Hatchery-raised chinook salmon kind themselves into surface- and bottom-oriented teams in their rearing tanks. This habits is perhaps due in half to the fish’s genes, in keeping with an Oregon State University research.
The discovering, revealed in the journal Environmental Biology of Fishes, may change a generally held view that hatchery-raised fish are usually anticipated to behave in the identical method, stated Julia Unrein, who led the research as a grasp’s diploma scholar 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 stated. “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, stated, “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 acknowledged this vertical self-sorting habits, simply because the younger fish have used up their yolk and are feeding for the primary time, at OSU’s Fish Performance and Genetics Laboratory. They noticed that some chinook orient themselves close to the floor and the rest swam alongside the underside of the tank.
When the researchers separated the surface- and bottom-fish into totally different tanks, the fish maintained their most well-liked vertical distribution for at the least a yr, Unrein stated. The fish that fed on the floor continued to remain close to the highest and those that most well-liked the underside remained deeper in the tank, even with the floor fish now not competing for meals that was offered on the floor.
They in contrast physique measurement between the 2 teams two months after the primary feeding started after which six months later. While initially the identical measurement, by the tip of the experiment the floor fish have been considerably bigger than the underside fish, Unrein stated.
“There were also consistent body shape differences, detected after two months of rearing and again six months later,” she stated. “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 in contrast the physique sorts of the floor and backside fish to wild chinook juveniles collected in the Willamette River Basin by Eric Billman, when he was a part of OSU’s analysis workforce. She discovered that floor fish are much like the wild juveniles that rear in the Willamette River and depart their first fall, whereas the underside fish resemble these rearing in the McKenzie River, an higher tributary of the Willamette, that depart as yearling spring smolts.
Unrein’s analysis 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 stated. “It is also present, although not as obvious, in steelhead trout.”
The research resulted from observations made throughout analysis 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.