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.....--- --...... .....---..-....-.. .....--.--_..._.. .................. ............... . I I I I I I I I I I I I I I I I I I I 3.5 Hatching Dates of YOY Colorado Squawflsh In order to gain a better understanding of the environmental factors that influenced hatching success and survival of yay Colorado squawfish, hatching dates were back-calculated for larvae and yay using the length/age regressions developed by Haynes at a1. (1985). The relationships are as follows: REGRESSION A: For fish with a total length (L) of less than 22 mm: Age = -76.7105 + 17.4949L - 1.055L2 + 0.0221L3 (r' = 0.99) REGRESSION B: For fish with a total length (L) of 22.0 to 47.0 mm: Age = -26.6421 + 2. n98L (~ = 0.99) . .... ...-.............. . - - . - -. - - - - . . - . . - . . . . . . ......--.... -................. .,-...-....'.',....-.-............ .. ......... . ................. ..................,._......-.................................. .........-....................... .. ........... ................. ........--..................... ...---.................,........ .,...........~................. ............. ......~.......... ........... ........ . ..q-- ."........ ... ...... ..................... ..................... . ...................... . . . . . . . . . . . . . . . . . . . . . . ...................... ..............-.. .........,....-..... .....,. .--.--.-..-.. '........--...-..-...--....-...-...-----...-. -. ...............-.-......-,....... -~-..--.----... ...........-....... .......-.-....-. .-...-.-. -, ....................-........-.... ..-..... .-.. ............................-.........- ...--... ............... -.... ................. -.... -. .. ..............-.....................--..-.---.... ............ ........ ...---.........--.-...--. ..............-....-................-~...-..._. .- . ...........-........-- .-.-...... . . .. . ... ...... ..........---...... .... ............ ..........-.......... .... ... -....... ...-.-........... . .......-........ ...... ........... .. . . . .. - . . . . , ,':':':':"':"':':':-:".:.:.:.:.:.;.;-:::::;:.::::;.:.:::.:.:::::::::::.:::;:.:::::::;:::::::.;::::::;:::::::;:::.::::::..... .......-.....-_.....................'......:-:.;.;.:.:.:-:........................;....:.:.:.:.:...:.:.:.:.:.:.:.:.:.:...............:.:.:.:.:.:.:.:.:.:.:.:.:.;.:.:.:.'. ....... .......... ...... ...... ......... .......-.-..........................................,.............................u.... .......---............................................................................. .....----............................................................................. . ....-.-...............:.;.:::::;:::::::::::::::::::::::::::::;:;::::;:::;;;;:;:::::::::::::::::::::::::::::::;::::::::::::::::::::::::::::::::::::::::::::::::;;:::::: .. .....-......................................."..-..-........ ....." --- ------.. . . .... .....,..-----...~...,...-._-....'.....--.-...... .......,-..---.--- - ........-.-.--...- -."--... ........ ......-...-----....-..... ----..- - -. ............,..-.-.----.,..,...-~.--....-....~--. ..............'-..........-....-.. ..--...- . --. . . . . . . . - . . . . . . . . . . . . . . . . . . . . . . .. ... - - . . . . . . . . . . .......-.-.....'-.-...-...............-......-. ..............--...... .....-.-............-.. ..._.............-..........................-.-. ... .. .........................-.-....-.....-. . ..-.....".-.....---.-- ..... ..... .... ..--..- ..---. ... ................--.. -----. ..... ..--.......-......-.----. . . - . . . . . . . . . . . . . . . . . . . . . - - . . - - . . .._",,---....................-.. ..--.-...................--.. ...--,-...-.... ..........----.. ....---.-.-..-.................-.... .-..--............ ......-....-. ..-.-......... ...............-.. .-................ .,...... -..-.. .--........,.. .... .-..-.....-. .......-..............'--....-...-. .............. .-.......... . . - . . . . - . . . . . .. ..... - . . . . ...-................. ........-....-..... ...............................,.....-...-...................-......--......................... i4;D::!,i:i!SESUU.?.....::.::.. .............. - -... ....................-. ---....,..-... ...................-......'--..-.-....--.,.---...-...-'-.'.-.'.-.-.. . . . - . . . . . . . . .. .... ........... - . ...............-...-.-.....,.-..-. ............ .......... -.... .................. .........-....... .................................. 4.1 Summary of Fish Composition A total of 31 species of fish, representing 11 families, were captured in the study area from 1985 to 1988 (Table 4). Of the 31 species, 23 were non-native Ontroduced), and only 8 were native to the Colorado River System (Tyus et a1. 1982). The non-native species made up 95% of the catch, while the natives made up only 5%. Of the 8 natives, 6 were endemic (Colorado squawfish, humpback chub, bonytail, razorback sucker, roundtail chub, and flannel mouth sucker), and 2 were native but not endemic (bluehead sucker and speckled dace). The three endangered species (Colorado squawfish, humpback chub and bonytaiO made up only 3% of the fish captured during these investigations. A discussion of each of the 31 species is presented in Appendix B. When the numbers of fish caught in all 4 years and by all gears were summed, fIVe species accounted for 90% of the catch (Figure 11). These included the red shiner, sand shiner, channel catfish, carp, and fathead minnow, all introduced species. Red shiners alone accounted for nearly 50% of the catch, sand shiners for 21 %, and channel catfish, carp and fathead minnows for 9, 6, and 5%, respectively. NATIVE AND ENDEMIC SPECIES- 5% / (Endangered Specles- 3%) KEY: RS- Red Shiner SS- Sand Shiner CC- Channel Catfish CP- Carp FH- Fathead Minnow Figure 11. Fish species composition In the Cataract Canyon Study Area, 1985.1988. 22