Movement patterns and home ranges of a pelagic carangid fish, Caranx crysos, around a petroleum platform complex

Abstract

Quantification of the movements and home ranges of highly mobile marine species is a challenging prerequisite for a more complete understanding of their ecology. Caranx crysos is a pelagic carangid found in large schools over the mid-shelf of the northern Gulf of Mexico. Twenty- three C. crysos were surgically implanted with acoustic transmitters, and their positions were local- ized around a petroleum platform complex in the Gulf of Mexico using a hydrophone network. Fish were tracked during August 2005 for 23 d, and home ranges were calculated for individual fish over the daily, diel, and entire study period. Most fish showed a preference for a discrete area within the platform complex: 11 fish had a range centroid near one platform for at least 7 d, and 9 fish had a range centroid near one platform for at least 3 d. Only 3 fish showed no preference for a particular site within the platform complex. Mean core daily range varied from 373 to 2202 m 2 , while the 95% daily range was between 3082 and 14 333 m 2 . Evidence for diel differences in habitat use was also apparent. Hydrophones detected more transmissions during the day than during the night; however, only 3 fish had significantly larger home ranges during the day than during the night. There was a significant correlation between fish length and both the size of their overall core home range and the size of the 95% daily home range. Our results suggest that this schooling pelagic species establishes a home range in the vicinity of structure.