Editor’s Note: Expedition Blue Planet, led by Jacques Cousteau’s granddaughter Alexandra Cousteau, is traveling 14,500 miles of road over 138 days to investigate and film some of North America’s most pressing water-use and management stories. Expedition members will file dispatchs from the field for Scientific American until the expedition concludes on November 12 in Washington, D.C. This is their fifth blog post.

“It means no food for the fish. It’s the bottom of the food chain,” he says over the growling engine of his 45-foot cape island fishing boat, “Rebecca and Shelley.”

Brown is particularly concerned about the herring, which he harvests in weirs, a passive and sustainable traditional fishing structure. “We’re having problems this year with sardines not growing. Their fat content is down to 3.5 to 4 percent fat content and usually this time of year they should be up around 14 percent,” he says.

In his 47 years of fishing, Brown’s seen tremendous changes in the waters that provide his livelihood: “Seems to be more pollution and less sea life.”