Sturgeon, often called “living fossils,” are an ancient group of fish with a lineage stretching back over 150 million years, inhabiting various aquatic environments from freshwater lakes and rivers to brackish and marine coastal waters. Characterized by bony plates called scutes and elongated bodies, their unique appearance is distinctive. Understanding their diet and feeding behaviors offers insights into their ecological role as bottom-dwelling inhabitants.
The Core Diet of Sturgeon
Sturgeon are primarily benthic feeders, foraging for food on or within the bottom sediments of their aquatic habitats. Their diet largely consists of a wide array of invertebrates, reflecting their opportunistic nature and reliance on readily available prey. Common food items include worms like polychaetes and oligochaetes. Aquatic insect larvae, such as mayflies, midges, and caddisflies, also form a significant part of their diet.
Beyond worms and insect larvae, sturgeon consume crustaceans like crayfish, shrimp, and amphipods. Mollusks are another staple, with clams, snails, and mussels expertly extracted from the substrate. While invertebrates form the bulk of their diet, some larger sturgeon species, such as white sturgeon, may also incorporate small fish, including salmon, flounder, herring, and suckers.
How Sturgeon Hunt and Feed
Sturgeon possess specialized anatomical features that enable their unique bottom-feeding strategy. They have four sensory whiskers, known as barbels, located in front of their mouths. These barbels are highly sensitive and are used to detect food items buried in the mud or resting on the substrate, especially in low-light or turbid conditions where visibility is limited. Once prey is located, sturgeon employ a distinctive suction feeding mechanism.
Their mouths are protrusible, meaning they can extend rapidly downward and outward to create a vacuum-like suction. This action allows them to draw in food, along with sediment, from the bottom. Sturgeon lack teeth in their adult stage, so they swallow their prey whole. Any ingested pebbles, sand, or gravel are then expelled through their gills. This efficient method allows them to process large quantities of substrate to extract their invertebrate prey.
Variations in Sturgeon Diet
The diet of sturgeon can vary depending on several environmental and biological factors. Species-specific preferences play a role; for example, while many sturgeon are primarily invertivorous, certain larger species consume more fish. Age also influences dietary composition, with newly hatched larvae consuming microscopic organisms like copepods. As sturgeon grow into juveniles, their diet expands to include small macroinvertebrates such as insect larvae and small freshwater shrimp.
Habitat type significantly impacts food availability, leading to dietary shifts between freshwater, brackish, and marine environments. For instance, sturgeon in estuarine settings might feed on crustaceans and mollusks common to those areas. Seasonal changes also affect what sturgeon eat, as the abundance and types of invertebrate prey fluctuate throughout the year. Sturgeon are opportunistic feeders, adapting their diet to whatever food sources are most available in their specific environment.