The Beachcomber May 27, 2016

Our Local Sharks Prefer Seafood

May 27, 2016
Photo by: NOAA Spiny dogfish (Squalus acanthias)

There are plenty of sharks living in the waters around Long Beach Island: in the bays, lagoons and even the surf. But except for the famous 1916 attacks off Beach Haven and in the Manasquan River, no other mortal shark attacks have been recorded in New Jersey.

That’s not so surprising since our most common species of shark are not considered man-eaters or even man-tasters, only interested in eating seafood.

Rutgers University’s Institute of Marine and Coastal Science’s most eminent ichthyologist, Ken Able, Ph.D., is the long-time director of the Rutgers Marine Field Station, located at the end of Great Bay Boulevard in Little Egg Harbor. Able and his graduate students have been tallying the number and types of fishes in the waters off Great Bay and Little Egg Harbor since 1989. This is done in a variety of ways: by plankton net off a bridge at night during times of flood tides; by nets, weirs, throw traps and trawls; and, most recently, by acoustic video from kayaks.

In his book about the Rutgers Marine Field station, From Lifesaving to Marine Research: Station 119, published in 2015 by Down The Shore Publishers, Able notes that despite all the sampling and research into the fish of the Mullica River basin and Little Egg Harbor (and, by extrapolation, Barnegat Bay), there are still gaps in the life histories of even the more commercially important fishes. He writes: “The ongoing studies of fish in estuarine habitats clearly show that use is highly seasonal, with most species abundant from spring to fall and particularly in the summer. Much of the abundance at the warmest temperatures is due to reproduction in the estuary or the movement of larvae and juveniles into the estuary after spawning in the ocean.”

Able recounts that records and specific studies of the Mullica, Bass and Wading rivers, Great Bay and Little Egg Inlet since the 1970s have documented about seven shark species. Our most abundant shark, the smooth dogfish, is a migratory fish. “The best information available on shark migrations is that for smooth dogfish, which are known to over-winter off North Carolina and to the south,” wrote Able for his next, yet-to-be-published book, used here by permission. “A Rutgers Institute of Marine and Coastal sciences graduate student, Rodney Rountree, tagged about 200 pups and had two tags returned. These were recaptured together in the same net the following March off North Carolina, by a commercial fisherman.

“These large-scale seasonal movements are complemented by smaller-scale movements by the sharks when they are in southern New Jersey.

“From our extensive collections with weirs, seines, gill nets, trawls, and by hook and line, we know that adult smooth dogfish ‘pup’ (bear live young) in the Great Bay/Little Egg Harbor area from May to July and then leave the estuary. The pups are born live in litters of 3 to 18, are 11-15 inches at birth and reach 22-27 inches by October. The smallest pups spend most of their time in marsh creeks during this time. Eventually, pups leave for deeper water as they grow and by October they leave the estuary.

“In the warm waters of summer and autumn, they are most abundant in creeks during nighttime flood tides. Their occurrence can also be influenced by short-term environmental factors such as temperature. In the summer of 1988 there were numerous upwelling events that resulted in very cold water moving into Great Bay. In a trawl survey at that time, we caught numerous adult smooth dogfish in a small 16’ trawl. In the subsequent 28 years of similar sampling, few were found.

“That same year, we tagged ten adult smooth dogfish (36-44 inches) with acoustic tags that allowed us to track them for up to 90 days, with a sonar system that functioned like an underwater E-Z pass.  As a result, we learned that they preferred the lower portions of Great Bay and Little Egg Harbor near Little Egg Inlet, an area with the highest salinity. However, one individual moved upstream and into the Mullica River as far up as the Garden State Parkway Bridge.”

According to the Florida Museum of Natural History website, the smooth dogfish usually grows to 3 or 4 feet in length and is the most abundant shark on the East Coast. It’s called the dogfish because it has a habit of fishing in packs; however these small sharks have flat, blunt teeth, more suitable for crunching and grinding the prey they go after: shellfish and crabs.

Able can attest to their docile nature as he was once startled by one as it bumped the floating dock he was standing on one night as he peered into the gloom. Later he found they frequented the station’s lighted boat dock. One night a graduate student caught one of them just using his hands, and they put it on the grill for dinner – not all that tasty, Able reports. Another time he held a small, live dogfish in one hand while driving to the field station in order to give it to a visiting scientist.

Smooth dogfish seem to be harmless creatures though numerous – as anyone surf casting off LBI can attest.

But our area is also host to the sandbar shark and the dusky shark.

The sandbar shark, also known as the brown shark or thick skin shark, is shaped like a fearsome shark. It can grow up to 8 feet long, and has a very large dorsal fin – one that would grab attention if seen slicing through the water off any beach if the shark ever came to the surface. Luckily it seldom does; it prefers to coast along the muddy or sandy bottom looking for its favorite prey: fish and crabs.

It is the most common shark in the Chesapeake Bay to our south but also frequents our lagoons, harbors, bays and the mouths of rivers. According to the International Shark Attack site, which keeps records since the 1970s, it has rarely been associated with attacks on humans.

“The sandbar shark also occurs commonly in Great Bay,” said Able. “The adults are off North Carolina and south to the Caribbean in the winter, then migrate back along the east coast to Great Bay where detailed studies have indicated that they pup. Great Bay is the northernmost area of their range on the east coast.  We captured pups that averaged 19-24 inches, with umbilical scars, indicating that they were born in the summer.”

According to the National Geographic website, torpedo-shaped dusky sharks are long-distance swimmers; some migrate up to 2,000 nautical miles. Yet they return to the same geographic region where they were born to give birth. Though fearsome looking, they have more to fear from us.  Distinct regional populations mean they are more susceptible to overfishing. In 2000, the United States banned both recreational and commercial fishing for the dusky, but they are overfished elsewhere for the shark fin trade.

These sharks are long-lived and don’t reproduce until they’re 22 years old. Females gestate for 22 months so can give birth only once every three years, adding to the need to protect them.

Able has included rays in his account of local sharks because they have become so numerous in our area.

“The cownose ray is worth noting because when they are at the surface, something they often do, their fin tips extend out of the water and look like shark fins. The only common skate is the clearnose skate. These are not residents; the cownose ray migrates into our waters from the south and the clearnose migrates inshore during the summer and outshore during the winter.

Other species of sharks and their relatives that can stray into the Mullica/Great Bay/Little Egg area include the spiny dogfish; during the last winter, several pups were captured just inside Little Egg Inlet. The tiger shark and hammerhead have also been recorded. In the summer of 1998, a youngster captured a juvenile smooth hammerhead in the inlet. The southern stingray, the bullnose ray and the little skate have also been collected by Rutgers.

“Other possible records have been more unusual.  By one story, a blue shark, typically an oceanic species, was caught on hook and line in the vicinity of the former menhaden plant (fish factory) on Crab Island in Great Bay, when the plant was processing fish meal and attracting lots of sharks in the process,” said Able.

Bull sharks of various lengths have been reported in the Mullica River at Lower Bank, but there are no known photographs to confirm these identifications, he notes. The occurrence may be uncertain because other species of sharks are much more abundant.

“Time will tell if the sharks and their relatives become more abundant, as we continue to study these fascinating fishes,” said Able.

It’s comforting to know for those of us who swim, surf and otherwise frolic in the water that no shark attacks were reported last year in New Jersey, and from 1837 to the present there have been just 15 confirmed, unprovoked shark attacks in the state.

For more shark facts and attacks, check out the International Shark Attack File maintained by the Florida Museum of Natural History.

— Pat Johnson


Close-up of the head, Spiny dogfish (Photo by: NOAA)
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