Travers Reservoir Fall Walleye Index Netting 2011
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Travers Reservoir Fall Walleye Index Netting (FWIN) Survey 2011 Fisheries Management June, 2012 Travers Reservoir Walleye (Sander vitreus) Index Netting Survey, 2011 Linda Winkel Fisheries Biologist Alberta Sustainable Resource Development Fish and Wildlife Division Calgary, AB June, 2012 Fisheries Management Division Technical Report PERMISSION TO QUOTE This report contains preliminary data and interpretations that may be subject to future revision. Persons who wish to quote from this report, cite it in bibliographies or use it in any other form must first obtain permission from: Executive Director of Fisheries Management, Alberta Fish and Wildlife Division; Program Manager, Fish and Wildlife Management, Prairies Area; or the author. ABSTRACT The 2011 FWIN Survey of Travers Reservoir was conducted from September 23, 2011 to September 26, 2011. Survey objectives included estimating catch per unit effort, as well as various population demographics (including age, growth rate, and reproductive status) in order to assess the status of the Walleye population in this location, and monitor the effects of management. In total 133 Walleye were caught in 2011, resulting in a catch per unit effort of 7.5 Walleye/100 m2/24 h (95% CI: 5.1 – 10.0 Walleye/100 m2/24 h). Walleye fork length averaged 354 mm (range: 129 – 753 mm). Walleye sampled in 2011 reached 500 mm of length by seven years of age. The mean age for this species was 4.7 years. While a diversity of ages (ranging from 0 to 19 years) were present in the sample, fish aged 5 years predominated. Walleye at Travers matured relatively quickly, with males attaining complete maturity by age 6, while females matured completely by age 7. A gonadosomatic index of 1.5% distinguished mature spawning females from immature females. No mature non-spawning female Walleye were observed in 2011. Overall, growth for this species was observed to be “normal”. As a result of these metrices, the Walleye population in Travers Reservoir is classified as vulnerable in 2011. TABLE OF CONTENTS 1.0 INTRODUCION..................................................................................................... 1 2.0 METHODS ............................................................................................................. 1 2.1 Study Area.......................................................................................................... 1 2.2 Survey Methods.................................................................................................. 5 3.0 RESULTS AND DISCUSSION............................................................................. 7 3.1 Water Temperatures and Netting Effort ............................................................. 7 3.2 Catch Results...................................................................................................... 7 3.3 Walleye Catch Per Unit Effort............................................................................ 8 3.4 Fork Length Frequency Distribution .................................................................. 9 3.5 Age Class Frequency Distribution.................................................................... 10 3.6 Age Class Stability............................................................................................ 13 3.7 Age at Maturity................................................................................................. 13 3.8 Length at Age.................................................................................................... 14 3.9 Length at Weight............................................................................................... 16 3.10 Gonadosomatic Index....................................................................................... 17 3.11 Von Bertalanffy Growth Equation.................................................................... 18 4.0 SUMMARY.......................................................................................................... 19 5.0 LITERATURE CITED......................................................................................... 21 6.0 APPENDICES ...................................................................................................... 23 6.1 Catch Composition for FWIN nets, Travers Reservoir 2011 ........................... 23 6.1.1 Catch composition from shallow sets, Travers Reservoir 2011 ............... 23 6.1.2 Catch composition from medium sets, Travers Reservoir 2011............... 24 6.1.3 Catch composition from deep sets, Travers Reservoir 2011 .................... 24 6.2 Northern pike catches by mesh size, Travers Reservoir 2011.......................... 25 6.3 Lake whitefish catches by mesh size, Travers Reservoir 2011 ........................ 26 6.4 Yellow Perch catches by mesh size, Travers Reservoir 2011 .......................... 27 6.5 Statistics of the catch distribution for game fish catches, Travers Reservoir 2011.................................................................................................................... 28 i LIST OF FIGURES Figure 1. Map of Travers Reservoir including 2011 netting locations............................... 4 Figure 2. Walleye catch frequency distribution, Travers Reservoir 2011 ......................... 9 Figure 3. FWIN catches from 32 Alberta lakes from 2002-2011....................................... 9 Figure 4. Walleye fork length frequency distribution, Travers Reservoir 2011.............. 10 Figure 5. Age frequency distribution, Travers Reservoir 2011. ....................................... 11 Figure 6. Age-at-maturity of male Walleye, Travers Reservoir 2011. ............................. 14 Figure 7. Age-at-maturity of female Walleye, Travers Reservoir 2011........................... 14 Figure 8. Length-at-at (logarithmic line of best fit) of Walleye, Travers Reservoir 2011. ......................................................................................................................... 15 Figure 9. Walleye length-at-age compared to 50 cm total length for Travers Reservoir, 2011................................................................................................................. 16 Figure 10. Growth of Walleye (expressed as Length vs. Weight) from Travers Reservoir, 2011................................................................................................................. 17 Figure 11. Walleye Gonadosomatic Index, Travers Reservoir 2011................................ 18 Figure 12. Von Bertalanffy growth curve and parameters fitted to observed fork-length- to-age data for Travers Reservoir, 2011 ......................................................... 19 LIST OF TABLES Table 1. Criteria for classifying status of Walleye fisheries, modified for FWIN analysis ................................................................................................ 12 ii LIST OF APPENDICES 6.1 Catch Composition for FWIN nets, Travers Reservoir 2011 .................................... 23 6.1.1 Catch composition from shallow sets, Travers Reservoir 2011 ........................ 23 6.1.2 Catch composition from medium sets, Travers Reservoir 2011........................ 24 6.1.3 Catch composition from deep sets, Travers Reservoir 2011 ............................. 24 6.2 Northern pike catches by mesh size, Travers Reservoir 2011................................... 25 6.3 Lake whitefish catches by mesh size, Travers Reservoir 2011 ................................. 26 6.4 Yellow Perch catches by mesh size, Travers Reservoir 2011 ................................... 27 6.5 Statistics of the catch distribution for game fish catches, Travers Reservoir 2011. .. 28 iii 1.0 INTRODUCION Walleye (Sander vitreus) are a highly regarded and much sought after sport fish in Alberta. As a result Walleye populations have been subjected to high levels of angling pressure and harvest, particularly in areas in proximity to larger population centers and in locations which are easily accessible. Historically Walleye management was conducted on a provincial basis (i.e. with a single regulation governing all water bodies). This proved ineffective for managing locations which receive high levels of angling pressure, where populations declined or collapsed as a result of overharvest. In response to this issue Alberta Environment and Sustainable Resource Development formulated Alberta’s Walleye Management and Recovery Plan (Berry 1995). Under this plan Walleye populations are individually surveyed to assess a variety of biological criteria and classified as trophy, stable, vulnerable, or collapsed. Management is subsequently tailored to prevent decline and/or restore diminishing populations according to the unique requirements at a given location. The Fall Walleye Index Netting (FWIN) survey conducted at Travers Reservoir in 2011 is the first study of this type conducted at this location. As a result, it will serve as a base line for continued monitoring and management of the Walleye population. 2.0 METHODS 2.1 Study Area Travers Reservoir (TWP14, 15 – R21 – W4M) is located in the mixed grass ecoregion of Alberta, situated between Secondary Highways 522 and 529, approximately 35 km southeast of the town of Vulcan (Mitchell and Prepas 1990). The reservoir was built on the Little Bow River in 1954 to store water for irrigation purposes. While it is part of the Oldman River drainage, the majority of water in Travers Reservoir originates from the Bow River, where it is diverted at Carseland to flow into McGregor Lake. There is additional