Redd-Site Selection by Brook Trout and Brown Trout in Southwestern Ontario Streams

Abstract

Redd‐substrate composition, water velocity, depth, and other environmental variables associated with redd‐site selection and spawning by brook trout Salvelinus fontinalis and brown trout Salmo trutta in southwestern Ontario streams were examined. Sympatric and allopatric populations spawned in similar ranges of specific conductance (225–810 μmhos/cm), pH (7.0–8.2), dissolved oxygen (>83% saturation), and stream gradient (0.2–2.3%). Brook trout spawned exclusively in areas of groundwater seepage, typically near headwaters where streamflow did not exceed 177 litres/second. Brown trout spawned in a wider range of flows (21–600 liters/second), and utilized locations with and without groundwater seepage. Spawning by brook trout usually began by the second week of October, by brown trout a week later. Brook trout spawning periods lasted 3–5 weeks, those of brown trout, 2–4 weeks. In sympatric populations, an overlap in spawning time occurred for up to 3 weeks. Reuse of redds was mostly intraspecific, although interspecific reuse of brook trout redds by smaller brown trout did occur, particularly below barriers to upstream movement. Mean water depth over redds selected by brook (24.0 cm) and brown trout (25.5 cm) were similar (P > 0.05). However, mean stream velocities were significantly (P < 0.001) slower at brook trout (17.6 cm/second) than at brown trout redds (46.7 cm/second). Average geometric mean sediment size of brook trout redds was significantly smaller than that of brown trout redds (5.7 mm versus 6.9 mm; P < 0.02), but less well sorted. Redd‐site preference by brook trout for areas of groundwater seepage and by brown trout for faster water velocities and coarser substrates minimized species interactions during spawning. Larger body size of mature brown trout (18.0–54.5 cm fork length) than of mature brook trout (8.4–29.0 cm) was probably a factor in the brown troutˈs ability to utilize faster currents where coarser gravels were found. Received December 3, 1982 Accepted August 5, 1983

Capacité de la méthode des microhabitats à prédire l'habitat de reproduction de la truite commune

“…La seconde hypothèse est d'ordre méthodologique. La granulométrie est, en effet, un facteur clé quant au choix du microhabitat de reproduction par la truite (SHIRVELL et DUNGEY, 1983 ;WITZEL et Mac CRIMMON, 1983). Ce facteur est parfois difficile à estimer.…”

Grays River Watershed and Biological Assessment, 2006 Final Report.

“…Factors influencing redd success include water flow and resultant water quality in the incubation environment and probability of redd scour, burial, or disturbance by later-arriving spawning individuals (Shumway et al 1964;Chapman 1988;. The ranges of habitat characteristics selected vary among species and individuals associated with differences in body size and therefore physical capability (Witzel and MacCrimmon 1983;Heggberget et al 1988;Kondolf and Wolman 1993;Fukushima and Smoker 1998). Because desirable habitat characteristics are temporally stable over short time frames, the locations of salmonid spawning areas may be somewhat static (Hoopes 1971;Fukushima 1994;Fukushima and Smoker 1998).…”

Etude du macrohabitat de reproduction de la truite commune (Salmo trutta L.) dans une rivière pyrénéenne, la Neste du Louron. Evaluation d'un potentiel de l'habitat physique de reproduction

“…La plupart des études soulignent l'importance de l'interface pool-radier en temps que macrohabitat de reproduction (STUART, 1953 ;WHITE et BRYNILDSON, 1967 ;REISER et WESCHE, 1977 ;WITZEL et Mac CRIMMON, 1983). OTTAWAY et al (1981) constatent sur la Teesdale (où les séquences pool-radier sont rares) que peu de truites fraient dans les queues de pools, et que les faciès utilisés ne peuvent en aucun cas être assimilés à des pools ou des radiers.…”

“…BAGLINIERE et al (1979), NIHOUARN (1983), WITZEL et Mac CRIMMON (1983 ont déjà souligné que les zones propices au frai sont surtout déterminées par la granulométrie. Cependant, l'utilisation de la granulométrie définie en classes n'est pas totalement satisfaisante lorsqu'on s'intéresse à la reproduction.…”

“…SHIRVELL et DUNGEY (1983) émettent l'hypothèse que la sélection du substrat se ferait par une sélection de la vitesse. De nombreuses études, relatives aux microhabitats, ont déterminé des préférenda de vitesses en dehors desquels peu de frayères étaient rencontrées (SMITH, 1973 ;REISER et WESHE, 1977 ;WITZEL et Mac CRIMMON, 1983 ;FRAGNOUD, 1987;etc.). On peut penser que les truites utilisent peu les faibles vitesses parce que le courant ne remplit plus son rôle d'aide à la formation de la frayère.…”