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SEPG 2135 - Date Awarded 2003
New Species of Caprellid (Amphipoda) in UK Waters: Description, Distribution and Ecological Significance
Dr Kate J. Willis & Dr Elizabeth J. Cook
Abstract
A large caprellid amphipod recently discovered in Scotland has been identified as Caprella mutica, a species indigenous to north-east Asia. C. mutica has since been identified at numerous locations along the Scottish west coast, the Hebrides, Shetland, Wales, and along the English south coast. Populations have only been found on artificial structures such as mooring ropes, aquaculture cages, boat hulls, and in harbours and marinas. Anecdotal evidence suggests the caprellid may have been introduced to Scotland in the early 1990s. Regular sampling at a Scottish salmon farm recorded abundant populations during the summer months with a maximum biomass of 109 AFDW g m-2 in July 2003. The sex ratio was skewed towards males in summer and females in winter. Rapid growth rates and a high reproductive output were observed in laboratory reared caprellids, with differentiation of the sexes possible by instar VI. Males developed faster than females and grew to a larger size. By instar X, male and female total body lengths were 15.5 and 12.3 mm, respectively. The time taken to reach instar X was 69 (males) and 77 (females) days. The maximum number of offspring produced by a female in a single clutch was 179. Caprellids maintained in the laboratory displayed opportunistic feeding behaviour. They were observed feeding on diatoms, fish feed, macroalgae, hydroids, brine shrimp, and other caprellids. Cannibalism was also observed. The evidence to date suggests C. mutica is a successful invader of British coastal waters and that its distribution range will continue to expand.
Full report: SEPG2135 
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