Growth and maturity of sprat in Norwegian coastal waters

Abstract

Data on length, age and maturity were analysed to study the growth and spawning of sprat in fjords on the Norwegian West Coast. The data were sampled in 4 fjord Areas in November 1993-1997 (for mean length and weight-at-age) and in the 2nd quarter 1992, 1996-1998, (maturity/spawning). The samples are taken by pelagic trawling. In addition, the length of 0-group sprat along the western coast was investigated by including sprat sampled further north on the coast. In 0-group sprat, significant differences in mean length were found along the coast. These differences seemed to be stable between years. In fjords just north of 62'N, the length were significant larger and further north significant lower, shows low correlation. In the present study it was shown that sprat stayed in the fjords during the spawning season and that they are spawning. Mature sprat had a minimum length of 8,0-9,0 cm. The results demonstrate that maturation in sprat is length dependent. The length at 50% maturity was 9,3 cm. The present study shows that sprat in the Norwegian fjords normally mature as 1-year olds. They will spawn during the current season but later than older fish (June-July). The spawning frequencies were in the range of 8-20%. Mature/spawning sprats were found in the entire area and no specific spawning aggregations were observed.