Distribution and movements of brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in Lake Otamangakau, central North Island, New Zealand

Abstract

The post-spawning movements and distribution of 15 brown trout (Salmo trutta Linnaeus 1758) and 21 rainbow trout (Oncorhynchus mykiss Richardson, 1836) were monitored weekly between August 1996 and March 1997 in the hydro-electric reservoir, Lake Otamangakau, New Zealand, using radio-telemetry. The most frequently used areas were the vicinity of the main inflow and the channel running through the main body of the lake. After spawning, brown trout regained rapidly their usual habitat. Rainbow trout were using the inlet intensively before recolonising the main channel of the lake. Brown trout made greater use of the weedy parts of the lake and littoral margins, had a more confined home range, and were less mobile than rainbow trout. Rainbow trout occupied the main body of the lake by day, and moved nearer the surface, and closer to the margins, at night. High lake levels allowed brown trout to exploit wetland margins of the lake.

Seasonal age distributions and maturity stage in a naturalized rainbow trout (Oncorhynchus mykissWalbaum) population in southern Chile reveal an ad-fluvial life history

“…In accordance with our results, Soto et al (2002) reported, for our study lake-inlet system, a higher frequency of larger mature (and probably older) rainbow trout in the lake and its inlet streams from May to October, with a peak in July and August. Dedual et al (2000) reported similar results in New Zealand. Movements of rainbow trout from the lake into its inlet streams to spawn have also been described widely in the Northern Hemisphere (Behnke, 1992;Crawford, 2001), New Zealand (Rosenau, 1991;Dedual et al, 2000), but only in one study in South America, southern Argentina (Sakai and Espinos, 1994).…”

“…Dedual et al (2000) reported similar results in New Zealand. Movements of rainbow trout from the lake into its inlet streams to spawn have also been described widely in the Northern Hemisphere (Behnke, 1992;Crawford, 2001), New Zealand (Rosenau, 1991;Dedual et al, 2000), but only in one study in South America, southern Argentina (Sakai and Espinos, 1994). Also, the wide period of time during which older trout (probably the bulk of spawners) are present in the inlet streams may reflect a spawning period that extends until late spring.…”

“…Furthermore, it would indicate that the spawning occurs mainly in winter and spring as the frequency of age 0 + trout in streams peaks in summer. Some trout may start to disperse toward their spawning streams in the fall months before they spawn (e.g., Sakai and Espinos, 1994) and/or may also stay in the streams months after the completion of spawning (e.g., Dedual et al, 2000). As a consequence, older trout are not found along the shoreline of the lake during spring because they are probably still spawning or, if they are spent, they may be waiting for a freshet to push them back into the lake.…”

“…Rainbow trout (Oncorhynchus mykiss Walbaum) is one of the most popular game species that has been introduced all over the world (Crawford and Muir, 2008). Similar patterns of habitat use have been reported in both native and introduced populations, with adults using inlet streams to spawn and juveniles occupying streams as nursery areas before they emigrate to the lake (Youngs and Oglesby, 1972;Hayes, 1988;Rosenau, 1991;Seelbach, 1993;Sakai and Espinos, 1994;Graynoth, 1996;Dedual et al, 2000;Riva-Rossi et al, 2007). However, naturalized populations currently exist across a diverse array of habitats (Crawford and Muir, 2008).…”

Fish Stomachs as a Biomonitoring Tool in Studies of Invertebrate Recovery

“…The strength of the selection is affected by several factors, of which prey density, prey size, quality, catchability and learning (Allen, 1988;Dahl, 1998;Reiriz, Nicieza, & Brana, 1998;Salvanes & Hart, 1998;Sweka & Hartman, 2001;Warburton, 2003) are the most important. As a consequence of this, large nutrient-rich food items may be strongly selected (Dahl, 1915;Dedual, Maxwell, Hayes, & Strickland, 2000). A secondary effect of this may be strongly reduced prey densities (McNaught et al, 1999;Pechlaner, 1984).…”