Artificial Habitats for Freshwater Fish

February 22, 2024

Question: Why does CDFW build artificial fish habitat in California lakes?

Answer: There are several reasons for CDFW to install artificial habitat in reservoirs around the state. Structures can be placed next to spawning areas to provide protective cover for juvenile fish. These constructions also attract larger fish, providing prime fishing opportunities for anglers.

Artificial fish habitat come in all shapes and sizes, whether orange trees, wood structures or other artificial man-made materials. Manzanita shrubs, Juniper trees and even used Christmas trees have been used for habitat purposes. Softwood like avocado trees are avoided because they deteriorate faster in the water.

Biologists might sink as many as 100 structures at different depths in just one reservoir. Crews also place different types of habitat structures along the shoreline when reservoir levels are low, providing a good area for fish habitat once the waters rise. About two dozen reservoirs contain artificial habitat, from Sutherland in San Diego County to Whiskeytown Lake in Shasta County.

One example is the use of large PVC piping in several Southern California lakes. CDFW places circular pipes, 12 inches in diameter and three feet long, in water hoping to attract catfish. Catfish are known as cavity-nesters and once the males have prepared the pipe for spawning by clearing out any debris, females follow and lay their eggs. The males then return to guard the nest and use their fins to fan the eggs to oxygenate them. Biologists will return to the spots where they’ve placed habitat structures to determine their effectiveness.

With two strong rainy seasons in California, many of the state’s reservoirs are filled to historic water levels, which lessens the need to install artificial habitat. Heavy rains raise reservoir water levels which in turn inundates natural habitat along the shoreline. Although this is beneficial for now, our biologists are planning future projects to continue to improve fisheries habitat in times of drought to ensure fish populations stay healthy.