Striped red mullet (Mullus surmuletus, Linnaeus, 1758) in the eastern English Channel and southern North Sea: growth and reproductive biology

Biological information is necessary for population structure assessment of economically important species. There are no known published studies on the age and reproduction of Mullus surmuletus in the north of the Bay of Biscay. The aim of this study was to estimate growth and reproductive biology of this species in the eastern English Channel and southern North Sea 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 Bertalanffy 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 English Channel, 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