Verification of Effectiveness of Spring Closure Zones on North and South Wabasca Lakes, Alberta, 2008 - 2010
Clayton James and Paul Hvenegaard
Domestic and recreational harvests are potential threats to the sustainability of the walleye population in North and South Wabasca lakes. In 2008, spring conservation closure zones were established by Alberta Sustainable Resources Development (ASRD) surrounding two inlets, Drowned-horse Creek and Willow River, on North and South Wabasca lakes respectively, to prevent the harvest of walleye on their spawning grounds during early spring. From 2008 to 2010, 64 mature walleye implanted with radio tags (41 in North Wabasca Lake and 23 in South Wabasca Lake) were tracked using radiotelemetry to determine both the spatial and temporal effectiveness of the closure zones.
We monitored walleye movements before, during and shortly after the spawning season from April to July using both boat and aerial surveys. Our ability to detect tagged fish varied on average (±SD) from 58.1 ± 8.2% in 2009 to 64.5 ± 5.1% in 2010. In 2009 and 2010, peak spawning activities occurred from 3 to 9 May in South Wabasca Lake and 3 to 16 May in North Wabasca Lake. Over the course of the study, the majority (>50 %) of tagged fish occupied the South Wabasca Lake closure zones until 10 June in 2009 and 2 June in 2010. In North Wabasca Lake, the majority of walleye occupied the closure zones until 17 June in 2009 and 27 May in 2010.
We observed 100% fidelity of tagged fish within the lakes during the spawning period in 2009 but some inter-basin movements (~4%) occurred in 2010. To determine the genetic relatedness of fish between sites, tissue samples were collected and were compared using microsatellite markers. Although fish movement between basins was limited during the spawning period, pairwise comparisons between spawning locations indicated no genetic differentiation between groups.
In terms of angling pressure, on North Wabasca Lake we observed an average of 8 ± 2 boats per telemetry relocation survey in 2010, compared to zero boats on South Wabasca Lake in 2010.
This study confirms the temporal and spatial effectiveness of the spring conservation closure zones, implemented in 2008 by ASRD, in protecting the spawning walleye population.