Effect of salinity on somatic growth and gonadal enhancement of the sea urchin Paracentrotus lividus (Lamarck, 1816)

Salinity plays a major role in several physiological processes in sea urchins, including reproduction and growth, ultimately affecting survival. Optimal salinity ranges vary considerably between species, as a consequence of ecological adaptations. However, related research in the context of aquaculture is quite scarce, particularly for the stenohaline sea urchin Paracentrotus lividus (Lamarck, 1816), a target species for aquaculture diversification in Europe. It is thus important to better understand the response of this species to hyposalinity conditions over an extended rearing period. Four salinity treatments (20, 25, 30 and 35 psu) were evaluated, over 120 days, in terms of survival, feed intake, growth, gametogenic development and gonadal colour in P. lividus. While a 100% survival was obtained in all treatments, salinity significantly affected all other parameters. Sea urchins reared at 20 psu presented significantly lower linear and specific growth rates, feed intake, gonadosomatic index, as well as a higher feed conversion ratio. While sea urchins reared at 30 and 35 psu were mostly mature, hyposalinity led to a slower gametogenic progression in the lower salinities, particularly at 20 psu. Gonad colouration was only affected in males, as individuals reared at 20 psu presented less brighter, but more reddish and yellowish gonads. The results clearly demonstrate that despite the absence of mortality, rearing salinities of 20 and 25 psu promote a negative effect on somatic and gonadal yield of P. lividus.