 In Trout Lake, several decades of overharvesting native lake trout (salvelinus namaycush) have drive the population down to low levels. Anglers were fishing a very long time and not catching very much. The MNR therefore decided to add hatchery reared lake trout (hereafter referred to as stocked trout) to increase angling success. From 1980 to 1990, over 100,000 stocked lake trout (fingerlings) were added to Trout Lake. Stocking locations included Four Mile Bay. What they failed to realize was that, in Trout Lake, only the native lake trout spawned. Adding stocked fish fuelled continued overharvesting and eventually drove the native lake trout to near extinction. When the lake trout angling season was closed in 1991 few large native lake trout were seen frequenting the spawning beds. At this time it was anybody's guess as to whether or not there were enough native fish left to make a come-back.
A self reproducing lake trout population is desirable in Trout Lake as they have adjusted to the lake over thousands of years and are best suited to the habitat. Natural reproduction requires clean water, good spawning habitat and good rearing habitat. Managing a lake for natural reproduction means taking care of the entire lake ecosystem, which make a lot of sense for Trout Lake as it is the sole source of drinking water for the City of North Bay. The native lake trout act as a natural, overall health indicator of the Trout Lake ecosystem. It is also much more economical to let the lake trout reproduce naturally. In conjunction with the lake trout closure, a "sonic" - hydro acoustic tracking program was also implemented. This was a community driven research project, overseen by our local Ministry of Natural Resources. We wanted to know more about the behaviour of the stocked and native lake trout. We also wanted to know if there were other spawning areas other than the Camp Island shoals. |
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The crux of the matter is this. With the lake trout angling season closed, how do we monitor the recovery. Also, how do we decide when the native lake trout populations have recovered enough to allow a controlled reopening of the lake trout angling season. Important questions with no easy answers. |
| The Ministry of Natural Resources operates a summer indexed gill netting program on Trout Lake to track the size of very young lake trout population. The idea is to target two to three year old fish in the gill nets and compare the catch on a year to year basis. The problem is that many of the fish die - the very fish that are trying to make a recovery. However, this does provide some indication of the state of the recovery. In 1996, the catch per unit effort was 9.7 lake trout /net / nigh; while, the c.u.e. in 1997 was 5.9. Thus lake trout are slowly recovering in Trout Lake. |
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A novel approach, spearheaded by Eric Marcotte and Anne Renée Gadoury, under the direction of senior scientist Mr. Jean-Marc Filion, is to track the average length of Mysis relicta, the freshwater shrimp. What they have found is that the average length of the shrimp decreases as the numbers of small lake trout increase. This is due to the small lake trout selectively keying on the larger Mysids. This is another tool that can be used to estimate when and how to restrict the harvest. |
 Two other lake trout monitoring programs were implemented by the Trout Lake Conservation Association. The first is a lake trout spawning bed observation program, whereby volunteers count the number of fish that they see on the spawning beds. This is done repeatedly over the spawning period. The maximum number of fish seen is recorded and plotted on a graph on a yearly basis. The graph shows that we have a slowly rising population of spawners. Clearly the conservation measures implemented thus far are having the expected beneficial effect. We expect an accelerated increase in the spawning population as the younger fish add to the recruitement.
Notice that the gill netting bar graph and lake trout spawning bed observations bar graph show statistical fluctuations from year to year. It is the longer term trend that is important. These two programs measure different aspects of the lake trout population. The gill netting program shows a positive increase in both lake trout standing stock while the spawning bed observation program shows an increase in mature spawning stock. (spawning bed observation program). |
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The second program (called the TransCanada Pipelines Lake Trout Watch, in honour of our corporate sponsor for this project) consists of a laser driven, electronic based, underwater observation system developed by Marc-André and Jean-Michel Filion. They have dubed their system R.A.M. which stands for Remote Acitivity Meter. In this system, a laser is placed underwater, on each of the two spawning beds. |
| When a fish cuts the laser beam for more than 0.2 seconds, the electronics count this as an event. Every hour, the number of fish events are stored in microprocessor memory.
The fall of 1996 was the first complete observation period for this new, automated system. Results are presented in the accompanying graph. More than 3000 fish events were recorded during the 1996 lake trout spawning run. A year to year comparison of RAM data should correlate to native lake trout population stock. In the long run we are hoping that this system will do away with the gill netting program. |
