Dogfish are a globally prevalent group of small sharks, most commonly referring to the Spiny Dogfish (Squalus acanthias) and the Smooth Dogfish (Mustelus canis). These slender, bottom-dwelling species inhabit temperate and subarctic continental shelves across the Atlantic and Pacific Oceans. Despite their relatively small size, they are highly abundant and play a significant role in their marine ecosystems. Their feeding habits are characterized by a flexible and opportunistic approach, allowing them to thrive in diverse environments.
Primary Prey of the Dogfish
The dogfish is a generalist predator, consuming a wide variety of available prey that shifts based on local abundance. A substantial part of their diet consists of small schooling fish, or forage fish, such as Atlantic herring, capelin, Atlantic mackerel, and bay anchovy. They also frequently target a diverse range of invertebrates. Common prey items include crustaceans (crabs and shrimp) and mollusks (squid, octopus, and various worms). Spiny Dogfish are known to feed on jellyfish and ctenophores.
Hunting Strategies and Feeding Methods
Dogfish are active hunters that often acquire food through coordinated group efforts. They form immense schools, sometimes numbering in the thousands, which they utilize to herd and corral schools of prey fish, making mass feeding efficient. Their mouth structure is well-suited to their varied diet. The Smooth Dogfish has rows of flat, pavement-like grinding teeth, highly effective for crushing the shells of crabs and mollusks. The Spiny Dogfish, by contrast, possesses short, oblique teeth capable of slicing flesh. These sharks also act as scavengers, consuming discards and readily taking advantage of available food sources, sometimes feeding voraciously on fish caught in commercial fishing nets.
Dietary Changes Based on Size and Habitat
The dogfish diet changes significantly throughout their life cycle, a phenomenon known as an ontogenetic shift. Juvenile dogfish initially rely on smaller, softer prey, such as small crustaceans, worms, and euphausiids. As they increase in size, they transition to a diet dominated by larger, more energy-dense prey, primarily teleost fish and cephalopods. Geographical location and habitat also introduce significant variations in the diet. Dogfish in the North Atlantic may rely heavily on species like Atlantic menhaden, while Pacific Spiny Dogfish consume more walleye pollock and Pacific herring. Deep-sea dwelling dogfish species often focus on benthic organisms and deep-water squid unavailable to their coastal relatives.
Place in the Marine Food Chain
The dogfish occupies the role of a mesopredator, a mid-level predator that both consumes smaller organisms and is preyed upon by larger ones. They serve a significant ecological function by controlling the populations of numerous forage fish and invertebrates, helping to regulate species like herring and mackerel. Despite their defensive spines, dogfish are a food source for several larger marine animals. Their natural predators include larger sharks, seals, orcas, and some large finfish like cod and goosefish. Their abundance means they transfer substantial energy from smaller prey items up to these larger consumers. Their feeding habits place them in direct competition with commercial fisheries for species like herring and squid, leading fishermen to often view them as a nuisance. Conversely, the dogfish is also a target species itself in international markets for human consumption.