|Family overview: Biologists say that sturgeons are the most primitive of the bony fishes alive today. Extinct sturgeon relatives date back more than 350 million years. Sturgeons are found throughout the Northern Hemisphere, in both fresh water and salt water. In some parts of the world, sturgeons are commercially valuable for their meat and for their eggs, which are used for caviar. Although they were once a more common part of our native wildlife, nowadays Pennsylvania sturgeons are rare. In Pennsylvania there are three sturgeon species: The shortnose sturgeon (Acipenser brevirostrum), the lake sturgeon (Acipenser fulvescens) and the Atlantic sturgeon (Acipenser oxyrhynchus).
The state-endangered shortnose sturgeon is a marine and estuarine fish. It is found in Pennsylvania when it returns to the Delaware River to spawn. Some adults overwinter in the tidal Delaware as well. Juvenile sturgeon also inhabit the nursery water of the tidal Delaware. Past exploitation by commercial fishermen, pollution of tidal streams and estuaries used by spawning adults, and habitat loss have led to its reduced numbers. The lake sturgeon is also a state-endangered species, found primarily in fresh water. Although it once was seen in the Ohio and Allegheny River watersheds, in recent years it has been found in Pennsylvania only in Lake Erie. Pollution, and locks and dams across the large rivers it prefers, which block access to spawning grounds, have been responsible for the lake sturgeon’s decline. The Atlantic sturgeon is a endangered species in Pennsylvania. As different subspecies, this sturgeon ranges along the Atlantic Coast from Labrador to the Gulf of Mexico. The Atlantic sturgeon is found occasionally in the Delaware River in Pennsylvania, where the adults migrate to spawn and then return to the ocean. Juveniles also spend time there before going to the ocean.
Identification: Sturgeons are elongate, with a flattened head and snout, and seem to be five-sided. This is because they have five rows of bony plates running along the body, one along the back, two on the sides and two on the underside. The plates are sharp in young fish, but smooth with wear in older, larger fish.
Sturgeons have four soft barbels between the front of the snout and the toothless mouth, which protrudes to pick up food. The upper lobe of the tail fin is much longer than the lower lobe, and the dorsal fin is set far back toward the tail. The first ray of the pectoral fin is hardened into a bony spine. It is used by biologists to determine the fish’s age.
The shortnose sturgeon grows to about three feet. It is dark-brown or black on the back, lighter brown to yellow below. The large, bony scales along its sides are lighter than the body color, and the paired fins are outlined in white.
Lake sturgeons reach seven feet long, with olive-brown to gray on the back and sides, white underparts, and dark-brown to gray fins. The rows of bony scales on the top and sides are the same color as the body.
Atlantic sturgeons are the state’s largest fish. They reach a length of 12 to 14 feet. The upper body is gray or blue-black, and contrasts with the white spines on the body plates, the front edge of the paired fins, and the lower portion of the tail fin.
Life history: Sturgeons can live 50 to 100 years or more, depending on the species. However, they are slow to mature sexually, and there may be several years between each spawning. The shortnose sturgeon takes up to six years to mature. The lake sturgeon doesn’t spawn until it is about 15 years old. The Atlantic sturgeon doesn’t breed until it is at least 12 years old.
Sturgeon adults spawn in spring on a stony bottom in the fast current of large rivers. The lake sturgeon also spawns along the rocky shoreline of lakes. The tiny dark-brown or blackish eggs extruded by the female are adhesive and stick to the bottom. No nest is constructed by the adults. There is no parental care of the eggs or young fish. In the marine species, the juvenile sturgeon spend time in the brackish lower river and estuary, before heading for the ocean.
Even though they grow to great size, sturgeons eat tiny bottomdwelling invertebrates, like sludgeworms, midges, shrimp, tiny bivalves and occasionally small fishes. They root for food from the soft bottom with their snout, and locate food using their barbels. Atlantic sturgeons are travelers. One tagged fish journeyed 900 miles in a single summer.