Browsing Nephrops Under Water TV Surveys by Author "Murphy, Á."
Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2014 UWTV Survey Report and catch options for 2015.Hehir, I.; Doyle, J.; Lordan, C.; O'Cuaig, M.; Hannify, O.; Fitzgerald, R.; O'Connor, S.; Keith, M.; Murphy, Á.; Sheridan, M.; et al. (Marine Institute, 2014-10)This report provides the main results and findings of the thirteenth 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 33 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 2014, adjusted for edge effect, was 0.29 burrows/m². The final krigged burrow abundance estimate was 287 million burrows with a CV (or relative standard error) of 4 %. Abundance estimates have fluctuated considerably over the time series. The 2014 abundance estimate was 9% lower than in 2013 and the lowest estimate in the 13 year time series. Raised abundance estimates for Galway Bay and Slyne Head were also low for those areas. Using the 2014 abundance estimate together with updated parameters for mean weight and proportions of removals retained implies catch advice, fishing at Fmsy (=F35%spr), of 584 tonnes and landings of 524 tonnes in 2015. Nephrops accounted for approximately 70% of the benthic catch by weight from 5 beam trawl tows. The relatively high numbers caught around 15 CL mm (carapace length) may indicate strong incoming recruitment. Virgilaria mirabilis was the most common of the two sea-pen species observed on the UWTV footage. Funiculina quadrangularis was observed at one station on the Slyne Head Nephrops ground.
Porcupine Bank Nephrops Grounds (FU16) 2014 UWTV Survey Report and catch options for 2015Doyle, J.; Lordan, C.; O'Cuaig, M.; Hannify, O.; Murphy, Á.; Sheridan, M.; Vila, Y. (Marine Institute, 2014-10)This report provides the results of the third underwater television on the ‘Porcupine Bank Nephrops grounds’ ICES assessment area; Functional Unit 16. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. In total 67 UWTV stations were successfully completed in a randomised 6 nautical mile isometric grid covering the full spatial extent of the stock. The mean burrow density observed in 2014, adjusted for edge effect, was 0.10 burrows/m². The final krigged abundance estimate was 722 million burrows with a relative standard error of 3% and an estimated stock area of 7,108km2. The abundance estimate was 6% lower than in 2013. Landings options at various different fishing mortalities were calculated in line with the recommendations of WKNEPH 2013. Fishing at Fmsy in 2015 implies catches of 1,850 t which close to the 2014 catch limit. This is because of an increase in average mean weight of the landings. The three species of sea-pen; Virgularia mirabilis, Funiculina quadrangularis and Pennatula phosphorea, were all observed during the survey. Trawl marks were also observed on over half of the stations surveyed.