Nature Bulletin No. 663-A   January 21, 1978
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

****:THE STURGEONS

All stories about sea monsters do not come from sailors who saw a 
strange beast a long time ago in a distant part of the world. Some start 
on our very doorstep. Every few years some excited Chicago vacationer 
babbles about a huge creature that he saw leap, splash, and beat the 
water into foam right in front of his eyes. This is good news. It means 
that the lake sturgeon is not yet extinct.

The sturgeons are primitive fishes whose fossil history can be traced 
back for fifty million years. Instead of overlapping scales, they have 
five lengthwise rows of heavy bony shields and a head covered with 
bony plates. The rest of the skeleton is cartilage or gristle, as in the 
sharks. Also like the sharks, the spinal column continues into the upper 
lobe of the tail. On the underside of the snout are four fleshy barbels or 
feelers that drag the bottom and locate the snails, clams, crayfish, 
worms and insect larvae on which it feeds. Behind these is the tube-like 
mouth which sucks up food like a vacuum cleaner.

The lake sturgeon is the giant of inland freshwater fishes and one of the 
oldest living animals in the world. The largest recorded from Lake 
Michigan in recent times was killed by a boat propeller near the mouth 
of the St. Joseph River in 1943. It was 7 feet, 11 inches long and 
weighed 310 pounds. Another with a weight of 215 pounds was 152 
years old when it was caught in 1953.

The great size and power of the lake sturgeon was one of the causes of 
its undoing. In early days the commercial fishermen of the Great Lakes 
destroyed them because they ripped and tore their nets. Later it became 
valuable and is now the highest-priced freshwater fish on the market. 
Becoming scarcer and scarcer in spite of many years of legal protection, 
the present annual catch from the Great Lakes is less than one percent 
of the amounts taken formerly.

The threatened extinction of the lake sturgeon is due in large part to its 
late maturity, Females do not spawn for the first time until they are over 
20 years old. After that they breed at only 5 or 6-year intervals. Besides, 
many of the tributary streams in which they formerly spawned have 
been blocked by dams, choked with silt, or polluted.

That famous delicacy, caviar, is made from sturgeon roe. Those black 
eggs, each about one-eighth inch in diameter, are freed from the 
membranes of the ovary and merely treated with salt. A 14-ounce can of 
genuine imported Russian caviar sells for $175. The domestic product 
is cheaper. Russia is the world's largest producer and exporter.

In addition to the smoked flesh, several other products come from the 
sturgeon. The air bladders are dried to produce the isinglass used to 
clarify wines and beer. Oil is rendered from the fat; the gristly skeleton 
is made into glue. The skins can be tanned to make a fine grade of 
ornamental leather.

The sturgeon family of fishes has about twenty living species, all 
restricted to the northern hemisphere.  Seven of these are found in 
North America: two on the Atlantic Coast; two on the Pacific Coast; 
and three in the inland lakes and rivers.

The largest of all American fishes is the white sturgeon of the coastal 
waters and rivers of the Pacific Northwest. A 12-foot female tipped the 
scales at 1285 pounds and others, in the past may have approached a 
ton. The largest sturgeon of all was a beluga from the Volga which 
weighed out at 3221 pounds.