Overfishing is a somewhat complicated subject, owing to the complexity of interactions between different species within an ecosystem, various influences on population growth rates, and the different types of fishing and methods of aquaculture. However, there are some clear principles that are important and easily understood, even by those not in the fishing industry. The first is that every species matters. Some may question the importance to an ecosystem of halibut or flounder, for example. The truth is that the homeostasis of energy flows through an ecosystem is finely balanced through predation, breeding, disease, adaptation, and other factors. When a particular species is removed from an environment or even significantly reduced in number, it can no longer fulfill its natural role in the system. The result can be an explosion in the population size of other organisms that compete for resources with or who usually serve as food for the endangered species. That imbalance may then affect other species of both plants and animals that live within the same system. To maintain biodiversity and a stable ocean environment, it is imperative that we prevent overfishing of all species.
It’s also important to understand why some species are more susceptible to overfishing than others. Fish that live in deep, cold waters like orange roughy generally have slower metabolisms, mature later in life, and breed less frequently than those that live in shallower, warmer waters. Fishing methods like deep-sea trawling are especially harmful to these sensitive species because they can be extremely efficient at catching these deep dwellers and are able to operate for long periods of time. As a community’s breeding population is fished out, the ability of the group to replenish itself naturally decreases. At a certain point, the spawning rate sinks low enough that the population as a whole begins to decrease.
While aquaculture at first appears to be a fantastic alternative to open water fishing, it is not without its drawbacks. Because fish farms house large numbers of fish in small areas, they can produce waste water with extremely high concentrations of nutrients and bacteria. When these products are released into the surrounding waters, they can negatively affect native species and produce algal blooms, throwing the local ecosystem far out of balance. In addition, when the algal blooms eventually die off, their decomposition can deplete the water’s oxygen level.
Aquaculture has also been responsible for the introduction of invasive species into the local environment. The newcomers can sometimes outcompete native species for food and other resources, decimating the native populations. Finally, foreign organisms may carry parasites or diseases to which native organisms have no defense. The Japanese oyster drill is an example of a detrimental piggy-backer, coming to North America in the early 20th century within shipments of Pacific oysters.
So, now that you’ve heard all of the doom and gloom, what can you do to help? Fortunately, the answer is easy. Choose fish and seafood products made from species farmed or fished using sustainable practices. There are a number of resources available to help you get on the right track. One of the best is the Monterey Bay Aquarium’s Seafood Watch Pocket Guides website. They have downloadable references that help you choose sustainable fish species specific to each region of the US. Another excellent resource is the Marine Conservation Society’s (MCS) fish purchasing guide. It even breaks down which fish are best to buy by month. Finally, look for sustainability ratings for seafood products in supermarkets. More and more suppliers are packaging their fish with color-coded labels indicating a level of sustainability certified by independent organizations like MCS. They are an easy way to quickly assess what you’re buying and to help make more informed decisions. Choose the right seafood products and benefit from their excellent nutritional properties while helping to save fish populations from collapse. Do your part and we will all be better off in the long run!