Evaluating Brook Trout Egg and Alevin Survival at Different Temperatures in Simulated Karst Environments with Marl Sedimentation

Authors: DAVIDSON, JOHN - Freshwater Institute; RAINES, CLAYTON - Us Geological Survey (USGS); CROUSE, CURTIS - Freshwater Institute; GOOD, CHRISTOPHER - Freshwater Institute; KEPLINGER, BRANDON - West Virginia Division Of Natural Resources

Submitted to: Southeastern Association of Fish and Wildlife Agencies Conference
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2023
Publication Date: 3/1/2023
Citation: Davidson, J., Raines, C., Crouse, C., Good, C., Keplinger, B. 2023. Evaluating Brook trout egg and alevin survival at different temperatures in simulated karst environments with marl sedimentation. Southeastern Association of Fish and Wildlife Agencies Conference. 10:27-35.

Interpretive Summary: Native brook trout have been extirpated from hardwater streams in the Eastern panhandle of West Virginia, in some instances, despite environmental conditions that support survival. The authors hypothesized that calcareous sediment (marl), which commonly forms in these streams, may inhibit brook trout egg and alevin survival. To test this hypothesis, fertilized brook trout eggs were held in three water types created by different aeration techniques (Study 1). Each water type imparted varying amounts of marl which was observed as coating on hatching units and egg surfaces. A second study was carried out to evaluate the interactive effect of water temperature and gravel substrate under similar conditions. During Study 1, brook trout survival was negligible across treatments, with the only surviving alveins observed in water with intermediate pH and carbon dioxide levels and without marl sedimentation. During Study 2, marl was produced in all treatments, but significantly lower survival and increased prevalence of spinal deformites was observed at 13.7oC versus 8.1 and 11.2oC. These studies indicate that calcareous precipitate does not cause catastrophic mortality, but may interact with other environmental conditions, such as temperature, to inhibit juvenile brook trout survival. This research provides important insight into environmental suitability aspects of karst-geology streams that will facilitate Brook Trout conservation efforts.

Technical Abstract: While the habitat requirements for Brook Trout Salvelinus fontinalis have been well-documented, research focused on the impact of calcareous sediment (marl) on early life stages is lacking. This condition is common to karst-geology streams in the distal Eastern Panhandle of West Virginia where Brook Trout have been extirpated. Two lab-based studies were conducted to determine if Brook Trout egg and alevin survival is inhibited by marl. During Study 1, three water types were generated from aeration treatments applied to source water from a limestone spring (13–14oC; hardness > 300 mg/L as CaCO3) including: raw/untreated (RU), once-aerated (OA), and continuously aerated (CA). These treatments respectively created an increasing gradient of marl precipitation. Brook Trout eggs obtained from a local hatchery were fertilized and stocked among replicate, gravel-filled trays receiving each water type. Egg mortality occurred faster in CA water where marl coated gravel and egg surfaces; however, cumulative survival was negligible for all water types. After 53 days, no surviving alevins remained in RU or CA water, and only 1% survival was observed in OA water. Interestingly, extra eggs maintained in a marl-producing, chilled-water (8oC) system without gravel demonstrated > 50% survival. A second trial was carried out to understand this discrepancy. During Study 2, Brook Trout survival was evaluated at three temperatures with and without gravel while creating marl. Significantly lower survival (< 22%) was observed at 13.7oC versus 8.1 and 11.2oC (> 50%), but gravel did not affect survival. Higher prevalence of alevin spinal deformities was also observed at 13.7oC. Negative effects imparted by marl were suspected, but Study 2 findings suggested that early life stage Brook Trout survival is not fully inhibited by these conditions. This research provides insight into environmental suitability aspects of karst-geology streams that are applicable to Brook Trout reintroduction and conservation efforts.