Follow the secret life of the lobster

To the average consumer, a lobster is just a meal sitting on a plate, waiting to be eaten.

Most have no idea that this meal has traveled hundreds of miles on the ocean floor before ending up on the menu.

But researchers who tagged the crustaceans know that the average Bay of Fundy lobster can criss-cross that bay several times over the course of a year.

A lobster caught on Grand Manan can easily make it to Nova Scotia in a month or two. Many go hundreds of miles further.

Heather Koopman examines where lobsters go and what they do 600 feet below the ocean’s surface. (Shane Fowler/CBC News)

“Some of them are going south to George’s Bank, some are going south to Maine, and some of them are going up the bay,” said Heather Koopman, senior scientist at the Grand Manan Whale and Seabird Research Station. “Last week I had a return from almost at Chignecto Bay.”

Koopman has been studying marine species from the research station for 32 years. Originally from Ontario, she is Professor of Biology in Marine Biology at the University of North Carolina Wilmington, where she teaches. But during lobster season, she’s more likely to head out to the open seas with lobster boat crews.

While the fishermen bring the lobster on board, she marks the females to be released back into the sea.

Some get a simple yellow zip tie that goes loosely around the Hummer’s wrist. This plastic tag has an ID number and Koopman’s phone number.

Koopman records the lobster’s size and location before releasing the tagged lobster back into the Bay of Fundy. (Shane Fowler/CBC News)

“We just ask the fishermen if they catch one of these to text my phone and the easiest way to do that is for them to take a picture because I want to know where they caught them, they take a picture of their plotter that has it [longitude and latitudes] thereon.”

This gives researchers like Koopman a very rough idea of ​​where females migrate to over the course of a year. Depending on the number of times a single lobster is caught and released, it can create a fairly accurate map of where it’s been over the years.

And they don’t move in a pack.

“Individual lobsters seem to make individual decisions,” Koopman said. “I can tag two lobsters in the same place on the same day, and they’ll be re-caught at different times in completely different places. So they seem to have their own ideas about what they’re going to do and where they’re going.”

CLOCK | Egg-bearing lobsters are tagged for science:

Bay of Fundy lobsters are helping researchers gather important data about their species

Scientists hope to learn more about lobster migration, the preferred climate when it comes to hatching and laying eggs.

According to Koopman, tagging lobsters gives researchers an idea of ​​where egg-producing females migrate, which could affect how lobster quotas and catch zone boundaries are set by the Department of Fisheries and Oceans.

But why do lobsters travel so far? This question can simply boil down to temperature.

measure temperature

Some lucky lobsters get an entirely different label. Hobo treats are thermal loggers that look like large yellow lobster wrist watches. Once activated, the gauges will record the water temperature every 15 minutes.

When that lobster is caught again and the logger is returned to Koopman, it connects via Bluetooth to an app on her phone and gives her the exact temperatures the lobster has been exposed to since it was last recorded.

A clutch of lobster eggs sticks to the underside of their mother’s tail after laying. (Shane Fowler/CBC News)

“Lobster reproduction is very temperature sensitive, and lobsters themselves are very temperature sensitive,” Koopman said

“There have been some lab studies that have shown that they can tell the difference or have a sensitivity down to 0.1 degrees Celsius. So temperature makes a difference for lobsters.”

According to Koopman, evidence suggests lobster eggs require cooler temperatures as they develop. But once those eggs are laid and stored under the female’s tail, they’ll likely need warmer temperatures to hatch at the right time.

“The water temperature accelerates the metabolism. So when it gets warmer, everything goes faster. They deplete their yolk resources faster, they grow faster,” Koopman said.

A Hobo Tidbit Thermal Logger is attached to a couple of lobsters before they are released. The logger measures the temperature of the water every 15 minutes. (Shane Fowler/CBC News)

She says there is also evidence that newly hatched lobsters may feed on zooplankton, tiny aquatic organisms that are affected by temperature changes. So if the temperature isn’t ideal when the eggs hatch, there may be no food for them.

Koopman said the data collected on these thermal loggers will go a long way in providing insight into the lobster’s life cycle in the wild, something they say scientists know very little about. So far, there isn’t even a way to accurately estimate how old a lobster might be.

But another lobster tagger up in the Bay of Fundy is working on it.

Various tags

Koopman only gets back about every fourth thermologger and only 30 percent of the yellow cable ties. That’s because lobsters shed their entire exoskeleton when they moult, leaving those marks still attached to empty shells on the ocean floor.

So how do you tag a creature that’s constantly shedding, so to speak?

Rémy Rochette has spent the last 12 years researching lobsters in his laboratory at the University of New Brunswick in Saint John. Last spring, he and his team tagged thousands of lobsters in the Bay of Fundy with T-bar tags.

Rémy Rochette has been researching lobsters at the University of New Brunswick in Saint John for 12 years. (Submitted by Remy Rochette)

Rochette likens these tags to the tiny plastic tags attached to new clothing.

These pierce the lobster shell.

“Basically, they anchor themselves in muscle tissue and when the lobster molts, it stays there,” Rochette said. “So we can actually track lobsters over longer periods of time.”

Rochette is testing a technique that uses structural changes in DNA molecules to estimate age. He says a similar study was done in Europe on a different species, so his lab is testing whether it will work on Homarus americanus — the American lobster found here on the Atlantic coast.

“If we [tagged] we also took a small biopsy from them and will be using this small biopsy to examine … structural aspects of their DNA.” Rochette hoping to recapture the same lobsters, or at least some of them, at different times.”

T-bar tags allow researchers to tag lobsters longer because they don’t detach during moulting. (Submitted by Remy Rochette)

Of the approximately 2,000 lobsters that Rochette and his team tagged this spring, 45 have been recaptured.

There is a more complex way of tagging that doesn’t require re-entry.

These pendants attach to larger lobster shells with specially made straps. The electronics in a tube detects the depth using pressure sensors and the temperature. When it’s time to collect the data, the label is ejected from the tube and the lobster.

Lobsters equipped with custom satellite tags do not need to be recaptured to retrieve the collected data. The tags are ejected from the dishes, float to the surface and transmit their data. (Submitted by Remy Rochette)

“This has a small electronic mechanism that, at a programmed set time, sets off an explosion that causes the label to detach,” Rochette said. “If all goes well, after the release they will come to the surface and transmit the data back to us via satellite.”

right

Despite all the technology and research involved in recording lobster movement and the temperatures they prefer, Koopman says lobster fishermen already know much of what she’s learning.

A lobster fitted with a customized harness and satellite tag as part of Rémy Rochette’s research. (Submitted by Remy Rochette)

“The people who are on the water every day know more about all of this than any of us,” she said.

“They’ve been watching these things for years, decades in some cases. Many of them have been fishing long enough to see large decadal fluctuations.”

Data collected from tagged lobsters gives an idea of ​​where they go after they are released. (Submitted by Remy Rochette)

According to Koopman, it is important to back up fishermen’s knowledge with data, which in turn can lead to better fishing regulations to make them more sustainable in the years to come. But she says it’s always humbling to work alongside those who’ve been lobstering for a living all their lives.

“What we’re doing as scientists is sort of confirming what they’ve already assumed,” Koopman said.

READ :  Who Knows Best? The urge to replace the parents

Leave a Reply

Your email address will not be published. Required fields are marked *