Variation of reproductive behaviour and success of males adopting different tactics in Atlantic salmon

Six males and five females anadromous Atlantic salmon were released in two sections of the Lapitxuri experimental stream (Southwest France), where they could reproduce naturally. Females had all the same size and age, contrary to males. We focussed our attention on the variation with time of spawning tactics and success of males. Two factors affected male spawning behaviour in the short term. An increase of the OSR increased the level of male competition around redds which resulted in a larger number of males adopting sneaking rather than fighting tactics. Changes in female activities also seemed to be detected by males, since male aggressiveness increased when females were close to oviposition. But whatever their activities, males preferentially courted the earlier spawning female when two females were active at the same time. Fighting in males was confirmed to be the most successful tactic at a given time. However, males adopting sneaking tactic at the beginning of the spawning season could dramatically increase their reproductive success in the long‐term. Fighting males invested much more energy in contests than secondary males, which may constitute a handicap in terms of longevity. They could quickly lose their status or strength with time which, although placed in a situation of high OSR, resulted in greater numbers of previously low‐ranking males adopting satellite and fighting tactics during the period preceding oviposition. Age more than size affected male status and reproductive success. Females seemed to select their mate directly in relation to their physiological condition, since they only attacked dull coloured males showing obvious wound marks. They also could indirectly choose their mate by repeatedly leaving the redd during the period preceding oviposition in a situation of high OSR. This behaviour might incite male competition and also promoted, by incessant attempts of secondary males to rob the more successful status of primary males, their chance to spawn with fitter males. These results emphasized the importance of environment, physiological condition and energy expenditure in allocation tactics and variations in salmon reproductive success throughout the spawning season. This led us to hypothesize that the choice of sneaking through conditional strategies might provide greater average fitness in salmon alternative life histories.