Field Trips Are Not Just For Kids: RSMAS Students Participate in NMFS Mark-Recapture Study

Think back about what it felt like being a kid in elementary school and going on field trips. I remember how exciting it was getting ready for school that morning knowing that my whole day would be spent outside of the classroom, on an adventure. It didn’t really matter to me whether it was a trip to the science museum or to the theater, what mattered was getting the chance to experience the world first-hand. As we get older, field trips become few and far between. But this is not the case at RSMAS where students are offered many opportunities to apply their classroom knowledge in real-world settings.

I had the opportunity to work with the National Marine Fisheries Service on a mark-recapture study of bottlenose dolphins in Biscayne Bay. Although the name “mark-recapture” may suggest otherwise, this study did not actually involve the capture of any dolphins. Rather, it is a survey of dolphin populations using photos to identify and track specific individuals. All dolphins have a dorsal fin on their back, which can actually be used as a ‘fingerprint.’ Throughout its lifetime, a dolphin’s dorsal fin can receive many nicks and cuts resulting in a permanent and unique pattern that can be used in photo-identification studies to identify and catalogue individual dolphins. These catalogues are important in assessing the status and health of individual dolphins, as well as the population in general. And since dolphins are a sentinel species for the environment, their health is representative of the health of our ocean.

The Fisheries Service currently has a catalogue of the Biscayne Bay bottlenose dolphin population, complete with pictures of each dolphin’s dorsal fin. In an effort to update and maintain this catalogue, I was able to partake in one of their surveys to locate and photograph the dolphins. Photographing wild dolphins may seem pretty simple, but I actually found it to be quite challenging. Imagine standing on a boat, trying to maintain balance amidst the waves, while also trying to maintain the bulky camera straight and focused, and then timing the photo just right to capture a clear and centered photo of the dolphin’s dorsal fin. It was challenging but exciting at the same time, being out in the field, and collecting real data. In the end, it was a great experience in which I not only gained more knowledge about photo-identification studies but also a new respect for the skill. I look forward to the many more field trips that lie ahead.

This blog post is part of a series of stories written by RSMAS graduate students enrolled in the Spring 2012 Scientific Communications (RSM 545) course.

Melissa Lopes
MBF – MPS – Marine Mammal Science
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Webinar of the Week: Eutrophication and the Subsequent Waste-Water Management Scheme in Boston Harbor

In this week’s webinar, Rosenstiel School student Abbey Cherish Pennington talks waste-water management in the Boston Harbor during Dr. Neil Hammerschlag’s Marine Conservation class.

The Boston Harbor Project was one of the biggest wastewater management projects in the US, conducted from 1991 to 2000. The relocation of the sewerage outfall pipe from the mouth of Boston Harbor, to 15km offshore in Massachusetts Bay ended over a century of direct wastewater discharges into the harbor. The project led to a reduction in: total nitrogen, total phosphorus, total suspended solids and particulate organic matter by approximately 80-90%. Macroalgae, phytoplankton and submerged aquatic vegetation need a certain level of nitrogen and phosphorus, as they are essential elements for their growth.

This study provides an opportunity to examine ecosystem responses to major reductions in pollutant input, which could be used as an example for other waste-water management schemes, for example in Biscayne Bay, Florida.

-Andrew DeChellis
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Tiger shark vomits feathers, as well as new ecological information

One of the coolest aspects of doing research on the water is the “wild” aspect of it all—anything could happen on a given day, and there is always the potential for new discoveries. Sometimes discoveries are made after years of data analysis and attention to an issue, while other times nature hands it over to you in the heat of the moment….literally.

What would you do if a tiger shark vomited partially digested food on you?

Our research team was faced with this very question in November 2010 during a normal day of shark research in the Florida Keys. While taking measurements and blood samples on a sub-adult female tiger shark, I noticed a trickling of greenish, oily liquid coming from the mouth of the tiger shark. A few seconds later, a huge clump of feathers joined the river of bile and stomach acid. I sat there next to the shark, and couldn’t help but smile, knowing what this neat little observation meant.

These are the moments that we savor as scientists—the ones when nature decides to give you a little hint, a “tip” so to speak. We finished the work up of the animal, attached a satellite tag to her, and sent her on her way. Meanwhile, we bagged up the feathers and kept them on ice. And while tiger sharks are known to have a broad diet which indeed includes birds, we knew an identification of the specimen was needed before we could make any conclusions.

Partially digested remains of an American Coot, as vomited by a female tiger shark.

I spent the entire next morning calling bird experts at NOAA, Miami Museum of Science and the Florida Keys Bird Sanctuary. Upon making a few calls and emails, the story got juicier and juicier. I soon found out that there was a recent massive bird die-off, where hundreds of turkey vultures somehow ended up floating dead in Biscayne Bay and the middle Florida Keys—an area right in the “wheelhouse” of our tiger sharks. With the help of Tom Jackson at NOAA, we positively identified the specimen as an American Coot, a terrestrial bird species which is found in marshes throughout the middle of North America. It wasn’t a marine bird, and hardly a local species.

How did it end up in the tiger shark’s stomach?

The tiger shark’s menu is large and diverse. Photo by Austin Gallagher

We concluded that since there was a massive input of new potential prey items, the tiger sharks responded and took advantage. In fact, results from our satellite tagged individual showed that it spent a considerable time on the surface near Biscayne Bay after we released it, potentially continuing to feed on the floating mass of birds.

While tiger sharks are known to consume birds, such a scavenging event has rarely been described in the Atlantic, allowing us to publish a short note in the journal Florida Scientist. Since that day, we have seen tiger sharks puke up some other interesting food items. And while this was just one small observation, our finding is another piece of the puzzle to understanding these complex predators. Nature sometimes moves in mysterious way, and the infamous “Tiger Bird” episode proves just that.

If any other sharks want to puke on us, we are ready and willing.

-Austin Gallagher
PhD Student, Research Assistant
RJ Dunlap Marine Conservation Program
Abess Center for Ecosystem Science and Policy