Reproductive Ecology of Top Mesopelagic Predators in the Gulf of Mexico

Dragonfishes (Family: Stomiidae) are dominant mesopelagic predators occurring throughout the world’s oceans. Stomiids are ecologically important because they are trophic mediators, preying primarily upon lanternfishes, which are major zooplanktivores. While aspects of stomiid feeding ecology have been quantified, little is known regarding their reproductive ecology. A key reason is insufficient sample sizes of mature adults due to the type of gear used; larger, sexually mature stomiid adults are more adept at net avoidance. Between 2010-2011, the Offshore Nekton Sampling and Analysis Program conducted sampling in the northern Gulf of Mexico using a discrete-depth sampling system (MOCNESS) and a large, commercial-sized midwater trawl. Gonads were dissected from 714 individuals belonging to 47 species, 12 of which were deemed abundant enough for detailed analysis. Eleven of the 12 species had sex ratios that did not significantly differ from a 1:1 male:female ratio. Females possessed an asynchronous oocyte development, suggesting that females are iteroparous, protracted spawners. Males exhibited a similar pattern. Length frequency distributions and sizes at maturity of each sex of the 12 species will be presented. Data such as these are essential for ecosystem-based modeling of global deep-pelagic ecosystems, which contain the overwhelming majority of earth’s fish biomass.