Ingestion rate, absorption efficiency, oxygen consumption, and fecal production in green sea urchins (Strongylocentrotus droebachiensis) fed waste from sablefish (Anoplopoma fimbria) culture

Abstract

The ability of the green sea urchin ( Strongylocentrotus droebachiensis ) to consume and subsequently reduce the organic content of sablefish ( Anoplopoma fimbria ) culture waste was assessed and properties influencing the dispersal of fecal pellets egested by the sea urchins were quantified in laboratory trials. Ingestion rate, absorption efficiency, and oxygen uptake in sea urchins and the shape, size, and settling velocity of fecal pellets were determined for individuals fed sablefish waste or a natural control diet (giant kelp , Macrocystis pyrifera ). Results showed that S. droebachiensis consumes sablefish waste at a dry weight ingestion rate of 0.43 ± 0.039 g individual − 1 d − 1 and absorbs 40 ± 4.84% (mean ± SE) of the organic material ingested, with no significant ( P < 0.05) differences between the diets tested. Oxygen consumption was significantly ( P < 0.05) higher in sea urchins fed sablefish waste than in those fed kelp at 0 and 2 d after feeding. The fecal pellets egested by sea urchins fed sablefish waste were significantly rounder and smaller and had a higher settling velocity than those from individuals fed kelp. This study demonstrates that green sea urchins actively ingest and absorb organic material from the waste produced by sablefish culture. Further research is recommended to determine the effect of the sablefish-waste diet on sea urchin survivorship, growth, and gonad quality. Culture of S. droebachiensis integrated with sablefish is warranted on an experimental scale. • Green sea urchins can consume and absorb sablefish waste. • They do this at rates not significantly different from those fed a control of kelp. • Oxygen consumption was higher in urchins fed fish waste than in those fed kelp. • Fecal settling velocity was higher for fish-waste-fed urchins than kelp-fed ones.