Natural Reproductive Success of First-generation Hatchery Steelhead Spawning in the Kalama River: A Progress Report

Hatchery-produced anadromous salmonids return to their rivers of release and some of them spawn, or attempt to spawn, among themselves and with native conspecifics in natural habitats. The nature and degree of the interactions between the hatchery and wild fish is of considerable concern because of the potential for those interactions to pose genetic and ecological risks to the extant wild populations (Waples 1991; Hindar et al. 1991; Busack and Currens 1995; McMichael et al. 1997; Ford 2002; Kostow et al. 2003; Araki et al. 2008).

The use of local wild-origin broodstocks in hatchery programs has received considerable attention by WDFW (e.g., 21st Century Salmon and Steelhead Initiative (WDFW 2009)) and other agencies responsible for fish management in the Pacific Northwest. Wild broodstocks are increasingly being used or recommended for use in supplementation applications (intended to increase natural production of depressed stocks) and also in harvest augmentation applications (intended to provide harvest opportunity). Current theory indicates that genetic risks to wild populations might be contained if the degree of genetic similarity between hatchery and wild stocks is high (e.g. Krueger et al. 1981; Allendorf and Ryman 1987; Fleming and Gross 1993). The presumption is that hatchery programs based upon or integrating locally adapted wild fish as broodstock would pose the least risk to wild populations. Alternatively, interbreeding between wild fish and fish domesticated for any number of generations may pose an unacceptable level of risk by causing shifts in genetically based performance traits and reducing survival in natural environments (Reisenbichler 1999, Araki et al. 2007).

The goal of the Kalama research program is to identify and empirically quantify risks imposed by hatchery programs on natural production of anadromous salmonids, and identify strategies to manage those risks. Studies of steelhead genetics, ecology, and life history have been ongoing in the Kalama River since the mid-1970's. A primary objective of Kalama research work has been to assess the relative reproductive performance and contribution of hatchery and wild steelhead spawning in the wild. For the purposes of this report, wild fish are defined as naturally produced fish, regardless of ancestry, and hatchery fish are those spawned and reared for some portion of their life in the hatchery environment. Earlier Kalama work focused on evaluating reproductive competence of highly domesticated, non-locally derived hatchery fish. The primary objective was to assess the reproductive performance of these hatchery fish relative to wild steelhead spawning in the wild. That work showed that highly domesticated steelhead of non-local origin (both summer and winter races) exhibited much lower natural reproductive success in the Kalama River than sympatric wild fish (Chilcote et al.1986; Leider et al. 1990; Hulett et al. 1996), an outcome supported by work in other watersheds (Araki et al. 2006, Mclean et al. 2003, Kostow et al. 2003).

The objective of the current Kalama research effort is focused upon estimating reproductive success of first-generation wild broodstock hatchery summer-run steelhead that were passed upstream to spawn among an approximately equal number of wild steelhead in 2003, 2004, and 2005. These brood years are our three experimental replicates. Most returning steelhead from natural production in those brood years have been, or will be, genetically sampled in 2007, 2008, and 2009. Anadromous offspring that returned in run year 2007 have been pedigreed back to their hatchery and wild parents. This document provides results of this first replicate of the experiment: comparison of production of anadromous adults from wild broodstock hatchery and wild steelhead spawning in 2003. A portion of the adult returns from the second replicate (2004) were also captured in run year 2007 and that portion of the results from the second replicate (adult returns from 2004 spawners) is also provided.