Marine Fish Enhancement as a Critical Component of Puget Sound Restoration

(01/01/2010)

Marine Fish Enhancement as a Critical Component of Puget Sound Restoration

Conserving and Restoring Biodiversity, MES Fall 2006


Introduction

Washington State is engaged in numerous efforts to protect biodiversity, preserve habitat and restore the Puget Sound ecosystem. One important element in these proposals is being largely overlooked, the restoration of marine fish stocks to historical or sustainable levels. Because of their longer life cycle, age at reproduction, and fecundity based on size at spawning, recovery of marine fish solely by natural means will take decades. Continued impacts from human activities including projected population growth in the Puget Sound region will militate against natural recovery. Marine fish enhancement may be an important tool in restoring some of these depleted stocks more quickly, particularly before those most impaired drop below sustainable and recoverable levels. Intervention sooner may allow us to preserve and protect some critical sub-groups and allele frequencies that are the most threatened.

Many negative impacts of past enhancement efforts on wild stocks and their environment have been identified, particularly with salmon. However, recent modifications of practices, with the adoption of conservation hatchery methods, have reversed most of the trends in these impact areas. Using conservation hatchery methods and applying emerging artificial genetic marking techniques will allow us to understand, avoid and manage negative impacts of enhancement efforts on marine fish while facilitating quicker and more complete recovery of some of our most depleted stocks.

This paper will examine the negative impacts of past practices and the strategies that have been developed to avoid them. We will examine the potential for applying them to marine fish in Puget Sound and some of the best ways to proceed while avoiding potential problems as much as possible.


Current Puget Sound recovery efforts

Gov. Chris Gregoire of Washington State created the Puget Sound Partnership (PSP) on Dec. 19, 2005, as part of her Puget Sound Initiative. On its website the tasks it was charged with were listed as follows:

"Gov. Gregoire recruited the "best and the brightest" to join the Puget Sound Partnership to make high-level recommendations on a comprehensive effort for integrating the work of local, state and federal governments with private sector and citizen efforts to protect and restore the Sound.

The Puget Sound Partnership will learn and use what has worked at other large ecosystem protection efforts around the country, and will engage an extensive cross-section of Washington citizens, business and governments in recommending how to improve protection and recovery of Puget Sound and Hood Canal." (PSP, 2006)

A draft set of final recommendations was issued on Oct. 13, 2006. The report was titled "Restoring Puget Sound Ecosystem Health for Future Generations." (PSP, 2006)

The report made numerous recommendations about restoring and protecting marine, near-shore and upland habitat. It talked about aspects of public engagement and communications, governance structures, funding and science. It discussed pollution, oil spill prevention, the reduction of human waste and stormwater runoff. It highlighted the protection of biodiversity and the recovery of imperiled species with special emphasis on salmon recovery. Finally it emphasized the importance of public involvement, effective governance and funding.

Marine fish were mentioned specifically in only two places in the report, on page 2 with reference to marine fish habitat and in Appendix A. Ecosystem Goals, Outcomes, and Potential Benchmarks in table 1 under A.2.1, with regard to sustainable harvest levels. (PSP, 2006) This limited discussion of marine fish as separate from salmon seems short sited and could result in missed opportunities to monitor the health of the sound and restore this important element of the marine ecosystem. It assumes that habitat protection and restoration will solve most of the problems for marine fish. While it will certainly help reduce the deterioration of marine stocks, upland and shoreline development and urbanization will continue to have a deteriorating effect on marine habitat for generations to come. When we acknowledge that population in the Puget Sound Region will increase by 1 million more people in the next 20 years, further impacts should be anticipated.


Marine fish enhancement, should we or shouldn't we?

One important strategy to restore stocks of marine fish would be to engage in marine fish enhancement. Washington State has a long history of enhancement activities particularly with salmonids. Unfortunately, salmon enhancement was traditionally seen as an alternative to sustaining viable ecosystems and was employed for the sole purpose of providing harvestable fish. Over time, that approach was deemed to be marginally effective as it became apparent that it was having negative impacts on native salmon populations. With growing public awareness, the pendulum began to swing away from artificial propagation. Concurrent with the listing of 80 some species of native stocks of salmonids in the 1990's in Washington State, additional scrutiny was focused on public hatchery programs to determine if they were really a part of the problem instead of part of the solution. Since that time, many new facility designs and production protocols have been introduced into hatchery management to harmonize their efforts with wild stock recovery. As a result of these changes, much has been learned about new approaches to artificial propagation of salmon that could appropriately be applied in marine fish enhancement. If this approach is employed with marine fish it should be used in a limited and cautious strategy to gain research information about the species, their life cycles and their habitat.

Peer reviewed literature on marine fish enhancement is limited. Much of the information exists in grey literature an in conference reports. Never-the-less, we will take a look at some of the criticisms and concerns with existing enhancement efforts. One of the most important concerns is that marine fish enhancement may not be cost effective and that alternative such as habitat restoration and enforcement of harvest limits will achieve more with available resources. Three possible objective for marine fish enhancement suggested are (1) to replace extinct stocks of recreational or commercial purposes, (2) to rebuild depleted stocks, and (3) to augment existing but depleted stocks for recreational purposes ( Hilborn, 1998.) In order to evaluate the success of enhancement programs four steps are required. They are (1) estimating the number of reared fish that survive and contribute to the catch, (2) verifying that survival can be maintained for many generations, (3) estimating the extent to which the harvest can be managed without adverse impact on wild fish, and (4) estimating the biological interactions between reared an wild fish that may decrease net production by reducing numbers of wild fish ( Hilborn, 1998.)

Using these criteria Hilborn reviewed 11 different case studies of programs from around the world that were engaged in marine fish enhancement (including several salmonid programs.) Only one of these, the Japanese Chum salmon program, appears to be a clear economic success. Other programs were plagued by lack of critical evaluation efforts, had clear impacts on wild populations, or failed to demonstrate sufficient return on investment. He suggests that marking should be standard procedure for establishment of survival and that control areas should be the method for determination of net increase in abundance ( Hilborn, 1998.) Density dependence seems to be a major limiting factor in most marine fish enhancement programs. "It is widely observed in marine fish stocks that recruitment is largely independent of spawning stock size over a wide range of spawning stock sizes. This pattern implies strong density-dependent competition between individuals and that releasing additional small fish will not result in any net increase in production." ( Hilborn, 1998) He suggests that only two circumstances warrant such intervention. They are, when spawning stocks of natural fish are so low that density-dependence is not a factor and when release fish are reared above the size where density dependence is no longer a factor. In both cases over harvest of wild fish remains a major concern and reduced fishing pressure is always appropriate ( Hilborn, 1998.) Of course rearing fish to larger sizes and reduced harvest militate against the cost effectiveness of these programs. His major assertion is that we should "solve the problem. Don't tinker with the symptoms."

Genetic impact of any enhancement program is always a major concern. One interesting observation, when comparing salamonids to other marine fish is that non-salmonids are typically less differentiated genetically than fresh water fishes (Utter, 1998.) This is most likely the result of fewer impediments to movement in the marine environment. One the one hand, this may make it less likely that marine fish enhancement will have the potential for less genetic impact. On the other hand, it makes it much more difficult to detect modifications of the allele frequencies in resident stocks as a result of enhancement activities. It is important to use intentional genetic marking techniques to provide an opportunity to evaluate this impact on the first generation population and on subsequent generations. Numerous problems with changes in genetic variability can result from artificial propagation. These include translocation of stocks, over harvest of wild stocks, reduced genetic variability , inbreeding depression, behavior modification and genetic selection as a result of artificial propagation techniques, non-introgressive hybridization resulting in wastage of gametes and habitat, and introgressive erosion of population fitness through mating of genetically divergent individuals, i.e. out-breeding depression(Utter, 1998.)

To avoid these pitfalls to the greatest extent possible Utter suggests three requirements be included in any significant enhancement efforts. They include (1) Field studies to verify the existence and ecological parameters of natural populations, (2) laboratory studies to identify the geographic patterns of indigenous ancestral groupings and the presence of exogenous or introgressed populations resulting form introductions, and (3) determination of genetic and ecological relationships among hatchery, native and other naturally reproducing populations. He further states that "actual or potential cultured-wild interactions be preceded by preliminary evaluations and risk assessments from empirical observations as outlined in preceding text. A systematic and cautious approach to marine stock enhancement is therefore essential as empirical data accumulate. (Utter, 1998)

Much of the concern and skepticism about future marine fish enhancement activities stem form our past experience with salmon hatcheries and their impacts on wild stocks. Let us examine past hatchery practices and their evolution in recent years.


Traditional salmon hatchery production methods and their problems

The early development of salmon hatcheries by public agencies was centered on providing mitigation of public projects such as hydroelectric dams. Little attention was paid to the interaction of hatchery stocks with wild stocks. In some cases natural production was virtually eliminated by dams with little or now fish passage. As wild stock continued to decline from over harvest in mixed stock fisheries, lack of access to native spawning grounds and human impacts on the quality of the water and the habitat, more attention was paid to this interaction.

"Up to 5 billion fish have been release annually into the North Pacific" and "today the Columbia River has more than 100 artificial production facilities that release about 200 million hatchery fish. (Flagg, et. al. 2004) The primary purpose of the listing under the Endangered Species Act is to preserve biodiversity of wild stocks. Recognition that hatcheries were often impacting wild stocks negatively began earlier, but the listings under the ESA brought strong pressure to review hatchery management policies to reduce these impacts. Where hatcheries were in conflict with ESA listings, only two alternatives existed. (1) Isolation of hatchery production and (2) altering hatchery operations to include the conservation mandate (Flagg, et.al.2004).

Three major potential impacts of hatchery fish on wild populations were identified. They include (1) over harvest of wild stocks in mixed stock fisheries, (2) interaction between wild and hatchery fish such as competition, predation, and negative social interactions due to the much larger numbers of hatchery fish as compared to wild fish and (3) genetic risks such as domestication selections, inbreeding and out-breeding depression. (Flagg, et.al., 2004) Hatchery techniques often reduced the survival of hatchery fish because of the design of the rearing tanks which often did not condition the fish to natural flows regimes. Surface feeding methods conditioned the fish to swim towards large moving objects instead of avoiding them. This left them much more susceptible to predators in the natural environment. High survival rates from egg to smolt were viewed as a major success in the hatchery, while reproduction success of cultured fish were much lower than the wild cohorts.(Flagg, et.al., 2004) Thus interbreeding between hatchery and wild fish could actually reduce the number of wild alleles transferred to the next generation.

Feed availability, lack of incubation substrate, excess movement of alevins resulting in lower energy efficiency and reduced size, rearing densities, size and timing of release, altered coloration due to rearing pond conditions and many more ore mentioned in the literature as reasons for decrease survival of hatchery fish throughout their lifecycle.


The conservation hatchery concept, a new approach

The importance mimicking the rearing environment as much as possible to the natural conditions for any animal that will eventually be released into the wild has long been recognized by those involved in conservation. So to, it became apparent that salmon hatcheries need to change to accommodate this important principle. Three general principles were identified as necessary if hatchery production was going to become more compatible with natural production. They are (1) mimic the natural life history patterns, (2) improve the quality and survival of the hatchery reared juveniles, and (3) lessen the genetic and ecological impacts of hatchery releases on wild stocks (Flagg, et. al., 2004).

Near the top of the list of important issues are genetic considerations. "Conservation hatcheries should provide fish with minimal genetic divergence from their natural counterparts..." (Flagg, et. al., 2004). To this end, hatcheries should establish rearing protocols that minimize domestication, inbreeding and out-breeding. "They should also release fish that have the same fitness and diversity characteristics of their wild cohorts." (Flagg, et. al., 2004). Spawning protocols to achieve these goals include random pairing, avoidance of pairing siblings, crossing different year classes and use of cryo-preserved sperm from other year classes. (Flagg, et. al., 2004).

Conservation hatcheries should use locally adapted broodstocks to the greatest extent possible. Elements of this program should include careful consideration of environmental relationships and life history and integration of wild fish into the hatchery population to avoid divergence.. Captive broodstock for severely depleted stocks should be considered with new generations of eggs coming from wild cohorts. (Flagg, et. al., 2004).

Incubation and rearing containers should have colors and complexity to insure that hatchery populations mimic the appearance of wild stocks. Low Rearing density as well as growth patterns and size at release are also important. Feeding techniques that enhance bottom feeding activities using diets with natural feeds should be employed. Anti-predation training exercises should be conducted to condition the fish for better avoidance responses in the natural environment. (Flagg, et. al., 2004).

Reintroduction strategies should mimic the natural migratory patterns of the wild population to the greatest extent possible. This includes time of release, population size variability, the use of volitional out migration regimes, and practices that enhance homing and imprinting on the water source at the point of release. (Flagg, et. al., 2004).

By employing these and other elements of the conservation hatchery approach artificial propagation has been shown to increase the survival of hatchery fish and reduce the impact of hatcheries on wild stocks. Exact application of these techniques vary from facility to facility depending on stock interactions and available resources to achieve the stated goals. (Flagg, et. al., 2004).


Opportunities for maine fish enhancement in Puget Sound

In considering any program for marine fish enhancement many of the principles listed above will apply and should be anticipated in hatchery designs and rigorously applied in all hatchery protocols and rearing regimes. One of the biggest historical impacts of salmon hatcheries came from the high numbers they released in comparison to the numbers remaining in the native populations. The high numbers of hatchery fish often overwhelmed the native runs with predation, competition and inbreeding. Another important element was the harvest of mixed stock fisheries to the detriment of the wild stocks.

Some question the need for marine fish enhancement with current stock levels in Puget Sound. There are a variety of opinions about which stocks are depleted, how severe that depletion is, and whether habitat restoration and preservation will return stocks to near historic levels. Is a regulating harvest and habitat restoration all or most of the answer and will artificial propagation simply make matters worse as it has in many cases with salmon. I believe there are good arguments to at least consider marine fish enhancement. Nearly everyone agrees that significant levels of depletion exist and that in some cases it is severe.

The following are quotes from various sources about the status of marine fish in Puget Sound:

"Some rockfish populations are down 90 percent from their historic levels" and "Of the 19 herring stocks in Puget Sound, one is depressed and two are in critical decline. Because herring are food for so many species, any decline sends repercussions throughout the Puget Sound food web." (State of the Sound Report - Puget Sound Action Team website, 2004)

Rockfish populations (like many marine fish species) are slow growing species with low birth rates which puts them particularly at risk. (State of the Sound Report - Puget Sound Action Team website, 2004)

"In response to a petition (Wright 1999) to list 18 species of marine fish in Puget Sound under the ESA, NMFS initiated status reviews of seven of these species: Pacific hake, Merluccius productus (Ayres, 1855); Pacific cod, Gadus macrocephalus (Tilesius, 1810); walleye pollock, Theragra chalcogramma (Pallas, 1815); Pacific herring, Clupea pallasi (Valenciennes, 1847); brown rockfish, Sebastes auriculatus (Girard, 1854); copper rockfish, S. caurinus (Richardson, 1845); and quillback rockfish, S. maliger (Jordan and Gilbert, 1880)." "The BRT also expressed caution that important changes in resource management practices (e.g., increased harvest levels) and in the ecosystem (e.g., increased numbers of marine mammals or predatory fish species), as well as increased habitat degradation, could result in increased extinction risk for copper rockfish in this DPS. (NOAA Technical Memo # 46, 2001)

"In response to a petition (Wright 1999) to list 18 species of marine fish in Puget Sound under the ESA, NMFS initiated status reviews of seven of these species: Pacific hake, Merluccius productus (Ayres, 1855); Pacific cod, Gadus macrocephalus (Tilesius, 1810); walleye pollock, Theragra chalcogramma (Pallas, 1814); Pacific herring, Clupea pallasi (Valenciennes, 1847); brown rockfish, Sebastes auriculatus (Girard, 1854); copper rockfish, S. caurinus (Richardson, 1845); and quillback rockfish, S. maliger (Jordan and Gilbert, 1880)." "Although, the BRT recognized that herring populations in north Puget Sound and Puget Sound proper may be vulnerable to extinction, these populations represent a relatively small portion of the overall DPS of herring in the Georgia Basin." (NOAA Technical Memo # 45, 2001)

"In response to a petition to list 18 species of marine fish in Puget Sound under the ESA (Wright 1999), NMFS initiated status reviews of seven of these species: Pacific hake, Merluccius productus (Ayres, 1855); Pacific cod, Gadus macrocephalus Tilesius, 1810; walleye pollock, Theragra chalcogramma (Pallas, 1815); Pacific herring, Clupea pallasi Valenciennes, 1847; brown rockfish, Sebastes auriculatus Girard, 1854; copper rockfish, S. caurinus Richardson, 1845; and quillback rockfish, S. maliger Jordan and Gilbert, 1880." "In fact, most BRT members could not rule out the possibility that Pacific cod in DPS scenario 2 (Puget Sound to Dixon Entrance) are likely to become endangered in the foreseeable future." (NOAA Technical Memo #44, 2000)

"I have been working with a few key tribes and NMFS (Manchester lab) for the past several years on Lingcod and Pacific Cod enhancement. The technology is available and being used for these two species in Puget Sound. Yellow eye rockfish are also ready for Coastal enhancement. There are other species of concern in Puget Sound, but marine fish enhancement should proceed with these first. We have done "research level" releases of Lingcod and they have carried acoustic tags for tracking." and "In fact, most BRT members could not rule out the possibility that Pacific cod in DPS scenario 2 (Puget Sound to Dixon Entrance) are likely to become endangered in the foreseeable future." (Wright, NWIFC, 2006)

All of these sources reference species that are in serious enough decline that efforts should begin as soon as possible to understand the life cycle of the fish and consider the applicability of enhancement. The issues of slow growth rates, age of maturation and fecundity that increases with age in marine fish suggest that natural recovery will be slow at best. These same issues militate against any type of a quick response by enhancement efforts should a stock be found to be in trouble and not responding to habitat restoration and harvest reduction strategies. Traditionally, harvest reductions have been the result of diminishing resource availability and have tended to follow the problem in a downward spiral instead of creating a proactive response that anticipates the trajectory of the problem. Developing a marine fish enhancement capability is on way to get ahead of the downward spiral.

Numerous efforts are under way to restore Puget Sound. These include the Puget Sound Partnership, Puget Sound Strategy, Puget Sound Council, Puget Sound Action Team, and numerous Tribal, State and Federal agency regulatory processes. None of these efforts project a significant near term reversal of the problems that we face. Some suggest that significant results can be attained by 2020. Current activities and planned population growth will likely continue to deteriorate the Puget Sound environment, at least on a localized basis, for years to come. Even climate change may have significant impacts that we can not anticipate at this point.

Enhancement potential for Puget Sound marine fish

"The following species have been petitioned for listing in Puget Sound within the past 5 - 10 years: rockfish (brown, quillback, and copper), Pacific cod, Pollock, Pacific hake, and herring. None of these species were ultimately listed under ESA, but there is now a new petition that provides additional information and rationale for listing copper and quillback rockfish. Lingcod populations are considered to be depressed. All of these species with the exception of Pollock and Pacific hake have been successfully cultured and may be good candidates for stock enhancement on an experimental scale (Table 1). Within Puget Sound the NWFSC has reared and released small numbers of lingcod and Pacific cod and monitored their post-release behavior with the use of acoustic telemetry. We think that any of the species listed in Table 1 represent opportunities for stock enhancement in Puget Sound or Hood Canal." (Flagg, NMFS, 2006)


Table 1. STATUS OF CULTURE TECHNOLOGY FOR PUGET SOUND MARINE FISH SPECIES
Common name Species Laboratory Broodstock maintained Broodstock successfully spawned Spawning period Juveniles reared F1 Adults reared F1 Adult reproduction Juveniles/adults released
Ling cod Ophiodon elongatus NMFS X X Winter X X X X
Pacific cod Gadus macrocephalus NMFS X X Winter X X
Brown Rockfish Sebastes auriculatus NMFS & UCSB X X Spring X
Copper Rockfish Sebastes caurinus NMFS & Vancouver aquarium X X Winter-Spring X X
Quillback Rockfish Sebastes maliger NMFS X X Winter-Spring X

Table 1 was supplied by Barry Berejikian of the National Marine Fisheries Service at Manchester, WA. (Flagg, NMFS, 2006)

A great deal of work has already been done on the artificial culture of marine fish. Table 2 indicates additional species where research has progressed on different life stages up to and including the release of juveniles or adults. Continuing this work will be important to understanding the development of these fish and gaining more information about their complex interactions with the environment.

An important aspect of enhancement is that it will yield valuable information about environmental roadblocks to recovering marine fish species. Just as with salmon, release strategies often created as many questions as they answered. Using the valuable experience gained in salmon enhancement, we can structure our research to minimize impacts on wild stocks and maximize the feedback we get from our efforts to assess the status of the environment and the potential for recovery. Using measured and well controlled inputs we can find the critical areas for intervention, whether it is changes in the environment or temporary augmentation of life stages for the different species.


While the literature on marine fish enhancement was mostly cautionary, two articles suggested areas for future exploration. One of these was an analysis of the behavior of hatchery reared versus wild summer flounder (Kellison, et.al., 2000.) In it they discussed the differences in behavior that resulted from artificial rearing strategies of this economically significant bottom fish species. Their major findings were that hatchery reared fish spend t more time up in the water column and were less likely to bury themselves in the bottom materials. This resulted in less color adaptation, more movement and a higher susceptibility to predation. The cause of this more mobile behavior was probably due to the rearing conditions and feeding techniques where individuals were 'rewarded' for swimming to the surface to receive bountiful feed. Anti-predator conditioning reduced predation in hatchery reared fish but did not mitigate it entirely. They suggested that future experiments modify the feed introduction strategy and that ant-predation conditioning be continued (Kellison, et.al., 2000.) This is consistent with the lessons learned in conservation hatchery techniques discussed earlier.

A second article suggested a more novel approach to enhancement. In it, immature wild cod were trapped and held in floating marine net pen structures for grow-out and then release to participate in spawning behavior Rearing lengths included 1, 2 and 3 growth seasons. Because of enhanced nutrition, each subsequent year class increased dramatically in size in proportion to similar non-captive populations. As was mentioned earlier, overall fecundity is significantly improved by size. Mortality was also reduced to 5% as compared to the wild population losses of 18%. Results were that no reduction in egg viability resulted from captive rearing. Captive reared fish delayed their dispersal from the net pen site by two weeks upon release as compared to a 'wild' group that was held for a short time in the same facility. Spawning occurred 1 - 4 weeks earlier due mostly to size and water temperatures in the vicinity of the farm site in 'captive' fish. Harvest of 'captive' fish was slightly higher due to the selectivity of gillnets for a wider girth typical of this group. 'Captive' fish reintegrated over a known spawning ground similar to wild fish. "Captive' fish were more acclimated to warmer temperatures due to the location of the net pens and were more likely to be found in shallower water. Artificial genetic marking was suggested for future experiments to get better data on the progeny of released fish. (Wroblewski, et. al., 2002)

The advantages of this approach is that the genetic profile of the 'captive' fish mirrored that of the wild population impacted. Survival was increased suggesting a higher retention of genetic variability. Reintegration into the wild population was generally successful with some minor variations. Fecundity due to size increases as a result of improved nutrition was dramatically enhanced. Using genetic markers will allow for a better analysis of future progeny.

Conclusion


Marine fish enhancement faces many of the same challenges that were encountered in the first century of salmon enhancement in Washington State. A great deal was learned from these early mistakes and the development of conservation hatcheries suggests that may of these pitfalls can be avoided. It will be many years before dramatic improvements in habitat restoration and preservation will affect the marine environment significantly. Some species are already at depleted levels and others appear headed in this same direction. A limited number of opportunities exist to expand our ability to reverse these trends which may be increasingly important as declining stocks deteriorate. All future marine fish enhancement efforts need to be accompanied by a cautious scientific analysis of the species impacted and strategies developed to minimize and avoid this conflict to the greatest extent possible. Enhancement by itself is never the answer. Habitat protection and harvest restrictions are always critically important. Both are necessary for the health of the species in Puget Sound as well as for a comprehensive analysis of the success of enhancement efforts.

For these reasons, I believe it would be prudent to expand marine fish research and begin a limited enhancement effort in Washington State. While we have a long history of enhancement with salmonids, we still have a lot to learn about other marine species. With the lessons learned from our mistakes with salmon I believe that we can establish a marine fish enhancement effort that, when applied on an appropriate scale using the modern tools of conservation hatchery techniques and genetic analysis, will benefit our efforts to recover the stocks in Puget Sound.

Bibliography


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Salmon. American Fisheries Society Symposium 44:603-619

Flagg, T. A.. 2006. National Marine Fisheries Service (NMFS) at Manchester, WA.
Interview

Hilborn, Ray. 1998. The Economic Performance of Marine Stock Enhancement Projects.
Bulletin of Marine Science 62 no2 661-6674 March '98

Kellison, G. T., D. B. Eggleston, J. S. Burke. 2000. Comparative Behavior and Survival
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State of the Sound Report. 2004. Puget Sound Action Team website,
http://www.psat.wa.gov/Publications/StateSound2004/State_Sound_Report.htm

Utter, Fred. 1998. Genetic Problems of Hatchery-reared Progeny Released into the Wild,
and How to Deal with Them. Bulletin of Marine Science 62 no2 623-640 Mar '98

Wright, Terry. 2006. Northwest Indian Fish Commission (NWIFC). Interview

Wroblewski, J. S., H. W. Hiscock. 2002. Enhancing the Reproductive Potential of Local
Populations of Coastal Atlantic Cod (Gadus morhua). Canadian Journal of Fisheries and Aquatic Sciences: Oct.'02; 59 10; Research Library, pg. 1685, 11 pages