Today on the James: Wildlife of the James

“There are crabs here?”

That’s the typical response during an eco-paddle trip when we find a blue crab in the James River just a few miles downriver of Richmond. The Blue crab, symbol and economic bastion of the Chesapeake Bay, can be found throughout the lower James, particularly in dry summer months. Male crabs are known to explore fartherr up the James than females, who prefer the salty depths in the middle of the Bay. The Blue crab, having fascinated and fed us well, bears a scientific name meaning “delicious beautiful swimmer.”

A few important facts about Blue crabs; they:

are a vital predator and prey item in the aquatic food chain
eat just about everything from fish to shellfish to vegetation to other crabs
are eaten by oysters, menhaden, striped bass, drum, and many birds at different stages in its life cycle
thrive in underwater grass beds that provide shelter for young and for molting and mating
have three pairs of walking legs, one pair of swimming legs, and a pair of formidable claws (the males are blue while the females have red tips)
mate after the female molts through her final “soft-shell” phase, during which the male cradles and protects the female
go through a planktonic larval stage in which they drift towards the ocean before they mature and swim back towards the Bay and its rivers
have been severely set back as a species by overharvesting, pollution, and the loss of aquatic grasses.

However…throughout the Bay, the Blue crab population appears to be rebounding as a result of stringent harvest restrictions. That’s great news for this fishery, which is worth over $24 million a year in Virginia alone.

Be careful what you eat.

Recently Virginia Commonwealth University researchers have found Blue crabs with high levels of microcystin, a liver damaging toxin produced by Cyanobacteria, or blue-green algae. The study is being conducted in the tidal, freshwater section of the James from Richmond to the Chickahominy River influx. The researchers are trying to determine whether the high toxin levels are constant or only high during the time of year when the river has large blue green algae blooms. Although the toxins levels found in the Blue crabs are high, these toxins do not stay in shellfish tissue for more than a few weeks. Low toxicity levels were also found in menhaden and blue catfish; however, researchers are unclear on why the levels are so high in the Blue crab.

Cyanobacteria is believed to be caused by nitrogen and phosphorus ‘runoff’, or pollution that is washed off streets, fertilized lawns and gardens into our waterways. In the worst cases an algae bloom can cause a ‘dead zone’ where it removes all of the oxygen in the water, suffocating aquatic life in the area.

Very little Blue crab harvesting takes place in the freshwater region of the James. The majority of the commercial harvesting takes place in the lower James where the salinity is higher, and presumably the toxin levels would be lower.

Researchers believe that microcystin found in the James is not a risk to humans, but they hope to learn more about the effect of the toxin as the study progresses.