Predation on Fishes in the Sacramento-San Joaquin Delta: Current Knowledge and Future Directions

Gary Grossman

Full article

Key points:

  • Predator-prey relationships are not static entities and there is a great deal of uncertainty surrounding predation in the Delta.
  • Predation involves several components, which are affected by a variety of changes that have occurred in the Delta.
  • Most fish predators identified were invasive species, while most non-fish predators were native species, and most prey fishes consumed were invasive species.
  • Thirteen hot spots were identified in the Delta. Hot spots are areas where physical conditions (e.g., unnatural or reversed flow patterns, structures such as fish ladders, pipes, modified channels or impoundments) combine to make predation more likely than in unaltered habitats.
  • Control of invasive predatory fish is a common management strategy, but it has not had a high success rate.