Post-Cephalic White Spot Syndrome in Salmonids
This report documents a phenomenon in salmonids involving one or more white spots generally located in the mid-dorsal nape or occipital region immediately posterior of the fishes ’ head. The syndrome, post-cephalic white spot (PCWS), varies widely among populations. When present it often is found in...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.561.4061 http://www.npafc.org/new/publications/Technical Report/TR5/page 100-102(Heard).pdf |
| Summary: | This report documents a phenomenon in salmonids involving one or more white spots generally located in the mid-dorsal nape or occipital region immediately posterior of the fishes ’ head. The syndrome, post-cephalic white spot (PCWS), varies widely among populations. When present it often is found in less than 0.1 % of individuals in a population although in some instances occurrence rates can be considerably higher. This anomaly is easily overlooked and often goes unnoticed, especially when viewing a large number of fish. The white pigment spots, only a few millimeters in diameter in juveniles, grow allometrically and are larger in older fish. I first observed PCWS in juvenile sockeye salmon in 1975 (Fig. 1). These fish were progeny of adults from Nakvassin Creek at the west end of Port Herbert, a 4.8 km fiord on Baranof Island in Southeast Alaska. Adult salmon were collected and taken to the nearby National Marine Fisheries Service Field Station at Little Port Walter where they were spawned as part of a study to evaluate rearing of smolts in estuarine net pens (Wertheimer et al. 1983). Since first observing PCWS the anomaly has been found to occur in all five species of North American salmon, rainbow trout, Dolly Varden char, and Atlantic salmon. Documentation of these findings was accomplished through careful observations by myself and by the solicited assistance of many other individuals. Much of this information documents the presence of PCWS in 37 different populations of salmonids from Alaska, Washington, Oregon |
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