EAPSI: Determining the Response of Migratory Fish to Environmental and Climatic Variability

Ballew Heidi E, Rockport TX

Investigators

Abstract

This research will be completed in collaboration with leading fish migration expert, Dr. Gerard Closs at the University of Otago, and will identify factors and conditions influential to the success of migration in fishes. The implications of this study can be drawn broadly to understand the factors that influence migratory species under rapidly changing environmental and climatic conditions which will be foundational in determining future population dynamics of, often threatened, migratory fishes and will provide information for conservation and management of these threatened populations. Climate variability can influence the nutrients available in freshwater and marine aquatic systems which can subsequently affect the success of migratory organisms to move between those two environments, called diadromy. Additionally, stream flow can be influenced by climatic/environmental variability directly influencing the success of migratory individuals. In this study, we will evaluate how climatic processes, like El Niño, affect stream flow and marine and freshwater nutrient availability to determine if migration success is influenced in two migratory fish species, Gobiomorphus cotidianus and Galaxias argentius. This study will evaluate samples collected from streams representative of varying stream flow and nutrient productivity and will use MODIS satellite images to determine how changes in nutrient availability in the marine environment might influence migration success. Climate variability can affect the productivity of freshwater and marine systems influencing the success of aquatic migrants between those systems (i.e., diadromy). Migratory success can fluctuate in response to variable environmental conditions such as stream flow or productivity. The primary hypothesis of this study is that climate variation (i.e., El Niño) alters the success of migrants and residents by affecting stream flow regimes and marine and freshwater productivity by sampling two diadromous species, Gobiomorphus cotidianus and Galaxias argentius along stream flow and productivity gradients. Otolith microstructure and microchemistry analysis will be used to determine the rate at which individuals migrate from freshwater streams to marine environments under different climatic conditions (ENSO index). MODIS satellite images will be used to analyze the influence of coastal productivity on migration propensity across a nutrient/productivity gradient while land use/land change satellite imagery will be used as proxy for stream productivity to determine migration rate dynamics across a terrestrial nutrient gradient. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Royal Society of New Zealand.