The Role of Fish in Lakes

general role of fish

• regulate food web

• planktivorous fish - reduce zooplankton, increase phytoplankton

• piscivores - increase zooplankton, decrease phytoplankton

• fish influence nutrient cycling, energy flow, and habitat use

fish community change by…

• temperature

• oxygen availability

• habitat structure

• nutrient status

• climate change

human impacts on fish

• overfishing

• species introductions

• habitat alteration

• pollution

• warming and hypoxia

biomanipulation

deliberately altering fish communities to improve water quality

consequences of biomanipulation

• systems may shift back due to alternative stable states

• internal nutrient loading may persist

• zooplankton may not recover as expected

why fish are indicators of biological health

• they integrate long-term environmental conditions

• they respond to temperature, oxygen, contaminants, and habitat quality

• changes in fish reflect cumulative ecosystem stress

DELT

• deformities

• eroded fins

• lesions

• tumors