Kootenay Lake Angler Creel Survey
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KOOTENAY LAKE ANGLER CREEL SURVEY 2011 KOOTENAY LAKE ANGLER CREEL SURVEY 2011 Prepared for: Fish and Wildlife Compensation Program – Columbia Basin 103-333 Victoria St. Nelson, BC Prepared by: H. Andrusak, RPBio & Greg Andrusak, RPBio September 2012 Redfish Consulting Ltd. 5244 Highway 3A Nelson, BC V1L 6N6 Cover Photo: ‘‘Release of a 800 mm (7.6 kg) male Gerrard rainbow trout on Kootenay Lake by Kerry Reed.’ Photograph taken on the 15th of June 2011 by Greg Andrusak. The Fish and Wildlife Compensation Program is a joint initiative between BC Hydro, the BC Ministry of Ministry of Forests, Lands and Natural Resource Operations (MFLNRO) and Fisheries & Oceans Canada (DFO) to conserve and enhance fish and wildlife populations affected by the construction of BC Hydro dams in Canada's portion of the Columbia Basin. Suggested Citation: H. Andrusak and G. F. Andrusak. 2012. Kootenay Lake Angler Creel Survey 2011. Report prepared for Fish and Wildlife Compensation Program – Columbia Basin(Nelson, BC) by Redfish Consulting Ltd. (Nelson, BC). FWCP Report 59 pp. + app. Kootenay Lake Angler Creel Survey-2011 EXECUTIVE SUMMARY The primary objective of the access point angler survey conducted on Kootenay Lake in 2011 was to provide updated estimates of angler effort, catch and harvest. Prior to the 2011 survey, analysis by Simon Fraser University expertise of large lake creel census methods led to the conclusion that stationary access point interviews for angler catch and effort combined with aerial boat counts were the best approach for such a large lake. Interviews at sampled access points provided only partial information on catch and effort. Non-randomized flights over the length of the lake during peak daily angling activity provided information on the fraction of total effort interviewed by comparing the total number of active fishing boats to the number of interviewed boats active during the flight times. This fraction was applied to the access point data to estimate total daily effort and catch. Survey dates and data collected were stratified by month and daytype (weekend/weekday). The monthly estimates of length of day fishing, species catch and harvest were then expanded using correction factors based on the ratio of access boats sampled to total boats counted by air from a total of 42 flights conducted throughout the year. The aerial based boat counts provided an effective method for estimating total effort. A total estimate of 201,434 (SE ±12,981) rod hours were spent in 2011 to catch an estimated 15,995 (SE± 1,408) rainbow trout, 6,133 (455) bull trout and 5,377 (SE ±814) kokanee. This equates into a total of 40,416 (SE ± 2,443) angler days fished on the lake during 2011. Release rate for rainbow trout was a very high at 61.5% whereas it was only 40% for bull trout and only 21.7% for kokanee thus estimated annual harvest was 6149 (SE± 584) rainbows, 3,655 (SE ±258) bull trout and 4209 (SE± 574) kokanee. Based on angler responses who fished only for one species most of the effort was directed primarily at the Gerrard rainbow trout population with 38,440(SE 6291±) rod hours (79%) compared to 7,482 (SE 3687±) rod hours (15%) for bull trout and only 2,756 (SE 611±) rod hours (6%) for kokanee. This data matches closely with the KLRT mail-out survey (that does not include kokanee effort) that indicates most anglers (average 85%, 1990-2010) fish for rainbow trout. The harvested large size rainbow trout and bull trout were in excellent condition (rainbow K = >1.27) and bull trout (K=1.08) but condition (K) was not considered a good indicator of success of lake fertilization owing to uneven seasonal sampling and lack of comparable pre-fertilization data. The Gerrard rainbow trout spawner counts, kokanee spawner counts, in-lake kokanee biomass estimates, rainbow trout growth, and trophic level production measurements all combined are considered to be far better indicators of success of lake fertilization. i REDFISH CONSULTING LTD. Kootenay Lake Angler Creel Survey-2011 Comparisons are made between the 2011 Kootenay Lake sport fishery statistics and those available from the 1970s and 1980s. Although the survey methods differ with the older data derived from a roving survey design there is reason to believe that estimates of effort, catch and harvest of rainbow trout and bull trout are much higher today than in the 1970s or 1980s. The mean rainbow effort, catch and CPUE (excluding kokanee effort) for 1973-1986 was 114,170 rod hours, catch of 3,575 and CPUE of 0.03, much lower than the 2011 estimates of 198,678 rod hours, 15,995 catch and 0.08 CPUE. The mean bull trout effort, catch and CPUE (excluding kokanee effort) for 1973-1986 was 114,170 rod hours, catch of 1,100 and CPUE of 0.01, much lower than the 2011 estimates of 198,678 rod hours, 6,133 catch and 0.03 CPUE. Despite the differences in survey methods the most comparable data is CPUE and it is quite convincing that the calculated 2011 CPUE rates for rainbow trout and bull trout (0.08 and 0.03 per rod hours respectively) are both substantially higher than any previous year on record. This increase, at least for the Gerrard rainbow trout population, is supported by the impressive increase in Gerrard spawner numbers during the late 2000s with peak counts nearly 1000 compared to only 200-300 in the 1970s and 1980s. The 2011 data also indicates that the larger, older rainbow trout are the fish of greatest interest to most anglers with more than half (54%) of the estimated harvest >50 cm. Mean weight of these larger trout in 2011 was considerably lower than earlier years data but dissimilar sampling procedures may account for the difference. Going forward, a closer examination of mean weights is warranted. Kootenay Lake fisheries are pre-eminent amongst similar BC large lake fisheries. Although few contemporary surveys exist to make direct comparisons data from Shuswap Lake and Arrow Lakes Reservoir (ALR) are somewhat comparable. In both cases the rainbow trout fisheries target much smaller size trout and angler effort is lower. The ALR rainbow trout fishery has declined in recent years - at least for the largest size trout whereas all indications are the Kootenay Lake rainbow trout spawner numbers and catch are tracking positively. A distinct feature of the Kootenay lake fishery is that effort is year round with success rates and the largest size trout caught during the non-summer months. The ALR fishery tends to be more of a summer time fishery with less effort during the winter months. The 2011 Kootenay Lake kokanee fishery did not generate much attention with effort at or near the lowest on record regardless of method of allocating the 2011 effort. The mean directed effort for kokanee, catch and CPUE for 1973-1986 was 25,379 rod hours, catch of 32,767 and CPUE of 1.29. These estimates are at or higher than the range of 2011 estimates of 2,755 rod-hours for anglers seeking kokanee only (26,068 rod hours for anglers including kokanee as a species sought), 5,377 catch (harvest 4,209) and 0.42-1.26 CPUE dependent upon whether the effort was directed at kokanee only or at kokanee and other species. Total catch has greatly declined from the high levels of ~100,000 in the ii REDFISH CONSULTING LTD. Kootenay Lake Angler Creel Survey-2011 1980s despite high in-lake abundance and no appreciable change in size over time. The ALR kokanee fishery has historically been lower than Kootenay Lake in terms of effort and catch but the CPUEs have been quite similar exceeding 1 fish per rod hour. However the most recent data for the ALR indicates kokanee CPUE has declined to < 0.8/rod hours. Comparison of the 2011 survey results with previous KLRT survey results was difficult given the availability of only one year’s access point data. It is believed the KLRT effort estimates are positively biased but still close to the 2011 estimate. Data analysis suggests the most comparable statistics between the two surveys are the catch and harvest of rainbow trout > 50 cm. Increased catch rate and harvest of large size rainbow trout and bull trout assumed to be piscivores bodes well for Kootenay Lake anglers. These metrics as well as others reported in numerous reports such as increased kokanee abundance and Gerrard rainbow trout spawner numbers indicate a positive response of the upper trophic levels to lake fertilization. Moving forward, the Kootenay Lake fisheries warrant close monitoring owing to its economic importance as well as an effective means of monitoring the status of the individual sport fish species. Angler surveys that includes biological data combined with long term monitoring of trophic level responses to lake fertilization provide a powerful measure of success (or failure) of nutrient additions. A series of recommendations for future angler surveys are made including a repeat in 2013 of the level of effort expended for the 2011 survey. However, it is recognized that the level of future funding may not be available therefore survey scenarios are suggested that include reduced interview effort, reduced lake area covered and variation of aerial boat count surveys. A more comprehensive analysis of options to reduce cost became available during time of writing this report. iii REDFISH CONSULTING LTD. Kootenay Lake Angler Creel Survey-2011 ACKNOWLEDGEMENTS This report could not have been written without the outstanding statistical analysis conducted by Dr. Carl Schwarz at Simon Fraser University. His work provides scientifically defensible analysis of the multitude of statistics that have been generated from the 2011 survey data.