CANCELLED - Investigating host-specificity using microsatellites: A study of Lepeophtheirus salmonis infection on salmon (Oncorhynchus spp.) of the North Pacific

Background/Question/Methods

The salmon louse (Lepeophtheirus salmonis) is a marine ectoparasite specific to salmonids. Salmon lice have become a recent topic of research due to prevalence at salmonid aquaculture sites and their ability to negatively affect wild populations of salmon. Little research has been done on the population dynamics of L. salmonis; of this research there are conflicting views on sub-division within populations of lice. Pacific salmon vary in ability to resist infection which could provide differential ability of certain genotypes of lice to infect specific species of salmon. It is important to understand if lice populations are sub-divided by host species because it would provide knowledge on the transfer of aquaculture reared lice to wild salmon populations. The goal of this research is to infer host-specificity of lice using microsatellites and examine parasite load off the coast of Washington State. Lice were collected from three Pacific salmon species chinook (Oncorhynchus tshawytscha), pink (Oncorhynchus gorbuscha), and coho salmon (Oncorhynchus kisutch) in the wild using hook and line sampling techniques. Once landed fish were measured, weighed, lice were counted, collected haphazardly and stored in 70% ethanol, and then the fish were released. The main objectives of this study are 1) R_st values between lice collected from different host species will approach zero and, 2) parasite load of salmon lice are similar on three species of Pacific salmon.

Results/Conclusions

Analysis for genetic comparisons between populations of parasites is forthcoming. This study includes nine microsatellite loci which were developed by researchers examining spatial sub-division in populations of salmon lice. Once DNA from lice is isolated and amplified using polymerase chain reaction lengths of amplicons will be assessed by visual length polymorphisms with gel-electrophoresis, this process will yield number of alleles for each assumed population and R_st values will be assessed from these values. We found that species of Pacific salmon have similar parasite loads (p-value > 0.05) where no possible pairs of salmon species had parasite loads which were significantly different from one another. King salmon were the only host species for which a regression of fish length to number of parasites were significant (p-value < 0.05, R²=0.575).