An Assessment of Walleye Populations in Buffalo, Gods, and Graham Lakes 2009
Shane Wood and Clayton James
Walleye (Sander vitreus) populations throughout Alberta are faced with high angling pressure, late‐maturity, and slow‐growth rates, resulting in many populations being susceptible to overexploitation. In 1995, Alberta Sustainable Resource Development (ASRD) implemented the Alberta Walleye Management and Recovery Plan (AWMRP) to facilitate the protection and recovery of Walleye fisheries. As part of the AWMRP, the Alberta Conservation Association (ACA) conducted gill net surveys in Buffalo, Gods, and Graham lakes from 21 to 29 September 2009 to examine population structure and growth characteristics of Walleye.
Despite anecdotal information that Walleye were present in Buffalo Lake, this survey failed to catch any Walleye from this lake.
Gods Lake exhibited a Walleye CUE (catch‐per‐unit‐effort) of 8.7 fish/100 m2/24 h. Length distribution of Walleye from Gods Lake was broad and ranged from 104 to 651 mm FL, with a strong peak in the 500–625 mm size ranges. Similarly, the age‐class distribution was broad, ranging from YOY (young‐of–the‐year) to age 19 with a mean age of 9.8 y. The population is composed mainly of Walleye in the 12 y age‐class, which made up 48% of the total Walleye captured. Based on the AWMRP criteria, the Walleye population in Gods Lake exhibited a wide (>8 age‐classes) and very stable (mean age >9 y) age‐class distribution. However, the poor representation of fish less than age 12 suggests poor recruitment into the fishery. Furthermore, the high catch rate of age 12 Walleyes strongly influences the mean age and precaution should be taken when classifying the age‐class distribution as very stable (>8 age‐classes with a mean age >9 y). Male Walleye from Gods Lake grew at a slower rate than females with males reaching 500 mm FL by age 11 and females by age 8. In addition to faster growth rates, females grow to a larger maximum size than males. Walleye from Gods Lake appeared to mature early, with males reaching maturity by age 3 and females by age 7.
Graham Lake exhibited a Walleye CUE of 27.2 fish/100 m2/24 h. Walleye from Graham Lake displayed a broad length distribution ranging from 105 to 718 mm FL, with the dominant peak within the 400–500 mm size range. Walleyes less than 375 mm FL were poorly represented. Similarly, the age‐class distribution was broad, ranging from YOY to age 22 with a mean age of 8.5 y. Strong age‐classes occurred at ages 5, 6, and 8, with the 5 y age‐class dominating the catch at 31%. Based on the AWMRP criteria, the Walleye population in Graham Lake exhibited a wide (>8 age‐classes) and stable (mean age 6–9 y) age‐class distribution. However, the poor representation of younger ageclasses suggests inconsistent recruitment over the last four years. The Walleye population in Graham Lake exhibited slow growth rates, with males reaching 500 mm FL by age 11 and females by age 9. In addition to faster growth rates, females grow to a larger maximum size than males. Walleye from Graham Lake appeared to be early maturing, with males reaching maturity by age 5 and females by age 7.
The information collected in these surveys will provide current data to ASRD, assisting managers in making accurate management decisions regarding the sport fishery and sustainability of Walleye populations within these lakes.