The Pacific spiny dogfish (Squalus suckleyi) is a common species of the Squalidae (dogfish) family of sharks and are among the most abundant species of sharks in the world. This species is closely related to Squalus acanthias and for many years they were treated as a single species. Recent research, using meristic, morphological and molecular data led to the resurrection of Pacific Spiny Dogfish as a separate species. The American Fisheries Society recommends the common name "Pacific Spiny Dogfish" for Squalus suckleyi over alternatives such as "Spotted Spiny Dogfish" and "North Pacific Spiny Dogfish" and "Spiny Dogfish" for Squalus acanthias.
The maximum length of a Pacific dogfish can be 130 centimetres (51 in), and they can live up to 100 years. Squalus suckleyi has a slower growth rate, larger maximum size, and later maturity compared to Squalus acanthias species. The slower growth rate and time of maturity could be related to the colder temperatures these sharks face. Pacific spiny dogfish prefer to be in temperatures ranging from 7 to 15 °C (45 to 59 °F). Dogfish are found all over the world, but the Pacific spiny dogfish are found mostly in the North Pacific Ocean. These areas range from Korea to Japan and Russia, as well as the gulf of Alaska down to Baja, California. They are known to be piscivores, eating other fish. Additionally, they are known to consume octopus, squid, and crustaceans.
Squalus suckleyi have a slow reproduction rate compared to other sharks, with their gestation period being roughly around two years. This makes the Pacific dogfish more vulnerable to threats since they take longer to reproduce.
Its distinctive snout, large eyes, and flattened head are just a few of the physical characteristics that give the Pacific spiny dogfish its distinctive look. The dogfish has a cylindrical shaped body. This type of shark also contains a unique body coloring. The top half of the shark has a gray color with scattered white spots while the bottom half has a white/light gray color. The scales of the dogfish is composed of the same material of shark teeth called dermal denticles, making the skin very hard and durable. The skin of the sharks used to be used as sandpaper once dried to do woodwork or even be used as leather, once the denticles are removed. Lastly, the Pacific spiny dogfish has a set of teeth specialized for grinding instead of tearing by the teeth being flat with sharp edges. If any of the teeth are worn down or broken, new teeth replace them from the two rows that are not being used to prey on other animals.
Dogfish in general live in three main areas of the ocean: the Pacific, Atlantic, and Indian ocean. While dogfish can be found all around the world, this specific type of spiny dogfish can be found in the Pacific Ocean. Spiny dogfish in the northern Pacific Ocean have recently been reevaluated and found to constitute a separate species, now known as the Pacific spiny dogfish.
The Pacific dogfish's habitat consists of bays, including inshore and offshore waters. Female dogfish are usually seen in inshore waters while smalls pups are seen maneuvering in offshore waters. These animals are usually spotted at the bottom of the continental shelf at the bottom of the sea. The Pacific dogfish prefers to live mainly in saltwater, but they can live in and tolerate brackish water (a mix of salt and fresh water).
Migratory patterns of Pacific spiny dogfish are not well understood. Analyses of tagged dogfish have shown a seasonal north-south migration along the west coast of the United States and Canada as well as a seasonal pattern of dogfish tagged in the inside waters of the Puget Sound repeatedly leaving that area for outside coastal waters in the summer.
Tagged dogfish released in Canadian waters off British Columbia were most often recaptured in the same area as released but 10 individuals were recaptured near Japan
Pacific spiny dogfish have been frequently captured over 1000 km from shore in salmon research gillnets in the North Pacific Ocean, suggesting that the trans-Pacific migrations from Canada to Japan could have passed through the open ocean rather than following the coast
The Pacific dogfish is an elasmobranchs or cartilaginous fish which includes sharks, skates and rays. Dogfish are carnivorous or meat eaters. Their teeth are sharp and are inclined laterally in order to cut through their prey. The Pacific dogfish usually eat mollusks or crustaceans such as squid, krill, and shrimp. They also eat other small sharks and fish. According to Jennifer Bigman, a marine scientist, there is no difference between what male dogfish eat versus what female dogfish eat. Their prey are usually found on the sea floor, so the Pacific spiny dogfish has to scan the bottom in order to invest in their prey. Elasmobranchs consume very little carbohydrates and glucose. During times of starvation, they rely on ketone bodies to give them enough energy to survive. Cartilaginous fish are able to endure severe hypoglycemia due to their ketone oxidation. Squalus suckleyi are able to eat more carbohydrates compared to other elasmobranchs. The rectal gland is activated when a dogfish consumes food. This gland helps the Pacific dogfish become glucose dependent. This means that they have the ability to break down a small amount of glucose.
The Pacific dogfish have a longer reproduction rate compared to other sharks, but have the same reproduction characteristics as Squalus acanthias. The gestation period for spiny dogfish is normally 18 to 24 months. Dogfish that live in cooler water may have an increased duration of pregnancy. Females are also known to migrate from deep to shallow water as the pregnancy continues. This migration pattern is known to influence embryonic growth. Baby dogfish, also known as pups, found near Newfoundland had an average of 1.1 cm/month and 24 month pregnancy period, while a warmer area such as Massachusetts had an average of 1.3 cm/month and 20-22 month pregnancy period. The sexual maturity of a dogfish is hard to determine because it varies anywhere from 10–30 years. Food supplies and water temperature also play a role in growth and development of the dogfish. The length of a newborn Pacific dogfish is around 22 to 23 centimeters. Females seem to be significantly larger than male dogfish. At sexual maturity the male dogfish is 60–70 cm while the female is about 70–100 cm. This length difference can be caused by the reproduction process of the female. Their bodies need to be bigger to carry and protect their eggs within their bodies. Pacific dogfish are ovoviviparous. This means that they produce eggs that hatch within the body. The size of the litter ranges from 1 to 20 newborns. Fertilization usually occurs from the beginning of October to the beginning of February.
The slow growth and low reproductive rates of Pacific spiny dogfish make them vulnerable to overfishing, but unlike the spiny dogfish found in other regions, which has been declared overfished in the past, stock assessments for the Pacific spiny dogfish in Alaska, British Columbia, and the West Coast of the United States have either found that the data are not informative about the stock status, or that the stock is not overfished and that overfishing is not occurring.
Dogfish have been harvested for subsistence use on the Pacific coast for centuries, but commercial fisheries first began targeting dogfish in the 1930s and commercial landings of Pacific spiny dogfish in the West Coast of the United States were highest in the 1940s, driven by a market for Vitamin A from shark liver oil. The mortality due to fishing was estimated to have peaked at over 15,000 mt in 1944 but rapidly declined in the years after that and remained below 3,000 mt for the years since 1950.
