Sunday, November 15, 2009

Protecting wild salmonids from releases of hatchery fish

The impact of releasing juvenile hatchery steelhead into streams on wild steelhead is one of the first effects of a hatchery program on wild salmonids. All the attention to the genetic effects of the hatchery program on wild salmonids is appropriate and necessary. However, the emphasis on it has been given more importance and attention than the effects of competition for space and food between the two types of steelhead. The first impact of a hatchery program is one of competition and displacement of rearing wild fish.

A study of juvenile salmonid behavior by Hillman and Mullan in 1989 shows that downstream migration of salmonid smolts pulled wild steelhead downstream with them and exposed them to higher predation rates. Their name for this is the “pied-piper effect.”

Ten years later McMichael et al. (1999a) recommended releasing hatchery juveniles that are smaller than wild fish in order to minimize their impact because the larger hatchery steelhead dominated the smaller wild fish.

McMichael et al. (1999b) said, “Hatchery steelhead displaced wild steelhead in 79% of the contests observed between these groups. Our results indicate that the behavior of hatchery steelhead can pose risks to pre-existing wild steelhead where the two interact. Strategies to minimize undesirable risks associated with behavior of released hatchery steelhead should be addressed if protection and restoration of wild steelhead stocks is the management goal.” (emphasis added) Apparently protecting wild salmonids is optional.

In those situations where hatchery steelhead are released at a larger size than the wild steelhead in the stream, the agency releasing them is obviously not concerned with protecting wild steelhead. It is unlikely that this research has gained much traction in hatchery management decisions because the managers have concluded that by releasing large steelhead smolts survival is increased. I am not aware of any evaluation that determines how many wild steelhead populations are affected by this practice. Given the emphasis on hatchery production in Oregon, Washington, Idaho and California, it would be surprising if any hatchery program is managed to reduce competition and protect wild juvenile steelhead in streams where these hatchery fish are released.

McMichael concludes by saying, “Acknowledging that releases of hatchery salmonids may affect pre-existing wild salmonid populations is an important step toward protection and recovery of imperiled populations of wild anadromous salmonids. Thorough evaluation of rigorous monitoring programs should be required in watersheds where depressed stocks of wild salmonids occur, even though these precautions will not ensure that wild stocks are protected or restored.”

This research was conducted on a Washington state stream, so if one were to apply a requirement to protect distressed stocks of wild salmonids in this state it would mean that of the 435 wild salmonid stocks in Washington, 134 (31%) are imperiled, needing protection. By following McMichael’s advice, these distressed wild stocks would be further harmed by the state’s hatchery practices. Since the status of 113 stocks is unknown (26%) a precautionary approach to hatchery practices would be in effect on 57% of the wild salmonid stocks making an impressive effort to do a better job of protecting 247 wild populations in Washington. But don’t hold your breath.


Hillman, T.W., and J.W. Mullan. 1989. Effects of hatchery releases on the abundance and behavior of wild juvenile salmonids. Pages 265-285 in D.W. Chapman Consultants, editors. Summer and winter ecology of juvenile chinook salmon and steelhead trout in the Wenatchee River, Washington. Report of D.W. Chapman Consultants, Boise, Idaho, to Chelan County Public Utilities District, Wenatchee, Washington.

McMichael, G.A., T.N. Pearsons, and S.A. Leider. 1999a. Minimizing ecological impacts of hatchery reared juvenile steelhead trout on wild salmonids in a Yakima basin watershed. Pages 365-380 in E.E. Knudsen, C.R. Steward, D.D. MacDonald, J.E. Williams, and D.W. Reiser. Sustainable fisheries management: balancing the conservation, and use of Pacific salmon. CRC Press, Boca Raton, Florida.

McMichael, G. A., T.N. Pearsons, and S.A. Leider. 1999b. Behavioral interactions among hatchery-reared steelhead smolts and wild Oncorhynchus mykiss in natural streams. North American Journal of Fisheries Management. 19:948-956.

Washington Department of Fish and Wildlife. 1992. Salmon and steelhead stock inventory. Olympia, Washington.

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