Measuring lumps: Optimising sampling of the commercial landings of lumpfish (Cyclopterus lumpus) in Iceland

Lumpfish (Cyclopterus lumpus) are the target of commercial fisheries in several countries. However, the collection of biological data for stock assessment purposes is both logistically difficult and expensive. The fishery takes place far from major population centres, over a wide geographical area, and, the roe is extracted at sea and the carcass is not landed in the majority of countries where lumpfish is fished commercially. In Iceland, a new regulation was introduced in 2012 making it mandatory to land the carcass, which led to changes within the industry that made the collection of biological data feasible, and a sampling programme was fully implemented by 2014. This study examines the precision of the sampling scheme and looks for areas in which improvements could be made. The female lumpfish landed by the fishery fell into a narrow length distribution, with the majority of fish between 36 and 47 cm total length. Average length of fish caught in the south-west (Faxaflói) was greater than fish caught on the north coast, highlighting the need to sample over the geographical extent of the fishery. A sample size of 20 fish was sufficient for a reasonably precise estimate of the length frequency of the fish caught by an individual boat. Individual boats caught fish of similar size over time, thus repeated sampling of the same boat should not be considered as separate samples. Fish stored on ice lost ~1.5–2.5% of their weight per day. From 2015–2020, measurements were taken from > 18% of the boats targeting female lumpfish; increasing the sampling effort would lead to only small increases in precision. This analysis provides valuable information in which to base future sampling schemes in other lumpfish fisheries.