07 March 2011

Bioecology of Non-native Fish Stocking Policies in Western North American Lakes

My co-blogger, Dr. Carin Bondar
My partner for this first experiment in co-blogging is Dr. Carin Bondar, a rising starlet in popular biology who has developed a video blog series called "Biomusings." Her fifth, most recent episode of Biomusings focused on the research of an M.S. student who is looking at the ecological recovery of mountain lakes in Banff National Park in the decade since the stocking of sport fish was banned across Canada. I have lived in areas of Colorado where sport fishing is seen as an essential tourist draw, have seen similar lakes and rivers where stocking is still practiced by our own US government agencies as well as individuals, and have concerns about the ecology of these hydrologic headwaters. Dr. C was thus welcoming to an opportunity to explore this topic together. In addition to this overlap in our professional interests, my guess is that when you watch her videos and look through her work, you’ll be smitten too...

In her part of this co-blogging effort, entitled "Further Thoughts on Introduced Sportfish," Dr. C examines the ecological impacts of salmonid (i.e. trout) sport fish introduction on the food webs surrounding and woven through mountain lakes. When introduced fish were allowed in Canadian lakes, an artificial environment of competition was developed between the fish and several other species, including birds and amphibians, all of whom rely on native insect species for food. At the same time, as Dr. C and I discussed during formulation of this collaborative effort, the hydrology of the lakes may simply not be adequate for the natural propagation of the introduced species, not providing appropriate spawning habitat or environmental conditions [1]. We came to two obvious results from this idea. First, this lack of species-appropriate habitat and spawning grounds provides a compelling explanation for the absence of these species from the lakes in the first place. Second, the introduced species cannot find appropriate spawning habitat, such that each stocked cohort is either fished out or dies over the winter season, bringing about the need for another stocking effort every year and propagating the policy by tradition. Canada, recognizing the both the ecological imposition and ultimate futility of such efforts [2], eventually halted the practice in favor of "returning to nature" the lakes that had been altered up to that point. As Dr. C showed in the work of her student associate, the ecological impacts of the sport fishing era on competing fish species and other associated fauna are still evident even a decade after the ban on stocking practices was enacted.

In the US, no such ban on stocking of sport fish has been introduced to the policy debate. For that matter, there seems to be no such policy debate; fish rearing and stocking activities are a basic function of the US Fish and Wildlife Service (USFWS). Questions surrounding the practice have become evident in relevant scientific literature and have floated through the years with little notice from the professional (that is, government) policy-makers. It is only recently, coincidentally since the Canadian ban was enacted, that researchers in the US have begun to demonstrate more seriously and in greater detail the ecological impacts of introduced species on native fish and other fauna in mountain lakes and rivers of the US Rocky Mountains and Sierra Nevada, as well as the effort that may be required to re-establish native species that have been crowded out or become endangered over time. Many of these researchers are looking in from the outside, however: the decision-making process is still managed by those government agencies that develop and control the natural areas, national parks, rivers, lakes and reservoirs in the mountain regions. Competing goals are just part of the problem; competing bureaucratic interests often obscure the goals entirely.

from Dunham et al. (2002) as listed below
USFWS jurisdiction overlaps in various wilderness and forest areas with the US Forest Service (USFS), the National Park Service (NPS), the Bureau of Reclamation (USBR), and the US Army Corps of Engineers (USACE). Interactions with state-level government agencies and managers offer even greater complexity in the overall management of natural resources [3]. Bureaucratic development of the benefit-cost analysis that helps evaluate the utility of proposed projects has numerous pitfalls, including that recreation is considered a significant and countable benefit while unmitigated environmental impact is often an indeterminate cost. When the known outweighs the unknown, and the known project benefits are great enough, the introduction of non-native species for recreational sport fishing is simply a matter of money and not a matter of known or anticipated ecological impact. Across the western US the introduction of sport fishing species to historically fishless lakes [4] has resulted in an unsustainable tradition of ecological alteration while native species, such as the cutthroat trout in the Rocky Mountains, are out-competed and eventually eliminated from their indigenous habitats by introduced species such as brown, brook and rainbow trout [5]. The historical native geographic ranges of cutthroat and rainbow trout are shown in the figures, and it is clear that the spread of rainbow trout eastward from the west coast of North America [6] to the Rocky Mountains is an artificial invasion by a translocated nonnative species. Add to this problem the impacts on food webs as addressed by Dr. C in her blog post on the topic, and we must see that our human meddling in the natural order of mountain rivers and lakes in the North American West extracts an innumerable cost. Fish stocking policy, especially using non-native species, remains detrimental to the ecology of the region as well as a continuing drain on financial and personnel resources.

from Metcalf et al. (2008) as listed below

One final issue for this overview, which must be recognized in an eventual debate on the topic, is an inevitable effort to re-establish the native species in their traditional habitats while, or after, the introduced fishes are removed. Scientists have found that translocated cutthroat trout, even within the ranges of their traditional geographic distribution, do not always successfully re-establish "native" populations in their traditional or former habitats for several reasons [7, 8]. Not only do we understand little about salmonid habitat preferences and tolerances over their life cycle even as our management practices have all but eliminated native species, but we must recognize that where there was once "native" habitat previously, the introduction of competing species and human practices may have modified the habitat (e.g., the thermal environment [9] and the altered food web [10]) beyond the tolerances of the returning cutthroat trout. What was once their home, for reasons of adequate spawning and feeding grounds and food availability that we are still attempting to understand, has been modified to an intolerable environment by the time of their return. It is certainly a tragedy to find that your old home has changed beyond recognition in the years since you last saw it.


[1] Rosenfeld, J., 2003: "Assessing the habitat requirements of stream fishes: An overview and evaluation of different approaches." Trans. Am. Fisheries Soc., v. 132, pp. 953-968. DOI: 10.1577/T01-126

[2] Schindler, D.W., 2000: "Aquatic problems caused by human activities in Banff National Park, Alberta, Canada." Ambio, v. 29, pp. 401-407. DOI: 10.1579/0044-7447-29.7.401

[3] Knapp, R.A., P.S. Corn, and D.E. Schindler, 2001: "The introduction of nonnative fish into wilderness lakes: Good intentions, conflicting mandates, and unintended consequences." Ecosystems, v. 4, pp. 275-278. DOI: 10.1007/s10021-001-0009-0

[4] Bahls, P.F., 1992: "The status of fish populations and management of high mountain lakes in the western United States." Northwest Sci., v. 66, pp. 183-193. (open-access pdf)

[5] Dunham, J.B., S.B. Adams, R.E. Schroeter, and D.C. Novinger, 2002: "Alien invasions in aquatic ecosystems: Toward an understanding of brook trout invasions and potential impacts on inland cutthroat trout in western North America." Rev. Fish Biol. Fisheries, v. 12, pp. 373-391. DOI: 10.1023/A:1025338203702

[6] Metcalf, J.L., M.R. Siegle, and A.P. Martin, 2008: "Hybridization dynamics between Colorado's native cutthroat trout and introduced rainbow trout." J. Heredity, v. 99, pp. 149-156. DOI: 10.1093/jhered/esm118

[7] Harig, A.L., K.D. Fausch, and M.K. Young, 2000: "Factors influencing success of greenback cutthroat trout translocations." North Am. J. Fisheries Manage., v. 20, pp. 994-1004. DOI: 10.1577/1548-8675(2000)020<0994:FISOGC>2.0.CO;2

[8] Harig, A.L., and K.D. Fausch, 2002: "Minimum habitat requirements for establishing translocated cutthroat trout populations." Ecol. Appl., v. 12, pp. 535-551. DOI: 10.1890/1051-0761(2002)012[0535:MHRFET]2.0.CO;2

[9] Bear, E.A., T.E. McMahon, and A.V. Zale, 2007: "Comparative thermal requirements of westslope cutthroat trout and rainbow trout: Implications for species interactions and development of thermal protection standards." Trans. Am. Fisheries Soc., v. 136, pp. 1113-1121. DOI: 10.1577/T06-072.1

[10] Eby, L.A., W.J. Roach, L.B. Crowder, and J.A. Stanford, 2006: "Effects of stocking-up freshwater food webs." Trends Ecol. Evol., v. 21, pp. 576-584. DOI: 10.1016/j.tree.2006.06.016


jmessner1 said...

Hi Matthew:

My name is Jordan Messner. I am the MSc (not Ph.D) student that worked with Carin on the filming of my thesis project, "Ecosystem Resilience of Mountain Lakes Stocked with Exotic Sportfish". Before beginning my graduate research in the Canadian Rockies I worked for the Idaho Dept of Fish and Game for a number of years, in central Idaho, surveying remote backcountry and frontcountry mountain lakes for fish and amphibian presence. Many of those lakes are still being stocked (some of which are in the River of No Return Wilderness…one of the largest wilderness areas in the lower 48 states) and some have not been stocked in over a decade.
Although I agree with you that in a great number of these lakes, fish persistence is only possible by way of continued stocking, that has not been the case in many instances. I think the number one reason that fish were not able to naturally colonize these systems is a result of the extreme gradient of their outlets, and the presence of natural (waterfall) barriers that did not allow migration upstream any further. The introduced fish do have strong negative effects on resident amphibian and invertebrate communities in mountain lakes throughout the west, and this has been shown in a number of studies as you know. What has also been shown (and is currently being studied by myself and others) is that recovery is possible (in many...but not all cases) once fish are removed from these lakes. One estimate is that recovery of zooplankton communities would take an average of 19 years, following the removal of introduced salmonids (Donald et al. 2001).
My research and the study sites I have chosen, will allow me to test this prediction, since I've got access to zooplankton data reaching as far back as the 1960's (to present) in a number of lakes that have variable histories. Although it is feasible for exotic fish in mountain lakes to be actively removed, and native biotic communities may be able to recover from the stresses of those fishes, the really difficult situation lies in dampening the impacts of all of the introduced fishes, and their offspring, that have escaped the lakes in which they were originally stocked, and are now competing and preying upon native fish species and other biota in lotic habitats downstream.
I know of one study site in a remote area of Banff National Park in which Parks Canada staff has been battling hard for the past 7 years to not only remove exotic Brooks from the lakes (which took only a couple years) but has also been eradicating the entire downstream stretches to eliminate these fish which are having a variety of negative consequences on native Bull trout populations. They have been very successful in doing so but after 7 years, Parks is pulling their funding on the project, so who knows what will happen now. As you know, funding opportunites (especially these days) are few, and are very competitive. Although I agree with you that stocking lakes is hugely detrimental to native communities, I think one smart option would be to find some sort of balance where appropriate recreational fishing lakes in the backcountry can still be maintained to keep anglers happy, which in turn will provide SOME funding (license sales and support through interest groups such as Trout Unlimited) for further research and eradication effort in areas of special concern, where such funding is needed. Perhaps one possible option would be to focus stocking efforts on supplementing native fish populations in watersheds where they are struggling. This seems to me like a valuable topic to explore, given that I too believe recreational fishing in the backcountry in a valuable economic and recreational resource.

My two cents.

Donald et al. 2001. Recovery of zooplankton assemblages in mountain lakes from the effects of introduced sportfish. Can J. Fish. 58:1822-1830.

M. Garcia said...


Thanks very much for adding your comments on the issues and about your own work on this project. I was very glad to work with Dr. C on this topic, and I hope that we can revisit it and some of the more nuanced aspects sometime soon. I agree with your idea that something can still be done to please the fishing community that would also help fund the work that needs to be done, and at the same time bolster the native fish populations instead of introducing what are tantamount to invasive species. Your experience and research will be great support for policy decisions in the near and long-term future, especially when lawmakers decide again that it is an affordable undertaking to protect our environment and the functional native ecology.

Best of luck on your MS thesis! Please don't hesitate to write with updates, new results, and ideas for us to collaborate on blogging the science--I'll be glad to help get your work out to as wide an audience as possible through this forum!