Species & Habitat Restoration
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Correlation Between Reef Terrain Variables and Species Diversity in Spiny Lobster HabitatCrayfish or spiny lobster occur in physically complex reef habitat in shallow waters off the west coast of Ireland. These habitats provide shelter for larvae that are settling out from the overlying water column and for juvenile and adult lobsters that use these areas to shelter and forage. Fisheries for spiny lobster occur in these areas and remove lobsters from the reef. The consequence of this for the structure and function of reef habitat is unknown. In this study the distribution of reef habitat was estimated from multibeam acoustic data collected in previous campaigns by the INFOMAR programme. Sub-sets of this area were re-mapped at higher resolution to provide further detail of the topography of the reef from which terrain variables were derived. Underwater video and SCUBA methods were used to identify the flora and fauna in areas with different topographies. Weak correlations between the terrain variables and the biological data were found. This was used to model the distribution of areas of high and low biodiversity over broader areas where only terrain data were available. Capacity to model the distribution of biological communities and crayfish over broad areas using physical terrain data remains difficult. Other physical variables that may be important in regulating the biology of reef need to be included and the association of crayfish with particular types of reef terrain needs to be established by higher resolution sampling. The benefits of the work reported here include increased capacity to monitor the distribution of biodiversity in marine reef habitats, to detect change that may be brought about by sector activities such as fishing or climate change, to estimate the population size of exploited reef species for fisheries management and to identify positive changes to biodiversity and lobster abundance that may occur through spatial management of reef habitat.
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Catch and bycatch in the tangle net fishery for crayfish (Palinurus elephas) off the south west coast of IrelandCrayfish or spiny lobster is fished off the south west coast of Ireland. There are also smaller fisheries on the west and north west coasts. Although historically, prior to the 1970s, the main fishing gear used in the fishery was top entrance traps crayfish are now targeted with large mesh tangle nets. The selectivity of these nets is poor and there is known to be a by-catch of finfish, skates and rays and protected species such as grey seal. The fishery usually occurs from mid-March to December. The species composition and size distribution of the catch and by-catch was surveyed over a 4 year period from 2017-2020 from Dingle Bay north to the Shannon Estuary. Additional data south of this area was obtained in 2020. A crayfish tagging programme was undertaken in 2017 and 2018. Between 2 and 6 vessels participated in the programme depending on year Most of the data was reported directly by Skippers and crew who were contracted to supply data. Scientific observers covered a proportion of trips in 2017 and 2019. A total of 1500 nmiles of tangle net hauls were surveyed across 6 vessels. A total of 11792 crayfish and 899 lobsters were measured, 1234 crayfish were tagged and released and 45 recaptures were reported. Spider crab, brown crab and crayfish were the numerically dominant species in the catch. Lobster, pollack, thornback ray, spurdog, monkfish and turbot were caught regularly in low numbers. There was no cetacean by-catch. A total of 200 grey seals were caught over the 4 year period by the vessels participating in the survey. Endangered and critically endangered species, including flapper skate, common skate, angel shark and white skate, were caught in very low numbers. The finfish catch is mainly lost to scavengers or seal depredation before nets are retrieved and because of long soak times which averaged 8 days. This reduces the value of the catch. The average value of the live crustacean (crayfish, lobster, brown crab) catch was approximately €300 per mile of net hauled. Crayfish were tagged and released in 2017 and 2018 and recaptured during the period 2017-2020. Three crayfish tagged by IFREMER off Brittany in 2015 and 2016 were recaptured off the south west and west coast of Ireland in 2019. The northern most recapture was off Erris Head Co. Mayo. The tagging data shows that most crayfish were recaptured locally close to release points even in the years following tagging. It is still unclear if crayfish are resident or if they migrate in and out of the tagging area as the reporting rate of recaptures outside the tagging area is unknown. The by-catch of critically endangered species poses a high risk to the continued presence of these species in Irish waters and indeed in European waters given that the area is known to hold the last European remnant populations of species such as angel shark and white skate. Grey seal by-catch was related to the distance between the fishing event and the nearest seal colony haul out at the Blasket Islands. Sixty % of seals were caught within 10km of the haul out. The probability of capture in a single net haul declined from 30-35% within 10km to 9-14% at distances of 10-30km to 4% at distances of 40-60km and zero at distances greater than 60km (data for 39 hauls >60km). The high by-catch of grey seal is a significant risk to the Blasket Island seal colony. It is unlikelythat the Blasket population can sustain this level of by-catch mortality without inward migration fromother colonies.
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Monitoring the recovery of exploited deep-water speciesCommercial fisheries for deep-water species off the Irish coast developed in the late 1990s and declined in the early 2000s. Many of the exploited stocks were depleted a result of commercial exploitation and ICES has advised a zero catch for Orange Roughy since 2004, and for Portuguese Dogfish and Leafscale Gulper shark since 2005. Since 2016, the deep water access regulation has effectively banned trawling in waters deeper than 800 m (EC, 2016) and fishing for deep-water sharks with static netting >600 m is also banned by the technical measures regulation (EC, 2019). However, some of these species continue to be caught, either by gears not covered by this regulation or in water <800 m deep. The Marine Institute carried out a survey programme to assess the distribution and abundance of these species between 1992 and 1999 and again between 2006 and 2009. Since 2019, 3 days of the Irish Anglerfish and Megrim Survey have been allocated to monitoring the recovery of commercial deep-water species. This work was funded under the European Maritime and Fisheries Fund (EMFF) from 2019 to 2021 and European Maritime, Fisheries and Aquaculture Fund (EMFAF) since 2022. The main objective of the current project is to assess the recovery of exploited deep-water species in Irish waters by comparing the results from 2019 to 2022 surveys with those from the previous period in 2006 to 2009 (methods used in the earlier period 1992 to 1999 were different, therefore a direct comparison with that period is not possible).
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Supply of Vertebrate Necropsy and Sample Recovery Services Merged Final ReportsThe Marine Institute issued a tender for the Supply of Vertebrate Necropsy and Sample Recovery Services Tender (2017-2018). The results are presented in this report. These tenders required i) the recovery and standardised necropsy of three cetacean species with associated case history reporting, ii) the provision of sampling kits to be used for the recovery of tissue samples collected from bycaught animals (birds, seals and cetaceans) by observers on commercial inshore and offshore fishing vessels in Irish waters in order to provide additional data to the MI’s existing catch sampling programme and iii) the storage and subsequent delivery of all samples and associated databases to the client. Recovery of 24 animals from two geographical lots was the target for the initial contract (2017) and was achieved. The contract extension (early 2018) required the collection and necropsy of a further 16 animals, which was exceeded as 19 animals were collected. A target of 30 animals to be recovered was required in the second contract (2018) and was also successfully reached. These 73 animals comprised 53 common dolphins (Delphinus delphis), ten striped dolphins (Stenella coeruleoalba) and ten harbour porpoises (Phocoena phocoena). Forty-one of the 73 (56%) individuals were recovered from Lot 1 from counties Clare to Donegal, while 32 (44%) individuals were recovered from Lot 2 from counties Wexford to Kerry. Thirty-five sampling kits were assembled and delivered to the Marine Institute, and additional kits were prepared and available upon request for distribution to their panel of fishery observers. Between 24 July and 14 December 2017, two adult male grey seals were incidentally captured in tangle nets and reported to the Project Coordinator. Results from these tenders will inform the development of a long-term strategy for necropsy of stranded cetaceans and recovery of tissue samples for further biological studies. Samples requiring long-term storage at -20°C, including those for virology, were transported in a portable refrigerator to the IWDG office in Kilrush, Co. Clare and stored at facilities on site. Formalin fixed tissues, such as reproductive organs and adrenal glands, were stored at the RVL in Cork. All samples have been delivered to the Marine Institute in Oranmore, Co. Galway along with a detailed database of samples collected.
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The Distribution and Abundance of Elasmobranch Fish in Tralee, Brandon and Dingle Bays in 2018-2019Surveys of skates and rays were undertaken in Tralee, Brandon and Dingle Bays in north Kerry during 2018 and 2019. The area was previously shown, from angling records and more recent shore surveys of egg cases, to support a high diversity of these species some of which are critically endangered in Ireland, the Atlantic or globally. Twelve species were recorded in the area and their geographic and seasonal distribution is described in this report. Their relative abundance in the surveys confirms their presence in the Tralee Bay area and the importance of that area as a refuge for them. Three of the species recorded, angel shark, blue skate and flapper skate are critically endangered globally. White skate was not recorded in the surveys but a single individual was captured separately in commercial tangle nets in 2018 in the area. This species is critically endangered in the Atlantic. Data from other broad scale fisheries surveys and fisheries sampling at sea, not reported here, confirm that these species are rarely found elsewhere. In addition, and in order of abundance, thornback ray, painted ray, sting ray, undulate ray, blonde ray, spotted ray, spurdog, tope and greater spotted dogfish were recorded. Endangered species of skates and rays are listed on various species red lists internationally and are prohibited species (from being landed) under Common Fisheries Policy regulations. The main source of mortality is from fishing. The current regulations, however, do not necessarily remove this source of impact because accidental by-catch and mortality can still occur. Populations that are at critically low levels locally are unlikely to be able to sustain this additional mortality and there is an ongoing risk of local extinction. Effective protection and restoration will need to consider additional measures such as marine protected areas or other mitigations of the effects of fisheries where they pose a high risk to the viability of local populations. Waters off north Kerry are important internationally as they hold some of the last remaining refuges for angel shark and white skate.