Most people are vaguely aware that eating fish is good for your health, but may be bad for the ocean. Exactly what is bad (overfishing? Mercury contamination? Fish farming?) is somewhat fuzzy, and how bad it is (probably should not eat whale, and shrimp trawling is worrisome, but catfish seems to be fine…right?) is fuzzier still. Some species are almost blacklisted (Bluefin tuna) while some have no wildlife advocates in sight marching for them (tilapia, cod).

All this confusion is understandable, considering the number of fish species commonly available at supermarkets or on restaurant menus. After all, “fish” represents an entire class of vertebrates—imagine a picky child refusing to eat “mammals”—though we often lump them together as a single unit comparable to chicken, pork, and beef, or turkey. Not to mention the inclusion of shellfish and “seafood,” which would extend the category to everything from scallops to octopus. Bring all this up to someone shopping for dinner with hungry children in tow and it would be understandable that she would choose to ignore the details in favor of simplified instructions. Fish sticks: yes or no? Chicken of the sea: good to go?

In Four Fish: The Future of the Last Wild Food (2010, Penguin Press), Paul Greenberg has done all the hard work for us, simplifying the wide issue of responsible fish consumption to the four major species dominating the modern seafood market: salmon, sea bass, cod, and tuna. If you are like me, you have only the vaguest of notions to what animals these names even signify; before reading this book, I knew that tuna fish were large and made good sushi, that salmon was pink and swam upstream to spawn, that cod was something white and fried, and sea bass was—well, I didn’t really know what sea bass was (besides a fish).

Four Fish will interest readers in one or both of two ways: First, as a story of humankind’s relationship with these four species of fish as food, as well as an account of the rather recent processes of domestication and implementation of fish farms. Secondly, as a guide to what should be done to ensure sustainable wild populations of fish. Paul Greenberg succeeds wonderfully on the first count, but is not so clear about the second.

Greenberg’s writing is easy and entertaining but still highly informative, giving a well-colored picture of each fish’s current situation and future prospects in the modern fishing industry. Greenberg has been a non-professional fisherman all his life and he connects easily with the professional fishermen he interviews. It’s clear that he has profound respect for these animals and an intimate knowledge of their behavior. He treads the line between wildlife advocate and practically-minded industry professional, steering clear of hard lines that turn many people off of conversations on ethical eating, while acknowledging the need for sustainable fishery practices. Much of his arguments center around a discussion of whether to fish from the wild or domesticate fish to raise in farms—and which, if either, might be better for individual species. Unlike cows, pigs, or chicken, which have been domesticated for millennia, fish production relies on wild catches in huge numbers. Though we are now at a turning point; aquaculture is the fastest growing food production system today, and farmed production of fish has likely already surpassed wild production.

The book begins with salmon, a species with a close relationship to humans. They often populate the rivers and streams flowing through our communities, and they have been domesticated going back several centuries. Salmon were the first fish to suffer from human industrialization, notably the pollution of rivers and streams and the damming of local waterways that serve at the salmon’s spawning routes. Salmon numbers have declined drastically. There are only two significant remaining wild populations of salmon: inEastern Russia and Alaska. Now virtually all the salmon available on the market is farmed, as salmon are well-suited to controlled breeding. But salmon monocultures produce an astounding quantity of refuse and encourage disease, polluting the ocean and exposing fish to horrible conditions. Additionally, wild populations may continue to shrink as farmed salmon (that have not been bred to survive in the wild) escape and invade their fragile numbers.

Greenberg nicknames sea bass “the holiday fish,” referring to its past image as a high-quality fish suitable for special occasions. Sea bass is the fish commonly seen on menus as branzino, or bar and loup de mer in French. Sea bass is widespread and universally well liked, but it is particularly ill-suited to domestication—decades of dedicated research led to its domestication by the 1980s. Barramundi, on the other hand, is an ideal species for domestication. They live off of mostly vegetable feed and are highly efficient at converting the feed to protein gain. They are the only fish that can create omega 3 fatty acids from vegetable oils. The sole problem is one of marketing—people don’t know what barramundi is, and they don’t buy it.

Cod is our industrial fish, and as such (no surprise here) seriously overfished. But farming cod presents many of the same problems as farming salmon. Cod are carnivorous and require a lot of protein feed to gain weight—actually, farmed cod can produce a net loss of protein. That’s a lot to pay for fish sticks and Fillet-o-Fish sandwiches. Greenberg concludes that cod should be fished in the wild on a small scale, not farmed. His solution? Tilapia or the Vietnamese freshwater fish tra, two options which he argues are much more economical for farmed industrial operations—they multiply quickly, are hardy and cheap to raise, naturally abundant in the wild, and have “unfishy” tastes that appeal to a large market. This could be a practical substitute for cod.

Tuna is a thorny issue. There are many kinds of tuna: longfin albacore, which is used for canned tuna, and ahi (yellowfin and bigeye). Atlantic bluefin tuna are just about the biggest, fastest, strongest fish in the world. Greenberg describes these animals with reverence, while fishermen revere them for the prices they bring in. One bluefin can sell for $150,000. Their numbers are perilously low and the demand is still rising. Forays have been made into farming bluefun but the costs are prohibitive. Greenberg seems reluctant to admit this, but perhaps, he says, we shouldn’t eat tuna. The Japanese will miss their sushi but Greenberg brilliantly points out that the seemingly unquenchable taste for toro, or fatty tuna belly, is a relatively recent phenomenon, motivated by availability and cheap supply. He seems to want to promote tuna out of the group of animals that we eat and into the group of animals that we like. People refuse to eat whale or dolphin nowadays, out of respect for these animals, but at the time of Moby Dick whales were just a fish like any other. Why can’t we change the public perception of bluefin too?

In sum, what Greenberg advocates to save declining numbers in the wild of each of these fish is industrial farming. But, he says, we should choose carefully which species to farm based on their success in intensive conditions and their feed conversion rates. Species that convent efficiently and are able to digest vegetable feed should be valued in order to minimally impact the environment. Polycultures should be developed to minimize waste and close the natural cycle. Wild fishing should exist in small-scale operations, avoiding trawling and other environmentally damaging methods.

But I think Greenberg’s argument is based on a false premise: that the world needs a greater and greater supply of fish. Certainly increasing populations in areas that are dependant on fishing for food supply, Senegal for example, will demand a greater supply of fish. But in the United States, where two-thirds of us are overweight, do we really need more and more fish, especially industrially produced processed fish that makes its way to us in fish sticks and fried filet sandwiches? Greenberg writes, “at the world’s present rate of consumption, humanity needs about 40 billion pounds of codlike fish annually.” Really? We need it? Greenberg seems to take current consumption levels as indisputable. Perhaps what we need is to decrease our consumption of fish (and all animal products, if you ask me).

I admire the respect and attention Greenberg gives to the lives of these wild animals that most people never give a thought to. However, I am uncomfortable with his distinction between wild fish deserving of our respect and those merely “suitable” for industrial farming. He seems to imply that what he considers a beautiful, impressive animal such as a bluefin tuna should be rescued and protected—but tilapia? An organic machine to produce protein, is all.

The most serious problem with Four Fish is how it approaches the issue of consumer choice. This is the question we’ve all been waiting for: so how will all this information help me become a more responsible consumer? Greenberg’s answer is, it won’t. He essentially debunks informed consumer choice as if it’s a myth. He dismisses a change in personal eating habits as ineffective and unreasonable difficult. This is a man that ordered bluefin tuna carpaccio in a restaurant days after publishing an op-ed in the New York Times counseling against its consumption. “To most people an animal is either food or wildlife” he writes, suggesting that people are incapable of respecting the welfare of animals and eating them at the same time, at least on an industry scale. He continues to say that if a fish is put on the market, people will inevitably eat it. So the solution is to prevent that fish getting to market, not campaign to reject it once its there. But historically, campaigns against the consumption of specific animal products, whether for reasons of health or welfare, has worked. There was an anti-cholesterol campaign in the 1980s, which significantly reduced the amount of beef Americans consumed. Ditto for butter, and an anti-cruelty campaign against veal pretty much removed this meat from general consumption in theUnited States.

In the case of bluefin tuna, however, evidence suggests that for every person who refuses to order there are two people more than happy to step in. It’s undeniably true that government action is more effective at effecting change than consumer choice. Regulations are needed to protect vulnerable wild populations of fish and make sustainable fishing lucrative for the industry. I respect Greenberg’s view that any individual participation in preventing fish from extermination or harm should be attentive and informed, beyond a color-coded eating guide from the Monterey Bay Aquarium. People need to be actively political, instead of naively believing that choosing chicken over salmon will save the species. I’m reminded of the recent controversy over the KONY 2012 campaign—tweeting about Joseph Kony is only helpful if it inspires people to inform themselves further about the issue and take real political action.

And yet for the day-to-day, the one thing that every single person can control is what they choose to buy and eat. This gives us agency in a world where our food is produced in ways beyond our control or understanding. Does Greenberg really expect someone who continues to eat farmed sea bass to convincingly champion their cause? What message would it send to others, sitting down to a fish and chips dinner and proclaiming the environmental waste of cod aquaculture? I believe in consumer choice. I believe in learning about where your food comes from too.

My advice is: read Four Fish and get to know your salmon fillet, fish and chips, and maguro sushi. But don’t forget that at the end of it you can still choose not to eat them.