Bluefin Tuna (photo from National Geographic)

Bluefin Tuna (photo from National Geographic)

12/17/2007

Saving the Gulf of Maine

by Karen Rowan

The Gulf of Maine, the expanse of Atlantic Ocean that stretches from Cape Cod to Nova Scotia, was once one of the richest fishing grounds in the world.  Since colonial times, people have over-fished the waters and destroyed the coastline.  But efforts to repair the damage and restore the Gulf are underway, and the lessons scientists learn here may help oceanic and coastal restoration projects in other parts of the world. 

One of the most commercially important species in the gulf is the bluefin tuna. These metallic blue and silvery white fish, which can grow as large as 14 feet and weigh more than 1000 pounds, have suffered tremendous declines. The population in the Western Atlantic is only about one-fifth the 1975 level. The worldwide sushi boom has created a lucrative market for prize bluefins – a single 444-pound fish sold for a record $173,600 in 2001.

Despite the bluefin’s value and well-documented decline, “There is still a great deal we need to learn about bluefin biology,” said Jennifer Goldstein, a researcher at the University of New Hampshire’s Large Pelagics Research Lab. Scientists need to better understand the fish’s growth, reproduction, and migration, in order to effectively restore the population.  Goldstein contributes to the efforts by studying the diet and reproductive habits of bluefins.

In her work, Goldstein uses a novel technique to study the bluefin’s diet.  Past research on the fish’s diet has largely been based on analyzing the stomach contents of fish that have been caught.  But Goldstein’s technique, known as fatty acid signature analysis, looks at an array of fat molecules in a fish’s tissues, and compares the different molecules to the types of fat found in the fish's prey.  From this, scientists can get a better idea of what the fish has eaten over the past several months, not just what happens to be in its stomach at the moment it's killed.  Once the bluefin diet is better understood, scientists will be able to help the population recover.  “Better understanding of their biology leads to better management,” Goldstein said.

Cooperating to help the cod
Another gulf species, the Atlantic cod, began to decline in numbers in 1950s, and by the 1990s, the population had disastrously collapsed, forcing thousands of fisherman out of work.  The collapse spawned a spate of cod restoration efforts, including the largest cod-tagging program ever undertaken in the U.S. 

The Northeast Regional Cod Tagging Program, or NRTCP, is an ambitious effort.  While typical tagging programs target 10,000-20,000 fish, the initial goal of the NRTCP was to tag 100,000 fish.  This program is exceptional not only because of its scope, but also because of the level of cooperation between the agencies involved.  Fishermen’s associations, academic scientists, federal and state officials collaborated and the program reported exceeding it goal, tagging over 114,000 fish.

The tags provide scientists with data on cod migration patterns, growth rates, and the effects of water temperatures and depth on cod movement patterns.  The scientists have made all of the data collected from the tags available to anyone involved, and as data began to pour in, new ideas about managing the cod population began to crop up.  “That’s the nature of bringing that many people together, ideas came out that we could take much further,” said Shelly Tallack, who manages the project at the Gulf of Maine Research Institute. 

Putting a date on the dogfish
When the cod began to disappear, many fisherman switched to catching spiny dogfish.   Not surprisingly, overfishing has now contributed to their decline as well, said Walter Bubley, a University of New Hampshire Sea Grant researcher.  Dogfish are sharks that grow to about three feet long. Although not generally consumed in the U.S., they are standard fare in British fish-and-chips meals and in a German specialty known as ‘belly flap.’ 

Bubley is testing a new way to figure out the age of dogfish sharks – his technique is similar to finding the age of a tree by counting its rings.  As dogfish grow, a banding pattern forms in their bones.  Bubley analyzes those patterns to determine the fish’s age, and he’s found a method that is more precise the older method of determining dogfish age.  (The traditional way is based on looking at the spiny region near the fish’s dorsal fin, and can be off by as many as 15 years.) 

Scientists have to know how old the dogfish are because in order to restore the population, the females must reach maturity and reproduce before they are caught.  Currently, there are no restrictions on catching dogfish, so fisherman can keep any fish they catch including immature or pregnant females.  The special challenge with dogfish is that their pregnancy lasts almost two years, which is among the longest of any known vertebrate animal and hinders the ability of the fish to rebound after a decline.

Bubley’s results could be used to determine at what age these fish mature, which can help create fishing regulations that ensure that females have a chance to reproduce.  And since dogfish are found around the world, Bubley’s approach can be applied to other ecosystems as well. 

Turning the tides
Far from the deep waters where the sharks and tuna live, scientists are also working to restore the coastline of the Gulf, where the young of many fish species find shelter in coastal marshes.  The marshes have a long and storied history of degradation.   Early American colonists filled in marshes to grow hay and during the twentieth century, people working to curb mosquito populations dug out these swampy bogs.  Today, heavily trafficked beaches and boat harbors are often found near marsh sites.

For scientists working to restore coastal wetlands, the typical approach is to first return the land to its original elevation.  But Michele Dione, an investigator at the Wells National Estuarine Research Reserve in Maine, said that a more effective approach is to first restore the natural tidal flow to an area.  She says putting the land back to its original elevation doesn’t guarantee that the tides will come back, because so many other changes to the land have also happened.

For example, a road to a beach might run right through a coastal marsh, cutting off part of the marsh from the ocean, and from normal tides. When many roads such were built, construction workers simply installed narrow drainage pipes beneath the roads.  Dione says that carefully engineered changes that lift the road and install wider drainage pipes beneath it can restore the marsh by allowing the tides to return.

After the tides return, the marshland can be fixed so that water returns to it’s normal depth.  Then, the native plants and animals will return.  “For now, a lot of projects are successful, and we’re getting marsh plants, back,” Dione says.

For centuries, humans have damaged this once-beautiful expanse of coast and ocean.  But the scientists working to improve conditions in the Gulf of Maine and the land along its shores offer optimism that, over time and with enough support, some of the damage may be reversed.