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.
About the OSU College of Science: As one of the largest academic units at OSU, the College of Science has 14 departments and programs, 13 pre-professional programs, and provides the basic science courses essential to the education of every OSU student. Its faculty are international leaders in scientific research.
The study this story is based on is available online: http://hdl.handle.net/1957/22084
Michael Kent | EurekAlert!
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy