Development of New High-Gradient Indices of Biotic Integrity for Wadeable Rivers and Streams in New Jersey

The New Jersey Bureau of Freshwater and Biological Monitoring has been conducting Fish Index of Biotic Integrity (FIBI) monitoring on rivers and streams (>4-miles²) in the Northern part of the state since 2000 using Karr’s original IBI format with several regional modifications.  The NJ Fish IBI serves several purposes including identifying waters with aquatic life use impairments 303(d), assessing the waters of the state 305(b), nominating quality streams for special anti-degradation protection, and tracking streams with natural trout reproduction.  In an effort to increase the overall performance of the IBI and to assess smaller headwater streams (<4-miles²), a new design and approach to metric development was evaluated on approximately 230 high gradient streams.  This design, developed by Whittier and Hughes, has been implemented for numerous Western U.S. studies, as well as the Connecticut multi-metric indices (MMI).  Analysis resulted in two distinct stream classes; a coldwater community (Headwaters IBI) consisting of brook trout, sensitive salamanders, and native crayfish and cool/warmwater fish communities (Northern FIBI).  Over 140 metrics from ten ecological classes were tested for signal to noise (S/N), range, responsiveness, and redundancy.  A total of eight metrics were selected for the Northern FIBI and six were selected for the Headwaters IBI.