Over the summer, crabbers in Chesapeake Bay pulled up four funny looking creatures. They were not the bay’s normal, skinny blue crabs, but instead, chunky stone crabs, the delectable crustaceans whose claws sell for between $40 and $70 — or more — per pound.
“This is the first documented instance of stone crabs now being able to live inside of Chesapeake Bay,” said marine biologist Romuald Lipcius, of the Virginia Institute of Marine Science, William & Mary, who is researching the finding.
The stone crab range expansion may eventually bode well for Chesapeake crabbers, but the warm waters that made it possible are not necessarily a good sign for the crabs in Florida.
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The stone crabs discovered in the Chesapeake were large enough to be about four or five years old, meaning they may have survived several winters in the area. In fact, crabbers have since pulled up more, and their arrival may signal a new commercial species in the region. Lipcius suspects the newcomers will make themselves right at home.
“I believe, because of warming waters, that now, all of a sudden, stone crabs were able to survive, grow, and live for a long time inside of Chesapeake Bay,” he said.
Their survival is not just about warming waters, though. The Chesapeake Bay’s successful oyster restoration efforts provide ample food for several crab species. “Juvenile stone crabs are abundant in oyster reefs — it’s a sort of a prime nursery habitat. … Stone crabs are going to be able to survive, and they’re going to have plenty of food to eat in those oyster reefs and surrounding areas,” said Lipcius.
Stone crabs have a leg (or 10) up.
“They’re like little tanks,” said Ryan Gandy, a crustacean expert and science and restoration manager for the Sarasota Bay Estuary Program. “They can take a lot of stress, from low oxygen stress all the way to high red tide (toxicity). … I think they stand a really good chance of being able to get a foothold somewhere and maintain that just because they’re such a hardy species.”
Their strength also allows them to prey upon many types of shellfish. “They can generate 10,000 pounds per square inch of pressure (with their claws),” said Gandy. “The strength of those claws is really for breaking into shells.”
As for how they found their way north to the Chesapeake, Gandy and Lipcius said when they spawn, their larva drifts on currents which spread them into new territories. There have long been stone crab harvests in North Carolina, now they’re just expanding their range as the climate allows.
What do warming seas mean for stone crabs in Florida?
Though stone crabs are extremely hardy, they do have temperature limits. If water gets below 41 degrees F for a prolonged period, they die.
“That’s the way it used to be here in the Chesapeake,” Lipcius said. “But with the warming waters — we’ve been warming at the rate of about a half degrees centigrade per decade, so it’s a good bit warmer over the last 40 years.”
Florida, too, has seen warmer water temperatures. “We have lost about a month and a half of those lower temperatures, below about 68 degrees on average,” said Gandy, “and we’ve gained more temperatures above 68 degrees. So your water holds a lot more heat, and it stays warmer longer.”
Gandy said water temperature triggers stone crab spawning. “As you get earlier and earlier warming up of the water, they’re spawning a lot sooner, it may come down to a time, you know, maybe in another decade or two, when you have a very short window of spawning instead of having, you know, four to six months.”
Crab larvae are affected by water temperature as well.
“We need to think more about the larvae than the adult crabs,” said Heather Bracken-Grissom, marine biologist at Florida International University.
Warmer water temperatures can decrease the time stone crab babies spend in the larval stage, drifting on currents. Currently, they live in the larval phase for up to a month.
“If that shortens, then they can’t disperse as far. … In healthy populations, you want wide distributional ranges,” she said. In other words, as water temperatures rise, stone crabs end up with a narrower geographic distribution, making populations more precarious, and vulnerable to local environmental stress.
Warm water also causes larvae to move into deeper water, which could move them out of zones that are valuable for commercial fishing — shallow water where it’s easier to fish.
Bracken-Grissom said she thinks there is a risk to losing stone crab range because of high water temperatures in Florida.
“Every animal has a minimum and maximum temperature range that they can tolerate, so there’s a tipping point for every species. We just need to pay attention to it, especially what larvae can tolerate.”
Warm water may push adult crabs deeper as well.
“We’ve heard of commercial fishermen trying and catching some crabs at 80 feet deep, but it’s a lot of work to maintain traps out that far,” he said. Traps at that depth would be 10 to 20 miles offshore on the Gulf coast.
As of today, the Florida Keys and west coast is still the perfect habitat for stone crabs. They like the broad gradual slope of the Gulf, which gives them plenty of bottom of relatively shallow depth — less than 80 feet or so — to forage. The coast off of Virginia and Maryland is similar.
Other species moving north
Stone crabs aren’t the only Florida-centric species making a move north as climate change opens up new waters.
“Snook, if you get a freeze, you’ll knock the population back. But we haven’t had a hard freeze that has knocked them back in over a decade, so you’re seeing them all the way up in the Panhandle,” Grandy said. “And mangroves are showing up all over the place — South Carolina, Georgia. They’re pushing their northern limits because the winter temperatures are just not getting cold enough to knock them back.”
Similarly, Maine lobsters are making a shift north into Canadian water, said Gandy, and the southern end of the range is retracting.
“The American lobster fishery has been having some hard times, just because the population is moving outside of where they fish. They’ve been looking at other crab species to fish, some of them you might see in the store called a Jonah crab. Fishermen, who are pretty much stuck in place for the regions they fish, are having to figure out how to fish different species because of these changes.”
As for the health of the Florida fishery, the core of the crab’s range, harvests peaked in the 1990s, said Grandy. “Harvests have been fairly stable for seven or eight years now,” he said. “But they’re fishing harder to get the same amount of pounds of stone crabs out every year.”
As for a new crab in the Chesapeake, Lipcius is more upbeat. “I really don’t think it’s going to be a bad thing over the long term,” he said. “To me, this is a feel-good story.”
Who knows, if Chesapeake stone crabs flood the market someday, maybe that will bring prices down.
Bill Kearney covers the environment, the outdoors and tropical weather. He can be reached at bkearney@sunsentinel.com. Follow him on Instagram @billkearney or on X @billkearney6.
This story was originally published by the South Florida Sun-Sentinel and shared in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the Sun-Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.
