Visual signals in the spawning behaviour of rainbow trout
Aspects of the behaviour of sexually mature rainbow trout, when mimicked by fishlike wooden models on spawning beds, induced displays of reproductive behaviour in males of the species. The total amount of male reproductive behaviour, and the amounts of posturing, gaping, and spawning elicited in tests were significantly correlated with the rank of tests arranged in descending order of priority, from those that most accurately depict the reproductive behaviour of a female rainbow trout to those that least accurately depict it (Spearman's rank correlation coefficient for total amount of male behaviour is ρ = −0.867, P < 0.01, N = 12. For posturing, gaping, and spawning, ρ = −0.7143, −0.9524, and −0.8690, respectively, P < 0.05, 0.01, and 0.01, N = 8). Sex recognition is governed largely by the distance of the model above the gravel. Males courted static models stationed 0 and 5 cm above the gravel, attacked a fusiform model stationed 10 cm above a flat gravel bottom, and attacked and courted the same model stationed 10 cm above a nest. Signals that induced posturing included the model's proximity to the gravel, and the action of a puppet, which was capable of movement, settling down into the nest, or onto the gravel. The puppet's action of rising up off the gravel terminated posturing.