Reproductive biology of the striped red mullet, Mullus surmuletus, and implications for its management

Abstract

[eng] Mullus surmuletus Linné, 1758 is one of the most important target species of Iberian Peninsula fisheries, including the Balearic Islands, where the official registers of annual catch vary between 100 and 400 tones. However, in the last 7 years, annual catches have been decreasing and now they oscillate between 60 and 100 tonnes. Despite its economic relevance, some of its reproductive aspects are still unknown. The objective of the present study is to characterise the reproductive ecology of M. surmuletus including the reproductive cycle and strategy, fecundity, population distribution and size-at-maturity. This study was based in the analysis of 1998 individuals obtained with two different fishing gears, trammel and trawling, captured between 13 and 518 m depth (mostly at depths inferior to 100 m), covering an entire year of sampling. The population structure of this species showed a marked bathymetric pattern, with the presence of larger individuals at shallower waters (< 50 depth), as well as a marked sex ratio segregation between shallow and deeper waters. Macroscopic and microscopic analyses of the gonads as well as Gonado Somatic Index showed a seasonal reproductive cycle with the presence of spawning females from March to May, while males spawn from January to May. The size-at-maturity was 14,4 cm for females and 12,2 cm for males. The size-frequency distribution of oocyte diameter showed an asynchronic ovarian organisation. The counting of mature oocytes in females just prior to spawn showed a total fecundity of approximately 335000 ± 75000 oocytes per female.