Comparative diets and foraging strategies of subyearling Atlantic salmon, brown trout, and rainbow trout during winter

Abstract

Summary Over‐winter survival of salmonids in streams is thought to be an important population regulation mechanism. Yet because of the difficulty of conducting field studies due to adverse weather or ice conditions, compared to other seasons, salmonid ecology during winter is least understood. Consequently, we sought to examine interspecific feeding associations of an important salmonid stream assemblage in the Lake Ontario watershed during winter. The diets of Atlantic salmon (Salmo salar) parr, brown trout (S. trutta) parr, and rainbow trout (Oncorhynchus mykiss) parr were significantly different in February but not in March. Salmonid diets differed from the benthos and the drift during both months. Dipterans (chironomids, simuliids, and tipulids) and ephemerellids were the major prey taxa consumed. All three species fed more heavily on prey items from the benthos than from the drift. The diet of Atlantic salmon had the highest similarity to the benthos whereas the diet of brown trout had the lowest similarity to the drift. All three salmonid species generally selected ephemerellids, limnephilids, and chironomids and avoided elmids. These winter feeding observations are the first reported for this specific salmonid assemblage and will help managers better understand interspecific associations during this critical period.

Trophic niche overlap and abundance reveal potential impact of interspecific interactions on a reintroduced fish

“…Diets within the fish community may also change seasonally depending on food availability. Convergences in diet may occur during times in which food resources are more limited, such as overwinter as seen with YOY rainbow trout, brown trout, and Atlantic salmon (Johnson et al 2017). Yet fish can also converge in diets during times with greater prey abundances and resource subsidies, such as terrestrial arthropods falling into streams in the summer (Nakano et al 1999;Kawaguchi and Nakano 2001).…”

Advantages and insights from a hierarchical Bayesian growth and dynamics model based on salmonid electrofishing removal data

“…The effect of temperature on growth is strongly mediated by food consumption; the optimum temperature for growth varies considerably depending on ration size (Brett et al, 1969;Elliott, 1975a,b;Piccolo et al, 2014). Since salmonids are highly territorial and juvenile and subadult fish feed on benthic and drifting macroinvertebrates (Oscoz et al, 2005;Johnson & McKenna, 2015;Johnson et al, 2017), in situ food ration is likely related to intrinsic (conspecific density) and extrinsic factors (discharge, macroinvertebrate density, etc. ), which are the factors that were found to be connected to salmonid growth (Table 1).…”

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low‐productivity rivers in northern Europe

“…Additionally, juvenile salmonids in high‐productivity streams in Alaska and Ireland depend more highly on terrestrial prey rather than larval aquatic prey due to the high amount of riparian vegetation surrounding the streams (Dineen et al, 2007; Grunblatt et al, 2019). Salmonids in sub‐Arctic streams can use terrestrial prey as a substitute food source during the summer to compensate for the low nutrient levels and colder climates, whereas in the winter, salmonids would have to rely more on aquatic insects (Amundsen & Gabler, 2008; Johnson, DiRado, Mackey, & Abbett, 2017; Johnson & Ringler, 2016).…”