the equation: TL = 43.881 * OR 1.245 (r 2 = 0.93, where OR= otolith radius). The parameters of the fitted von Bertalanffy growth curve were estimated for sex combined for the whole period (L ∞ = 43 cm, K = 0.27 for the Gulf of Cadiz, and L ∞ = 40 cm, K =...

The biology, growth and reproduction of the axillary seabream, Pagellus acarne, was studied based on data obtained from the catches of the Andalusia commercial fleet operating off the coasts of southern Spain from October 2003 to September 2004. The axillary seabream had a very wide depth distribution, appearing from the surface down to 500 m depth. The length–weight relationship was given by TW = 0.0048 TL3.3207 (R2 = 0.98) (TW = total weight; TL = total length) for all fish from the Gulf of Cadiz and TW = 0.0093 TL3.1132 (R2 = 0.94) for all fish from the Alboran Sea. The proportion of females to males increases as length increases in both populations and the species is characterized by protandric hermaphroditism. Spawning males were present almost throughout the year although higher percentages were observed in spring and early summer. In females, the spawning period occurred mainly in spring. In both areas, the mean size at first maturity for males was smaller than for females. The mean lengths at first maturity were 18.04 cm for males and 21.7 cm for females from the Gulf of Cadiz, and 17.7 cm and 20.1 cm for males and females from the Alboran Sea, respectively. The average total fecundity was estimated at 290,070 and 173,509 oocytes for Atlantic and Mediterranean individuals, respectively. The parameters of the von Bertalanffy growth model were estimated by age readings of the 247 sagitta collected. Two rings, one opaque and one hyaline, were laid down each year on the otoliths. The opaque zone was formed during spring and summer and the hyaline one during the remaining months of the year. The relationship between otolith radius and total length of the fish was described by the equation: TL = 27.7 OR – 1.8 (r = 0.96) (where OR = otolith radius). The parameters of the fitted Von Bertalanffy growth equation were L∞ = 31.65 cm, k = 0.21 yr−1 in the Gulf of Cadiz and L∞ = 32.14 cm, k = 0.17 yr−1 in the Alboran Sea.