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A 25-year study of climatic and density-dependent population regulation of common shrimp Crangon crangon (Crustacea: Caridea) in the Bristol Channel
Henderson, P.A.; Seaby, R.M.; Somes, J.R. (2006). A 25-year study of climatic and density-dependent population regulation of common shrimp Crangon crangon (Crustacea: Caridea) in the Bristol Channel. J. Mar. Biol. Ass. U.K. 86(2): 287-298. dx.doi.org/10.1017/S0025315406013142
In: Journal of the Marine Biological Association of the United Kingdom. Cambridge University Press/Marine Biological Association of the United Kingdom: Cambridge. ISSN 0025-3154, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Henderson, P.A.
  • Seaby, R.M.
  • Somes, J.R.

Abstract
    The results of a 25-year study of the population dynamics of the common shrimp, Crangon crangon, in the Bristol Channel are presented. The population size varied seasonally, with maximum abundance occurring in early autumn at the completion of annual recruitment. The number of recruits changed greatly between years, and was positively correlated with both average water temperature from January to August, and river flow rate, and negatively correlated with the Winter North Atlantic Oscillation Index. A wide range of other physical and biotic variables was found to have no significant impact on C. crangon abundance. The positive relationship between temperature and C. crangon abundance observed for the Atlantic coast during this study is the opposite of that found for southern North Sea populations. Similar contradictory responses have been noted previously for flatfish such as sole, Solea solea. This suggests that global variables may act to produce different outcomes for Atlantic and North Sea populations of the same species. Over-winter mortality was found to vary with population size so that the adult C. crangon population in spring was found to be remarkably stable, and little influenced by temperature or other variables. The mortality rate increased with population size producing clear evidence of density-dependent control. It is suggested that this stability is linked to the constant limited availability of suitable habitat, with individuals unable to find shelter vulnerable to a range of predatory fish. Given the pivotal role of C. crangon within the northern European estuarine ecosystems, this stability may be a critical component for the overall stability of the system. A particular feature of this study was the exceptional recruitment observed in October 2002. This did not result in any subsequent increase in adult C. crangon numbers, possibly because there was a synchronous increase in a wide range of predators. While the adult population has remained stable and showed no temporal trend, there has been an increase in both the average magnitude and between year variability in recruitment, which can be related predominately to the recent increase in water temperature. The difficulty of predicting the response of this population to continued climate warming is discussed. If temperature continues to rise, the present power law describing the increase in recruitment with temperature must inevitably break down. If this were to occur, the future trajectory of the C. crangon population could not be predicted, and the continued stability of this ecosystem would no longer be assured.

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