Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2013 UWTV Survey Report and catch options for 2014

Abstract

This report provides the main results and findings of the twelfth annual underwater television on the Aran, Galway Bay and Slyne head Nephrops grounds, ICES assessment area; Functional Unit 17. The survey was multi-disciplinary in nature collecting UWTV, fishing, CTD and other ecosystem data. In total 31 UWTV stations were successfully completed in a randomised isometric grid design at 3.5nmi or 6.5km intervals over the known range of the stock on the Aran Grounds. The mean burrow density observed in 2013, adjusted for edge effect, was 0.32 burrows/m². The final krigged burrow abundance estimate was 317 million burrows with a CV (or relative standard error) of 4 %. Abundance estimates have fluctuated considerably over the time series. The abundance decreased significantly in 2012 and the 2013 estimate was 2% lower and the lowest estimate in the 12 year time series. Raised abundance estimates for Galway Bay and Slyne Head were also low for those areas. Using the 2013 abundance estimate together with updated parameters for mean weight and proportions of removals retained implies 2014 total catch advice fishing at Fmsy (=F35%spr) of 699 tonnes which results in landings of no more than 591 tonnes. Nephrops accounted for approximately 70% of the benthic catch by weight from 7 beam trawl tows. The observed length frequency and maturity of female Nephops caught was similar to previous years. Virgilaria mirabilis was the most common of the two sea-pen species observed on the UWTV footage (Pennatula phosphorea was also present).