When formulas fail: The ecological impact of commercial fishing

Brett Favaro, the Peak (Simon Fraser University)

VANCOUVER (CUP) — Another productive Canadian fishery is in a state of emergency.

The Department of Fisheries and Oceans has closed all commercial fishing of Fraser sockeye due to surprisingly low numbers of returning fish. Like the Atlantic Cod fishery of the early 1990s, the public is demanding to know how an abundant species of fish could be driven to such catastrophically low numbers in a relatively short time.

A look at the global trends behind fishery management may provide answers.

To British Columbians, the Fraser sockeye is one of many examples of managed fisheries collapsing in both Canada and around the world. By our best estimates, the global fish biomass has dropped 90 per cent since the early 1900s. If this trend continues our oceans may end up devoid of any organisms fit for human consumption.

Understanding how a managed fishery can crash lies first in knowing how fishery science is used to manage fish populations. Modern methodology involves calculating a maximum sustainable yield, designed to bring down the number of fish in a population to a level where reproductive output is projected to be bigger thanks to fewer individuals being forced to compete for resources. The maximum sustainable yield can be calculated a number of ways, all based on mathematical values that fail to consider key ecological factors.

The way humans prey upon fish differs from predator-prey interactions in nature. In a natural ecosystem, predators target the young, old and weak as they are the easiest to hunt. When we fish, our nets are designed to catch the largest and healthiest individuals.

We target healthy reproductive adults that would have otherwise spawned the next generation of fish. Remove too many before they get a chance to spawn and it knocks down the number of offspring in the future generation, threatening the species’ survival.

We’re effectively removing the capital rather than living off the interest.

The second major flaw in the logic behind fishery science is the myth that we have a surplus of fish available for consumption. Ecosystems evolve over millions of years to reach the point of equilibrium we observe today. Predators evolve to become more effective at catching prey, which favours the evolution of prey individuals that have large numbers of offspring. When humans remove millions of reproductively mature fish, no allowance exists for this increased drawdown. Predators continue to mount the same predatory stress on the existing species, and those prey species dwindle in numbers. If this continues over many years, a crash of the population occurs.

One management solution governments have been hesitant to enact, yet is most likely to succeed in making a fishery truly sustainable are no-take zones — areas of the ocean where commercial fishing is forbidden.

The concept is simple: if no commercial fishing occurs in an area, it becomes a sanctuary for the species. Fish in that area increase greatly in size and abundance, causing a spillover effect into surrounding areas where fishing is allowed. Yields will increase with less fishing effort, and the fishery will be far more resistant to collapse. These no-take zones require less management than current complex regulatory structures and are far more effective.

Historically, no-take zones have been resisted by certain segments of the population. This attitude is short-sighted and ignores the ecological realities of fishery management. I encourage readers to go online and research the effects of no-take zones and to contact their local Member of Legislative Assembly, Member of Parliament and Premier Campbell to voice support for these measures. Canada has the opportunity to become a world leader in fishery management by setting aside large areas of our vast oceans as no-take-zones, thus preserving our marine resources for future generations.