Lake Newell Fall Walleye Index Netting (FWIN) Survey 2011 Fisheries Management November, 2011 Lake Newell Fall Walleye (Sander vitreus) Index Netting Survey, 2011 Linda Winkel Fisheries Biologist Alberta Sustainable Resource Development Fish and Wildlife Division Calgary, AB November, 2011 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 Lake Newell was conducted from September 26 to 27, 2011. Survey objectives included estimating catch per unit effort, as well as various population demographics (age, growth rate, reproductive status) in order to monitor the effects of management to ensure the stability and sustainability of the Walleye population at this location. In total 109 Walleye were caught in 2011, resulting in a catch per unit effort of 10.4 Walleye/100 m2/24 h (95% CI: 7.2 – 14.5 Walleye/100 m2/24 h). Walleye fork length averaged 467 mm (range: 112 – 720 mm). Walleye sampled during the 2011 FWIN reached 500 mm in length by five years of age, and mean age for this species was 5.5 years. While a diversity of ages (ranging from 0 to 14 years) were sampled, fish aged 8 years predominated. Males matured completely by age 3, while females were completely mature after 8 years of age. A gonadosomatic index exceeding 0.5% distinguished mature spawning females from immature and non-spawning individuals. Overall growth for Walleye can be characterized as “normal” in 2011. In response to these metrics, the Walleye population in Lake Newell can be classified as vulnerable in 2011. TABLE OF CONTENTS 1.0 INTRODUCTION ............................................................................................ 1 2.0 METHODS ....................................................................................................... 1 2.1 Study Area .................................................................................................... 1 2.2 Survey Methods ............................................................................................ 4 3.0 RESULTS AND DISCUSSION....................................................................... 6 3.1 Water Temperatures and Netting Effort ....................................................... 6 3.2 Catch Results ................................................................................................ 6 3.3 Walleye Catch Per Unit Effort...................................................................... 7 3.4 Fork Length Frequency Distribution ............................................................ 9 3.5 Age Class Frequency Distribution................................................................ 9 3.6 Age Class Stability...................................................................................... 12 3.7 Age at Maturity........................................................................................... 12 3.8 Length at Age.............................................................................................. 13 3.9 Length at Weight......................................................................................... 15 3.10 Gonadosomatic Index ................................................................................. 15 3.11 Von Bertalanffy Growth Equation.............................................................. 16 4.0 SUMMARY.................................................................................................... 17 5.0 LITERATURE CITED ................................................................................... 19 6.0 APPENDICES ................................................................................................ 21 6.1.1 Catch composition from shallow sets, Lake Newell 2011.................. 21 6.1.2 Catch composition from medium sets, Lake Newell 2011................. 21 6.2 Walleye catches by mesh size, Lake Newell 2011. .................................... 22 6.3 Lake Whitefish catches by mesh size, Lake Newell 2011.......................... 22 6.4 Northern Pike catches by mesh size, Lake Newell 2011............................ 23 6.5 White Sucker catches by mesh size, Lake Newell 2011............................. 23 i LIST OF FIGURES Figure 1. Map of Lake Newell, including 2011................................................................. 3 Figure 2. Walleye catch frequency distribution, Lake Newell 2011 (CUE = 10.3 Walleye/100m2/24h (95% CI: 7.2 – 14.5 Walleye/100m2/24h)). ........................ 8 Figure 3. FWIN catches from 35 Alberta lakes from 2002-2011....................................... 8 Figure 4. Walleye fork length frequency distribution, Lake Newell 2011. ....................... 9 Figure 5. Age frequency distribution, Lake Newell 2011. ............................................... 10 Figure 6. Age-at-maturity of male Walleye, Lake Newell 2011. ..................................... 12 Figure 7. Age-at-maturity of female Walleye, Lake Newell 2011. .................................. 13 Figure 8. Length-at-at (exponential line of best fit) of Walleye, Lake Newell 2011. ...... 14 Figure 9. Walleye length-at-age compared to 50 cm total length for Lake Newell, 2011.................................................................................................................... 14 Figure 10. Growth of Walleye (expressed as Length vs. Weight) from Lake Newell, 2011.................................................................................................................... 15 Figure 11. Walleye Gonadosomatic Index, Lake Newell 2011........................................ 16 Figure 12. Von Bertalanffy growth curve and parameters fitted to observed fork- length-to-age data for Lake Newell, 2011. ........................................................ 17 LIST OF TABLES Table 1. Criteria for classifying status of Walleye fisheries, modified for FWIN analysis............................................................................................................... 11 ii LIST OF APPENDICES 6.1 Catch Composition for FWIN nets, Lake Newell 2011....................................... 21 6.1.1 Catch composition from shallow sets, Lake Newell 2011................................ 21 6.1.2 Catch composition from medium sets, Lake Newell 2011............................... 21 6.2 Walleye catches by mesh size, Lake Newell 2011. ............................................. 22 6.3 Lake Whitefish catches by mesh size, Lake Newell 2011................................... 22 6.4 Northern Pike catches by mesh size, Lake Newell 2011..................................... 23 6.5 White Sucker catches by mesh size, Lake Newell 2011...................................... 23 6.6 Statistics of the catch distribution for game fish catches, Lake Newell 2011. .... 24 iii 1.0 INTRODUCTION Walleye (Sander vitreus) are considered a highly desirable sport fish in Alberta, and are consequently much sought after. As a result Walleye populations have been subjected to high levels of angling pressure and harvest, particularly in easily accessible locations in proximity to larger population centers. Historically, management of this species was conducted on a provincial basis, which proved ineffective for managing locations with high levels of angling pressure. Walleye populations in a variety of locations declined or collapsed as a result of overharvest. Alberta Sustainable Resource Development formulated Alberta’s Walleye Management and Recovery Plan (Berry 1995) in response. Under this plan Walleye populations are surveyed to assess a variety of biological criteria and classified as trophy, stable, vulnerable, or collapsed. Management is subsequently modified to prevent decline and/or restore diminishing populations according to the individual requirements at a given location. The Fall Walleye Index Netting (FWIN) survey conducted at Lake Newell in 2011 continued monitoring at this location to ensure effective management of the local Walleye population. It follows up on similar surveys conducted since 2005. 2.0 METHODS 2.1 Study Area Situated approximately 200 km southeast of Calgary and 8 km south of Brooks, Lake Newell (TWP16-R14-W4M to TWP18-R15-W4M) is located in the shortgrass prairie region of Alberta (Mitchell and Prepas 1990). Constructed for offstream storage, the reservoir is owned and operated by the Eastern Irrigation District. Lake Newell is one of Alberta’s largest reservoirs, with a mean depth of 6.4m, a maximum depth of 16.8 m, and a surface area of 6307 ha. The mean annual drawdown is 1.4m, and water has a residence time of 1.4 years (Mitchell and Prepas 1990). Water is diverted into the north end of Lake Newell from Bassano Dam via the Main East Branch Canal, and into the Southwest corner from Kitsum Reservoir via the Bow Slope 1 Canal. Lake Newell has two exits; the Main Bantry Canal in the north east supplies the North and West Bantry Canal systems, while the outlet at the south east end supplies Rolling Hills Reservoir (Mitchell and Prepas 1990). In addition to irrigation, Lake Newell also provides access to a number of popular recreational activities such as angling, wind surfing, and bird watching. The majority of access to this location occurs