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Bear Lake's Unique Whitefish
By Scott Tolentino, DWR Bear Lake Biologist
Bear Lake is a very unique ecosystem that has four endemic (found nowhere
else in the world) species of fish that live in its waters. Two of these fish
are the Bear Lake whitefish and the Bonneville whitefish. These fish were
first described by John O. Snyder in 1919. Since that time limited research
has been conducted on whitefish from Bear Lake. The fact that little is known
about these whitefish has led researchers from the DWR and USU to begin conducting
in-depth studies to better understand their life histories and to develop
a method that can be used to differentiate between the species at all sizes
and seasons of the year.
Knowing more about the biology and status of the populations of these important
endemic species will allow managers to better manipulate stocking rates of
cutthroat trout and lake trout so they do not over-utilize the available forage
base, but allow for optimal utilization of the resource by anglers. The diets
of the whitefish are also being analyzed to identify any diet differences
between the two species.
To set the record straight, both whitefish from Bear Lake are very different
from their river inhabiting cousin, the mountain whitefish. Bear Lake and
Bonneville whitefish both have relatively large mouths compared to the mountain
whitefish. Mountain whitefish, since they live in streams, have developed
a much heavier Y-bone structure, whereas the whitefish from Bear Lake have
Y-bones that are almost nonexistent. Bear Lake and Bonneville whitefish live
and spawn in the lake rather than in a stream and they also have different
diets. The whitefish in Bear Lake usually feed on plankton, ostracods, fish
eggs and other organic debris. They also feed on aquatic insects. What a fish
eats has a lot to do with what it tastes like and both whitefish from Bear
Lake are excellent table fare, compared to the mountain whitefish.
It is speculated that Bear Lake whitefish only grow to a maximum size of
about 10 inches and they are thought to inhabit deeper waters of the lake.
Bear Lake whitefish spawn in mid-February, usually in water more than 30 feet
deep. The bonneville whitefish can grow to over 21 inches in length and weigh
up to five pounds. They spawn in late November through mid-December over rocky
areas in water 2-10 feet deep. When the lake levels are low and rocky areas
are not in the water they will spawn over sandy points.
The major problem fishery managers face in their attempt to manage the whitefish
in Bear Lake is that the two species cannot be readily identified from each
other at sizes less than 10 inches and during the spring and summer when the
fish are not in spawning condition. Unfortunately, this is when the majority
of the fish sampling on the lake takes place. In an effort to find a way to
differentiate the two species at lengths less than 10 inches DWR recently
funded a research project at Utah State University. Researchers collected
and fertilized whitefish eggs from the two different species during their
respective spawning runs during the fall and winter of 1995 an 1996. The eggs
from each species where hatched and are being raised at the USU aquatics laboratory.
Periodic measurements are being taken on the growing fish and will be compared
between these two groups of laboratory-reared fish. Any difference that exist
are noted and are being incorporated into a key which will hopefully be used
to identify the species when collected from the lake. Some of the measurements
being made include: maxillary length, nostril-snout length, head length and
number of scales in the lateral line. Whitefish DNA is also being examined
to determine if differences between the fish can be detected on a cellular
level.
Biologists from DWR have been collecting trend gill net information over
the last 20 years on Bear Lake to monitor populations of the different fish
in the lake. These data have shown some minor population fluctuations in whitefish
catches from 1973 to 1990. However, from 1991-1994 whitefish catch rates were
at all-time highs. Data from 1995-1997 have shown continued near-record catches.
The high catch rates from the mid 1990s prompted the biologists to collect
more detailed information from whitefish caught during the regularly scheduled
gill netting in 1995 and 1996. These fish were measured, weighed and examined
by comparing body measurements and morphological characteristics such as spotting
patterns and head conformations. The data is being examined to determine differences
associated with water depth, location in the lake where the fish were collected,
and time of year they were collected. The observations are being analyzed
to determine if any particular trait, or combination of traits, can be used
to separate the species collected directly from the lake. In addition, diets
of these fish were also assessed. Some of the noteworthy early results in
the current study have shown that whitefish larger than 14 inches utilize
fish as a component of their diet. Bear Lake sculpin, another endemic species,
have been identified in several of the whitefish stomachs.
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