Cod fish, including Atlantic cod (Gadus morhua) and Pacific cod (Gadus macrocephalus), are often described as bottom feeders, but this term is misleading. They are scientifically classified as demersal fish, meaning they live and feed on or near the seabed in the cold, deeper regions of the North Atlantic and North Pacific oceans. While they forage along the ocean floor, their feeding habits distinguish them from the purely scavenging organisms often associated with the term “bottom feeder.” Cod are highly valued globally and function as active predators within the marine ecosystem.
What Defines a Bottom Feeder
The term “bottom feeder” lacks a precise scientific definition, though it generally refers to aquatic animals that feed on or near the ocean floor, known as the benthic zone. Fish are broadly categorized by where they live and feed in the water column. Pelagic fish, such as tuna and mackerel, inhabit the open waters away from the bottom and shore.
Demersal fish, often called groundfish, live and feed near the bottom substrate, including areas over the continental shelf and slope. Benthic fish, like flounder or rays, are denser and rest directly on the seafloor, often feeding on immobile organisms or detritus.
Cod, however, are benthopelagic fish, meaning they maintain a neutral buoyancy and swim freely just above the ocean floor. Their structure, unlike the flattened bodies of true benthic fish, allows them to ascend into the water column to pursue prey. While they operate in the demersal zone, they are not restricted to eating only detritus or material found strictly on the bottom.
The Demersal Diet and Habitat of Cod
Atlantic and Pacific cod inhabit the demersal zone, which typically consists of gravel, sand, or rocks in waters ranging from the shallows to depths of over 600 meters. Their foraging behavior is that of an opportunistic and voracious predator, not a passive scavenger. Cod possess a chin barbel, a sensory organ that helps them detect prey along the seabed in dark, deep-water environments.
The diet of adult cod primarily consists of actively hunted species rather than organic waste or marine snow. They consume smaller fish like capelin, herring, and sand eels, which swim both near the bottom and in the water column. They also prey upon larger invertebrates, including shrimp, crabs, and mollusks that live on or just above the substrate. Stomach content analysis shows that larger cod are even known to practice cannibalism, consuming juvenile cod.
Quality and Safety for Consumption
The concern about cod being a “bottom feeder” often stems from the misconception that fish living near the seabed are inherently dirty or high in contaminants. However, cod is generally considered a highly safe and healthy choice for consumption. This is due to its physiological characteristics and position in the food chain.
Cod is a lean fish, meaning its flesh contains very little fat, typically between one and four percent. Contaminants like heavy metals and persistent organic pollutants tend to accumulate more readily in the fatty tissues of marine animals. The low-fat content in cod means it naturally accumulates fewer fat-soluble toxins compared to fattier fish.
Cod has low concentrations of mercury, averaging around 0.111 parts per million (ppm), according to data from the U.S. Food and Drug Administration. This level places cod in the “low-mercury” category, far below the levels found in larger, longer-lived pelagic predators such as swordfish or shark. Its low mercury content makes it a recommended choice for most consumers, including pregnant women and young children.