EFFECT OF SALINITY ON GROWTH AND SURVIVAL OF THE JUVENILE SEA CUCUMBERS HOLOTHURIA TUBULOSA (GMELIN, 1788) AND HOLOTHURIA POLI (DELLE CHIAJE, 1923)

摘要

The aim of this study is to determine the effect of salinity on growth and survival of juvenile sea cucumbers (Holothuria tubulosa and Holothuria poll). Specific growth rate and survival of 18±0.44 g sea cucumbers stocked at 25, 30, 38 (control) and 45 ppt were investigated at summer (15°C) and winter (25°C) temperature triplicates for 60 days. While H. tubulosa had negative specific growth rates (-0,81 and -0,55/day) at 30 and 45 ppt in summer and winter temperature conditions, H. poli presented a similar growth rate (0,66/day) at 45 ppt with the individuals at 38 ppt salinity group. Juveniles of both species ceased feeding and estivated under low-temperature conditions (15°C) at 30 (low) and 45ppt (high) salinities and lost their weight. These results consider that H. tubulosa juveniles are unsuitable for low and high salinities, where H. poli can adapt high salinities (45 ppt) but with limited tolerance to the low salinities. The optimal salinity for optimal growth and survival considered as 38 ppt at 15°C for both species. In summer temperatures as 25°C, a salinity range from 38 to 45 ppt considered as optimum for H. poll and a salinity of 38 ppt for H. tubulosa. The lethal low salinity level is 25 ppt for both species.