Date of Award

8-1-2025

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Juliana M. Harding

Second Advisor

Robert Young

Third Advisor

Matthew Kimball

Abstract

Spot (Leiostomus xanthurus) are ecologically important and numerically abundant transient species that rely on temperate and subtropical estuaries for nursery habitat. Juvenile age and growth has been examined across their geographic range using length or sagittae at annual scales or for portions of a growth season. The overall research objective was to describe spot intra-annual age structure and growth rates based on arrival timing in a polyhaline intertidal Southeastern estuary. Juvenile spot were present in biweekly seine collections between February to November 2020 but absent in January and December. A 20-day lapillar correction factor was established to accurately age wild-caught spot and applied to 343 juveniles ranging from 67 to 212 dph. The last cohort to enter the estuary had the fastest growth rate (0.67 mm/d) at the warmest water temperatures. The fastest growth rates were observed after the seasonal thermal maxima in all three cohorts (n = 974 juveniles). The rate of biomass increase relative to length was significantly faster in the earlier cohorts than the last cohort. All cohorts transitioned from isometric to allometric growth between 56-62 mm standard length, ranging in biomass from 0.44 to 1.35 g. The timing of entrance into the estuary may determine cohort and year-class success as well as future spawning stock contributions. Incorporation of multiple sequential cohorts within a growth season into spot life history may maximize population ecological success at generational scales.

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