The potential use of caudal thorns as a non-invasive ageing structure in the thorny skate (Amblyraja radiata Donovan, 1808)

  • Michael J. Gallagher
  • Marianne J. Green
  • Conor P. Nolan
Part of the Developments in Environmental Biology of Fishes book series (DEBF, volume 25)


The thorny skate, Amblyraja radiata, is the most widely distributed and abundant of all skate species worldwide, found on both sides of the north Atlantic Ocean. Large inter-regional size differences exist for this species and the few age and growth studies undertaken have revealed marked differences in life history traits for geographically distinct stocks. To facilitate the progression of further age and growth studies for this commercially important species, the effectiveness of caudal thorns as a rapid ageing tool was assessed. Twenty-eight male and 24 female thorny skates were collected off Greenland, covering the full size range of the species. Replicate age readings of crystal violet stained vertebral sagittal sections and whole silver nitrate stained caudal thorns revealed mean intra-reader age reading precision was higher for caudal thorns (Covariance (CV): reader 1 = 9.07, reader 2 = 9.73) than vertebrae (CV: reader 1 = 14.91, reader 2 = 14.27). Age bias plots revealed minimal inter-structure bias, apart from a higher average thorn age reading of 0.76 years from age classes 5–11 years for reader 1. Minor inter-reader bias was evident for vertebrae only; averaging 0.90 years higher for reader 1 from age classes 11 to 15 years. Preliminary evidence suggests caudal thorns could prove an effective non-invasive ageing tool for thorny skates.


Skate Age Caudal thorns Vertebrae Bias 


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  1. Anderson ED (1990) Fishery models as applied to elasmobranch fisheries. In: Pratt HL, Gruber SH, Taniuchi T (eds) Elasmobranchs as living resources: advances in the biology, ecology, systematics and the status of the fishery. NOAA Technical Report NMFS 90, pp 473–484Google Scholar
  2. Beamish RJ, McFarlane GA (1987) Current trends in age determination methodology. In: Summerfelt RC, Hall GE (eds) Age and growth in fish. Iowa State University Press, Ames, USA pp 15–42Google Scholar
  3. Berestovskii EG (1994) Reproductive biology of skates of the family Rajidae in the seas of the far north. J Ichthyol 34:26–37Google Scholar
  4. Bigelow HB, Schroeder WC (1954) Fishes of the western north Atlantic, part II. Sawfishes, guitarfishes, skates, rays, chimaeroids. Sears Foundation, Bingham Oceanographic Laboratory, New Haven, 588 ppGoogle Scholar
  5. Cailliet GM (1990) Elasmobranch age determination and verification: an updated review. In: Pratt HL, Gruber SH, Taniuchi T (eds) Elasmobranchs as living resources: advances in the biology, ecology, systematics and the status of the fisheries. NOAA Technical Report NMFS 70, pp 157–165Google Scholar
  6. Cailliet GM, Goldman KJ (2004) Age determination and validation in Chondrichthyan fishes. In: Carrier J, Musick JA, Heithaus MR (eds) Biology of sharks and their relatives. CRC Press LLC, Boca Raton, Florida pp 339–447Google Scholar
  7. Cailliet GM, Yudin KG, Tanaka S, Taniuchi T (1990) Growth characteristics of two populations of Mustelus manazo from Japan based upon cross-readings of vertebral bands. In: Pratt HL, Gruber SH, Taniuchi T (eds) Elasmobranchs as living resources: advances in the biology, ecology, systematics, and the status of the fisheries. NOAA Technical Report NMFS 90, pp 167–176Google Scholar
  8. Campana SE (2001) Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods. J Fish Biol 59:197–242CrossRefGoogle Scholar
  9. Campana SE, Annand MC, McMillan JI (1995) Graphical and statistical methods for determining the consistency of age determinations. Trans Am Fish Soc 124:131–138CrossRefGoogle Scholar
  10. Casselman JM (1983) Age and growth assessment of fish from their calcified tissue-techniques and tools. In: Prince ED, Pulos LM (eds) Proceedings of the international workshop on age determination of oceanic pelagic fishes: tunas, billfishes and sharks. NOAA Technical Report NMFS 8, pp 157–166Google Scholar
  11. Chang WYB (1982) A statistical method for evaluating the reproducibility of age determination. Can J Fish Aquat Sci 39:1208–1210CrossRefGoogle Scholar
  12. Compagno LJV, Ebert DA, Smale MJ (1989) Guide to sharks and rays of southern Africa. New Holland Publishers, London, 158 ppGoogle Scholar
  13. Del Río JL (2002) Some aspects of the thorny skate, Amblyraja radiata, reproductive biology in NAFO Division 3N. NAFO SCR Document 02/118, serial no. N4739, 14ppGoogle Scholar
  14. Dolgov AV (2004) Feeding and food consumption by the Barents sea skates. J Northw Atl Fish Sci 35: Scholar
  15. Francis MP, O’Maolagain C, Stevens D (2001) Age, growth, and sexual maturity of two New Zealand endemic skates, Dipturus nasutus and D. innominatus. N Z J Mar Freshwater Res 35:831–842CrossRefGoogle Scholar
  16. Francis MP, O’Maolagain C (2005) Age and growth of the Antartic skate, Amblyraja georgiana, in the Ross Sea. CCAMLR Sci 12:183–194Google Scholar
  17. Frisk MG, Miller TJ, Fogarty MJ (2001) Estimation and analysis of biological parameters in elasmobranch fishes: a comparative life history study. Can J Fish Aquat Sci 58:969–981CrossRefGoogle Scholar
  18. Gallagher MJ, Nolan CP (1999) A novel method for the estimation of age and growth in rajids using caudal thorns. Can J Fish Aquat Sci 56:1590–1599CrossRefGoogle Scholar
  19. Gallagher MJ (2000) The fisheries biology of commercial ray species from two geographically distinct regions. Ph.D. Thesis, Department of Zoology, University of Dublin, Trinity College, Dublin 2, IrelandGoogle Scholar
  20. Gallagher MJ, Nolan CP, Jeal F (2005a) Age, growth and maturity of the commercial ray species from the Irish Sea. J Northw Atl Fish Sci 35:47–66Google Scholar
  21. Gallagher MJ, Nolan CP, Jeal F (2005b) Structure and growth processes of caudal thorns. J Northw Atl Fish Sci 35:125–129Google Scholar
  22. Henderson AC, Arkhipkin AI, Chtcherbich JN (2004) Distribution, growth and reproduction of the white-spotted skate Bathyraja albomaculata (Norman, 1937) around the Falkland Islands. J Northw Atl Fish Sci 35: Scholar
  23. Holden MJ, Meadows PS (1962) The structure of the spine of the spur dogfish (Squalus acanthias) and its use for age determination. J Mar Biol Assoc U K 42:179–197CrossRefGoogle Scholar
  24. Holden MJ, Vince MR (1973) Age validation studies on the centra of Raja clavata using tetracycline. Journal du Conseil International pour l’Exploration de la Mer 35:13–17Google Scholar
  25. Kulka DW, Miri CM (2003) The status of thorny skate (Amblyraja radiata Donovan, 1808) in NAFO Divisions 3L, 3N, 3O and subdivisions 3Ps. Canadian Science Advisory Secretariat Research Document—2003/031Google Scholar
  26. Kulka DW, Mowbray FK (1999) An overview of the grand banks skate fishery. In: Shotton R (ed) Case studies of the management of elasmobranch fisheries. FAO Fisheries Technical Paper, Rome pp 47–73Google Scholar
  27. Natanson LJ (1993) Effect of temperature on band deposition in little skate. Copeia 1:199–206CrossRefGoogle Scholar
  28. Officer RA (1995) Vertebral mineralisation patterns in gummy and school sharks and their utility for age determination. Ph.D Thesis, University of Melbourne, Victoria, AustraliaGoogle Scholar
  29. Officer RA, Gason A, Walker TI, Clement JG (1996) Sources of variation in counts of growth increments in vertebrae from gummy shark, Mustelus antarcticus, and school shark, Galeorhinus galeus: implications for age determination. Can J Fish Aquat Sci 53:1765–1777CrossRefGoogle Scholar
  30. Rätz HJ (1992) Decrease in the fish biomass of West Greenland (Subdivisions 1B-1F), continued. NAFO SCR 92/40, serial no. N2088Google Scholar
  31. Rätz HJ (1999) Structures and changes of the demersal fish assemblage off Greenland, 1982–96. NAFO Sci Coun Studies 32:1–15Google Scholar
  32. Smith WD, Perez CR, Ebert DA (2005) Growth of the California skate, Raja inornata: assessment of multiple aging structures and somatic growth models. In: Abstract. American Society of Ichthyologists and Herpetologists/American Elasmobranch Society/Annual Meeting. Tampa, FLGoogle Scholar
  33. Stehmann M, Burkel DL (1984) Rajidae. In: Whitehead PJP, Bauchot ML, Hureau JC, Nielson J, Tortonese E (eds) Fishes of the north-eastern Atlantic and the Mediterranean, vol 1. UNESCO, Paris, pp 163–196Google Scholar
  34. Stehmann MFW, Merrett NR (2001) First records of advanced embryos and egg capsules of Bathyraja skates from the deep north-eastern Atlantic. J Fish Biol 59:338–349CrossRefGoogle Scholar
  35. Sulikowski JA, Kneebone J, Elzey S, Jurek J, Danley PD, Howell WH, Tsang PCW (2005) Age and growth estimates of the thorny skate (Amblyraja radiata) in the western Gulf of Maine. Fish Bull 103:161–168Google Scholar
  36. Templeman W (1984) Migrations of thorny skate, R. radiata, tagged in the Newfoundland area. J Northw Atl Fish Sci 5:55–63Google Scholar
  37. Templeman W (1987) Length-weight relationships, morphometric characteristics and thorniness of thorny skate (Raja radiata) from the northwest Atlantic. J Northw Atl Fish Sci 7:89–98Google Scholar
  38. Vinther M (1989) Some notes on the biology of the starry ray Raja radiata, in the North Sea. Working Document for ICES study group on elasmobranch fisheries, April 1989, 20pGoogle Scholar
  39. Walker PA, Hislop JRG (1998) Sensitive skates or resilient rays? Spatial and temporal shifts in ray species composition in the central and north-western North Sea between 1930 and the present day. ICES J Mar Sci 55:392–402CrossRefGoogle Scholar
  40. Walker PA (1999) Fleeting images dynamics of north sea ray populations. Ph.D. Thesis, University of AmsterdamGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  • Michael J. Gallagher
    • 1
  • Marianne J. Green
    • 2
  • Conor P. Nolan
    • 1
  1. 1.Irish Sea Fisheries BoardKillybegs, Co.DonegalIreland
  2. 2.Killybegs Fishermen’s OrganisationKillybegs, Co.DonegalIreland

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