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Hatching Dates <br />Hatching dates were back- calculated for each Age 0 cohort using formula developed by Muth <br />1990). Standard lengths of Age 0. Gila spp (required to calculate days after hatch) were <br />generated from total lengths collected in the field and lab using the following regression: <br />sL a ~.oa +. ~2os (TTY <br />Days after hatch were calculated for the modal peaks (Table 3) in AGE O length frequency <br />histograms. Spawning activity appeared to be bi-modal in 1992 and particularly in 1993 above <br />the canyon (Figure 3). Hatching (spawning) occurred later in the canyon than upstream, with <br />the exception of 1996. <br />Table 3. Days post hatch and back-calailated hatching dates for YOY chubs collected above and <br />within Westwater Cauyoq Colorado on selected dates in 1992, 1993, 1994 and 1996. Modal <br />peaks are from respective length frequency analyses. <br /> ABOVE CANYON <br /> MODAL PK EST <br />DATE (Std len t~h (mml) DAYS POST HATCH HATCH DATE <br />920721 ~ 18.6 ~ 28.7 920623 <br />920721 29.4 43 920608 <br />930625 14.3 25.9 930531 <br />. 930802 .' 11.4 13.4 - 930720 <br />930802 17.2 ` ' 26 ~ 930707 <br />940712 16.4: 24.8 940717 <br />_. 960725 13.5 ~ i 8.8 960706 <br />WESTWATER CANYON <br /> MODAL PK EST <br />DATE Std length (mm~ DAYS POST HATCH HATCH DATE <br />920721 i 5.7 -' 23.4 920629 <br />920721 20.8 32 920619 <br />930802 14.3 20.3 930713 <br />940712 14.9 22 940620 <br />950905 .24 29.9 - 950805 <br />960725 14.3 20.4 960705 <br />960815 .' 23.6 36 960710 <br />DRAFT <br />.~ ~ 9 <br />