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    AuthorDoyle, J. (5)Lordan, C. (5)Hehir, I. (4)Allsop, C. (2)Blaszkowski, M. (2)Burke, C. (2)Butler, R. (2)Fitzgerald, R. (2)O’Connor, S. (2)O’Donovan, S. (2)View MoreSubjectbenthos (5)geostatistics (5)
    Nephrops norvegicus (5)
    stock assessment (5)
    underwater television (UWTV) (5)
    Porcupine Bank (1)View MoreDate Issued
    2013 (5)

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

    Lordan, C.; Doyle, J.; Hehir, I.; Allsop, C.; Butler, R.; Burke, C. (Marine Institute, 2013)
    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).
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    The “Smalls” Nephrops Grounds (FU22) 2013 UWTV Survey Report and catch options for 2014

    Doyle, J.; Lordan, C.; Hehir, I.; Fitzgerald, R.; O’Connor, S.; O’Donovan, S.; Salaun, M. (Marine Institute, 2013)
    This report provides the main results and findings of the eighth annual underwater television survey on the ‘Smalls grounds’ ICES assessment area; Functional Unit 22. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. The sampling intensity was reduced this year from around 100 stations in the past to 51 stations this year. A randomised isometric grid design was employed with UWTV stations at 4.5nmi or 8.3km intervals. Previously a 3.0 nmi square grid was used. The krigged burrow abundance estimate for the Smalls ground has decreased by 19% relative to 2012 and was the fourth highest in the 8 year history of the survey. Abundance estimates have been fairly stable over the time series. The 2013 randomised isometric grid design result in a CV (or relative standard error) of 7% which is well below the upper limit of 20% recommended by SGNEPS 2012. Total catches and landings options at various different fishing mortalities were calculated and fishing at Fmsy in 2014 implies a total catch option at Fmsy (=Fmax) of 2,937 tonnes which results in landings of no more than 2,674 tonnes.
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    Western Irish Sea Nephrops Grounds (FU15) 2013 UWTV Survey Report and catch options for 2014

    Doyle, J.; Lordan, C.; Ligas, A.; Brown, V.; Leocadio, A.; McCausland, I.; McCorriston, P.; Service, M.; Stewart, P.; Schön, P.J. (Marine Institute & Agri-Food and Biosciences Institute, 2013)
    This report provides the main results and findings of the eleventh annual underwater television survey on the ‘Irish sea west Nephrops grounds’ ICES assessment area, Functional Unit 15. The survey was multi-disciplinary in nature collecting UWTV and other ecosystem data. The 2013 design consisted of a randomised isometric grid of 80 stations at 5 nautical mile intervals out over the full known extent the stock. The resulting krigged burrow abundance estimate was 4.3 billion burrows. This was a 16% decrease relative to 2012. The spatial distribution shows higher abundance in the south of the area and a larger decline in abundance is apparent in the North. Overall densities remain high and abundance remains relatively stable, well above MSY Btrigger. Reducing the number of stations in 2013 is not expected to have significantly affected the accuracy of the survey estimate. The CV (or relative standard error) of 3% is in line with previous estimates and well below the upper limit of 20% recommended by SGNEPS 2012. Total catches and landings options at various different fishing mortalities were calculated and fishing at Fmsy in 2014 implies a total catch option at Fmsy (=Fmax) of 9,914 tonnes which results in landings of no more than 8,244 tonnes. The only sea-pen species observed in 2013 was Virgularia mirabilis and the frequency of occurrence was lower than in 2012. Trawl marks were noted at 43% of the UWTV stations.
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    Porcupine Bank Nephrops Grounds (FU16) 2013 UWTV Survey Report and catch options for 2014

    Lordan, C.; Doyle, J.; O'Connor, S.; Hehir, I.; Fitzgerald, R.; Blaszkowski, M.; O'Sullivan, D.; O’Donovan, S.; Salaun, M.; Stewart4, P. (Marine Institute, 2013)
    This report provides the results of the second 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 68 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 2013, adjusted for edge effect, was 0.106 burrows/m². The final krigged abundance estimate was 768 million burrows with a relative standard error of 4% and an estimated stock area of 7,100km2. The abundance estimate was 2% lower than in 2012. Landings options at various different fishing mortalities were calculated in line with the recommendations of WKNEPH 2013. Fishing at Fmsy in 2014 implies a slight increase in the TAC from 1,800 t to 1,850 t. This increase is mainly due to an increase in average mean weight of the landings. The three species of sea-pen found on muddy habitat in Irish waters are 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.
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    FU19 Nephrops Grounds 2013 UWTV Survey and catch options for 2014

    Lordan, C.; Doyle, J.; Hehir, I.; O’Sullivan, D.; Allsop, C.; O’Connor, S.; Blaszkowski, M.; Butler, R.; Burke, C.; Stewart, P. (Marine Institute, 2013)
    This report provides the main results and findings of the fourth underwater television survey of the various Nephrops grounds in Functional Unit 19. The survey was multi-disciplinary in nature collecting UWTV, CTD, multi-beam and other ecosystem data. In 2013 a total 40 UWTV stations were successfully completed. Adjusted burrow density estimates varied considerably across the different grounds. The 2013 raised abundance estimate of 397 million burrows is a 20% decrease from the 2012 estimate. Taking into account the uncertainty (CV of 17%) this is not significantly different from abundance estimates in 2011 or 2012. Using the 2013 abundance and recent mean weight and discard implies 2014 total catch advice fishing at Fmsy (=F35%spr) of 618 tonnes which results in landings of no more than 521 tonnes.
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