Oil Spill Wildlife Spotlight: Blue Crab and Shrimp

 

As is the case for many nesting bird species, the Gulf oil spill’s timing is also bad for blue crab, which are currently spawning offshore. Whereas its impacts on birds can be blatantly obvious, however, the spill's effects on blue crabs may not be as apparent to the average (horrified) onlooker. Richard Condrey, an associate professor at in the Department of Oceanography and Coastal Sciences at Louisisana State University, is largely concerned about the oil that’s been broken up by dispersants and the effect it could have on their food source, which consists primarily of diminutive invertebrates that live in the sand, such as snails and mole crabs. The accumulation of toxins in these small organisms could hamper their reproduction—and a decline in what blue crabs are eating could then hinder their own growth and survival.

 

Further, contaminated food could also affect blue crab reproduction, thereby impacting the next generation. Females undergo a single mating event to tide them over for the rest of their lives. After fertilization by males, females store the sperm and use it periodically throughout their life cycle, which, from April to October, basically entails eating and spawning on shoals of about 20 fathoms (120 feet) and shallower. (Based on current research, males generally stay up in the estuaries, in fresher water areas where they mate.) The toxins in dispersed oil are “lipophilic,”* says Condrey (in other words, they mingle well with fat), so if they ingest tainted food, female blue crabs will inadvertently put the viability of their eggs and stored sperm—both packed with lipids—at risk. "You could find that there’s an inordinate number of eggs being laid that aren’t fertile,” says Condrey.

 

Condrey is also concerned about the fate of shrimp, specifically white and brown ones (pink shrimp don’t dominate in Louisiana), which are also currently spawning offshore. As is the case with blue crab, dispersed oil could affect shrimps’ food source, and ultimately their own survivorship and reproduction.

 

While female blue crabs store sperm for posterity’s sake, white and brown shrimp don’t. Instead, females mate and spawn multiple times into the fall. That means that males have to keep up by constantly producing sperm—which could become intoxicated if males eat food affected by dispersed oil.
 

Louisiana is also the U.S. center for white shrimp production, and it boasts the highest number of brown shrimp, too. If it’s any consolation to the seafood-loving public, however, most of the shrimp* we consume come from elsewhere in the world. Let’s just keep our fingers crossed that the oil doesn’t get swept into that Loop current.