fish community IBI

why are fish important for watershed health

sensitive to physical and chemical disturbances, long lived and mobile - they leave disturbed habitats

describe the IBI

• use fish communities as indicators of stream health

• no universal IBI, varies between states

• most federal agencies use it

development of impervious surfaces leads to

degradation of waterbody

bank destabilization is caused by

removal of riparian vegetation and livestock

role of IBI

reduces biological processes to a numberical value and is helpful to non experts, developed for wadeable streams but now can be used on a boat

ibi is semi-____

quantitative

4 categories of IBI

• species richness and composition

• tolerant/intolerant species

• trophic composition

• health and body condition

small head waters and large bodies of water typically have more or less diversity?

less

medium sized rivers typically have more or less diversity

more

species richness and composition include:

• number of native species

• number of shiner species

• number of sucker s[ecies

• number of darter and madtom species

best = high # of all these

sucker species are sensitive to

chemical and physical degradation, they are also long lived

darters and madtoms relate to specificity for

benthic habitats, they are also sensitive to disturbance

tolerant/intolerant species include

• percent interolerant species

• number of intolerant species

• percent lepomis

• best = high intolerants, low % lepomis

high percent of intolerant = undisturbed

trophic composition consists of

percent omnivores

• nutrient enrichment (disturbance) favors generalists

percent invertivores

percent top carnivores

best = low omnivores, high invertivores + top carnivores

health and condition includes

percent DELT (deformities, eroded fins, lesions, tumors) + hybrids

• delts and hybrids indicative of pollution, disturbance

number of lithophilic spawners

• require clean substrate to reproduce

• lack of these = interstices filled with sediment/silt

best = low delts and hybrids and high lithophilic spawners

undisturbed sites have

HIGH - native shiner, sucker, darter, madtom species; high percent and number of intolerant species; invertivores, top carnivores, lithophilic spawners

LOW - percent lepomis, omnivores, delts, and hybrids

bad actions that affect IBI

impervious surfaces - runoff increase (temp, chemicals)

poor riparian zone to buffer nutrient, soil, and water excess

livestock in creek (adds excess nutrients, bank erosion)

good actions that affect IBI

fence livestock from stream

no till farming and cover/forage crops, crop rotation

drawbacks to IBI

need training to identify fish, time consuming to sample across multiple watersheds, some areas have few reference streams - some even highly modified

gsa is representative sample of

fish comunityIB

IBI metrics correspond to

human disturbance