At the last expert meeting it was realized by all that kokanee egg plants alone wasn’t going to turn the lake around and for kokanee to start increasing in numbers we need to plants eggs and cull bull trout that continue to do okay and continue to prey on kokanee. Here are the salient points on this issue:
- Kokanee—they are the primary food source for Gerrard rainbow trout, bull trout (BT) and most other predators in the lake. They have numbered over 1.5 million in good times and nowadays number less than 20,000. Meadow Creek is the primary spawning stream as well as the Lardeau River.
- Gerrard rainbow trout eat kokanee and used to grow to a size of 30 lbs. They have always been low in numbers ranging from 1500 spawners to less than 100 over the last 60 years. Their numbers today are less than 200 spawners but their size is now less than 5 lbs. The same story for BT although unlike the Gerrards they do eat other fish species. Today their numbers are on the low side and size is less than 10 lbs, average around 3-4 lbs. Overall, the BT are doing okay compared to Gerrards.
- Issue—-The numbers of predators (Gerrards and bull trout) increased in the early 2000s because the lake was fertilized starting in 1992 the result of which was significantly increased kokanee numbers from lows of around 200,000 in the early 1990s to well over 1 million by the late 1990s. The decline of kokanee in the early 1990s was due to nutrient uptake in upstream reservoirs (Duncan & Libby) that used to flow into KL. Fisheries management failed to recognize that increasing the kokanee numbers would predictably result in increased numbers of predators (Gerrards and BT). The end result was that by 2009 it was evident that the large predator numbers were eating down the kokanee numbers and certainly by 2012 kokanee numbers declined precipitously low. Management did not adjust the fishery to remove (harvest) the predators. The end result has been that the predators have eaten themselves out of “house and home”.
- Despite my advice management has been loath to reduce predator numbers and now kokanee are < 20,000 spawners for the entire lake. Reduction of BT is necessary to permit kokanee numbers to increase. If predator reduction on a large scale isn’t conducted the kokanee will remain low in numbers and all wildlife that depend on them will be continue to be negatively impacted. The same situation happened on Pend O”Reille Lake just south of you in Idaho. Management there implemented a predator suppression program and kokanee egg plants and within 10 years kokanee numbers went from < 100,000 back to 1 million or more.
- The world famous Gerrard rainbow fishery is now a mere shadow of itself and there are none that exceed more than about 5 lbs. It is very simple—to increase kokanee numbers we have to suppress BT and suppression must be intensive for 3-5 years. I doubt our fisheries managers are committed to this course of action.
- Only two weeks ago we advised John Krebs that the Ministry needs to inform the public about the need to cull bull trout. Nothing was done and now they have a protest on their hands due to lack of public information.
- The BCWF supports the Ministry’s efforts to reduce bull trout.