Return of the Female Crabs
We’ve heard great news about blue crabs. The total population has risen this past year to almost 600 million, according to the 2019 Winter Dredge Survey.
Best of all, the sooks, our female spawning-age crabs, have reached a population of 190 million, only 35 million under the target level for healthy reproduction success that we should be striving to maintain all along. The spawning-size female population is the major factor in maintaining a healthy blue crab population.
This is cause for celebration, not news to take for granted. Just last year, the female population dropped by more than 35 percent after particularly frigid wintertime temperatures. Yet Department of Natural Resources allowed regular commercial female harvest limits in 2018.
As we were not in actual crisis, merely headed that way, DNR gambled on the fecundity of the blue crab to gradually restore the female stocks. Another deadly winter was discounted.
Luckily, this time the wager was right. Thanks to mild temperatures and an unusually generous Mother Nature, the female population bounced back this spring with unexpectedly significant gains. We are once again, and almost miraculously, approaching the female population target of 215 million achieved only twice in the last 30 years.
We’ve been slow to recognize the necessity of an ample female spawning population. Only recently has science debunked the assumption that female crabs spawned only once and thus could subsequently be harvested without limit or consequence.
Now crab managers have set commercial female harvest limits and banned recreational harvest of sooks. Since then, the blue crab population has tended to stability.
Another help in achieving stability was the establishment of two species-management benchmarks: a minimum threshold of 70 million female crabs and the target threshold of 215 million. Both figures are founded in good science.
The target threshold is the population level necessary to allow the species to be comfortably resilient to natural population fluctuations.
The minimum threshold is the critical level that, if crossed, could send the species spiraling into population collapse.
Numbers between the two thresholds don’t justify complacency. This year’s count of 190 million females does not make it safe to harvest females. It’s courting crisis to allow harvests that push the population down near the minimum level.
It’s easy to succumb to temptation to harvest more crabs. Maryland consumes virtually every blue crab harvested in its portion of the Bay, every year, plus some of the crabs harvested by Virginia and a substantial portion of the crabs harvested in North Carolina, South Carolina, Florida, Louisiana and Texas. In lean years, a bushel of crabs in Maryland can bring more than $300.
Maryland’s 4,000 licensed commercial crabbers have only a few months to make their annual income. It’s natural to want to make hay while the sun shines.
Further complicating conservation efforts is demography. Female crabs favor the southern, more saline portion of the Bay. Hence watermen there are far more dependent upon the sooks for their income.
All of these factors translate into intense pressure to allow generous female harvests — despite their critical value to the overall population.
So I’m arguing that this year’s achievement makes a fine foundation for an even-brighter future. There is plenty of room in the Chesapeake for an expanded crab population. Not too long ago, our Bay held more than twice as many blue crabs. It is neither naive nor optimistic to manage more forcefully toward numbers just as high.