# Influence of Lakeshore Riparian Vegetation on Diet, Feeding Rate, and Body Condition of Adfluvial Coastal Cutthroat Trout

## TL;DR

This study shows that lakeshore vegetation influences the diet and health of cutthroat trout by affecting the availability of terrestrial invertebrates.

## Contribution

The study provides new evidence linking riparian vegetation characteristics to trout diet composition and feeding behavior in small lakes.

## Key findings

- Cutthroat trout in lakes with intact old forests consumed more terrestrial invertebrates.
- Feeding rates and body condition correlated with overhanging vegetation and decaying wood in the littoral zone.
- Riparian vegetation cover was positively related to the intake of terrestrial invertebrates by trout.

## Abstract

Terrestrial invertebrates provide energy and nutrients to lacustrine systems. However, the extent to which lakeshore and riparian vegetation affects the diet of lake‐associated fish is not well known. We sampled six small lakes (< 1 km2 surface area) on the West Coast of British Columbia, Canada, to determine if lakeshore riparian vegetation composition and extent affected the diet, feeding rate, and body condition of adfluvial cutthroat trout (
Oncorhynchus clarkii clarkii
). We found strong evidence that cutthroat sampled from a lake with an intact, old forest riparian had a different diet composition comprised largely of terrestrial invertebrates than cutthroat sampled from lakes with riparian forests representing a gradient of vegetation age and cover. We identified positive relationships between the intake of terrestrial invertebrates by cutthroat with the percentage of riparian vegetation overhanging and submerged along and decaying wood within the littoral zone. We also found positive relationships between the percentage of vegetation overhanging and submerged along the littoral zone and the percentage of overstory terrestrial vegetation. Our study contributes to a growing body of evidence recognizing the connections between upland terrestrial and lakeshore riparian and aquatic ecosystems.

Our research compares the diet, feeding rates, and condition of Coastal cutthroat trout in six small (1 km2 area) lakes with lakeshore riparian zones representing a gradient of logging histories. We identified positive relationships between the intake of terrestrial invertebrates by cutthroat and the percentage of riparian vegetation overhanging and submerged along, and decaying wood within the littoral zone. We also found positive relationships between the percentage of vegetation overhanging and submerged along the littoral zone and the percentage of overstory terrestrial vegetation.