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BACKGROUND: The widespread occurrence of feminized male fish downstream of some wastewater treatment works has led to substantial interest from ecologists and public health professionals. This concern stems from the [...]

A comparative analysis of sperm competition and sex change across fish species was carried out. The results confirm the hypothesis that female-biased sex ratios and risk of sperm competition are evolutionary correlates of female-first sex-change.

A bidirectional pattern of male trait evolution and sensory trade-off signal divergence in surfperch are investigated. It is shown that sensory systems with trade-offs in detection abilities produce bidirectional biases and that signal design properties match these biases.

Research into genetic mating and biological parentage has revealed that some 70-95% of offspring is parented by nest-guarding fish, while around 33% of nests are cuckolded.

Individual differences in attractiveness were incorporated into the theory of condition-dependent sexual selection in a study of courtship behavior of guppies. Large attractive males reduced their courtship under high light levels, supporting the differential cost hypothesis rather than the differential-benefit hypothesis for correlations between sexually selected traits. Bright lights might have exposed large males to predator risk. The discovery that changing environmental conditions can alter the distribution of individual male mating success in guppies has implications for the co-evolution of female choice and sexually selected traits.

Female sand goby fish display significantly lower levels of mate-choosing behavior in the presence of predation threats by codfish. Observations show that searching for a mate increases predation risk and is therefore reduced by the female sand goby who otherwise indulges in extensive mate searching behavior. This observation can be generalized to other species as well. Various explanations can be offered for the restriction of searching behavior such as increased exposure, stress and suppression of spawning instincts during predation threat.

Alternative mating strategies are common in nature and are generally thought to increase the intensity of sexual selection. However, cuckoldry can theoretically decrease the opportunity for sexual selection, particularly in highly polygamous species. We address here the influence of sneaking (fertilization thievery) on the opportunity for sexual selection in the sand goby Pomatoschistus minutus, a marine fish species in which males build and defend nests. Our microsatellite-based analysis of the mating system in a natural sand goby population shows high rates of sneaking and multiple mating by males. Sneaker males had fertilized eggs in [approximately equals] 50% of the assayed nests, and multiple sneakers sometimes fertilized eggs from a single female. Successful males had received eggs from 2 to 6 females per nest (mean = 3.4). We developed a simple mathematical model showing that sneaking in this polygynous sand goby population almost certainly decreases the opportunity for sexual selection, an outcome that contrasts with the usual effects of cuckoldry in socially monogamous animals. These results highlight a more complex and interesting relationship between cuckoldry rates and the intensity of sexual selection than previously assumed in much of the literature on animal mating systems. microsatellites | mating systems | paternity | polygyny

Issues concerning the reproductive behavior of fishes are discussed, including sexual and social relationships, along with competitive and cooperative behaviors.