Publication Abstract

Ectoparasitic sea lice (Lepeophtheirus salmonis (Krøyer), Caligus elongatus (Nordmann) infestations of wild adult one sea-winter Atlantic salmon Salmo salar L. returning to Scotland, 1998-2005

Ectoparasitic sea lice (Lepeophtheirus salmonis (Krøyer), Caligus elongatus (Nordmann) infestations of wild adult one sea-winter Atlantic salmon Salmo salar L. returning to Scotland, 1998-2005

C.D. Todd, B.D.M. Whyte, J.C. MacLean and A.M. Walker

Caligid ectoparasitic copepods are major pathological pests on cultured Atlantic salmon (Salmo salar L.) and their population biology has been well studied in the farm environment. The ecology of caligid infestations of wild salmon is, by contrast, rather poorly understood. We monitored return migrant one sea-winter wild Atlantic salmon in Scotland annually between 1998 and 2005 for infestations of 2 caligids, Lepeophtheirus salmonis (Krøyer) (8 y) and Caligus elongatus Nordmann (7 y).  L. salmonis was 100% prevalent in all years, whereas C. elongatus ranged from 90–100%. Abundances fluctuated markedly between years and L. salmonis mean abundance (min.-max. 17.4–31.0) was significantly greater than for C. elongatus (min.-max. 2.9–23.8) in all except one year. A positive association in abundance of the 2 species, for individual fish within any one year, indicates weak or absent competitive effects on abundances for individual hosts. Individual fish within any one year appeared similarly vulnerable to infestation by either species, though Taylor’s power regression showed clear differences in density-related patterns of overdispersion amongst hosts for the 2 species. Host condition factor (expressed either as K or W_R) showed significant variation among years. Parasite species abundances were not, however, determined by host condition factor, and poor condition fish were no more likely to carry high infestations than were high condition fish.

Reference

C.D. Todd, B.D.M. Whyte, J.C. MacLean and A.M. Walker (2006) Ectoparasitic sea lice (Lepeophtheirus salmonis (Krøyer), Caligus elongatus (Nordmann) infestations of wild adult one sea-winter Atlantic salmon Salmo salar L. returning to Scotland, 1998-2005. Marine Ecology Progress Series, 328: 183-193

C.D. Todd, B.D.M. Whyte, J.C. MacLean and A.M. Walker*

Marine Ecology Progress Series, 328: 183-193