Otolith based growth indices of Atlantic croaker as indicators of environmental quality

Juvenile Atlantic croaker (Micropogonias undulatus) were sampled from four estuarine systems to determine whether otolith based indices of their juvenile growth reflected the environmental quality in areas of their capture. Otolith weight was used as an indicator of long term growth and the width of marginal micro-increments as an indicator of recent growth rate. Sampling of the severely impacted Houston Ship Channel in Galveston Bay showed increased severity of fin disease and a progressive decline in indicators of long and short-term growth rate as levels of pollution increased along an upstream gradient. Otoliths of croaker from the most polluted site were about 25% heavier and had micro-increments 75% the width of otoliths of croaker from the least impacted site. Subsequent sampling of upstream and downstream sites in three rivers of the more moderately impacted Charleston Harbor, also indicated that growth was correlated with environmental quality. The long term growth index indicated that there was no difference between upstream and downstream areas within a river but that growth differed between rivers. Croaker from the river with the highest water quality designation had the most rapid growth. Sampling of Pensacola and Choctawhatchee Bays, Florida, also revealed differences in croaker growth which generally agreed with what we know of the environmental quality of the sampling areas. Our results indicate that otolith based indices of growth are correlated with water quality and that growth of Atlantic croaker may provide a measure of estuarine habitat quality along the South East Atlantic and Gulf Coasts of the U.S.A