Spiny Dogfish Essay Example

and both fins have spines at their origin. The caudal fin is asymmetrical with the upper lobe being larger.

The smooth edged short and oblique teeth are similar in both the upper and lower jaw. ” Habitat: They prefer to have temperatures from 45 to 55 degrees Fahrenheit. Spiny dogfishes are located inshore and offshore of the continental and insular shelf and upper slopes and are usually found near the bottom (but also in mid-water and at the surface). Dogfish are often found in enclosed bays and estuaries. Life span: Dogfish are long-lived - males live up to 35 years and females live up to 40 years.

Food: Spiny dogfish eat a wide variety of prey. Herring, mackerel, squid, silver hake, and comb jellies constitute the major portion of their diets. Cod, haddock and flatfish are relatively uncommon by comparison. Spiny dogfish also prey on flatfishes, blennies, sculpins, jellyfish, polychaetes, sipunculids (group of marine worms), amphipods (small, shrimp-like crustaceans), shrimp, crab, snails, octopods, squids, and sea cucumbers. Growth rate: Slow; females grow larger then males.

Maximum size: Males grow up to 3. 3 feet, and females grow up to 4 feet. Reaches reproductive maturity: Spiny dogfish Males reach maturity at 6 years and 23 inches; females reach maturity at 12 years and 30 inches. Reproduction: Females each have 2 to 12 eggs per season. They bear live young, after a gestation period of about 18 to 24 months, and typically produce 2 to 15 pups, with an average of 6. Spawning season: Winter Spawning grounds: Offshore waters Migrations: “Related to water temperature.

Dogfish are found in North Carolina and southern New

England during spring and autumn but migrate northward to the Gulf of Maine-Georges Bank region and into Canadian waters in summer and southward in autumn and winter. Mature dogfish also school by size and sex. ” Predators: Predators of dogfish include a variety of shark species including sixgill, sevengill, leopard, and great white; a variety of larger fishes such as lancetfishes and some rockfish; and some marine mammals.

Commercial or recreational interest: Both, although recreational only when preferred target species are unavailable. Distinguishing characteristics: Dogfish are slim, with a narrow, pointed snout and characteristic white spots. They have two dorsal fins with unproved large spines and are colored grey above and white below. Additional Information: Role in the Ecosystem “Spiny dogfish are top level predators. They are an opportunistic feeder, taking whatever prey is available.

Smaller dogfish have been reported to eed primarily on crustaceans, while larger individuals tend to feed on fish. Fish, mainly schooling pelagic species, constitute 50% of their diet. Despite possessing venom-delivering spines on each of its two dorsal fins, spiny dogfish are preyed upon by cod, red hake, goosefish, other spiny dogfish, larger sharks, seals, and orcas. ” Geographical Distribution Spiny dogfish are found in the western Atlantic Ocean from Greenland to Argentina and in the eastern Atlantic from Iceland and Murmanski Coast (Russia) to South Africa including the Mediterranean Sea and Black Sea.

In the western Pacific Ocean, the spiny dogfish occurs from the Bering Sea to New Zealand while in the eastern Pacific, this species is found from the Bering Sea to Chile. Biology Distinctive Features The spiny dogfish has a slender, elongate body and

a moderately flattened head. The snout is narrow, tapering to a pointed tip. The eyes of this dogfish are moderately large. The first dorsal fin is located about halfway between the pectoral and pelvic fin origins and behind the rear tips of the pectoral fins. The second dorsal fin is about two-thirds the size of the first and is located behind the pelvic fins.

There are sharp dorsal fin spines at the anterior margins of the dorsal fins with the first about half as long and the second nearly as long as the anterior margins of their respective fins. The pectoral fins form nearly perfect equilateral triangles with rounded rear tips and slightly concave rear margins. The pelvic fins are closer to the second dorsal fin than the first dorsal. There are low lateral keels located on the caudal peduncle. There is no notch on the upper caudal lobe and the lower caudal lobe is not well-developed. There is no anal fin on the spiny dogfish.