One evening when author Paul Greenberg was 10 years old his father dropped him off at Menemsha. That night he would pull six glistening iridescent squeteague from the waters around the jetty.

“I thought I was going to be rich beyond my wildest dreams,” Mr. Greenberg said in an interview at the same spot on Wednesday.

Everett Poole of Poole’s Fish Market sat Mr. Greenberg down and told him he would take the fish off his hands for 65 cents a pound. It was the first fish he ever sold.

Poole’s Fish on Squid Row has since disappeared (replaced by a market of another name). But so have the squeteague — and the squid, for that matter.

Standing on the wave-tossed jetty in a northeast storm, Mr. Greenberg pointed across to the Lobsterville side at what could have been a younger version of himself casting into the channel.

“That kid fishing out there doesn’t know that squeteague used to be in these waters,” he said plaintively.

Mr. Greenberg is on the Island to promote his new book, the New York Times best-selling Four Fish: The Future of the Last Wild Food. In it Mr. Greenberg charts the heedless race in the past 50 years to extirpate a vanishing wild resource and the attendant fish-farming industry that has emerged to satisfy consumer demand.

Mr. Greenberg, an avid sportfisherman, says the fishing on Martha’s Vineyard is still quite good, especially compared with his childhood fishing haunts of Connecticut, but contends that the evidence for fisheries collapse is evident with each reel cast.

“All along this jetty there used to be tons of tinker pollock and you just don’t see any of that anymore. I haven’t seen a blackfish caught off here in years,” he said.

What that suggests to Mr. Greenberg is that stocks have yet to recover from the big groundfish collapses of the 1980s. They may never recover, he said.

With his brother Mr. Greenberg remembers hunting for crabs in the jagged jetty rocks and unexpectedly coming upon five-foot silver eels.

“They were this big around,” he said indicating roughly the circumference of a grapefruit. But he said the monstrous eels, scarcely believable now to a younger generation, were likely another casualty of commercial bycatch.

Still the Menemsha jetty represents a sort of archetype for the fishing bounty of yesteryear.

“Here you can cast your reel and you really don’t know what you’re going to catch,” Mr. Greenberg said. “That’s the fisherman’s fantasy, this cornucopia of every kind of fish. But the species profile here is completely different than when I was a kid.”

At one time or another Mr. Greenberg said he has caught scup, sea bass, stripers, bluefish, bonito, blackfish, tinker pollock, mackerel, squeteague and winter flounder at Menemsha.

Author and longtime Island angler Paul Greenberg off Lobsterville in 2003. — Laura Straus

The last five on that list are virtually extinct in these waters, save a one-off annual run of the once-abundant mackerel (a fish stock that the National Marine Fisheries Service has curiously designated as rebuilt), but the news isn’t all despairing. Striped bass was almost unheard of when Mr. Greenberg fished here as an adolescent. After a moratorium and intensive conservation campaign in the 1980s and 1990s, striped bass stock has recovered from just five million in 1982 to nearly 56 million today.

Although the story of stripers is a cause for optimism, Mr. Greenberg said in order to meet global demand for fish — he writes in his book that annually we take more wild seafood than the weight of the entire human population of China — people need to take seriously the need for sustainable aquaculture. Over the past 50 years fishing stocks have collapsed in the northern hemisphere as commercial trawlers have become more and more destructive and the industry has increasingly sailed south to exploit new resources. As these become overfished, aquaculture inevitably takes their place.

Unfortunately, many aquaculture practices are not sustainable, especially for carnivorous species such as tuna which require protein. Much of that protein comes from smaller, largely unregulated species like menhaden, also harvested for fish oil supplements and agricultural feed. As a result in Chesapeake Bay, a major spawning ground, fishermen and conservationists have observed with alarm in recent years the significant decline of menhaden in their fisheries.

“The last 20 years have all been about preserving the big fish,” said Mr. Greenberg. “The next 20 years will be about reimagining how we deal with the little fish.”

One solution Mr. Greenberg proposes in his book is the farming of those species more suitable to aquaculture, such as the herbivorous tilapia and barramundi, which would not result in net-protein loss and the further depletion of fisheries.

“It is a very key moment for the sea right now because we’re seeing the closing of the circle,” Mr. Greenberg said. “There are no new fishing grounds as commercial fishing has expanded from a northern hemispheric to a global activity.”

One topic Mr. Greenburg said he deliberately avoided in Four Fish was the prospect of ocean acidification and global warming. How these will affect phytoplankton and zooplankton, the primary producers of energy in the ocean, is largely unknown, but early indications are worrisome.

“I intentionally didn’t talk about it because I didn’t want to throw people off and have them think the whole ocean is doomed,” Mr. Greenberg said.

But global warming may offer new opportunities for fish on the brink. “With warming and the expansion northward of species like salmon we may be given a second chance not to dam the rivers,” the author said.

Historically Mr. Greenberg’s home state of Connecticut was a paradise for spawning anadromous species, with wending freshwater rivers that emptied into Long Island Sound. Some 6,000 mill dams later, Atlantic salmon, river herring and shad are all but gone in Connecticut. The textile mills the dams powered have vanished as well and all that remains are the names of rivers and landmarks that point to its once fecund past. The phenomenon is familiar throughout the area, including at Salmon River in New York and Sheepshead Bay between Brooklyn and Coney Island.

“People think its called Sheepshead Bay because it looks like a sheep’s head,” Mr. Greenberg said. “No, Sheeps­head is a kind of fish that was once plentiful there.

“These place names are the archives of what we’ve lost,” he said as he walked back down Squid Row.