River Ecology and Restoration - River Dynamics and Integrated River Management - page 677

least 3 km of contiguous river channel too deep to be effectively sampled by wading. Lyons et al. (2001)
used fish assemblage data from 155 main-channel-border sites on 30 large warmwater rivers in Wisconsin
(including 19 sites on the Mississippi River) to construct, test, and apply a large river IBIs. Fourteen sites
were sampled more than once for a total of 187 samples. Watershed drainage areas for these sites ranged
from 349 to 218,890 km 2 . Lyons et al. (2001) used some of Karr's original metrics while adding several
different metrics. A main difference is that instead of just considering the proportion of individuals (i.e.
numbers-based metrics) the large river IBI also considers the proportion of fish by weight (i.e. biomass-
based metrics). Such biomass-based metrics best reflect the amount of energy flow across trophic levels
and functional groups, whereas numbers-based metrics indicate the diversity of pathways that energy
could follow and the potential for intra- and inter-specific interactions (Lyons et al., 2001).
The large river IBI for southern Wisconsin is listed in Table 10.5. Definitions of some of the “new”
metrics are given as follows (Lyons, 1992; Lyons et al., 2001):
Weight per unit effort— Weight (biomass) to the nearest 0.1 kg of fish collected per 1600 m of
shoreline, excluding tolerant species.
Total number of native species— The total number of species collected at a site, excluding hybrids
(which are common among sunfish and certain minnow species) and exotic species.
Total number of riverine species— Number of species that are obligate stream or river dwellers not
normally found in lentic habitats.

Index of Biological Integrity (IBI) for large rivers in southern Wisconsin (after Lyons et al., 2001)
Scoring criteria

T able 10.5

Metrics

10 5 0

1. Weight of fish per unit effort > 25 kg 10-25 kg 0-9.9 kg

2. Total number of native fish species >15 12-15 0-11

3. Number of suckers species >4 3-4 0-2

4. Number of intolerant species >2 2 0-1

5. Number of riverine species >6 5-6 0-4

6. Proportion of individuals with disease, tumors fin damage,
skeletal anlmalies (DELT)

<0.5% 0.5%-3% >3%

7. Percent of individuals as riverine species >20% 11%-20% 0%-10%

8. Percent of individuals as simple lithophilous spawners >40% 26%-40% 0%-25%

9. Percent of insectivores by weight >39% 21%-39% 0%-20%

10. Percent of round suckers by weight >25% 11%-25% 0%-10%

Percent of individuals as simple lithophilous spawners —The number of individuals that belong to
species that lay their eggs on clean gravel or cobble and do not build a nest or provide parental care,
expressed as a percentage of the total number of fish captured. Simple lithophilous species need clean
substrates for spawning and are particularly sensitive to sedimentation (embeddedness) of rocky
substrates. Hybrids are included in this metric only if both of the parental species are simple lithophilous
species.
The total IBI scores then yield the following biological conditions categories: Excellent >80,
Good 60-79, Fair 40-69, Poor 20-39, Very Poor <20. Lyons et al. (2001) found that the Wisconsin
large river IBI was comparable to IBIs developed for use in large rivers in Ohio (including data for the
Ohio River) and Indiana. The fact that the IBI metrics in Table 10.5 reflect conditions on the Mississippi
River and Ohio River indicate that these metrics might be a good beginning point for developing IBIs for
the other large rivers of the world.