Common bottlenose dolphin (Tursiops truncatus) abundance and distribution patterns in St Andrew Bay, Florida, USA

Abstract

1. Common bottlenose dolphins (Tursiops truncatus) are found in temperate and tropical waters of the world across a wide range of habitats. Along Florida's northwestern coast, this species resides in the bays, sounds, and estuaries (BSE) and coastal (CST) waters of the northern Gulf of Mexico. The National Marine Fisheries Service has identified one CST (Northern Coastal Stock) and seven adjacent BSE dolphin stocks, including the St Andrew Bay BSE Stock. 2. Baseline data are critical to assess the impacts of ongoing and future anthropogenic stressors on these stocks. Currently, there is no comprehensive abundance estimate for the St Andrew Bay BSE Stock, and there are limited data on distribution patterns and site fidelity for this stock. In addition, little is known about the Northern Coastal Stock hypothesized to range from the Big Bend of Florida to the Mississippi River Delta, inclusive of the CST waters adjacent to St Andrew Bay. 3. The goals of this study were to conduct photographic-identification surveys during 2015 and 2016 to determine abundance, distribution, and site fidelity of common bottlenose dolphins in the St Andrew Bay BSE Stock over four primary periods (199, 95% confidence interval [CI] 173-246), followed by July 2015 (249, 95% CI 199-338), and highest in October 2015 (299, 95% CI 259-361) and October 2016 (315, 95% CI 274-378). Few individuals were sighted in both BSE and CST waters (N = 25/ 353; 7%), and this fact, taken in tandem with limited connections between the BSE and CST environments, suggests that there may be minimal overlap between the St Andrew Bay BSE and Northern Coastal Stocks.

Capitoline Dolphins: Residency Patterns and Abundance Estimate of Tursiops truncatus at the Tiber River Estuary (Mediterranean Sea)

“…This study provides the first empirical estimates of abundance of bottlenose dolphins at the Tiber River estuary. The overall mark rate ( ) of this population is equal to 0.585, similar to those given by other studies [ 73 , 83 , 84 , 85 , 86 ], with peaks higher than 0.70, as in [ 87 , 88 ]. However, the annual mark rate decreases through the investigated years, with the lowest value in 2020 ( = 0.53).…”

Abundance and Occurrence of Common Bottlenose Dolphins (Tursiops truncatus) in Three Estuaries of the Northwestern Gulf of Mexico

“…We calculated a corrected estimate of abundance (N̂c) to account for both marked and unmarked individuals by dividing N̂ by the proportion of marked fins, also known as theta (θ). Since the proportion of distinctive fins can change between and within survey areas (Balmer et al 2019), seasonal θ values were calculated for each of the 3 survey areas. As with previous studies, θ was derived by calculating the proportion of distinctive fins (D1 + D2) out of all fins (D1+D2+D3+D4) that met photo quality criteria (i.e., PQ1 and PQ2) and were collected during on-effort group encounters (Read et al 2003) for each of the Bay and Selective datasets.…”

Seasonal population parameters reveal sex‐related dynamics of common bottlenose dolphins in open waters of the southwestern Gulf of Mexico

“…Recent CMR estimates of bottlenose dolphin abundance in coastal and/or inshore areas in the northern Gulf of Mexico include St. Joseph's Bay (Balmer et al, 2008), Sarasota Bay (Tyson & Wells, 2016; Wells & Scott, 1990), Barataria Bay (McDonald et al, 2017), Mississippi Sound (Mullin et al, 2017), St. Andrews Bay (Balmer et al, 2019), and Sabine Lake, West Bay, and Galveston Bay, Texas (Ronje et al, 2020). In the southern Gulf of Mexico, information is available only for Nautla (Morteo et al, 2019) and Tuxpan (Valdés Arellanes et al, 2011), off Veracruz State, near our study area.…”