End of Summer

Both the HMC and CSULB team have made it back to California safe and sound! Our time in Costa Rica formed lifelong friendships and memories we'll keep with us for years to come! We appreciate all of the support throughout the summer, and thank you for staying tuned in our many adventures!

Ray Tracking

All of the footage from the drone surveys performed over the past two weeks can now be analyzed back in the lab. One project the team is working on is tracking eagle rays as they move through the water. With this data, the team will be able to characterize the rays' behavior quantitatively. The images below show some preliminary results from this work.

An eagle ray in the water

The path of the eagle ray as it moves through the water

Drone surveys

Eagle rays and Pacific nurse sharks are two of the most commonly observed marine species in our drone surveys. Both of these species are considered threatened by the International Union for the Conservation of Nature (IUCN). The frequent sightings in Santa Elena Bay highlight the importance of our study site for the conservation of these species.  

Acoustic Receiver Retrieval

 Today, a portion of the Harvey Mudd Team assisted Mario Espinoza with the retrieval of acoustic receivers and the downloading of their information. Declan, Chris H, and Caitlyn were all able to do free dives (up to two meters!) to retrieve the devices, download the collected data, and then re-position the receivers on their underwater bases. Caitlyn was also able to do a six-meter dive for the retrieval of the fifth acoustic receiver in the set, with Mario free-diving alongside her. Pictured below are Declan and Chris H as they prep to retrieve one of the sensors.

Robot in the ocean

 We had to do several repairs of the AUV (Autonomous Underwater Vehicle) and managed a few tests (see image, but are now focusing on collecting acoustic tag data for state estimation. This data will support our efforts to develop new state estimators for tracking marine life.

Welcome Caitlyn!

HMC student Caitlyn Ossa (second from left, to the right of Felicity in image below) was finally able to join us on Sunday. She participated in shark tagging the very next day and can be seen wrangling a nurse shark in the first image. Dr. Espinoza can be seen managing the hook attached to this juvenile nurse shark.

A ray was also tagged this day!

 

Turtle Catch, Tag, Release

This past week we spent Friday morning attempting to catch turtles for tagging with an acoustic transmitter to enable motion tracking within the static receiver arrays installed in the two bays of interest. One green sea turtle, was caught, measured, tagged and released. HMC student Chris Herrera and Jaden Clark (left and right) are shown releasing the turtle in the affixed image.

Ray tagging

 It took us awhile, but we finally found a ray to tag in the mango groves.

Shark Tagging Episode 2

This week has been highly successful with respect to shark tagging. All students were able to aid in shark tagging that took place on two separate days of catching and tagging sharks. Image below shows HMC student Yoo-Jin Hwang measuring a recently caught nurse shark after she and team we able to position the shark in a state of "tonic immobility" (upside-down).

Two types of tags were embedded in the shark: 1) an acoustic transmitter tag that emits acoustic signals at pseudo-random intervals, and 2) PIT (passive integrated transponders) tags that can be used to identify the shark if re-caught later.

Costa Rica 2022: Field Day 4

After finally having reassembled the robot the previous day, today we aimed to run a mission and collect sidescan sonar data. We began by driving the boat around Matapalito bay to log GPS coordinates in order to plan the mission. I later plotted these coordinates on top of a map of the area:

Once we had a sense of the area we were working with, we created a mission for the robot that would drive it in zig zag pattern in order to completely cover a rectangle. However, as we got ready to deploy the robot, we realized that we weren't getting any GPS or sidescan sonar readings. Unfortunately, despite our efforts to debug the robot in the field, we were not able to resolve these issues. We decided it would be best to take apart the robot again once we got back to the lodge. Before we left, we drove the robot around in the water manually to make sure that it worked.

Once back at the lodge, we found some water damage to the GPS chip that will need to be replaced. Fortunately, it appears as though the sidescan sonar wasn't due solely to a wire that we forgot to connect.

About me: Chris Herrera

My name is Christopher Herrera, and I am a rising junior at Harvey Mudd College studying computer science and math. Starting in the summer of 2021, I worked with the SotoLab analyzing a large acoustic telemetry dataset of white shark trajectories along the beaches in Santa Barbara, CA. I transitioned to the LAIR lab in January 2022 and began working on various state estimation projects. These projects include a kalman filter to estimate the distance of an acoustic pinger tag from a hydrophone using time of flight and signal strength data, as well as a particle filter to combine measurements from two hydrophones to estimate the location of the tag. Eventually this work will allow us to track tagged animals with multiple underwater autonomous vehicles (AUVs).

Costa Rica 2022: Field Day 6

The Harvey Mudd, CSU Long Beach, and University of Costa Rica research team had the amazing opportunity today to help with Vanessa, who is a masters student at the University of Costa Rica. Her project, working under Professor Espinosa, requires tagging turtles in Playa Matapalito which is at the Northwest edge of Costa Rica.

Some of the beautiful scenery near Playa Matapalito and Santa Elena Bay

First, a line is set to capture sea turtles (and apparently some eagle rays as well!). Then as we waited, all of us hopped out the boat and snorkeled to see if we could find turtles and grab them by hand.  

A line was dropped and we started snorkeling right away

A little bit later,  a ray was caught (!) and we released it after a few pictures. After an hour or so, a bit distraught, we hopped onto the boat and started reeling the net in thinking we would have to move to another location to tag turtles. Then suddenly, as the net was being pulled in, a turtle was spotted! 

The turtle's head was wrapped in a wet cloth to keep the turtle calm

Chris helped out with measuring the turtle's width and length. We also measured the weight as well with a spring scale. I got the opportunity to hold the turtles flippers while we measuring and their flippers are much stronger than you would think! 

Chris is measuring the width of the turtle

Weighing the turtle with a spring scale

Turtles, as the one you see in these pictures, will have barnacles attached to them. Barnacles tend to adhere to the shells of the sea turtles due to their hard shell. 

Acoustic transmitter attached to the exterior, backside of the turtle

Then, the turtle was released! It was an exciting day of tagging turtles and the Harvey Mudd research team got to learn so much about turtles from the University of Costa Rica research team. Thanks for reading and that's all for Day 6! 

-Yoo-Jin

About Me: Felicity Eriksson

Hi! I'm Felicity Eriksson, and I'm a rising senior majoring in marine biology at California State University, Long Beach. I am part of Dr. Lowe's Shark Lab and have been helping with juvenile white shark research since Fall 2021. I am currently collecting and using drone footage to analyze movement data on the spotted eagle ray, Aetobatus laticeps.