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Fish & Wildlife Main Page > Lake Stock Assessment Reports > Angly Lake Recreational Fishery Stock Assessment 1999 Final Report Introduction
This report presents the results of a stock assessment of Angly Lake, completed on August 6, 1999 under a partnership arrangement between the Ministry of Environment, Lands and Parks and the Carrier Sekani Tribal Council (CSTC), with funding obtained from Fisheries Renewal B.C. through the Upper Fraser-Nechako Fisheries Council. Gary George and Clayton Charlie of the CSTC delivered the fieldwork component of the assessment; 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. Angly Lake was first surveyed in 1981, at which time it was determined that the lake was barren of all fish species, based on gill net and minnow trap results. The lake was subsequently stocked with rainbow trout in 1982, and has since received yearly releases of 5000 fish of various strains, with the exception of 1997 when only 2500 yearlings were released. In July 1983, an angling survey was performed to evaluate the status of the stocked fishery, however the lake only contained the 1982 cohort at that time. Since this evaluation did not supply the necessary information to determine the long-term performance of the Angly Lake fishery, and since no additional surveys had been performed on Angly Lake, the lake was assigned a high priority for assessment in 1999.
Methods
A 91.4 m sinking monofilament gill net with experimental mesh sizes was set in Angly Lake at 8:18 AM on August 5, 1999, according to the methods specified in the Resource Inventory Committee document Fish Collection Methods and Standards. The net was deployed in an N-S orientation from the south shore (Figure 1), and retrieved on August 6 at 8:30 AM, for a total soak time of 11.8 hours. All trout collected were sampled for fork length, weight, sex,
and maturity. Weight was measured to the nearest 10 g. Scales
were collected for age structure analysis. This analysis was performed
by Darlene Gillespie
of TimeMark Consulting Ltd. (Nanaimo, B.C.).
Results and Discussion
CATCH SUMMARY The net catch yielded 117 rainbow trout (RB), for a catch per unit effort (CPUE) of 9.9 RB per net-hour. Due to time constraints, 50 fish were randomly selected from the catch and sampled. See Appendix 1 for specific fish attribute data. The sex ratio of the sample was 27 females : 23 males. Forty-five fish were classified as "immature", 4 were "maturing", and 1 was "mature". CONDITION The weight of the sampled population increased according to the equation W = 4 x 10-5 x W 2.73 (R2=0.58), where W = weight in grams and L = length in millimeters. While the mean condition of 0.96 for the population is normal for rainbow trout in a monoculture species environment, the variance around the mean is high (as seen in Figure 2), suggesting that the precision applied to weight measurement was low. Similar inaccuracies were reported for other lakes sampled by the crew which conducted this survey. Reasons for this error rate could include either the use of non-calibrated scales, or the imprecise reading and recording of the scale apparatus. LENGTH FREQUENCY DISTRIBUTION The length frequency distribution of the sample (Figure 3) shows that the population was primarily composed of individuals larger than 300mm, and that these fish were age 4 and older. While the ageing data suggests that only four age 3 fish were captured (see Appendix 1), it is likely that some of the smaller fish classified as 4-year-olds were in fact 3 years of age, as a distinct size break between the two cohorts is evident in the length frequency distribution. The low number of 3-year-olds sampled reflects the fact that only 2,500 yearlings were released into the lake in 1997, compared to the usual 5,000. The complete lack of 6-year-olds cannot be expained, since 5,000 fish were released in 1994. This absence may be attributable to ageing error, sampling bias, cohort mortality (i.e. a year-class failure) or to historical angling pressure. GROWTH The mean length of 2-year-old rainbow trout captured in 1983 (328 mm), was considerably greater than the mean reported length of 262 mm for the 3-year-old fish captured in 1999. This result is typical of the difference in trout growth observed between newly stocked lakes, and lakes that have reached an equilibrium between production and growth after several years of stocking. Assuming a minimum acceptable catchable size of 250 mm, Angly Lake rainbow trout currently do not enter into the recreational fishery until they have reached at least 3 years of age. The growth rate of the 3-year-olds sampled may not be indicative of a typical cohort stocked at 5,000 fish per year, since this cohort was stocked at half the density of those stocked in other years. The growth attained after 3 years for cohorts stocked at 5,000 per year is therefore likely to be even less than that reported here.
Management Recommendations The original management objective established for Angly Lake (note to file, 1989) was to create a recreational fishery for 3 lb. rainbow trout (approx.1,300 g). The data obtained from this survey suggests that at present stocking levels, rainbow trout attain a maximum weight of 505 g (approx. 1.1 lb), which is clearly short of the stated management goal. The provincial stocking formula
recommends that Angly Lake be stocked at 9,000 yearlings per
year. While there is no decision record on file to justify the
current stocking rate, it is likely that fisheries managers concluded
that the recommended rate exceeded the lake's capacity to produce
a quality recreational fishery. The rate was accordingly reduced
to 5,000 fish per year. The high rainbow trout CPUE recorded during this survey suggests that the lake has an abundance of trout, whose growth is likely constrained by density dependent factors. In order to improve the mean size-at-age, and in an effort attain the goal of producing 1,300 g trout, it is recommended that the stocking rate be reduced from 5,000 to 3,000 fish per year. This reduction will not ikely curtail angling catch rates to a significant degree, however a survey of angler satisfaction would be beneficial, both before and after the stocking rate change is put into effect.
Literature Cited. Coombes, D. and T. Pendray 1981. Angly Lake Lake Survey
Data. Report repared for the Fisheries Branch, Ministry of Environment.
Prince eorge. 
For More Information: Contact :Ted Zimmerman
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