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UBC Theses and Dissertations

Effects of variability in space and time on the production dynamcis of salmonid fishes Tautz, A. F.


Detailed studies of the spawning behavior of chum salmon (Oncorhynchus keta) and rainbow trout (Salmo gairdneri) in laboratory-flumes were conducted. The behavioral activities, quivering, probing, and crossing over increase in frequency as a function of time prior to spawning whereas digging remains constant or decreases slightly. Maps of digging locations and movie films suggest nest shape and current pattern are monitored by the female, allowing her to intensify her digging activity near the center of the nest. Probing appears to be a signal to the male indicating approach of oviposition and also provides information to the female regarding the space and suitability of the nest site. The probing act is also used in the synchronization of the male and female spawning acts. Changes in velocity do not appear to markedly affect nest construction either in terms of number of digs to ovipoistion or in size of nest constructed. It is inferred that velocity and gravel size are important insofar as they influence the construction of a suitable nest depression. Nest sites would appear to be selected on the basis of acceleration of flow rather than velocity per se though high limits must obviously exist. Simulation studies, field observations of sockeye salmon (Oncorhynchus nerka) spawning in spawning channels, and laboratory studies were used to estimate optimal spawning densities for salmonids. Optimum density was found to be a function of redd size, territory size, temporal distribution of the run and ocean survival rate. Pattern of territorial defense in sockeye is consistent with maximizing protection of the redd from superimposition, and provides a quantitative value for the benefits of territorial behavior. A comparison of the theoretical optimum with current operating channels indicates a possible over-escapement of up to 50 percent, representing a substantial annual commercial loss to the fishery.

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