Does the Refuge Availability Influence the Spawning Behavior of Mature Male Parr in Salmonids? A Test in the Miyabe Charr

Abstract

In many salmon and charr, both 'migratory males' and 'precocious males' are maintained as alternative life-histories within a population. During breeding, precocious males gather around the mating pair of migratory fish and attempt to sneak in the spawning between larger male and female charr. Refuges such as debris and shallow areas may provide shelter from aggressive attacks and allow precocious males to hold positions closer to the pair (nest) and/or sneak more easily during the mating. Here we examine whether the availability of refuges influences the breeding behavior of precocious male parr of the Miyabe charr under experimental and natural conditions. Aggressive attacks directed toward precocious parr by the mating pair or other parr was not influenced by the refuge availability either under experimental conditions or in the wild. We did not find the effect of high refuge availability on the proximity of parr to the nest beyond the experimental conditions where the density of refuges was probably higher than in the natural stream. There were no effects of high refuge availability either on parr's attempts at sneak mating or on their success in spawning. Thus, our results provide little evidence that the refuge availability influences parr sneaking behavior. Other possible effects of high refuge availability, for example, the increase of fertilization success and the decrease of energy expenditure and risk taking, remain to be considered.