While terrestrial seasons are relatively fixed geographically (just try growing peppers in frozen soil), the seasons of the sea are more fluid. Different species of fish populate different parts of the ocean at different times depending on water temperature, individual breeding habits, and the migration of prey. Atlantic herring, for example, are more likely to be found in Chesapeake Bay between January and March as they migrate to the Gulf of Maine.
When and where fish spawn is also a factor in determining whether or not they are in 'season.' Disturb that Atlantic herring during reproduction and there's a danger not only of depleting stock in the short term but also of altering the food chain long term, affecting the availability and health of other fish (in this case, the increasingly popular Atlantic tuna) and changing the migratory patterns of yet others.
When this sort of snowball effect goes into motion, it leads to overreliance on industrial fishing operations, which tend to travel into deeper waters with high-tech equipment to take a heavy toll on the ecosystem. There's also a tendency to import fish from countries with lax environmental regulations.
Short of moving to Cape Cod, the best way to suss out what's in season where is to do your homework before hitting the seafood counter. A good place to start is The Fish List (www.thefishlist.org), a stockpile of consumer-friendly seafood information created by a reputable trio: the Monterey Bay Aquarium, Blue Ocean Institute, and Environmental Defense. The more you know about the status of various species of fish, the better equipped you are to diversify your seafood selections and help fisheries maintain a sustainable balance of supply. You might also be surprised by the options. Hankering for the texture and flavor of red snapper? If it's in short supply, striped bass is a tasty substitute.
While information about seasonal seafood is beginning to make its way into the mainstream, it is still a relatively new concept in the industry, introduced in 1996 with the Sustainable Fisheries Act, which was designed to protect fish in certain areas during certain times of the year so they can spawn, feed, and breed. Further study of the human health benefits of seasonal fish is needed to convince consumers that the issue transcends environmentalism to affect everyday diet. According to U.S. Department of Agriculture testing, for instance, wild salmon have more of the healthy omega-3 fatty acids essential to prevent various diseases than farmed salmon.
If the recent surge in demand for food from small, local, ecologically responsible farms is any indication, chances are good that consumers who have already begun to appreciate the quirky beauty of heirloom tomatoes, and the homegrown terroir of local cheese, will acquire a taste for what our seas can support.