Morphological changes in artificially reared one year old sea trout (Salmo trutta L.) during spring

Rutkovska, I., Latvia Univ. of Agriculture, Jelgava; Medne, R., Institute of Food Safety, Animal Health and Environment BIOR, Riga

Morphological changes in artificially reared one year old sea trout (Salmo trutta L.) during spring

2015

Rutkovska, I., Latvia Univ. of Agriculture, Jelgava (Latvia) | Medne, R., Institute of Food Safety, Animal Health and Environment BIOR, Riga (Latvia)

Morphological parameters and their changes common for artificially reared one year old sea trout were examined from January to May the year 2013 to determine whether these parameters indicated the smoltification in one year old sea trout and whether these fish achieved smolts stage. Fish were reared in flow-through and recirculation systems in hatcheries based on three different rivers (Brasla, Daugava, Venta basin). Sea trout were examined in the Latvia University of Agriculture, Faculty of Veterinary Medicine, Institute of Food and Environmental Hygiene and in the Institute of Food Safety, Animal Health and Environment BIOR, Laboratory of Aquaculture and Fish Pathology. To appreciate fish growth stage condition index, hepatosomatic index, spleen index was calculated and silvering level was evaluated. The fish condition index decreased in all hatcheries and flow-through and recirculation rearing systems from January to April and increased in May. Spleen index was the most stable parameter and did not change a lot showing that fish did not have migratory stress in April and May. Silvering level increased from January to April but suddenly the increase became slower in May without reaching the top level. These results made us to consider that one year old sea trout parrs released in May 2013 probably did not become smolts before release and they had to stay in river for one additional year until reaching pronounced smolt stage.

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