Volume 093 Article 03 FISH HABITAT ASSOCIATIONS OF THE PEND OREILLE RIVER, IDAHO Project F-73-R-15 Subproject VI, Study VII by David H. Bennett and Joseph M. DuPont September 1993 TABLE OF CONTENTS Page ABSTRACT ...............................................................1 INTRODUCTION ...........................................................3 OBJECTIVES .............................................................4 STUDY AREA .............................................................4 OBJECTIVE 1. To identify and evaluate existing physico-chemical and biotic habitat conditions in the Pend Oreille River, Idaho. METHODS ................................................................6 Physico-Chemical Conditions ......................................6 Biotic Conditions ................................................7 RESULTS ................................................................8 Physico-Chemical Conditions ......................................8 Temperature and Dissolved Oxygen ...........................8 Conductivity, Ph, Transparency and Phosphorus ..............8 Water Level Fluctuations .................................. 12 Substrate Composition ..................................... 12 River Velocities .......................................... 15 River Depths .............................................. 15 Biological Components ........................................... 15 Zooplankton ............................................... 15 Benthic Macroinvertebrates ................................ 22 Aquatic Macrophytes ....................................... 28 DISCUSSION ............................................................ 28 Physico-Chemical Conditions ..................................... 28 Temperature and Dissolved Oxygen .......................... 28 Conductivity, Transparency, Ph, and Phosphorous ........... 31 Water Level Fluctuations .................................. 31 Substrate Composition ..................................... 32 River Velocities and Depth ................................ 32 Biological Components ........................................... 33 Zooplankton .............................................. 33 Benthic Invertebrates ..................................... 33 Aquatic Macrophytes ....................................... 34 i TABLE OF CONTENTS Page OBJECTIVE 2. To assess the relative abundance of fishes and determine fish habitat associations as related to drawdown in Pend Oreille River, Idaho. METHODS ...............................................................35 RESULTS ...............................................................37 Species Composition and Relative Abundance ......................37 Habitat Selection ...............................................40 Size Structure ..................................................48 DISCUSSION ............................................................48 OBJECTIVE 3. To assess food habits of fishes in the Pend Oreille River, Idaho. METHODS ...............................................................56 RESULTS ...............................................................57 Food Habits .....................................................57 Diet Overlap ....................................................61 DISCUSSION ............................................................61 OBJECTIVE 4. To determine and compare age, growth, and mortality of selected game fishes in Pend Oreille River, Idaho with other systems of the same latitude. METHODS ...............................................................65 RESULTS ...............................................................65 Growth ..........................................................65 Mortality .......................................................78 ii TABLE OFCONTENTS Page DISCUSSION ........................................................... 78 Growth ......................................................... 78 Mortality ...................................................... 83 OBJECTIVE 5. To determine the effects of drawdown on fish populations in the Pend Oreille River, Idaho. INTRODUCTION ......................................................... 85 METHODS .............................................................. 85 RESULTS .............................................................. 87 Comparison of Fish Communities ................................. 87 Habitat Availability ........................................... 95 DISCUSSION ........................................................... 95 OBJECTIVE 6. To evaluate potential introduction of fishes into the Pend Oreille River, Idaho. METHODS .............................................................. 101 RESULTS .............................................................. 101 Smallmouth Bass ................................................ 101 No r t h e r n Pike ................................................... 105 W h i t e Sturgeon ................................................. 105 C h annel Catfish ............................................... 111 Walleye ........................................................ 111 DISCUSSION ........................................................... 114 Smallmouth Bass ................................................ 114 Northern Pike .................................................. 114 White Sturgeon ................................................. 114 Channel Catfish ................................................ 115 Walleye ........................................................ 115 iii TABLE OF CONTENTS Page GENERAL DISCUSSION ................................................... 116 SUMMARY .............................................................. 116 REFERENCES ........................................................... 118 APPENDIX ...................... ...................................... 123 LIST OF TABLES Table 1. Average conductivity, pH, and secchi readings from each stratum of the Pend Oreille River, Idaho ...................11 Table 2. Zooplankton species observed in the Pend Oreille River, Idaho during 1991 .......................................... 21 Table 3. Average zooplankton densities from collections during July 9-10, 1991 and August 5, 1991 at each strata of the Pend Oreille River. Stratum 4 was not sampled from July 9-10 .................................................. 23 Table 4. Density (No/m2) of benthic invertebrates sampled at each strata of the Pend Oreille River during July 9-10 and August 18-20, 1991. Stratum 4 was not sampled . 26 Table 5. Biomass (g/m2) of benthic invertebrates sampled at each strata of the Pend Oreille River during July 9-10 and August 18-20, 1991. Stratum 4 was not sampled . 27 Table 6. Average biomass (g/m2) of aquatic macrophytes collected from sloughs and along the main river channel during August 1, 1992 ............................................. 29 Table 7. Sampling dates and drawdown stages in the Pend Oreille River, Idaho ............................................... 36 Table 8. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during 1991 and 1992 ................................................... 38 Table 9. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during lowpool (March 1992). No sampling occurred in Stratum 4 . 39 iv LIST OF TABLES (Cont.) Page Table 10. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during refill (mid-May to mid-June) 1991 and 1992. Strata 4 and 5 were not sampled during 1991 ...............................41 Table 11. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during early highpool (July) 1991 and 1992 ............................... 42 Table 12. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during late highpool (August) 1991 and 1992 ............................. 43 Table 13. Number of fishes sampled by all gear types within each stratum from the Pend Oreille River, Idaho during drawdown (October) 1991 and 1992 ...........................44 Table 14. Observed (obs), expected (exp), and the magnitude of difference (mag) between the observed and expected gill net catches for yellow perch, peamouth, and northern squawfish sampled during lowpool, refill, early highpool, late highpool, and drawdown, 1991 and 1992 .................45 Table 15. Observed (obs), expected (exp), and the magnitude of difference (mag) between the observed and expected gill net catches for largemouth bass, black crappie, rainbow trout, cutthroat trout, and brown trout sampled during the cooler period (drawdown, lowpool, and refill) and warmer period (early and late highpool) during 1991 and 1992 ...................................................47 Table 16. Stomach contents by weight of yellow perch >200 mm (n=162) and <200 mm (n=140) collected during July and August, 1991 from Pend Oreille River, Idaho ................58 Table 17. Stomach contents of northern squawfish >200 mm (n=63) and <200 mm (n=169) and peamouth (all sizes; n=5) collected during July and August, 1991 from Pend Oreille River, Idaho .......................................59 Table 18. Stomach contents by weight of largemouth bass 100-200 mm (n=25) and >200 mm (n=8) and black crappie <200 mm (n=33) and >200 mm (n=9) collected during July and August, 1991 from Pend Oreille River, Idaho ................60 v LIST OF TABLES