Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
John A. Musick
Eric J. HIlton
Longnose gar (Lepisosteus osseus) inhabit all of the major tributaries of Chesapeake Bay in Virginia, extending from fresh to estuarine waters. Literature concerning longnose gar from tidal environments is limited and this is study concerns important aspects of the life history (e.g., growth, reproduction, dimorphism, movements, and diet). Age, growth, and reproduction are important life history aspects for understanding the biology of fishes and may be affected by the environment in which an individual lives. This study found no differences in the age, growth, and fecundity parameters between longnose gar from tidal portions of Chesapeake Bay tributaries and previous studies in non-tidal environments. Fecundity averaged 30,000 eggs and a von Bertalanffy growth model described growth of longnose gar to be sexually dimorphic, rapid in the first year of life, and leveling off after maturity. Sexual dimorphism has been documented previously in two species of the family Lepisosteidae, L. osseus and L. oculatus. The present study expands upon previous work on this species by examining a broader array of morphometric characters, while removing the bias associated with overall body length. A stepwise discriminant function analyses found that five characters best distinguish the sexes: head width, mid-snout width, anal-fin height, anal-fin width, and prepectoral-fin length. Discriminant function analyses with the five characters and standard length yielded misclassification rates of 8.8% and 6.2% for females and males, respectively. Another goal of this project was to characterize the movements of longnose gar by using both acoustic and conventional tagging methods and by examining historical catch records from a trawl survey. Two individuals moved 69 and 74 km, which is greater than the distance observed in the only other report on long-distance movement by longnose gar individuals. Spawning data were collected from two acoustically tagged longnose gar and spawning residency time was approximately one month. Winter distributions of longnose gar, previously unknown, occurred both inshore and mid-channel and were similar to the summer and fall. Finally, this study characterized the diet of longnose gar inhabiting tidal rivers in Virginia. The top five prey types recovered from stomachs were white perch, menhaden, killifishes (Fundulus spp.), Atlantic croaker, and spot. Marine and anadromous fishes (%W = 59.4%) and resident fishes (%W = 40.6%) were equally important in the diet of longnose gar. The diet varied with the seasonal prey fish assemblages, longnose gar length, and salinity, reinforcing the categorization of the species as an opportunistic predator. The relative abundance, rapid growth, and high fecundity of this apex predator warrant further study and inclusion into ecosystem models.
© The Author
McGrath, Patrick E., "The life history of longnose gar, Lepisosteus osseus, an apex predator in the tidal waters of Virginia" (2010). Dissertations, Theses, and Masters Projects. Paper 1539616772.