Scientists Say Signs That Red Tide Killed Scallops Are Present, But Few

Scientists from Long Island University say that outbreaks of “rust tide” algae this summer may have killed large numbers of bay scallops in Great Peconic Bay but do not appear to have wholly devastated what is expected to be a robust harvest this fall.

Blooms of the red algae, which marine scientists have dubbed rust tide for the brownish-red tint it stains waters where it is blossoming, were widespread in the Peconics this summer—and scientists from LIU said they found large numbers of what they call “cluckers” on the bottom of the bay there.

“They are scallops that are dead but are still attached at the hinge—meaning, they died recently,” said Dr. Stephen Tettlebach, a marine science professor at LIU’s C.W. Post campus. “We saw pretty high numbers of mortality in Great Peconic, but most other areas were fairly consistent from the spring to fall.”

Nonetheless, he said, the number of scallops in Great Peconic is very high, thanks to what he said was one of the largest “sets” of young scallops in decades in 2016.

The rust tide algae has been shown by scientists to be capable of killing fish and shellfish if exposed to a dense bloom for an extended period. The algae has been blamed for a massive die-off of bay scallops during the summer of 2012, when blooms of the algae were especially dense and widespread.

With tracking of rust tide blooms difficult, because they move up and down in the water column during the day and night, Dr. Tettlebach said that pointing to the algae as the cause of the scattered hot spots of mortality witnessed in the surveys is impossible.

Mr. Tettlebach’s researchers have been conducting biannual survey counts of wild scallops at 20 sites around the East End for the last 13 seasons, once in the spring and once in the fall, just before the harvest season opens.

On the whole, Mr. Tettlebach said, the team saw evidence that the population of scallops in the waters between the two forks would be considerably better than last year.

The scientists, however, conduct almost all of their sampling in deep areas of state waters, not in the shallow areas of enclosed harbors or tidal ponds—like Napeague Harbor, Cold Spring Pond or the western shoreline of Shinnecock Bay—that many local recreational scallopers and baymen rely on to tip the scales of whether a given season is good or not.

There may be some promise for town waters—which open in Southampton Town on November 6 and in East Hampton Town on November 12—in the gargantuan set of 2016, which should be of legal harvesting size now.

Dr. Tettlebach said that due to an anomaly of environmental conditions, last year’s young-of-the-year scallops grew quickly in the summer and fall of 2016 and an unusually high percentage of them had reached legal harvestable size by the latter months of the past scallop season, which run until March 31. In town waters, however, pressure is less late in the season, and the leap between robust years and down years are difficult to predict, the scientist noted.

While regulations require that in addition to being at least 2.25 inches at the clasp, harvested scallops must also show a telltale growth ring, which indicates they are more than a year old.

“Last year, there was a lot of harvesting of juvenile scallops that were supposed to be illegal because they had no growth ring, but we saw guys bringing in limits in March, from places where there had not been enough adults in the fall to sustain that,” Dr. Tettlebach said. “That took away from this year’s spawning stock and the adult harvest. It had been one of the largest I’d ever seen—but a lot of those animals are gone.”