Life History Traits of the Florida Sand Darter Ammocrypta bifascia, and Comparisons with the Naked Sand Darter Ammocrypta beani

Abstract

The life history of Ammocrypta bifascia was studied using collections taken from five localities in the Blackwater River drainage, Okaloosa and Santa Rosa counties, Florida, between 1974 and 1977. Ammocrypta bifascia reproduced from April-July or early August. All females were sexually mature by 38 mm SL; and by 43 mm SL, all males were mature. Adult males were significantly larger than adult females. The number of mature ova in 10 females 39.5-52.5 mm SL ranged from 19-85 and was highly correlated with female size. Mean mature ovum diam for nine females were 0.88-1.24 mm (x= 1.08?0.04 mm); individual ova were 0.80-1.33 mm diam. There was no significant correlation between mean female ovum diameter and SL. The maximum life span was ca. 3 years. Individuals matured at about 1 year. Comparisons were made with Ammocrypta beani based on previous work. Ammocrypta bifascia from the Blackwater River drainage of Florida differed from A. beani from the Jourdan River drainage of Mississippi in a number of life history traits. Ammocrypta bifascia matured at a larger size, attained a larger size, reproduced for a shorter period of time, and lived longer. Ammocrypta btfascia females produced fewer but larger ova. INTRODUCTION Published data on the natural history of the Florida sand darter Ammocrypta bifascia are scarce. Williams (1975) provided limited information on the life history of A. bifascia when he described the species. He also discussed the distribution, habitat and common species associates. Bailey et al. (1954) described the habitat and species associates of A. beani ( = A. bifascia) in the Escambia River drainage, Florida. There is no other published information on the natural history of A. bifascia. Herein I present a study of the life history of A. bifascia and compare life history traits of A. bifascia and A. beani based on previous work (Heins and Rooks, 1984). Ammocrypta bifascia is a member of the beani species group in the subgenus Ammocrypta (Williams, 1975; Page, 1981). It occurs in streams of the Gulf Coastal plain of southern Alabama and northwestern Florida from the Perdido River drainage E to the Apalachicola River system (Williams, 1975; Starnes and Starnes, 1979). Ammocrypta bifascia typically is collected in moderate to large streams with shifting sand substrates in moderate current at depths of 2-4 ft; however, it also may be taken in small streams, in streams with swift current, and at depths between 6 inches and 5 feet (Williams, 1975). MATERIALS AND METHODS Collections of Ammocrypta bifascia were taken from five localities in the Blackwater River drainage, Okaloosa and Santa Rosa counties, Florida. The Blackwater River was sampled at two locations. Big Coldwater Creek and the East and West Forks of Big Coldwater Creek each were sampled at one location. The collections were made from 1974-1977 with a 3-m long, 4.8-mm Ace-mesh seine. Specimens were preserved in 10% formalin and stored in 43% isopropyl alcohol. Collections of A. bifascia are deposited in the Florida State Museum at the University of Florida. Climatic and daylength records for the nearest recording stations (Milton Experiment Station and Pensacola, Fla.) were obtained from the National Climatic Center, Asheville, North Carolina, and the Naval Observatory, Washington, D.C., respectively.