Sturgeon are ancient fish known for their distinctive appearance and bottom-dwelling habitat. These creatures have inhabited Earth’s waters for millions of years and rely on a specialized diet. Understanding what sturgeon consume provides insight into their ecological role as bottom-feeders.
The Varied Diet of Sturgeon
The diet of sturgeon changes as they progress through different life stages. Newly hatched larvae primarily consume microscopic organisms like copepods. As they grow, their diet expands to include small macroinvertebrates such as the larvae of mayflies, midges, and blackflies. Young sturgeon possess small teeth, which they lose as they mature, indicating a shift in their feeding strategy.
Juvenile sturgeon transition to a diet of small freshwater shrimp, insect larvae, and fish eggs. Common prey items include amphipods and aquatic insect larvae. This dietary phase supports their growth before they become larger foragers.
Adult sturgeon are benthic feeders, consuming a wide array of organisms from bottom sediments. Their diet includes mollusks like clams, snails, and mussels, along with worms such as polychaetes and leeches. Crustaceans like crayfish and shrimp are also common food sources. While most sturgeon remain invertivorous, some larger species, such as the white sturgeon and pallid sturgeon, incorporate small fish into their diets, including salmon, flounder, herring, and suckers. Their specific diet varies by species and environment (freshwater, saltwater, or anadromous).
Unique Ways Sturgeon Find Food
Sturgeon possess specialized adaptations to locate food in murky habitats. Four sensitive, whisker-like barbels are located on the underside of their snout. These barbels drag along the riverbed or seafloor, housing taste buds that help sturgeon detect prey through scent, feel, and vibrations in low visibility.
Their mouth is designed for bottom-feeding, being toothless, wide, and highly protrusible. When a sturgeon finds prey, it extends its mouth downward like a siphon, creating a powerful vacuum to suck up food and sediments. Food is swallowed whole, and inedible material like pebbles or sand is expelled. A muscular stomach then crushes the ingested food for digestion.
Beyond touch and taste, sturgeon employ an electroreceptive system to detect hidden prey. Sensory pores, known as ampullae of Lorenzini, are located on their head and snout. These electroreceptors are sensitive to weak electrical impulses from other animals, enabling sturgeon to pinpoint prey even when buried or obscured. This combination of sensory abilities allows sturgeon to feed non-visually in dark, benthic environments.
How Environment Shapes Sturgeon Diet
Environmental factors influence sturgeon diet. Water temperature affects sturgeon activity and prey availability. In warmer temperatures, sturgeon show increased feeding activity. The abundance of invertebrate prey can fluctuate seasonally, with some insect larvae dominating the diet during specific seasons due to their life cycles.
Water quality and habitat structure also affect food availability. Degraded water quality can reduce benthic community productivity, impacting prey. The composition of the riverbed or lakebed, like rocky versus soft sediments, dictates which invertebrates thrive, influencing sturgeon foraging success. Compacted sediments, for example, can make it difficult for sturgeon to access buried prey.
Sturgeon are opportunistic feeders, adapting their diet to what is readily available. Ecosystem changes, such as non-native species introduction, can alter benthic communities, forcing sturgeon to shift preferences. As sturgeon forage, they engage in bioturbation, stirring bottom sediments. This activity affects nutrient cycling and the distribution of other bottom-dwelling organisms.