Assessment of Egg and Larval Quality during Hatchery Production of the Temperate Sea Cucumber, Australostichopus mollis (Levin)

Abstract

Abstract A greater understanding of the causes of variation in egg and larval quality during larval rearing of sea cucumbers will assist in the development of methods to further improve production in hatcheries. For Australostichopus mollis the techniques and methods used in other hatcheries during fertilization resulted in polyspermy occurring in 10–60% of spawned eggs. Despite this, hatch rates were usually greater than 90%. By Day 18 when fed the diatom Chaetoceros muelleri at 2000 cells/mL/day, survival in cultures varied between 35 ± 26% and 57 ± 25%. Of remaining larvae, 10–12% remained in the water column for long periods and did not complete metamorphosis. Furthermore, observation of development in relation to growth and feeding rather than gut content was a better indicator of larval competence. Larvae that were between 700 and 1000 ± 50 μm in length had between four and eight hyaline spheres in the folds of the ciliated band and were in various stages of metamorphosis and settlement. Assessment and comparison of current and previous methods enabled a greater understanding of sources of variation in egg and larval quality, impacts on the production cycle, and suggested improvements.