My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
7985
CWCB
>
UCREFRP
>
Copyright
>
7985
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
7/14/2009 5:01:46 PM
Creation date
5/20/2009 1:36:12 PM
Metadata
Fields
Template:
UCREFRP
UCREFRP Catalog Number
7985
Author
Trammell, M. A., E. P. Bergersen and P. J. Martinez
Title
Evaluation of an Introduction of Colorado Squawfish in a Main Stem Impoundment on the White River, Colorado
USFW Year
1993
USFW - Doc Type
The Southwestern Naturalist
Copyright Material
YES
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
8
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />December 1993 <br /> <br />Trammell el al.-Colorado squawfish <br /> <br />367 <br /> <br /> <br />several possible explanations including any or a <br />combination of flow regime, movement patterns, <br />mortality and sampling effectiveness. . <br />The short period of escapement, or "pulse" of <br />downstream movement of the majority of the Col- <br />orado squawfish was associated with high spring <br />flows following stocking. Clark (1942), Louder <br />(1958), Elser (1960) and Powell and Spencer <br />(1979) all found high fish emigrations over spill- <br />ways related to season rather than magnitude of <br />discharge, with most migration occurring in <br />spring. Lewis et al. (1968) found such movements <br />related to heavy rainfall events in the spring, with <br />none occurring after heavy rainfall in July. <br />The spillway at Kenney Reservoir offers no <br />deterrents or barriers to fish emigration. Colorado <br />squawfish stocked during the spring high flows <br />in 1988, 1989, and 1990 were collected in rela- <br />tively large numbers downstream from the dam. <br />A single Colorado squawfish from late summer <br />stockings in 1990 was captured below the dam <br />in a drift net two days after stocking. None were <br />collected in subsequent seining downstream from <br />the dam (Table 3). Our data suggest that Colo- <br />rado squawfish exit the reservoir regardless of the <br />time of year when stocked, however, it appears <br />that lesser numbers exit the reservoir during pe- <br />riods of lower flows. <br />Catch-per-unit-effort, (CPUE) declined <br />throughout the summer sampling period and ap- <br />proached zero (Table 3). When sampling was <br />resumed the following spring, CPUE for the pre- <br />vious year-class of squawfish was found to be at <br />the same level as that in the fall, one or two fish <br />per several hundred square meters seined. The <br />CPUE then resumed a downward trend until no <br />fish were collected at the end of their second sum- <br />mer. It is a matter of speculation whether these <br />fish are reentering the backwaters at high water <br />after spending the winter months in the main <br />channel, or have recently exited the reservoir dur- <br />ing spring runoff. The recent exit theory supports <br />the "pulse" hypothesis proposed above. <br />Emigration and resultant downstream move- <br />ment of Colorado squaw fish may represent a ge- <br />netic and age-related tendency. Young Colorado <br />squaw fish tend to move or drift downstream after <br />"swim-up" to more suitable nursery habitat <br />(Tyus, 1991). Juveniles have generally only been <br />found downstream of identified spawning areas. <br />No spawning sites for Colorado squawfish have <br />been identified and no wild juveniles less than <br />267 mm long have been collected in the White <br /> <br /> <br />"~l . <br /> <br />River (Chart and Bergersen, 1992). Apparently <br />the White River is not highly suitable habitat for <br />young Colorado squawfish; this may be one ex- <br />planation for the downstream dispersal and prob- <br />able mortality of the stocked fish. <br />The small size of the squawfish at stocking <br />could have contributed to increased mortality. Al- <br />though no evidence of predation on squawfish <br />was collected, potential piscid and avian predators <br />were present in the White River and Kenney <br />Reservoir, including black crappie, roundtail chub, <br />channel catfish and brown trout. The effect of <br />predation on the stocked squawfish is unknown, <br />but is likely to be significant. A rapidly expanding <br />population of black crappie, whose numbers in- <br />creased from 0.4% of the community in 1988 to <br />3.8% in 1989 and 17% in 1990 could seriously <br />affect future stocking of fingerling Colorado <br />squawfish. <br />Although most of the recaptured Colorado <br />squaw fish were found in the reservoir or down- <br />stream, the few that were captured above the <br />reservoir in 1990 raise some interesting questions <br />because upstream movement is unusual in juve- <br />niles. That the stocked Colorado squawfish were <br />able to.swim upstream against a current and even <br />negotiate small rapids at sizes less than 100 mm <br />are both important findings of the present study <br />because previous data had suggested that juve- <br />niles do not normally move upstream (Tyus, <br />1991). The behavior of Colorado squaw fish <br />changes with growth and sexual maturity. They <br />become more mobile, particularly during the <br />spawning season when they undertake long <br />spawning migrations (Tyus and McAda, 1984). <br />Such behavior would tend to make any Colorado <br />squawfish remaining in the reservoir more likely <br />to emigrate as they reach maturity. <br />The telemetry portion of the study explored <br />behavioral differences between wild and hatch- <br />ery-raised adult Colorado squawfish; specifically <br />to determine if fish raised to maturity in a hatch- <br />ery would exhibit less tendency to make a spawn- <br />ing migration, or would have greater tendency to <br />remain in the reservoir particularly during high <br />movement periods in June and July. Although <br />sample sizes were too small for statistical com- <br />parisons, our results indicate no greater tendency <br />of hatchery reared fish to remain in the reservoir. <br />A hatchery fish was the first to be located below <br />the dam, and descended many kilometers before <br />returning. Another moved upstream into the river <br />and back shortly before death. Two of the three <br /> <br />)- <br /> <br />~J.;lU\.~\$_ <br /> <br /> <br />: ~~~""~~~Q"i7~~~~..~,~..,~.'~ri""-.':":"" <br />
The URL can be used to link to this page
Your browser does not support the video tag.