Characterizing Bull Shark (Carcharhinus leucas) Assemblages Near the Sabine Pass Inlet

Abstract

The developmental stages of bull shark (Carcharhinus leucas) life history and the impact of selected environmental variables on the utilization of a Gulf of Mexico habitat by this species were characterized during late spring through summer 1992-1999, Entanglement nets 91.4 min length of varying depth (2.40--4.88 m) and mesh sizes (12.7-25.4 em) were deployed adjacent to jetty and beachfront sites near Sabine Pass. Bull sharks (N = 720) were incidentally captured as part of a study to monitor the population of Ridley sea turtles. The bull shark bycatch portion of the parent study data was expanded in 1997-1999 to record sex and in 1999 to include total length (TL) of individual bull sharks. Bull shark life history stages were estimated for the 1999 study from length and sex. Bull shark TL data when evaluated using size ranges of the Final Fisheries Management Plan for Atlantic Tunas, Swordfish, and Sharks indicate that no adult sharks were captured. Total length frequency compared to generally accepted length at age data supports that 94% of the Sabine Pass captures would be at most 6 yr old. A strongly correlated power model (r2 = 0.91) extended the length-weight relationship data for immature life history stages of bull sharks. Bull shark catch (1992-1999) was positively correlated with water temperature (20.0--40.0°C), salinity (12.3-34.8 parts per thousand), and water clarity (0.0-1.6 m) and inversely correlated with dissolved oxygen (4.4-9.1 mg/liter). The findings suggest that the area surrounding Sabine Pass functions as a nursery I development area for early life-history stages of bull sharks during late spring and summer months when specific environmental factors are present.