Ocean Watch

Monday, June 23, 1997

A Wisconsin trip yields
a very crabby argument

I didn't expect it, but during my visit to Wisconsin last week, some aspect of the marine world cropped up nearly every day. It reminded me that even people who don't live in Hawaii or on the coast still have connections to the world's oceans.

One day while walking on the sandy beach of one of Wisconsin's many lakes, I spotted a newly dead crayfish drifting near the water's edge. I picked up the 4-inch-long animal.

"It's a crab," said a friend who had grown up near the lake.

"Actually, it's a crayfish," I explained, turning over the lobsterlike animal.

"We always called them crabs," she told me.

I thought for a moment. Who am I to argue with local common names? "OK, you call them crabs and I'll call them crayfish."

She shrugged. "Fine. But they're crabs."

I smiled and let it go, remembering that the language of common names is a confusing one. New Zealanders and Australians, after all, call lobsters crayfish.

In the study of marine biology (at least in my textbooks), crabs, crayfish, lobsters and shrimp are close relatives, all belonging to a group of crustaceans called decapods, meaning 10 feet. Most decapods are marine, but some shrimp, a few crabs and all crayfish live in fresh water.

Crayfish are the most successful of the freshwater decapods, evolving into more than 500 species in the world's streams, lakes and ponds. Some live under stones or debris, but others build burrows which they use for retreats and for overwintering.

Most crayfish are less than 4 inches long, but one type in Australia reaches the size of lobsters. This may be why folks there use the two names differently than North Americans.

Like crabs, crayfish eat most anything they can find, scavenging on dead organic matter and catching small fish and invertebrates. Unlike crabs, however, or any other decapod for that matter, crayfish antennae glands can excrete urine that is less salty than their bodies. This plays an important role in these creatures' salt balance.

A few days after my crayfish find, I was strolling along a path next to a creek I played in as a child. A flash of a large fin stopped me in my tracks, and before my astonished eyes, an enormous fish, over 3 feet long, swam to the water's edge.

With its two chin whiskers busily probing, the fish soon began to loudly suck mud.

The fish was a common carp, a native of Europe and Asia that was introduced to North America in 1831 and is now nearly everywhere. It grows to 4 feet long.

Because carp root in mud for organic wastes, thus increasing the turbidity of streams and ponds, the presence of these aliens can decrease populations of native fish. Most people now consider carp a giant pest.

I considered this particular one a blessing, though, because right after it left the bank, a mature painted turtle appeared from the stream depths to forage in the fish's wake.

The turtle had orange stripes between the green scutes on its back, yellow markings on its face, neck and legs, and long, sharp-looking claws.

I watched the turtle struggle with a loose crayfish claw uncovered by the carp's rooting. It nibbled on this for a while, then it moved to graze on some nearby algae.

I was thrilled to see this 10-inch ancestor of the sea turtles I like so much.

After it took off, I hurried to a nearby bookstore to see if they had anything about freshwater turtles.

I found a book on reptiles -- next to two books about whales and dolphins.

In the Wisconsin home of my childhood, reminders of the ocean are everywhere. Still, it was too far away for me.

It's good to be back in Hawaii.