Helping Sturgeon Survive – Studies On Swimming Performance And Fishways Can Make A Contribution
Sturgeons (Acipenseridae) are primitive fishes that mature late and display migratory behavior. There are 25 species of sturgeon in the world and they have substantial value for both scientific and economic enterprises. However, for the past one hundred years, a rapid decline in sturgeon populations has been caused by human activities, including overfishing, pollution, and the proliferation of hydraulic structures, such as dams and other river works.
Hydraulic structures interrupt river connectivity, obstruct sturgeon migrations, and change hydrologic variables in ways that negatively impact sturgeon habitat conditions. As a result, sturgeon reproduction has diminished, and population gene exchange is hindered. All sturgeon species are on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, and 16 species are critically endangered.
Effective fishways for sturgeon can make a contribution to their migration. The design of fishways is related to both hydraulics and biological factors (migration behavior and swimming performance). Many salmon fishways were based on both hydraulic and biological studies, while many fishway designs for non-salmon species were based on hydraulics with limited biology, or copied salmon fishways with limited adaptations to meet the abilities of these species.
Different research approaches have been used to generate the data necessary to develop design criteria for fishways, but more information is needed to develop and optimize passage effectiveness in the following ways:
- Researchers invented many types of equipment, methods, and metrics for testing swimming performance, but it is insufficient and difficult to compare them. There is still disagreement on the best way to obtain criteria for designing fishways.
- To design fishways, it is important to study the swimming performance of mature sturgeons which migrate for spawning. However, the data are limited because there is no equipment that accommodates their large size.
- Because the flow in fishways and rivers are complex, studies on sturgeon swimming performance should be based on not only simple flow field or uniform flow, but also complex flow field. This makes experiments more realistic. In addition, more attention should be paid to the evaluation of multiple factors (such as temperature, flow velocity, dissolved oxygen, and fish size) and the interaction between factors to improve swimming performance models and make them more realistic.
- Fish fatigue influences swimming performance, may contribute to delayed mortality or inability to reach spawning grounds, and should be considered in the design of fishways. Flow velocity in the upper portion of a fishway may need to be lower than that in the lower portion, especially for long fishways. Fatigue influences fish health and survival and the influence of passage on the physical condition of migrants should be considered. Delayed mortality or failure to reach their spawning grounds and successfully spawn may occur because of fatigue during the entire process of barrier-passage.
- Researchers do study sturgeon upstream movement, but the study on sturgeon downstream movement is limited. Downstream migration is also needed to be studied in the future.