Dolphins in Biscayne Bay at Miami: How Many, What Threatens Them and the Rules

Yes, Biscayne Bay holds a resident population of common bottlenose dolphins that NOAA Fisheries manages as its own stock, ranging from Haulover Inlet in the north to the Card Sound bridge in the south (NOAA stock assessment, July 2025).

That range follows the confirmed home ranges of dolphins tracked in a long-term photo-identification study, and NOAA treats it as the core range of the Biscayne Bay Stock (NOAA stock assessment). The study started with preliminary work in the central bay in 1990 and 1991, restarted in 1994, reached the northern bay and Card Sound Bridge in 1995, and pushed through Barnes Sound in 2008; as of 2021 the catalog held more than 400 marked individuals, many of them long-term residents (NOAA stock assessment).

The work is run from Miami. The NOAA Southeast Fisheries Science Center, at 75 Virginia Beach Drive, Miami, describes a long term photo-identification study of bottlenose dolphins inhabiting Biscayne Bay that has been ongoing since 1990, with the purpose of determining residency patterns and abundance (NOAA InPort record).

North of Haulover Inlet the picture blurs. Dolphins in the estuaries from Haulover north to Jupiter Inlet are not included in any NOAA stock report, because there is not enough data to say whether they belong to the Biscayne Bay Stock, to the Indian River Lagoon stock, or are passing coastal animals (NOAA stock assessment).

About 241 bottlenose dolphins live in Biscayne Bay, the best NOAA estimate from a fall 2019 boat survey of the bay off Miami, with a minimum population estimate of 233 (NOAA stock assessment).

The 241 figure comes from a capture and recapture photo-identification survey in October and November 2019 that split Biscayne Bay into northern and southern halves, with two research boats working at once when possible (NOAA stock assessment). NOAA has not analyzed a population trend for the stock (NOAA stock assessment).

This number is new. The previous edition of the Biscayne Bay stock report, dated May 2023, said no current information on abundance was available to calculate a minimum population estimate and that research to estimate abundance was under way (NOAA stock assessment, May 2023 edition); the July 2025 report now takes its 241 estimate from the 2019 survey published by Bowers and others in 2024 (NOAA stock assessment).

Yes, NOAA found significant genetic differences between Biscayne Bay dolphins and those in nearby Florida Bay, and together with strong site fidelity that makes the Miami bay residents a demographically independent population (NOAA stock assessment).

Inside Biscayne Bay there are two social groups. One is sighted mainly in the northern half of the bay and the other mainly in the southern half, and the two groups showed significant differences in contaminant loads (NOAA stock assessment). Their home ranges overlap and some interbreeding seems to continue, so NOAA has not split them into separate stocks (NOAA stock assessment).

The southern edge is still being studied. Biscayne Bay runs south through Card Sound and Barnes Sound and links by small inlets to Florida Bay, and early catalog comparisons show the two stocks overlapping near the boundary or in Barnes Sound, so the Card Sound limit may change (NOAA stock assessment).

The name may change too. Tamanend's bottlenose dolphin was described in 2022 as a smaller nearshore species, but those samples did not reach as far south as Biscayne Bay, so NOAA keeps the Miami animals listed as common bottlenose dolphins for now (NOAA stock assessment).

Fishing gear, a vessel strike and urban pollution are the pressures NOAA documents, and NOAA classes the Biscayne Bay Stock as strategic under the Marine Mammal Protection Act (NOAA stock assessment).

The stock is not listed under the Endangered Species Act, and the numbers explain the strategic label. NOAA sets the stock's potential biological removal at 1.7 animals a year, while documented human-caused deaths and serious injuries averaged 1.0 a year from 2018 to 2022; because stranding counts capture only a fraction of real deaths, NOAA says the true total for the Biscayne Bay stock is very likely greater than its PBR of 1.7 (NOAA stock assessment).

Crab traps are one named source. During 2018 to 2022 NOAA documented two entanglement serious injuries of dolphins in Biscayne Bay with trap and pot fisheries: in 2020 one animal was disentangled from commercial blue crab trap/pot gear and released alive, and a second was freed from unidentified trap gear the same year (NOAA stock assessment).

Water quality is the other pressure. NOAA says the northern bay, ringed by the cities of Miami and Miami Beach, is heavily influenced by industrial and municipal pollution and poorly flushed because of dredged islands, while the central and southern bay are better flushed and exchange water with the ocean through the Safety Valve (NOAA stock assessment). NOAA designated the Biscayne Bay Habitat Focus Area in 2015 with goals of better water quality, enough freshwater inflow and better habitat, and the focus area page describes a landscape-scale study of a major waterway discharging nutrients into the bay, while noting that specific NOAA funding for the focus area ended in 2020 (NOAA Habitat Focus Area).

On Biscayne Bay it is illegal to feed or harass wild dolphins, and NOAA encourages boaters, paddlers and anglers out of Miami to watch from at least 50 yards (150 feet) (NOAA Fisheries).

NOAA's viewing guidelines add three practical limits for a Biscayne Bay outing: limit overall viewing time to no more than 30 minutes, avoid circling or trapping dolphins between boats or between a boat and shore, and avoid separating mothers and calves (NOAA Fisheries). Feeding is banned because dolphins that learn to beg swim too close to boat propellers and get tangled in hooks and line (NOAA Fisheries).

Penalties for a Biscayne Bay violation are federal: if prosecuted under the Marine Mammal Protection Act, violators could face civil penalties up to $36,498, up to 1 year in prison plus fines, and forfeiture of the vessel involved (NOAA Fisheries).

For a land-based start, Biscayne National Park charges no entrance fee (Biscayne National Park fees); its Dante Fascell Visitor Center is open daily from 9 AM to 5 PM, and the canoe and kayak launch at Convoy Point is open 7 AM to 5:30 PM (Biscayne National Park hours).

A stranded, injured or dead dolphin in Miami-Dade waters is reported to the NOAA Fisheries Southeast Marine Mammal Stranding Hotline at (877) WHALE-HELP (877-942-5343) (NOAA Fisheries).

While waiting on a Miami shoreline, NOAA asks that people and pets stay back at least 50 yards (150 feet) from a stranded marine mammal, and reports can also be made through the Dolphin and Whale 911 app, available for Apple devices (NOAA Fisheries). The same NOAA page lists the FWC Wildlife Alert Hotline, (888) 404-FWCC (888-404-3922), as the Florida contact, and names the Marine Animal Rescue Society and the NOAA Southeast Fisheries Science Center Miami Laboratory, both in Miami, among Florida stranding network members (NOAA Fisheries).

Strandings matter for the Biscayne Bay count. NOAA builds its human-caused mortality figures for the stock from strandings, at-sea observations and fishermen's self reports, and says the number reported is a minimum because not every stranding or gear interaction is detected (NOAA stock assessment). During 2018 to 2022, nine common bottlenose dolphins were reported stranded within Biscayne Bay, five of them with evidence of human interaction from trap and pot gear, hook and line, gillnet gear and a vessel strike (NOAA stock assessment).