Blue Crab Update

Every year, the Maryland Department of Natural Resources, the Virginia Institute of Marine Science, and the University of Maryland Chesapeake Biological Laboratory work together to monitor blue crab population during winter months. The results of this year’s dredge survey were just published, so let’s go over what they were and what they mean for this important crustacean.

First things first, the survey estimated an increase in the overall number of crabs as compared to last year. This is good news because last year had the lowest population estimates on record since the survey began over 30 years ago.

However, it doesn’t mean that everything is fine. As noted by the Maryland DNR, there hasn’t been a really good year in terms of the number of juvenile crabs since 2019, even though the number of females is high enough to produce a large number of baby crabs. This may mean that reproduction isn’t where we’d like it to be, or it may mean something is happening to all the baby crabs that are being born. Just like we discussed last year, this may be due to environmental conditions such as wind and currents keeping larval blue crabs from re-entering the Chesapeake Bay, or it may have to do with what’s going on in the Bay itself. Again, as discussed last year, the invasive blue catfish may be feeding heavily on juvenile blue crabs or there may not be enough habitat with good cover for juvenile crabs to hide in.

These numbers are a reminder that it’s not enough to just manage blue crab harvest in order to protect this important fishery. Blue crabs need underwater grasses during their vulnerable time as small, juvenile crabs. Weather conditions also play a role in yearly variability of populations and there’s not a lot we can do about that other than ensure we have a large enough base population to protect against bad years. We may also need to consider that natural mortality due to consumption by other animals may be higher, especially as blue catfish populations potentially continue to grow.

Image credit: Maryland DNR

Regardless, the survey did see an increase in blue crabs across the board – higher overall population estimates but also a higher number of females that should be spawning this year, a higher number of large male crabs, and a higher number of juvenile crabs. The hope is that last year was just a bad year for a variety of reasons and that the blue crab population will continue an upward trend after this year.

We are always going to see ups and downs in the estimated number of blue crabs in the Bay. However, what we want to avoid are trends where the down year population numbers get lower and lower over time. If we continue to see rising populations over the next couple of years and if the next downward trend suggests a larger blue crab population than last year, we should be ok to continue managing the blue crab fishery as is. However, if we continue to see bad years with extremely low population numbers, we may see fisheries managers make more drastic cuts to how many blue crabs can be harvested and when.

So, for the time being, we can celebrate that we saw an uptick in blue crab populations this year by enjoying locally caught blue crabs. We can also do our part to support a healthy blue crab population by eating locally caught blue catfish, which helps remove these invasive fish from the Bay and keeps more juvenile crabs in the Bay for future years.

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