by Hal Hagen, Aquatic Alternatives
|Photo 1: Aerial view of the North Park ranch project showing the all seven lakes and ponds that were created and connected with spawning/fisheries streams to allow migration from lake to lake and self-reproducing fisheries.|
In early 1800s, populations of fish in the western United States existed much as they had for thousands of years. Many populations of cutthroat trout lived their lives in isolated drainages that gave rise to unique strains adapted to environmental conditions such as water chemistry, pathogens, stream and lake characteristics that are unique to those drainages.
As the West developed, agriculture, deforestation, water impoundments, and mining began impacting these populations to the point where many unique strains and populations became extinct. Concerns over these losses led to the development of a hatchery system that aided in repopulating affected streams and lakes. This approach has worked for over one hundred years, but new issues are on the horizon that this prevailing fisheries management paradigm is struggling to answer.
One of the main problems with restocking depleted fish populations is the creation of more homogenous populations where once unique strains existed. The loss of this unique genetic heritage represents the loss of populations capable of resisting many possible catastrophic stressors. Populations of fish like the greenback cutthroat are being protected and making a remarkable recovery. With more attention being paid to recovery and restoration efforts of riparian habitats, these successes will continue. However, there is another way in which the development of populations of wild fish can have a positive impact.
|Photo 2: Largest lake in the North Park Ranch project which then feeds into the other 6 lakes. The lake was designed and constructed to provide habitat for all fish age classes.|
Aquatic Alternatives, a company founded in 1988, has had the opportunity to work on several private ranches in the West focusing their work on establishing wild-like populations of trout. The company realized that the conditions necessary to generate unique fish populations still exist and that the processes of natural selection within drainages are actively at work. However, the biggest limiting factor keeping them from generating unique populations is the almost constant introduction of fish from outside the drainage, or more precisely, the stocking of trout to keep up with the recreational pressures placed on these waters. The fact is that most rivers, streams, and lakes are not productive enough to keep up with the fishing pressures placed on them. The question is then how to improve the productivity within the drainage so that special strains of trout can develop. When we work on a project, we focus on the following components of an improvement project to improve productivity.
First and perhaps most obvious is that the watershed needs to be in as good a condition as it can be. In most cases, industry, agriculture and communities are aware that sound environmental practices are beneficial to aquatic species, and water quality has steadily improved throughout the West. There are, however, some impacts on watersheds that cannot be avoided and this is not necessarily a bad thing. Naturally-occurring pollutants have always affected fish populations and are part of the environmental stressors that have molded unique strains and species of fish. Stressors are, in fact, vital to developing a genetic resource that could someday be the salvation of aquaculture as well as wild fisheries.
The second factor affecting the productivity of any aquatic system is the ability of trout to reproduce successfully and in enough numbers to exceed anticipated human pressure. In general, a spawning adult trout is looking for an area where water is moving through a gravel bed so that oxygen is available for the developing egg. Building suitable spawning areas for trout in rivers or inlets to lakes can be enhanced if the temperature of the main body of water is influenced by a spring or other area where ground water is released into the channel. The number of days it takes for an egg to hatch is related to temperature and is adversely affected by fluctuating temperatures or water that is too cold or too warm. In the wild, it is normal for only one to two percent of a spawn to reach adulthood. Since recruitment of young trout depends on how many hatch, water temperature can be critical.
Assuming that a well-constructed spawning bed is successful in producing a greater number of fry, the survival of the fry and fingerling to adults is the next major hurdle. The behavior of young fish often leaves them vulnerable to predation or to other environmental influences that can carry them into unsuitable habitats where there is either a lack of suitable forage or cover. Building protected habitats for fry and fingerling must also include the development of habitats for properly-sized forage organisms. These protected areas should be placed in succession so that as the young fish grow they do not have to move far from one area to the next.
Building a forage base capable of supporting a larger-than-normal population of fish is critical and can be accomplished in a number of ways. Generally speaking, the process is simple to understand. Coarse and fine organic particulate needs to be trapped in a well-oxygenated part of the stream or lake where there is an abundance of surface area for bacterial colonization. Trapping this material keeps the nutrient for the base of the food chain available to the fish population rather than allowing it to move downstream.
Finally, strain and species selection is perhaps the most important for establishing a unique genetic resource. For one current project we began with two federally-certified strains of rainbow trout. We are hopeful that the hybridization of these two strains will lead to a fish capable of withstanding one known pathogenic stressor found in the area and enhance a strain of rainbow already found in the drainage. Because they are from known strains, we can track their progress in the future. ..
In our work we have found that privately-held ranches are an excellent place to start. Owners are interested in how the riparian and aquatic habitats on their ranches can best be utilized both for personal enjoyment and economic gain. It is interesting to note that as the projects proceed, neighbors become interested in what they can do with their aquatic resources. The fact that they may be the beginning of a genetic resource with greater long-term viability fits with these goals.