Overlapping Habitat Use of Multiple Anadromous Fish Species in a Restricted Coastal Watershed

Abstract

The purpose of this study was to document timing and habitat of alosines (Hickory Shad Alosa mediocris, American Shad A. sapidissima, Alewife A. pseudoharengus, and Blueback Herring A. aestivalis) and Striped Bass Morone saxatilis in the lower Tar River, a North Carolina coastal watershed partially restricted by an unused industrial dam. Alosines and Striped Bass are usually separated in time or space during spawning activity but occasionally overlap in some systems. Results show that both eggs and larvae of Hickory Shad and Striped Bass predominated catches, followed by American Shad. Alewife and Blueback Herring had negligible catches of eggs and larvae, but a separate study conducted 48 river kilometers downstream of the study area collected larvae of both species. Eggs and larvae of target species overlapped spatially and were most abundant in downstream tributaries, which seasonally reached hypoxic to anoxic conditions. The origins of spawning are unknown, but the collection of eggs suggests that these low-velocity tributary habitats are used for spawning and are acceptable for survival, possibly even providing egg and larval refuge from predators. Eggs and larvae of target species, except Blueback Herring, were collected at the furthest upstream sampling location, which suggests that the dam was restricting upstream migration and habitat use. If the dam was to be removed or modified for fish passage, future studies could document how these species utilize and separate into the upstream habitats that once served as historical habitats for these species. Climate change and associated sea level rise, combined with habitat restriction from the dam, may affect how these species utilize the lower Tar River as time moves forward.

Received August 28, 2013; accepted July 13, 2015

ACKNOWLEDGMENTS

We appreciate the Institute for Coastal Science and Policy, and Department of Biology, at East Carolina University for logistic support, travel, and field and laboratory equipment. We also thank the U.S. Fish and Wildlife Service for project funding (Grant 520101) during the 2005 field season.