The dogfish sharks hold the record for having the largest estimated population in the world. They are not only populous and common, but gregarious as well – they frequently travel together, in packs of hundreds, sometimes even thousands. That’s where they got their name from, because they hunt in packs.
Being so widespread, dogfish sharks can be found everywhere in the world where there is salt water, even in the Black Sea. What’s more, they can be found even in brackish waters, where salt water meets freshwater in estuaries. They are bottom-dwellers, preferring waters of temperatures between 7 and 15 degrees C (44-60 F) and up to 700 meters deep.
These sharks are about 1 meter long when fully developed and they can be distinguished from other shark species by having two spines at the base of their fins and no anal fin. The spine makes these animals extremely combative – when captured, they can arch their backs and free themselves by attacking their captor with the spines. They also have a venomous gland at the base of these spines – the venom secreted is mild, but sufficiently potent to help the animal get away. Dogfish sharks are dark grey in color, with lighter colored spots and a whitish underbelly.
Dogfish are carnivorous predators – they feed on fish, squids and octopuses and they are known to prey on other sharks as well. Though their feeding routines have not been completely mapped yet, it seems that dogfish sharks have two distinct feeding methods: they either lower their jaw and suck in the food they find or they just snatch the food, cramming it into the mouth.
Dogfish sharks give birth to live young, 2-11 of them at a time. Dogfish have a very long gestation period, 18-24 months long, which is longer than in the case of whales or even elephants. The young are about 20-30 cm long and their growth rate is relatively slow – males reach maturity at the age of 11, while females are not considered mature until they are 19-20 years old. However, at the age of 20, dogfish sharks are still relatively young, their average life expectancy being up to 75 years.
Male and female dogfish sharks make up separate packs and the packs are also diversified based on age. There are packs that consist entirely of pregnant females that are looking for a suitable place to nest in. Dogfish are also known to migrate over long distances. They travel either in pursuit of food or to find waters that are sufficiently cold. In an attempt to identify migration patterns, marine biologists have tagged several dogfish shark individuals and have found that one of them travelled an incredible 6,500 km in a year, but they can only speculate about the reason for such a long journey.