Worries persist about health of blue crab stock
A new analysis of the Bay’s blue crab stock indicates that the species has been overfished for six of the past seven years—including 2004—despite efforts to reduce harvest pressure.
The analysis was presented in the annual blue crab advisory report of the Chesapeake Bay Stock Assessment Committee, which also shows that five years after the states agreed to act together to reduce harvest pressure on the Bay’s most valuable commercial species, the blue crab stock remains low and continues to run the risk of a collapse.
“Bay jurisdictions should, at a minimum, keep all current management measures in place,” said the committee, which is composed of scientists from universities, the National Oceanic and Atmospheric Administration’s Chesapeake Bay Office and the states of Maryland and Virginia.
The committee’s report serves as a prelude for what will likely be increased attention on blue crabs—and blue crab management—later this year.
The first completely new top-to-bottom review of the blue crab stock since 1997, using the latest research, is expected to be made final in late summer or early fall. Scientists familiar with that assessment say it will mostly reinforce the conclusions of the new advisory report.
Later this year, the Bay Program is scheduled to complete its first Baywide blue crab management plan since 1997. That “ecosystem based” report will discuss not only harvest management, but may also deal with habitat and predator-prey issues affecting crabs—some suspect, for instance, that the species is suffering from increased predation by striped bass and croaker.
Those reports, some suggest, could trigger the most serious discussions about blue crab management since 2000, when record low harvests forged the first Baywide agreement about blue crab management.
Working through a special Bi-State Blue Crab Advisory Committee, the fishery managers agreed to the first-ever fishing threshold for crabs, which was aimed at allowing 10 percent of the adult female crabs to survive and reproduce. The threshold was considered the maximum “safe” fishing level to prevent a stock collapse.
In addition to the threshold, the BBCAC had also set a lower fishing target, which was aimed at allowing the spawning stock to double.
To get to the target, fishery managers agreed to implement regulations that would reduce harvest pressure by 15 percent. Those actions were phased in through 2003.
Until this year, the annual blue crab advisory report had suggested that fishing pressure had dropped slightly below the threshold, but not yet reached the target. But scientists increasingly had questioned the technique used to measure fishing mortality, an estimate of the annual harvest rate of the adult population.
The new method shows that fishing-related mortality is not only exceeding the target, but has also been above the threshold every year since 1997 except for 2003. The report said the fishing mortality rate “increased substantially” last year from 2003. Despite the bad news, scientists say the new method of measuring fishing mortality, which has been under review for several years, is vastly improved.
“There is little doubt in my mind that is a pretty reliable estimate of what the fishing mortality rate has been,” said Tom Miller, a fisheries scientist with the University of Maryland Center for Environmental Science, and a member of the stock assessment committee.
Exceeding the threshold is a concern because it increases the risk of a stock collapse, particularly if the low population level was faced with adverse environmental conditions—such as an ill-timed storm during the spawning season—that could sharply reduce reproduction.
Still, the figures from the stock assessment show that fishing mortality the past three years was less than it was in 2000 and 2001, which suggests the regulations are having an effect.
“The fishing mortality rates have come down a great deal,” Miller said. “What we are trying to decide now is how much further they are going to come down—or is that the limit of what we are going to see?”
It’s possible, therefore, that managers may choose to maintain existing regulations to see if that trend continues.
“Even though we’ve been overfishing, the trend two out of the past three years was a decrease,” said Derek Orner, a fisheries biologist with NOAA’s Chesapeake Bay Office. But with fishing mortality remaining above the agreed upon threshold, he added, “you’d want to have some kind of discussion.”
Other measures of the stock health reported by the stock assessment committee were mixed:
- Recruitment, a measure of young crabs that survive to enter the population, slightly increased. Data from 2004 indicate above average average populations of juvenile blue crabs for the first time since 1999.
- The abundance of mature females, or spawning stock, remained below the long-term average, and data suggested a slight decrease in 2004 after small gains in the previous three years.
- The abundance of adult blue crabs larger than 5 inches remained below the long-term average for the eighth consecutive year.
Of particular concern to scientists is the lack of an increase in the spawning stock. The goal of the fishing restrictions was to initially protect at least 10 percent of the females until they spawned, and ultimately double the spawning stock by protecting 20 percent of mature females.
The stock assessment committee’s analysis is based on averaging the results of several surveys. But the survey of spawning females conducted by the Virginia Institute of Marine Science has shown a steady decline for several years. That is a concern because the VIMS survey is conducted in blue crab spawning grounds—female crabs in the other surveys may never make it to spawning areas.
“We don’t see a recovery of the spawning stock,” said Rom Lipcius, a VIMS researcher. “In fact, the spawning stock itself, in the spawning grounds, may be declining.”
Lipcius said it was time for managers to consider taking further steps to protect the crabs. “It’s possible that the regulations kept the fishery from collapsing, but it’s obvious that we have to do more,” he said.
When BBCAC established the threshold and targets, it called for jurisdictions to jointly evaluate progress and management actions in three years. That never happened. Instead, the committee was disbanded in 2003 after the Virginia and Maryland general assemblies failed to provide funding.
“To me, this year’s blue crab advisory report begs the question: Do the states need to come together again and consider additional management actions?” asked Ann Swanson, executive director of the Chesapeake Bay Commission, which operated BBCAC. “The Bi-State Blue Crab Advisory Committee appears to have helped reverse a decline, but the population has clearly stabilized at a much reduced level. We have not finished our work if our job is to double the spawning stock.”
Bill Goldsborough, senior scientist with the Chesapeake Bay Foundation, said future discussions should not be limited to regulations, but cover the whole range of recommendations from BBCAC. Efforts to control fishing pressure, he said, were “only the first step.”
Those additional recommendations were aimed at coordinating management, improving the health and value of the fishery, ensuring fairness among different groups and promoting ecosystem-based management. Most of those actions went unaddressed.
“I think we would be getting a lot more benefit out of the blue crab population,” Goldsborough said. “The Bi-State Blue Crab Committee was on a great track. It had vision.”
Part of the reason for the lack of follow-up was that after the painful and controversial process of cutting fishing pressure by 15 percent, the states agreed to give the regulations time to work before taking further actions.
Rob O’Reilly, a natural resource manager with the Virginia Marine Resources Commission, said that—at the very least— the time may have come for the states to evaluate each of the multitude of actions they have taken. “I think the time is here to look not only at what has happened to the stock, but perhaps what management action really has an impact, and what really doesn’t.”
Most don’t expect a major review to come until the new stock assessment is released in a few months, and perhaps not until after the new management plan is released late this year.
But as long as the population remains above the overfishing threshold, the stock will be at risk of collapse. “If we get poor environmental conditions, we could potentially collapse the population,” Lipcius said. “We need to get out of this danger zone so we are not taking a chance. We don’t have an insurance policy.”
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