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.