Dolphins of Biscayne Bay — Miami, Florida

Biscayne Bay, the 35-mile-long lagoon that borders Miami to the east and separates the city from its barrier islands, is home to a federally recognized stock of common bottlenose dolphins (Tursiops truncatus truncatus). NOAA Fisheries designated Biscayne Bay a Habitat Focus Area in 2015, establishing it as a priority location for coordinated conservation work involving multiple federal, state, and academic partners. Within this framework, the bay's resident dolphin population occupies a defined stock range stretching from Haulover Inlet in the north to Card Sound Bridge in the south, according to the NOAA Fisheries 2022 Stock Assessment Report. The bay's seagrass beds, mangrove shorelines, and shallow-water habitats provide the foraging and social environment that supports this population's documented long-term residency. NOAA's Southeast Fisheries Science Center has monitored these dolphins continuously since 1990, making Biscayne Bay one of the longer-running estuarine dolphin study sites on the U.S. Atlantic and Gulf coast.

NOAA Fisheries formally recognizes the Biscayne Bay dolphins as a discrete management unit: the Biscayne Bay Stock of common bottlenose dolphins. The stock's geographic range, as defined in the 2022 Stock Assessment Report, runs from Haulover Inlet — approximately eight miles north of downtown Miami — south to Card Sound Bridge, which marks the boundary between Miami-Dade County and Monroe County at the northern edge of the Florida Keys.

The 2014 edition of the Stock Assessment Report documented that through 2007, photo-identification work had catalogued 229 unique individual dolphins in the bay. Approximately 80 percent of those catalogued animals were classified as long-term residents, indicating a stable core population rather than a transient aggregation. The 2014 report also identified at least two overlapping social groups within the stock, suggesting internal social structure within the bay's dolphin community. The species present is the coastal subspecies Tursiops truncatus truncatus, which is distinct from the offshore bottlenose dolphin populations found in deeper Atlantic waters east of the barrier islands.

NOAA's Southeast Fisheries Science Center operates the Biscayne Bay Florida Bottlenose Dolphin Studies program, a long-running scientific effort designed to characterize the residency patterns, population size, and social structure of the bay's dolphin stock. The primary methodology is photographic mark-recapture, in which researchers photograph the dorsal fins of individual dolphins and use naturally occurring nicks, notches, and scars to identify and re-identify the same animals across time and space. The NOAA SEFSC InPort dataset record describes the program's specific purpose as determining residency patterns and abundance within the Biscayne Bay Estuarine System.

A companion database, the Biscayne Bay Dolphin Photo ID System, maintains the cumulative catalog of identified individuals. According to NOAA SEFSC InPort records, this dataset was last updated in May 2025, confirming the program remains active. The photo-ID catalog serves as the primary data source informing NOAA's periodic stock assessment reports, which are produced under the Marine Mammal Protection Act and inform federal management decisions. NOAA's InPort record for the Photo ID System provides the methodological and population stock structure context underlying the assessments.

In 2015, NOAA designated Biscayne Bay as one of its national Habitat Focus Areas, a program that concentrates agency resources and interagency coordination on ecologically significant coastal and marine systems. According to NOAA Fisheries, the Biscayne Bay Habitat Focus Area encompasses the bay and its adjacent reef tract, the entirety of Biscayne National Park, the Florida Department of Environmental Protection Biscayne Bay Aquatic Preserves, and a northern extension of the Florida Keys National Marine Sanctuary.

The NOAA Habitat Blueprint identifies four implementation goals for the Biscayne Bay HFA: improving water quality, restoring freshwater inflow, protecting species habitat, and expanding public awareness. The freshwater inflow goal is linked to the Comprehensive Everglades Restoration Project, the large-scale federal-state effort to restore more natural hydrological patterns to South Florida, which historically fed freshwater into the bay through a network of drainage systems. Partner institutions named by NOAA in the Habitat Focus Area framework include Miami-Dade County, the Florida Department of Environmental Protection, Biscayne National Park, the University of Miami, and Florida International University, alongside multiple nongovernmental organizations. For the dolphin stock specifically, water quality and seagrass integrity within the bay are directly relevant, as seagrass beds support the fish prey base on which resident bottlenose dolphins depend.

The most recent federal stock assessment, the NOAA Fisheries Common Bottlenose Dolphin (Biscayne Bay Stock) 2022 Stock Assessment Report, released in August 2023, reported that no current abundance estimate was available for the stock. The report noted that residency patterns within the stock are not yet fully characterized and that the photographic mark-recapture methodology required to produce a statistically valid abundance estimate remains ongoing. Population trends and productivity rates for the Biscayne Bay Stock were also documented as insufficiently characterized at the time of the 2022 assessment.

The absence of a current abundance figure does not indicate a newly identified data gap; the 2014 Stock Assessment Report similarly flagged the need for additional mark-recapture surveys to produce a reliable population estimate. NOAA SEFSC InPort records accessed in May 2026 confirm that the Biscayne Bay Dolphin Photo ID System dataset was updated as recently as May 2025, indicating that field data collection continued through at least that date. The ongoing accumulation of photo-ID records is the mechanism by which NOAA anticipates eventually producing an updated abundance estimate for the stock.

The Biscayne Bay Stock sits within a broader South Florida marine ecosystem that includes Biscayne National Park, which the National Park Service administers across approximately 172,000 acres of bay waters, coral reefs, mangrove shoreline, and barrier islands south of the city. The park's southern boundary adjoins the northern Florida Keys, where a separate management zone — the Florida Keys National Marine Sanctuary — covers adjacent offshore reef habitat. The 2015 Habitat Focus Area designation explicitly incorporated the northern extension of that sanctuary into the Biscayne Bay framework, reflecting the ecological continuity between bay and reef environments.

Federal protection for the dolphin stock flows primarily from the Marine Mammal Protection Act, which prohibits harassment, hunting, capturing, or killing of marine mammals in U.S. waters and designates NOAA Fisheries as the lead agency for cetacean management. Stock assessment reports produced under the act, including the periodic Biscayne Bay assessments, inform federal decisions on whether a stock meets the act's definition of strategic — a designation that triggers additional management attention. The Biscayne Bay Stock's classification in successive assessments has been tied directly to the availability of reliable abundance data, which the ongoing SEFSC photo-ID program is designed to supply. Miami-Dade County, through its participation in the Habitat Focus Area partnership, represents the primary local governmental entity engaged with the broader conservation framework within which dolphin habitat protection is embedded.