Male social dominance affects access to mates but not female mate choice in a livebearing fish

Male-male competition and female mate choice are often assumed to act in concert, with male social dominance serving as a reliable cue in female choice reflecting overall male quality. However, few studies have explicitly disentangled the effects of male competition and female mate choice, leaving gaps in our understanding of how these processes interact to shape male fitness. Here, we experimentally separated the effects of male-male competition and female mate choice in the pygmy halfbeak Dermogenys colletei, a small freshwater fish, to test whether i) male social dominance drives access to females in the presence and absence of direct male-male competition, and ii) females prefer socially dominant males. Our results show that dominant males monopolized access to females, spending more time courting females and engaging in more courtship behaviors. Additionally, female halfbeaks did not show a preference for dominant males, providing no evidence that females use male dominance when assessing males. Overall, these findings highlight that when male-male competition facilitates mate monopolization there may be less scope for pre-copulatory female mate choice.