Female reproductive cycle and batch fecundity in the central-southern Adriatic population ofEngraulis encrasicolus(Osteichthyes: Engraulidae)

Abstract

The European anchovy, Engraulis encrasicolus, is a multiple-spawning small pelagic fish with a comparatively long reproductive season. From April to October 2009, ovary samples were collected from individuals of the southwestern Adriatic Sea in order to examine ovarian histological changes and assess batch fecundity monthly variations throughout the whole reproductive season. To assess monthly variations of the relative batch fecundity, the correlation between batch fecundity (F) -i.e. the number of oocytes released at each spawning act -and ovary-free body mass (W * ) was tested by four regression models; the power equation (F = aW * b ) was found to be the most suitable to describe F/W * correlations. The reproductive season of the anchovy of the central-southern Adriatic population lasts from May to September; in this period, all the oocyte development stages were observed, including hydrated oocytes and postovulatory follicles. In April, most fish had only unyolked oocytes; in October, an extensive atresia of yolked follicles was observed. The slope of all the ln F on ln W * monthly regressions did not differ significantly from 1, which shows that relative batch fecundity is constant all over the anchovy size range, throughout the spawning season. In the central-southern Adriatic anchovy population, batch fecundity increased from May to July and then gradually decreased until September. Differences in batch fecundity of the anchovy from different areas of the eastern Atlantic and Mediterranean could possibly be due to both environmental parameters and genetic differences among the different populations.

Liver melanomacrophage centres and CYP1A expression as response biomarkers to environmental pollution in European anchovy (Engraulis encrasicolus) from the western Mediterranean Sea

“…In fact, almost all sampled European anchovies (both age 1 and age 2 specimens) were in spawning condition, displaying ovaries with hydrated oocytes and postovulatory follicles (data not provided). European anchovies are partial spawners with a 30% daily spawning frequency (Basilone et al, 2015) from April to September (Zupa et al, 2013;Basilone et al, 2006). Although no definitive data have been reported regarding spawning site fidelity in this species, it is reasonable to assume that European anchovies spend the entire reproductive season in a restricted spawning area.…”

Global expression pattern of genes containing positively selected sites in European anchovy (Engraulis encrasicolus L.) may shed light on teleost reproduction

“…On average, each female anchovy spawns more than 50 times per year [12]. The fecundity of anchovy from different areas may vary due to a combination of environmental factors (such as water temperature) and genetic differences (such as body size) among different populations [13]. All these studies indicate that E. encrasicolus is a multiple-spawning and highly fecundate pelagic fish.…”