Distribution and abundance of Norwegian spring spawning herring during the spawning season in 2000

Abstract

During the period 15.02-26.03.2000 the maturing and spawning herring (Clupea harengus L.) were distributed along the Norwegian coast from 57°N to 69°N. Between 61°N and 69°N the biomass and abundance estimates were 4.7 million tonnes and 17.4 billion individuals respectively. The respective biomass estimates at the traditional spawning grounds off Karmøy (59°-59°30N) and at the spawning grounds farther south (57°-59°N) were 56.000 tonnes and 84.000 tonnes at the highest. The 1992 and 1991 year classes predominated the spawning stock with 44.4% and 24.4% respectively, but the proportion of 1991 year class tended to increase northwards from 62°N. The body length and condition factor of abundant year classes tended to increase southwards. The temperature increased with depth. In addition it tended to decrease northwards and southwards from 62°N at all depths. North of 61°N the herring mainly spawned at depths between 100-200 m with ambient temperatures at 7-9°C. South of 61°N the majority of the herring spawned at depths below 75 m with temperatures at 5-7°C. The spawning temperatures in all areas seemed somewhat higher in 2000 compared with the two previous years.