Lumpfish (Cyclopterus lumpus) in the Barents Sea: development of biomass and abundance indices, and spatial distribution

Little is known about lumpfish (Cyclopterus lumpus) ecology, especially its distribution in the open Barents Sea. This paper describes fluctuations in abundance and biomass indices of lumpfish based on pelagic trawl catches. This long-termmonitoring survey has been conducted between August and September since 1980. Investigations show that lumpfish is widely distributed in the pelagic waters of the Barents Sea. Relative biomass and abundance indices were calculated for the period 1980-2012. The mean annual biomass was estimated to be 48 000 t, with a maximum of 143 000 t; the estimated mean annual abundance was 53 million individuals, with a maximum of 132 million individuals. There were more juveniles than adults, with juveniles comprising 40-80% of the total abundance (average 60%). The largest concentrations of both juveniles and adults were in years with warm temperatures. The majority of fish were found in waters of 5-7 degrees C (60% of juveniles) and 4-7 degrees C (70% of adults), indicating a strong association with Atlantic water masses in the Barents Sea. Regulations on the Norwegian and Russian fisheries for prespawning lumpfish are based only on after-the-fact fishery data and, therefore, have been insufficient in preventing negative effects on the lumpfish resource from fishing. Understanding the stock fluctuations and the use of fishery-independent data may improve the precautionary approach to fishery management. The use of lumpfish indices from the scientific surveys in the Barents Sea should be implemented to strengthen the current stock assessment.