Formulated feeds prolong the reproductive period of a cultured echinoid

Abstract

The production of echinoid larvae and juveniles is required in both wild‐population enhancement programs and full life‐cycle culture. Many echinoid species of commercial interest spawn only once or twice a year, however, restricting temporal access to viable broodstock. High‐energy/high‐protein formulated feeds have been used for gonad enhancement of a variety of echinoid species, but the goal of that activity has always been to produce pre‐mature gonads, which the market requires, not the production of mature gonads for breeding. The present investigation, originally established to examine gonad enhancement, took advantage of a spawning event to assess the efficacy of a formulated feed to extend the spawning period or reduce gonad recovery time after spawning in a commercially relevant echinoid, the green sea urchin (Strongylocentrous droebachiensis). Urchins held in suspended sea cages were fed either a formulated, commercial, pelleted urchin diet or bull kelp (Nereocystis luetkeana) over 12 weeks, survival, somatic growth, gonad quantity (wet weight, yield), and gonad quality (presence/absence of gametes) being examined over time. Survivorship after 12 weeks was high, little difference being observed between the two diets (mean ± SE: 98.2 ± 1.1% and 95.9 ± 1.9% for kelp and formulated feed, respectively). There was no significant difference in somatic growth between the two treatments, but formulated feed led to significantly higher gonad wet weight and yield than kelp at the end of the study. When compared with kelp, formulated feed may have led to earlier spawning, quicker gonad recovery, and prevented the complete spawning of all urchins, thus extending the period of gamete availability. Formulated feeds may have the potential to maintain reproductively active broodstock over an extended time, allowing expansion of the period in which echinoid larvae and juveniles can be produced.