Freshwater Shellfish

This page lumps together representatives from crustaceans and mollusks. Freshwater typically has lower diversity than the ocean. However, this is just a tiny sample of what may be found.
 

Freshwater also contains an entire phylum of microscopic creatures known as rotifers.
Rotifers are exclusively freshwater predators which swim by means of cilia.
Their relationship to other animals is not clear.

 

Eastern Crayfish

Cambarus bartoni

Size: to 3"

Habitat: small streams, sometimes ponds and lakes

Notes: Active at night, hides in burrows or under objects during the day.

Compare freshwater crayfish with marine lobsters.

Crayfish are quite common at Dutch Springs. See lobster for anatomical details.

Blue coloration is the crayfish equivalent
 of albinism, and also occurs in lobsters.
Individuals like this have little chance
of surviving in the wild.

 

Miscellaneous Crustaceans

Look very closely, and you may see swarms of Daphnia ( right ) swimming jerkily through the water as they feed on microscopic algae. These tiny "water fleas", are an important link in the food chain, converting plant plankton into animal.

Tadpole shrimps ( far right ) grow much larger than daphnia, up to 1 inch. They are capable of swimming, but are usually found crawling on the bottom, on plants, or burrowing. Their eggs are highly resistant to drying, which makes Tadpole shrimps well-adapted to life in temporary pools.

Freshwater shrimps are similar to their saltwater cousins, and are usually small ( 1-2" ) and transparent.

Various Cladocerans ( not quite microscopic )

 

Apple Snail

Pomacea paludosa

Size: to 2"

Habitat: quiet waters

Notes: The largest freshwater snail in the area.

 

River Snail

Goniobasis virginica

Size: to 1"

Habitat: flowing water

 Notes: This is one example of the many small snails you may find during a freshwater dive. They are very common in Round Valley Reservoir, which is filled from the Raritan River.

 

Pearly Mussel

Elliptio crassidens

Size: to 6"

Habitat: dug into muddy or sandy bottoms in quiet waters

Notes: This is actually a freshwater clam.

 

Zebra Mussel

Dreissena polymorpha

Size: to 2"

Habitat: grows profusely on any solid surface

Notes: Zebra Mussels were introduced into the Great Lakes in the mid eighties from the Caspian Sea region of Eurasia. They probably arrived as larvae in the ballast water of visiting ships. Since then, they have been having a regular party - spreading like wildfire and often covering every available hard surface, including each other. This wreaks havoc with power-plant cooling systems and municipal water supplies, where masses of the tiny bivalves clog pipes and water intakes. The mussels also radically alter the native lake ecology by efficiently filtering nutrients from the water. This does have one positive effect for divers, however. Apparently, the Great Lakes and surrounding waters have never been cleaner or clearer.

Zebra Mussels growing underneath one of the platforms at Dutch Springs.