A phosphorus-fish standing crop relationship for streams?

Abstract

Total fish standing crop data from 79 North American streams located in Wyoming (N = 20), Vermont (N = 19), Florida (N = 15), Iowa (N = 12), Ontario (N = 10), Washington (N = 2), and Missouri (N = 1) were used to test the hypothesis that stream fertility as indexed by total phosphorus concentrations is an important environmental factor influencing fish standing crop. Total fish standing crop among the different geographical regions was not related to differences in latitude, but regional estimates of average fish standing crop were significantly correlated to total phosphorus concentrations (r = 0.79, p < 0.05, n=7). The best-fit empirical regression model for these data was: log (TFSC) = 0.59 log (TP) + 0.82, where TFSC is total fish standing crop (kg/hectare) and TP is total phosphorus concentration (μg/L). The phosphorus-total fish standing crop relationship, however, was weaker when fish standing crop data from individual streams were correlated to total phosphorus concentrations (r = 0.42, p < 0.05, n=79). Locally weighted robust regression analysis (LOWESS) indicated that the phosphorus-total fish standing crop relationship was not linear. Total fish standing crop increased with total phosphorus concentrations throughout the range of reported values, but the increase was much more rapid in streams having total phosphorus concentrations ≤ 15 μg/L. This is consistent with the results of whole-stream fertilization experiments that have demonstrated that phosphorus enrichment enhances autotrophic production in nutrient-deficient streams. The phosphorus-total fish standing crop relationsip also is consistent with the long-held hypothesis that stream fertility is an important factor influencing fish standing crop in North American streams. © 1991 Taylor and Francis Group, LLC.