FAII (fish assemblage integrity index) is used extensively to assess environmental quality of fish habitat in the world. The method was first raised as IBI (index of biotic integrity) by Karr, then improved and developed by Deegan et al., Kleynhans,Kesminas et al. and Lin Xinhui. However, this method is not yet commonly used in China.
Appled the FAII to the environmental assessment of fish habitat, specifically, the nursery ground in the estuarine waters of theYangtze River. Field work was conducted monthly during the high tide from November 2006 to October 2007 at 13 stations of the Yangtze River estuary, in the surf zone (0.5-1.5 meter water depth) using small trawls (1 m×4 m, mesh size 1 mm). A total of 6734 fish larvae and juveniles, representing 78 species from 29 families were collected. The fish collection consists of marine, estuarine, diadromous and freshwater species. All species are grouped accordingly to the trophic levels, tolerance and the water layer of the habit, only one exotic and one hybrid species. No fish were collected in St.1 and St.13 between November 2006 and March 2007, neither in St.12 between November 2006 and May 2007.
Ten FAII indices are selected to analyze our data based on the fact that our research focus on the surf zone of theYangtze River estuary, and the fish collected are mainly larvae and juveniles. Karr defined nine categories of environment quality based on the FAII values, i.e. 57-60 as "excellent", 45-47 as "general" and less than 24 as "very poor", et al. The FAII value in our 13 stations ranged from 0 to 46 with an average value of 21.08. The maximum FAII value is detected at St. 12 in the month of July. The St.4 has an annual average value of 28, the highest among all 13 stations. The result indicates that the environmental quality of the surf zone in the Yangtze River estuary falls into fair to very poor categories. The hierarchical clustering (based on monthly FAII) shows that the stations could be classified into 4 groups, . FAII of station in poor categories are more fluctuating than that in fair categories. Besides, there is a noticeable seasonal fluctuation of the FAII that is higher in the summer months and lower in the winter months. The average FAII value reaches the "general "category in eight stations (St. 1, St.4 and St. 8 to St. 13) during the months from May to August, while this value remains at the "poor" or the "very poor" categories even in the summer months. The seasonal variation of FAII was similar to that of Margalef richness index, but was significantly different from that of Shannon-Wiener diversity index. Results of the study suggest that environmental monitoring and remediation of the surf zone of the Yangtze River estuary are necessary for the recruitment of the fish larvae and juveniles.