Large‐bodied fish assemblage characteristics in large rivers across Ontario

Abstract

Large-bodied fish assemblages were assessed in large rivers across Ontario. The objectives of this study were to (i) determine if there were relationships in large-bodied fish species within rivers;(ii) determine what factors explain the variability in the abundance of large-bodied fish within rivers across Ontario; and (iii) assessed variation in large-bodied fish biodiversity among these river.Standardized index netting was conducted at 22 sites across 12 major rivers and sampled 3889 fish representing 26 species. Species associations were evident based on correspondence analysis. Walleye, Common White Sucker, Northern Pike and Lake Whitefish formed one group; Silver Redhorse, Shorthead Redhorse and Lake Sturgeon (adult and juvenile) formed another; Burbot, Longnose Sucker and Sauger were closely associated; and Cisco, Yellow Perch, Rock Bass, Smallmouth Bass and Brown Bullhead grouped. Canonical correspondence analysis was conducted to link species abundance patterns to environmental conditions. Walleye, Common White Sucker, Lake Whitefish and Smallmouth Bass were ubiquitous. Northern Pike abundance was negatively correlated with river discharge and longitude. Burbot, Sauger and Longnose Sucker abundance were positively correlated with deep rivers and discharge. Whereas Cisco, Yellow Perch and Rock Bass abundance were greater in wider rivers with lower discharge. Lake Sturgeon (adult and juvenile), Silver Redhorse and Shorthead Redhorse abundance were greater in narrow, longer rivers. Juvenile Lake Sturgeon abundance was positively correlated with longitude and river discharge. Mean species diversity and richness of large-bodied fish among all sites was 1.58 (0.36 SD) and 7.7 (2.6 SD). Species diversity was not significantly related to any of the variables used in the Generalized Linear Model; however, species richness was significantly related to maximum depth. This study demonstrated subtle differences in environmental variables affecting large-bodied fish at the landscape scale rather than those observed at the river scale.

Interaction of sauger Sander canadensis and walleye Sander vitreus in a large, shallow northern river

“…The sampling techniques were identical among these studies therefore permitting the comparison of relative abundance. This study supported that S. canadensis are common in large, shallow rivers (Bozek, Haxton, & Raabe, ) whereas at a landscape scale, they demonstrated proclivity to deep, high‐discharge river (Haxton et al, ) and were not as abundant. This study also corroborated the ubiquity of S. vitreus population across Ontario (Haxton et al, ).…”

“…Relative abundance of S. canadensis and S. vitreus were similar in the Rainy River. CPUE of both species was greater than observed in the Ottawa River (Haxton, ), whereas the CPUE of S. canadensis was greater than observed in most rivers sampled in Ontario; S. vitreus CPUE was within the range reported (Haxton et al, ). The sampling techniques were identical among these studies therefore permitting the comparison of relative abundance.…”

“…Sauger Sander canadensis (Griffith & Smith 1834) and walleye Sander vitreus (Mitchill 1818) are two closely related species of the family Percidae that are often found sympatrically in large rivers and lakes throughout North America (Billington et al, ; Bozek, Baccante, & Lester, ; Dendy, ). At a landscape scale across Ontario, Canada, S. canadensis were associated with deep rivers with higher discharge whereas S. vitreus were ubiquitous among rivers (Haxton et al, ). In contrast, S. canadensis have been reported as common in warm, shallow, turbid rivers (Bozek, Baccante, & Lester, ).…”

Assessment of lake sturgeon (Acipenser fulvescens) recruitment in a regulated spawning tributary of Rainy Lake, Ontario

“…near to the Sturgeon Falls HGS, proximal to which suitable spawning habitat occurs) while older juveniles were more abundant further downstream. A similar size/age distribution of juveniles (smaller juveniles located in upstream reaches) was observed among eight reaches of the Seven Sisters Falls Reservoir on the Winnipeg River (Barth & Anderson, ), whereas the opposite (larger sturgeon closer to upstream spawning sites and smaller juveniles in areas distant from spawning areas) has been observed in the Attawapiskat River (Haxton, Friday, Cano, & Hendry, ), Ottawa River (Haxton, ) and the St. Lawrence River (Mailhot, Dumont, & Vachon, ). Based on the finding that juveniles rarely move among reaches separated only by rapids (Barth, Anderson, Henderson, & Peake, ), Barth and Anderson () suggested that the distribution of juveniles in the Seven Sisters Reservoir on the Winnipeg River was likely determined prior to age‐1, driven by non‐random patterns of larval drift (likely influenced by hydraulic conditions, which would vary among years) or differential larval mortality (higher rates of larval or young YOY mortality distant from spawning areas).…”

“…Based on the finding that juveniles rarely move among reaches separated only by rapids (Barth, Anderson, Henderson, & Peake, ), Barth and Anderson () suggested that the distribution of juveniles in the Seven Sisters Reservoir on the Winnipeg River was likely determined prior to age‐1, driven by non‐random patterns of larval drift (likely influenced by hydraulic conditions, which would vary among years) or differential larval mortality (higher rates of larval or young YOY mortality distant from spawning areas). Assuming the premise that distance of larval drift is a function of hydraulics (water velocity) (Benson, Sutton, Elliott, & Meronek, ) and is transferrable among systems, it was hypothesized that the observed differences in spatial segregation of life stages among systems may be due to their regulated/unregulated nature, wherein a high proportion of larvae would drift farther from spawning sites in unregulated systems (Haxton et al, ). Although water velocity was not measured during this study, field crews working during spring qualitatively assessed velocities as <0.2 m/s in all reaches downstream of Reach 1 (North/South Consultants Inc., unpublished data) when the river was experiencing spring discharges of 50–75 m 3 /s.…”