Colonization of a Watershed by Anadromous Salmonids following the Installation of a Fish Ladder in Margaret Creek, Southeast Alaska

Abstract

We evaluated the colonization of a watershed blocked by a 7-m falls following the installation of an Alaska steeppass fish ladder to provide access for anadromous salmonids. Coho salmon Oncorhynchus kisutch, pink salmon O. gorbuscha, and chum salmon O. keta were present below the falls. Fry of sockeye salmon O. nerka were stocked into Margaret Lake once in 1988 and annually from 1990 through 1994. Pink salmon were the most numerous species to colonize habitat above the falls. Coho salmon moved up the ladder during all years. However, progeny from 25,000 coho salmon presmolts that were stocked in 1991 were the greatest proportion of the returns in 1992, 1995, and 1996. During the study, only 1,595 sockeye salmon returned from more than 1.4 million that were stocked. The rapidity of colonization by naturally occurring anadromous salmonids, including cutthroat trout O. clarki, Dolly Varden Salvelinus malma, and steelhead O. mykiss, underscores a life history strategy of exploiting newly accessible habitat as it becomes available. Although anadromous salmonids successfully colonized the watershed, effects of interbreeding among stocked and natural runs of coho salmon may not be observed for several generations.

Notes

³ Draft Forest Plan for the Tongass National Forest, Appendix H, U.S. Forest Service, Region 10, Juneau, Alaska.