Lake Trout Fishing Winter 2018/2019 – Brian Evans
Now that the ice has finally cleared the lake its time to reflect on this past season’s ice fishing success. Certainly my review of the Kennisis Lake face book pages indicated that some larger than average Lake trout were caught this winter. There was much discussion about these larger lake trout, their impacts on the overall lake trout population and whether these are spawning fish or not. To address these comments and concerns I asked Minden based MNR biologist for Zone 15, Adam Chalice to provide us with some feedback;
Adam – Kennisis Lake appears to have a small-bodied lake trout population with some large individual lake trout sprinkled throughout based on the historical assessment data. This is common for many lake trout lakes in central Ontario. Small-bodied lake trout can be sexually mature at 1.5- 2 lbs. To give you a sense on biological calendar for lake trout in Kennisis, the 1991 length at age data available on file suggested a fish at 250 mm would be between 4-6 years old and the lake trout would just be entering sexual maturity at this size and age. The 2010 length data suggests not much has changed.
There is a well known relationship between size/age and eggs produced for female lake trout. Once lake trout shift their energy from growth to gonad development, their overall growth rate declines and their egg production / unit weight of flesh increases. Egg production increases annually to a point until it plateaus. This rate of egg production and maximum egg potential varies by individual fish and is greatly influenced by diet – case in point in Kennisis where the majority of trout never exceed 500 mm in fork length, they are likely primarily feeding on plankton and littoral baitfish whereas the larger trout may at least partly be utilizing cannibalism to attain overall higher growth rates and maximum size. For those few individuals which take this path, their egg development is likely delayed as they continue to invest in growth rather than egg production at the same age as the majority of small-bodied trout who have shifted to egg development. Eventually even those large lake trout egg production plateaus and will eventually decline with old age.
There were some suggestions that larger sized lakers were no longer spawning and fed heavily on smaller lake trout.
Adam – I would offer that all lake trout should be given equal value, regardless age or size. Lake trout are slow growing, late to sexual maturity and occupy cold deep and largely unproductive lakes. Additionally, they are also opportunistic feeders which often feed in groups and will demonstrate flexible diets if conditions exist so its inaccurate to assume the very large fish are exclusively cannibals. Cumulatively, these characteristics make them vulnerable to overexploitation. Without the luxury of knowing the specific age or egg production of the fish one holds in their hand, understanding these dynamics as anglers will support the long-term sustainability of the fishery.
Five pound plus fish are getting harder to find and catch though lots of small fish are being caught.
Adam – This is not unexpected. The large (5+ lbers) are relatively rare compared to the abundance of small-bodied lake trout. Interestingly, based on available angler diary data from Kennisis from 2008 – 2010 anglers were appearing to catch larger fish on average than what the netting data showed which may have been for several reasons including size selectivity of the gear and anglers! We also know that lake trout populations are highly adaptable in their diets. New angler diary data is required to compare the 2008 – 2010 data to now and see if there has indeed been a shift overall to smaller fish. I am very interested to gather unsubmitted angler diaries and reinvigorate the program on Kennisis with your support. Its purely anecdotal, but the literature is very strong in helping to understand the negative impact the introduction of rock bass may be contributing to the potential reduction in overall size as rock bass would consume a significant portion of littoral area baitfish biomass that would have been previously available to lake trout, particularly in the spring.
As a general statement the lake trout population in Kennisis lake appears to be healthy based on the best available information and the lake contains excellent cold-water habitat (ie high dissolved oxygen in the deepest parts of the lake). Anglers are strongly encouraged to record their effort and catches and harvest using the angler diary template and submit them annually to our office to support fisheries management.
The most important actions to maintain the fishery are already outlined in the Kennisis Lake Fishery: Past Present and Future (Kemp et al. 2010). I would add that raising awareness of invasive species and introductions is another critical action that needs to be implemented which I am sure the cottage association is already doing, but the introduction of rock bass and its potential impact on lake trout highlights that.
If you would like to help out with updating our understanding of the Lake Trout population trends in Kennisis by participating in the Angler Diary Program you can email your completed daily diary sheets to the email address on the form.
Update on FMZ Zone 15 regulation changes
The Zone 15 Fishery Council and Ministry of Natural Resource ‘s representatives have now met some 20 times over the last 2 years to review and propose changes to fishery regulations in Zone 15, the zone in which Kennisis Lake is located. Progress has been slow as the council members had to come up to speed on a significant amount of data and research on the current state of the fishery and the impact reg changes could have on the fishery across the variety of species in the zone. The Council is just now reviewing the final species, Lake Trout with the expectation that the proposed regulations could be out for public consultation sometime in 2020. With the goal to have self-sustaining and growing populations of most species, Lake Trout regulations could see changes such as shorter seasons. slot limits and maximum keeper size limits to enhance protection of this heritage fish which is one of the most vulnerable to rising lake temperatures related to climate change . That being said, most fishers should welcome changes that could enhance the fishing experience in the Haliburton area. Stay tuned for your opportunity to comment on any proposed changes sometime next year.