Catchments affect growth rate of Northern Pike, Esox lucius, in subarctic lakes

A comprehensive understanding of how interactions between catchments and downstream lakes affect fish growth rate is lacking for many species and systems, yet is necessary for predicting impacts of environmental change on productivity of freshwater fish populations. We investigated among-lake variability in growth rate of Northern Pike (Esox lucius), a fish species of widespread subsistence and commercial importance. Northern Pike were captured from 11 subarctic lakes that span 60,000 km(2) and four ecoregions in the Dehcho Region of the Northwest Territories, Canada. Growth rates were related to stable isotope ratios and to lake and catchment physicochemistry. Growth, modelled using increment widths (n = 2953) measured on cleithra (n = 432), was significantly slower (p < 0.001, adj. r(2) = 0.78) in lakes subject to greater inferred catchment influence, which was quantified using a combination of lake and catchment characteristics. While Northern Pike growth rate was not related to delta N-15, it was positively related to delta C-13 (p < 0.001, adj. r(2) = 0.75). Further analyses revealed that benthic invertebrates in lakes subject to greater inferred catchment influence had more depleted delta C-13 ratios, and we posit that Northern Pike growth is slower in these lakes because terrestrially derived organic matter has relatively lower nutritional value and bioaccessibility, but further research is necessary. By linking current among-lake variability in Northern Pike growth to trophic ecology and to both lake and catchment physicochemical data, results inform predictions of how future changes to subarctic lakes and catchments may affect fish growth and productivity.

Automated summary

This study investigated the variability in growth rates of Northern Pike in different lakes in the Northwest Territories of Canada, finding that lakes with greater catchment influence showed significantly slower growth rates for the fish. The study linked Northern Pike growth rates to trophic ecology and physicochemical data of the lakes and catchments, providing insights into potential impacts of future changes on fish growth and productivity in subarctic regions.