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Biopsy sampling Attempts were made to biopsy sample three sharks using the biopsy pole and two sharks with the crossbow One sample was obtained from the third shark sampled using the biopsy pole however this resulted in the pole breaking and no more attempts could be made. No samples were obtained from biopsy sampling using the crossbow despite one shark being hit from 5m. The arrow bounced of the shark but no skin sample was obtained. The barbs in the biopsy tip were bent from the impact with the sharks’ tough skin.
Table 5. List of stranded basking sharks in Ireland and tissue samples obtained for genetic analysis during 2009.
Three samples from archived tissues and five samples from the present study were sent to Dr Chrysoula Gubili at the University of Aberdeen together with a sample of slime from one shark, which was scrapped off the bow of the research vessel after being hit by the tail after tagging. It had been suggested (Noble et al. 2006) that DNA may be extracted from basking shark slime which occurs on the sharks’ skin which could aid the collection on samples for genetics. Dr Gubili managed to extract DNA from the slime recovered from the side of the research vessel and to amplify it. A PCR was run to ensure the DNA came from a basking shark. This demonstrated the value of shark slime for genetic work.
A further five samples were obtained from basking sharks in the Blasket Islands on 8 August using a modified mop handle and scourer pad. This technique was also used successfully in the Isle of Man and a paper is being prepared on this technique as it offers a non-invasive efficient method of obtaining samples for genetic analysis.
Shark entangled in gillnet in Derrynane, Co Kerry and washed up in Falcarragh, Co Donegal Publicity Following the remarkable tagging success in Co Donegal at the beginning of June a number of media items were published. A good article in the Irish Times on 5 June led to a number of articles in the tabloid newspapers and interest from UK newspapers. Radio interviews were recorded for RTE 1, BBC NI, Newstalk and many local radio stations. This has led to increases awareness and interest in Basking Sharks in Ireland and the study.
Following this initial interest continued requests for comment and input was received from a number of newspapers including Observer and Guardian newspapers in the UK. A French film crew with Cannel Plus also made contact with the team, wishing to film sharks off Co Donegal. Due to time constraints, this crew has decided to return next year during the peak basking shark season to film.
The project facilitated film crew from Crossing-the-Line films on five days; 3 days in Co Donegal and one day each in Counties Cork and Kerry. The deployment of the satellite tags off Slea Head, Co Kerry was filmed as well as the deployment of coloured numbered tags off Co Donegal and biopsy sampling and photo-identification.
A website www.baskingshark.ie has been established to promote the forthcoming Irish basking shark Seminar, it also provides primary information on basking sharks in Ireland and provides a media for people to report any sightings of tagged sharks.
The project team presented a paper on the work in Ireland to date at a conference in the Isle of Man from 2August 2009 entitled Basking Sharks – A Global Perspective and will present the results from this year’s survey which we feel will ensure Ireland remains a significant player in future basking shark research in Europe (See Appendix III for abstract).
Additional data collected In addition to the primary aims of this study additional information was obtained on the diet of basking sharks and surfacing behavior. Sightings of other species including cetaceans, sunfish and a probable turtle (Table 6).
Table 6. List of additional sightings of marine megafauna recorded during 2009.
A total of 17 cetacean sightings, two Sunfish (Mola mola), two Porbeagle sharks and one probable turtle sightings were made during this survey. The sighting of around 30 bottlenose dolphins off Brandon, Co Kerry was of significance as they were identified as Shannon dolphins. Over 20 individual dolphins were identified from images and 13 of these had previously been recorded in the Shannon Estuary from comparison to the Shannon Dolphin Photo-ID catalogue held by the Shannon Dolphin and Wildlife Foundation. Shannon dolphins have never been recorded this far west, outside of the Shannon estuary (Ryan and Berrow, submitted). All cetacean sightings have been submitted to the Irish Whale and Dolphin Group.
The turtle was observed on three occasions off Cape Clear Island, Co Cork on 11 June but no images could be obtained. It was thought to be a Cheloniid turtle, probably a Loggerhead (Caretta caretta) and the data, including sunfish records, have been sent to Dr Tom Doyle of CMRC in Cork.
Discussion The Basking Shark Survey 2009 has been very successful. A total of 101 coloured tags were deployed in three counties and two satellite tags off Co Kerry. Images of 71 individual sharks were obtained for photoidentification and ten tissue samples obtained for genetic analysis, five from the sharks slime – a new technique developed by this project.
The project team gained huge experience of basking sharks, tested and developed new techniques and enjoyed considerable media interest. There is no doubt that we have established a very important basking shark research project and a lot of people in Ireland are now aware and interested in basking sharks in Ireland.
1. Despite a large number of basking shark sightings in June 2009 it was still very difficult to be at the right location at the right time to encounter and tag sharks. Often sharks are at the surface for only a very limited period and conditions can change very dramatically within and between days.
Even when weather conditions are similar between days the distribution and surfacing behaviour of sharks may be radically different constraining tagging attempts. An alternative strategy would be to remain in an area for extended periods rather than move to new locations as shark sightings are received.
2. For efficient location of sharks it is recommended that as well as the boat-based team an additional team member is stationed on land at a suitable vantage point, if available, to locate sharks and direct the research vessel to them. This worked very effectively in West Kerry when the project team were looking to deploy satellite tags on sharks.
3. Areas with concentrations of shark can be surveyed by vessel before and after tagging sessions to pre- determine surfacing patterns and potentially increase encounter rates.
4. More tags need to be deployed as the recovery rate is unknown. In many ringing/tagging studies the recovery rate can be les than 1% and the longevity of basking shark tags on sharks is not known. We recommend this tagging is continued for three years before a thorough evaluation of its effectiveness is carried out.
5. More satellite tags should be deployed to provide a baseline for the future. Deployment of FastLoc GPS tags should also be considered as these will provide finer scale tracks which can be used to identify important areas for basking sharks in Ireland.
6. Photo-identification of individual sharks is generally of limited value. Sharks with minor nicks or markings can be useful over a tagging session to identify sharks previously tagged but probably not useful over extended periods. Sharks with significant damage are rare but provide excellent opportunities for re-sightings through photo-identification.
7. If biopsy sampling is to be continued the biopsy tip will need to be modified to increase the chances of the tip obtaining a skin sample as shark skin is very tough. The biopsy pole probably offers the best option but the pole and tip will have to be much stronger to withstand the impact required to obtain a sample.
8. Slime from the sharks’ body can be used to extract DNA. A method of obtaining a sample of this slime has been developed as a non-invasive system of obtaining samples for genetics and is considered a significant break through in the study of basking sharks
9. Such is the interest in basking sharks in Ireland we recommend a Basking Shark Study Group is created under the auspices of the Irish Elasmobranch Group to promote the research and awareness of basking sharks in Ireland. This recommendation will be persued through the Irish Basking Shark Seminar from 30-31 October 2009 to be held in the Fisheries College in Greencastle, Co Donegal.
AcknowledgementsWe would like to thank Stephen McGavigan, Lee Magee, Paul McNutt, Lough Swilly Marina, Danny Portious, Darren Stephens, Pat Curran, Rosemary Hill, Lucy Hunt, Pádraig Whooley, Vivi Bolin and especially Conor Ryan and Nick Massett for help in the field and Brian O’Rourke, Nick Massett, Joe Joyce, Ross Bartley and Colin Speedie for sending in re-sightings.
Berrow, S.D. (1994) Incidental capture of elasmobranchs in the bottom-set gill-net fishery off the south coast of Ireland. Journal of the Marine Biological Association of the U.K. 74: 837-847.
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Doyle, J.I., Solandt, J.-L., Fanshawe, S., Richardson, P., Duncan, C. (2005) Marine Conservation Society Basking Shark Watch Report 1987-2004. Marine Conservation Society: Ross-on-Wye, UK.
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Hoelzel, A. R., Shivji, M. S., Magnussen, J., and Francis, M. P. (2006). Low worldwide genetic diversity in the basking shark (Cetorhinus maximus). Biological Letters 2, 639–642.
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Proceedings of the Royal Irish Academy C 65: 91-115 Appendix I: Log of tagged basking sharks 2009.
Appendix II: Paper presented at the Basking Sharks – A Global Perspective conference on the Isle of Man from 2-5 August 2009 Basking Sharks in Ireland: historical perspective and future research
Keywords: Ireland, Historic, Sightings, Tagging, Future Research The basking shark was a very familiar visitor to coastal communities in Ireland. It was known as ainmhide na seolta ‘monster with the sails’ and liop an dá ‘unweildy beast with two fins’. More generally in the west of Ireland it was called liabhán mór (signifying a great leviathan) or the most evocative liabhán chor gréine ‘great fish of the sun’. It was locally known as the “sunfish”.
The best documented basking shark fishery was off Achill Island, Co Mayo. Between 1950 and 1964, 9,000 sharks were killed with a record 1,808 killed in 1952 alone. From 1955 the catch declined and the fishery closed in 1975 after 12,342 sharks had been killed. It has been suggested that the collapse of this fishery indicated a local stock had been over-fished but there is also evidence of changes in zoo-plankton distribution. Basking sharks were continued to be fished commercially by Norwegian vessels off Co Waterford up to 1986 when 2,465 sharks were killed. By-catch of sharks in static gillnets is still a cause of mortality in Ireland.
Sightings of basking sharks on the surface have been systematically collected in the UK and Ireland by the UK Marine Conservation Society since 1987. Of the 4,005 sighting records reported by 2002 only 71 were from the Republic of Ireland and 33 from Northern Ireland. In 1993 a sighting survey was carried out in Ireland and 140 sightings of 425 individual sharks were received with concentrations off the east, southwest and northern coasts. The Irish Whale and Dolphin Group (IWDG) have collected 442 basking shark records since 1992. There has been a rapid increase in sightings reported to the IWDG since 2004 which cannot be explained entirely by increased effort or reporting.
This increase in sighting records has resulted in an increase in research interest. In 2008 basking sharks were successfully tagged off Counties Kerry and Donegal with uniquely numbered, coloured tags. This pilot study provided knowledge and experience of basking shark tagging and was expand significantly in 2009 when 71 tags were deployed in addition to two PAT archival tags. A photo-identification catalogue was established in 2009 with images of 60 sharks to date and three more tissue samples added to a tissue archive. In this paper we review present knowledge of basking sharks in Ireland and look at present and future research activities and opportunities.