After a week of checking our field site, our first batch of lobsters is no where to be found! Although none of our experimental lobsters were located, we did have three resident lobsters stay on the site for the entire week. We tracked each resident lobster by a unique color combination of antennae tags. We also determined the sex and carapace length of each resident lobster.


Today we released our second batch of lobsters at a new site. Our second site contains no artificial shelters unlike our first site (which contained artificial shelters). We will continue to monitor our first site along with our second site. It is important to continue checking our first site in case our experimental lobsters return. This will help us determine whether we should check sites for more than one week after an experimental release.

As promised here are some pictures of our first site release. The first step was to catch all the lobsters out of our mesocosm using hand nets and tickle sticks. The tickle sticks are a great tool that we use to help walk our lobsters into our nets.













Then, the lobsters were loaded into a cooler and placed on the Parker. We drove out to our first experimental site, which was where we set up our transect the previous day. Each lobster was removed from the boat and gently placed into or near a shelter. Both artificial and natural shelters were used. To observe the denning behavior and dispersal of resident lobsters, we also tagged lobsters that were already on the site. These were lobsters that were not used previously in our experiment, but happened to be utilizing shelters within our site. During the next week, we will be checking the site daily to see where our lobsters are!

Field Release Tomorrow!

For the past week, we have been examining the denning behavior of 20 spiny lobsters in an enclosed area (mesocosm) that contains ten artificial shelters. Each morning, we snorkeled the mesocosm and recorded where the animals are. We can tell each animal apart because they have a unique combination of colored antennae tags. After four days, we reduced the number of artificial shelters in the mesocosm to five to examine whether habitat loss will result in a change in denning behavior.

Now that we know the dominance status of each individual and have examined their denning behavior in an enclosed area, we are ready for the final stage of our experiment. Tomorrow we will be releasing our first set of 20 spiny lobsters onto a field site to examine their denning behavior and dispersal in the natural environment. To prepare for our first release, we placed weighted transect lines along our sites. Using transect lines allows us to locate specific structures and to easily navigate our sites. Some great pictures of this process will be posted soon!

The many sizes and shapes of lobsters

Spiny lobsters have a complex life cycle. It begins when females travel to deeper, colder waters to release their young. The females fan their telson (or tail), and the larvae drift off into ocean currents without any parental care! At this stage, the transparent lobsters are referred to as phyllosome larvae.


As they complete all eleven stages of their development, spiny lobsters begin to look more like adult lobsters and are called puerulus larvae. It is a long journey (6-12 months), and as the surviving larvae grow, they begin to settle on hard bottom habitats. At this stage, spiny lobsters are solitary and have banded legs which aid in camouflage (see picture above). Spiny lobsters become social when they grow larger and migrate out of algal habitats.

Tracking juvenile lobsters using acoustic tags

Have you ever wondered where lobsters go when they leave their homes? Lobsters like all animals have to go find food, avoid scary predators, and make it home safely each day. What makes this particularly difficult to study is the fact that lobsters are nocturnal (active at night). That means while we're asleep in our beds, these lobsters are just waking up to go exploring. So how do marine biologists study the behavior of lobsters at night?

One way is to use acoustic tags. The small transmitter attached to the back of the lobster above sends out a signal a regular intervals (every 90 seconds). With the proper receivers set in the water, it is possible to track the movements of a tagged lobster without even being there. Here's how it works...


First, you need a set of acoustic tag receivers. Think of these as small radio receivers that operate on batteries and are water-tight. Here we have 10 radio receivers mounted in stands and ready to be placed underwater. Once in the water the receivers can keep track of many different lobsters at the same time.


Our experiment relies on the expertise of our friend and senior research biologist Dr. Rodney Bertelsen of the Florida Fish and Wildlife Research Institute. Dr. Rod is an expert at tracking marine animals using acoustic tags. He usually tracks the big adult lobsters out along the coral reef, but for this experiment, he is helping us to track our juvenile lobsters in Florida Bay.


The first step is careful placement of the receivers in a pattern on the ocean floor. On our study site this is shallow water, only about 2 meters deep and the receivers are placed about 20 meters apart. Dr. Mike drives the boat very carefully checking his GPS to find the exact spot for Dr. Rod to release the receiver.


Next, it is time to catch some juvenile lobsters to participate in our experiment. Here Dr. Mike dives down with a hand net to collect a juvenile lobster. The water is a little murky today because the wind has mixed up the sediment making it hard to see very far. A total of three lobsters are collected and returned to the boat.


Dr. Rod carefully attaches the acoustic tag to the shell of the lobster using Super Glue. This sounds painful (and should not be tried at home) but it is harmless to the lobster because their shell is hard. The glue will keep the tag attached for a week or two until the lobster has its next molt. Then as the lobster crawls out of its old skin it will leave the tag behind. Dr. Rod also places a bright yellow tag on the base of the antennae. Can you see the yellow tag in the picture? This helps the divers to recognize a tagged lobster once released.


Now the time has come to release the tagged lobster. Dr. Mike carefully swims the animal back to the same shelter where it was collected. It is not known if lobsters keep the same shelter night after night, but we hope to find out from this experiment. By the end of the day we release three tagged lobsters known by their tag colors as RY, LY, and YY.


Here is lobster RY in his home shelter, an concrete block. This is where he was released on Day 0. We note this on a map printed on waterproof paper. We carry this map on a clipboard underwater each day when we search for our tagged lobsters.


Meanwhile, our acoustic receivers are listening for the 'ping' of each acoustic tag. When a 'ping' is heard it is recorded along with the time of day. Later when we recover the receivers and download the data to a computer, we will know which receivers heard from each lobster. As the lobsters move around, they will only be received by the closest receivers. That way we can estimate their location at all hours of the day and night.


Today is Day 5 and we checked on the location of the lobsters on Days 2 and 4. Lobster RY was found in a hole about 2 meters from it's original release point on both Days 2 & 4. Lobster YY was found 1 meter from it's release point on Day 2 and then 8 meters away on Day 4. Lobster LY was not found on either Day 2 or Day 4, but that doesn't mean its left the site. We'll have to wait until we check the data from the receivers to know if and when it left the area. Check back soon to see what happened to our tagged lobsters.

Time for some snorkeling!

For the past week, we have been completing behavioral observations to determine the dominance status of each lobster. By knowing the dominance status of each lobster, we will be able to determine if dominance influences den sharing behavior in our mesocosm study.

Since we worked hard all week to prepare the mesocosm, we decided to take the afternoon off and snorkel Coral Gardens - a coral reef near Long Key. Enjoy the pictures (Left: sea turtle; Middle: cow fish; Right: brain coral)!

Learning New Techniques

As a researcher, it is important to learn new techniques that my be useful for future experiments. We started off the morning by learning how to pull larval collectors. Specifically, these collectors monitor the abundance of spiny lobster pueruli (or late-stage larval lobsters) near Long Key. The pueruli can be extremely small, and as we found out, it is often hard to pick them out of the collectors. In the afternoon, we began a trial run of our acoustic tagging project. We activated all of the receivers (the objects that receive a 'ping' or signal from the acoustic tag) and headed out into the field to set up the array and tag juvenile lobsters. After the receivers and tagged lobsters were in the water, the 'pings' began to be recorded by the receivers. This data will be later uploaded into a computer, and the position of each tagged lobster will be calculated. By completing this trial run, we will have a better understanding of the steps needed to set up an array of receivers and the dispersal distance of juveniles.

First Day in the Field

After learning how to complete an underwater transect, we headed out on the Parker (the Keys Marine Lab boat). Each field station contains two experimental sites (one with artificial shelters and one without artificial shelters), and the artificial shelters must be removed from one these sites. Our first task was to shoo out all the inhabitants with a tickle stick (which is commonly used for lobstering in the Keys). Then, we tied a rope to the blocks, swam the heavy blocks to the boat, and lifted them onto the boat. Since the artificial shelters have been underwater for many years, they were fouled with many neat organisms. While we were snorkeling around, we took some pictures of lobsters in their dens. Lobsters often use the artificial shelters, crevice holes, and sponges/corals as homes during the day. Part of this experiment will examine the influence of artificial shelters on denning behavior and dispersal of juvenile lobsters.

Which Lobsters Share Shelters?

Spiny lobsters are known to be social animals that often share crevice shelters. However, den sharing is far from obligatory. On average only one-half of all juvenile lobsters in Florida Bay are sharing shelters at any time. What are the factors that determine who will and will not share shelters with one another? This is the question we are studying for our current research project in the Florida Keys.


We are staying at the Keys Marine Laboratory in Long Key, FL for the next month and will we post updates as we can during our time out of the water.