Report Number: 12812
Permit Number: CRLA1997ASPG
Date Received: Jan 01, 1998
Reporting Year:
1997
Principal Investigator:
Mark Buktenica,
National Park Service,
Crater Lake, Oregon
Park-assigned Study Id. # CRLA1997ASPG
Permit Expiration
Date:
Jan 01, 1999
Permit Start Date:
Jan 01, 1998
Study Starting
Date:
Jan 01, 1997
Study Ending Date:
Jan 01, 1997
Study
Status:
Completed
Activity Type:
Other
Subject/Discipline:
Ecology (Aquatic, Marine, Terrestrial)
Objectives:
Develop a better understanding of the
ecological role(s) of introduced fish in
Crater Lake.
Findings and Status:
Fish distribution was evaluated in 1996 and
1997 with sonar (BioSonics DT4000 and DT6000
respectively). The lake was divided into
nearshore (0 to 100 m depth) and offshore (>
100 m depth) zones for purposes of the
acoustic survey. In 1996 the fish population
was estimated to be 56,500 with a density of
10.37 fish/ha. Density was highest
nearshore, day and night; however, density
offshore more than doubled during the day
(4.0 to 8.9 fish/ha), while density
nearshore decreased (34.4 to 21.8 fish/ha).
Fish were detected deeper during the day
(61.0% below 60 m) than at night (0.5% below
60 m). In 1997 several fish were detected
below 120 m in depth. The maximum depth of
detection was 146 m. The distribution of
fish appeared to be most closely related to
fish food habits. A multivariate analysis of
variance indicated that kokanee salmon and
rainbow trout food habits, collected over a
twelve year period, were different (f =
51.12 with 31, 1222 d.f.). Kokanee salmon
fed on fewer taxonomic food groups than
rainbow trout. Kokanee fed on a large number
of food items (average number of food items
per stomach = 1074) of small body size (1.72
mg dry weight), primarily from the mid-water
column. Rainbow trout fed on taxa taken from
the lake bottom and the lake surface, with
an average of 180 food items per stomach
that averaged 11.06 mg dry weight.
For
this study, were one or more specimens collected and
removed from the park but not destroyed during
analyses?
No
Funding provided
this reporting year by NPS:
4000
Funding provided
this reporting year by other sources:
0
Full name of
college or university:
n/a
Annual funding
provided by NPS to university or college this
reporting year: 0
