Gray seals are making a huge comeback
For nearly a century, gray seals in New England had a reward over their heads. Maine and Massachusetts have paid to kill people because they have run out of fish stocks. They have also been hunted for their flesh and their skins. In 1973, a year after the Law on the Protection of Marine Mammals Prohibited to Systematically Kill Animals, a census estimated that there were only 30 gray seals on the coast of Maine.
Since then, the gray seal of Canada has returned to collect on the east coast of the United States. Its populations are growing at Martha’s Vineyard, Nantucket and Cape Cod, but scientists have had difficulty estimating their real numbers. The count when they are on the beach can be difficult and expensive, and these surveys will miss the seals in the water.
Now, in a study published in Bioscience, researchers combined Google Earth images and data from tagged seals to make a more accurate estimate of population. His conclusion: there may be many more gray seals that live along the east coast as previously thought.
“Previous surveys based on traditional counting methods … have counted about 15,000 seals on the southeastern coast of Massachusetts,” said David Johnston, an ecologist at Marine Conservation at Duke University, in a statement. “Our aerial reconnaissance with the help of technology, which uses Google Earth images in conjunction with tagged animal telemetry data, suggests that the numbers are much higher, between 30,000 and 50,000.”
Johnston and his colleagues used high resolution images of Google Earth to count the number of seals on the beaches for several years. They also analyzed more than 8000 hours of follow-up data tagged together to try to determine how many would be in the water at one point, in which the upper limit of their estimate.
With very high resolution images from numerous commercial satellites, the authors claim that this can provide an economical alternative to old methods of estimating population size, especially when the image is associated with tagging data.
Traditionally, scientists would capture some animals would mark them and see how these animals can be tagged found to extrapolate the size of the entire population later. Or they will face a plane or helicopter flight for air accounts. However, this study uses the marking data only eight seals to estimate the time that the average seaborne sea-to-Earth spend.
Not everyone is happy with the explosion of the Pinniped population, especially the fishermen, who see them as competition for fishery resources. In recent years, some groups have advocated reducing the number of gray seals. Johnston said that it would not only be illegal, but would also be premature.
“We know almost nothing about what gray seals eat, how and where they eat, and they interact in a green way for fishing,” he said. “There is very little evidence that seal tightness increases fishing yields or produces positive effects on the local ecosystem.”
“The really good thing here,” Johnston said, “is that the recovery of gray seals is a success for conservation.” This tells us that if we stop doing bad things for marine species, we can recover. People realize, we invest in conservation, we can do the work. “