THE ABILITY OF RELEASED HATCHERY SALMONIDS TO CONTRIBUTE TO THE NATURAL PRODUCTIVITY OF WILD POPULATIONS

Fleming, Ian A. and Erik Petersson. 2001. Nordic J. Freshw. Res. 75:71-98.

ABSTRACT: The success and implications of hatchery release programmes are intimately tied to the reproductive capabilities of the hatchery fish in the wild. Moreover, reproductive interactions are important in understanding the ecological and genetic threats that hatchery fish may pose to wild populations. Reproductive success is a key to self-sustainability, shaping natural and sexual selection, and influencing the genetic diversity of populations and the implications of parental traits and decisions for offspring survival and success. We then address how rearing and release programmes affect the reproductive traits and performance of fish. A review of such programmes reveals that in the few cases where adequate assessments have been made released fish frequently fail to attain self-sustainability and/or contribute significantly to populations. Clearly, new approaches based on sound scientific research are needed and these need to be tailored specifically to the management objectives.

EVALUATION OF HATCHBOX FRY RELEASE PROGRAM

Solazzi, M.F., T.E. Nickelson, S.L. Johnson, and J.D. Rogers. 1998. Project Number: F-125-R-13. Oregon Department of Fish and Wildlife, Portland, Oregon.

INTRODUCTION Historical Background and Rationale For Hatchboxes:

The use of coho salmon hatchery fry and fingerling to supplement wild populations has a long history in Oregon coastal streams. However, the evaluation of the success of these programs has been problematic, at best.
Juvenile coho salmon have been released into Oregon streams and rivers since about 1890. Until 1910, all the fish released were unfed fry. Beginning in about 1910 an experiment was set up at Central Hatchery (now Bonneville) to evaluate the effects of pond rearing the fry to a larger size prior to release. Returns of adult fish between 1914 and 1919 were at or near historical levels suggesting that the new rearing strategy was successful. The first coastal releases began about 1890 by R.D. Hume on the Rogue River. His self-proclaimed success led to the development of 10 coastal hatcheries or egg taking stations by 1915. By 1938, over 30 million coho salmon fingerlings and fry were being released into Oregon coastal streams.
By the early 1940s, the first smolt releases (fish larger than 25 fish per pound) were beginning. As the number of smolts released began to increase the numbers of fry and fingerlings released began to decline. The major reason was that larger fish were shown to survive better than fingerlings or fry. Other reasons cited include a major advancement in disease control (pasteurized feed), nutrition, better broodstock development and improved hatchery practices.
During the 1960s and 1970s, the number of adults spawned exceeded the capacity of the available hatchery rearing space, and the excess offspring were released as unfed fry. During this period, the first attempt to evaluate the success of the fry-stocking program was completed. An analysis of the relationship between hatchery coho salmon fry releases and adult escapement (McGie 1980) for the 1961 through 1971 broods, suggested that the release of fry “had no measurable influence on adult escapement.” Fry and fingerling releases subsequently began to decline.
In the early 1980s, a legislatively directed program of presmolt (2000/lb.) releases was initiated. An evaluation of this program (Nickelson et al. 1986) suggested that the increased number of fish released did not result in increased production of adults in streams where the fingerlings were stocked. Because of this evaluation and decreased numbers of excess adult fish returning to coastal hatcheries the number of fry and fingerlings released in recent years has declined.
The Oregon Department of Fish and Wildlife began using hatchboxes on a large scale beginning in 1981 with the creation of the Salmon and Trout Enhancement Program (STEP). This program was begun under legislative directive (ORS 496.430 to 496.460). The goal of the STEP program is to restore native stocks of salmon and trout to their historic levels of abundance. One of the techniques used to achieve this goal has been the use of volunteers to raise excess eggs in hatchboxes. ...The unfed fry are then released directly from hatchboxes or transported and released into local streams and rivers in an attempt to bolster depressed stocks. Approval by the Department of Fish and Wildlife for volunteers to obtain eggs from state hatcheries to incubate in hatchboxes is administered under OAR 635-09-090 to 635-09-140. Section one of this rule states that “all projects must comply with fish management goals and objectives as set forth in OAR 635-070-501 through 635-07-830, and species and/or area management plans adopted by the Commission.” It further states that a project will NOT be approved if it is not based on sound biological principles and is not supported by physical and biological stream survey information or if it proposes to use inappropriate methods to accomplish the project objectives.
The Oregon Department of Fish and Wildlife will support the use of hatchboxes only in certain areas and under certain specific conditions. The areas where hatchboxes are most likely to be appropriate are streams historically inhabited by the juvenile fish of the species of interest, but where they are not now present. In some cases, hatchboxes are used in areas above artificial barriers that block passage of adult salmonids. Hatchboxes may be used to supplement existing populations only if information from a physical and biological survey of the stream suggests that the local population is extremely depressed and that there is sufficient habitat available to support the hatchbox fry without having a detrimental effect on the local population. Except for small projects that focus on education, releases into a stream is limited to one life cycle of the species. Hatchboxes are an inappropriate tool in areas where the available rearing habitat is already fully occupied by juvenile salmonids, or where the appropriate egg source (brood stock) is not available.
Social interactions between hatchbox fry and native wild fry generally result in displacement of the hatchbox fry into marginal habitats where survival is low, however, some wild fry are also displaced. Evaluations of salmon fingerling releases...suggest that the release of large numbers of fingerlings and fry into coastal streams does not result in increased adult production. Nickelson et al. (1986) documented a detrimental impact on wild adult coho salmon production from fingerling releases, partly because of the use of an inappropriate broodstock that spawned too early.

STEP HATCHBOX EVALUATION
During the early 1980s, we evaluated the effectiveness of using hatchery presmolts to rehabilitate naturally spawning coho salmon populations in coastal streams (Nickelson 1981; Niclelson et al. 1986; Solazzi et al. 1983, 1990). We found that the numbers of juvenile wild coho salmon were reduced in streams stocked with hatchery presmolts. We also found that, although the total number of spanwers in stocked and unstocked streams were similar in the years that the hatchery fish returned, the late-spawning wild adults in the stocked streams were 50% less abundant than in the unstocked streams. We concluded that the hatchery presmolts reduced the wild populations through competition and that the early returning hatchery fish failed to contribute significant numbers of offspring to the next generation. Two factors contributed to this result: 1) early spawning time of the hatchery broodstock, and 2) large size of the presmolts relative to wild fish.
The purpose of the STEP hatchbox evaluation program was to evaluate the effectiveness of coho salmon fry that result from late spawning broodstock incubated in STEP hatchboxes, to rehabilitate wild populations of coho salmon...

RESULTS AND DISCUSSION
Adult Abundance:
The number of adult coho salmon returning to the study streams during 1985-1987 was not significantly different between the treatment and reference streams. Because there was no difference in adult abundance between the reference and control streams, any differences in juvenile abundance should be due to the effects of stocking the hatchbox fry.
Juvenile Density:
We did not find an increase in juvenile coho salmon density as a result of stocking hatchbox fry for two years in the six study streams.
Results from sampling juvenile coho abundance and outmigration suggest that the hatchbox program was not effective at increasing the rearing density of juvenile coho salmon in the treatment streams. Our estimates suggest that 13% to 26% of the juvenile coho salmon fry stock in Oxbow Creek migrated our of the stream within four days after stocked.

SUMMARY
There is little argument that good artificial incubation techniques can have egg-to-fry survival rates of well over 95%, a significant increase over values reported for naturally incubated eggs. However, there is little evidence that egg-to-fry survival rates are limiting the adult production of most salmonid fishes. (emphasis added) One exception to this may be with chum salmon, which migrate into salt-water almost immediately after emerging from the gravel. For salmonid species with extended freshwater rearing (coho, steelhead, cutthroat, and some chinook stocks) factors other than egg to fry survival rate are probably more important in determining adult production levels. Recent studies by Nickelson et al. (1992) for coho salmon in Oregon coastal streams suggest that winter habitat may often be the limiting factor in the freshwater environment, especially for juvenile coho salmon.

REPRODUCTIVE SUCCESS IN THE WILD

Andrew Hendry, John Wenburg, Eric Volk, and Thomas Quinn. 1999. American Society of Ichthyologists and Herpetologists AnnualMeeting 1999.Organized by Andrew Hendry and Drew Hoysak.

ABASTRACT We demonstrate that sockeye salmon populations can exchange many migrants each generation and yet remain genetically distinct, owing to reduced reproductive success in strays. We studied a small beach population that receives strays each generation from a much larger river population (both in Lake Washington, Washington). Site-specific otolith microstructure patterns were used to determine which beach spawners had been born at the beach (residents) and which had been born in the river (strays). In each of two years, about 1% of the river population strayed to the beach but these strays composed 35 - 44% of the beach spawners. If strays and residents had similar reproductive success, such levels of gene flow would prevent any neutral genetic divergence of the populations. However, allelic variation at microsatellite loci revealed that beach residents were distinct from the river population and from river fish that strayed to the beach. Strays were morphologically similar to river fish but quite different from beach fish, suggesting that local adaptation may play a role in their reduced success at the beach. Local adaptation of residents and declining success of strays can arise early in a population’s history (the beach site was colonized less than 14 generations ago).

NATURAL EPRODUCTIVE SUCCESS OF HATCHERY AND WILD STEELHEAD IN THE KALAMA RIVER

Patrick Hulett, Cameron Sharpe, and Chris Wagemann . 1999. Society of Ichthyologists and Herpetologists AnnualMeeting 1999.Organized by Andrew Hendry and Drew Hoysak.
ABSTRACT: Allozyme genetic marking approaches were used in two long-term studies to estimate the reproductive success of non-locally derived stocks of hatchery summer and hatchery winter steelhead spawning naturally in the Kalama River. Results of the winter-run study corroborate those previously published from the summer-run study. Reproductive success (offspring produced per spawner) of the hatchery steelhead was substantially lower than that of the wild fish. Also, the disparity in reproductive success was increasingly pronounced at successive (subyearling, smolt, and adult) life history stages of the offspring. These results are believed to reflect genetic differences between the wild and non-local hatchery stocks. Because their natural spawning poses genetic and ecological risks to wild steelhead, the non-local hatchery adults are no longer permitted access to principal wild Kalama steelhead spawning areas. Moreover, new research has been initiated to assess the wild stock conservation merits of using locally derived wild broodstock as a source for hatchery steelhead production. Specifically, the reproductive success of hatchery-reared steelhead spawned from wild Kalama summer-run broodstock will be compared to that of their wild-reared counterparts by relating microsatellite DNA profiles of naturally produced offspring to those of their prospective hatchery and wild parents.

HATCHERY-WILD INTERACTIONS

Mart Gross, Bryan Neff, and Ian Fleming.1999. American Society of Ichthyologists and Herpetologists AnnualMeeting 1999.Organized by Andrew Hendry and Drew Hoysak.
ABSTRACT: Although salmon supplementation and conservation programs often use hatchery fish, there is a lack of empirical knowledge about their behaviour, ecology and reproductive success in the wild. We now present the results of several experiments in which we studied their behaviour and ecology and quantified their reproductive success. Both wild and hatchery coho salmon were allowed to freely breed within a spawning channel in the wild. The behaviors and interactions of the fish were recorded and after all spawning had been completed we collected the alevins from the nests. Using microsatellite genetic markers, we determined the parentage, including maternity and paternity, of the fish. Several important relationships emerged, including that between male position in the mating hierarchy and paternity, between male size and reproductive success, between stock type (hatchery or wild) and paternity, and between mating partner and success. Overall, hatchery males attended fewer mating hierarchies, obtained lower paternity within a position, and made up only about a third of the male contribution to the next generation. Hatchery females were also significantly less successful than wild females. Hatchery fish were therefore relatively maladapted and decreased the wild population’s effective population size. Finally, our measures of reproductive success within hierarchies may be widely applicable to studies of salmon in the field. This research is supported by NSERC and DFO of Canada, and NINA of Norway.