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Abundance, movements and size of gadoids (Teleostei) in the Severn Estuary

  • P. N. Claridge (a1) and I. C. Potter (a1)


Samples collected regularly from the intake screens of power stations between July 1972 and June 1977 demonstrate that the Gadidae is the most abundant and diverse teleost family in the inner Bristol Channel and Severn Estuary. The first records for the Severn Estuary of two cold water species, northern rockling and Norway pout, which were present in appreciable numbers, may be related to the effects of the changes that commenced in south-western English waters during the 1960s. Maximum numbers of the five most abundant gadoids were attained in different years, with the greatest catches being recorded for whiting and poor cod in 1975/6, bib and pollack in 1974/5 and northern rockling in 1976/7. Peak abundance in the middle estuary was reached by whiting, bib, poor cod and pollack in the autumn and by northern rockling in the winter or early spring. The 0 + age class of these species, which was always by far the most predominant category, showed increases in mean length during their relatively short stay in the estuary. Movement out of the shallows of the inner Severn Estuary by whiting and also apparently by some other gadoids occurred when salinities fell below 10‰. The size of poor cod and pollack in the autumn was not as great in 1974 as in 1975 and 1976, presumably reflecting the effect on growth of lower summer temperatures in the first of these years. Poor cod was represented by five age classes and attained at the end of the first to fifth years of life standard lengths of approximately 80 mm (≡4.8 g), 110 mm (≡11.7g), 140 mm (≡23.0 g), 170 mm (≡39.6 g) and 210 mm (≡71.6 g) respectively.


Corresponding author

School of Environmental and Life Sciences, Murdoch University, Murdoch, Western Australia 6150.


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Abou-Seedo, F. S. & Potter, I. C., 1979. The estuarine phase in the spawning run of the river lamprey Lampetra fluviatilis. Journal of Zoology, 188, 525.
Badsha, K. S. & Sainsbury, M., 1978. Aspects of the biology and heavy metal accumulation of Ciliata mustela. Journal of Fish Biology, 12, 213220.
Beal, K. L., 1980. Territorial sea fisheries management and estuarine dependence. In Estuarine Perspectives (ed. Kennedy, V. S.), pp. 6777. Academic Press.
Blaber, S. J. M. & Blaber, T. G., 1980. Factors affecting the distribution of juvenile estuarine and inshore fish. Journal of Fish Biology, 17, 143162.
Blacker, R. W., 1981. Recent occurrences of blue whiting, Micromesistius poutassou, and Norway pout, Trisopterus esmarkii, in the English Channel and southern North Sea. Journal of the Marine Biological Association of the United Kingdom, 61, 307313.
Chubb, C. F., Potter, I. C., Grant, C. J., Lenanton, R. C. J. & Wallace, J., 1981. Age structure, growth rates and movement of sea mullet, Mugil cephalus L., and yellow-eye mullet, Aldrichetta forsteri (Valenciennes), in the Swan-Avon river system, Western Australia. Australian Journal of Marine and Freshwater Research, 32, 605628.
Claridge, P. N. & Gardner, D. C., 1977. The biology of the northern rockling, Ciliata septentrionalis, in the Severn Estuary and Bristol Channel. Journal of the Marine Biological Association of the United Kingdom, 57, 839848.
Claridge, P. N. & Gardner, D. C., 1978. Growth and movements of the twaite shad, Alosa fallax (Lacépède), in the Severn Estuary. Journal of Fish Biology, 12, 203211.
Claridge, P. N. & Potter, I. C., 1983. Movements, abundance, age composition and growth of bass, Dicentrarchus labrax, in the Severn Estuary and inner Bristol Channel. Journal of the Marine Biological Association of the United Kingdom, 63, 871879.
Cooper, A., 1980. Gadoid populations of western Scottish sea lochs and their exchanges with west coast stocks. In Fjord Oceanography (ed. Freeland, H. J., Farmer, D. M. and Levings, C. D.), pp. 415421. Plenum Press.
Cronin, L. E. & Mansueti, A. J., 1971. The biology of the estuary. In Proceedings of a Symposium on the Biological Significance of Estuaries (ed. Douglas, P. A. and Stroud, R. H.), pp. 1439. Washington, D.C.: Sports Fishing Institute.
Day, J. H., Blaber, S. J. M. & Wallace, J. H., 1981. Estuarine fishes. In Estuarine Ecology with Particular Reference to Southern Africa (ed. Day, J. H.), pp. 197221. Rotterdam: Balkema.
Department of Energy, United Kingdom, 1981. Tidal Power from the Severn Estuary. London: Her Majesty's Stationery Office. [Energy Paper no. 46.]
Farmer, G. J. & Beamish, F. W. H., 1969. Oxygen consumption of Tilapia nilotica in relation to swimming speed and salinity. Journal of the Fisheries Research Board of Canada, 26, 28072821.
Gardner, D. C., 1978. The Biology of the Whiting in the Severn Estuary and the Bristol Channel. M.Sc. Thesis, University of Bath.
Gordon, J. D. M., 1977 a. The fish populations of inshore waters of the west coast of Scotland. The unusual occurrence of the blue whiting (Micromesistius poutassou) and some notes on its biology. Journal of Fish Biology, 11, 121124.
Gordon, J. D. M., 1977 b. The fish populations of the west coast of Scotland. The biology of the Norway pout (Trisopterus esmarkii). Journal of Fish Biology, 10, 417430.
Gordon, J. D. M., 1977 c. The fish populations in inshore waters of the west coast of Scotland. The distribution, abundance and growth of the whiting (Merlangius merlangus L.). Journal of Fish Biology, 10, 587596.
Gordon, J. D. M. & De, Silva S. S., 1980. The fish populations of the west Scotland shelf. Part 1. Oceanography and Marine Biology, an Annual Review, 18, 317366.
Hartley, P. H. T., 1940. The Saltash tuck-net fishery and the ecology of some estuarine fishes. Journal of the Marine Biological Association of the United Kingdom, 24, 168.
Huddart, R. & Arthur, D. R., 1971. Lampreys and teleost fish, other than whitebait, in the polluted Thames estuary. International Journal of Environmental Studies, 2, 143152.
Lenanton, R. C. J., Robertson, A. I. & Hansen, J. A., 1982. Nearshore accumulations of detached macrophytes as nursery areas for fish. Marine Ecology – Progress Series, 9, 5157.
Lloyd, A. J., 1941. Studies on the biology of the Bristol Channel. V. The marine fish fauna of the southern shores of the Bristol Channel. Proceedings of the Bristol Naturalists’ Society, 9, 202230.
Lutz, P. L., 1975. Adaptive and evolutionary aspects of the ionic content of fishes. Copeia, 1975, 369373.
Mchugh, J. L., 1976. Estuarine fisheries: are they doomed? In Estuarine Processes, vol. 1 (ed. Smith, R. F., Swartz, A. H. and Massman, W. H.), pp. 1527. Academic Press.
Maddock, L. & Swann, C. L., 1977. A statistical analysis of some trends in sea temperature and climate in the Plymouth area in the last 70 years. Journal of the Marine Biological Association of the United Kingdom, 57, 317338.
Matthews, L. H., 1933. The sea fish and fisheries of the Bristol district. Proceedings of the Bristol Naturalists’ Society, 7, 442462.
Palmer, C. J. & Culley, M. B., 1983. Aspects of the biology of the sandsmelt Atherina boyeri Risso, 1810 (Teleostei: Atherinidae) at Oldbury-upon-Severn, Gloucestershire, England. Estuarine and Coastal Shelf Science, 16, 163173.
Palmer, C. J., Culley, M. B. & Claridge, P. N., 1979. A further occurrence of Atherina boyeri Risso in North Eastern Atlantic waters. Environmental Biology of Fishes, 4, 7175.
Pollard, D. A., 1976. Estuaries must be protected. Australian Fisheries, 36, 610.
Radford, P. J., Uncles, R. J. & Morris, A. W., 1981. Simulating the impact of technological change on dissolved cadmium distribution in the Severn Estuary. Water Research, 15, 10451052.
Raitt, D. F. S., 1965. The stocks of Trisopterus esmarkii (Nilsson) off north-west Scotland and in the North Sea. Marine Research, no. 1, 24 pp.
Raitt, D. F. S., 1968 a. The population dynamics of the Norway pout in the North Sea. Marine Research, no. 5, 24 pp.
Raitt, D. F. S., 1968 b. Synopsis of biological data on the blue whiting Micromesistius poutassou (Risso, 1810). F.A.O. Fisheries Synopsis, no. 34, 35 pp.
Raitt, D. F. S., 1968 c. The biology and commercial potential of the blue whiting in the north-east Atlantic. Rapport et procés-verbaux des rèunions. Conseil permanent international pour l'exploration de la mer, 158, 108115.
Raitt, D. F. S. & Adams, J. S., 1965. The food and feeding of Trisopterus esmarkii (Nilsson) in the northern North Sea. Marine Research, no. 3, 28 pp.
Raitt, D. F. S. & Mason, J., 1968. The distribution of Norway pout in the North Sea and adjacent waters. Marine Research, no. 4, 19 pp.
Russell, F. S., 1980. On the distribution of postlarval fish in the Bristol Channel. Bulletin of Marine Ecology, 8, 283290.
Scheffé, H., 1959. The Analysis of Variance. 477 pp. John Wiley.
Southward, A. J., 1980. The western English Channel – an inconstant ecosystem? Nature, London, 285, 361366.
Southward, A. J. & Mattacola, A. D., 1980. Occurrence of Norway pout, Trisopterus esmarkii (Nilsson) and blue whiting, Micromesistius poutassou (Risso), in the western English Channel off Plymouth. Journal of the Marine Biological Association of the United Kingdom, 60, 3944.
Titmus, G., Claridge, P. N. & Potter, I. C., 1978. Growth and abundance of o-group herrings, Clupea harengus L., in the Severn Estuary. Zoological Journal of the Linnean Society, 64, 251260.
Van, Den Broek W. L. F., 1979. A seasonal survey of fish populations in the Lower Medway Estuary, Kent, based on power station screen samples. Estuarine and Coastal Marine Science, 9, 115.
Wheeler, A., 1969. The Fishes of the British Isles and North-West Europe. 613 pp. Macmillan: London.
Wheeler, A., 1979. The Tidal Thames. The History of a River and Its Fishes. 228 pp. London: Routledge & Kegan Paul.


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