Seasonal patterns of feed intake and growth of Hammerfest and Svalbard Arctic charr maturing at different ages

Age at maturity, feed intake and growth were monitored in two strains (Hamm erfest, 70 degrees N and Svalbard, 80 degrees N) of Arctic charr, Salvelinu s alpinus, held under comparable rearing conditions for 2 years (age 9 to 3 2 months after hatching). Feed intake of individually tagged fish was measu red using X-radiography, and growth rates and timing of maturation were mon itored for the same individuals. There were differences in age at first mat urity, both between strains and between sexes. In the Hammerfest charr, 56% of the males matured at age 1 + , bur no male Svalbard charr matured at th is age. At age 2 + , 94% of the Hammerfest males were mature, compared to 1 4% of the Svalbard males. No females matured at age if, while 71% of the Ha mmerfest females matured at age 2 +. No Svalbard females matured during the study. There were no differences between strains in weight, feed intake an d growth before the first reproductive season at age 1 + . When fish were h eld at constant temperature (7 degrees C), seasonal variations in feed inta ke and growth were observed in fish of both strains and sexes. Svalbard cha rr were significantly larger than Hammerfest charr from age 19 months onwar ds, and by the end of the experiment, the Svalbard charr were 25% larger th an Hammerfest charr. The differences between the strains were largest in 2 + mature males. Prior to maturation, maturing fish were significantly large r than immature fish, but in the weeks immediately prior to maturation, the maturing fish grew significantly less than the immatures. (C) 1999 Elsevie r Science B.V. All rights reserved.