Tag Archives: fisheries

The Return of Lahontan Cutthroat Trout

The New York Times had a terrific story on Wednesday on the recovery of an endemic trout previously believed to be extinct since the 1940s in Pyramid Lake, Nevada. As I am currently teaching my class, Ecology, Evolution, and Human Health, with its emphasis on adaptation as local process and human-environment interaction, I was happy to see such an excellent story about local adaptation. In a nutshell, the trout was over-fished and also suffered devastating population declines in Pyramid Lake because of predation from introduced brook trout (and other exotic salmonids) and hybridization with introduced rainbows. This is, alas, an all too common story for trout endemics of western North America. A remanent population of Lahontan cutthroats, that were genetically very similar to the original Pyramid stock, was found in a Pilot Peak stream near the Utah border and samples from this population were brought to a USFWS breeding facility in cooperation with the Paiute Nation.  It sounds like the breeding/stocking program has been a tremendous success and the Lahontan cutties have now returned to Pyramid Lake. A big part of the story appears to be the intensive management of the main prey item of Lahontan cutties, the cui-ui sucker, which was devastated  following the construction of the Derby Dam in 1905.

This was all great news, but the thing that really caught my attention (because I’m currently teaching this class that focuses on adaptation) was the fact that the re-introduced Lahontan cutties have thrived so rapidly:

Since November, dozens of anglers have reported catching Pilot Peak cutthroats weighing 15 pounds or more. Biologists are astounded because inside Pyramid Lake these powerful fish, now adolescents, grew five times as fast as other trout species and are only a third of the way through their expected life span.

Can you say adaptation?! There is something about the interaction between this particular cutthroat species and the environment of Pyramid Lake that makes for giant fish as long as the juveniles can escape predation by exotic salmonids and adults can prey on their preferred species. Great news for anglers, great news for the Paiute Nation, great news for ecology.

Devastating Virus in Tasmanian Abalone Fishery

A news story reports the outbreak of abalone viral ganglioneuritis in Tasmania.  This is the first report of the disease in Tasmanian fisheries.  In fact, the disease appears to be quite newly emergent since, according to the Department of Primary Industries for the State of Victoria, the virus was previously not described in Australia prior to 2005.  Since 2005, it has been devastating abalone fisheries in Victoria.  Now it’s in Tasmania.  One theory for the emergence of this herpes-like virus is that it is actually endemic in abalone populations and usually harmless. Environmental stress (e.g., via warming or polluted water) could induce increased virulence, leading to the high observed mortality rates.  This is an outbreak to keep an eye on. The PROMED-mail moderator writes this about the virus:

Ganglioneuritis is an interesting condition causing inflammation in the nervous tissue, which swells. The result is curling of the abalone foot and swelling of the mouth. Thus, the organism cannot eat and looses its grip on the rocks it so depends on.

Abalone viral ganglioneuritis (AVG) is a highly virulent herpes-like virus, undescribed in Australia before 2005, and still not well characterized. The virus affects the nervous tissue of abalone and rapidly causes death. The virus can be spread through direct contact, through the water column without contact, and in mucus that infected abalone produce before dying. The virus is thought to survive only a short time when out of a moist environment.