Reproduction of the shorthorn sculpin Myoxocephalus scorpius in northern Norway

Abstract

The reproduction and life history events of the shorthorn sculpin Myoxocephalus scorpius were studied in an unexploited high latitude population in Tromsø, northern Norway. Shorthorn sculpins were sampled from November 1998 to March 1999 to determine sex ratio, spawning period, oogenesis, fecundity, embryogenesis and hatching. Spawning occurred between January and March. The catches of males were maximal in January and February, while catches of predominantly immature females increased towards the end of the spawning period. This may be related to different migration patterns in males and females. It is possible that after spawning, females migrate to other areas, whereas males stay behind and guard the eggs. The spawned eggs were smaller than reported from other study areas. Larvae hatched after 7 weeks at an average egg incubation temperature of 3.3 °C. Fecundity in females ranged from 1200 to 29 000 eggs, with a length exponent of 3.0. The relatively large size (7.6–8.8 mm in length), advanced performance and developmental status at hatch of shorthorn sculpin larvae suggest that the reproductive strategy of the shorthorn sculpin is an intermediate between strategies that have many small larvae and those that have fewer, larger and more developed larvae.