Rotten Smell and Mushy Sockeye Salmon (Oncorhynchus nerka) and Pacific Halibut (Hippoglossus stenolepis)

Observation: Fishing about a mile and a half up the Meshik River and caught about 20 sockeye salmon. Only saved about four fish that appeared normal. The others had a rotten smell and the meat had a mushy texture. When they were gutted, you could put your hands through the meat. The meat color was normal, but the guts were black. Normal skin and scales- looked like a good fish when you first pulled it out. Water temperature was way warmer than normal. Caught about a mile and a half from the mouth of the river. Fish from that area in previous year have been fine. Same thing happened with the halibut in 2016, around the Chigniks. They were hard to catch because they went deep, and then the ones that were caught were mush. Cold winter followed, and then they came back up. Observation by Erica Mitchell with Jimmy Christensen, local resident.

LEO says: The identification of the cause for these symptoms in the sockeye can be done through examination of the fish, samples, or possibly a photos. We have forwarded the post to Jayde Ferguson a fish pathologists at ADFG, in the event that a consult can be provided based on the description. Observers are asked to take detailed photos with fish illness cases, and to save a fish for analysis. There are fish illnesses that have been associated with mushy and smelly condition of salmon in Alaska. One example is Ichthyophonus hoferi of "Ich". Stress caused by environmental conditions including warmer temperatures have been connected with an increase in illness such as Ich, a protozoa. According to Common Disease of Wild and Cultured Fishes in Alaska (p. 46), Ich causes systemic disease and in particular effects major organs like the heart. Ich may be one of the possible suspects but there are others. The condition while harmless to humans, makes the salmon mushy and unappetizing, and makes the fish difficult to dry. We defer to ADFG for expertise on the most likely causes for the condition in the Meshik River salmon. In regard to mushy halibut, there is a relatively new fish illness that has been documented in the Kachemak Bay and Prince William Sound areas (Homer, Seward etc) called Mushy Halibut Syndrome which has been frustrating fisherman due to the impact on the quality of the fish. Mostly in smaller fish, the condition causes the muscle of the fish to be opaque and jelly like. According to the bulletin from ADFG, the cause is thought to be associated with a nutritional deficiency. The condition does not affect the safety of the food, only the quality. M. Brubaker For more information about Sockeye salmon see: Sockeye Salmon (Oncorhynchus nerka) Species Profile. For more information about pacific halibut see Pacific Halibut (Hippoglossus stenolepis) Species Profile M. Tcheripanoff

Alaska Department of Fish and Game Consult: Jayde Ferguson writes:" I would say that although Ich is a possibility it's probably less likely than something like Kudoa. Ich will present with white spots too, which are the chronic inflammatory granulomas. Kudoa is a myxozoan parasite that releases proteolytic enzymes that destroys the tissue after the fish dies. It's been called tapioca disease due to the consistency of the flesh. Any samples available? Kudoa is actually pretty common here and in the Pacific Northwest. It's a marine parasite.Regarding the mushy halibut syndrome, there is not much known at this time. I would say that it's not that new though. The first case of mushy halibut in the database was in 1998. The IPHC now has an online reporting form."

Resources:

Meyers T., Burton T., Bentz C., and Starkey N., Common Disease of Wild and Cultured Fishes in Alaska . Alaska Department of Fish and Game, Fish Pathology Laboratory, July 2008. https://www.adfg.alaska.gov/static/species/disease/pdfs/fish_disease_book.pdf

Mushy Halibut Syndrome Alaska Department of Fish and Game

Moles A., Parasites of the Fishes of Alaska and Surrounding Waters. Alaska Fishery Research Bulletin 12(2):197–226. 2007. Copyright © 2007 by the Alaska Department of Fish and Game

Kenneth Weiss. Alaska salmon may bear scars of global warming. Los Angeles Times. June 15, 2008.