Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Herbert M. Austin
The spot (Leiostomus xanthurus) is an important commercial and recreational species in Virginia. Recruitment of juveniles to the Bay is characterized by large interannual fluctuations, that can be explained by the sequence and direction of wind during various phases of the early life history. An environmentally-modified Ricker stock-recruitment curve was developed incorporating the southeasterly winds in November-December, the southerly winds in January-March, and the westerly winds in April-May. This model explained 81% of the variation and closely paralleled the VIMS Juvenile Spot Index. Spot from the Chesapeake Bay migrate south in fall to spawn near or south of Cape Hatteras. Larvae were distributed over the shelf south of Oregon Inlet in February and early March, with the youngest larvae found over the outer shelf off Cape Hatteras. By late March, spot were distributed over the inner shelf north of Oregon Inlet to the mouth of the Chesapeake Bay. Age and size of larvae increased in a northward and shoreward direction. The persistence of larvae over the inner shelf north of Oregon Inlet suggests that a mechanism for northward transport occurs in this area. Northward transport over the inner shelf in the southern MAB is possible with multiple southerly wind events. Spot larvae would not have to be transported the entire distance to the Chesapeake Bay entrance, but only to where the bottom layers of the water column are moving toward the Bay. Recruitment to the Chesapeake Bay began in February or March of 1990 and in April of 1989 and lasted for two months. Spot entering the Bay were approximately 84 days old and 14.0 mm SL. The birthdates of spot collected offshore in the southern MAB and those at the Bay mouth were very similar, suggesting that recruits to the Bay were from the same pool of larvae collected earlier in the season and providing further support for a spawning location south of Cape Hatteras and not off the Chesapeake Bay as previously reported.
© The Author
Bodolus, Deborah A., "Mechanisms of larval spot transport and recruitment to the Chesapeake Bay" (1994). Dissertations, Theses, and Masters Projects. Paper 1539616574.