Current and Alternative Boston Traffic Separation Scheme (TSS) and associated right whale sightings, March-July 1960-2003. Figure from Wiley, D., M. Thompson and R. Merrick. 2005. An analysis to reduce ship strike risk to baleen whales in the Stellwagen Bank National Marine Sanctuary. Report to the Stellwagen Bank National Marine Sanctuary. 175 Edward Foster Road, Scituate, MA. Click image (above) for enlarged view.

Northern right whales underway off New England in May, 2002. Photo by NEFSC aerial survey team, MMPA permit 775-1600-02.

Richard Merrick of the NEFSC explains his findings at the Marine Mammal Commission review panel (see related story.) Photo by J. Hain, Associated Scientists at Woods Hole

“For marine mammals the pattern seems to be that if you remove human-caused stresses and then wait, you will get recovery. First the populations have to work through whatever problems have likely been caused by humans.” From the left: Southern fur seal, photo by Richard Behn NOAA Corps; gray whale breaching, photo by Dave Withrow NOAA/NMFS/NMML; and elephant seal pups, photo by Rolf Ream, NOAA/NMFS/NMML

Merrick gave three examples of species that fit the pattern. The Eastern Pacific gray whale population was down to a couple of hundred animals before hunting was stopped. After the hunting ban, the population didn’t immediately start growing. “Then some fortuitous combination of events got them started and they just chugged along,” said Merrick. Today the group is no longer listed as either threatened or endangered. Two other examples are elephant seals and southern fur seals -- which were hunted to what people thought was extinction. Both populations have recovered, but it took time.    Northern right whales are an example of a species that hasn’t yet turned that corner. In general, Merrick is optimistic about the chances of recovering these whales, which are among the nation’s most endangered wildlife species. He cautions however, that it will be a long haul.    “We stopped hunting them but there’s been no recovery during the past century,” Merrick observed. “This historical lack of recovery is perhaps not caused by collisions or entanglement, but removing those threats -- and the resulting loss of animals -- can only improve recovery chances.”

Richard Merrick, chief of the NEFSC Protected Species Branch, has shown that moving a portion of the Boston ship traffic lanes slightly to the north could reduce by half or more the relative risk of collisions between ships using the lanes and large whales.

“This study looked not only at separating whales from ships, but also at whether there should be changes to where and when fishing gear modifications are currently required to reduce the risks to these animals,” said Merrick.

The endangered Northern right whale is particularly susceptible to ship collisions. All six species of endangered whales that occur off the Northeast are known to be injured or killed by both ship collisions and encounters with some kinds of fishing gear.

NOAA Fisheries Service has identified large areas off the Northeast where right whales aggregate during the year. Since the late 1990s, fishing gear modified to make it easier for whales to escape entanglements must be used in these areas. “The strategy relies on seasonal management. To make that work, you need to define in both time and space where whales are,” said Merrick.

Since Merrick’s group began developing a systematic approach for defining these areas, NOAA Fisheries Service has also initiated a national strategy for managing ship traffic along the east coast to reduce the chances of ship collisions with large whales. Merrick was particularly interested in whether areas for “whale safer” ship operations off New England could be similar, or even the same, as the areas where “whale-safer” fishing gear is required. As it turns out the answer is probably yes.

The basis for this conclusion (as well as the one supporting a shift in the Boston ship traffic separation scheme) relies on a clearer picture of when and where the whales can be expected to aggregate and persist during the year.

Think about it. There are just 300-350 individuals in the population, and they don’t all travel together. Over the year, they range from the Bay of Fundy and the waters southeast of Nova Scotia to the warm southern Atlantic waters off Florida. The task would be almost impossible if the animals didn’t come together in larger groups to take advantage of concentrations of their primary food, and for mating, giving birth, and nursing young.

“The springtime feeding in Cape Cod Bay, the early summer feeding in the Great South Channel, and the summer feeding areas in the Canadian Bay of Fundy have been well-documented for some time,” said Merrick. “But only in recent years have we been able to learn more about whale presence other times of the year, and in places besides these better known ones.”

The big step up in understanding right whale distribution off the Northeastern U.S. has been achieved through NOAA’s expansion of aerial sighting surveys over the entire Gulf of Maine. Merrick’s study used data from more than 10,000 right whale sighting events (an event could include multiple animals) reported between 1960 and 2003. About one quarter of these (2,396) occurred between 1999 and 2003, and were made by NOAA’s aerial survey team.

“The data are much improved since 2000,” said Merrick. “Through our systematic aerial survey, now conducted year-round, we are getting a much better idea of what’s going on offshore, away from the nearshore places where groups are more easily sighted.” For example, prior to 2000 there was little data suggesting that the northern edge of George Bank was an area where there would be animals. “Now we know that they are there,” said Merrick.

The aerial team is watching primarily, but not exclusively, for right whales. “When we see right whales, we break off the survey track and photograph them,” Merrick explained. “Otherwise, the track lines are the same as they would be for any other transect survey. Overall, we are trying to survey the entire Gulf of Maine on a monthly basis.”

Merrick’s results, along with a companion study by colleagues at NOAA’s Stellwagen Bank National Marine Sanctuary, will be considered by the agency as it finalizes proposals for reducing the chances of collisions between ships and whales along the east coast. Merrick’s work also suggests that the boundary between two seasonal management areas should be skewed slightly to the northeast on Georges Bank.

"It is hard for us to know what the real rate of interaction is between gear and animals, or between ships and animals, because the events themselves are relatively rare in comparison to the enormous amount of activity that’s out there,” said Merrick. “So usually we are looking at reducing relative, not absolute risk and this is one example of how we might be able to do that.”

Posted April 26, 2006