Marmorkrebs: The Crayfish Almanac

30 January 2025

The Crayfish Almanac

Don’t know how I missed this last year, but Michigan State University released Great Lakes Almanac to Invasive Crayfish.

It has one of the best short identification guides for Marmorkrebs I’ve seen. Click to enlarge!

Marbled crayfish (or marmokrebs) originated in the aquarium trade and are often called the self-cloning crayfish. All marbled crayfish are female and the offspring are clones. This species is of high concern because a single individual can produce an entire population in a short time. This species has a distinct marbling pattern, but other species may look similar. Male crayfish with this pattern are not marbled crayfish. To determine if its a female, look for a round pocket-like feature located on the underside between the last pair of walking legs. This is the sperm pouch (called an ‘annulus ventralis’) .

Marbled crayfish (or marmokrebs) originated in the aquarium trade and are often called the self-cloning crayfish. All marbled crayfish are female and the offspring are clones. This species is of high concern because a single individual can produce an entire population in a short time.

This species has a distinct marbling pattern, but other species may look similar. Male crayfish with this pattern are not marbled crayfish.

To determine if its a female, look for a round pocket-like feature located on the underside between the last pair of walking legs. This is the sperm pouch (called an ‘annulus ventralis’) .