Potential sources of unaccounted mortality in the fishery for Norwegian spring spawning herring

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The stock of Norwegian spring spawning herring (NSSH) is managed and fished by 5 different parties. These are the EU, Faroe Islands, Iceland, Norway and Russia. The most common gears are purse seine and pelagic trawl. The fishery is regulated by quota, and to prevent the fishery exceeding the quota, landings are recorded. Taking account of how the fishery is conducted, potential sources of unaccounted mortality may be identified. In this paper we will focus on the possibility of unaccounted mortality caused by errors in the landing figures, error concerning the water content in herring deliveries and errors concerning conversion factors between fillets and live weight of herring.