World Aquaculture Society Meetings


Frank C. Sommers*, Ronald B. Johnson
 National Marine Fisheries Service
 Northwest Fisheries Science Center (NWFSC)
 Seattle WA 98112

Development of alternative, terrestrial plant-based feeds raises important nutritional issues. Several nutrients present in fish meal are absent in plant proteins, including taurine. Taurine plays an important role in many physiological processes including growth and olfaction. The sense of smell is important to fish, connecting them to the environment by relaying chemical information that plays a role in triggering behaviors associated with feeding, predator avoidance, reproduction and migration.

Elecrophysiological techniques make it possible to measure physiological olfactory responses to various substances. Some amino acids are important stimulants of searching and feeding behaviors. Olfactory sensitivity to different amino acids has been shown in fish and varies among species. Using the electro-olfactogram (EOG) and the electroencephalogram (EEG), it is possible to measure the neurological responses to amino acids at the receptor sites in the nose and the olfactory bulb. In this way, if the olfactory response in fish is affected by a lack of taurine in the diet, it should be possible to demonstrate that change using these techniques.

Two studies were conducted with fish maintained on plant-based feeds supplemented either with taurine at 1 or 1.5%, or with no taurine or a commercial feed as a reference.  Results of the initial experiment indicated a potential reduction in olfactory function in the olfactory bulb, presumably in response to taurine deficiency. Initial analysis of the larger follow up study may show a similar reduction in olfactory function (Fig. 1). Fish in this experiment however were maintained in a recirculating system as opposed to the flow-through system used in the initial experiment. Individual growth, olfactory function and whole body taurine levels were traced by individually marking fish with PIT tags. Whole body taurine levels of fish fed the 0 taurine diet averaged .1%, about half the level of fish that received the 1% taurine diet. Results of the follow up study indicate that taurine is either conserved, synthesized by sablefish, or possibly that fish are able to absorb taurine from culture water.

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