. The Canadian field-naturalist. Natural history; Sciences naturelles. 20 The Canadian Field-Naturalist Vol. 119 Table 1. Spearman's rank correlation coefficients for over- all fish abundance relative to environmental variables in River Canard. Upper row denotes 1994 values. Number of meas- urements in parentheses. Variable Lower reach Middle site Upper reach Conductivity Secchi depth Temperature Flow volume (12) (9) (10) (9) (12) (9) (12) (9) (10) (10) (10) (10) (8) (8) (8) (9) tember, when the larges
. The Canadian field-naturalist. Natural history; Sciences naturelles. 20 The Canadian Field-Naturalist Vol. 119 Table 1. Spearman's rank correlation coefficients for over- all fish abundance relative to environmental variables in River Canard. Upper row denotes 1994 values. Number of meas- urements in parentheses. Variable Lower reach Middle site Upper reach Conductivity Secchi depth Temperature Flow volume (12) (9) (10) (9) (12) (9) (12) (9) (10) (10) (10) (10) (8) (8) (8) (9) tember, when the largest specimen (94 mm) was col- lected. As flow volume decreased to m3/d in late June, an isolated pool (-350 m2) developed at the sam- pling site. Eight species and 81% of the total collection were caught in this pool on 23 June. Orangespotted Sunfish was the sole recurring adult fish. Middle site Fishes represented 18 species and 7 reproductive guilds at the middle site. Non-guarding phytophils (Common Carp, Bigmouth Buffalo) and guarding nest- spawners, such as psammophils Bluntnose Minnows, Black Crappie, numerically dominated the assemblage. Highest catch and number of species were observed in late June (Figure 3). Logperch were first caught in mid-May and Gizzard Shad, Yellow Perch, White Suck- er, and Quillback in early June. Common Carp ( ± mm; N = 23), Bluegill, and Emerald Shiner next appeared in late June. Gizzard Shad, which represent- ed of the total collection (4744 fishes), was the only highly persistent species (Table 3). Although var- ious age 0 and 1+ fishes co-occurred in early spring and autumn, they were usually temporally separate dur- ing the early summer nursery period. Emerald Shiner was the only adult fish caught repeatedly. Lower reach Although sampling in 1994 began in late June, 12 taxa were found that were not caught in 1995, when collections began in April. However, these fishes con- 900 600 300. 400 15 300 200 100 A S O N 1500-1 2
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