Redd Site Microhabitat Utilization and Quantitative Models for Wild Large Brown Trout in Three Contrasting Boreal Rivers

Abstract

Riverine spawning areas are important but restricted source habitats for large brown trout Salmo trutta (!40 cm total length). In hydrophysically different reaches within three contrasting boreal rivers, redds larger than 100 cm in length were located by direct underwater observation in 1998 and 2001 (n ¼ 157 redds; range ¼ 10-60 redds per reach and year) and were characterized based on 29 habitat variables. The microhabitat of utilized redd sites (total redd length: mean 6 SD ¼ 206 6 83 cm, range ¼ 100-615 cm) was typified by a mean total water depth of 103 6 39 cm with a wide optimum (range ¼ 23-215 cm) and a mean water velocity of 47 6 32 cm/s (range ¼ 2-124 cm/s). Mean velocity measured at 5 cm above the substrate was 29 6 20 cm/s (range ¼ 0-82 cm/s). Mean substrate particle size was 7 6 6 cm and demonstrated a narrower optimum (range ¼ 2-37 cm) than the other variables. Substantial differences among the three rivers, particularly in water depth and velocity measures, largely reflected size and gradient differences and indicated some flexibility in spawning microhabitat utilization. The use of substrate particle size was less variable. Multivariable analysis indicated that water velocity (except velocity measured just above the substrate) and water depth explained most of the variation. Depths and substrates utilized were larger than previously reported, probably reflecting the in situ habitat availability in the relatively large study rivers.

Timing of brown trout spawning in Alpine rivers with special consideration of egg burial depth

“…() and Wollebæk et al. () documented that brown trout females used coarser substrate for redd construction than reported in this study (Fig. ).…”

“…Only studies with a special focus on large brown trout (Wollebæk et al. ) found completely different values, which can be mainly explained by fish size. Interestingly, the range of the water depth used was quite narrow compared to other studies.…”

“…; Wollebæk et al. ). To detect differences between redds and the surrounding undisturbed area, all abiotic parameters were also measured at one point (always at the level of the tail) in the surrounding area.…”

“…; Crisp & Carling ; Walker & Bayliss ; Wollebæk et al. ) have focused on the habitat use of brown trout in general, only a few studies were conducted in mountain streams (Barlaup et al. ; Grost et al.…”

Aquatic Habitat Modeling in Running Waters

“…Numerous habitat modeling studies have been undertaken over time in North America and Europe, first mainly for salmonids (e.g., Northcote 1984;Shirvell 1989;Wollebaek et al 2008;Moir and Pasternack 2010) but later for non-salmonids also (e.g., Melcher and Schmutz 2010). Predominantly these studies applied univariate habitat use and preference curves.…”