Non-Lethal Seal Deterrent in the North East Scotland Handline Mackerel Fishery. A Trial using Targeted Acoustic Startle Technology (TAST) David Whyte, Thomas Götz, Sam F. Walmsley and Vincent M. Janik 1 Contents Project Team ............................................................................................................................................... 3 Funding ........................................................................................................................................................ 3 Executive Summary ..................................................................................................................................... 3 Introduction ................................................................................................................................................. 4 Fishing methods .......................................................................................................................................... 6 Trial Methodology ....................................................................................................................................... 7 Data analysis .............................................................................................................................................. 13 Results ....................................................................................................................................................... 15 Discussion .................................................................................................................................................. 19 Conclusions ................................................................................................................................................ 22 Acknowledgements ................................................................................................................................... 23 References ................................................................................................................................................. 23 Appendix 1 – RHIFA Seal Conflict with under 10m summer Handline Mackerel Fishery Report. ............ 24 Appendix 2 – Data Sheets completed by fishers ....................................................................................... 32 Appendix 3. – Model details and full results ............................................................................................. 33 Appendix 4. – Supplementary figures ....................................................................................................... 39 2 Project Team David Whyte, Rosehearty Harbour and Inshore Fisherman’s Association (RHIFA) Dr Thomas Götz, University of St Andrews Professor Vincent Janik, University of St Andrews Lynda Blackadder, Marine Scotland Science (MSS) Anne McLay, Marine Scotland Science (MSS) Sam Walmsley, University of St Andrews Chloe Aird, Marine Scotland (MS) Jennifer Mouat, North East Coast Regional Inshore Fishery Group (NECRIFG) Steven Alevy (Genuswave) Funding This trial was funded by the North East Coast Regional Inshore Fishery Group (NECRIFG), Genuswave and Rosehearty Harbour and Inshore Fisherman’s Association (RHIFA). Executive Summary Local Rosehearty fishers have observed a steady increase in seal numbers around the north east coast of Scotland in recent years with seals causing significant disruption to the inshore handline fishery for mackerel. Seals often follow boats as they leave the harbour to search for fish and when fish are located, seals interfere with fishing operations by dispersing the shoals. Fishers are keen to reduce these negative interactions with seals. A trial using Targeted Acoustic Startle Technology (TAST) to deter seals in the vicinity of fishing vessels was carried out between late July and early October 2020 on the inshore mackerel grounds in the North East Coast Regional Inshore Fishery Group (NECRIFG) area. The trial involved five fishing vessels operating from Rosehearty Harbour. Fishers were asked to return a data sheet for each day fished, recording data on seal sightings, fishing operations and catches on days when they were either fishing normally (control) or additionally deploying the TAST device. Data analysis revealed a strong deterrence effect of TAST on seal activity directly around fishing vessels, in which seal detections on the vessels’ fish finder (sonar) decreased by 97%. Only one seal was observed under a vessel when TAST was deployed. No significant effect was evident in the visual sighting data, though fewer seals were spotted when TAST was operatiponal. This could be the result of a limited deterrence range of the device and/or a change of seal dive submersion times. Beyond the influence of TAST, visual detections of seals decreased towards the end of the season. Fishing metrics such as ‘fishing stop duration’ and ‘catch weights’ were primarily influenced by time-of-year (seasonality). However, fishing stop duration was almost twice as long when TAST was used which may be the result of a reduction in shoal dispersal caused by seals. More data are required to investigate whether TAST also leads to an increase in catch weight. Generally, statistical findings are consistent with reports from fishers, supporting the idea that TAST is effective in its primary function of deterring seals and preventing shoal dispersal caused by seals swimming under or close to the vessel. The study suffered from an imbalance between control and TAST days and a decline in seal/vessel interactions towards the end of the fishing season. It would be helpful to collect more data during the presumed peak predation season in June and July. It would also be beneficial to 3 investigate seal/fish shoal interactions at the behavioural level using sonar from a secondary vessel to optimise TAST use and provide fishers with improved fishing practice guidelines. Introduction Studies have reported a continuous increase in seal numbers around the east coast of the UK sine 1985 with a four-fold increase in grey seal pup production over 20 years (Thomas et al. 2019). Fishers have also reported an increase in seal numbers around the north east coast of Scotland (and elsewhere in the UK) since the introduction of seal protection measures, initially through the Conservation of Seals act 1970 and more recently the Marine (Scotland) Act 2010 - Part 6 'Conservation of seals'. Interaction between seals and fisheries is an increasingly common occurrence and has been well documented in recent years (MMO 2020, Tixier et al. 2021). For a number of years, local fishers in Rosehearty and other east coast harbours, such as Fraserburgh, Whitehills and Eyemouth, have reported problems with seals interfering with the inshore handline mackerel fishery. Hindrance has been increasing year on year, causing frustration to the industry and the locals who rely on this fishery for their income. The main issue is the detrimental effect the seals have on fishing operations by scaring and dispersing the shoals of fish. Seals will remove fish from the handlines, however the quantity of fish lost in this way is negligible compared to the loss of catch due to diminished fishing time on mackerel shoals. In many cases, although fish are present in the area, seal interference makes it extremely difficult for fishers to catch their allocated quota. The handline mackerel fishing season is contingent on the arrival of shoals in the area and typically starts sometime between May and June, continuing into October. The fishery provides a significant source of income for many inshore fishers around the east coast of Scotland, particularly in the Rosehearty area, and is also a diversification opportunity which reduces the effort targeted towards fishing crab and lobster stocks. The extent of seal interference varies throughout the season and is typically at its highest during June to September. Fishers report that seal interference appears to decrease during September. Grey seals (Halichoerus grypus) appear to constitute the majority of seals in the area (Russell et al 2017). Juvenile and adult seals are occasionally observed following the fishing boats and it is possible that juveniles learn to participate in this ‘easy meal’ approach from experienced adults. A proposal document “Seal conflict with under 10 m summer Handline Mackerel Fishery” (Appendix 1) was tabled to representatives of NECRIFG, Marine Scotland Science, the Sea Mammal Research Unit at the University of St Andrews and other interested parties on the 25th February 2020. The report detailed the detrimental effects of the increase in predatory seals, over at least 16 years. Seal conflict during the mackerel fishery generates the following issues for skippers; Frequent returns to port with insufficient quantity of fish to land Inability to catch allocated quota More time at sea Increased fuel consumption Loss of earnings Injury to seals by entanglement in fishing lines. 4 The proposal document was written from the perspective of the fishers. It provides background information on the mackerel handline fishery, the fishing methods used and the seasonal nature of the fishery by under 10 m vessels operating from a small harbour. The constraints associated with boat size, the limited fishing opportunities within the fisher's safe area of operation, and the seasonal nature of the fisheries are also explained. Additionally, an outline of the legal framework associated with the protection of seals