Anchovies are small, silvery fish found in vast, dense schools across the world’s temperate oceans. They are one of the most commercially important forage fish species, renowned for their intense, savory flavor used in numerous global cuisines. Given their small size, a common question arises regarding their natural feeding habits: are anchovies classified as bottom feeders? Answering this requires understanding the ecological definitions of marine life and the anchovy’s role in the ocean’s food web.
Defining the Ecological Term
The term “bottom feeder” is a common label for aquatic animals that live and forage on or near the ocean floor, known ecologically as the benthic zone. True bottom feeders, or benthivores, rely on food sources found in or on the sediment, such as detritus or small benthic invertebrates. These animals often exhibit physical adaptations for this lifestyle, such as a flattened body shape or a downward-positioned mouth.
Primary examples of true bottom feeders include flatfish, like flounder or sole, which rest directly on the substrate and hunt for buried prey. Other examples are eels, which probe the sediment, and certain species of catfish. The diet of these organisms is fundamentally tied to the seafloor environment, separating them from fish that inhabit the open water column.
The Anchovy Diet
Anchovies are positioned at a low trophic level, acting as a crucial link between microscopic organisms and larger predators. Their diet consists overwhelmingly of plankton, which are tiny, drifting plants and animals found throughout the water column. The primary food sources for an adult anchovy include phytoplankton (microscopic plant-like organisms) and zooplankton (small animal organisms).
Zooplankton, such as copepods and crustacean larvae, often constitute the dominant portion of an anchovy’s caloric intake. By consuming these minute organisms, anchovies convert primary production into accessible energy for higher-level consumers. This feeding habit means they function as forage fish, supporting the diets of nearly every predatory fish, mammal, and seabird.
Feeding Mechanism and Habitat
The anchovy’s feeding mechanism provides the definitive answer: they are classic filter feeders. As they swim actively through the water column, anchovies open their mouths to continuously strain microscopic food particles. This process is facilitated by specialized structures within their gills called gill rakers, which act like a sieve to capture the tiny plankton.
While some species, like the European anchovy, can employ a secondary, selective feeding mode to target larger prey, the bulk of their sustenance is acquired through filtering. This active, continuous filtering process occurs in the open water, known as the pelagic zone. Anchovies are highly mobile, schooling fish that inhabit the surface and middle layers of the ocean, often migrating vertically in response to the movement of their planktonic prey.
Their existence as pelagic, open-water swimmers contrasts sharply with the habitat of benthic feeders that dwell near the substrate. Although anchovy larvae may briefly reside near the bottom, the adults spend their lives actively foraging in the water column. Due to their planktonic diet, filter-feeding mechanism, and open-ocean habitat, anchovies are not considered bottom feeders.