Effects of large-scale anthropogenic development on juvenile lemon shark (Negaprion brevirostris) populations of Bimini, Bahamas

Abstract

The waters around Bimini (25° 43.70′ N, 79° 18.00′ W) provide an ideal nursery location for juvenile lemon sharks, Negaprion brevirostris, but this habitat is threatened by the development of a large resort. Since 1999 the North Sound (NS) has been subjected to intermittent periods of dredging, the most intensive of which was in March 2001. Possible effects from the development up to June 2006 were investigated by: comparing growth rates of juvenile lemon sharks in the NS, Sharkland (SL) and South Bimini (SB) nurseries between 1995-2005 using before-after, control-impact (BACI) analysis; analyzing survival of juvenile lemon sharks in the NS and SL between 1995–2006; and by comparing habitat structures in the NS and SB nurseries in 2003 and 2005. BACI analysis detected no statistically significant difference between the growth rates of juvenile lemon sharks in the three nurseries before and after the impact date of March 2001. However, a reduction in the survival rate of juvenile lemon sharks in the NS after March 2001 was statistically significant, including a 23.5% decline in first-year survival. Habitat structure of the NS in 2003 and 2005 also varied with the mean percentage cover of the seagrass Thalassia testudinum declining by 17.7% since 2003. Our results indicate a correlation between the development thus far and a decline in the survival rates of juvenile lemon sharks and changes in the habitat structure of the NS. To elucidate further information regarding potential effects of the resort development on juvenile lemon sharks in the NS nursery, we suggest several future research directions.