MOOSE LAKE-Fallindexnettingreport-2020

Moose Lake FIN Summary 2020

Background Biologists use this information, as well as a variety of data on water quality, access, development, and “How are the fish in my lake doing?” We need this habitat threats as part of Alberta’s Fish Sustainability answer to set appropriate fishing regulations, to Index (FSI). understand and correct any problems with fish habitat, and to guard against invasive species. A healthy fish The management goal for most Alberta fisheries is long-term sustainability, shown by the red lines on the population and fish community means we can all enjoy the benefits of sustainable fisheries and healthy graphs below. Achieving this goal uses the netting data ecosystems. A standard method of assessing the and the FSI to determine the most appropriate sport fishing regulations for a lake. This landscape-level status of fish populations is necessary to allow comparisons of fish sustainability across the years at a assessment allows for consistent, broad temporal comparisons of fish sustainability and status. lake, and to compare to other lakes. In Alberta, we use an accepted standard of index netting for lake fisheries For more information, please see Alberta’s FIN and FSI assessment. This method provides the necessary data websites, on fish abundance, biological data (such as age and • https://www.alberta.ca/fall-index-netting.aspx sex), and species diversity to assess sustainability. • https://www.alberta.ca/fish-sustainability-index- Fall Index Netting (FIN) overview.aspx Table 1 – Alberta’s Fish Sustainability Index risk thresholds for Alberta Environment and Parks monitor Walleye and Walleye and Northern Pike using the standardized Fall Index Net Northern Pike populations using standardized index (FIN) method. Note: Thresholds align with species management netting (Morgan, 2002). Fall index netting occurs during frameworks. late summer and fall when water temperatures are 10- 15 °C. Standardized multi-mesh gill nets are set at Mature Mature Risk to random locations between 2 and 15 metres deep, set Walleyes/ ½ net Pike/ ½ net Sustainability for 21-27 hours (i.e., a net-night), and then reset in new >14.5 >10.9 Very Low random locations. At Moose Lake in 2020, a half-length 10.2-14.5 7.7-10.9 Low variation of the standard index net was used, balancing precision of the catch rates with reduced sampling 7.3-10.1 5.5-7.6 Moderate effort. Information from Yellow Perch, Lake Whitefish, 2.9-7.2 2.2-5.4 High Burbot, minnow, and sucker species are also collected. <2.9 <2.2 Very High The information collected from each fish includes length, weight, age, gender, and maturity. After Results of the 2020 FIN at Moose sampling, if fish are appropriate for human consumption, Alberta biologists provide the fish to local Lake Indigenous peoples or to persons on approved Moose Lake (4541 ha) is located a few kilometres west subsistence lists. Typically, a tiny proportion of the from the town of Bonnyville. From September 8 to 11, lake’s fish population (usually less than 1 or 2%) are 2020, 12 ½-length nets captured 46 Northern Pike, 45 killed in this sampling. Walleyes, 5 White Suckers and 66 Yellow Perch. How is this information used? Walleye Catch rates (i.e., number of fish captured per net-night) The mean catch rate of Walleyes was 3.8/ ½ net-night. of Walleye and Northern Pike are an index of the The catch rates of mature (Figure 1) and immature populations’ abundance, with higher catch rates Walleyes were 3.3/ ½ net-night and 0.5/ ½ net-night, meaning there are more fish in the lake. The respectively. The corresponding FSI score for the abundance of adult fish is compared to the current mature density of Walleyes was assessed at standardized thresholds for 5 broad categories of risk risk. to the long-term sustainability of the fish population, The length distribution shows very weak and very with higher densities of fish having lower risk (Table 1). sporadic recruitment, low abundances of 310 mm to The sizes and age of fish also tell us if problems with 520 mm Walleyes and strong abundances of 530 mm overharvest (e.g. too few fish living to old age) or to 700 mm fish (Figure 2). habitat (e.g., poor spawning success) are a concern.

https://www.alberta.ca/fall-index-netting-overview.aspx ©2020 Gov ernment of Alberta | Published: December 2020 Classification: Public Figure 1 - The FIN catch rate of mature Walleyes from Moose Figure 3 - The FIN catch rate of mature Northern Pike from Lake, 2020. Dashed line is the mean catch rate (3.3 fish/ ½ net- Moose Lake, 2020. Dashed line is the mean catch rate (3.8 fish/ night), with individual net data as hollow circles (n=12 nets). ½ net-night), with individual net data as hollow circles (n=12 nets).

Figure 2 – FIN sample of showing size of Walleyes from Moose Figure 4 – FIN sample showing size of Northern Pike from Moose Lake, 2020. The red line indicates the average length distribution Lake, 2020. The red line indicates the average length distribution of Walleye from 5 Alberta lakes supporting long-term sustainable of pike from 6 Alberta lakes supporting long-term sustainable harvests of Walleye. harvests of pike. The 2020 FIN sample represented approximately 0.2% Walleyes is concerning. Given the Walleye’s current of the estimated mature Walleye population size. risk status, conservation-based management is required to manage the sustainability of this population Northern Pike and fishery. The mean catch rate of mature Northern Pike was 3.8/ Since the 2017 FIN assessment, the status of mature ½ net-night (Figure 3). The corresponding FSI score for Northern Pike has declined from to the current mature density of Northern Pike was risk. The lack of recruitment and moderate-sized pike is assessed at risk. of concern. Strict conservation-based management will The length distribution shows very weak and sporadic remain the focus for this pike population and fishery, recruitment, a low abundance of 550 mm to 700 mm based on the management objective. Northern Pike and a strong abundance of fish larger A s lot harvest regulation is being evaluated for than 700 mm (Figure 4). Walleyes at Moose Lake. Alberta Fish and Wildlife will The 2020 FIN sample represented approximately 0.1% report on its performance as survey results are of the estimated mature Northern Pike population size. available. Summary The status of Walleyes in Moose Lake has remained at risk since the 2014 and 2017 FIN assessments. However, the sharp decline in the Walleyes abundance since 2017, the lack of recruitment and moderate-sized