Index Of Biotic Integrity Metrics Research Articles

First data on an Index of Biotic Integrity (IBI) based on fish assemblages for the assessment of the impact of deforestation in a tropical West African river system

African tropical rainforests, and especially their freshwater biodiversity, are seriously threatened by ongoing industrial deforestation. Sound ecological management is needed to ensure the sustainability of these resources. For this purpose, an index of biotic integrity (IBI), based on fish assemblage characteristics, is developed in this paper. It is used to quantify the impact of industrial deforestation on freshwater biodiversity. Data from 30 non-impacted sites were used to develop a series of compositional, structural and functional metrics that reflect sites with a high biotic integrity, i.e. what a stream-fish community should look like in the absence of human perturbation. These data were compared to data collected from sites subjected to substantial forest watershed loss, in order to identify those IBI metrics that best distinguish streams with high and low biotic integrity. The overall IBI scores reflected the quality of the watershed conditions. In addition, there was a close agreement between an index of environmental quality, based on water and habitat quality and the IBI scores, suggesting that the different biological responses of the fish assemblages (observed differences in the IBI scores) were indicative of differences in physico-chemical quality of the streams. The ability of the proposed IBI to index water resource degradation, due to deforestation, suggests that it can be used as a tool for biological monitoring. However, more consistent and comprehensive data are needed to further refine the IBI, especially the assignment of integrity classes and metric threshold values.

Variable Fish Communities and the Index of Biotic Integrity in a Western Great Plains River

We applied the index of biotic integrity (IBI) to the portion of the Arkansas River basin within the Southwestern Tablelands ecoregion, located on the Great Plains of southeastern Colorado. Only nine IBI metrics were appropriate for this region, largely because of the depauperate and tolerant ichthyofauna. The modified index was then used to assess effects of U.S. Army mechanized infantry training on biotic integrity of the Purgatoire River at 12 sites adjacent to the Pifion Canyon Maneuvers Site, a remote and relatively undisturbed canyon reach on a seventh-order Arkansas River tributary. Decrease in abundance of adult red shiners Cyprinella lutrensis, a tolerant omnivorous species, over a 6-year period (1983–1989) caused marked increases in the IBI at 9 of 12 sites despite lack of obvious changes in environmental quality after training began in 1985. Neither sampling variation nor the magnitude and timing of floods were sufficient to explain the large decrease in red shiner abundance. Other attributes of the biota, such as presence of long-lived fishes and lack of introduced species, provided no evidence for detrimental change. The majority of potential IBI metrics were hampered by the low fish species richness, the preponderance of trophic and habitat generalists, or other attributes of the depauperate ichthyofauna. Moreover, human perturbations that cause change in fish communities of midwestern U.S. streams are suspected in many cases to mimic natural disturbances in this system, so they may have relatively little effect. Conversely, some perturbations considered benign in more mesic environments are likely to cause dramatic changes. We therefore propose that our understanding of the structure, function, and natural variation of fish communities in western Great Plains streams must increase substantially before we can define fully appropriate measures of biotic integrity for these lotic systems.

Regional Application of an Index of Biotic Integrity Based on Stream Fish Communities

The recently proposed index of biotic integrity (IBI) was evaluated for several watersheds throughout the midwestern United States. Five of the community metrics comprising the IBI depend on the number of fish species present and must be adjusted for changes in expected species richness with stream size or zoogeography. We use basic relationships of fish species richness versus stream size, calculated from historical fish community data for seven watersheds, to define lines of maximum species richness. These lines are used to predict attributes of “excellent” fish communities, the basis of comparison for assigning scores to 5 of 12 IBI metrics. When zoogeographic and stream-size factors were accounted for in assigning scores, the IBI accurately reflected watershed and stream conditions. As partial tests of the IBI, we found that the index conforms to knowledge of biologists familiar with several watersheds, is independent of stream order in homogeneous watersheds, and is not biased upwards in generally degraded watersheds. Furthermore, analysis of undisturbed fish communities in Illinois and Kentucky support criteria set for percentages of omnivorous individuals and insectivorous cyprinids expected in excellent fish communities. Comparison of maximum species richness lines reveals two groups of similar fish communities, those in woodland streams (Illinois, Michigan, and Kentucky) and those in Great Plains streams (Nebraska, North and South Dakota). We suspect similarities result from ecological factors relating to physical habitat and biotic interactions, rather than from factors such as geologic and climatic history. Received December 10, 1982 Accepted November 9, 1983