Prey Abundance

The abundance of small fish and crustaceans is a key metric of Everglades food webs because they feed iconic apex predators including wading birds and alligators. Diminished production and availability of fish and crustaceans during the critical nesting season has been linked to diminished nesting success of these key predators. Abundance of prey species is closely tied to hydrological variation and periphyton quantity and quality, which are sensitive to management actions affecting timing and quantity of water delivery and water quality. Small fish and crustaceans have short generation times, a year or less, and their abundance responds to hydrological management at an annual time scale, recovering from marsh drying events over three to seven years.

See the results for prey abundance in the Greater Everglades.

Photo credit: South Florida Water Management District.

How is it measured?

Sampling methods of small fish and crustaceans are well evaluated and use of a 1-m² throw trap provides readily interpretable information; a substantial resource of historical information gathered using this approach is available. Targets for the aquatic fauna metric are dynamic based on observed rainfall and resulting hydrological fluctuation observed in the mid-1990’s when high rainfall and management in the southern Everglades generated water stages like those predicted for the pre-management ecosystem. In years with low rainfall, the target is lower abundance of fish and crustaceans than in periods of greater rainfall. Dynamic targets avoid assigning a low performance score for years when little rainfall made it impossible for managers to support production of high prey biomass.