Cahaba Animals

 

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Pictured at top: Bluegill Sunfish

 

Map turtle
 

 


Stinkpot turtle

 


 

 

 

 

 

Caddisfly larvae

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Waterstrider

 

 

 

 

 

 


Waterpenny

This page describes some of the Cahaba River's animals.

Mussels

Mussels are freshwater mollusks that have a shell separated into two symmetrical valves.  Inside these valves are a soft body and gills.  Mussels are very similar to clams.

 

Historically, 42 mussel species were found in the Cahaba River.  Their populations once fueled a million-dollar industry in Alabama.  Unfortunately, barely half of these species (27 to be exact) are now found in the river.  Eleven of these mussel species are recognized as endangered or threatened by the U.S. Fish and Wildlife Service.

While mussels may be hard to notice in the river (they burrow down into the sediment) they play an important role in the ecosystem.  Mussels filter river water, helping to keep it clean for other species and for us.  Many are a source of food for large animals that feed in the river.  Mussels are also  important to us as an indicator of the health of the river. Unfortunately, because many of our rivers have been so heavily damaged by damming and pollution, many of the nation's and Alabama's mussel species are extinct.

Mussels have an elaborate mating method that is truly bizarre. The male mussel releases his sperm into the water to fertilize the female's eggs.  The fertilized eggs grow in the mom's gills until they are mature.  But the mother must make sure the larvae survive and find the proper habitat into which to settle. Thus, she cannot just release them or they end up far downstream.  This is when unsuspecting fishes play a critical role.  The female mussel essentially tricks fishes into transporting her offspring to a new place in the river.  The female mussel will grow a fleshy lure on her body that resembles a small meal for a large fish. 
Some of the lures resemble minnows, while others resemble crayfish.  Mussels pack the lure with larval mussels, and when a fish takes a bite, the packet of larvae explodes in the fish's mouth and the larvae then attach to the fish’s gills.  Other mussels keep the lure close to their body, and when the hungry fish approaches, the female squirts her larvae at the fish and the young mussels attach to the fish's gills.  Once secure inside the fish, the young mussels continue to grow and eventually drop off when the fish have unknowingly transported them to the proper habitat for the mussels.  This way the mussels are able to send their offspring upstream against the current. The only problem with the fish-mussel relationship is that when a fish species declines, so do the mussels species that depend on it.

 

Mussel Slide Show

Visit our Mussel Slideshow to see images of many mussel species found in the Cahaba River. These images may help your students identify mussel shells they find in the river on field trips.  When the file opens, click on the numbered slides in the far left column to view the slides.

 

 

 
fishes   

Above Picture: the Cahaba Shiner

The Cahaba River is known for its fish diversity.  The river contains the greatest diversity of fish species per mile than any other river in North America.  There are 131 species of fishes found in the Cahaba River, and eighteen are endemic, meaning they are found nowhere else in the world.  The Cahaba shiner was one of these endemic fishes.  Unfortunately, the Cahaba shiner is no longer found in the Cahaba River.     
(Left Picture: Blue Shiner) Many other fish species are no longer found in the Cahaba River.  Fish and other aquatic organisms are suffering because of declining ecological conditions in our watersheds.  Chemicals (like heavy metals, fertilizers, pesticides) and sediments (silt and sand) are being dumped into rivers through rainfall and runoff from cities.  Blue shiners used to be one of the most common minnows in the Cahaba and are  now considered threatened under the US Endangered Species List.  Like many other of the unique fishes in the Cahaba, these shiners have an unusual reproductive strategy.  They are called crevice-spawners The Blue shiner females spray their eggs into the crevices and cracks of of rocks, boulders, wood, etc.  This protects the eggs from predators.  In rivers where siltation is a problem, sediment builds up in the crevices of rocks and the shiners have nowhere to lay their eggs. 

Other fish species have declined in the Cahaba River for different reasons. The Alabama shad and Atlantic sturgeon  used to migrate from the Gulf of Mexico to the Cahaba River for spawning, but are no longer able to reach their spawning habitats due to damming on the major rivers below the Cahaba River.

Fishes come in an array of sizes and shapes.  Some fishes are slim, while some are a little thicker.  Some fishes' mouths are on the bottom of their heads, while some have mouths more toward the center.  The shape and size of a fish correlates with what food it eats and where it lives in the river.  Fishes vary in their eating habits.  Most fishes are omnivorous, eating many kinds of foods.  Others are more specialized, eating only vegetation, invertebrates, or other fish.  Some fishes feed on the bottom of the river (these are called bottom-feeders), and some fishes dwell at the surface of the water to get their food. 

   
   

INVERTEBRATES

Invertebrates are animals lacking a backbone and spinal cord.  There is a tremendous diversity of invertebrate species that live in our rivers and they are essential to maintaining the health of the river's ecosystem.  Every organism in the river has a role in the ecosystem and is part of the river's food chain.  The invertebrates usually make up the lower regions of the food chain since they are some of the smallest organisms in rivers.

Picture above: Dragonfly larvae

Figure at right: Aquatic invertebrates occupy the second-lowest tier on the adjacent food pyramid.

Larger animals eat the invertebrates, while the invertebrates eat detritus and microscopic plants and animals.  As organisms eat one another, energy and nutrients flow through the ecosystem. 

Aquatic invertebrates can have elaborate life cycles.  The larval flies pictured at left go through three to four very different stages during their lifetime, eventually becoming flying adults that hardly resemble the larval stages. 
Aquatic insects live on, between, and under stones and logs in rivers.  Though they are small, aquatic insects have developed certain adaptations to live in fast moving waters.  For example the blackfly larvae attach themselves to stones, and mayflies have small claws that allow them to hang on to rocks when the current is strong.  Aquatic insects can be found in rivers of all temperatures, but they are especially common in temperate rivers, such as the Cahaba River.  They can even be found during the wintertime when the water is at its coldest temperature. 
Crawfish, are crustaceans like crabs, shrimp and lobsters.  Crawfish are common invertebrates in rivers.
Crawfish, also known as crayfish and crawdads to many people, are alive and well in the Cahaba River, just as they are in other central, eastern, and southeastern parts of the United States.  There are 24 species of crawfish in the Cahaba.  Crawfish can be 10-150 mm long, and come in various colors such as black, brown, red, blue, orange, and green.  Crawfish use their pincers to grab and tear-up their food.  They are omnivores, eating a variety of foods such as snails, insects, small fishes, carrion, and vegetation.  Crawfish, as a group are are very versatile, but some species require very narrow environmental conditions.  They live in areas of different temperatures and have a mixture of habitats. Crawfish often dwell under rocks or in holes they dig.
 

Identification of Aquatic Invertebrates

Follow the link to pictures and descriptions of common  and important aquatic invertebrates.  This pamphlet can you and your students identify the types of invertebrates that you will likely find when exploring your local stream or river.  Click here:  Identification of Aquatic Invertebrates

 

Sources used: Draft Interim Report- Natural Resources/Conservation Committee
U.S. Fish and Wildlife Service
Explore the Cahaba River- CRS Pamphlet
2717 7th Avenue S.
See References for other sources


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