Researching and Restoring West Virginia’s Declining Brook Trout Population

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

Unfortunately, West Virginia’s natural choice for a state fish is declining. 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 is void of native brook trout, suggesting that other variables could be responsible for the decline of WV’s state fish. A conversation with WV DNR biologists theorized that calcium precipitate could be limiting juvenile brook trout survival.

Calcium precipitate, also known as marl, is common to hardwater streams. However, calcium ions only remain in solution 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 cover and 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 springwater 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 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 ^oC.

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 presence of gravel substrate could have contributed to 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 ^oC) 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 ^oC, but was significantly lower (< 20% ) at 13.7 ^oC, 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 hardwater streams like Rockymarsh Run, while the second study confirmed that water temperature > 13.7 ^oC is 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.

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

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