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Finding Fins: Dolphin Field Research

Published August 29, 2014

By Kerry Diehl, Senior Marine Mammal Trainer

Last month, I had the opportunity to represent the National Aquarium on a field research project studying free-ranging dolphins in the Gulf of Mexico. The purpose of my visit was to learn about field research with dolphins and the current threats to marine mammals in coastal waterways.

An important question worthy of study is the extent that human activities impact resident dolphin populations. For the past ten years, Dr. Ann Weaver has been studying free-ranging bottlenose dolphins off the coast of St. Petersburg, Florida. Backed by a federal permit, which is required for field work with marine mammals, she works to identify and monitor a community of over 300 dolphins in and around John’s Pass, a shallow, canal-filled waterway connecting Boca Ciega Bay and the Gulf of Mexico.

Dolphin jumping

Boating along the same six mile stretch of intra-coastal waterway as her study area two times each week, Dr. Weaver is able to get a snapshot of its current population.

NOAA researchers

The Basics of Dolphin Field Research

As a research assistant, I had the opportunity to experience firsthand what’s involved in conducting field work with dolphins. This included skills such as observational tactics, photo ID documentation and analysis, behavioral data collection, population biology calculations and dolphin field veterinary data.

NOAA researchers

Dorsal Fin Identification

In order to monitor the population, it is essential to be able to tell the dolphins apart. This is done through dorsal fin identification. The dorsal fin of a dolphin is a unique reflection of the dolphin’s experiences. If the dorsal fin pattern is distinct, the dolphin can be identified and studied. Calves usually lack identifying marks.

Dolphin fins

Dr. Weaver’s work involves photographing the fins of each dolphin encountered in the survey site and comparing the images to her catalog of over 250 individual animals that she has identified over the course of her ten-year study.

John's Pass Dolphins photo-identification catalogue

I had the opportunity to try my hand at photographing the dolphins, and I can tell you it is not as easy as it may look!

Kerry Diehl


The biggest threats to dolphins living in John’s Pass are the increasing boat activity and decreasing water quality.

During my time there, I witnessed a fair amount of boat traffic within close range to the animals, including mothers with calves just a few weeks old! Boats, more specifically propellers, can be extremely dangerous to dolphins, even lethal. Most boaters in the John’s Pass study area seemed to be cautious when boating in the vicinity of dolphins, which for their safety is a must. One way people can take an active part in conservation is to be careful boat drivers.

Dolphin fin

It is actually illegal to get close to and interact with any marine mammal in United States waters without a federal permit. Dr. Weaver has a special government permit that allows her to approach the dolphins as closely as she does. The best thing you can do for marine mammals like dolphins and manatees is to keep your distance and appreciate them from afar.

The quality of the water that these dolphins live in is a concern as well. Run-off from surrounding roads, lawn fertilizers and other chemicals are all detrimental to water quality and to the animals that call the seas home.

Dolphins are extremely curious animals and will interact with objects that they find in their environment. Unfortunately, this can include trash and debris. Dr. Weaver keeps a net handy at all times, scooping up any trash she encounters. You can help keep the oceans safe for dolphins by making sure your trash gets disposed of properly and by recycling whatever you can.

Cleaning debris from the water

Dr. Weaver cares deeply about these dolphins, and after assisting her in Florida and working daily with our dolphins here at the National Aquarium, it is hard not to do the same.

"If we love it, we will save it.”
– Dr. Ann Weaver

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