New Jersey Scuba Diving
Sharks - Dogfishes
"Dogfish" is a generic name for a large number of small, generally harmless and unaggressive sharks, not all of which are very closely related. Smooth Dogfishes are related to Tiger, Bull, and other Requiem Sharks, while Spiny Dogfishes are in a completely different group, more closely related to Angel Sharks. Compare these with the unrelated Chain Dogfish, a "Cat" shark. Sandbar sharks have nothing in common with the others here, except their small size. None of these little sharks is really dangerous, although any of them could give a good bite if provoked. Generally, they will avoid you.
Most of these sharks are in more danger from us than we are
from them. Real sharks are ashamed of them.
to 3ft (male)
to 4 ft (female)
cool coastal waters, midwater and bottom, but seldom at the surface
The Spiny Dogfish has two distinguishing features: rows of small white dots that run along its sides, and a sharp spine that is found in front of each of its two dorsal fins. The spines of the Spiny Dogfish are formed from material much like that of our teeth. Other distinguishing features include the lack of an anal fin, and the rounded, un-notched tail, unlike the Smooth Dogfish. In the water, the white spots are the thing most likely to jump out at you for identification, although they fade away in some older individuals.
This is thought to be the world's most abundant shark, occurring worldwide in temperate and sub-arctic ocean waters. They prefer cooler water temperatures, from a low of around 45-46 F to a high of 54-59 F, and occur in oceans and coastal zones but rarely enter the upper reaches of estuaries and never occur in fresh water. Spiny Dogfish are gregarious in nature, often occurring in 'packs' of hundreds or even thousands of individuals, and may be found anywhere in the water column, from the bottom to the surface.
Spiny Dogfish are voracious predators that feed primarily on bony fishes. Principal food are members of the herring family, sand lances, smelts and euphasids ( a krill-like ocean shrimp. ) Twenty-seven other fish species, many being of commercial importance fall prey to the Spiny Dogfish, as do over 13 species of invertebrates including squid, lobster, and crabs. "Spurdogs" are not picky, and will feed on almost anything that is plentiful, even Comb Jellies. In Europe, they are often served as "Fish & Chips", but in North America they are generally considered nuisance / trash fish, although sometimes marketed commercially as "Cape Shark". They are preyed upon by larger sharks, and are not above eating each-other.
This long-lived species is the most studied of all the sharks, no doubt due in part to their use as a dissection subject in the classroom. Some researchers have estimated the life expectancy of this shark to be from 25 to as much as 100 years. Females of the species mature in about 10 years at length of 27-40" and males mature in 11 years at a size of 24-28". Females are ovoviviparous ( produce eggs that hatch within the body ) and have a gestation period of 22-24 months, the longest of any vertebrate. They generally have from 2-15 pups with an average of about 6-7 with each being 9-12" in length. With such a long lifespan and low reproductive rate, this shark is particularly vulnerable to overfishing.
Spiny Dogfish seem to be attracted to yellow - any yellow object, such as a bag or tank, will provoke their curiosity. Lone individuals are shy, but these little sharks become bolder in groups, and a pack may take turns making passes at you, which soon goes from amusing to annoying. If one comes closer than you would like, a swat on the nose is usually enough discouragement. The teeth are sharp, but too small to do much damage, and the Spiny Dogfish is more likely to just bump you than actually bite. Of more concern are the two mildly poisonous spines on the back, with which the shark will lash out to defend itself if necessary. They are graceful sinuous swimmers - fast and agile.
Spiny Dogfish are speedy little buggers, not easily photographed. Generally, they are gone before you can even point the camera at them.
The dorsal spine is clearly evident in this shot
This is probably the most dangerous shark you will ever encounter while diving in New Jersey. Try not to scare it away.
to 4ft (male)
to 5 ft (female)
shallow coastal waters, in depths 30 ft and below.
Smooth Dogfish are tannish-gray, slate-gray, or brown above. The lower sides and belly are white, grayish-white, or yellow. A sooty spot is often found near the tip of the upper lobe of the caudal fin. The species is distributed from New Brunswick, Canada, to Uruguay, and inhabits the bottoms of estuaries and coastal waters out to a depth of about 650 feet. During the spring and summer, most of the sharks are found in waters less than 60 feet deep.
The Smooth Dogfish Mustelus canis is one of the most common sharks along the Atlantic coast of the United States. The small gray-brown shark discarded on a pier or beach in the spring of the year is probably a Smooth Dogfish or "Smoothhound". It is a medium-sized shark reaching a maximum length of about 5 feet, although fish in the 1- to 3-foot class are more common. The species has a slender body with two dorsal fins nearly equal in size. The second dorsal fin is positioned slightly ahead of the anal fin. Other distinguishing characteristics are the narrow, catlike eyes, the large spiracle behind each eye, and the caudal fin, which has a small lower lobe.
Spawning occurs in coastal waters from May through July over most of the range. Males are sexually mature when they are 1 to 2 years old, females when they are 2 or 3. Fertilization is internal, and after a 10-month period, the female births 4 to 20 ( average 14 or 15 ) 14-inch pups. The sexes grow at different rates. Females are larger at a given age than males, and attain a larger maximum size ( 59 inches compared to 43. ) Average lengths for the sexes combined for ages 1, 5, 10, and 15 years are 16.9, 43.9, 50, and 52 inches. Smooth Dogfish use their senses of sight and smell to scavenge for prey, usually during the hours of darkness. Favorite foods are crabs, fishes, squids, clams, worms, and lobsters.
Smooth Dogfish jaws, showing tiny rounded teeth designed for crushing shellfish.
Unlike the Spiny Dogfish, which can be comically aggressive at times, the Smooth Dogfish is almost certain to flee from a diver, unlike its big cousins, Tiger and Bull sharks.
Atlantic Angel Shark
Size: to 5 ft
Habitat: shallow coastal waters to extreme depths
Angel Sharks are ambush predators, much like Goosefish. They are generally passive creatures, but can bite viciously if provoked. They seem to be intermediate between sharks and rays, and are actually more closely related to Spiny Dogfish than anything else, despite appearances.
open ocean bottoms, deep
This is a harmless little Cat shark that is found on deep wrecks beyond 130 ft.
Sandbar (Brown) Shark
to 6 ft
The Sandbar Shark is the commonest inshore shark in New Jersey waters. It
Most people are familiar with Peter Benchley's thrilling novel Jaws or one of the movies it has inspired. The image of a giant shark terrorizing a small resort community is hard to forget. After all, the idea of predators ( in this case, people ) becoming prey realizes one of our most primal fears. It also makes for exciting reading or viewing.
Fortunately, actual shark attacks are rare. In fact, few species of shark are considered dangerous to man and the poor reputation sharks have earned throughout much of history is horn more out of fear and ignorance than scientific fact. New Jersey's coastal waters harbor a rich diversity of marine life. Included in this diversity are several species of shark, one of which is the Sandbar Shark.
The Sandbar Shark ( Carcharinus plurnbeus ) - also commonly known as the Brown Shark - is a small-to-medium-sized shark found in temperate and tropical waters worldwide. It is a heavy bodied shark with a large dorsal fin, the vertical height of which exceeds 10 percent of its total body length. Its coloration is dark gray to brown above, becoming almost whitish below. Length at birth is approximately 25 inches, while mature adults average six feet. In New Jersey, a similar shark, the dusky, may be confused with the sandbar shark. But the dusky has a smaller dorsal fin and is significantly larger at maturity.
Sandbar sharks adapt readily to captivity.
Estuaries, bays and coastal areas are the preferred habitats of the sandbar shark, which is the most commonly seen toothed shark in our coastal bays. The sharks are bottom dwellers found predominately at depths of 10 to 30 fathoms, but occasionally at depths of more than 100 fathoms. Because they are bottom dwellers and stay away from beaches, the sandbar shark has rarely - if ever - been implicated in an attack on a human.
Sandbar sharks are highly migratory, ranging in North America from New England to Florida and the Gulf of Mexico. In New Jersey, the sharks occur in highest concentrations during the summer months when they migrate north to their primary nursery grounds. Recently, one tagged specimen was recovered and found to have traveled 2,019 miles from Point Judith, Rhode Island, to Mexico. This is the third longest migration reported for a sandbar shark.
Like many predators, sandbar sharks are opportunistic feeders. Their diet is varied, consisting mainly of small fish, crustaceans, mollusks and, in some places, octopuses. While sandbar sharks have large mouths, their teeth are relatively small and this makes it unlikely that they can attack anything larger than the prey on which they feed.
The abundance of sandbar sharks is testimony to their reproductive success. The sharks mate in spring and early summer. After a gestation period of nine to 12 months, pregnant females move to nursery grounds in shallow waters close to shore and give birth to an average of nine pups ( anywhere from one to 14 pups is possible. ) the newborn sharks resemble scaled-down versions of the adults and are on their own to fend for themselves as soon as they are born. At this young age, the sharks' mortality rates are high as larger predators such as tiger and bull sharks feed upon them. The young sharks will stay in shallow waters until cooler temperatures set in. They then move to deeper waters, possibly forming schools.
Sandbar sharks are popular sportfish, and are also harvested commercially in places.
Because sandbar sharks are born alive and are large at birth, their survival rates are high - much greater than that of egg laying fishes. In fact, a large fishing industry has developed for them and they are considered one of the most economically important species on the East Coast. Though it is not currently heavily fished in New Jersey, elsewhere both recreational and commercial anglers seek out the shark's palatable meat. In fact, it is reported to be the most abundant commercially valuable shark taken off the southeastern coast of Florida.
Despite their high survival rates, sandbar shark populations are still susceptible to over fishing. This results from the fact that they grow very slowly ( only about two inches a year, ) mature at an old age and bear relatively few young. In fact, sandbar sharks were recently included along with 21 other species of large coastal sharks - in a new management effort by the National Marine Fisheries Service that for the first time sets commercial quotas and sportfishing bag limits for sharks.
If we are conscious of our actions and sensible in our management, the sandbar shark will always be a part of New Jersey's natural heritage. As both predator and prey, the shark fills a critical niche in the marine ecosystem and in the lives of those who depend on it for their livelihoods. And, unlike the situation portrayed in Jaws, this species - and the overwhelming majority of sharks - has much more to fear from humans than the other way around.
Al Ivany is a naturalist and media specialist with the Division of Fish, Game and Wildlife's Pequest Natural Resource Education Center in Oxford
This article first appeared in New Jersey Outdoors - Summer 1993
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