Effect of Combining Different Photoperiod Regimes on the Sexual Maturation of Male Sea Bass (Dicentrarchus labrax L.) During the First Two Years of Life

Abstract

This study assesses the effect of combining different photoperiod regimes on the sexual maturation and growth of male sea bass during the first two years of life. In two different trials, regimes of continuous light (LL) lasting 24 consecutive months (Trial 1) or shorter periods within the summer-early autumn months during the first and second annual cycles (Trial 2) were compared to control groups under a natural photoperiod (NP). In a third trial (Trial 3), fish kept under either NP or LL conditions during the first year were subsequently assigned a treatment involving exposure to NP or a constant long photoperiod (LP) throughout the second year. The rates of spermiating males, gonadal size (GSI) and growth under all these photoperiod regimes were analyzed. Exposure to LL reduced the rates of precocity in all trials (<3%) at the end of year one as compared to NP (13-22%), but full spermiation was still observed in year two (Trials 1 and 2), indicating that LL is not efficient for blocking gametogenesis at this time. Fish exposed to LP in Trial 3 displayed high GSI values (April) and a significant delay in gonadal maturation (62.50-100%; May) with respect to those exposed to NP (12.5%), which enhances the potential growth of the fish. In summary, exposure to LL reduces precocity in underyearling fish, while LP delays maturation during the second year, thus providing a promising approach for controlling male sea bass reproduction and growth.

Long-term feeding of a maintenance ration affects the release of Igf-1 and leptin, and delays maturation in a male teleost fish, Dicentrarchus labrax L.

“…These differences between salmonids and sea bass might be related to the anadromous life-strategy of some salmonid species, with an annual migration to the sea in summer, followed by a long starvation period in freshwater that coincides with the breeding season, which takes place over a few days or weeks, during which time energy resources are rapidly diminished. In the case of the European sea bass, this multiple spawner marine fish spawns during winter, and males remain actively spermiating for several months, notably as many as 6 months in captivity (Felip et al, 2017), and thus leptin regulation might differ in response to nutritional status. Furthermore, food availability between cold-water species (such as salmonids) and those species (such as the sea bass) found in regions of warm and tropical seas might have seasonal variations that influence the allocation of energy resources in a species-specific manner.…”