Variation in resting respiration rate of Brook Trout among source populations: Implications for bioenergetic models

Our objective was to compare wild and hatchery sourced Brook Trout Salvelinus fontinalis to determine the importance of source population on routine respiration rate (RRR), the major cost term in bioenergetic models.We evaluated intraspecific variation in RRRs of one hatchery and four wild Brook Trout populations. Hatchery fish were obtained from the Bowden State Fish Hatchery in Elkins, West Virginia, and were the basis for the previously published bioenergetics model for the species. Wild fish were obtained from four headwater streams in West Virginia. Using intermittent respirometry, we measured and analyzed RRRs sequentially at 20, 16, and 12°C. Measures on hatchery fish were censored to restrict the dataset to similar sizes and temperatures as used with the wild populations. We used a suite of mixed effects models and one linear model to compare RRRs of hatchery fish with wild fish, as well as to determine whether wild populations differed.We found that the RRR of hatchery fish was double that of wild fish over the range of 12–20°C. Within the wild populations, the RRR of the Potomac drainage fish was lower than two of the three Ohio drainage populations despite all steams falling within 55 km of each other.Our findings suggest that selective pressures at the hatchery, as well as factors that influence thermal regimes in wild populations, likely influence RRR in Brook Trout. More research is needed to identify correlates related to intraspecific variation in fish respiration rates. Most fish bioenergetics models are not based on, or calibrated to, the specific population to which they are applied. Therefore, we encourage greater efforts be expended to calibrate and validate such models in the future.