Teleost fishes exhibit an unrivaled diversity of reproductive patterns compared to other vertebrates, and the groupers (Epinephelidae) and seabasses (Serranidae) represent an extreme example of this diversity, because significant variations in sexual pattern, mating behavior, and reproductive anatomy occur among species in both families. For this research, I investigate these three aspects of the reproductive biology in five species of groupers from the eastern Pacific. I then combine my data with published results on the reproductive biology of other groupers and seabasses to describe taxonomic differences in these aspects and reconstruct their evolutionary history. Finally, I use a comparative phylogenetic approach to evaluate the evolutionary relationship between mating system characteristics (i.e., mating group structure and sperm competition) and sexual pattern. More specifically, I test whether evolutionary shifts in sexual pattern and, in particular the loss of sex change, were influenced by changes from paired to group spawning and associated increases in sperm competition among males. These analyses allow me to determine whether predictions of sex-allocation theory regarding the influence of mating behavior on sex allocation are congruent with fine-scale, evolutionary patterns of sex change within a resolved phylogeny.

My results indicate that characteristics of the sexual pattern, mating behavior, and reproductive anatomy in both families are exceptionally labile. Evolutionary transformations in these features do not strictly follow taxonomic lines and remarkable changes have evolved in closely related species and genera. The most parsimonious phylogenetic reconstructions of the evolutionary history of sexual patterns indicate that protogynous hermaphroditism is the ancestral character state in both the Epinephelidae and the Serranidae, and other forms of hermaphroditism evolved secondarily from this state. Tests of correlated evolution showed that evolutionary transformations in sexual pattern from protogyny to gonochorism are correlated with transformations in mating group structure from paired to group spawning, and sperm competition is significantly higher in gonochoric species than protogynous species. These results suggest that the loss of sex change was influenced by changes from paired to group spawning and associated increases in sperm competition among males. More importantly, this research provides phylogenetic support for predictions of the size-advantage model and empirical evidence for the influence of sperm competition on sex allocation in animals.

Sounds produced by fishes during reproductive periods are increasingly being discovered, highlighting the importance of acoustic communication within courtship and spawning behaviors across a diverse assemblage of fishes. While researchers have increased monitoring efforts of fish sounds to infer spatio-temporal patterns of spawning, habitat use, and abundance, a lack of knowledge about the relationships between recorded sounds, reproductive behaviors, and abundance has impeded progress in exposing the utility of fish sounds for understanding the reproductive biology and dynamics of regional populations.

This dissertation assesses the biological importance of sound production in Gulf grouper (Mycteroperca jordani) and Gulf corvina (Cynoscion othonopterus) and provides evidence that levels of fish sounds are indicative of reproductive activity and abundance. Long-term recordings of Gulf grouper sounds were coupled with observational data and acoustic propagation modeling to describe the mating system and acoustic behaviors of the species. Gulf grouper conformed to a protogynous life strategy and lek mating system with large males that established fixed territories, courted individual females, and pair spawned. Males produced sounds during courtship behaviors and spawning rushes that may have functioned to express fitness to prospective mates; this is the first account of sounds accompanying spawning in groupers. Rates of sound production were statistically related to measures of female abundance and reproductive activity, indicating that fish sounds can be used as estimators of relative reproductive activity and abundance of both sexes outside of observations. Mobile echosounder and passive acoustic surveys of the spawning aggregation site of Gulf corvina documented the sounds, spatial distribution, and abundance of aggregated fish. The site supported up to 1.55 million fish that contributed to a 21-fold increase in ambient noise levels through collective chorusing of the loudest fish sound yet to be documented, warranting future conservation and appreciation of acoustic communication in fishes. A predictive relationship between acoustic levels of chorusing and estimates of density was found, demonstrating that sound levels may be used to estimate the density of soniferous fishes at aggregation sites. In summary, my dissertation advances our understanding of the importance of sounds within reproductive behaviors and identifies future opportunities for improved population monitoring.