As a dietitian, I recommend eating fresh fish at least once a week. Less than half of all Americans eat fish on a regular basis, and if they do, it’s usually at restaurants. This is unfortunate, since fish has significant health benefits. Even the consumption of small portions can help reduce the risk of heart disease and stroke. Experts point out that fish oil, which is rich in omega-3 fatty acids, is the principal benefactor. Cold-water and deep-sea fish, such as salmon, tuna, mackerel and herring have especially high levels of this fat. This is the upside.

Regrettably, wild fish is also exposed to numerous pollutants. Hazardous chemicals, such as methylmercury and polychlorinated biphenyls, may pose health risks that increase with frequency and quantity of consumption.

For this reason, the Food and Drug Administration and the Environmental Protection Agency advise that women of childbearing age and young children should avoid eating certain fish in large quantities, particularly carnivorous fish (bigger fish that eat smaller fish), such as swordfish, king mackerel, tuna, shark and tilefish. The rationale is that larger fish species have a longer life span and therefore have more time to accumulate pollutants in their system, both from their environment and their food supply. Consequently, by eating these larger fish, we expose ourselves to a whole chain of potentially harmful chemicals, some of which are known to be carcinogenic. Smaller species, such as shellfish, cod, sole, herring and sardines are considered to be less problematic in this regard.

Another issue is overfishing. Traditional harvesting methods of the international fishing industry are no longer sustainable, at least not at the current rate. Prices for wild-caught fish have skyrocketed in recent years and fishing restrictions are on the rise. In California, the commercial fishing season for salmon has been called off (again), because of record-low numbers of Chinook reported by the state’s fishery management department.

Indeed, we’re running out of fish ­– globally. The entire world population of some fish species has now been decimated by more than 90 percent and counting. The only realistic alternative to open-sea-fishing at this point, so it seems, is fish farming, also known as “aquaculture.” Fish farms raising fish in enclosed ocean pens and freshwater ponds have been expanded dramatically in recent years and supply now more than half of all the seafood available. Especially Southeast Asia has seen a spectacular boom in fish farming. With the ever-growing global appetite for seafood on the one hand and the progressive depletion of the world’s fish population on the other, aquaculture is here to stay.

But there are grave concerns about the environmental impact of fish farming as well. Raising large amounts of fish in tightly confined waters is a messy business. Growth hormones, antibiotics and even chemicals for artificial coloring of fish meat are routinely added to the feed. There are no internationally binding rules or regulations to speak of for fish farming methods yet, and even if that were to happen, uniform enforcement would be a nearly impossible task considering the enormity of the global market forces involved.

Thankfully, there are also some serious efforts on the way to make fish farming cleaner and more sustainable. For the first time, an advisory board of the United States Department of Agriculture has issued criteria for farmed fish to be labeled “organic.” It’s a tricky undertaking, since fish farms by nature cannot provide the same controlled environment as other livestock farms. Fish grown in open sea waters remain exposed to outside pollutants whether they are kept in cages or swim freely. It has been pointed out that fish farms may harm the environment further by adding concentrated waste and disease, not only within their facilities but also in the larger region around them.

At this point in time, it is safe to say that consumer confidence in fish farming is not great. Those who can afford the high prices will go for the wild-caught variety, as long as it is available. Eventually, however, we will have no choice but to look for the best farmed seafood money can buy.

Locally grown food has always appealed to me. That’s why I prefer to do my grocery shopping at the neighborhood farmer’s market. A few years ago, I paid a visit to a shellfish farm in the San Juan Islands. The owner was kind enough to take me on his vessel for a harvesting trip. The water was crystal clear and the surroundings serene. I observed the men of his crew as they retrieved the nets and emptied them out. Then, without delay, they cleaned, packed and shipped the fresh bounty. Having personally come to see the quality of their work gave me confidence that I was getting good seafood there. I would like to have more experiences like this in the future.

Timi Gustafson is the author of “The Healthy Diner – How to Eat Right and Still Have Fun.” Her book is available in bookstores, at her blog or on Amazon.com – To receive her free monthly newsletter by e-mail, you may send a request to timi@thehealthydiner.com