Recreational Fishery Stock Assessment 1999/2000 Data Report with Management Recommendations

PHOTO 1. View of Camp Lake from boat launch, August 2000. Click image to view 87K JPG

Introduction

This report presents the results of two stock assessment surveys conducted on Camp Lake, between 1999 and 2000, under a partnership arrangement between the Ministry of Environment, Lands and Parks and the Carrier Sekani Tribal Council (CSTC). Funding for this work was obtained from Fisheries Renewal B.C. through the Upper Fraser-Nechako Fisheries Council. Gary George and Clayton Charlie carried out the fieldwork in 1999; Margo French and Lawrence Ward completed the assessment in 2000. The author conducted the analysis and reporting of the field results. Inquiries pertaining to this report should be directed to the author at the email and address located at the bottom of this page. Click here to view additional photographs of Camp Lake.

Camp Lake is one of five stocked lakes that are managed within Eskers Provincial Park, located 33 km northwest of Prince George. The lake was initially surveyed in 1985, at which time it was determined that the lake was barren of all fish species. Following this survey a joint brook trout and rainbow trout stocking program was recommended to provide a multi-species year-round fishery within easy access of Prince George. Rainbow trout were accordingly released in 1986, followed by brook trout in 1988. The lake has received intermittent releases of both species since that time. All brook trout released since and including 1997 have been sterile (triploid) stock.

The lake was last assessed in 1991 by the B.C. Environment Fisheries Branch. The results of this survey revealed that both rainbow and brook trout were performing well, so no changes were made to the management strategy for the lake. Since eight years had passed since its last assessment, the Ministry assigned Camp Lake a high priority for assessment in 1999.

A preliminary review of the 1999 results revealed that rainbow trout survival was low to non-existent, a marked change from the results obtained in 1991. A repeat of the 1999 net survey was completed in 2000, to ensure that the 1999 results were not an artefact of sampling or due to identification error. The results of both surveys are described below.

FIGURE 1. Location of Camp Lake gill net sets, 1999 & 2000. Click image to view full size bathymetric map (71K).

Methods

A 91.4 m sinking monofilament gill net with experimental mesh sizes was set in Camp Lake on August 10, 1999, and on August 10, 2000, according to the methods specified in the Resource Inventory Committee document Fish Collection Methods and Standards. The 1999 set was deployed at 8:30 AM and retrieved August 11, 1999 at 12:00 PM, for a total soak time of 27.5 hours. The net was set from the northeast shore of the lake, and extended in a SSW orientation (Figure 1). The 2000 set was deployed at 11:30 AM and retrieved the same day at 2:00 PM for a total soak time of 2.5 hours. The exact location of the set was not recorded, however it was placed in the same approximate location as the 1999 set.

All trout collected were sampled for fork length, weight, sex, and maturity. In 2000, stomach contents were also evaluated. Weight was measured to the nearest 5 g in 1999 and to the nearest 10 g in 2000. In 1999 scale samples were collected for ageing, which was performed by Darlene Gillespie of TimeMark Consulting Ltd. (Nanaimo, B.C.). In 2000, rainbow trout scales and brook trout otoliths were collected and analyzed by Birkenhead Scale Analyses (Lone Butte, BC) for analysis.

Results and Discussion

CATCH SUMMARY

The 1999 net catch yielded 27 eastern brook trout (EB), for a catch per unit effort (CPUE) of 0.98 EB per net-hour. See Appendix 1 for the full catch statistics. No rainbow trout or other species were captured.

The 2000 set yielded 10 eastern brook trout and 1 rainbow trout, for a CPUE of 4 EB and 0.4 RB per net-hour. See Appendix 4 for the 2000 EB catch statistics.

FIGURE 2.  Percent maturity class of brook trout sampled in Camp Lake, August 11, 1999.

In 1999, the sex ratio of the sampled brook trout was 17 females : 6 males; 4 could not be classified. Eleven fish were classified as "immature" and 4 could not be classified. Four trout were eggbound, and one was spent (Figure 2), indicating that spawning activity was taking place during the time of survey. The remaining 7 fish were classsified as "mature".

In 2000, a similar ratio of 7 female : 3 male brook trout were captured. One brook trout was classified as "immature", the remaining brook trout catch were all classified as "maturing". These independent assessments confirm the presence of a reproductively viable brook trout population, which are likely the offspring of stock released prior to 1997.

CONDITION

The mean condition of brook trout acquired from Camp Lake in 2000 was higher than the mean condition reported in 1999 (Table 2). The variance in condition factor was lower in 2000 than in 1999 despite the larger sample size obtained from the 1999 survey. High variances in condition were also calculated for brook trout sampled in 1999 in Bow Lake, Butterfly Lake, and Byers Lake , suggesting that mass was not accurately measured by the crew conducting the 1999 surveys. The length-weight relationship reported for Camp Lake brook trout in 2000 is described by the equation W = 0.0002 x L ^2.65 (R²=0.92), indicating that brook trout exhibited a healthy increase in weight relative to their length, but did not exhibit the same degree of increase in weight when compared to brook trout from other regional lakes.

GROWTH

FIGURE 3. Length frequency distribution of brook trout sampled in Camp Lake, comparing 1999 and 2000 results.

Camp Lake brook trout were sampled on August 10 in both 1999 and 2000, however the structures that were collected for ageing purposes differed between the sample events. This may account for the differences in growth noted between 1999 and 2000 (Figure 4). It is generally accepted that scales lead to an underestimate of age in char; if this was the case in 1999 one would expect brook trout growth rates to be even slower in 1999 than what is reported here. The discrepancies between the two years may therefore be due to ageing error, ageing differences between structures, or true differences in growth due to seasonal or population effects. Since otoliths are considered to be more accurate in assessing the age of char, the data obtaining from the 2000 survey should be used to assess brook trout growth in Camp Lake.

Camp Lake brook trout exhibited similar growth rates to brook trout in Bow Lake, and were significantly faster growing than brook trout sampled in Butterfly Lake and Kathie Lake. Recruitment into the recreational fishery occurs by the middle of the third growing season (i.e. age 2+), assuming that anglers target a minimum size of 250 mm fork length.

FIGURE 4. Age vs. length of brook trout sampled in Camp Lake, comparing 1999 and 2000 results.

Current stocking levels do not appear to attenuate growth of Camp Lake brook trout, however the contribution of the stocking program to the recreational fishery, relative to cohort accrual from the naturalized stock, is not presently understood. Camp Lake has received alternate year releases of hatchery fry since 1993, yet 4-year-old Camp Lake trout were, on average, as large as 4-year-old trout captured in Bow Lake, which was only restocked in 1997. This suggests that growth rates are not inhibited by the stocking program.

Management Recommendations

The complete absence of rainbow trout in the 1999 gill net sample, and the presence of only one rainbow trout in 2000, suggests that hatchery-reared rainbow trout are exhibiting poor survival in Camp Lake. Predation by brook trout most likely accounts for this absence, and it is unlikely that modifications to the brook trout stocking program will result in more favorable conditions for rainbow trout survival. It is therefore recommended that rainbow trout yearlings no longer be released into the lake.

Camp Lake brook trout exist as a viable, self-recruiting population. The effect of continued stocking of hatchery-reared brook trout may constrain cohort growth, due to inter-specific competition between naturalized and hatchery recruits, however there is no evidence for this at present. The Province has adopted a policy of stocking exclusively non-reproductive (triploid) brook trout to reduce the risk of escapement and the naturalization of brook trout in the wild. Through continued stocking, it is possible that non-reproductive fish, which develop secondary sexual characteristics but are not capable of spawning, may compete with viable naturalized trout for limited spawning habitat. This may lead to the eventual extirpation of the naturalized stock (see the Butterfly Lake stock assessment report for more details). Continued brook trout stocking is therefore recommended until the outcome a paired lake study in Bow and Butterfly Lakes has been conducted.

Literature Cited.

East, P., and P. Magnan.  1991. Some factors regulating piscivory of brook trout, Salvelinus fontinalis, in lakes of the Laurentian Shield. Can. J. Fish. Aquat. Sci. 48: 1735-1743.

Van Schubert, R.  1991. A Stocking Assessment of Camp Lake. Report prepared for the Fisheries Branch, Ministry of Environment. Prince George.

Philip, D.F. 1985.  A Reconnaissance Survey of Camp Lake. Report prepared for the Fisheries Branch, Ministry of Environment. Prince George.

Appendix 1.
Appendix 2.
Appendix 3.
Appendix 4.

For More Information:

Contact :Ted Zimmerman
Sr. Fisheries Biologist, Omineca sub-Region
Prince George, B.C.
250-565-6852