Esocid Family Responses to Warming Temperatures: Laboratory Experimentation on Species Metabolic Rates

Annual temperature variation in nursery habitat may be a mechanism of relative esocid success in the upper St. Lawrence River. Noticeable declines in northern pike and muskellunge populations have occurred in recent decades. Conversely, grass pickerel appear to be increasing in regional abundance and chain pickerel have expanded in range, with populations residing in Lake Ontario near the upstream mouth of the St. Lawrence River. Basal metabolic rates among four young-of-year esocids were compared in five thermal treatments (20, 23, 26, 28, 30⁰C) using static respirometry to contrast oxygen preferences among the species and infer habitat suitability. Grass and chain pickerel were hypothesized to have lower respiration rates than northern pike and muskellunge at the higher temperatures due to their assumed tendency to remain in shallow waters longer during summer warming. Respiration rates for grass pickerel were significantly higher and chain pickerel were significantly lower than northern pike and muskellunge (Waller-Duncan 0.515 and .363 vs 0.425 and 0.419 ml O₂/g hr, respectively). Interaction existed between species and temperature (p = 0.023, α = 0.05). Preliminary results suggest highest potential for chain pickerel success given trends towards habitat and climate warming. Since size was statistically significant beyond interspecies differences, further respiration studies on different sized young-of-year individuals are necessary to support the results of this study.