The behavioural, chemical and host ecology of two species of copepods (Copepoda: Caligidae) parasitic on Atlantic salmon (Salmo salar L.)

• Main Author: Smallman, Duncan Robert
• Published: University of Aberdeen 2009
• Subjects: 571.861; Atlantic salmon : Copepoda : Caligus : Fishes
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499727

<i>Caligus elongatus </i>and <i>Lepeophtheirus salmonis </i>are ectoparasites of Atlantic salmon and sea trout (<i>S. trutta).</i> Solid phase extraction (SPE) and stir bar sorptive extraction (SBSE) were used to investigate and compare the odour profiles of Atlantic salmon, sea trout, haddock and turbot. The behavioural responses of <i>L. salmonis </i>copepodids towards the different extracts of the four species were tested on Y-tube bioassays. Copepodids showed significant increases in swimming activity in the presence of SPE and SBSE extracts of salmon and sea trout. The copepodids showed a significant preference for SPE extracts of salmon and sea trout only. Haddock SPE extracts elicited a significant increase in activity but no significant odour preference. <i>L. salmonis</i> copepodid behaviour when presented with sea trout and haddock odours was tested in a Y-tube bioassay. Significant increases in activity in the presence of both species odours was found. Copepodids showed a significant preference for sea trout conditioned water over blank artificial seawater and for artificial seawater over haddock odour. <i>C. elongates</i> copepodids showed no significant chemotactic responses in Y-tube experiments. Analysis of video tracked three-way olfactometer experiments found significant increases in the swimming activity and larger turning angles by <i>C. elongates </i>in the presence of salmon odour. When compared to <i>L. salmonis, </i>significant differences in swimming behaviour were found. A weak but significant correlation was found between the ecology of the hosts and the presence or absence of Caligid copepods. This is discussed in the context of the ecological traits and the influence these have on potential co-occurrence. In addition the reproductive strategies of <i>C. elongatus</i> and <i>L. salmonis</i> were investigated and the differences found are discussed in the context of co-existence.