Evaluating feed attractants and replacement diets to reduce Artemia spp. use in albino Rainbow Sharkminnow Epalzeorhynchos frenatum larviculture protocols

Abstract

Abstract Objective Brine shrimp Artemia spp. nauplii are a widely used first feed in ornamental aquaculture due to their digestibility, adequate nutritional profile, and ability to elicit feeding behavior from larval fish. Issues with variable cost and nutritional consistency, however, render Artemia spp. a suboptimal feed for extended periods. Inert alternatives, such as commercially available microparticulate diets (MDs) and liquid diets, although nutritionally robust, lack intrinsic motility, which can lead to insufficient ingestion rates during early developmental stages, where appropriate nutrition is critical. Methods A series of experiments was conducted with larval albino Rainbow Sharkminnow Epalzeorhynchos frenatum to evaluate the efficacy of top-dressing MDs with three different amino acid feed attractants (FAs)—L-alanine, betaine, and L-tryptophan—to enhance larval feed ingestion. The FAs were tested at varying concentrations to identify inclusion amounts that improved survival and growth after 7 d of feeding. A subsequent 21-d experiment followed, including all three FAs at their respective best-performing inclusion amounts to determine whether additive or synergistic effects resulted from their combined application. Two liquid Artemia replacement diets (LiquaLife and EZ-Artemia Ultra) were also assessed by substituting 50% or 100% of nauplii to compare the diets’ performance relative to live Artemia spp. and determine whether they could be a cost-effective substitute. Survival, standard length, and larval quality were evaluated as experimental end points. Results The L-alanine and betaine diets increased larval survival during the 7-d experiments, while the L-alanine and L-tryptophan diets increased larval survival during the 21-d experiment. Neither brand of liquid Artemia diet resulted in any increase in survival or growth when compared with the reference diet consisting of live Artemia spp. nauplii. Conclusions Inclusion of specific FAs may increase larval survival by up to 10% compared with the control MD. Additional trials that investigate weaning from live feeds to MDs are warranted to further refine feeding protocols for larval albino Rainbow Sharkminnow.