Shovelnose Sturgeon

Shovelnose Sturgeon

Friends of Bighorn Lake

 

Characteristics
The distinctive Shovelnose Sturgeon (Scaphirhynchus platorhynchus)has a flattened and indeed a shovel-shaped snout. Bony plates instead of scales give it a reptile like body surface. These scutes are in five rows: 14-19 dorsal plates, 38-47 lateral plates along the sides and 10-14 ventrolateral scutes along the lower side of the body. The area in front of the tail is entirely covered in these bony scutes. The belly is also covered in plates that distinguish it from the Pallid Sturgeon which does not have them on the belly.

Shark-like features include a torpedo shaped body that seems stretched out and a skeleton composed of cartilage instead of bone. The Shovelnose has a sucker type mouth and halfway between the mouth and the tip of the snout are four barbells arranged in a line. The outer barbells on the Pallid Sturgeon are placed further back than the inner barbells. The barbells sense the bottom and help identify food. They are tan to gray or yellowish green on top which shades to grayish white on the belly.

The Shovelnose may grow up to about 15 pounds and two and a half to three feet long, while the Pallid Sturgeon can exceed 100 pounds. Anglers need to know the differences beside weight so that they can immediately release any young Pallid Sturgeon they might catch.

Territory
Shovelnose Sturgeon can tolerate high levels of turbidity and are usually found in strong currents and deep channels of large rivers. Its native range in the Mississippi and Missouri river basins and their tributaries definitely provides lots of suitable habitat, but various locks and dams have contributed to its range reduction often because they block access to those sturgeon migrating upstream to spawn.

They are usually sedentary but occasionally move 7 to 10 miles in one day. They feed on any aquatic insect larvae (especially mayflies, true flies and caddis flies), leeches, mussels, worms, crustaceans, fish eggs, and minnows. Being bottom feeders and not inclined to jump, they are not well adapted to use most fish passage features.

Spawning
Spawning usually occurs between April and early July with the bulk of it taking place in June. Spawning takes place over gravel in fairly swift water at temperatures between 60 and 70 degrees F. Females usually do not spawn until they reach seven years of age or older, while males will typically start spawning at age five. Females do not spawn every year and most typically only every third year, but when they do they will produce 10,000 to 50,000 eggs.

Since fertilization occurs externally some hybridization with Pallid Sturgeon takes place. The adhesive eggs incubate for about a week, and then the fry drift downstream to suitable places to grow. While some Shovelnose may reach the age of 40, most only live to an age of about 12 which means many females only spawn three times during their lifetime.

200 Million Years Old
The Shovelnose is a member of one of the oldest known fish families and can be traced back over 200 million years. Numerous dams and diversions on the North Platte and Bighorn Rivers are likely the reasons the Shovelnose is no longer found in the upper reaches of these rivers.