Fast Food and Fast Fish

Latest update August 26, 2019 Started on January 1, 2019

The Pacific Coast of Costa Rica is home to populations of some of the fastest fish including marlin, sailfish and tunas. We will explore the fish communities at "fast food" restaurants humans have installed to attract these fast fish.

January 1, 2019
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In The Field

Guest Posting: Verónica Valverde

Studying our oceans for better management is a big challenge that marine biologists, ecologists, researchers in general, and coastal communities are getting ready to tackle here in Costa Rica. I’m Verónica Valverde-Cantillo, from San José, Costa Rica. I got the chance to join the DynaMAR team on one of their billfish tagging trips. As a marine biologist who is fascinated in marine animal behavior and ecology, these projects never stop to motivate me. Getting to hear more about this project in specific and then getting to spend a few days with some members of the team was amazing. I got to experience my own country in a way I never had. Off the south Pacific coast is like a whole different place, and each step was enriching. These big animals, dorados, marlins and sailfish, that we rarely (if ever) get to see, came alive to my own eyes and it was amazing to see how these animals are handled so well in the tagging and measuring process. Lots of things to have in mind in the minutes of adrenaline you get when the fish is brought in close to the boat and the tags have to be deployed. Taking all the necessary data, having the equipment and tools ready, the person about to tag ready to go, making sure to hold her so she doesn’t fall over, making sure everyone’s handling the fish correctly, making sure to put the tag properly and the take the measurements…. Oh! And if you can take as many pictures as you can, that’ll be great! Keep in mind that it might be pouring down on you, and that everyone on board is also trying to watch and/or help. In the end, seeing the fish swim away is relieving. The team was great, the crew had two local men, which in the end are some of the most benefited people of these programs. This team really understands the importance of involving other people, like boat captains, crew and even tourists, in the investigation process, which, to me, is the best way to do science. The initiative of working directly with these teams, allows these projects to have a stronger impact, and involving them makes them feel a part of the effort to learn more and manage better the resources. The part of taking the ROV for a go was just as exciting. All sorts of different animals came up to see what it was up to and being able to use these tools as part of the research helps to get a better understanding of the targeted ecosystems. Like playing a videogame, the ROV is easy to use, and being able to see what is right around you, when you can’t see anything, adds more than a few levels to the excitement!

Spanish translation Estudiar nuestros océanos para darles un mejor manejo es un desafío muy grande para el que los biólogos marinos, ecologistas, investigadores y las comunidades costeras nos estamos preparando para enfrentar aquí en Costa Rica. Mi nombre es Verónica Valverde-Cantillo, soy de San José, Costa Rica. Tuve la oportunidad de unirme al equipo de DynaMAR en uno de sus viajes de marcaje de pez vela. Como bióloga marina fascinada por el comportamiento de animales marinos y la ecología, estos proyectos nunca dejan de motivarme. Tener la oportunidad de escuchar más de este proyecto en específico y poder pasar unos días con algunos de los miembros de este equipo fue increíble. Pude experimentar mi propio país de una forma completamente diferente. Alejándonos un poco de la costa Pacífica es como estar en un lugar completamente distinto, cada pasa fue enriquecedor. Estos grandes animales, dorados, marlines y peces vela, que con suerte vemos rara vez, tomaron vid frente a mis propios ojos y fue asombroso ver como eran manejados tan bien en el proceso de marcaje y medición. Hay muchas cosas que tener en mente en esos pocos minutos de adrenalina mientras cada pez es traído al lado del bote y se ponen las marcas. Tomar todos los datos necesarios, tener el equipo y las herramientas listas, el que va a poner el transmisor debe estar preparado, asegúrense de que no se caiga al agua mientras mara al pez, asegúrense también de que se está manejando al pez adecuadamente, y de poner el transmisor bien y tomar las medidas… ah! Y si puedes, toma tantas fotos como puedas! Esto puede ocurrir mientras hay una tormenta encima, además de que todos a bordo intentan ver y/o ayudar. Al final, ver como el pez se va nadando es un alivio. El equipo estuvo excelente, la tripulación estaba conformada, entre otros, por dos hombres locales, quienes al final son los más beneficiados por estos programas. El equipo realmente entiende la importancia de involucrar a otras personas, ya sean los capitanes de las embarcaciones, la tripulación y hasta los turistas, en el proceso de investigación, que a mi parecer es la mejor forma de hacer ciencia. La iniciativa de trabajar directamente con estos grupos permite que estos proyectos tengan un mayor impacto, y al involucrarlos les da una sensación de ser parte del esfuerzo por aprender y manejar mejor los recursos. La parte de darle una vuelta al ROV fue igual de emocionante. Todo tipo de animales distintos se acercaban a ver qué era y el poder usar estas herramientas como parte de la investigación ayuda a tener un mayor entendimiento de los ecosistemas deseados. Igual a jugar un videojuego, el ROV es fácil de usar, y el poder ver los que hay alrededor cuando normalmente no se ve nada le añade más niveles de emoción a toda la experiencia!

Photos: Top Left: Verónica, Danielle Haulsee, Hannah Blondin overlooking Golfito. Bottom Left: Pacific blue marlin Top Right: Verónica eagerly waiting for fish to take the bait despite the rainy weather. Bottom Right: Danielle Haulsee, Verónica and a mate use the Trident to explore the ocean at night.

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The team had a busy couple of months. We were down in Costa Rica for one week in June and one week in July. Due to issues with the motors on the Trident, we weren't able to run the ROV in July, but we did get some footage in June that we finally put together into a video to share with you guys.

Like we have touched on before, the goal of using the ROV is to try and survey the types and quantities of baitfish that are found on seamounts and FADs off the coast of Costa Rica. These schools of baitfish support many larger fish, like the blue marlin and sailfish our research focuses on, but also things like sharks, bigger tunas and dorado, marine mammals like dolphins and porpoises, etc. While we have not yet begun to quantify the amount of baitfish we have surveyed from the videos, we are able to see changes in diversity. Most of the schools of baitfish we have observed have consisted of three main species: yellowfin tuna and black skipjacks, and rainbow runners. On this dive, we observed a new species with the ROV, a few small Dorado (Mahi Mahi).

Check out the video, which also includes some night dive footage again, and let us know if you have any questions!

We recently worked with the SoFar Ocean team to help us recover a hidden video file on the Trident! This file was from one of our night dives. While we did add some of the highlights from the night dive, I thought I would add a more complete version here so you can see just how many little critters are attracted to the lights on the ROV. It is truly like flying through space sometimes. In addition, there are some more obvious things to see like the juvenile African pompano fish highlighted in our previous video, some flying fish and some larger squid. There are also several bright blue "specks" and bring red "specks" that we aren't quite sure what they are yet. It is really really interesting to see how the community of critters changes after the sun goes down. Most of the animals in this video spend daylight hours deep in the ocean, hiding from larger predators like fish and marine mammals (aka dolphins/whales) that use their eyes to find prey. By hiding in the dark, deep ocean, these small fish, squid and zooplankton decrease their chances of becoming someone's lunch. When the sun goes down, these twilight zone critters make the world's largest migration up to the surface waters, where they eat the phytoplankton (single celled ocean plants) that are found near the ocean's surface.

We hope you enjoy exploring what we can find in the deep blue sea at night, and as always, please feel free to leave any questions below. If we don't know the answer's ourselves, we are happy to reach out to our colleagues to find out!

In The Field

I’m on the deep end, watch as I dive in…to the open ocean! In addition to deploying six satellite tags on sailfish and blue marlin, the DynaMAR team launched the OpenROV Trident on its maiden voyage during the March 2019 trip! During this trip, we spent four days far from the shallows (125 miles offshore, to be exact) of Quepos, Costa Rica. Fishing effort was concentrated on a fish aggregating device, or FAD, which is anchored to an offshore seamount. The FAD (or fast food restaurant) aggregates baitfish which then attract blue marlin and sailfish. During our first ROV deployments, we were already able to take a look below the surface of the ocean to survey the composition and size of the baitfish aggregations found near the FAD.

From the underwater video, we were able to identify several species hanging out around the FAD including skipjack tuna, yellowfin tuna, and rainbow runners. The team also tested the ROV after dark and were able to see other critters that appear more often at night including squid, flying fish, and juvenile African pompano. We now have a better idea of which species of baitfish might be important for sustaining the billfish populations in this region.

The most challenging part so far is getting used to driving the Trident! Currents and open blue water make it difficult to keep the ROV on a steady path and figure out what direction you’re driving. The good news is that we’ve already improved! By the end of the trip, we got the trick of simultaneously turning and ascending/descending. The baitfish even started to get curious and would follow the ROV around as it moved about the FAD. We can’t wait to continue to learn about the species composition on the FAD and hope to catch a glimpse of a sailfish or blue marlin with our ROV on the next trip!

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The team has returned from Costa Rica. While we are unpacking and putting together our thoughts for a debrief, I thought I could first share some highlights from our ROV testing from this trip! We received the Trident the DAY BEFORE we left, so we were still trying to get a feel for it in the water this trip. Luckily, we were able to already start to answer some of our questions about what kinds of fish are attracted to the FADs! I put together a short video with some of my favorite clips and the species of fish we saw.

Please enjoy, and look for more updates from our last trip coming over the next few days.


The team has been gearing up for our next trip down to Costa Rica! We will be spending 5 days, 4 nights aboard a 42 ft. charter fishing boat, the Double Nickel ( We worked with this crew on our first trip down to Costa Rica, and they are not only great fisherman, they are also dedicated to the science and conservation of the marine ecosystem off of Costa Rica, so they are a true asset to our project.

Prepping for a trip to "the field" consists of planning travel logistics, getting paperwork in order, and making sure we have all of the gear and supplies we need prepped and packed.

This trip, we are hoping to put out a few more satellite tags on blue marlin, so a lot of our preparation deals with making sure our satellite tags are prepped and programed. Because our team spends a lot of their time working on computers, processing data and writing up research in papers and reports, it can be refreshing to have some hands on work to do prepping tags. To get the tags ready, we have to make leaders, the pieces of monofilament and shrink wrap tubing that connect the tag to the fish. We also have to check all of the tags to make sure they are working properly, and then connect them to a computer to program what kind of data they collect while on the fish, and how to know when to come off the fish.

We also have to make sure we have copies of all of our permits and licenses, data sheets printed out on waterproof paper, tools, a first aid kit, bug spray, and sunscreen, etc. This trip we will also have a satellite phone (there isn't cell service where we go offshore), a probe that can measure water temperature down to 300ft deep, and a standalone GPS unit. We also take a couple different cameras and GoPros so we can document the trip and share the things we see and do with the rest of our team and with our followers!

We are excited to announce that soon we will have a new tool to document our trip and to make observations of the fish communities we are studying in the field! We recently found out that we will be getting an OpenROV Trident through the S.E.E Initiative ( We are excited about this new partnership, and our expanded capabilities to observe and document how fish communities are structured at the FADs (the offshore fast food restaurants), and how the fast fish predators we are studying are interacting with each other at these hot spots.

Let us know if you have any questions about getting ready for field work in another country, or let us know what is essential in your field work kit!

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Some more thoughts and info about the project:

Along with studying the fish communities around the FADs (Fish Aggregating Devices, or here our fast-food restaurants), we will also be placing hi-tech tags on sailfish and blue marlin off Costa Rica to track where they go for months at a time. The goal of this, is to better understand how these fast fish move around depending on the environmental conditions (ocean temperature, ocean color, currents, bathymetry or depth, etc.).

These fish likely swim long distances along Central America, following ideal ocean conditions and food availability. Along the way, they are likely to encounter numerous fisheries. From recreational fisherman who release the fish alive after catching them, to long-line and purse seine fisherman who are likely targeting other species for food like tunas and Mahi Mahi (dorado), but who will sell the sailfish and marlin back at the dock if they are caught.

But what happens if a fast fish doesn't have to travel far for it's next meal? Are these fast-food restaurants changing the behavior of the fish, and potentially reducing their chances of getting caught in commercial food fisheries? Or are these fast predators susceptible to exploitation by commercial fisheries when they are concentrated in small areas like on the FADs?

We are hoping that using satellite tags, along with our surveys of fish communities and behavior at the fast-food restaurants, we will begin to be able to answer some of these questions.

Logistics update We are planning our next trip to Costa Rica for late March, early April. I've heard reports that the fish aren't around as much as in past years, which may be related to the moderate El Niño conditions we are experiencing in the Pacific Ocean this year. I'll save that discussion for another post. :)

Photo: Sailfish fin above the water while it is searching for prey fish to chase.

Good point! It’s an El Niño year... I wonder how that will affect the fish breeding in our project? Thanks for reminding me!
In The Field

In January, our team traveled to Costa Rica to begin our field work. Out on the water we got to see some of the amazing marine species that call these waters home. Here's some of the highlights. Hope you enjoy them as much as we do. We are looking forward to getting down there again soon to continue our research.

Expedition Background

The Pacific coast of Costa Rica is home to a diverse and valuable (ecologically and economically) array of oceanic predators including billfishes (sailfish, marlins, etc), tunas, sharks, and sea turtles. Sustaining commercial and recreational fisheries in this region is challenging because of limited data, the wide variety of competing interests, and perhaps an increasing influence from ocean climate variation. Marine animals live in a highly dynamic habitat, but humans have begun to interfere with these dynamics by installing Fish Aggregating Devices, or FADs, to attract these fast-moving pelagic predators to stationary locations. These underwater structures are attractive to smaller baitfish because they provide cover, and are attractive to predators because they become localized "hot-spots" of food. Think of these FADs like fast-food restaurants. This theoretically reduces the amount of searching a pelagic predator needs to do to find their next meal as they could hop from FAD to FAD (or fast-food joint to fast-food join if you will) to fill up. In addition, FADs are fascinating from an ecological perspective because they concentrate predator species (like marlin and sailfish) that would otherwise partition habitats and resources in order to avoid competing with each other. Our project hopes to better understand the basic predator-predator and predator-prey relationships around these fast-food hot-spots, in order to inform management decisions regarding how FADs affect commercial and recreational fisheries resources, as well as potentially protected species resources off of Costa Rica.

While we understand the general idea of these fast-food FADs, we still do not know much about the fish community that establishes at FADs. The underwater structure is usually anchored around 60ft (~20m) below the oceans surface, and out of view of humans. To understand the predator-predator and predator-prey relationships that form at these fast-food hot-spots, we need to start with some basic observations. We propose to use an underwater ROV to try and assess the fish communities around the FADs. An ROV has several benefits over human divers. These FADs are often located 12-15 hours run time from shore which is dangerously long time to get help in the case of a scuba diving emergency. In addition, the small size of the ROV and lack of bubbles will be less disruptive of the fish's natural behavior and allow for observations un-influenced by the presence of humans. Video observation is also is a non-lethal technique to survey the fish communities around the structures, as opposed to more traditional fish surveying techniques like net trawling, or hook and line fishing. Therefore, an ROV provides an opportunity to spy on rare behaviors and ask the question- "how does everyone behave in the fast-food restaurant when no one wants to wait in line for their food, and what's on the menu?"

We have recently just completed our first preliminary work in Costa Rica! Our team of researchers recently spent a little over a week in on the water in Costa Rica, working with private boat owners and charter boat captains to get on the ground (or on the water) experience fishing for marlin and sailfish, and deploying tags to track their movements. Most of the fishing was centered around these FADs, although what the fish community around the FADs looked like remained a mystery. We have many future trips planned and will hopefully be able to bring an ROV out with us to help answer some of these questions.

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Really interesting project! Thank you for sharing your work with us. I'd never thought of FADs as "fast food spots" and think it's a really useful metaphor!

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