Temporal patterns of young-of-year fish emigration in Upper St. Lawrence River coastal wetlands in relation to environmental change

Abstract

Young-of-year (YOY) fish emigration from shallow coastal wetlands to deeper embayments via connectivity channels represents a critical life history milestone. Emigration is typified by growth, dispersal, and changes in nursery habitat that influence species differently based on abiotic tolerance. To test this, we conducted a field study examining the relationships between YOY fish emigration and abiotic conditions in two freshwater coastal wetlands dominated by hybrid cattail Typha x glauca (Typha). Water level (WL), water temperature (WT), and dissolved oxygen concentration (DO) were monitored in these sites and temporally coupled with 42 consecutive days of YOY fish emigration. Individuals from five taxonomic groups emigrated over multiple time periods for a total catch of 25,272 YOY fish. Daily capture data was modeled with a Generalized Linear Model (GLM) to examine the influence of mean daily WL, mean daily WT, and mean daily DO on YOY fish emigration. Emigration patterns were variable for each taxonomic group and linked to known abiotic tolerance. Models of daily catch and environmental covariates indicated that increasing WL, WT, and decreasing DO had a significant effect on emigration. Typha dominance and reduced open water habitat likely influenced WT and hypoxia and may provide an advantage for tolerant protracted emigrants like largemouth bass (Micropterus salmoides) and brown bullhead (Ameiurus nebulosus). More sensitive groups like Leuciscidae (formally Cyprinidae), Lepomis, and smallmouth bass (Micropterus dolomieu) emigrated over truncated periods dependent on abiotic conditions. These findings highlight the role of fish tolerance and abiotic conditions during seasonal YOY fish emigration from USLR coastal wetlands.