Striped red mullet ( M ullus surmuletus , L innaeus, 1758) in the eastern E nglish C hannel and southern N orth S ea: growth and reproductive biology

Summary Biological information is necessary for population structure assessment of economically important species. There are no known published studies on the age and reproduction of M ullus surmuletus in the north of the B ay of B iscay. The aim of this study was to estimate growth and reproductive biology of this species in the eastern E nglish C hannel and southern N orth S ea from 1089 individuals, observed from February to December 2004. The length–weight relationship was described by the parameters: a  = 3.284.10 −6 and b  = 3.243, being allometrically positive. Ages were determined from increments of otoliths, used entirely after a burning treatment. Marginal‐increment analysis showed an annual periodicity of increment formation. Von B ertalanffy growth equations were estimated as TLt = 51.2(1−e −0.19( t +2.904) ) for females and TLt = 36.0(1−e −0.218( t +3.232) ) for males. Comparing the observed growth performance index (φ′ = 2.676) from others studies, a positive growth gradient was suggested for M . surmuletus from south to north of its distribution area. Females grew significantly faster and reached a larger size at age than males. Length at 50% maturity was 16.9 and 16.2 cm, respectively, for females and males, corresponding to an estimated age of 1 year for both sexes. In the eastern E nglish C hannel, according to both the gonadosomatic indices ( GSI ) and maturity stages, the observed spawning period of M . surmuletus was from May to July. The present description of the red mullet life history characteristics in this region may constitute a preliminary step to future population dynamics modelling and stock assessment exercises.