Chemical fractionation of shrimp extracts inducing bottom food search behavior in cod (Gadus morhua L.).

The bottom food search (BFS) feeding behavior in cod (Gadus morhua L.), has been used in a bioassay for chemical isolation of the feeding stimulant substances present in shrimp (Pandalus borealis). An aqueous methanol extract of ground shrimp was separated into acidic, neutral, and amphoteric/basic fractions by ion-exchange chromatography and into single components by preparative high-pressure liquid chromatography (HPLC). Of the isolated single components, the amino acid glycine was most potent, followed by alanine. Two unidentified substances were also highly potent. There was a synergistic effect between glycine, alanine, proline, and arginine. These four amino acids were more potent than the total amino acid pool found in the shrimp extract, indicating that there may be amino acids in this pool having an antagonistic effect.