Meeting Abstract
Land use conversion can lead to decreased biodiversity and organismal health in freshwater habitats. Run-off from urbanized environments introduces pollutants and alters water temperature, chemistry, and hydrology in streams. The resulting “urban stream syndrome” affects the stress response of resident fishes by elevating or dysregulating the stress hormone, cortisol. We explored the consequences of land use conversion on baseline cortisol release rates, stress response (to agitation), resilience, and life-history plasticity of the Western Mosquitofish, Gambusia affinis, an abundant species which persists in urbanized habitats. We hypothesized that increasing urbanization, defined by the percent developed land within a 2.2 km radius of each site, will alter cortisol levels and affect life-history traits of female mosquitofish. We sampled fish from streams varying in levels of urbanization and measured water quality covariates in 2018 and 2019. In both years the dry brood mass of female mosquitofish increased with increasing urbanization. Cortisol release rates increased with increasing urbanization in 2018, but not in 2019. All streams showed stress response to agitation in both years. In 2019 none of the mosquitofish populations showed resilience indicating that they did not recover in one hour from a stressor. In urban populations as the magnitude of resilience decreases, dry brood mass increases but there is no such trade-off for the more rural populations. Further, we found that cortisol response was highly repeatable indicating an ability to respond to selection. Our findings suggest that mosquitofish are urban adaptors and modulate reproductive output in lower quality streams.
