Reproductive strategy of forkbeard, Phycis phycis, from the Portuguese coast

Ana Neves,Leonel Serrano Gordo,Vera Sequeira,Ana Rita Vieira,Rafaela Barros Paiva

doi:10.1186/s10152-016-0455-x

Abstract

Knowing fish reproductive strategy is essential for understanding population dynamics. This study intends to define the spawning season, length at first maturity, fecundity type, and estimate fecundity of forkbeard, Phycis phycis, from the Portuguese coast. Monthly samples collected from commercial landings between May 2011 and December 2012 were used. Results show that forkbeard is a group-synchronous and batch spawner species. Mature females were found between September and January, mature males were found between August and January, and a significant concomitant increase in gonadosomatic index suggests a spawning season from September to January. Length at first maturity was estimated as 35.9 and 28.5 cm TL for females and males, respectively. Reproductive abnormalities—mosaic intersex, follicular cysts in ovaries, and early mature males—were detected. For fecundity-type definition, a hiatus between primary and secondary growth oocytes was detected. A significant increase in the mean diameter of secondary growth oocytes and a decreasing trend in their number during the spawning season were observed. The intensity of α-atresia was low throughout the spawning season. These four criteria suggest that forkbeard has determinate fecundity. Mean relative annual fecundity estimated was 1833 ± 857 oocytes g−1 gutted weight. Non-reproductive females that skipped a spawning season attained 36.1 %.

Highlights

The knowledge of life history traits of a fish species is essential for a comprehensive understanding of the population dynamics [24] and an essential key to identify and further assess fish stocks [56]
Forkbeard ovaries consist in two elliptic shape lobes, fused posteriorly, whose colour varies from whitish to pink, yellow, orange and red, as maturity progresses
This study indicates that the forkbeard is an iteroparous and gonochoristic species, which shows no sexual dimorphism, has external fertilization without parental care, presents a group-synchronous ovary development, is a batch spawner, and possesses determinate fecundity

Summary

Introduction

The knowledge of life history traits of a fish species is essential for a comprehensive understanding of the population dynamics [24] and an essential key to identify and further assess fish stocks [56]. Studies on reproduction, including timing and duration of spawning, the assessment of maturity size, and fecundity, permit the comprehension of the reproductive strategy of the species [47]. In fish species with determinate fecundity, this is fixed before the onset of spawning, and the number of yolked oocytes prior to the beginning of spawning is considered equivalent to the potential annual fecundity [47, 27]. In these species, total annual fecundity is estimated after discounting oocyte atresia from potential fecundity. Annual fecundity should be estimated from batch fecundity, spawning fraction, and the duration of the individual spawning season [27]

Methods

Results

Conclusion