Tag Archives: Oregon Hatchery Research Center

Earth’s Geomagnetic Field Doesn’t Just Aid Salmon Migration-Getting Out Of The Gravel Too

THE FOLLOWING IS A PRESS RELEASE FROM OREGON STATE UNIVERSITY

Researchers who confirmed in recent years that salmon use the Earth’s geomagnetic field to guide their long-distance migrations have found that the fish also use the field for a much simpler and smaller-scale migration: When the young emerge from gravel nests to reach surface waters.

FRESHLY HATCHED SALMON. (RICHARD BELL, TOM QUINN, UNIVERSITY OF WASHINGTON)

The study is published in the journal Biology Letters. The findings have important implications for understanding how salmon navigate across the wide range of habitats they encounter.

“From very early on in the life cycle, salmon have the ability to detect and respond to geomagnetic information,” said David Noakes, director of the Oregon Hatchery Research Center and senior author on the study. “This matters because we need to know how rearing conditions might impact the fish, particularly in the case of hatcheries – where we already have some evidence that exposure to unnatural magnetic fields can disrupt the ability of steelhead trout to orient appropriately.”

The Oregon Hatchery Research Center is a collaborative research project of Oregon State University, where Noakes is a professor and senior scientist in the College of Agricultural Sciences, and the Oregon Department of Fisheries and Wildlife. Michelle Scanlan, faculty research assistant at OSU and co-lead author on the study, said, “We show that the magnetic sense in salmon can be used for three-dimensional orientation – as a map, a compass and an indication of which way is up.”

When salmon spawn, the mothers bury their fertilized eggs in gravel “redds” where they incubate for weeks or months. Upon hatching, the young salmon remain in the gravel until they deplete residual yolk stores, after which they emerge from the gravel and live above the substrate in the open water of the stream or river.

The newly-hatched fish appear to use the direction of magnetic field lines to help determine which way is up. This finding indicates that magnetic cues are used for three-dimensional orientation across a wide range of spatial scales and habitats.

“Getting out of the gravel is not as easy as it might seem, but it is of critical importance,” said Noakes, who in previous studies examined the role of temperature, light, and water current on salmon emergence.

“All could be used by the fish, but none was essential,” he said. “In the absence of these cues, fish still moved out of the gravel. Now we have the answer to that.”

The research team constructed a system of copper-wire coils through which a very low electric current could be run to precisely control the magnetic field surrounding fish. Experiments were carried out under complete darkness and in still water.

Within the coil system, fish that were developmentally ready to move into surface waters were placed at the bottom of plastic tubes that had been filled with clear glass marbles, to mimic gravel. The researchers measured the height fish moved up in the tubes over a 30-minute period.

One group of salmon were exposed to the normal magnetic field in Oregon and another group of salmon to an inverted magnetic field. Fish in the normal magnetic field moved significantly further up the tubes than did those that experienced the inverted magnetic field. The team ruled out the possibility that fish were simply startled by the sudden change in electromagnetic conditions by running the same amount of electric current required to invert the magnetic field in the opposite direction.

“Given that only inverting the magnetic field influenced fish movement, it seems salmon use the direction of field lines to orient vertically during their emergence from gravel – our findings are difficult to interpret in any other way,” said Nathan Putman, senior scientist at LGL Ecological Research Associates in Bryan, Texas, and co-lead author on the study.

Study collaborators included researchers in OSU’s College of Agricultural Sciences and College of Earth, Ocean, and Atmospheric Sciences; the University of Washington and the University of North Carolina at Chapel Hill.

The study was funded by Oregon Sea Grant, Oregon Department of Fish and Wildlife, Oregon Hatchery Research Center and OSU’s Department of Fisheries and Wildlife.

Cookie Cutters? Maybe Not Entirely, OSU Research On Hatchery Chinook Suggests

THE FOLLOWING IS A PRESS RELEASE FROM OREGON STATE UNIVERSITY

Hatchery-raised chinook salmon sort themselves into surface- and bottom-oriented groups in their rearing tanks. This behavior might be due in part to the fish’s genes, according to an Oregon State University study.

YOUNG HATCHERY CHINOOK STRATIFY INTO SOME FISH THAT HANG OUT ON THE SURFACE AND SOME THAT LIKE THE BOTTOM. THAT GENETIC BEHAVIOR IS SIMILAR TO THE DIFFERENCE IN WHERE YOUNG WILD WILLAMETTE AND MCKENZIE RIVER CHINOOK OCCUR, ACCORDING TO OREGON STATE UNIVERSITY. (OSU)

The finding, published in the journal Environmental Biology of Fishes, could change a commonly held view that hatchery-raised fish are generally expected to behave in the same manner, said Julia Unrein, who led the study as a master’s degree student in the Oregon Cooperative Fish and Wildlife Research Unit in OSU’s College of Agricultural Sciences.

“What we found is hatchery juvenile chinook salmon are not made from the same mold,” Unrein said. “Perhaps by trying to force them to fit our model of what a ‘hatchery fish’ is and constrain them to specific release times, we may be overlooking the variation among individuals that we know is important for the survival of their wild counterparts.”

Carl Schreck, professor in OSU’s Department of Fisheries and Wildlife, said, “The implications relative to Endangered Species Act-listed fish may be profound if they serve to allow the creation of test fish for researchers to use when studying how to successfully get juvenile chinook to safely migrate through Willamette system reservoirs and dams. There are fish culture and habitat restoration implications, as well.”

The researchers first recognized this vertical self-sorting behavior, just as the young fish have used up their yolk and are feeding for the first time, at OSU’s Fish Performance and Genetics Laboratory. They observed that some chinook orient themselves near the surface and the remainder swam along the bottom of the tank.

When the researchers separated the surface- and bottom-fish into different tanks, the fish maintained their preferred vertical distribution for at least a year, Unrein said. The fish that fed at the surface continued to stay near the top and the ones that preferred the bottom remained deeper in the tank, even with the surface fish no longer competing for food that was provided at the surface.

They compared body size between the two groups two months after the first feeding began and then six months later. While initially the same size, by the end of the experiment the surface fish were significantly larger than the bottom fish, Unrein said.

“There were also consistent body shape differences, detected after two months of rearing and again six months later,” she said. “The surface fish had a deeper, shorter head and deeper body than the bottom fish, which was more streamlined. For the next four brood years, we looked at these variations and found they were consistent from year to year. For the fourth brood year, we held families separate to determine if the proportion of the two types of fish varied among families and they did, which suggests genetics plays a role.”

Unrein compared the body types of the surface and bottom fish to wild chinook juveniles collected in the Willamette River Basin by Eric Billman, when he was part of OSU’s research team. She found that surface fish are similar to the wild juveniles that rear in the Willamette River and leave their first fall, while the bottom fish resemble those rearing in the McKenzie River, an upper tributary of the Willamette, that leave as yearling spring smolts.

Unrein’s research was directed by Schreck and David Noakes, professor and senior scientist in the Oregon Hatchery Research Center in the Department of Fisheries and Wildlife.

“It is surprising that such behavioral sorting hadn’t been noticed before given that we’ve seen it at two different facilities, in different stocks of chinook salmon, and over numerous years,” Schreck said. “It is also present, although not as obvious, in steelhead trout.”

The study resulted from observations made during research funded by the U.S. Army Corps of Engineers, Portland District; the U.S. Geological Survey, the Oregon Department of Fish and Wildlife and the Oregon Hatchery Research Center.