• Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2012 UWTV Survey Report and catch options for 2013

      Lordan, Colm; Doyle, Jennifer; Hehir, Imelda; Fee, Dermot; Allsop, Chris; O'Neill, Ross (Marine Institute, 2012)
      This report provides the main results and findings of the eleventh 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. The sampling intensity was reduced this year from around 75 stations in the past to 31 on the Aran grounds. A randomised isometric grid design was employed with UWTV stations at 3.5nmi or 6.5km intervals. Previously a 2.25 nmi square grid was used. The kigged burrow abundance estimate declined by 34% relative to 2011 with a CV (or relative standard error) of 5 %. Abundance estimates have fluctuated considerably over the time series but the 2012 abundance is the lowest in the 11 year history of the survey. Four UWTV stations were carried out on the Galway Bay and 3 on the Slyne Head Nephrops grounds. Raised abundance estimates for Galway Bay and Slyne Head are provided based on improved knowledge of the boundaries of those areas. Nephrops accounted for 85% of the benthic catch by weight from 4 beam trawl tows. The observed length frequency and maturity of female Nephops caught was similar to previous years. Various further investigations needed before the next ICES benchmark are discussed.
    • 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).
    • 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.
    • 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:
    • 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.
    • 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.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds (FU17) 2018 UWTV Survey Report and catch scenarios for 2019

      Doyle, J.; O’ Brien, S.; Ryan, G.; Galligan, S.; Hernon, P.; Aristegui, M.; Vacherot, J.P. (Marine Institute, 2018)
      This report provides the main results and findings of the seventeenth 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 2018 a total of 43 UWTV stations were successfully completed, 33 on the Aran Grounds, 5 on Galway Bay and 5 on Slyne Head patches. The mean burrow density observed in 2018, adjusted for edge effect, was medium at 0.40 burrows/m². The final krigged burrow abundance estimate for the Aran Grounds was 488 million burrows with a CV (relative standard error) of 3%. The final abundance estimate for Galway Bay and Slyne Head was 33 million in both grounds with CVs of 17% and 12% respectively. The total abundance estimates have fluctuated considerably over the time series. The 2018 combined abundance estimate was a 37% increase compared to in 2017 and at 554 million burrows and is above the MSY Btrigger reference point (540 million burrows). Using the 2018 abundance estimate and updated stock data implies catch of 1002 tonnes and landings of 916 tonnes in 2019 when the MSY approach is applied (assuming that discard rates and fishery selection patterns do not change from the average of 2015–2017). Virgularia mirabilis was the only sea-pen species observed on the UWTV footage. Trawl marks were present at 9% of the Aran stations surveyed.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2006 UWTV Survey Report

      Lordan, C; Doyle, J; Sacchetti, F; O'Driscoll, D; Heir, I; Smith, T; Allsop, C (Marine Institute, 2007)
      The Nephrops fishery “at the back of the Aran Islands” is the mainstay of the Ros a Mhíl fleet and sustaining this valuable fishery would be at the heart of any management plan for fisheries in the area. In 2006 the fifth in a series of annual UWTV survey was completed, and the results of that survey together with a synthesis and analysis of the results were published. The survey is multidisciplinary in nature collecting data on burrow abundances from UWTV, Nephrops biological data from beam trawls, oceanographic data from CTD, sediment data, multi-beam and other habitat data. A geostatistical analysis indicates that burrow densities and abundances have fluctuated considerably in space and time. Highest densities occurred in 2004 with the lowest densities in the 2006 survey. There may be a negative relationship between abundance in landings in the autumn and a positive relationship between observed densities and landings the following spring.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2007 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2008)
      In 2007 the sixth in a series of annual UWTV survey was complete and the results of that survey together with a synthesis and analysis of the results. A geostatistical analysis indicates that burrow densities and abundances have fluctuated considerably in space and time. The highest densities occurred in 2004 and the lowest densities in the 2006.The 2007 survey shows an increase in burrow density. Using the survey directly for assessment and management is not yet possible. However, there appears to a negative relationship between abundance and landings in the autumn and a positive relationship between observed densities and landings the following spring. The relationship between abundance and landings is not as clear. There is no serious concern about the stock given the recent survey abundance.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2008 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2009-05)
      In 2008 the seventh in a series of annual UWTV survey was complete and the results of that survey together with a synthesis and analysis of the results is presented. A geostatistical analysis indicates that burrow densities and abundances have fluctuated considerably in space and time. The highest densities occurred in 2004 and the lowest densities in 2008.The 2008 survey shows a decrease in burrow density to the lowest observed. Using the survey directly for assessment and management has been discussed at WKNEPHTV (2007) and at SGNEP (2009).This stock was a focus at the benchmark workshop on Nephrops assessment held in Aberdeen WKNEPH, (2009). There appears to a negative relationship between abundance and landings in the autumn and a positive relationship between observed densities and landings the following spring. There is some concern about the stock given the most recent survey abundance observed to date. The time series is short and to date survey estimates have fluctuated across a large dynamic range.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2009 UWTV Survey Report

      Lordan, C; Doyle, J (Marine Institute, 2009-09)
      The prawn (Nephrops norvegicus) are common around the Irish coast occurring in geographically distinct sandy/muddy areas were the sediment is suitable for them to construct their burrows. The Irish Nephrops fishery is extremely valuable with landings in recent years worth around €30m at first sale supporting an important indigenous processing industry. The Nephrops fishery “at the back of the Aran Islands” can be considered the mainstay of the Ros a Mhíl fleet. Without this Nephrops fishery the majority of vessels in the fleet would cease being economically viable (Meredith, 1999). Given these socio-economic realities, good scientific information on stock status to enable sustainable management of the resources are urgently required. This is the eight data point in a time series of UWTV surveys on the ‘Aran grounds’. The survey covers three distinct mud patches; the Aran Ground, Galway Bay and Slyne Head. These have approximate areas of 940, 41 and 26sq.km respectively. In 2009 this survey was used to develop catch options for the stock using a bias corrected survey estimate as an absolute measure of stock size and recent discard rates and mean weight to forecast catch (ICES, 2009a). This report details the results of the 2009 survey and updates the catch option table using the most recent survey estimate.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2010 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2011-05)
      This is the ninth data point in a time series of UWTV surveys on the ‘Aran grounds’. The survey covers three distinct mud patches; the Aran Ground, Galway Bay and Slyne Head. These have approximate areas of 940, 41 and 26 km2 respectively. For the first time in 2009 this survey was used to develop catch options for the stock using a bias corrected survey estimate as an absolute measure of stock size and recent discard rates and mean weight to forecast catch (ICES, 2009a). This report details the results of the 2010 survey and updates the catch option table using the most recent survey estimate.
    • Aran, Galway Bay and Slyne Head Nephrops Grounds 2011 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer; Bunn, Robert; Fee, Dermot; Allsop, Chris (Marine Institute, 2011-10)
      This report provides the main results and findings of the tenth annual underwater television on the ‘Aran grounds’ ICES assessment area; Functional Unit 17. The survey was multi-disciplinary in nature collecting UWTV, fishing, CTD and other ecosystem data. In total 76, 10 and 7 UWTV stations were successfully completed on the Aran, Galway Bay and Slyne Head Nephrops Grounds. The observed abundance estimate for the main Aran ground has declined by 23% relative to 2010. Abundance estimates have fluctuated over the time series. The 2011 abundance is the third lowest in the 10 year history of the survey. This is not a cause for immediate concern about the stocks sustainability. Raised abundance estimates for Galway Bay and Slyne Head are provided for the first time based on improved knowledge of the boundaries of those areas. Nephrops accounted for 26% of the catch weight from 10 beam trawl tows. The observed length frequency and maturity of female Nephops caught was similar to previous years. Various further investigations needed before the next ICES benchmark are discussed.
    • Celtic Sea Nephrops Grounds 2007 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2008-05)
      This is the second in a time series of UWTV surveys on the ‘Smalls grounds’. The 2006 survey covered the distinct mud patches of the Smalls Grounds and also indicator stations on the Labadie Bank, Nymphe Bank and Seven Heads, whereas the survey 2007 covered the Smalls Grounds only due to poor weather. This report details the results of the surveys on the Smalls Grounds to date.
    • Celtic Sea Nephrops Grounds 2008 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2009-05)
      This is the third in a time series of UWTV surveys on the ‘Smalls grounds’. The 2006 survey covered the distinct mud patches of the Smalls Grounds and also indicator stations on the Labadie Bank, Nymphe Bank and Seven Heads, whereas the 2007 and 2008 survey covered the Smalls Grounds only due to poor weather and time contraints. This report details the results of the surveys on the Smalls Grounds only to date.
    • Celtic Sea Nephrops Grounds 2009 UWTV Survey Report

      Lordan, C; Doyle, J (Marine Institute, 2010-05)
      This is the fourth in a time series of UWTV surveys on the ‘Smalls grounds’. The 2006 survey covered the distinct mud patches of the Smalls Grounds and also indicator stations on the Labadie Bank, Nymphe Bank and Seven Heads, whereas the 2007 to 2009 survey covered the Smalls grounds only due to poor weather and time constraints. This report details the results of the 2009 survey for the Smalls ground Nephrops stock.
    • Celtic Sea Nephrops Grounds 2010 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer (Marine Institute, 2011-04)
      This is the fifth in a time series of UWTV surveys on the ‘Smalls grounds’. The 2006 survey covered the distinct mud patches of the Smalls Grounds and also indicator stations on the Labadie Bank, Nymphe Bank and Seven Heads, whereas the 2007 to 2010 survey covered the Smalls grounds only due to poor weather and time contraints. This report details the results of the 2010 survey for the Smalls ground Nephrops stock.
    • Celtic Sea Nephrops Grounds 2011 UWTV Survey Report

      Doyle, Jennifer; Lordan, Colm; Fitzgerald, Ross; O’Connor, Sean; Fee, Dermot; Nolan, Cormac; Hayes, Joan (Marine Institute, 2011)
      The prawn (Nephrops norvegicus) are common in the Celtic Sea occurring in geographically distinct sandy/muddy areas were the sediment is suitable for them to construct their burrows. The Celtic Sea area (Functional Units 19-22) supports a large multi-national targeted Nephrops fishery mainly using otter trawls and yielding landings in the region of ~6,000 t annually over the last decade (ICES, 2011). Nephrops spend a great deal of time in their burrows and their emergence behaviour is influenced many factors; time of year, light intensity and tidal strength. Underwater television surveys and assessment methodologies have been developed to provide a fishery independent estimate of stock size, exploitation status and catch advice (ICES, 2009 & 2011).This is the sixth in a time series of UWTV surveys in the Celtic Sea carried out by the Marine Institute, Ireland. The 2011 survey was multi disciplinary in nature and this report details the final UWTV results of the 2011 survey and also documents other data collected during the survey.
    • FU19 Nephrops Grounds 2011 UWTV Survey Report

      Lordan, Colm; Doyle, Jennifer; Fitzgerald, Ross (Marine Institute, 2011)
      This report provides the main results and findings of the second underwater television survey of the various Nephrops grounds in Functional Unit 19. The survey was multi-disciplinary in nature collecting UWTV, CTD and other ecosystem data. In total 35 UWTV stations were successfully completed on the following Nephrops grounds: Bantry Bay, Galley, Cork Channels and Helvick. Raised abundance estimates for these grounds are provided for the first time based on improved knowledge of the boundaries of those areas.
    • 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.