New Dynamics Churn Ocean Norms

by Laurie Schreiber

ROCKPORT – The ocean ecosystem is changing in ways that make it difficult not only to manage fisheries, but even to understand all of the many factors that may be affecting the sea’s dynamic denizens.

A seminar at last month’s Maine Fishermen’s Forum, called “Our Changing Ocean: What Factors May Be Inhibiting Groundfish Recovery?” noted that, despite two decades of extraordinary restrictions on fishing effort, many groundfish stocks in the Northeast have failed to respond. Factors under scrutiny include increased water temperature and inflated populations of lobster, dogfish, and seals.

“Every one of us, in some way or another, is observing these changes in the ecosystem,” said Dr. William Karp, director of the Northeast Fisheries Science Center in Woods Hole, Mass. He said the dynamics of fish stocks and the way stocks interact appear to play an important role in recovery.

Dr. Michael Fogarty, a scientist with the Woods Hole, Mass-based Northeast Fisheries Science Center’s ecosystem assessment program, said that major climate changes have broad ramifications in the Gulf of Maine and, indeed, around the world.

“Most scientists around the world have come to the understand that the change to climate is due to human activity, in particular the amount of carbon dioxide we put into the atmosphere and its effects both on land and sea,” Fogarty said.

 

Fogarty said temperature is only one part of the story. Other changes are in precipitation, wind speed and direction, and many more indicators, and these have important implications for the area’s oceanography and productivity of the system, he said.

One example of change is melting sea ice that flows from the Arctic to the Gulf of Maine, a process that can take just 18 months. Ice melt brings colder, fresher water to the gulf and lowers its nutrient content and salinity, he said. In turn, changes can be seen in the productivity of the food web, beginning with microscopic organisms.

Some changes that have been observed in the Gulf of Maine’s two “iconic” species, lobster and cod, are connected to changes in temperature patterns and overall distribution patterns, he said.

For example, he said, trawl surveys show the major distribution of offshore lobster stocks have shifted from the Southern New England and Mid-Atlantic area progressively northward, and is now heavily concentrated along the Canadian border.

Cod has also shifted north and eastward, he said

“That has a lot of implications to people who are fishing,” Fogarty said. “It points to the need for us to take into account the environmental changes we’re seeing. This is not a blame game. You have an interaction between fishing and with parts of the system that are changing, and we need to take them both into account to understand what the best strategy would be. We can expect lower yields and we have to have lower fishing pressure.”

Stock interactions may also play a role in the status of groundfish. Dr. Graham Sherwood, a research scientist with the Portland-based Gulf of Maine Research Institute, reported on the long lag in the recovery of codfish stock in Newfoundland. That stock collapsed in the early 1990s, from well over 1 million metric tons (mt) to 10,000 mt, a 99 percent decline.

A fishing moratorium was declared in 1992. Models predicted recovery in a short timeframe. But only now is the area beginning to see a slight recovery, Sherwood said.

“What’s to blame for this long recovery?” Sherwood said. “Seals always come up in Newfoundland. It’s a hot-button issue.”

However, he said, studies show that Newfoundland’s large population of harp seals, although they consume cod and other groundfish, as well as other forage and crustaceans, have always co-existed at high levels with cod.

“So seals may slow the recovery of cod, but don’t necessarily preclude cod recovery,” Sherwood said.

Bycatch of cod in other fisheries has been an issue.

But the lack of forage fish stands out. “There’s general feeling among scientists that cod will eat anything they can get their mouths on, and so it shouldn’t matter what happens to their prey base,” Sherwood said.

However, he said, studies have shown that capelin – a small fish in the smelt family – are the best forage for migrant cod. When capelin were abundant, cod were packing on lots of lipid energy, which is important for migration and overwintering and for maturing gonads.

“Resident” cod – which don’t migrate – don’t spawn as much, he said.

“So now we know capelin are important, and we see recovery starting to happen, so the question is, Are capelin coming back?” Sherwood said. The first indications are — yes. There have been some observations of capelin spawning on the area’s beaches, a sight that has not been seen in a generation, Sherwood said.

Offshore trawl and acoustic surveys also show something of an uptick in capelin biomass, although their population is nothing like it once was. Likewise, in the Gulf of Maine, there is some thought that the decline of river herring may have inhibited the recovery of cod, Sherwood said.

Other speakers said that gray seals and dogfish may also be negative factors in groundfish recovery. Betty Lentell, a biologist and consultant with the Chatham, Mass.-based Cape Cod Commercial Hook Fishermen’s Association, said that increasing numbers of gray seals have impeded spawning and schooling behavior, impacted water quality, and impacted fishing in her area.

Captain Michael Russo, born and raised on Cape Cod and a groundfisherman for 25 years, said an abundance of dogfish in his area has decimated spawning grounds and groundfish populations in recovery. “I’m living this nightmare,” Russo said. “All right, I’ve sucked it up. I’ve taken the hard quotas on groundfish, I’ve done the dance. And I’m going to forsake 30 years of fishing, for dogs and seals? Give me a break. But that’s the level of frustration. Seals ruin the trap fishery. We’re running from seals and getting whaled on by dogs.”

Karp said the issues deserve careful attention, not only to try to find solutions but also to avoid a possible solution’s unintended consequences. For example, he said, “If the abundance of dogfish were to be greatly reduced, what would the consequences be of that? Would that reverse the decline of the cod population? I think those kinds of questions might help the discussion to move forward.”