Crayfish Predators in Northern America

Text by Roger F. Thoma

   
Mudpuppy

This is a picture of a mudpuppy (Necturus maculosus) from Conneaut Creek in Ohio. I caught this male in July (2000). Mudpuppies are very fond of crayfish and like to eat the small young ones. Mudpuppies are salamanders that retain their gills as adults (neotenic = retain characteristics of
youth). Many people are afraid of them and think they are poisonous. Only if you eat them raw will they make you sick. Just thinking about eating them raw makes me sick!

Mud puppies live under large rocks, just like crayfish and have a life span of over twenty years. This one is about 45 cm. long and probably over ten years old. I was out sampling with Dr. Tim Matson when we caught it. Tim is
curator of vertebrates at the Cleveland Museum of Natural History. Don't hold that against him, he likes crayfish to!




 

 Hellbender

This is a picture of a Hellbender (Cryptobranchus alleganiensis) captured down at my "secret laughing spot". I'd tell you were that is but I worry that a collector may go out there and catch them to sell in the aquarium trade. They are not common. This one was 54 cm. long, a really big one and was with another smaller one (they mate in August here in Ohio). They were found under a rock about 1.5 m. X 3 m. and 15 cm. thick. It took three of use to lift it.

It seems their principle food is crayfish and other smaller hellbenders. These salamanders (totally aquatic) can only be found in very clean, silt free, undisturbed streams in the Ohio River basin. There is a subspecies found in the Ozark Mountains area of Missouri. Many people think they are poisonous, and like mudpuppies, they kill them when the catch them while fishing. When upset they will try to bite and they exude large amounts of mucus which may be an irritant (so don't lick them!).

This is the business end of a hellbender. The head is very flat and the eyes are small. Unfortunately for crayfish, their mouth is large.
Hellbenders have no gills. Oxygen is exchanged trough the highly folded skin seen here on the sides of the abdomen.

This is the stream I collected the hellbender in. It is one of the highest quality streams in Ohio. Note the small plants growing at the edge of the stream. This is water willow, a herbaceous plant that is actually growing in the stream. It filters great quantities of silt, removes nutrients and keeps healthy streams in good condition. When one finds large beds of this plant growing in a stream you can be sure it will have good fishing for smallmouth bass. Excess silt and nutrient will eliminate water willow streams and rivers.

 

This is the rock the hellbenders came from under. It's a big piece of sandstone. I think hellbenders may prefer to mate and lay their eggs under rocks in shallow water because its warmer there. The warmth probably makes the eggs develop and hatch quicker. 
Smallmouth Bass.

Micropterus dolomieui, Smallmouth bass are known to eat up to 80% of their diet in crayfish. In North America they are probably responsible for consuming more crayfish than any other species just by virtue of their large numbers. Crayfish here are so prolific, there is normally no suppression of their numbers by the myriad of animals that prey on them. Besides humans, animals such as owls, herons, mink, muskrats, raccoons, snakes, and many fish species relish a tasty meal of crayfish. The greatest impact to crayfish populations comes from pollution such as mud and sediment, nutrients from fertilizers, and toxic chemicals from industry and mining (especially metals and acid run off). In a healthy stream with lots of predators, crayfish have no problems maintaining their numbers.

Rock Bass



Here's a bunch of rock bass (Ambloplites rupestris) I caught on a limestone boulder breakwater at Fairport Harbor in Lake Erie. They're laying in the bottom of my live well. They're big-time crayfish predators and are known to eat up to 90% of their diet in crayfish. As the name implies, they like to live around rocks. At night they sleep under or between the rocks. They're a good sport species especially for kids. When I was thirteen I would ride my bike out to the country to fish the local streams for "rockies". It was
great fun and they're good to eat!
This month Enrique got pretty bad news. One morning he discovered that "something" has eaten all of his "outdoors" crayfish; the crayfish that he keeps outside in the college green house ( at The Los Angeles Valley College, California ). Nothing was left, only water and plants, and a big mess!. He set up a trap and...bingo!...He got the beautiful beast that you see in this picture. The raccoon was later released to the wild. The moral of it all is: you never go back to the crime scene, unless you're still hungry!

New picture from Enrique

   

Fish of the Great Lakes

Electro fishing on the Great Lakes