Improving Habitat Connectivity in a Typha-Dominated Wetland Shows Increased Larval Northern Pike Survival

A decline in northern pike (Esox lucius) abundance in the upper St. Lawrence River is thought to be related to hybrid cattail invasion and disruption of natural water-level periodicity leading to spawning and nursery habitat degradation. Channel-connectivity and spawning-pool excavations were implemented in a tributary to the upper St. Lawrence River to enhance spawning and nursery site complexity. We assessed the effects of excavations on pike by comparing percent survival (from advanced larvae to fall emigration), water quality factors, and larval diets at excavated and non-excavated sites. Lab-reared pike, 16 days post-hatch and 14 mm in length, were released at three site types: non-excavated, spawning pool, and channel. Percent survival in channels and spawning pools after a minimum of 26 days was nearly identical (2.4%), and greater than non-excavated sites (0.13%). Spawning pools displayed higher water temperatures and dissolved-oxygen concentrations than either channel or non-excavated sites. Larvae primarily consumed zooplankton and diets of larvae from spawning pools and non-excavated sites were similar, whereas larvae in channels consumed different taxa. Differences in diet were not reflected in survival, suggesting larvae were not prey-limited. Observed differences in percent survival among sites demonstrates created spawning pool and channel-connectivity sites enhanced conditions for pike.