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The Importance of Resident Steelhead (Rainbow Trout), Oncorhynchus mykiss, in the Recovery, Productivity, Genetics and Population Viability of Anadromous Steelhead in Washington: The need to fully protect this life history form in anadromous rivers from harvest and incidental mortality with recommendations for WDFW rule changes.

Category: Newsletter Articles | Posted by: Jonathan | 1/6/12 | Comments: 0

Summary: The Wild Steelhead Coalition recommends that all resident steelhead in anadromous rivers be protected from harvest and incidental mortalities. This protection will further the recovery of badly depleted and ESA listed anadromous steelhead stocks in Western Washington.
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rainbow trout
Rainbow Trout (photo US EPA)

 by Dick Burge                                  

 Introduction

 Rainbow trout are resident steelhead and have been shown by many research studies to be important in the spawning, genetics, population viability and recovery of wild anadromous steelhead.  Resident steelhead spawn with anadromous steelhead throughout their range.  Male resident steelhead either augment spent-anadromous males using sneak tactics or replace them during the late winter run.  Studies have shown that 20 to 40% of returning anadromous steelhead have at least one resident parent and often have two.

Anadromous steelhead produce fish that stay in the river and become resident steelhead, and resident steelhead produce fish that go to sea and become anadromous steelhead.  Each form (resident and anadromous) is dependent on the other for productivity, gene flow and viability.  In rivers where the anadromous population is ESA listed or depleted, or in a long term decline, resident steelhead can play an important role in the recovery and rebuilding of the anadromous population.  Fishing for resident steelhead with a 14” size limit removes valuable spawners and causes a high mortality rate on released juvenile anadromous and resident steelhead which may be as high as 35%.

 The Wild Steelhead Coalition recommends that all resident steelhead in anadromous rivers be protected from harvest and incidental mortalities. This protection will further the recovery of badly depleted and ESA listed anadromous steelhead stocks in Western Washington.  Additionally, it will assist in the rebuilding of stocks and their long term maintenance in the non-listed rivers.  Most of those stocks are in decline and under increasing fishing pressure from fishers displaced by closures of their home rivers.    We recommend the elimination of all harvest of resident steelhead in all in anadromous rivers in Western Washington and the use of selective gear for all trout all fisheries to reduce hooking-induced mortalities.

 

COMMENTS on the WDFW Proposed Regulations for Rainbow Trout

Anadromous steelhead and rainbow trout are sympatric forms of the same the same species, Oncorhynchus mykiss (Behnke, 2002); they occupy the same riverine area and breed together without any loss of identity.  Other names for the rainbow trout that better describe this life history form are resident steelhead and steelhead trout.  The resident steelhead is a life history phenotype form of O. mykiss that is produced by both resident and anadromous steelhead.  Whenever agencies and sport fishers discuss management of the resident form, whether it is called rainbow trout or resident steelhead, it should always recognize that they are referring to resident steelhead.

In Washington rivers, anadromous wild steelhead juveniles smolt and go to sea in one to three years; however, many also residualize and spend their life in their natal rivers.  Using otolith microchemistry, 43 to 70% of resident steelhead in the Columbia River were found to have had anadromous mothers (Carmichael (RSRP) 2004; Carmichael et al. 2005) and Marshall found 37.5% of the lower Cedar River resident adults came from anadromous fish.   Zimmerman and Reeves (2000) found similar results in the Babine River in British Columbia.   These residualized steelhead fry become members of the resident steelhead population and mix and mate with other resident adults.

Resident steelhead sexually mature during their first or second year in the river and the males also mate with anadromous female steelhead, especially during the April through June spawning period when anadromous male steelhead have become less available and reproductively depleted from multiple earlier matings (McMillan et al. 2007).    Many observations have been reported of resident and anadromous steelhead mating including McMillan et al.  (2007) for the Sol Duc River, Kostow  (2003) for many tributaries to the Columbia River, Shapovalov and Taft (1954) in Waddell Creek, California,  and in the Cedar River, Washington by Foley (2005).  It is the later spawning time when resident males increase in importance for the mating and fertilization of anadromous female eggs.  Even when anadromous males are still spawning, the smaller resident male is successful using sneak tactics to fertilize anadromous female eggs (McMillan et al.,  2007). This interaction between the two forms is an evolutionary survival adaption that assures most anadromous female steelhead are fertilized and that the stock productivity, diversity, and genetics are maintained.

Anadromous steelhead are generally female biased in Washington and Oregon based on studies in coastal rivers and Columbia tributaries where they have been studied, and the resident population is male biased (Christie and McMillan, 2011; Kostow, 2003; McMillan et al. 2007).   In rivers on the Kamchatka Peninsula, Russia, Savvaitova et al. (1997) described a single inter-breeding population consisting of a female dominated steelhead form and a male dominated resident form.  This adaption undoubtedly helps provide more fertilized eggs to the spawning gravels than what would be expected from equal sex ratios.

Research has shown the resident steelhead is either genetically identical or very similar to the anadromous steelhead in a specific watershed.   The resident form also has a stronger genetic affinity to steelhead in its natal river than it does to the same life history type in another drainage (McCuster et al., 2000; Wapples et al., 2001).   This indicates that the resident form has evolved from the anadromous form independently many times within the species (Busby et al., 1996).

Recent genetic studies and Sr/Ca analysis of otoliths have further defined the mating and gene flow relationship and connectiveness between the two forms and shown that at least 20% of anadromous adults, and often more, result from matings that include at least one resident parent (Payne 2005).   A recent genetic analysis of the Hood River, Oregon, found 40% of the returning anadromous steelhead had resident steelhead genes (Christie et al., 2011); 20% had one resident parent and 20% had two resident parents.   A study at the Snow Creek Research Station in Washington found 39% of the juvenile steelhead did not have two anadromous parents (Seamons et al., 2004).  Carmichael et al. (2005) found 27% to 33% of returning anadromous adults in the Grande Ronde River had resident mothers and 43% to 70% of resident adults were produced by anadromous mothers.   Marshall et al. (2005) found 25% of the Cedar River smolts came from parents of the resident population and 5-16% of the returning steelhead had resident parents.  Clearly, an anadromous steelhead may be produced by the spawning of two resident adults, a resident and an anadromous adult or by two anadromous fish. This gene flow should remain continuous from generation to generation between steelhead forms as it is critical in maintaining population abundance and genetic diversity.  These research findings amongst others show the connectivenes of the two forms of steelhead in terms of genetics, reproduction, and in producing both life history forms that will be temporarily separated (riverine and oceanic life periods) in both time and space during part of their lifetimes.

From the studies cited, a clearer understanding of this polymorphic species has emerged: resident steelhead provide a necessary reproductive and genetic contribution to anadromous steelhead populations.  This should not come as a surprise as they are a single species comprised of two sympatric forms. Observations from rivers in California further demonstrate that resident steelhead can assist in the recovery of near-extinct steelhead populations (Osprey Staff 2000 and 2001); and WDFW noted the importance of this form in restoring the depleted native steelhead stock in the Cedar River (Marshall et al., 2004).  Steelhead planted in a lake in Alaska continued to produce sea going progeny with a 76% migratory rate after separation from their natal river for 70 years (Thrower et al., 2004) even though access back to the lake was blocked by in-river falls.  Clearly, every steelhead, resident and anadromous, has been shown to be important to the wild steelhead spawning populations; to improve the chances for the recovery of rivers of the ESA listed DPS’s and to improve the maintenance of the heavily fished non-listed populations.  Reducing or depleting resident steelhead populations removes critically needed spawners and reduces the viability of anadromous steelhead populations.

Resident steelhead and juvenile steelhead move up and down rivers in response to river flows, habitat needs, sexual attractions and food.  They may move from one main stem area or one tributary to another to satisfy their needs for rearing habitats (J. McMillan, personal observations in the Quillayute River system).  Resident steelhead have been found to move from their summer and fall habitats in upper portions of the rivers to lower river areas to locate and spawn with anadromous steelhead (McMillan, et al., 2007).  This would indicate that protecting resident steelhead in one area, such as in tributaries, and allowing for harvest in another area, such as main stem areas, may only protect resident steelhead for a limited time from harvest.

WDFW does not have the financial resources to obtain population information such as abundance or size distribution to manage wild resident steelhead in Washington rivers.  Catch data is also generally missing; hence there is no information to open a harvest fishery on resident steelhead and assure the population remains healthy.   This information should be a basic requirement for a harvest fishery of resident steelhead to assure an adequate spawning population for resident and anadromous fish populations after any planned harvest.

Rainbow Trout
Rainbow Trout (photo by Gary Martson)

Rivers of Puget Sound are ESA listed for wild steelhead and their populations are now at extremely low abundance levels of anadromous steelhead and at about 2% of their historical numbers.  In fact, many of these rivers such as the Puyallup (2010/11 escapement was 329 fish), the Nisqually (2010/11 escapement was 268 fish), the Cedar (now appears extinct) and the Green (2010/11 escapement was 855 fish) may now be at, or very near, functional extinction and biologically incapable of self-recovery as described by Wright (2004a, 2004b) in the petition for listing the Puget Sound Steelhead DPS.

 

Recommendations to WDFW for the 2011/12 rules proposals

 Every steelhead, resident and anadromous, should be protected from fishing mortality to take part in the recovery and/or maintenance of wild stocks.  Even where the size limit for resident steelhead (rainbow trout) has been set at 14-inches, anglers using bait and lures and barbed hooks cause a high hooking mortality of juvenile (pre anadromous) steelhead and resident steelhead smaller than 14”.  Mortality rates of hooked and released trout, in general, has been recorded at much higher levels than that of adult steelhead, often as high as 35% (Trotter, 1995).

The harvest of a resident steelhead (rainbow trout) is the same as harvesting a wild anadromous steelhead; they are both necessary components and genetic resources of the steelhead spawning population.  Given that the WDFW allows only one wild anadromous steelhead to be harvested per angler each year, this rule should be applied to the resident steelhead (rainbow trout) as well in anadromous rivers.  In Washington state,  where most Steelhead Distinct Population Units (DPS’s) are ESA listed (5 out of 7) and the remaining two areas are experiencing both population declines and increasing fishing pressures, every wild resident steelhead should be protected.

To protect both life history forms of wild steelhead (resident and anadromous), the Wild Steelhead Coalition recommends the following:

  1.  The maximum limit for wild steelhead, anadromous and resident, in combination, should be either 0 or 1 fish per year.  It would be management and biologically correct to fully protect resident steelhead (rainbow trout) as many will still be lost to hooking mortality during trout and salmon fisheries; and to retain the one fish harvest for the anadromous steelhead.
  2. Allow only selective gear for all trout fisheries in anadromous sections of Puget Sound and Coastal Washington and do not allow hooked fish to be removed from the water for any reason.

 

References cited>

 

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