Use of krill hydrolysate as a feed attractant for fish larvae and juveniles

We determined the effect of krill hydrolysate as a feed attractant in three freshwater fish species: yellow perch Perca flavescens, walleye Stizostedion vitreum, and lake whitefish Coregonus clupeaformis. Growth trials were conducted using a commercial trout starter diet (control) and the diet that was coated with liquid krill hydrolysate. The krill hydrolysate coated diet increased growth of yellow perch juveniles by 31% compared to control diet (average final wet weight, 734 ± 33 mg and 559 ± 82 mg, respectively). Moreover, weight gains were not significantly different than for fish fed exclusively live Artemia nauplii. Similar results were obtained with walleye juveniles fed either a trout starter diet or 5% krill hydrolysate coated diet (8.9 ± 0.25 g and 11.6 ± 5.1 g wet weight, respectively). The food conversion ratio (FCR) was lower in fish fed the control diet, although not significantly different (2.95 ± 0.18 and 3.69 ± 0.39, for control and coated diet, respectively). The effect of krill hydrolysate on dry diet ingestion rates of lake whitefish and yellow perch larvae was also determined using radio-active (¹⁴C) labelling. A commercial starter diet was coated with krill hydrolysate or the soluble fraction of krill hydrolysate was added to the experimental tank water. In both species, coating the diet with 5% krill hydrolysate resulted in significantly higher ingestion rates. Supplementation of krill hydrolysate soluble fraction to the tank water resulted in 200% increase in ingestion rate in comparison to control (uncoated starter diet), although it was not significantly different from krill coated diet and live Artemia nauplii ingestion rates.