Shell disease in the common shrimp Crangon crangon : variations within an enclosed estuarine system
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A field survey of the shrimp Crangon crangon (L.) from Poole Harbour, Dorset, England, revealed high incidences of shell disease, a condition causing exoskeletal erosion. Further samples collected from two subsystems within the harbour were subjected to more detailed analysis. The number, location and size of the lesions on each shrimp were analyzed with respect to sex and size class. Lesion incidences were higher than any previously recorded for the species, with a maximum of 87%. Lesion incidence, number and size were significantly higher in larger size classes of C. crangon, and the incidence and number of lesions were significantly higher in female shrimps than in males. The most frequently affected appendages were the antennae, pereiopods and pleopods, of which the outermost sections had the greatest lesion frequencies, namely the antennal flagellae, the propus and dactyl of the pereiopods and the exopodite of the pleopods. Several factors including pollution, fishing activity and population density have previously been cited as direct causes of shell disease. The results of the current study together with observations from published literature suggest that predatory and cannabilistic interactions combined with the high level of organic enrichment (both natural and anthropogenic) are more likely to have contributed to the high incidences observed than pollution or fishing activity.
KeywordsPopulation Density Detailed Analysis Fishing Size Class Field Survey
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