A longline survey for spurdog distribution and life history along the Norwegian coast

Abstract

To improve spatiotemporal data collection and inform future spurdog Squalus acanthias stock assessment, a new dedicated longline survey was initiated in 2021 in coastal waters of southern Norway. The survey comprised a mixture of randomly predefined stations to facilitate unbiased abundance estimates and supplementary stations including informant putative hotspots. During 25 survey days in autumn 2021, 287 stations were sampled, of which 280 were categorized as “satisfactory” in terms of gear quality deployment. Spurdog catches (n = 954) were more abundant in southeast coastal shallower waters (19–150 m). No length, sex, or maturity stratified schooling behavior was found with increasing catches. Females were more abundant and larger than males, but males were older. Growth and reproduction parameters were within ranges reported for the stock. Our results provide valuable input for spurdog survey designs with regards to optimizing boat time, location of stations, and biological sampling protocols. The survey provides important data for monitoring the spurdog stock and other data-limited species, especially considering the newly re-opened spurdog fishery but also to study possible future effects of climatic changes on spurdog distribution.