Long-term trends of bull shark (Carcharhinus leucas) in estuarine waters of Texas, USA

Abstract

Increases in standardized catch per unit effort (CPUE) and mean length of bull shark (Carcharhinus leucas) were observed in coastal estuaries over a 35-year period (1976–2010). Trends in abundance and size were examined using fisheries-independent data from a long-term monitoring survey in Texas, USA. Catch, effort, and environmental covariates that affect bull shark distribution were used to create a standardized index of abundance. Increases in abundance and mean length were detected, potentially due to the initiation of federal management and restrictions on the use of gill nets in nearby Louisiana, USA, waters in 1995. This study provides a long-term perspective of two important demographic indicators (abundance and mean size) of bull shark and provides an encouraging signal in the Gulf of Mexico for a species whose stock status is unknown yet considered near threatened on the International Union for Conservation of Nature red list. Continuing research is needed to gauge effects of management and environmental impacts on shark resources as well as investigations into ecosystem effects of increasing predatory density in coastal waters.