The Slot Limit – A management tool: Part Two

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In 2000, the Area A Slot Limit for Walleye was implemented. Area A defined by ‘the area south of Gammon-Bloodvein Rivers to the south and west shores of the Winnipeg River, including Lac du Bonnet, and the southern boundary of Whiteshell Provincial Park, and from Lake Winnipeg to the Ontario border (excluding the Winnipeg River from Pine Falls Dam to Lake Winnipeg)’.

The slot limit initially was all walleye between 38 cm and 70 cm must be released. Notice the lower end is not 45 cm but 38 cm. This reflects the different growth rates for walleye located in lakes predominately in the less productive Canadian Shield country versus a highly productive reservoir like LOTP. The growth rates are different, however the age at sexually maturity for walleye would remain the same at around 5 years of age. The lower limit of 38 cm would again try to encompass most mature females in the population. The lower end of the slot was raised from 38 cm to 40 cm in 2002, raised again in 2004 from 40 cm to 42 cm and once more in 2007 from 42 cm to 45 cm. I think the intent was to start at the biologically preferred size and eventually raise the lower limit to allow more additional harvest for anglers as well as keeping the slot the same as other lakes in Southern Manitoba (LOTP, Whitefish and Wellman Lakes for example) possibly to avoid regulation confusion.

There is a challenge in adopting one size specific regulation such as a slot limit, to a large area like this. Not all lakes are created equal. Pre-slot limit data in Area A is limited but obviously warranted a drastic change in walleye regulations for the area. When we (Eastern Region Fisheries Branch) started our Non-Lethal Sampling Program (NLSP) in 2008, some of our initial objectives were to look at the comprehensive walleye data collected and see what state walleye populations were in, how effective walleye fry stocking was on target lakes (most of them within the Area A identified boundaries), and attempt to see how effective the slot limit was working on a lake by lake basis. We targeted lakes that had some form of development (cabins, lodge, campground etc.) and easy access (both would allow for potential intense harvest pressure on walleye stocks) and were within the Area A walleye slot limit boundaries. Also, most of the lakes we looked at were stocked annually with hundreds of thousands of walleye fry.

Our results have shown us that only certain lakes have responded well to the slot limit regulation. These lakes all have solid natural reproduction. (walleye fry stocking contributes less than 5% to the walleye population) Also walleye age structure was healthy, representing many year classes, both in the slot and below the slot and these lakes usually were the most bio-diverse in that they held many different species. An example of these lakes include Jessica, White, Betula, Beresford and Big Whiteshell. On these lakes we will only stock walleye fry during years of draught in order to boost natural recruitment. We do this because even if the lakes do not naturally produce decent year classes, the pressure from anglers does not necessarily stop.

On other lakes such as Booster, Barren, and Caddy, we caught less walleye and fewer year classes. All had some level of natural reproduction, lower catch rates of walleye and fewer strong year classes. Walleye fry stocking contribute 35 % – 55 % annually to the walleye population as yearlings. There are also modest populations of yellow perch, smallmouth bass and black crappie, which compete for food with walleye at all life stages. On these lakes, the slot is still effective, however we would stock more walleye fry per year but would stock alternate years. We do this because in a natural scenario, if you have two back to back bumper crops of walleye, usually the second one does not make it much past the post larval stage due to extreme competition from the previous strong year class.

There are definitely some lakes that should be regulated under some kind of minimum size and/or altered slot size. I also firmly believe that all the walleye lakes in Area A should have a limit of four walleye. However, at this point in time I do not think we have an option to fit regulations based on a lake by lake basis as a result of our NLSP studies. The angling guide would simply get too complicated (or would it?). What we can do is continue to assess our lakes, and apply our knowledge and common sense to move forward in the best possible direction.
I have definitely simplified this topic and the work we have carried out to a large degree. However, I think what it does point out that we face great challenges when managing our fisheries resources. We have many tools and techniques at our disposal and just one of them is the slot limit. The absolute key to relative success is to be able to access the data with adequate staff, equipment and funding required to manage our fisheries properly for now, and the future.

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About Author

Ken has recently retired from a 30+ year career in fisheries research and management conducted all across Manitoba. From the Theliwaza and Lower Nelson Rivers, to Manitoba’s Parkland and Whiteshell areas, Ken has worked tirelessly in efforts to improve fish populations and recreational angling opportunities through science and common sense based realities. A rabid fisher himself, with a penchant for tossing flies at rather large salmonids, Ken hopes to share his knowledge with all Hooked Magazine readers through the unique combination of biologist and angler.

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