Effectiveness of an artificial stream in providing productive fish habitat in the Canadian Arctic

Few fish habitat compensation projects are rigorously assessed with respect to the principle of "no net loss" of productive capacity. To examine the effectiveness of a 3.4-km artificial stream in the Northwest Territories, Canada, I used reference streams to understand fish-habitat relationships and diet of YOY (young-of-the-year) Arctic grayling (Thymallus arcticus ) and to develop standards against functions of the artificial stream (e.g., production fish) could be compared. The artificial stream restored watershed connectivity, allowing fish migration, and provided spawning and nursery habitat, particularly for Arctic grayling. However, the mass of individual YOY grayling at the end of summer was 57% lower in the artificial stream than in natural streams. This difference in growth, in concert with estimates of grayling density, meant that the standing crop produced in the artificial stream averaged 37% of that found in natural streams. A bioenergetics model indicated that cooler water temperatures in the artificial stream had limited influence on growth. However, low amounts of autochthonous and allochthonous organic matter and poor physical habitat in the artificial stream appeared to limit the productivity of benthic invertebrates and fish. Resource selection functions developed for YOY grayling in natural streams indicated that there was an abundance of quality habitat for small grayling in the artificial stream, but a paucity of quality habitat for the larger YOY grayling. Habitat structures created to "enhance" the productive capacity of the artificial stream provided benefits at the local, but not at the whole-stream scale. Annual climatic variability and lake-outlet ecology affected the production of grayling in both the natural and artificial streams. Successful habitat compensation in this artificial stream will not likely be fully realized until more allochthonous and autochthonous organic matter is available to the benthic fauna and fish.