Caligus elongatus

From Fish
Lumpfish infected with more than 600 sea lice (Caligus elongatus)
Caligus elongatus, male

Caligus elongatus is a copepod lice that parasitises salmon.

It is one of two major species of sea lice that parasitize farmed salmon, the other being Lepeophtheirus salmonis.

Clinical signs

Sea lice affect salmon in a variety of ways, namely; by reducing fish growth; by causing loss of scales, which leaves the fish open to secondary infections; and by damaging the fish, which reduces its marketability[1].

Most of the damage caused by these parasites is thought to be mechanical, carried out during the course of attachment and feeding. Inflammation and hyperplasia (enlargement caused by an abnormal increase in the number of cells in an organ or tissue) have been recorded.


Management practice is such that chemotherapeutic treatments are focused on controlling L. salmonis rather than C. elongatus. During the period under study the types of treatment used have altered substantially. In commercial hatcheries, the majority of treatments are by hydrogen peroxide with some use of dichlorvos. Cypermethrin, deltamethrin and azamethiphos have also been used with success[2].


  1. Wooten, R., Smith, J. W. & E. A. Needham. (1982) Aspects of the biology of the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus on farmed salmonids, and their treatment. Proceedings of the Royal Society of Edinburgh 81B:185-197
  2. Landsberg J.H., Vermeer G.K., Richards S.A. & Perry N. (1991) Control of the parasitic copepod Caligus elongatus on pondreared red drum. Journal of Aquatic Animal Health 3:206–209