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Research article - Peer-reviewed, 2016

Feeding stimulants in an omnivorous species, crucian carp Carassius carassius (Linnaeus 1758)

Olsen, K. Hakan; Lundh, Torbjorn


Many fish are during feeding dependent on both an olfactory and gustatory sense. Olfaction that actsas the distance sense induces arousal, food search behaviour and attraction to the source, followed byexamination of food items by the gustatory sense. During buccal handling the fish decide if the feed willbe rejected or swallowed. Amino acids are often stimulatory to the gustatory sense and can act as feedingstimulants. There are, however, inter-species differences concerning what kinds of amino acids act asfeeding stimulants or deterrents. The species differences are probably dependent on the natural foodchoice. As feeding stimulating molecules increase feeding and growth, but deterrents have the reverseeffect, it is important to know what kind of molecules have either effect. In the present study we recordmouth handling time in the omnivorous crucian carp, Carassius carassius, of agar pellets containing waterextracts of meal consisting of ordinary food pellets, blue mussels or a commercial carp attractant. Thesetests were followed by testing with agar pellets with synthetic amino acids, based on the content of thewater extracts of the food pellets that was the only feeding stimulant. Neither extracts of mussel mealor of commercial carp attractants had a stimulating effect, i.e. no significant difference in handling timecompared to agar pellets with only water. A mixture of five of the major amino acids in the food pelletextract (40 mM alanine, 20 mM glycine, 20 mM arginine, 8 mM serine, 8 mM leucin) gave a significantlonger handling time compared to agar pellets with only water. The handling time was also longer for thethree amino acids that had the highest concentrations (40 mM Ala, 20 mM Gly, 20 mM Arg) and finallywith only alanine (128 mM). Agar pellets with only Ala gave, however, a significant shorter handlingtime compared to agar pellets with food pellet extract. The mussel meal extract had the same contentof free amino acids and their ranking order was the same as in extracts of food pellets, but at muchhigher concentrations. Based on the free amino acid content, the mussel extract should have stimulatedfeeding. This indicates that the mussel extract contained compounds that acted as feeding deterrents inomnivorous crucian carp that do not feed on blue mussels in their natural environment. Previous studieshave shown that blue mussel extracts act as feeding stimulants in several bottom feeding carnivorousfish. We finally tested betaine (100 mM) but the molecule had no significant stimulating effect that hasbeen observed in some other fish species.


Gustatory sense; Feeding stimulants; Mouth handling time; Agar pellets; Feed extracts; Mussel meal; Free amino acids

Published in

Aquaculture Reports
2016, volume: 4, pages: 66-73

Authors' information

Olsén, K Håkan
Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management

Associated SLU-program

Future Animal Health and Welfare (until Jan 2017)

UKÄ Subject classification

Fish and Aquacultural Science

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