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Nephrops Under Water TV Surveys

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  • Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2017 UWTV Survey Report and catch options for 2018

    Lordan, C.; Doyle, J.; Butler, R.; Sugrue, S.; Allsop, C.; O'Connor, S.; Vacherot, J.P. (Marine Institute, 2017)
    This report provides the main results and findings of the fifteenth 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 2017 a total of 40 UWTV stations were successfully completed, 31 on the Aran Grounds, 5 on Galway Bay and 4 on Slyne Head patches. The mean burrow density observed in 2017, adjusted for edge effect, was medium at 0.29 burrows/m². The final krigged burrow abundance estimate for the Aran Grounds was 343 million burrows with a CV (or relative standard error) of 3 %. The final abundance estimate for Galway Bay and Slyne Head was 25 and 11 million burrows with CVs of 7% and 3% respectively. The total abundance estimates have fluctuated considerably over the time series. The 2016 combined abundance estimate was 32% lower than in 2015 and at 379 million and is below the MSY Btrigger (540 million). Using the 2017 abundance estimate and updated stock data implies catch of 551 tonnes and landings of 513 tonnes in 2018 when MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2014–2016). Virgilaria mirabilis was the only sea-pen species observed on the UWTV footage. Trawl marks were present at 20% of the Aran stations surveyed.
  • Porcupine Bank Nephrops Grounds (FU16) 2017 UWTV Survey Report and catch options for 2018

    Lordan, C.; Doyle, J.; Butler, R.; Sugrue, S.; Allsop, C.; O’Connor, S.; Vacherot, J.P. (Marine Institute, 2017)
    This report provides the results of the fifth 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 63 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 2017, adjusted for edge effect, was 0.12 burrows/m². The final krigged abundance estimate was 850 million burrows with a relative standard error of 5% and an estimated stock area of 7,134 km2. The 2017 abundance estimate was 11% lower than in 2016. Using the 2017 estimate of abundance and updated stock data implies catch of 2,734 tonnes and landings of 2,734 tonnes in 2017 when MSY approach is applied (assuming that all catch is landed). The three species of sea-pen; Virgularia mirabilis, Funiculina quadrangularis and Pennatula phosphorea, were all observed during the survey. The deepwater sea-pen Kophobelemnon stelliferum was also observed and its presence/absence mapped from the available time-series. Trawl marks were also observed on 43% of the stations surveyed.
  • Western Irish Sea Nephrops Grounds (FU15) 2017 UWTV Survey Report and catch options for 2018

    Clements, A.; Doyle, J.; Lordan, C.; Lundy, M.; McCorriston, P.; McArdle, J.; McCausland, I.; Burns, G.; Schön, P.J. (Marine Institute, 2017)
    This report provides the main results and findings of the 15th 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 2017 design consisted of a randomised isometric grid of 100 stations at 4.5 nautical mile intervals out over the full known extent the stock. The resulting krigged burrow abundance estimate was 5.3 billion burrows. This was a similar result of that obtained in 2006, and 4% higher than the abundance in 2016. In contrast to 2016 the spatial distribution of burrows appears more homogenous across the survey area. Overall densities are high and abundance remains stable, well above MSY Btrigger. Reducing the number of stations compared to 2011 has not affected the accuracy of the survey estimate to date. 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 2017 implies a total catch option at Fmsy (=Fmax) of 11,807 tonnes which results in landings of no more than 9,630 tonnes. The only sea-pen species observed in 2017 was Virgularia mirabilis and this was found at 16% of stations ranging from occasional to common, with high densities observed in the south-west of the ground. Trawl marks were noted at 36% of the UWTV stations.
  • FU19 Nephrops Grounds 2017 UWTV Survey and catch options for 2018

    Doyle, J.; Fitzgerald, R.; O’Brien, S.; Ryan, G.; McGeady, R.; Lordan, C. (Marine Institute, 2017)
    This report provides the main results of the eighth 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 2017 a total 41 UWTV stations were successfully completed. The mean density estimates varied considerably across the different patches. The 2017 raised abundance estimate was a 25% increase from the 2016 estimate and at 499 million burrows is above the MSY Btrigger (430 million). Using the 2017 estimate of abundance and updated stock data implies catch of 1,192 tonnes and landings of 889 tonnes in 2018 when MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2014–2016). Two species of sea pen were observed; Virgularia mirabilis and Pennatula phosphorea which have been observed on previous surveys of FU19. Trawl marks were observed at 10% of the stations surveyed.
  • The “Smalls” Nephrops Grounds (FU22) 2017 UWTV Survey Report and catch options for 2018

    O’Brien, S.; Blaszkowski, M.; Butler, R.; Fee, D.; Hernon, P.; Santana, C.; Lordan, C.; Doyle, J. (Marine Institute, 2017)
    This report provides the main results and findings of the twelfth 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. A total of 40 UWTV stations were surveyed successfully (good quality video footage) carried out over an isometric grid at 4.5nmi or 8.3km intervals. The precision, with a CV of 5%, was well below the upper limit of 20% recommended by SGNEPS 2012. The 2017 abundance estimate was 16% higher than in 2016 and at 1600 million is above the new MSY Btrigger (990 million). Using the 2017 estimate of abundance and updated stock data implies catch of 4,332 tonnes and landings of 3,784 tonnes in 2018 when MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2014–2016). Only one species of sea-pen Virgilaria mirabilis was recorded as present at the stations surveyed. Trawl marks were observed at 59% of the stations surveyed. Ten beam trawl tows were carried out providing important data on the benthic communities and size structure of the Nephrops population.
  • The Labadie, Jones and Cockburn Banks Nephrops Grounds (FU2021) 2017 UWTV Survey Report and catch options for 2018

    Doyle, J.; Fitzgerald, R.; O’Brien, S.; Ryan, G.; McGeady, R.; Lordan, C. (Marine Institute, 2017)
    This report provides the main results of the 2017 underwater television survey on the ‘Labadie, Jones and Cockburn Banks’ ICES assessment area; Functional Unit 20-21. This was the fourth survey to achieve full coverage of the full area. The 2017 survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. A total of 86 UWTV stations were completed at 6 nmi intervals over a randomised isometric grid design. The mean burrow density was 0.44 burrows/m2 compared with 0.18 burrows/m2 in 2016. The 2017 geostatistical abundance estimate was 4.4±0.01 billion a 236% increase on the abundance for 2016 with a CV of 4% which is well below the upper limit of 20% recommended by SGNEPS 2012. Highest densities were generally observed throughout the ground, and there were also high densities observed close to boundaries. Using the 2017 abundance estimate and updated stock data implies catch of 8,673 tonnes and landings of 6,553 tonnes in 2018 when MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2014–2016). One species of sea-pen were recorded as present at the stations surveyed Virgilaria mirabilis. Trawl marks were observed at 32% of the stations surveyed.
  • Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2016 UWTV Survey Report and catch options for 2017

    Doyle, J.; Lordan, C.; Stokes, D.; O'Brien, S.; Kelly, C.; Bentley, K.; Vacherot, J.P. (Marine Institute, 2016)
    This report provides the main results and findings of the fifteenth 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 2016 a total of 45 UWTV stations were successfully completed, 34 on the Aran Grounds, 7 on Galway Bay and 4 on Slyne Head patches. The mean burrow density observed in 2016, adjusted for edge effect, was medium at 0.29 burrows/m². The final krigged burrow abundance estimate for the Aran Grounds was 343 million burrows with a CV (or relative standard error) of 3 %. The final abundance estimate for Galway Bay and Slyne Head was 25 and 11 million burrows with CVs of 7% and 3% respectively. The total abundance estimates have fluctuated considerably over the time series. The 2016 combined abundance estimate was 32% lower than in 2015 and at 379 million and is below the MSY Btrigger (540 million). Using the 2016 abundance estimate and updated stock data implies catch of 489 tonnes and landings of 456 tonnes in 2017 when MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2013–2015). Virgilaria mirabilis was the only sea-pen species observed on the UWTV footage. Trawl marks were present at 20% of the Aran stations surveyed.
  • Porcupine Bank Nephrops Grounds (FU16) 2016 UWTV Survey Report and catch options for 2017

    Doyle, J.; Lordan, C.; Fitzgerald, R.; O'Brien, S.; Allsop, C.; Kelly, C.; McArdle, J. (Marine Institute, 2016)
    This report provides the results of the fourth 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 65 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 2016, adjusted for edge effect, was 0.13 burrows/m². The final krigged abundance estimate was 958 million burrows with a relative standard error of 4% and an estimated stock area of 7,108km2. The 2016 abundance estimate was 32% higher than in 2014. There was no UWTV survey in 2015 due to vessel breakdown prior to survey. Using the 2016 estimate of abundance and updated stock data implies catch of 3,100 tonnes and landings of 3,100 tonnes in 2017 when MSY approach is applied (assuming that all catch is landed). The three species of sea-pen; Virgularia mirabilis, Funiculina quadrangularis and Pennatula phosphorea, were all observed during the survey. The deepwater sea-pen Kophobelemnon stelliferum was also observed and its presence/absence mapped from the available time-series. Trawl marks were also observed on 30% of the stations surveyed
  • Western Irish Sea Nephrops Grounds (FU15) 2015 UWTV Survey Report and catch options for 2016

    Clements, A.; Doyle, J.; Lordan, C.; Brown, V.; Doran, S.; McArdle, J.; McCausland, I.; McCorriston, P.; Simpson, S.; Schon, J. (Marine Institute and Agri-Food and Bioscience Institute, 2015)
    This report provides the main results and findings of the 13th annual underwater television survey on the ‘Irish sea west Nephrops grounds’ ICES assessment area, Functional Unit 15.
  • The “Smalls” Nephrops Grounds (FU22) 2015 UWTV Survey Report and catch options for 2016

    Lordan, C.; Doyle, J.; Fitzgerald, R.; O’Connor, S.; Blaszkowski, M.; Butler, R. (Marine Institute, 2015)
    This report provides the main results and findings of the tenth 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. A total of 33 UWTV stations were surveyed successfully (good quality video footage) carried out over an isometric grid at 4.5nmi or 8.3km intervals. Of the planned stations 17% (7) could not be completed due to very poor or nil visibility conditions encountered at seabed. For these stations density estimates were filled-in using and average of historic values within 2nmi. The resulting krigged burrow abundance estimate for the Smalls ground decreased by 16% relative to 2014. The final abundance estimate was 1,363 million. The precision, with a CV of 7%, was well below the upper limit of 20% recommended by SGNEPS 2012. Using the 2015 estimate of abundance and updated stock data implies catch of 3,027 tonnes and landings of 2634 tonnes in 2016 fishing at Fmsy (assuming that all catch is landed). Only one species of sea pen Virgilaria mirabilis was recorded as present at the stations surveyed. Trawl marks were observed at 12% of the stations surveyed.
  • The Labadie, Jones and Cockburn Banks Nephrops Grounds (FU2021) 2015 UWTV Survey Report and catch options for 2016

    Lordan, C.; Doyle, J.; Fitzgerald, R.; O’Connor, S.; Blaszkowski, M.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Butler, R.; Sheridan, M.; Simpson, S.; Blandon, A.; Meakins, B. (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.
  • FU19 Nephrops Grounds 2015 UWTV Survey and catch options for 2016

    Lordan, C.; Doyle, J.; Fitzgerald, R.; O’Connor, S.; Blaszkowski, M.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Butler, R.; Sheridan, M.; Simpson, S. (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.
  • Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2015 UWTV Survey Report and catch options for 2016

    Doyle, J.; Lordan, C.; Fitzgerald, R.; O’Connor, S.; Fee, D.; Butler, R.; Stokes, D.; Ni Chonchuir, G.; Gallagher, J.; Sheridan, M.; Simpson, S. (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:
  • The “Smalls” Nephrops Grounds (FU22) 2014 UWTV Survey Report and catch options for 2015

    Lordan, C.; Doyle, J.; Fitzgerald, R.; O'Connor, S.; Blaszkowski, M.; Simpson, S. (Marine Institute, 2014-10)
    This report provides the main results and findings of the ninth 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. A total of 52 stations UWTV stations were carried out over an isometric grid at 4.5nmi or 8.3km intervals. The krigged burrow abundance estimate for the Smalls ground increased by 22% relative to 2013 and was the highest in the 9 year time series. The final abundance estimate was 1,622 million with a CV of 8% which is well below the upper limit of 20% recommended by SGNEPS 2012. Using the 2014 estimate of abundance and recent mean weight and discard data would imply total catches at Fmsy in 2015 of 3,797t. This implies landings of 3,409 tonnes. Temperature on the seabed varied by 2oC over the Nephrops ground with coldest values around 9.4oC in the deepest part of the area. Only one species of sea pen Virgilaria mirabilis was recorded as present at 46% of the stations surveyed. Trawl marks were observed at 28% of the stations surveyed.
  • The Labadie, Jones and Cockburn Banks Nephrops Grounds (FU2021) 2014 UWTV Survey Report and catch options for 2015

    Doyle, J.; Lordan, C.; Hehir, I.; Fitzgerald, R.; O'Connor, S.; Keith, M.; Sheridan, M. (Marine Institute, 2014-10)
    This report provides the main results of the 2014 underwater television survey on the ‘Labadie, Jones and Cockburn Banks’ ICES assessment area; Functional Unit 20-21. Some exploratory UWTV stations were carried out in 2006 and 2012. In 2013 ~60% of the ground was surveyed. This was the first survey to achieve full coverage of the newly defined area. The 2014 survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. A randomised isometric grid design was employed with 98 UWTV stations at 6.0 nmi intervals. The mean burrow density was 0.19 burrows/m2 compared with 0.16 burrows/m2 in 2013. The 2014 geostatistical abundance estimate was 2.1±0.1 billion a 26% increase on the extrapolated abundance for 2013. Highest densities were general observed towards the middle of the ground, but there were also high densities observed close to boundaries. Using the 2014 abundance and recent fisheries data it is possible to estimate harvest ratios consistent with various landings options. These can be used by ICES to provide catch options for 2015. The occurrence of sea-pens and trawl marks on the UWTV footage and processed CTD is also presented.
  • FU19 Nephrops Grounds 2014 UWTV Survey and catch options for 2015

    Lordan, C.; Doyle, J.; Fitzgerald, R.; O'Connor, S.; Blaszkowski, M.; Simpson, S. (Marine Institute, 2014-10)
    This report provides the main results and findings of the fifth 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 2014 a total 40 UWTV stations were successfully completed. The mean density estimates varied considerably across the different patches. The 2014 raised abundance estimate of 636 million burrows was a 31% increase from the 2013 estimate. Taking into account the uncertainty (CV of 15%) this is not significantly different from abundance estimates since 2011. Using the 2014 abundance and recent mean weight and discard parameters would imply total catches of 1119 t fishing at Fmsy in 2015. Based on recent discard patterns which are high in this area; 715 t would be landings and 404 t would be discards. Two species of sea pen were observed; Virgularia mirabilis and Pennatula phosphorea, both species have been observed on previous surveys of FU19.
  • 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.; Vila, Y. (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 2015

    Doyle, 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.
  • Western Irish Sea Nephrops Grounds (FU15) 2014 UWTV Survey Report and catch options for 2015

    Ligas, A.; Doyle, J.; Lordan, C.; Brown, V.; Doran, S.; McArdle, J.; McCausland, I.; McCorriston, P.; Simpson, S.; Schon, J. (Marine Institute and Agri-Food and Bioscience Institute, 2014-10)
    This report provides the main results and findings of the 12th 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 2014 design consisted of a randomised isometric grid of 101 stations at 4.5 nautical mile intervals out over the full known extent the stock. The resulting krigged burrow abundance estimate was 4.6 billion burrows. This was a similar result of that obtained in 2009, and slightly higher than the abundance in 2013. The spatial distribution shows a decline in abundance in the south-eastern area compared to 2013 figure, while a slight increase is apparent in the North and in the middle of the area. Overall densities remain high and abundance remains relatively stable, well above MSY Btrigger. Reducing the number of stations compared to 2011 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 2015 implies a total catch option at Fmsy (=Fmax) of 9,922 tonnes which results in landings of no more than 8,223 tonnes. The only sea-pen species observed in 2014 was Virgularia mirabilis and the frequency of occurrence was lower than the average during the investigated period, but higher than in 2013. Trawl marks were noted at 24% of the UWTV stations.
  • 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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