Resident rainbow trout produce anadromous offspring in a large interior watershed

Abstract

Rainbow trout (Oncorhynchus mykiss) have diverse life histories, including both freshwater-resident and anadromous “steelhead” life-history forms. Here, we demonstrate that female resident rainbow trout produce anadromous offspring that survive and return to spawn as adult steelhead. This study represents the first successful attempt to quantify steelhead production rates from female resident rainbow trout across a large watershed. Otolith microchemistry (87Sr/86Sr) techniques were used to determine the maternal life history (resident or anadromous) of 498 emigrating steelhead kelts in the Yakima Basin, Washington. Five geochemically distinct freshwater rearing regions were identified within the basin. All five regions were predicted to produce steelhead with resident maternal life histories. Basin-wide, 20% and 7% of steelhead collected in 2010 and 2011, respectively, had resident maternal life histories. Cross-life-history form production may be critical to persistence of anadromous life histories within partially anadromous salmonid populations, particularly in areas where anadromous fish abundance is low due to natural or anthropogenic influences.

Anadromy and residency in steelhead and rainbow trout (Oncorhynchus mykiss): a review of the processes and patterns

“…Likewise, freshwater maturation persists in many, if not all, hatchery steelhead trout stocks after decades of selectively breeding only anadromous adults (Christie et al 2011;Sharpe et al 2007;Sloat and Reeves 2014). Otolith microchemistry revealed that anadromous kelts in the Yakima River basin, Washington, had resident mothers 7% and 20% of the time in each of 2 years of study (Courter et al 2013). Similar observations of residents producing anadromous offspring have been documented in other populations (Zimmerman et al 2009;Zimmerman and Reeves 2000), in addition to female steelhead producing resident offspring .…”

“…On the other hand, only two studies estimated heritability within the context of anadromy and residency (h 2 = 0.44-0.56 and H 2 = 0.69-0.77, respectively) (Doctor et al 2014;. Although the studies provide evidence of a heritable component to O. mykiss life histories and for traits related to individual condition (e.g., body growth), they also demonstrate that individuals are not necessarily precluded by parentage from expressing alternative life histories (e.g., Christie et al 2011;Courter et al 2013;Zimmerman and Reeves 2000).…”

“…However, few studies explicitly examined the extent of heritability associated with anadromy and residency in O. mykiss (Table 2). For instance, several studies estimated the proportion of anadromous offspring produced by anadromous and resident parents (Berejikian et al 2013;Christie et al 2011;Courter et al 2013;Hayes et al 2012;Ruzycki et al 2009;Seamons et al 2004). On the other hand, only two studies estimated heritability within the context of anadromy and residency (h 2 = 0.44-0.56 and H 2 = 0.69-0.77, respectively) (Doctor et al 2014;.…”

“…"Steelhead" and "rainbow trout" are the common North American names for anadromous and freshwater resident life history forms of O. mykiss, respectively, whereas both forms are known as "mykizha" in Russia. Anadromous and resident forms are often sympatric, commonly interbreed, and their offspring may adopt either form (Christie et al 2011;Courter et al 2013;Sloat and Reeves 2014). The balance of life histories can vary, with some populations supporting more residents and others more anadromous individuals (e.g., .…”

“…For example, greater life history diversity in O. mykiss spreads mortality risk over space and time, thereby dampening population fluctuations and increasing resiliency to environmental variability (Moore et al 2014). Further, resident males mating with anadromous females (McMillan et al 2007) and the contribution of anadromous offspring from residents and vice-versa (Christie et al 2011;Courter et al 2013;Sloat and Reeves 2014) offer important avenues for buffering genetic and demographic stochasticity that are much less available to other Pacific salmonines . Declines in the anadromous component of O. mykiss populations in the United States, Canada, and Russia have motivated an increased interest in exploring the factors shaping anadromy and residency, especially as changing climate conditions and anthropogenic activities alter the fitness of these different forms (Benjamin et al 2013;Satterthwaite et al 2010).…”