Sexual dimorphism in size, age, maturation, and growth characteristics of boarfish (Capros aper) in the Northeast Atlantic

Boarfish (Capros aper) have, in recent years, become of increasing commercial importance due to their apparent increase in abundance in the Northeast Atlantic. This study presents detailed biological information relevant to understanding stock structure and dynamics. Boarfish are a long-lived species that reach a maximum age of >30 years. The size distribution is skewed towards larger sizes, as expected from an unexploited stock with sexual dimorphism, where females are, on average, larger than males. No seasonal effects occur in size distribution and sex ratio, indicating that females and males stay together in shoals throughout the year. Females become increasingly dominant in abundance at larger sizes and older ages. There is no significant difference in length at maturity nor age at maturity between the two sexes, with L-50 = 9.7 cm and A(50) = 3.4 years. Growth is dimorphic following von Bertalanffy growth characteristics, with a common t(0) = -2.897, but significantly different K and L-inf values, where females have K = 0.145 and L-inf = 16.519 and males have K = 0.181 and L-inf = 14.437. The sexual dimorphism in size is thus caused by sex-specific growth and longevity patterns.