Researchers tip the scales on anadromous wild Atlantic salmon. That is, they place them on microscope slides to better understand why the population of this endangered species continues to decline even though their harvest – commercial or recreational – has been banned for decades.
Let me clarify a few points up front to avoid confusing fishermen or confusing eaters. First, the landlocked salmon, a freshwater relative in the Salmo salar Family, hailing from a handful of Maine lakes and stocked in many other lakes, rivers, and streams statewide, is still fair (and legal) play for recreational anglers. Second, the Atlantic salmon from Maine on your plate – and the one-pound piece of tenderloin on my cutting board – almost certainly comes from a farm run by Canadian company Cooke Aquaculture Inc., where it was. Bred to market size (around 11 pounds) in net pens at Machias Bay.
And, finally, Dr. Kathy Mills, who heads the Integrated Systems Ecology Lab at the Gulf of Maine Research Institute, and her team do not address the environmental issues surrounding salmon farming in Maine or comment on them. legislative efforts to regulate this industry at that time.
They are simply examining heaps of information about physical fish scales extracted from marine salmon as they returned to rivers in Maine to spawn over time. Since salmon are anadromous fish, they spend the first part of their life in rivers, move through the ocean for one to three years to mature, and then return to their native rivers to spawn. The steady decline in populations in several rivers in Maine indicates that something is happening during the salmon’s time at sea that is making their survival more difficult.
Fishermen and researchers have a long history of collecting scales from wild salmon, noting when and where they were collected. Using a high-powered microscope, researchers can now see the mineralized ridges, or circuli, that salmon deposit on their scales as they grow. The photos I have seen of these enlarged scales look like a cross section of a crossed tree trunk with a thumb print. Unlike trees which produce one ring of growth per year, fish scales seem to register several circuli per year of life. An international group of researchers comprising members of the Maine Department of Marine Resources, NOAA-Fisheries in the United States and the Department of Fisheries and Oceans Canada, archived the images of scales collected over time and organized the information about them in databases.
Mills’ team analyzes this data. She says the distance between circles on a scale (measured accurately by computers) can tell a lot about a particular fish. When the rings are farther apart, it means the salmon has experienced a period of rapid growth. These data points can help reveal how long a particular salmon spent at sea, how long it took to mature, and how much it grew relative to other members of its cohort when it returned to its native river for spawn.
Mills’ team works to relate growth patterns, information on factors that may influence growth (such as changing environmental conditions, access to nutritious zooplankton and capelin, and migratory patterns) and Atlantic salmon survival rate at sea.
For example, Atlantic salmon prefer ocean temperatures between 4 and 8 degrees Celsius and grow slower at the lower, cooler end of this range. More closely spaced circles then likely formed during the colder winter months or during times of low prey availability. More spaced circles probably correspond to the hot summer months and favorable feeding conditions.
The more we can understand how changes in the marine ecosystem affect the growth of Atlantic salmon, the more likely it is that scientists will be able to identify barriers to a return of wild Atlantic salmon and identify conservation efforts and management requirements to further protect the species.
Mills says his team works closely with NOAA’s Northeast Fisheries Science Center and that researchers participate in several international Atlantic salmon-focused science and management organizations that are developing science advice for the management of wild Atlantic salmon. , then pass regulations based on that advice.
“Our research indicates that changing the marine ecosystem is a powerful driver of declining Atlantic salmon populations,” said Mills. There are few steps international regulators can take to control ecosystem changes other than continuing to control marine salmon fishing, but local and state regulators can work to reduce the number of dams salmon must pass through and improve habitat conditions in rivers to maximize the number of healthy wild juveniles swimming towards the sea.
“Our results can also help management agencies at all scales (national and international) by providing expectations for salmon productivity in the future,” said Mills. Just to level expectations, while she would love to see a viable wild Atlantic salmon fishery return to Maine, she is not optimistic that this will happen. “Ocean conditions have changed dramatically unfavorably to Atlantic salmon, and climate projections indicate that these changes will continue into the future. “
Given these projections, Maine salmon enthusiasts can choose farmed salmon, steal wild Pacific salmon caught in Alaska, or use adaptable seafood recipes that can use the species local fishermen are looking for.
SEAFOOD RAGOT WITH CURRY AND SWEET POTATO
This recipe adapts to available seafood, seasonal vegetables and the degree of spicy you want to make. For the rendering photographed, I had salmon and scallops in the freezer, I chose sweet potatoes for the substance and red peppers, green beans and purple carrots for the color, and I ran with Thai yellow curry paste, the mildest alternative to Thai red and green curry paste.
For 4-6 people
1 small bunch of cilantro (15-20 stems)
2 tablespoons of vegetable oil
1 onion, peeled and finely chopped
1 tablespoon of chopped fresh ginger
1 teaspoon of chopped garlic
2 tablespoons of yellow curry paste
1 large sweet potato, washed and cut into ½ inch cubes
1 can of 14 ounces of coconut milk
3 cups of fish or vegetable broth
1 tablespoon of brown sugar
1 sweet red pepper, cut into 1-inch pieces
½ pound fresh green beans, trimmed and cut into 1-inch pieces
2 carrots, peeled and sliced
1 1/2 pounds of fish or shellfish of your choice, cut into large chunks
1 serrano pepper, sliced
White rice or soba noodles, for serving
Remove the cilantro leaves from their stems. Tie the stems with a piece of kitchen twine. Finely chop the leaves. Set them both aside.
Heat the oil in a large, heavy-bottomed saucepan over low heat. Add onion and cook until softened, about 5 minutes. Add the ginger and garlic and cook for 1 minute. Stir in the curry paste and cook for 1 minute. Add the sweet potatoes and mix well. Add coconut milk, broth or water, brown sugar and tied cilantro sprigs. Bring the curry to a boil and cook for 8 minutes until the sauce thickens and the sweet potato pieces are almost tender. Remove the coriander stems and compost them. In the pot, add the carrots, green beans and red pepper. Bring the curry back to a boil. Carefully place the fish pieces in the curry, making sure they are covered with the sauce. Cover the pot, turn off the heat and let the residual heat of the curry sauce gently cook the seafood until opaque, 4-5 minutes. Combine the zest and juice of a lime and the chopped cilantro. Add sliced serrano chili to taste. Serve with rice or noodles and lime wedges.
Christine Burns Rudalevige is a food writer, recipe developer, tester and cookery teacher in Brunswick, and the author of “Green Plate Special”, an Islandport Press cookbook based on these columns. She can be contacted at: [email protected]
Sweet and sour reduced apple cider syrup enhances many fall dishes, including apple pancakes