In a past life I seem to remember on Casco Bay, there was a bird the fishermen called shag, and they disliked it. For my part, I remember thinking the shag were kind of cool when they were arrowing in straight lines a few feet above the water in fighter jet formations.

They were less cool when they were swimming because it seemed like they could barely float. The water washed up over the base of their necks, and they held their orange beaks up the way you hold your face when you’re learning to dog paddle. They looked like a low-rider seagull-duck. Seagulls to me were idiots, and duck beauty would not dawn on me for years yet.

I still kind of think gulls are goofballs, but even then I didn’t believe they deserved death. My 11-year-old mind was shocked one sunlit morning in the early 1960s when I was rowing across the cove at Bailey Island and saw a fisherman cruise up in his outboard beside a hapless floating gull and kill it with a bait pick, like a Cossack mowing down a peasant. Feathers went everywhere and the fisherman buzzed away, leaving the gull crumpled on the water.

Even then, the great black-backed and herring gulls common along Maine’s coast were protected by the government. But I guess this did not sit well with some fishermen, who it turned out thought gulls and especially shag — or cormorants, as I later learned to call them — threatened their livelihood by eating too many fish.

Settlers in New England, believing their survival was at stake, set about early on to get rid of double-crested cormorants, and by the early 1800s, the birds had been extirpated from the northeast region. But they have a huge worldwide range, and by the 1920s, they were documented to be nesting again in Maine.

The fishing industry saw them as such a threat that in the 1940s and ’50s, vegetable oil was systematically sprayed on some 188,000 eggs to suppress the population. It didn’t really work. By the mid-1960s, a number of harvestable fish species were noticeably declining in the Gulf of Maine and environs, and the birds took a lot of the blame. “Black water rats,” as one sardonic coastal moniker has it, were shot by the hundreds.

Different species of cormorants live in lake and ocean areas all over the world, and they seem to be reviled almost everywhere except parts of Asia. In 1972, the Migratory Bird Act of 1918, which was the gulls’ protection, was expanded and cormorants, too, came under federal protection. Their numbers increased through the end of the 20th century.

Hereabouts, we see mostly double-breasted cormorants. Much less common are great cormorants, coast dwellers whose breeding populations in Maine have plummeted in recent years for reasons not well understood. The double-crested cormorant has an orange throat pouch, and the great cormorant has a white neck patch.

Whether cormorants have a significant impact on populations of harvestable wild fish has not been established. Most studies seem to indicate they don’t, but the common belief among many fishermen, handed down for centuries, is that they do. Studies in the 1980s showed they were at least interfering with Atlantic salmon restoration projects by eating a lot of hatchery smolts.

As populations increased, federal money made its way Down East-ward in the early 2000s for more studies to figure out how to deter them without having to kill them. Firecrackers, lasers and shooing them away from smolt-run areas seemed to work in one experiment on the Narraguagus River in 2004-05.

All along the coast, as well as lakes, ponds and rivers, shag low-ride the surface and suddenly dive for fish and disappear. Their featherage absorbs water for ballast to stay submerged for as long as two minutes. After a round of fishing, they perch clumsily on a rock outcrop or a buoy and spread their waterlogged wings to dry out.

As a kid, I thought they were cool again when they dove. They stayed down for what seemed like impossible periods of time, popping up feet or yards from where they disappeared. Decades later, they pop into sight again, silent squadrons of two or three angling with Doppler-like precision a few feet over the water.

They vibrate some living thread between here and boyhood. Still fishing, still causing trouble.

Dana Wilde lives in Troy. You can contact him at dwilde.naturalist@gmail.com. His book “Winter: Notes and Numina from the Maine Woods” is available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.