KCl induced paralysis facilitates detachment of hatchery reared juvenile green sea urchins, Strongylocentrotus droebachiensis

In echinoculture, there is a need for a suitable detachment agent to facilitate grading and transfer of cultivated juveniles from settlement substrate to intermediate culture. KCl appears to be a convenient, inexpensive, readily available, nontoxic, and efficient agent for inducing paralysis and detachment of juvenile green sea urchins, Strongylocentrotus droebachiensis. The anaesthetic effect of KCl and three other chemical compounds was tested on hatchery reared juvenile S. droebachiensis. The number of paralyzed juveniles was recorded after 10 min submersion in different strength solutions of potassium chloride (KCl), magnesium chloride (MgCl 2), benzocaine, or 2-phenoxyethanol. Mortality was monitored by recording survival after 1 day and again after 7 days. KCl at 0.25%, 0.5%, 1%, 5%, and 10% concentrations induced 100% paralysis whereas the other chemicals were less effective, or did not induce 100% paralysis at sublethal concentrations. The duration of the KCl effect was dose-dependent and lasted approximately 10 min at 0.25%, and approximately 24 h at 5%. Mortality was 0% at KCl concentrations ≤5%, but increased to 100% at 10% concentration. There was no mortality in the control treatments, and all juveniles remained attached.