Featured Research

from universities, journals, and other organizations

Parasite loads an underlying cause of salmon mortality, linked to land use changes

Date:
August 15, 2011
Source:
Oregon State University
Summary:
A recent study suggests that parasites in fish, including threatened species of Oregon coho salmon, may have more profound impacts on fish health than has been assumed, and could be one of the key mechanisms by which habitat and land use changes cause salmon mortality.

Parasites and salmon. Research at Oregon State University suggests that parasites are a more significant threat to salmon that has previously been assumed, making them weaker, smaller and more vulnerable to predators.
Credit: Graphic courtesy of Oregon State University

A recent study suggests that parasites in fish, including threatened species of Oregon coho salmon, may have more profound impacts on fish health than has been assumed, and could be one of the key mechanisms by which habitat and land use changes cause salmon mortality.

It's not just the presence or absence of parasites that is important, the research found, but their numbers that can build up over years or decades and ultimately cause major impacts.

The study will be published soon in the journals Aquaculture, Journal of Parasitology, and International Journal of Parasitology. It was done by researchers from Oregon State University and other agencies, and concluded that heavy loads of parasites can affect salmon growth, weight, size, immune function, saltwater adaptation, swimming stamina, activity level, ability to migrate and other issues. Parasites drain energy from the fish as they grow and develop.

"We've known for a long time that salmon and other fish are affected by parasites, so that isn't new," said Mike Kent, an OSU professor of microbiology. "Because parasites have been present for decades, they have often been dismissed as a cause of increasing salmon mortality.

"But we're now getting a better appreciation that it's the overall parasite load that is so important," he said. "The higher levels of mortality only show up with significant increases in the parasite burden."

And that increase in parasite numbers, Kent said, is a slow, gradual response to warmer waters and heavier nutrient loads that can be a result of logging, agriculture, inadequate streamside protection and other land use or management changes over many years.

"Salmon can actually tolerate a fairly wide range of temperatures, it's not just the fact a stream is warmer that's killing them, in and of itself," he said. "We now believe that some of these forces are leading to heavier parasite loads. This could be important in understanding declining salmon populations."

Some of the digenean parasites that can infect salmon and other fish have complex life cycles, which include passage through the intestinal tracts of birds that eat fish, producing eggs and then infecting snails. Snails thrive in warmer water with higher nutrient loads from common fertilizers.

It's been historically difficult to study these issues in salmon, Kent said, because they migrate and cannot be easily analyzed, as fish can when they are trapped in a lake or pond.

In the new study, researchers did both laboratory and field analysis of fish in Oregon's West Fork Smith River. The impact of parasites on fish health were much more severe in a part of the river where water moved more slowly and nearby logging and agricultural practices increased water temperature and nutrient loads. Fish in this area had parasite infestations about 80 times higher than those higher up in the tributary.

The various impacts on fish health, the researchers said, could affect their ability to survive. Fish size influences juvenile overwinter survival, for instance, and swimming ability that's essential to avoiding predators.

"Understanding why certain salmon populations are heavily infected with these parasites, which likely are driven by landscape characteristics, could help in management or recovery planning," the scientists wrote in their conclusion, "given that our data indicates that severity of these infections are associated with survival."

The study was done by scientists from OSU and the Oregon Cooperative Fish and Wildlife Research Unit. The corresponding author was Jayde Ferguson, a doctoral student in the OSU Department of Microbiology, and other collaborators included researchers from the OSU Department of Statistics, College of Veterinary Medicine, and Carl Schreck in the Department of Fisheries and Wildlife. The research was supported by the Oregon Department of Fish and Wildlife.


Story Source:

The above story is based on materials provided by Oregon State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jayde A. Ferguson, Jeremy Romer, Jean C. Sifneos, Lisa Madsen, Carl B. Schreck, Michael Glynn, Michael L. Kent. Impacts of multispecies parasitism on juvenile coho salmon (Oncorhynchus kisutch) in Oregon. Aquaculture, 2011; DOI: 10.1016/j.aquaculture.2011.07.003

Cite This Page:

Oregon State University. "Parasite loads an underlying cause of salmon mortality, linked to land use changes." ScienceDaily. ScienceDaily, 15 August 2011. <www.sciencedaily.com/releases/2011/08/110815121523.htm>.
Oregon State University. (2011, August 15). Parasite loads an underlying cause of salmon mortality, linked to land use changes. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2011/08/110815121523.htm
Oregon State University. "Parasite loads an underlying cause of salmon mortality, linked to land use changes." ScienceDaily. www.sciencedaily.com/releases/2011/08/110815121523.htm (accessed July 22, 2014).

Share This




More Plants & Animals News

Tuesday, July 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Michigan Plant's Goal: Flower and Die

Michigan Plant's Goal: Flower and Die

AP (July 22, 2014) An 80-year-old agave plant, which is blooming for the first and only time at a University of Michigan conservatory, will die when it's done (July 22) Video provided by AP
Powered by NewsLook.com
San Diego Zoo Welcomes New, Rare Rhino Calf

San Diego Zoo Welcomes New, Rare Rhino Calf

Reuters - US Online Video (July 21, 2014) An endangered black rhino baby is the newest resident at the San Diego Zoo. Sasha Salama reports. Video provided by Reuters
Powered by NewsLook.com
Shark Sightings a Big Catch for Cape Tourism

Shark Sightings a Big Catch for Cape Tourism

AP (July 21, 2014) A rise in shark sightings along the shores of Chatham, Massachusetts is driving a surge of eager vacationers to the beach town looking to catch a glimpse of a great white. (July 21) Video provided by AP
Powered by NewsLook.com
$23.6 Billion Awarded To Widow In Smoking Lawsuit

$23.6 Billion Awarded To Widow In Smoking Lawsuit

Newsy (July 20, 2014) Cynthia Robinson claims R.J. Reynolds Tobacco Company hid the health and addiction risks of its products, leading to the death of her husband in 1996. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins