Size and Age Structure of Anadromous and Landlocked Populations of Rainbow Smelt

Abstract

Rainbow Smelt Osmerus mordax are widely distributed in both anadromous and landlocked populations throughout northeastern North America; abundance, size at age, and maximum size vary widely among populations and life histories. In the present study, size at age, von Bertalanffy growth parameters, population age distributions, and precision and bias in age assessment based on scales and sectioned otoliths were compared between ecotypes and among populations of Rainbow Smelt. To compare the ecotypes, we collected spawning adults from four anadromous and three landlocked populations in Maine during spring 2014. A significant bias was identified in only one of four scale comparisons but in four of seven otolith comparisons; however, a comparable level of precision was indicated. Anadromous populations had larger and more variable size at age and von Bertalanffy growth parameters than landlocked fish. Populations were composed of ages 1–4; six populations were dominated by age-2 or age-3 individuals, and one population was dominated by age-1 fish. These data suggest the presence of considerable plasticity among populations. A latitudinal gradient was observed in the anadromous Rainbow Smelt, which may show signs of population stress at the southern extent of their distribution.

Received March 25, 2016; accepted November 16, 2016 Published online February 27, 2017

ACKNOWLEDGMENTS

We gratefully acknowledge the staff at the Maine Department of Marine Resources (MDMR) and MDIFW for assistance and coordination in the collection of anadromous and landlocked Rainbow Smelt. Additionally, we appreciate the generosity of graduate students at the University of Maine, who spent nighttime hours on the road in search of Rainbow Smelt and helped with the statistical analysis. We thank Stephen M. Coghlan Jr. and Donna L. Parrish for reviewing the manuscript. Support for this research was from the Department of Wildlife, Fisheries, and Conservation Biology at the University of Maine; the U.S. Geological Survey’s Maine Cooperative Fish and Wildlife Research Unit at the University of Maine; MDIFW; MDMR; and the Maine Outdoor Heritage Fund. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. This study was performed under the auspices of Institutional Animal Care and Use Committee Protocol A2013-02-04 at the University of Maine.