Hatch dates and habitat use of juvenile sheepshead Archosargus probatocephalus recruiting across a biogeographic divide in North Carolina.

Abstract

The goal of this study was to identify hatch dates of juvenile sheepshead (Archosargus probatocephalus) to confirm the spawning season for the species within North Carolina, and to identify potential spatial differences in early life history dynamics and habitat usage of juveniles. Spatial differences were compared across four locations to the North (Oregon Inlet) and South (Hatteras, Cedar Island, and Back Sound) of Cape Hatteras, a known biogeographical divide. Sheepshead are a coastal and estuarine species that are poorly understood in the region, especially concerning the juvenile stage. Sheepshead are managed by individual states and in North Carolina, a stock assessment is underway, and research on early life history dynamics was requested. The first objective of this study was to confirm the spawning season for sheepshead in North Carolina through a hatch date analysis. Transverse sections of sagittal otoliths were analyzed, and total age was used to identify hatch dates for juveniles in the four locations within North Carolina. The results determined that the general spawning season for sheepshead in North Carolina is April to May. Also, hatch dates varied spatially, especially between the Cape Hatteras breakpoint with fish from Oregon Inlet hatching later on average. The second objective was to determine fine-scale spatial differences in early life history dynamics across the Cape Hatteras breakpoint. Relationships between various important ages (total, pre-settlement, and post-settlement), timeframes (pelagic larval duration, juvenile stage), lengths (fork length and estimated size at settlement), and hatch dates were compared between locations. The results determined that early life history dynamics are variable across Cape Hatteras. Most notably, pelagic larval duration was longer for sheepshead collected north of Cape Hatteras. The final objective was to determine habitat utilization of juvenile sheepshead in Pamlico Sound. The utilization of various habitat types including seagrass beds, areas of oyster aquaculture, and unstructured sandy bottom habitats were compared. The results from this indicate that juvenile sheepshead have preferences for biogenic habitats, mainly areas of seagrass. The results from this study provide resource managers with more information on early life history dynamics of sheepshead in North Carolina. The confirmed spawning season can be further used as a baseline for additional research on reproductive biology of sheepshead. Additionally, this study provides methodology for any future research into a juvenile index of abundance, which can be used to create an index of annual recruitment. Finally, this study provides evidence of differences in early life history dynamics across Cape Hatteras and habitat preferences for the species.