Size and condition of mackerel in research vessel trawl hauls versus commercial purse seine catches: implications for acoustic biomass estimation ...

• Main Authors: Slotte, Aril, Dankert Skagen, and Svein A. Iversen
• Format: Conference Object
• Language: unknown
• Published: ASC 2006 - Theme session I 2024
• Subjects: Fisheries and aquaculture; Technologies and data; Norwegian Sea; Northeast Atlantic
• Online Access: https://dx.doi.org/10.17895/ices.pub.25258864; https://ices-library.figshare.com/articles/conference_contribution/Size_and_condition_of_mackerel_in_research_vessel_trawl_hauls_versus_commercial_purse_seine_catches_implications_for_acoustic_biomass_estimation/25258864

No abstracts are to be cited without prior reference to the author.In September, after the summer feeding has ceased, the Northeast Atlantic mackerel (Scomber scombrus) stock tends to aggregate in ICES Area IVa before they start to migrate southwards in December-February towards the spawning grounds. It is during this autumn period that the Norwegian purse seine fleet catch the mackerel in the southern part of the Norwegian Sea and the northern part of the North Sea (IVa). Since 1999 IMR has also carried out annual acoustic surveys to estimate the biomass concurrently with this fishery. During these surveys the mackerel has been sampled with a small pelagic trawl (20 m opening) at a speed of 3-3.5 knots, and the age, length and weight has been measured for use in the biomass estimation. In the present study we demonstrate that the size, both in terms length (mean length and length at age) and condition (weight at length), of mackerel caught in the research vessel trawl hauls is significantly lower than that ...