Lobster in Shetland inshore waters

Transcription

1 Lobster in Shetland inshore waters Content last updated 22nd Feb 2017 Stock: Lobster Shetland stock Management: Shetland Shellfish Management Organisation (SSMO) Lobster in Shetland inshore waters Overview The European lobster is found in most areas of the British Isles, particularly off rocky coastlines. The diet of the adults consists mainly of benthic invertebrates such as crabs, molluscs, sea urchins, polychaete worms and starfish, but may also include fish and plants. The majority of lobsters are caught in waters shallower than 30 m but they may be found as deep as 150 m. The growth rate of lobsters is highly variable. Individuals recruiting into the fishery at the minimum landing size of 87 mm carapace length in the rest of Scotland and at 90mm in the inshore waters around Shetland can be anywhere between 4 and 12 years old. The size at 50% maturity for female lobsters has been estimated from 77mm carapace length (CL) (Cefas, unpublished, 2004) to over 103mm (Laurans et al., 2009), with other intermediate estimates (Free et al, 1992; Tully et al., 2001; Lizárrago-Cubedo et al., 2003). Fecundity of lobsters is moderate; ranging from around 5000 eggs at first maturation to to for lobsters of around 120mm CL (Hepper & Gough, 1978;Latrouite et al., 1984; Bennett & Howard, 1987; Free et al.,1992; Roberts, 1992; Free, 1994; Tully et al., 2001; Lizárrago-Cubedo et al., 2003; Agnalt, 2007). Lobsters can grow very old and the potential reproductive life span of a female lobster is in excess of 40 years, although individual females are not thought to spawn every year. Amongst the largest reported lobsters in the UK are a female of 157 mm, thought to be about 72 years old, and an 11 lb (5 kg) lobster from the Hebrides estimated as 190 mm in length (MSC, 2007; Marine Scotland Science 2014). The earliest records of lobster fishing in Scotland date back to the 12th century when lobster was caught by hand using crooks and hoop nets. With the introduction of baited traps (creels), exploitation on a more commercial basis developed, and today there are important creel fisheries for the European lobster in many areas around the Scottish coast. In Shetland there is both a bycatch fishery all year round (from vessels targeting crab species) and a targeted fishery for lobster at certain times of the year (MSC, 2012). Agnalt, A. L., Fecundity of the European lobster (Homarus gammarus) off southwestern Norway after stock enhancement: do cultured females produce as many eggs as wild females? ICES J. Mar. Sci., 65: Bennett D. B. & Howard A. E. Estimates of lobster (Homarus gammarus) fecundity from east and west Britain ICES Document CM 1987/K: 47. Free, E.K., Reproductive processes in the European lobster, Homarus gammarus. PhD thesis, Univ. Southampton. 447pp. Free, E.K., Tyler, P.A.V. & Addison, J.T., Lobster (Homarus gammarus) fecundity and maturity in England and Wales. ICES CM 1992/K:43, 13pp. Hepper, B.T. & Gough, C.J., Fecundity and rate of embryonic development of the lobster, Homarus gammarus (L), off the coast of North Wales. J. du Conseil ICES, 38: Latrouite, D., Morizur, Y. & Raguenes, G., Fécondités individuelle et par recrue du homard Européen, Homarus gammarus (L.) des côtes Françaises. ICES CM1984/K:38, 18pp. Laurans, M., Fifas, S., Demaneche, S., Brérette, S. & Debec, O., O Modelling seasonal and annual variation in size at functional maturity in the European lobster (Homarus gammarus) from self-sampling data. ICES Journal of Marine Science : Lizárrago -Cubedo, H.A., Tuck, I., Bailey, N. Pierce, G.J. & Kinnear J.A.M., Comparisons of size at maturity and fecundity of two Scottish populations of the European lobster, Homarus gammarus. Fish. Res. 65: Roberts E. A Fecundity of the European lobster Homarus gammarus (L.) from the central south coast of England; p. 53. MSc thesis. University of Southampton. Tully, O., Roantree, V. & Robinson, M., Maturity, fecundity and reproductive potential of the European lobster (Homarus gammarus) in Ireland. J. Mar. Biol. Ass. U.K. 81: Stock Status less risk more risk The fishery for Lobster Homarus gammarus in Shetland inshore waters was scored as low risk. This is because as a data limited stock lobster has moderate vulnerability and LPUE shows a generally increasing population trend in recent years. Management less risk more risk The management of lobster up to the six mile limit has been scored as low risk. There is a suite of management controls that are implemented as well as back up controls that can be implemented if LPUE is found to be outside reference point levels. The enforcement of management controls is done via logbook data and occasional patrols. Bycatch less risk more risk The bycatch risk of this fishery has been scored as low risk. This is because whilst discarding of undersized lobster and other crustaceans occurs, these are released alive on hauling and survival rates are believed to be high. Catch of protected, endangered and threatened species is minimal. Ghost fishing by lost pots is not considered to be a problem.

2 Habitat less risk more risk The habitat impact of this fishery has been scored as low risk. The impact on the seabed is negligible but creels could potentially cause some abrasion to the sea floor during hauling or in particularly rough weather. Outlook Type Current Risk Status Outlook Reason Stock Low Stable/ Improving Species is characterised by a moderate vulnerability and population trends in the form of LPUE has generally been increasing over recent years. LPUE has also been above its target reference point since Management Low Stable Management controls in place are advised by analytical stock assessments, they are not precautionary but prevent over fishing and are designed to keep the fishery sustainable. Bycatch Very low Stable All undersized lobsters and crab caught are released and are thought to live. Bycatch of other species is very low and survival rate is high. Risk of ghost fishing by lost pots is considered negligible. Habitat Low Stable Static gear such as creels are known for their negligible impact on the seafloor, however there is contact with benthos and abrasion may occur during hauling or bad weather.

3 Stock Status Details less risk more risk Lobster in Shetland inshore waters is the stock within the six mile limit around Shetland (Fig 1). This stock is managed and assessed annually by the Shetland Shellfish Management Organisation (SSMO). In Marine Scotland terms the Shetland stock assessment area for lobster encompasses the seven ICES rectangles around Shetland, including the SSMO area (Fig. 1). Figure 1. Map showing Shetland, the six mile limit (SSMO area) around the isles (black line) and the Shetland stock unit as defined by Marine Scotland (blue polygon). Time-trends Data from 2014 indicates that the SSMO stock status of lobster is low risk. LPUE (kg per 100 creels) has increased generally since 2008, with a small dip in 2012and 2013, but then increasing the the highest level seen in the 15 year time series. Landings have been decreasing since 2010 until 2014 when they reached the highest ever level. Effort showed a similar decrease in recent years but as with landings an increase was seen in 2014 (Fig. 2). Figure 2. Landings, Effort and LPUE of the lobster fishery within the SSMO managed area and collected by SSMO logsheets. 95% confidence intervals are shown for LPUE. LPUE is used as a reference point for the stock and has values or levels assigned in a traffic light system. LPUE has been above the upper target reference point (i.e. green) since 2009 (NAFC, pers comm). In addition to the information from the SSMO on stock status, Marine Scotland has a stock assessment on the Shetland stock management unit as defined by them. From 2009 to 2012 fishing mortality estimates indicate that female lobster were being fished below F MSY but males were being fished over F MSY estimates (Baretto & Bailey, 2015). Stock structure and recruitment Shetland inshore lobster can be defined as the stock within the six mile limit around Shetland. Under a regulating order the Shetland Shellfish Management Organisation (SSMO) manages this crab fishery, assesses the stock and aims to promote sustainability of the shellfish fisheries around Shetland (SSMO, 2016b). Whilst managed and assessed as a separate stock, this stock is encompassed by the larger Marine Scotland Shetland stock assessment area (SSMO area is included as part of this) and there is likely to be a large degree of mixing between lobster found inside or outside the SSMO managed area, although lobsters are generally found in shallower waters. The lobster population structure around Scotland is poorly understood (Baretto & Bailey, 2015). No recruitment data is collected in Scotland or by the SSMO. Recruitment in Homarus gammarus tends to be highly variable due to the time spent in the plankton by larvae and distribution is dependent on not only hydrodynamic conditions but also behaviour (CEFAS, 2014). The stock is assessed by the SSMO using information from logsheets as well as observer sampling on board vessels (SSMO, 2015). Data gaps and research priorities The population structure of lobster stocks around Scotland is not well understood, with Marine Scotland stock units being based upon historic districts for reporting landings. Connectivity of the individual lobster stock units is not very well known (Baretto & Bailey, 2015). An improved understanding of the population structure may lead to the assessment units being redefined to better represent biologically distinct populations, however the management area under SSMO control enables better effort control and overall management of the fishery on the localised population around Shetland.

4 Baretto, E. & Bailey, N (2014) Fish and shellfish stocks 2014 Edition. Marine Scotland Shetland Shellfish Management Organisation (SSMO) (2014) SSMO Harvest Control Rules [restricted access] Science, 65 pp. Shetland Shellfish Management Organisation (SSMO) (2016). Regulations, Shetland Shellfish Management Organisation [ accessed: 8/01/2016]

5 Management Details less risk more risk Advised and agreed catches According to the Scottish government statistics 42 tonnes of lobsters were landed into Shetland in 2014 (Scottish Government, 2014). Stock harvesting strategy The management of lobster around Shetland up to the six nautical mile limit is the responsibility of the Shetland Shellfish Management Organisation due to a regulating order that allows them to manage shellfish within this area. Outside of this lobster are the responsibility of Marine Scotland and are under the same rules as the Inshore Fisheries Groups around Scotland. The SSMO objectives include managing and regulating shellfish fisheries within the six mile limit, using licence issuing, minimum landing size and other regulations to keep the fisheries sustainable in the long term (SSMO, 2016a). Management by the SSMO is seen as tighter than in other areas around Scotland as regulations include a total creel limit and the number of licences are limited, as well as a regulation on minimum landing size (90mm in Shetland and 87/88mm in the rest of Scotland). There is also scope within the harvest control rules of the SSMO to implement more measures such as spatial/temporal closures and an increase in MLS if catch rates indicate a need to do so. LPUE is used as a reference point in this case to indicate whether more management measures or stricter management measures need to be considered. Organised as a traffic light system, values of LPUE have been chosen to assist management decisions in the future, i.e. if green then no extra management measures, amber requires consideration of extra management measures and if reference points are red this may result in closure or/and a more detailed monitoring of the fishery(ssmo, 2014). The annual stock assessment is assessed through a combination of comprehensive landings and effort data collected through mandatory logsheets, as well as observer collected data. Results such as LPUE, effort and the Length Cohort Analysis (LCA) are considered in order to make informed management decisions. There are a number of regulations that vessels that have obtained a licence from the SSMO have to comply with. Some of these are similar to regulations for edible crab fishing in the rest of Scotland (SSMO, 2016b). Main SSMO regulations : Vessels over 17m are not allowed to fish with creels within the six mile limit Vessels are restricted to a total creel limit of 600 creels, 240 of these must have escape gaps fitted Minimum landing size for lobster is 90mm carapace length Landing of soft or v-notched lobsters is prohibited Fishermen are obliged to fill in logsheets to enable monitoring of the fishery Effort, LPUE and population (via LCA analysis) are monitored and if reference points are reached then additional management measures, such as no new licences issued or increasing minimum landing size, may be implemented (SSMO, 2014). Surveillance and enforcement Fishermen are obligated to submit logsheets detailing daily landings and effort by area. There is also occasional patrols that haul creels in order to check compliance. MSC (2012) MSC sustainable fisheries certification. The SSMO Shetland inshore brown & velvet crab, lobster and scallop fishery.public Certification Report. January pp. Scottish Government (2014) Scottish Sea Fisheries Statistics-Landings Tables [ Fisheries/PubFisheries/2014LandingsTables] [Date accessed: 8/01/2016] Shetland Shellfish Management Organisation (SSMO) (2014) SSMO Harvest Control Rules [restricted access] Shetland Shellfish Management Organisation (SSMO) (2016a) Aims and Objectives, Shetland Shellfish Management Organisation [ accessed: 8/01/2016] Shetland Shellfish Management Organisation (SSMO) (2016b) Regulations, Shetland Shellfish Management Organisation [ accessed: 8/01/2016]

6 Bycatch Details less risk more risk Targeting and behaviour In Shetland, the crab and lobster fishery uses static gear known as creels. These creels are similar to traps and pots found throughout the UK and Scotland, usually utilising a metal frame covered in small mesh netting, with mesh eyes that make entering easier than exiting for the crab. These creels are then baited typically with fish that is likely to be frozen mackerel or horse mackerel or waste from local fish processers. Creels are set in leaders that could comprise of between creels on a line but typically vessels tend to have approximately creels per leader as they are limited by the size of their boat. Gear is placed usually at specific depths or bottom types and locations that the fishermen know to be good spot for their target along the coastline of Shetland. Soak time or time that the creels are left on the seafloor before being hauled is generally a few days or less but fishermen have been known to leave leaders for weeks due to a variety of reasons (Tallack, 2002). Generally ghost fishing occurs very rarely and then only for limited duration. Inkwell pots and creels have been found to allow their content to escape after about 3 days. Escapes will eventually occur from parlour traps and soft-eyed traps by crabs gradually cutting their way through though it might not occur until after about 3 months (Swarbrick and Arkley, 2002). Another study by Bullimore et al., found that a leader of creels ghost fishing can fish for extended periods (i.e. over a year). Evidence of bycatch risk Mesh size allows juveniles and undersized individuals of the target species as well as smaller species of crab to escape in many instances. However, due to the nature of creel fishing any individuals soft, berried, undersized or not targeted are returned alive when creels are hauled and the catch sorted. Of the 600 creels permitted, only 240 of these are allowed to fish without escape gaps. These escape gaps are designed to allow all velvet swimming crab and undersized edible to escape the creels but are large enough to allow undersized lobster to escape as well (MSC, 2015). Occasionally bycatch of other species is also found in creels, fish species such as cod, poor cod and rockling as well as a variety of invertebrates. These are generally discarded alive if the fish are not used for bait (Tallack, 2002). Bycatch (not including discards of soft or berried retained/target species was estimated at around 1% in the MSC certification report of the Shetland creel fishery (MSC, 2012). Rare, threatened or iconic species are rarely caught in pot fisheries though leatherback turtles have very occasionally become entangled in pot ropes and occasionally whales have been found also entangled (Thomson, 2010; Pierpoint, 2000). There is also the potential for otters or birds to interact with creels. The configuration of leaders is thought to decrease significantly the chance of entanglement with such animals, in comparison to pot fisheries in North America for example (MSC, 2012). A study on the Relative Risk of Entanglement around Scotland was conducted using minke whale sightings and found Shetland had a much lower risk than elsewhere in Scotland (Northridge et al., 2010). Mitigation measures Bycatch of undersized lobsters and other crustacean caught in creels is regulated by a minimum landing size (MLS)*. Landing of other stages (soft or v-notched*) are also prohibited. Minimum landing sizes also apply to other commercial species taken with lobsters (e.g. velvet crab and edible crab) (MSC, 2012), lobsters tend to be found in conjunction with velvet crab rather than edible crab. *Please refer to management section for further specific information for this fishery. MSC (2012) MSC sustainable fisheries certification. The SSMO Shetland inshore brown & velvet crab, lobster and scallop fishery.public Certification Report. January pp. MSC (2015) MSC sustainable fisheries certification. The SSMO Shetland inshore brown & velvet crab, lobster and scallop fishery Surveillance Report 3 rd stage. September 2015, 41 pp. Northridge, S., Cargill, A., Coram, A., Mandleberg, L., Calderan, S. and Reid, B. (2010) Entanglement of minke whales in Scottish waters; an investigation into occurrence, causes and mitigation. By Sea Mammal Research Unit for Scottish Government. Pierpoint, C. (2000) Bycatch of marine turtles in UK and Irish waters. JNCC Report No pp. Swarbrick, J. and Arkley, K. (2002) The evaluation of ghost fishing preventers for shellfish traps. Seafish Report No SR pp. Tallack, S. (2002). The biology and exploitation of three species in the Shetland Islands, Scotland: Cancer pagurus, Necora puber and Carcinus maenas. PhD Thesis. NAFC/UHI.

7 Habitat Details less risk more risk Gear effects, targeting and behaviour Creels are set in leaders that are typically comprised of of the creels. Leaders are then shot over the desired location and settle on the bottom. The seafloor tends to be substrate suited to the particular target species, relatively shallow and usually fairly hard or gravelly bottoms that are often subjected to a degree of disturbance from adverse weather conditions. Habitat risks Static gear such as creels are known to have notably less impact on benthic habitats than other fishing gear such as bottom trawl or dredge (Bernette, 2001; Polet & Depestele, 2010). There have been a few studies on the impact of pots and traps on the benthos around the UK. A four year study on the No-take zone around Lundy Island off the south west coast of England indicated that there was no difference over the time period between areas fished with pots and those left untouched (Coleman et al., 2013). A review of evidence and data gaps indicated that whilst there are still many unknowns, many of the habitats around Shetland (i.e. rocky substrate, kelp forest etc.) are not known to be sensitive to potting but some locations such as those with horse mussel beds or sea grass may be more sensitive to intense potting activity (ABPmer, 2015). Ghost fishing is known to occur in pot and trap fisheries when gear is lost (Swarbrick et al., 2002). It is thought that the effects are generally negligible but that these pots can continue to fish for extended periods of time (Bullimore et al., 2001). Mitigation measures The data that is collected thorugh logsheets for the SSMO enables managers to have a good understanding of the effort distribution around Shetland. There is also ongoing work on mapping sensitive habitats around the coastline (MSC, 2012) ABPmer (2015) Summary of Evidence Sources on Impacts of Potting on Designated Features. Workshop 25th February ABPmer. P1-9. Bernette, M. C. (2001). A review of the fishing gear utilized within the Southeast Region and their potential impacts on essential fish habitat. National Marine Fisheries Service. Bullimore, B. A., Newman, P. B., Kaiser, M. J., Gilbert, S. E., & Lock, K. M. (2001). A study of catches in a fleet of ghost-fishing pots. Fishery Bulletin, 99(2), Coleman, R. A., Hoskin, M. G., Von Carlshausen, E., & Davis, C. M. (2013). Using a no-take zone to assess the impacts of fishing: Sessile epifauna appear insensitive to environmental disturbances from commercial potting. Journal of Experimental Marine Biology and Ecology, 440, MSC (2012) MSC sustainable fisheries certification. The SSMO Shetland inshore brown & velvet crab, lobster and scallop fishery.public Certification Report. January pp. Polet, H., & Depestele, J. (2010). Impact assessment of the effects of a selected range of fishing gears in the North Sea (p. 120). ILVO. Swarbrick, J. and Arkley, K. (2002) The evaluation of ghost fishing preventers for shellfish traps. Seafish Report No SR pp. All content 2018 Seafish. Origin Way, Europarc, Grimsby, DN37 9TZ. This page created on 10th July 2018 at 10:31am.