Description
Blue Shark Description
The Blue shark is a long and slender shark, dark blue dorsally, bright blue on the sides and white on the belly. They can reach over three meters long and feed largely on fish and other animals in the pelagic zone such as squid, smaller sharks and even sea birds.
Typically they occur in large aggregations which are often size and sex segregated.
Blue sharks are viviparous, with females producing average litters of 35 live pups.
Distribution
Blue Shark Distribution
The Blue shark is a long-distance migrant. It is present in Irish waters usually from June to October when it is taken by recreational anglers on rod and line on a catch-and-release basis.
The Blue shark has been described as one of Ireland’s largest and most valuable marine sport fishes (Fitzmaurice and Green 2000).
Due to high catch rates by commercial fisheries and high demand for blue shark as a food source, this species has been assigned a status of ‘Near Threatened’ in Irish waters by the IUCN (Clarke et al. 2016).
Tagging results
Blue Shark tagging
Distribution of tagged blue shark 1970-2013
Between 1970 and 2013 19,309 Blue sharks were tagged as part of the Marine Sportsfish Tagging (MSFT) Programme all along the south, west and north Irish coast. (Wogerbauer et al. 2016). These account for 45% of all tagging events since the beginning of the programme.
Number of blue shark caught per boat per day spent shark-fishing
The majority of blue sharks tagged off the Irish coast to date were smaller females (220cm fork length or less). Tagging of blue shark peaked in the 1990’s.
Blue Shark recaptures
895 recaptures have been reported from all across the North Atlantic and the coast of Africa. In 2002, a blue shark tagged as part of IFI’s programme was recaptured an estimated 6,840 km from its tagging location off the coast of Accra, Ghana only 247 days after its release.
One blue shark was recaptured in 2008 after 4,326 days (11 years) and another individual was recaptured in 2009 after 6,502 days (17 years) at liberty. Both sharks had returned to the west coast of Europe, an estimated 560 km and 450 km from their original tagging locations respectively.
References
References
Clarke, M., Farrell, E.D., Roche, W., Murray, T.E., Foster, S. and Marnell, F. (2016) Ireland Red List No. 11: Cartilaginous fish [sharks, skates, rays and chimaeras]. National Parks and Wildlife Service, Department of Arts, Heritage, Regional, Rural and Gaeltacht Affairs. Dublin, Ireland
Compagno L.J.V., 1984. FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2 - Carcharhiniformes. FAO Fish. Synop. 125(4/2):251-655. Rome: FAO.
Fitzmaurice P. and Green P. 2000. Results from tagging of blue shark in Irish waters. Irish Scientist Yearbook, 3: 51.
Stevens, J. 2009. Prionace glauca. The IUCN Red List of Threatened Species 2009: e.T39381A10222811. http://dx.doi.org/10.2305/IUCN.UK.2009-2.RLTS.T39381A10222811.en. Downloaded on 20 February 2017.
Wogerbauer C., O’Reilly S., Doody C. and Roche W. 2016. Recent data (2007-2013) from the Irish Blue Shark Recreational Fishery. Collect. Vol. Sci. Pap. ICCAT, 72(5): 1150-1166. [HYPERLINK TO TEXT ONLINE]
