Whiting fish are carnivorous predators whose diet shifts based on their size, location, and prey availability. The term “whiting” broadly refers to several species, such as the European whiting (Merlangius merlangus), which share a common, opportunistic feeding strategy. While generally bottom-dwellers (demersal), they actively hunt throughout the water column, consuming a wide range of invertebrates and smaller fish. This opportunistic nature allows them to capitalize on the most calorie-rich food sources available.
The Predominance of Benthic Invertebrates
The foundational part of the whiting diet consists of organisms that live on or within the seafloor, known as benthic invertebrates. Many whiting species are physically adapted for this type of feeding, possessing mouths positioned to root or suck up prey from the substrate. This makes slow-moving or stationary creatures a consistent and reliable food source, particularly for younger or smaller individuals.
A large portion of this benthic diet includes various types of marine worms, specifically polychaetes, which they often encounter while foraging in the sandy or muddy bottom sediments. They also consume numerous small mollusks, such as bivalves and gastropods, which are ingested along with the substrate. Sedentary organisms like certain echinoderms are also consumed.
Many crustaceans that live near the bottom, known as epibenthic species, are also frequently targeted, including amphipods and mysids. These prey items are often consumed more heavily during the night when whiting tend to feed closer to the seabed. This reliance on bottom-dwelling food establishes a baseline diet that provides steady nutrition.
Opportunistic Feeding on Smaller Fish and Crustaceans
As whiting grow larger, their feeding strategy broadens and becomes increasingly focused on higher-trophic-level prey. Adult whiting become significantly piscivorous, meaning their diet is dominated by other fish species, which provide a greater energy return than smaller invertebrates. They actively pursue small schooling fish, like sand eels, sprats, and juvenile herring, often moving up from the seabed into the water column to hunt.
This change in diet is highly opportunistic, as whiting will prey on whatever small fish are locally abundant, including the young of commercially important species like cod and haddock. They are capable of ingesting prey that is a significant fraction of their own body length. This shift to actively hunting pelagic (free-swimming) fish often occurs during daylight hours when schooling prey are more accessible.
Crustaceans remain a significant part of the diet for larger whiting, but the species consumed are typically larger than their benthic counterparts. This includes commercially valuable shrimp, such as crangonids, and small crabs. Larger whiting also opportunistically consume cephalopods, with squid being a common, calorie-dense addition to their feeding repertoire.
How Diet Varies by Life Stage and Habitat
The diet of whiting undergoes a pronounced transformation, or ontogenetic shift, as the fish matures. Newly hatched whiting larvae, which are pelagic and drift in the water, begin their lives by feeding on microscopic organisms, primarily the nauplii and copepodite stages of copepods. As they grow into juveniles, they shift to consuming small crustaceans like amphipods and mysids, along with tiny polychaete worms.
The transition to a fish-heavy diet is closely linked to size. Adult whiting over approximately 30 centimeters in length often consume fish almost exclusively. This size-dependent shift means that a whiting’s primary food source moves from invertebrates to fish as it grows. The exact size at which this transition occurs can be influenced by regional differences in prey availability.
The specific habitat and season also introduce variation in the whiting diet. For example, in the Western Baltic Sea, larger whiting may rely more heavily on clupeid fish, which can constitute up to 90% of their diet, compared to whiting in the North Sea. Seasonal changes can also affect feeding intensity; for instance, some populations show an increase in feeding on copepods during nutrient-poor winter periods.