Infestations of wild adult Atlantic salmon (Salmo salar L.) by the ectoparasitic copepod sea louse Lepeophtheirus salmonis Kroyer: prevalence, intensity and the spatial distribution of males and females on the host fish
The copepod Lepeophtheirus salmonis Kroyer is a specific ectoparasite of North Atlantic and Pacific salmonids in their marine phases. We compared infestations of L. salmonis on wild Atlantic salmon (Salmo salar L.) captured in estuarine (Firth of Tay, east Scotland; 1995, 1996) and marine coastal wa...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2000
|
| Subjects: | |
| Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/infestations-of-wild-adult-atlantic-salmon-salmo-salar-l-by-the-ectoparasitic-copepod-sea-louse-lepeophtheirus-salmonis-kroyer-prevalence-intensity-and-the-spatial-distribution-of-males-and-females-on-the-host-fish(be7c7f50-350f-44a4-8567-bcebc0c57a34).html https://doi.org/10.1023/A:1004031318505 http://www.scopus.com/inward/record.url?scp=0033821837&partnerID=8YFLogxK |
| Summary: | The copepod Lepeophtheirus salmonis Kroyer is a specific ectoparasite of North Atlantic and Pacific salmonids in their marine phases. We compared infestations of L. salmonis on wild Atlantic salmon (Salmo salar L.) captured in estuarine (Firth of Tay, east Scotland; 1995, 1996) and marine coastal waters (Strathy Point, north Scotland; 1998, 1999). Host fish from the Tay were caught by sweep netting, whilst those from Strathy Point were trapped in anchored bagnets. Fish capture method and exposure of the parasites to brackish conditions may both have detrimental effects on the retention of L. salmonis by the host, and hence possibly lead to their being under-estimated on returning adult fish. At Strathy Point, we recorded (i) an infestation prevalence of 100%, (ii) mean log abundances of pre-adult + adult L. salmonis at 19 (1998) and 24 (1999) per fish, (iii) 85/93% of all L. salmonis as being adults and (iv) overall 68/69% females. Fish caught in the upper Firth of Tay showed significantly lower prevalences, intensities and abundances of L. salmonis and probably had lost part or all of their lice burdens prior to capture, whereas those sampled from Strathy Point were apparently minimally affected by capture method or brackish water influences. The loss of parasites for the Tay fish was not markedly biased to males or females, or to pre-adult versus adult developmental stages. There were significantly greater abundances of L. salmonis on two sea-winter fish (30 lice per fish) than on one sea-winter fish (17 lice per fish) sampled at Strathy Point in 1998. There are several possible explanations for such age-related patterns of abundance, but the indications are that (i) initial infestation of smolts occurs in coastal waters, (ii) infestation of hosts in the open ocean is a persistent event, and (iii) oceanic reinfestation outweighs mortality losses of L. salmonis. This parasite typically occupies rather few zones on the host fish covering only a small percentage of the total available body surface area. Female ... |
|---|