Shark trip brings research career full circle

On a warm July morning in 1961, undergraduate Jack Musick of Rutgers University stepped aboard a commercial trawler to begin a summertime study of sharks off the New Jersey coast.

Forty-four years later, VIMS Professor and international shark expert Dr. Jack Musick will bring the R/V Bay Eagle back to the very same waters. His plan is to fish the same stations and gear that he fished in 1961, with the goal of capturing a unique long-term record of changes in shark abundance.

“I’ve wanted to do this for years,” says Musick. He’ll get his wish when the R/V Bay Eagle set sails from VIMS on July 18th for the 10-day cruise.

This photo from Musick’s 1961 trip shows the catch from a four-hour longline set. The set returned a large number of sharks and other fish.Musick says that a direct comparison of shark numbers across a span this long is unprecedented. His 1961 cruise took place 14 years before Jaws sparked the sport fishery that first began to take significant numbers of large sharks from Atlantic waters. The upcoming cruise comes 12 years after federal regulations first sought to manage the commercial fishery that had devastated shark stocks during the 1980s.

Musick’s plan to use the same gear and stations sets his work apart from other recent studies of shark population trends, most notably an analysis in Science by Canadian researcher Ransom Myers. Myers used a technique called “metadata analysis” to conclude that populations of large coastal and oceanic sharks had declined by more than 75% in the past 15 years.

Although Musick agrees with Myers’ general conclusion, he questions his methodology.  Myers’ metadata analysis entails combing through existing scientific and commercial fisheries records to extract relevant data, in this case the number of sharks reported as bycatch.

“Myers compares longline catch rates from the 1950s and 60s with more recent catch rates from observer data in the commercial fishery,” says Musick. “During that time the fishing gear and depths have changed completely. It’s like comparing apples and oranges.”

Today’s longline fishery uses monofilament line and, instead of fishing in the top 100 or 200 feet for swordfish, fishes at 400 or 500 feet for big-eye tuna.

“You just can’t make those comparisons,” says Musick. “There isn’t enough overlap in the gear or target species.”

In Musick’s case, the gear will overlap completely, making for a statistically robust comparison. His crew will use the exact same type of main line, drop lines, hooks (8 and 9 ought), and bait (menhaden) that he used on the initial longline cruises in 1961.

Musick’s Bay Eagle crew, headed by graduate student Jason Romine, will set the same 19 stations between Cape May and Sandy Hook Bay. VIMS graduate students Chip Cotton, Andrij Horodysky, Dave Portnoy, and Vince Saba, along with lab technician Demetria Christo and Captain Durand Ward round out the crew.

Musick’s longline set-up was initially developed for swordfishing. “We didn’t know anything about longlining,” says Musick. “So the gear experts from the Bureau of Commercial Fisheries came and showed [Principal Investigator] Jack Casey what to do.”

Casey and Musick stayed at sea all through that summer, on a commercial trawler donated to the Sandy Hook Marine Lab by a local fishing company. “The Lab Director managed to get the help of the Smith Menhaden Company, which had a local plant on Sandy Hook Bay. Mr. Smith contributed gas, bait, crew, and everything else, for the entire summer of 1961,” says Musick.

Musick will use the same longline gear this summer. “We’ll set a mile and a half of main line, which is a 3/8-inch braided and tarred nylon with anchors and buoys on each end. That line has 100 dropper lines, or gangions, each around 12-feet long. Each gangion has a couple of feet of steel leader that goes to the hook, because a shark will bite through otherwise.”

The only changes he’s made help ensure that setting the line is safer and more efficient. “We now use quick clips to fasten the gangions to the main line,” says Musick. “Back then the clips hadn’t been invented. Instead, you used a slipknot, and you had everything coiled in galvanized tubs. If the lines tangled, and that happened often in rough seas, you just tossed the whole tub over the side. Otherwise you could get tangled in the gear and pulled overboard. You’d then go on to the next set and worry about it when you came back. Because the line is fairly stiff, the tangles would often fall out as it soaked.”

After the upcoming cruise, Musick thinks it will take about a week to get a ballpark figure of the change in shark numbers between 1961 and present. A particularly interesting aspect of the comparison will be that between sandbar and dusky sharks, the two most common species along the New Jersey coast. Sandbar populations have responded well to shark management plans. Duskys have not (see sidebar).

Musick’s graduate student Dan Ha has already digitized the original 1961 data, which until recently had been held at the National Marine Fisheries Service (NMFS) office in Narragansett, Rhode Island. A researcher at the office had found the original hand-written field notes in a tattered box after Musick’s mentor Jack Casey retired from there about eight years ago.

The timing of the upcoming New Jersey cruise is just right, says Musick. “I’ve got [gradate student] Dan Ha doing some pretty sophisticated analyses of our own long-term shark data right now, so I thought it would be a perfect time to go back up there.” Funding agencies agreed. The cruise is funded by NMFS through the National Shark Research Consortium, of which VIMS is a member.