No, that kept all the unwanted riffraff off the tropical island. Of course, for those of you who are James Bond fans, it turned out to be an armored vehicle painted like a dragon.
In this case the boat that was emerging out the darkness, lit by a brilliant bank of lights, was affectionately known as “Silver” by fisheries biologist Ken Kansas. And silver it was with electrodes hanging off the front and arms thrust to front with more electrodes, a fearsome looking critter in its own right.
This twenty foot flat-bottom aluminum vessel (designed and built by Smith-Root) is mounted with a genera¬tor that creates electrical currents that pass through positive (anodes) and negative electrodes (cathodes) hang¬ing partially submerged in the water in front of the boat. As the vessel cruises through the water, a field of electricity precedes the path of the boat. The right amount of current elicits taxis, an invol¬untary muscular response that causes fish to swim towards the anodes. Once fish reach an anode, they stop swim¬ming and go into narcosis (stunned), floating belly up. Since narcosis only lasts for a few secon
ds, biologists must quickly net the fish, which they put into a holding tank or live well during the “run” (sampling period).
That’s where Fish Futures President David Carrick and I came in. We had been asked by Kansas and Eastern regional fisheries manager Doug Leroux to see the boat in action first hand.
I don’t think we quite knew what we were in for.
Working in the darkness was critical since fish numbers rose dramatically under the cover of night. All species of fish become more active in the less than three metres of water that was required for this type of work. Off the front where a bank of lights that allowed those in the front of the boat who were netting the stunned fish to quickly get a net down to the fish. Since I was the one with the fancy camera, I was set on shore to capture the moment. And what moments did we have! On a trial run while it was still light out, I had dipped a massive lake whitefish that got my heart a pumping.
After a quick supper, we were back out in the darkness, starting out on a rocky point on the main lake that marked the entrance to a shallow bay. As Carrick and Kansas swung the electrode booms out and “kicked in the juice” a massive fish appeared off the starboard. Leroux immediately spotted the fish and piloted the jet drive to where Kansas could get his net under this massive specimen. But I get ahead of myself.
SOME HISTORY: Ken Kansas, who has been a biologist with the province for a number of years put together a summary of fish assessment since he has been with the branch. Here is a brief history.
“Fisheries personnel have used gill nets as a fish stock assessment tool for many decades. This technique is indeed an effective method to collect fish population data and has greatly assisted fisheries staff over the years to make the management decisions necessary to ensure sustainability of our fisheries resources. This method of assessment is certainly an effective tool, especially on large lakes where the amount of fish mortalities using this technique (usually 100%) will not negatively impact fish populations as a whole. In these scenarios, a well designed and sometimes annually occurring index gill netting program is quite necessary.
In the Eastern Region of Manitoba there are a large number of smaller lakes which have easy access, subsequent high recreational use including sport fishing and developed shorelines in the form of cottages and/or campgrounds. Most, if not all of these lakes have had their fish community assessed in the form of a gill net survey at least once in the past few decades. In some cases, as with Lac du Bonnet, an annual index netting program has occurred since the early nineties. Information gathered using this method is invaluable and has a very insignificant impact to the overall fish community considering the lake size (3500+ hectares) and the small amount of fish taken for scientific and management purposes.
On smaller lakes however (less than 500 hectares), which have a low Maximum Sustainable Yield (MSY) combined with potentially low success in terms of natural recruitment, any amount of fish removed for stock assessment (walleye for example) might have a negative impact on angler success for years to come.
Numerous government agencies across North America utilize non-lethal methods of fish stock assessment for the exact same reasons as mentioned above. Timely and consistent data collection, analysis and interpretation on high profile, heavily utilized lakes which receive high angling pressure is essential for fisheries managers to effectively manage these fisheries. Utilizing established, non-lethal stock assessment methods, these data can be collected without negatively impacting the fisheries and provides current and quality information required by the managing agency.
Some of these non-lethal methods which have proven effective in fish community assessments include seasonal trap netting and boat electrofishing. Both these methods feature extremely low mortalities (less than 5%) if conducted properly. Even though both techniques tend to bias towards the littoral fish community, conducted in tandem and during different times of the day and year, will yield quality data.
The Eastern Region of Manitoba has numerous lakes which fall into the category of high profile, developed and intensively utilized fisheries which require comprehensive stock assessment. Non-lethal assessment methods provide the only tool available to fisheries managers for fish community assessment that do not negatively impact existing fish stocks. According to Kansas the two main objectives are
1) up to date fisheries inventory data, species assemblages, catch/unit of effort, size, age etc…
2) assess eastern region walleye stocking program-all fry since 2006 have been marked with Oxytetracyline (OTC) we can determine stocked vs natural walleye because of this”
Here is a sample of the species we dip netted on this particular trip, a short two hours of work total