Scottish Marine and Freshwater Science Vol 6 No 7: Collection of bycatch data for spurdog (Squalus acanthias) in the North Minch fishery: Report of Fishing Industry Science Alliance (FISA) Project 02/13

Introduction

The north-eastern Atlantic stock of spurdog ( Squalus acanthias) is assessed as being at a historical low by ICES and others ( De Oliveira et al. 2013, ICES 2014). In consequence landing spurdog has been banned via a zero Total Allowable Catch limit set throughout EU waters ( European Commission 2015). The present project was proposed to FISA after discussion with fishers from Barra and Stornoway who fish for Nephrops in the Minches and Sea of Hebrides using single or twin-rig otter trawls. According to the fishers the majority of the spurdog caught in this area are predominantly small to medium-sized male fish. Pawson et al. ( 2009) suggested that controlled fisheries for small male spurdog ( i.e. avoiding the mature female components of the stock) might not be damaging to the stocks overall so the industry are keen to explore whether a controlled by-catch fishery could be allowed.

The fishers also stated that patches of spurdog are encountered only occasionally and are hard to avoid (that is they do not occur in predictable locations). Prior to the landing ban, spurdog represented a small but valuable by-catch for the Nephrops trawl sector fishing around the western Isles at certain times of the year. Because the spurdog entangle the nets the fishers state that they would normally move away from the area and try to avoid such encounters but they do object to having to discard a saleable product when it is accidentally caught. A further important issue is that under the new ‘landings obligation’, spurdog could act as a choke species for the Nephrops fisheries.

The aims of the present project were to collect new data on the levels of spurdog by-catch, locations of by-catch and to collect biological information in terms of the sizes and sex of the fish caught in order to inform the debate on whether a controlled incidental by-catch ( i.e. not targeted) fishery could be considered. The project was funded to run over the winters of 2013/14 and 2014/15. Because not all the available budget for sampling in 2013/2014 was spent, sampling was extended to cover the spring and summer 2014.