Summer Sport Fishery and Special Harvest License at Pigeon Lake, Alberta, 2007
In 2006, Alberta Sustainable Resource Development (ASRD) initiated a pilot project on Pigeon, Newell and Wolf lakes that allowed anglers to harvest walleye from these previously closed fisheries through a Special Harvest License (SHL). Successful applicants purchased a unique license and tag (i.e., similar to big game hunting application and draw methods) that permitted them to harvest walleye within a specified length category (i.e., > 50 cm, 50 - 43 cm, < 43 cm total length, TL). Anglers not in possession of a SHL followed the provincial regulation for each lake (i.e., zero bag limit / catch-and-release).
To monitor the effects of SHL regulations on the sport fishery at Pigeon Lake, the Alberta Conservation Association (ACA) conducted a summer angler survey from 19 May to 27 August 2007. The survey focused primarily on the walleye sport fishery, although we also collected data on the northern pike sport fishery. We collected information on angling effort, catch, and population structure, and calculated uncertainty in angler survey parameters using a bootstrapping method. To collect yield and biological data, we conducted angler surveys in combination with test angling. Finally, we compared results of this study with those from previous surveys at Pigeon Lake during the summers of 1999, 2003 and 2006.
During the 2007 survey period, we estimated 14,760 angling-trips (95% CI = 13,045 – 16,594, n = 3,706 anglers) and 42,870 angling-h (95% CI = 37,917 – 48,507, n = 10,959 h). Angling-pressure was 4.4 h/ha (95% CI = 3.8 – 5.0). However, angling pressure associated with SHL anglers was a small portion of the sport fishery; only 22% or 3,247 anglers interviewed held a SHL. Angling pressure during the 2006 SHL season was slightly higher (by 5%) than pressure during the 2007 SHL season. In addition, angling pressure has increased nearly four-fold since 1999. Of SHL anglers interviewed in 2007, 37% had not fished Pigeon Lake the previous year; this increase in SHL participation may indicate a growing interest in the program.
SHL holders were permitted to harvest walleye from 18 May to 3 September 2007. During the survey period (19 May to 27 August 2007), we estimated that anglers with SHL tags harvested 2,729 walleye (95% CI = 2,277 – 3,245, n = 644). We estimated that 157,629 walleye (95% CI = 136,812 – 179,439, n = 37,741) were released by all anglers (regular and SHL anglers combined), of which, SHL anglers released 15,199 walleye (95% CI = 9,846 – 21,849, n = 10,909). The sport fishery harvested 0.27 kg/ha of walleye and 0.42 kg/ha of pike. The yield associated with the release mortality of walleye (estimated to be 5.3%) was 0.83 kg/ha (95% CI = 0.55 – 1.20) or approximately three times that of the SHL harvest. We estimated that anglers harvested 509 pike (95% CI = 177 – 1,130, n = 73) during the survey period. SHL anglers accounted for 8% of the pike harvest. Anglers released 2,417 pike (95% CI = 1,999 – 2,946, n = 567). Based on proportion of the catch, SHL anglers released 22% of captured pike. The yield associated with pike harvest and release mortality was 0.44 kg/ha.
According to Alberta’s Walleye Management and Recovery Plan, catch rates of walleye were high. The length and age distributions of harvested walleye ranged from 427 to 718 mm TL and age-7 to 10 and 13. Growth of walleye was moderately slow and almost all harvested walleye were reproductively mature fish. The length distributions of harvested walleye and test-angled walleye were very similar (with the exceptions of individual fish < 430 mm and > 550 mm TL). This similarity suggests that anglers were not selecting the largest fish in their SHL length-category, and instead were harvesting the sizes of fish vulnerable to angling.
Relatively few pike were observed in angler harvests; thus, we also conducted test fishing to help categorize the pike fishery. The estimated catch rate for pike was extremely low; the total rate was 0.028 pike/h (legal-size harvest rate = 0.005 pike/h, protected-size release rate = 0.023 pike/h). Based on test fishery data, we found the size distribution of pike in Pigeon Lake to be severely truncated, possibly due to sizeselective mortality and high angling pressure. The size distribution of pike was also unstable, primarily supported by protected-size fish (i.e., < 630 mm TL) with legal length pike (> 630 mm TL) at very low numbers. However, the relative density of small pike was substantial and may indicate considerable recruitment to the sport fishery in the near future. The relative stock density (RSD) and the proportional stock density (PSD) also indicated a truncated size distribution. The percent success and Gini coefficient both indicated the chance of catching a pike was very low. These parameters, including the extremely low catch rate, indicate a highly exploited pike fishery in Pigeon Lake.