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Marine Life Encyclopedia

Sharks & Rays

Spiny Dogfish

Squalus acanthias

Distribution

Atlantic, Pacific and eastern Indian Oceans, Mediterranean Sea, Black Sea

ECOSYSTEM/HABITAT

Coastal to offshore waters

FEEDING HABITS

Foraging predator

TAXONOMY

Order Squaliformes, Family Squalidae

The spiny dogfish may go by many names, including piked dogfish, rock salmon and spiky dog, but only one truly represents this shark’s unique defense strategy. Using sharp, venomous spines in the front of each dorsal fin, the spiny dogfish is a small but mighty predator that isn’t afraid to take a jab at passing fish. They are considered one of the most abundant living shark species in the ocean, but are harmless to humans.

Dogfish sharks make up the second largest order of sharks at 119 species. Sharks that are grouped into the dogfish family are so named because fishermen have observed these species chasing down smaller fish in dog-like packs. Schools of dogfish sharks numbering in the hundreds swim close together during the day, hunting herring, mackerel and capelin, as well as squid and jellyfish in some cases. Despite sharp spines, this dogfish consumes its meals by biting down on prey with sharp teeth and a strong jaw. Scientists believe that spiny dogfish eat less in the winter months when they swim in extreme depths of up to 2,900 feet below the surface. During spring, the sharks will return closer to the surface looking a little thinner, but will quickly move to warmer, coastal waters for summer feeding.

With a slender body and pointed snout, the spiny dogfish is a compact shark species reaching a maximum of 39 inches in males and 49 inches in females. Their skin is grey to brown on top and becomes increasingly paler, or even white, on the belly with small white spots running down each side of the body. The spiny dogfish is a highly migratory species–one individual tagged in Washington made a 5,000-mile journey to Japan. The spiny dogfish also breaks records when it comes to gestation. These sharks have the longest pregnancy of any vertebrate at 22 to 24 months, or two years! Eggs develop in the female, gaining nutrients from yolk sacs, and live young are born at 20 to 33 centimeters. Even at a young age, newborn spiny dogfish pups may hunt fish two or three times their size. Predators of the spiny dogfish include larger sharks, seals, orcas, cod and red hake. To defend itself, the spiny dogfish may inject venom into predators from the two spines near the dorsal fins. Humans are only at risk if they improperly handle these sharks.

Based on evidence of over-exploitation in their range and bycatch fisheries, global population of spiny dogfish are considered vulnerable by the IUCN Red List. Global populations have declined by more than 30 percent over the last 75 years. In some parts of the world, this shark has been targeted for its meat and fins. In 2014, Oceana applauded steps taken by the Atlantic States Marine Fisheries Commission to prohibit the finning of spiny dogfish. Other fisheries take the spiny dogfish as unwanted bycatch before discarding them back to sea.

Fun Facts About Spiny Dogfish

1. Pacific spiny dogfish reach a maximum length of 4.5 feet (1.4 m) and maximum weight of 22 pounds (10 kg).

2. Pacific spiny dogfish can live more than 80 years, while the Atlantic spiny dogfish only lives for 35 to 40 years.

3. Female spiny dogfish in the Pacific Ocean don’t reach sexual maturity until age 35. Males reach maturity much sooner at age 19.1

4. Atlantic spiny dogfish can be found anywhere from the surface to more than 3,000 feet (914 m) deep.2

5. Spiny dogfish were named after their tendency to hunt in dog-like packs.3

6. Female spiny dogfish are pregnant for 18 to 24 months, giving them one of the longest gestation periods of any vertebrate.

7. Spiny dogfish have sharp, venomous spines in front of both dorsal fins.4

References:

1 NOAA Fisheries – Pacific Spiny Dogfish

2 NOAA Fisheries – Atlantic Spiny Dogfish

3 Florida Museum

4 Monterey Bay Aquarium

IUCN Red List

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