Just Offshore

This display focuses on the prehistoric connection between the formation of the Chesapeake Bay and the ancient Susquehanna River valley. The Susquehanna once extended to the edge of the continental shelf, when sea levels were much lower. This channel is still present in the modern day underwater formation called Norfolk Canyon.

Animals living in this offshore habitat are able to tolerate moderate pressures and cooler temperatures associated with living at depth in the ocean. Most can be found in the shallower waters around the mouth of the bay, at least seasonally. Come learn more about the formation of dead zones in the deeper water.

Only a select few of these species are on exhibit at any time, though all are representative of Just Offshore habitats.

Chain dogfish

Scientific name: 
Scyliorhinus retifer

Chain Dogfish

Habitat: The chain dogfish prefers structured habitats including rocky bottoms as well as living among man-made artifacts such as wires and cables.

Key characteristics for distinction: The chain dogfish is small with a slender body and wedge-shaped, blunt-tipped snout. The eye is narrow and somewhat oval in shape. The origin of the first dorsal fin is somewhat behind the free rear tips of the pelvic fins. The second dorsal fin is approximately half the size of the first dorsal. The pectoral fins are as broad as they are long with rounded corners. The outer margin is slightly convex and the distal margin is straight. The anal fin is subtriangular with nearly straight edges and a rounded apex. The small caudal fin has a square tip or indented at the midline. The caudal fin also has a defined subterminal notch. The surface of the skin feels smooth to the touch.

Coloration: The coloration of the chain dogfish distinguishes it from all other sharks. The body is reddish-brown along the back and a yellowish shade on the underside. There is a chain-like pattern of black or dark brown lines on the back and sides of the chain dogfish. This coloration pattern helps this species blend into its bottom habitat. The eyes are yellowish-green.

Feeding habits/specializations: Chain dogfish feed on squid, small bony fishes, polychaete worms, and crustaceans.

Reproduction: Egg-laying. Follicles are ovulated in pairs. Each pregnant female releases two box-shaped egg cases after an unknown gestation period. Each egg case, also referred to as a mermaid's purse, has long stringy tendrils at each corner. The egg case is amber in color. Prior to release of the egg cases, the mother searches for bottom habitat with gorgonians and sponges or man-made structures for the tendrils to snag. These benthic invertebrates or structures provide an area to secure the egg cases. Adult chain dogfish often congregate in these nursery areas where females release egg cases. After the egg cases are released, there is no further parental involvement. The embryos are released from the egg case about 250 days later.

Maximum length (in inches or feet): 20 in

Predators: larger fish

Importance to humans: aquarium use

Conservation status: least concern

Fun fact: The common name "chain dogfish" is actually a misnomer as this shark belongs to a group referred to as catsharks.

Sources: fishbase.org, flmnh.ufl.edu