Browsing Nephrops Under Water TV Surveys by Author "Ni Chonchuir, G."
Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2015 UWTV Survey Report and catch options for 2016Doyle, J.; Lordan, C.; Fitzgerald, R.; O’Connor, S.; Fee, D.; Butler, R.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Sheridan, M.; et al. (Marine Institute, 2015)This report provides the main results and findings of the fourteenth 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 2015 a total of 44 UWTV stations were successfully completed, 34 on the Aran Grounds and 5 on each of the Slyne Head and Galway Bay patches. The mean burrow density observed in 2015, adjusted for edge effect, was medium at 0.38 burrows/m². The final krigged burrow abundance estimate for the Aran Grounds was 480 million burrows with a CV (or relative standard error) of 6 %. The final abundance estimate for Galway Bay and Slyne Head was 56 and 20 million burrows with CVs of 15% and 4% respectively. The total abundance estimates have fluctuated considerably over the time series. The 2015 abundance estimate was 42% higher than in 2014 and at 556 million and is just above to the new MSY Btrigger (540 million). Using the 2015 abundance estimate and updated stock data implies catch of 991 tonnes and landings of 915 tonnes in 2016 fishing at Fmsy (assuming all catch is landed). Virgilaria mirabilis was the most common of the two sea-pen species observed on the UWTV footage. Pennatula phosphorea was observed at one station on the Slyne Head Nephrops ground. Key words: Nephrops norvegicus, stock assessment, geostatistics, underwater television (UWTV), benthos, CTD. Suggested citation:
FU19 Nephrops Grounds 2015 UWTV Survey and catch options for 2016Lordan, C.; Doyle, J.; Fitzgerald, R.; O’Connor, S.; Blaszkowski, M.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Butler, R.; Sheridan, M.; et al. (Marine Institute, 2015)This report provides the main results of the sixth underwater television survey of the various Nephrops patches in Functional Unit 19. The survey was multi-disciplinary in nature collecting UWTV, CTD, multi-beam and other ecosystem data. In 2015 a total 39 UWTV stations were successfully completed. The mean density estimates varied considerably across the different patches. The 2015 raised abundance estimate of 482 million burrows was a 24% decrease from the 2014 estimate. Taking into account the uncertainty (CV of 13%) there is no significant difference in abundance estimates since 2011. Using the 2015 abundance estimate and recent mean weights and discard parameters would imply total catches of 793 t fishing at Fmsy in 2016. This stock will be subject to the landing obligation in 2016 and the calculation of catch options assume that all catches will be landed in 2016. The catch can be partitioned into landings of 543 t and discards of 250 t. The estimated discards rates in FU19 are relatively high and impact of this on the catch options is discussed. One species of sea pen was observed; Virgularia mirabilis which has been observed on previous surveys of FU19.
The Labadie, Jones and Cockburn Banks Nephrops Grounds (FU2021) 2015 UWTV Survey Report and catch options for 2016Lordan, C.; Doyle, J.; Fitzgerald, R.; O’Connor, S.; Blaszkowski, M.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Butler, R.; Sheridan, M.; et al. (Marine Institute, 2015)This report provides the main results of the 2015 underwater television survey on the ‘Labadie, Jones and Cockburn Banks’ ICES assessment area; Functional Unit 20-21. This was the second survey to achieve full coverage of the full area. The 2015 survey was multidisciplinary in nature collecting UWTV, CTD and other ecosystem data. A total of 96 UWTV stations were completed at 6 nmi intervals over a randomised isometric grid design. The mean burrow density was 0.20 burrows/m2 compared with 0.19 burrows/m2 in 2014. The 2015 geostatistical abundance estimate was 2.0±0.02 billion a 2% decrease on the abundance for 2014 with a CV of 3% which is well below the upper limit of 20% recommended by SGNEPS 2012. Highest densities were general observed towards the north and southwest of the ground, and there were also high densities observed close to boundaries. Using the 2015 abundance estimate and updated stock data implies catch of 3045 tonnes and landings of 2225 tonnes. Only one species of sea pen Virgilaria mirabilis was recorded as present at the stations surveyed. Trawl marks were observed at 30% of the stations surveyed.