Biotic and Abiotic Influences on Nest-hatching Outcome in the Japanese Fluvial Sculpin, Cottus pollux

Size-mediated dominance and aggressive behavior of male Japanese fluvial sculpin Cottus pollux (Pisces: Cottidae) reduce nest-site abundance and mating success of conspecific rivals

“…Males with larger body size are often advantageous for the acquisition of nests through male-male competition and subsequent female mate choice (Andersson 1994), and this trend is consistent with several freshwater sculpin species (Brown and Downhower 1982;Goto 1987;Natsumeda 1998bNatsumeda , 2005. Although we could not entirely rule out the effects of male-male competition on female mate choice in our experimental design (see review in Karino 1996), our results indicated that the model incorporating male body size, nesting rate before addition of females, and the number of courtship attempts on females was adopted to explain male mating success.…”

“…large-bodied early spawners and small-bodied late spawners in one breeding season), but few males take part in both breeding activities (Natsumeda 2005), implying their semelparious reproductive lifespan (see Stearns 1992). Smaller mature males of the species may adopt two alternative reproductive tactics: they delay reproduction until late phase of the breeding season with small body size, or postpone reproduction for another year, invest energy in growth during that time, and consequently take part in reproduction in the early phase of the next breeding season with a larger body size (Natsumeda 1998a(Natsumeda , 2005(Natsumeda , 2007. Thus, smaller males of the species had few opportunities of nesting and subsequent reproduction where larger conspecific males were present nearby.…”

“…In this population, breeding took place from mid-February to early May, and they showed apparent sexual-size dimorphism (males are larger than females) (Natsumeda et al 1997). In the field observations, larger males acquired nests by outcompeting smaller males and achieved greater mating success than smaller males over a single breeding season (Natsumeda 1998b(Natsumeda , 2005.…”

“…They exhibit typical resourcedefence polygynous mating patterns in their natural habitat: larger males successfully acquire larger nest rocks through male-male competition and achieve greater mating success than smaller males in a single breeding season (Natsumeda 1998a(Natsumeda , 2001(Natsumeda , 2005. On the other hand, the number of nests actually used by males was only 11.1% of potentially suitable nest resources, i.e., rocks larger than 30 cm in diameter with a cavity ([10 cm in depth; Natsumeda 2001).…”

Population trends and current status of the endangered Pyrenean sculpin Cottus hispaniolensis in the Spanish part of the Garonne drainage

“…3) showed a simplified structure, dominated by fish from 85 to 135 mm FL, and the 0þ class (<50 mm) was very scarce. The spate occurred in sculpin spawning time (spring) and could damage the nests or flush down the newly hatched fry (Natsumeda, 2005). In 2015, the 0þ class was also scarce probably because of a small stock of mature individuals in the reproductive season.…”