June 20, 2024

Historical Seasonal Density and Distribution Patterns of Tursiops truncatus in Northeast Florida


Marthajane Caldwell


Abstract: The potential impact of scheduled channel changes in the St. Johns River, Florida, upon Tursiops truncatus communities within the area underscores the need for access to unpublished historic datasets. Thus, this article reports seasonal density and distribution patterns observed from December 1994 through December 1997 in the alongshore and estuarine waters of northeastern Florida. Frequency of social interactions and number of possible affiliates are influenced by abundance and distribution patterns of a species within a given area; thus, dolphin density as measured by both dolphins per km2 and dolphins per group was analyzed. Dolphin density was highly variable and significantly correlated with water temperature in the COAST region as well as the St. Johns River (SJR) study region and intracoastal waters south (ICS) of the SJR, but not in intracoastal waters north (ICN) of the SJR. Although sightings were randomly distributed with respect to water temperature in three regions, they were significantly clustered within the ICN. Neonate density (number per km2) in the ICS was over four times greater than in the exposed COAST region, more than five times greater than in the estuarine SJR region, and 17 times greater than in the ICN region. The number of neonates per group in the ICS was significantly higher than that in the exposed habitat of the COAST as well as in the estuarine SJR and ICN regions, which suggests that in 1994 through 1997, dolphins used the isolated, shallow, small inland Chicopit Bay of the ICS region as a nursery area. Since significant changes in the bathymetry and tidal flow patterns in these regions are scheduled, current dolphin density and distribution patterns are needed to determine if the seasonal density and distribution patterns identified in 1994 through 1997 are still relevant.

Key Words: seasonal density, distribution, bottlenose dolphin, Tursiops truncatus, northeastern Florida Document Type: Article
DOI: 10.1578/AM.42.1.2016.74
Page Numbers: 74-88

Info SKU: Vol__42__Iss__1__Caldwell Category: