Population Structure of a Neotropical Migratory Fish: Contrasting Perspectives from Genetics and Otolith Microchemistry

Abstract

Developing conservation strategies for migratory fishes requires an understanding of connectivity among populations. Neotropical rivers contain diverse and economically important assemblages of migratory fishes, but little is known about the population biology of most species. We examined the population structure of Prochilodus mariae, an abundant migratory fish species found in Venezuelan rivers that plays essential roles in both regional fisheries and ecosystem dynamics. By coupling otolith microchemistry and microsatellite genetic analyses, we were able to evaluate both natal origins of individual fish and genetic structure on a regional level. The chemistry of otolith cores inferred separate breeding grounds for four of six populations, with 75–85% of individuals from each river sharing a natal signature that is distinct from the other populations. In contrast, we detected no genetic structure, indicating that gene flow among these rivers prevents population differentiation. These disparate inferences underscore the complexity of conserving migratory species; otolith data suggest that ensuring fishery sustainability requires recognizing distinct breeding stocks, while gene flow reflects the importance of connectivity across the broader river network on an evolutionary time scale. We conclude that multiple methodological approaches may often be necessary to fully understand the spatial ecology and management needs of migratory fishes and, therefore, also influence local management practices.

Received June 8, 2012; accepted May 1, 2013

ACKNOWLEDGMENTS

Support for this research was provided by grants from the National Science Foundation (DEB-0321471, INT-0321443) and the Cornell Chapter of Sigma Xi. Junnior Figueredo, Oscar Leon, and Carmen Montaña provided assistance with field collections. Steve Bogdanowicz, Laura Stenzler, Amanda Talaba, Chris Markareowich, and Irby Lovette assisted with genetic laboratory work. Claire Ingel assisted with mapping the study sites. Willie Fetzer, Joe Simonis, Chris Dalton, Nelson Hairston Jr., the Flecker laboratory group, and four anonymous reviewers provided helpful comments on the project and manuscript.