Alberta Fisheries Management – The Science of Fish

DSC05408Anglers in Alberta experience world-class fishing today, but this was not always the case.

Starting as early as the 1970s, Alberta’s sport fisheries declined to a shocking degree. Native trout like cutthroat trout and bull trout were rare catches in mountain streams. Lakes once famous for walleye and pike fishing were reduced to shadows of former quality. By the 1980s and 1990s, Alberta walleye fisheries were among the worst in North America; surveys at many lakes reporting 80 per cent of anglers catching nothing during a fishing trip. Angler numbers declined and with them went millions of dollars in lost economic activity.

The explanation for dwindling fish populations was scientifically simple, but socially difficult; overfishing. There were too many people chasing too few fish.  Alberta’s waters and our fisheries are relatively unproductive, but population and interest in fishing has continually increased.

With sound science and help from responsible anglers, the province imposed strict size limits and catch-and-release policies at the most depressed fisheries to protected fish until they spawned several times. Twenty years later, many fisheries haves recovered to the point that fishing success is high and harvest opportunities are increasing.

Why more isn’t always better when recovering fish stocks

Stocking tubesStocking fish seems simple – just replace what has been taken. This is the exact approach that has been taken by fisheries managers throughout the world for decades. The practice seldom works and often creates more complex problems:

  • Fish production in a lake is usually limited by factors such as food, nutrients and water quality. Naturally, far more small fish are born than are necessary to replace older fish and the amount of habitat determines the survival rate of these small fish. Adding more small fish can’t increase production, and usually decreases the survival rate of the existing small fish.
  • If fish are harvested too young they don’t live long enough to spawn a few times and grow to be quality-sized. Stocking a lake with more small fish does little to reduce the problem of excess mortality on large fish.
  • Stocked fish are usually less adapted to local conditions than native fish, which can result in poorer long-term survival and growth rates or worse, hybridization with native fish, which causes poorer long-term sustainability. The bottom line is that stocked fish often do great for the first few years, but then cause a steady decline in quality of native fisheries.
  • It is expensive and potentially ecologically damaging compared to natural reproduction. In a big walleye production year, the Alberta hatchery system handles about 40 million walleye eggs. This is equivalent to the output of fewer than 1,000 adult female walleye – less than four per cent of a single natural walleye lake’s production.

An unnatural solution

While stocking native fish like walleye can be problematic, fish stocking remains an effective management tool. In certain situations, stocking non-native trout for the express purpose of catching and keeping the fish is the perfect recipe for increasing fishing diversity. This is a real shining success story for Alberta hatcheries. Environment and Parks staff stock hundreds of thousands of domesticated non-native trout species annually in put-and-take ponds and reservoirs.

This  will remain an important focus of Alberta fisheries management program.

Why size can matter

The issue of size limits and protecting breeding fish is complex and Alberta’s regulations allowing the harvest of big fish might raise some questions.

At most lakes, there are far more small fish than big fish. Typically in Alberta, 20 anglers will each catch a small spawning-sized pike, and only one angler will catch a big pike. Regulations require the release of the 20 smaller fish to increase the number of eggs that are released.

Consider this: a 100 cm pike might produce 100,000 eggs whereas a smaller 60 cm pike may only produce 25,000. If you were managing a live-well in your boat and caught one big female and one smaller female, you would logically save more eggs by releasing the big one.

This is not the case if you are biologist managing an entire lake’s fishery. That catch ratio is not one big fish to one small fish because catch analysis shows that for every big female fish caught by anglers, there are typically 20 smaller females caught. For pike, that one big fish might have 100,000 eggs, but the 20 small fish would have 25,000 eggs each for a total of half a million eggs. Releasing the numerous small breeders and harvesting the one older fish puts many more eggs back into the lake.

Getting the skinny on harvest

People sometimes ask if overly abundant fish become skinny if harvest does not occur. The simple answer to this is – no.

As Alberta’s fisheries began to recover after the collapses of the 1980s and 1990s, people saw increases in abundance to beyond their recent experiences. At some of these fisheries, walleye became thin and anglers assumed this was the result of overpopulations of starving fish. Opening the lakes to harvest, however, wasn’t the solution. Within three or four years, the skinny fish problem solved itself and relatively plump fish were again abundant, the prey fish (minnows) and predators (walleye and pike) were simply adjusting to new abundances and habitat selection after years of collapse.

Further to this, remote fisheries don’t collapse because no one harvests fish and poor fishing at fly-in lakes is not the result of unexploited fish being over-populated.

Abundant populations of walleye and pike mean that anglers can benefit from restored abundance, either through controlled harvest or quality catch-and-release fishing. This is the fisheries management goal of most fisheries in Alberta; the opportunity for sustainable harvests of fish. Harvest is a great benefit of restored fisheries, and should be enjoyed where sustainable.

This work illustrates that careful monitoring, modern science and conservation-based regulations are necessary to ensure the continuation of Alberta’s amazing fisheries successes – and our successes increase your angling success!

1 thought on “Alberta Fisheries Management – The Science of Fish

  1. I believe your logic on releasing smaller fish and keeping only larger ones, over 63 cm, is flawed. In the last ten years I have not caught one male pike over 63 cm. every one has been a female! If you aren’t catching males, the female population is the one that suffers. A changed to only one fish over 63 cm, which would probably be female, and keeping two under 63 cm, probably a male, would give you a better female population and more spawning stock.

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