9292

• UCREFRP Catalog Number: 9292
• Author: Trammell, M. and T. Chart.
• Title: Aspinall Unit Studies Nursery Habitat Studies Colorado River 1992--1996.
• USFW Year: 1998.
• USFW - Doc Type: Moab, Utah.
• Copyright Material: NO

. ,
21 :
OVERWINTER SURVIVAL OF CS
AS A FUNCTION OF FALL TL
350
300 -- - -----------•--------------------------------------------- ------------
e 250 -- -------------------------------------------------- ------•--•---•-----..
f- 200 -- ----------------------------------------- --•---------------------------

w 150 - PROJECIID VALIIE FOR'96
----------------------

~ 100 -- -
---------
----•------------------ ------------------------------------------------
a 50 -- -------------- -------._..._.......... r2 = .97 ---------------
0 ~

-50
30 35 40 45 50 55
TOTAL LENGTH {mm)
r figure j . Overwinter
survival (% change in catch rates) of Colorado squawfish as a function of total length (TL) in the
fall, 1992-1996.
Conclusions
Colorado squawfish YOY occupy a variety of low velocity habitats throughout their first year.
The type of habitats occupied during the summer months likely affects growth rates and ultimately
condition of squawfish going into their first winter. Habitat selection in the fall is critical because of
it's influence on overwinter survival ofthe squawfish. As the water cools to below 13° C the physical
characteristics of the habitat required to provide adequate refuge through the winter are of great
importance.
In the fall, squawfish were found in relatively persistent, deep backwater habitats, which usually
were associated with deep scour channels behind large alternate sand bars. It is a matter of
speculation whether the squawfish actually select these habitats, or if the gradual disappearance of
other habitats contributes to the high mortality of the YOY, and sampling merely reveals the survival