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<br />of HBC. Nets were often repositioned following net checks if the catch was poor, <br />or if an alternative site was available. Shoreline distance between nets varied <br />due to many logistical considerations; however, most nets were placed between <br />80 to 150 m apart, and an effort is made to roughly space nets evenly. Most nets <br />were tied from the shorelines and set along shore or within a few meters from <br />shore. Some nets were tied from mid-channel boulders and fished further from <br />shore. Each net was checked and emptied of fish daily. <br /> <br />All net locations were recorded as distance (rkm) above the confluence, side of <br />the river (right, left, center), and nets were individually marked on photographic <br />maps supplied by GCMRC. Net locations were entered into a field computer <br />using Arc Map. General habitat characteristics were recorded for the nets, <br />including shoreline habitat, hydraulic unit, substrate, and cover type (Table 2). <br /> <br />Fish <br /> <br />Data collected for native fish captured included: total length (mm; total and fork <br />lengths for HBC), sex (male, female, undetermined), sexual condition (ripe, <br />spent), sexual characteristics (tuberculate, breeding colors), external parasite <br />types and number of external parasites per fish. An exception was made for <br />speckled dace, for which fork length, sex and sexual characteristics were usually <br />not recorded. All fish lengths reported in this document refer to total lengths (Tl). <br />All HBC ~ 150 mm were scanned for a Passive Integrated Transponder (PIT) tag <br />(Biomark, Inc.); and if lacking a tag or containing an older 400 ,kHz PIT tag, were <br />injected with a new 134.2 kHz PIT tag. The two native suckers and carp ~ 150 <br />mm were also scanned for a PIT tag, and if not already tagged, were injected <br />with a PIT tag. Stomach contents of large bodied non-native fish (primarily <br />ictalurids and salmon ids) were examined and recorded in the field. All bullhead <br />were identified to be black bullhead (Ameiurus me/as) in this document based on <br />anal ray counts (i.e., all bullhead checked had 15-19 anal fin rays). <br /> <br />Water Quality <br /> <br />Measured water quality parameters included temperature (OC) and turbidity <br />(nephelometric turbidity units; NTUs), and were collected daily at Salt reach <br />(-10.4 rkm). Turbidity readings were taken daily during the afternoon with a <br />Hach 21 OOP turbidimeter. Provisional discharge (cubic feet per second; cfs) data <br />were obtained from USGS gage station 09402300 located at approximately 1.0 <br />rkm above the confluence in the lCR, and from USGS gage station 0940200 <br />located on the lCR near Cameron, AZ. <br /> <br />Mark-Recapture Analysis and Assumptions <br /> <br />Two mark-recapture efforts (spring and fall) were conducted to estimate the <br />abundance of HBC ~ 150 mm in the lower 13.6km of the lCR. Marking events <br />occurred during the first spring trip (29 March to 9 April) and during the first fall <br />trip (15 to 26 September). Fish ~ 150 mm that had not previously been tagged <br />were injected with an individually numbered and recorded PIT tag. At the end of <br />each marking trip, all unique HBC that had been either tagged or recaptured from <br />14 <br />