Development of Young Bluefish (Pomatomus saltatrix) and Distribution of Eggs and Young in Virginian Coastal Waters

Abstract

Cruises were made off Chesapeake Bight from December 1959 through April 1963 to determine species composition and distribution of fishes spawned on the Continental Shelf. Illustrations of young fish, herein provided, now complete figures from newly hatched larvae to juveniles. Verbal descriptions provide prominent features of young bluefish to aid in identification and osteological development and to compare similar appearing larvae. Bluefish larvae can be distinguished from similar appearing species (Peprilus triacanthus and Urophycis chuss) with which they were taken in Chesapeake Bight by myomere numbers and pigment patterns. Bluefish larvae closely resemble the larval scombrids, Scomber scombrus and S. japonicus, and larval carangids. They may be separated by myomere numbers or relative lengths of the preopercular spine. Continental Shelf waters off the Virginia-North Carolina coast are major spawning grounds of bluefish. Major spawning sites in the Chesapeake Bight were located over the outer half of the shelf between 55 km (30 nautical mi) and 148 km (80 nautical mi) offshore and where water temperatures were 22 C or greater and surface salinities were 31‰ or greater. Minimum temperature at the onset of spawning was 18 C and minimum salinity was 26.6%. Our data show that bluefish spawning commences in June, peaks in July, and continues into August. Peak spawning activity occurred in early evening near sundown (1900-2100 hr). Eggs are thought to be transported south and offshore by prevailing surface currents. Larval bluefish inhabit surface waters and greatest numbers were found near the edge of the Continental Shelf. Juvenile bluefish move inshore during their first growing season. Despite intensive sampling, none were captured in offshore waters. We speculate that with growth young bluefish move to depths above the thermocline. We suspect that the most important single factor in determining the fate of every year class is the circulation of Continental Shelf waters.