Behavioural responses of the Persian sturgeon (Acipenser persicus) juveniles to free amino acid solutions

This study analysed the attraction/avoidance responses of the Persian sturgeon (Acipenser persicus) juveniles to 20 free L-amino acid solutions, 0.001 M. We used aquaria with two parallel compartments with a water flow of ≈ 300 mL min−1 in each compartment. During each trial, the flow of clean water in one compartment was replaced for 3 min by a test solution of free amino acids. We counted the number of fish in each compartment every 30 s for 3 min and also used a qualitative assessment to characterise the sturgeon's searching behaviour. Daphnia water extracts were used as a positive control. Treatments and positive and negative controls (clean water) were replicated 10 times each. Solutions of alanine and glycine elicited the strongest food searching responses. This was confirmed by comparing the numbers of fish in test and control compartments. Leucine, histidine, cysteine, isoleucine and proline evoked low positive responses, which were confirmed by a quantitative assessment. Aspartic acid, tyrosine a...