West Virginia’s native brook trout are struggling. A collaboration between the West Virginia Division of Natural Resources and TCF’s Freshwater Institute looks to combat these losses, increase the success of brook trout reintroduction efforts and restore West Virginia’s brook trout population.

The brook trout is the only trout species native to West Virginia streams. And just like the state in which it thrives, it’s quite a sight to behold. The species has a dark green back with small markings, bluish sides covered in yellow and red dots, orange-red lower fins, and a pink belly.

Unfortunately, West Virginia’s state fish is in decline. Changes in land use, increasing water temperature and loss of streamside canopy and shade have caused populations to dwindle.

Our Role

Freshwater Institute staff realized that Rockymarsh Run, a local stream that flows next to their facility, has the correct environmental conditions to support brook trout populations. However, the stream was devoid of native brook trout, suggesting that other variables could be responsible for the decline of West Virginia’s state fish. Biologists with the West Virginia Division of Natural Resources (WV DNR) theorized that calcium precipitate could be limiting juvenile brook trout survival.

Calcium precipitate, also known as marl, is common to hard-water streams. However, calcium ions remain in solution only when water pH is low or slightly acidic. When hard water is aerated, the pH shifts upward and calcium precipitates out of solution, forming a powdery silt that could potentially suffocate brook trout eggs and young fish.

An experiment was developed to test the hypothesis. Three very different water types that are common to Rockymarsh Run were created in the Freshwater Institute’s new research facilities for use in the trial, including a raw spring water condition with low pH, a lightly aerated water with mid-range pH and a continuously aerated treatment with high pH and obvious calcium precipitate. Brook trout eggs from neighboring Virginia’s Paint Bank Fish Hatchery were obtained and stocked in replicate trays with fine gravel to simulate the substrate used in brook trout nests. Mean water temperature was 13.8 degrees Celsius.

Juvenile brook trout survival was low across all treatments; however, not a single brook trout survived in the high pH and calcium precipitate condition. Calcium siltation covered the gravel and brook trout eggs in these containers.

A second study was carried out to evaluate whether water temperature and/or the presence of gravel substrate could have contributed to the generally poor survival observed during the first trial. Brook trout eggs from the same provider were maintained in chilled water (8.1, 11.2 and 13.7 degrees Celsius) in hatching trays with and without gravel substrate. All conditions supported the formation of calcium precipitate. Interestingly, brook trout survival was 50-60% in systems maintained at 8.1 and 11.2 degrees Celsius, but was significantly lower (less than 20%) at 13.7 degrees Celsius, while no correlations to gravel substrate were observed.

Why This Project Matters

The findings from the first study supported the hypothesis that calcium or marl precipitate could be limiting brook trout survival in hard-water streams like Rockymarsh Run, while the second study confirmed that water temperatures greater than 13.7 degrees Celsius are not ideal for juvenile brook trout in environments that produce calcium precipitate. These science-based results provided important information to WV DNR regarding habitat suitability for native brook trout reintroduction efforts.

Freshwater Institute staff continued to grow the brook trout remaining from both studies. In mid-March 2019, several hundred brook trout were picked up by WV DNR and reintroduced to the local Opequon Creek with the hope that they would continue to grow and thrive. The stocking was carried out in partnership with Shepherd University as a hands-on learning experience for local college students. Similar educational outcomes are planned for the brook trout remaining from the second trial.

This synergistic project between the WV DNR and TCF’s Freshwater Institute resulted in positive outcomes that are aiding brook trout reintroduction efforts and contributing to successful conservation in West Virginia.