Sexual dimorphism in age, growth and sexual maturity in channel bull blenny Cottoperca trigloides (Forster, 1801) (Bovichtidae: Notothenioidei) on the Patagonian Shelf, Southwest Atlantic

Perciform fish of the suborder Notothenioidei radiated in the cold marine environments of the Southern Ocean around Antarctica where they evolved a diverse array of ecological forms. Despite their relatively high abundance and important roles in the Antarctic and sub-Antarctic ecosystems, many aspects of their life history are still poorly known. In the present study, age, growth and sexual maturity of channel bull blenny Cottoperca trigloides were analysed using the data of 28,229 specimens collected over the last 30 years in the southern part of the Patagonian Shelf in the Southwest Atlantic. It was found that C. trigloides features sexual dimorphism with males attaining larger sizes than females, an unusual characteristic for notothenioid fish. Males also had higher growth rates, older maximum ages and slower maturation. The peak in gonad maturation and spawning in C. trigloides was revealed to take place in austral winter, similar to other notothenioids from the Patagonian Shelf, thus matching larval hatch with the spring bloom of zooplankton. Sexual dimorphism may be advantageous for large territorial males during competitive interactions, particularly in an environment characterised by strong patchiness of rocky areas that are most suitable for spawning. Evolution of life history traits that placed C. trigloides close to the r-end within the r/K strategy continuum evolved by notothenioid fishes, enabled this species to successfully compete with other medium-large and large predators in resources-rich environment of the Patagonian Shelf.