Age, Growth, and Reproduction in Two Coastal Populations of Longnose Gars

Meredith Smylie,Virginia Shervette,Chris Mcdonough

doi:10.1080/00028487.2015.1111256

Abstract

AbstractMeasurements of age, growth, and reproduction are excellent tools for determining the ecological role and impact of a species within an ecosystem. Longnose Gar Lepisosteus osseus is a large, ubiquitous top predator in fresh and saline waters of the eastern United States. Even though the species is common, their basic biology has been largely uncharacterized in brackish and marine waters. Specimens were collected from two estuaries: Winyah Bay and Charleston Harbor, South Carolina, from May 2012 through July 2013 to examine age, growth, and reproduction in tidally influenced systems. This species is fairly long‐lived, with maximum ages of 17 and 25 years for males and females, respectively. The von Bertalanffy growth model yielded significantly higher growth rates for males than for females. Reproductive histology and the gonadosomatic index indicated that Longnose Gars exhibit determinate fecundity and spawn in late spring following a long development period during fall and winter. These life history parameters provide valuable insight into the basic biology of Longnose Gars and into how they function in estuarine environments. Further research on the precise timing and location of spawning movement, as well as daily movement patterns of this species, would provide a more comprehensive knowledge of Longnose Gar reproductive biology.

Highlights

South Carolina Department of Natural Resources, Marine Resources Division, 217 Fort Johnson Road, Charleston, South Carolina 29422, USA
Age and Growth Longnose Gars were relatively abundant in the two estuarine systems we examined
In coastal South Carolina estuaries, Longnose Gar abundance has remained relatively stable over the past decade (SCDNR, unpublished monitoring data) and they are the sixth most abundant species collected by the South Carolina Department of Natural Resources (SCDNR) Inshore Fisheries monitoring efforts

Summary

Introduction

Specimens were collected from two estuaries: Winyah Bay and Charleston Harbor, South Carolina, from May 2012 through July 2013 to examine age, growth, and reproduction in tidally influenced systems This species is fairly long-lived, with maximum ages of 17 and 25 years for males and females, respectively. Reproductive histology and the gonadosomatic index indicated that Longnose Gars exhibit determinate fecundity and spawn in late spring following a long development period during fall and winter. These life history parameters provide valuable insight into the basic biology of Longnose Gars and into how they function in estuarine environments. We wanted to do the following: (1) document population age structure and growth rates using sagittal otoliths, (2) describe reproductive phases of males and females using histological techniques, (3) quantify sex-specific monthly changes in the gonadosomatic index (GSI), and (4) quantify female potential annual fecundity

Objectives

Methods

Results

Conclusion