. Bulletin. Science. 78 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 1. Probable date of breaching of the stream mouth and recording of first lamprey in ladder. No. of days Probable date Date first lamprey Last day lamprey ladder Year sand bar breached in ladder recorded operated 1994 7 February 17 February 9 April1 50 1995 2 January 18 January 18 May 137 1996 20 February 25 February 25 March1 23 1997 24 December2 16 December 18 February1 45 1 Ladder likely closed prior to the end of the upstream migration period. 2 Sand bar breached briefly in October, November, and early December for a few
. Bulletin. Science. 78 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES Table 1. Probable date of breaching of the stream mouth and recording of first lamprey in ladder. No. of days Probable date Date first lamprey Last day lamprey ladder Year sand bar breached in ladder recorded operated 1994 7 February 17 February 9 April1 50 1995 2 January 18 January 18 May 137 1996 20 February 25 February 25 March1 23 1997 24 December2 16 December 18 February1 45 1 Ladder likely closed prior to the end of the upstream migration period. 2 Sand bar breached briefly in October, November, and early December for a few days at a time prior to the 24 December breaching event. total by March 15). On March 16, 142 lamprey were counted in the ladder, the highest single daily total during the study. During the last two weeks of March, 676 adult lamprey were counted. A total of 908 adult Pacific lamprey were ob- served in the ladder during 1994 (Table 2). In 1995, rainfall totaled inches (4 percent exceedance). The sand bar at the mouth of the river likely first breached on 2 January, and suitable streamflow conditions for upstream migration existed in the lower river through 20 May (137 days). Pacific lamprey were observed in the ladder from 18 January through 18 December Year 1 2 3 4 5 6 7 8 9 10 II 12 13 14 |j 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1994 1995 1996 1997 January Year 1 2 3 4 1 < 7 K 9 Id â¢1 ,2 13 ,4 16 17 18 19 20 21 1 22 23 24 25 26 27 1 28 1 29 1 30 1 31 1994 J-L n_ 1996 1997. March Year | 1 | 2 | 3 | 4 | 5 | 6 | 7 8 1 9 10 1 II 12 1 13 1 14 1 15 1 16 1 17 1 18 1 19 1 20 1 21 1 22 1 23 1 24 1 25 1 26 1 27 1 28 1 29 1 30 1 31 1994 â â â â § 1995 ^^^^^^^â-â¢""⢠1996 | 1997 |. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Southern California Academy of Sciences. Los A
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