Managing Populations: Indigenous Knowledge, Sustainable Harvests and Careers

From models to decisions

Every hunting season, fishing quota and conservation plan in Canada is a population-dynamics decision. In this final lesson you will apply the logistic model to harvesting, learn from one of Canada's hardest lessons (the collapse of the northern cod), see how Indigenous knowledge and co-management help sustain populations, and explore careers that use everything in this unit.

Maximum sustainable yield

If a harvest equals the population's growth, the population stays the same: ΔN = growth − harvest = 0. From Logistic Growth and Carrying Capacity, growth is fastest at N = K/2, where dN/dt = rK/4. So in theory, the maximum sustainable yield (MSY) is rK/4, taken from a population kept at K/2.

But look at the graph below. For any harvest smaller than MSY, there are two population sizes where growth equals harvest:

• The upper one is stable: if N rises a little, growth falls below the harvest and N comes back down; if N falls a little, growth rises above the harvest and N recovers.
• The lower one is unstable: if N falls below it, growth is less than the harvest, so the population keeps shrinking, faster and faster, toward collapse, unless harvesting is reduced.

At MSY itself, the two points merge, so any small overestimate of the stock or bad year can tip the population into decline. That is why modern fisheries management uses a precautionary approach: harvest less than the estimated MSY and cut catches early when a stock declines. Fisheries and Oceans Canada classifies stocks into healthy, cautious and critical zones and is supposed to reduce fishing as a stock moves toward the critical zone.

The collapse of the northern cod

For centuries, Atlantic cod off Newfoundland and Labrador supported fishing communities. Beginning in the 1950s and 1960s, large foreign and domestic factory trawlers using new technology (sonar, powerful engines and huge nets) took enormous catches, and catches crashed in the 1970s. Canada extended its fishing zone to 200 nautical miles in 1977, and Canadian fleets expanded. Through the 1980s, stock assessments overestimated the population, partly because catches per trawler stayed high even as the stock shrank (fish gathered in dense schools that modern gear could still find), and inshore fishers' warnings that fish were getting scarcer and smaller were not given enough weight.

On 2 July 1992, the federal government declared a moratorium on the northern cod fishery. It was one of the largest layoffs in Canadian history: tens of thousands of people lost work. Recovery has been very slow. Cod mature at several years old, the fishing had removed many of the largest, most fecund females, and the ecosystem had changed.

Population dynamics explains much of this: harvests above sustainable growth, uncertainty in N, a lowered effective K from ecosystem change, and the slow recovery of a later-maturing species. The I = P × A × T idea applies too: technology (T) multiplied fishing power far faster than scientists could measure the stock. Researchers such as Ransom Myers of Dalhousie University went on to show that many of the world's large predatory fish populations had declined sharply under industrial fishing.

Indigenous knowledge and resource management

First Nations, Métis and Inuit peoples have managed relationships with the animals, plants and waters of their territories for thousands of years, and continue to do so today. Their knowledge systems are diverse; each nation has its own knowledge, laws and practices. Many share principles that match what you have learned in this unit: take only what is needed, share, watch the land over long periods, and think about future generations. A few examples:

• Two-Eyed Seeing (Etuaptmumk). Mi'kmaw Elders Albert and Murdena Marshall of Unama'ki (Cape Breton) introduced this principle: learning to see from one eye with the strengths of Indigenous knowledge and from the other with the strengths of Western science, and using both eyes together. It now guides many Canadian research and management projects. The Mi'kmaw concept of netukulimk describes using what the land provides for the community's well-being without harming the integrity, diversity or productivity of the environment.
• Inuit Qaujimajatuqangit. In Nunavut, wildlife decisions are made through co-management under the Nunavut Agreement (1993). The Nunavut Wildlife Management Board includes Inuit and government appointees, and Inuit hunters' long-term observations of caribou, polar bears and other species are used alongside scientific surveys in setting harvest levels.
• Haida Gwaii. Gwaii Haanas National Park Reserve, National Marine Conservation Area Reserve and Haida Heritage Site is managed jointly by the Haida Nation and the Government of Canada through a board with equal representation.
• Clam gardens. On the Pacific coast, Coast Salish, Kwakwaka'wakw and other peoples built rock walls at the low-tide line, creating terraces of sand and gravel. Studies have found that these clam gardens can produce more clams than unmodified beaches, a form of raising carrying capacity that has been sustained for generations.
• Manoomin (wild rice). Anishinaabe communities in northwestern Ontario harvest wild rice by canoe, gently knocking ripe grain into the boat so that much of it falls back into the water to reseed, and they speak up to protect rice waters from damage such as changing water levels.
• Indigenous Guardians. In many First Nations, Métis and Inuit communities across Canada, Guardians monitor wildlife, water quality and land use in their territories, combining traditional knowledge with tools such as GPS and water testing.

In the northern cod story, inshore fishers' local knowledge was underused; in co-management, long-term knowledge holders have a formal role in decisions. This is one reason co-management is increasingly seen as both more just and more effective.

Careers in population dynamics (A2.1)

• Wildlife biologist / ecologist: surveys populations (mark-recapture, aerial surveys, camera traps), models growth and recommends harvest limits. Usually a B.Sc. in biology or ecology; many positions need an M.Sc.
• Fisheries scientist (stock assessment): estimates fish populations and sets catch advice, for example at Fisheries and Oceans Canada. B.Sc. plus graduate study in fisheries science or quantitative ecology; strong math and statistics.
• Fish and wildlife technician: fieldwork, trapping and tagging, data collection. Ontario colleges offer two- and three-year fish and wildlife technician programs.
• Conservation officer: enforces hunting and fishing laws and educates the public; college or university training in natural resources plus law enforcement training.
• Indigenous Guardian: monitors and protects lands and waters for First Nations, Métis and Inuit communities; training often combines community knowledge with certificates in field skills.
• Demographer: studies human populations (births, deaths, migration) for Statistics Canada, governments and companies; degrees in statistics, sociology, economics or geography.
• Epidemiologist: studies how diseases spread through populations (Public Health Ontario, the Public Health Agency of Canada); usually a master's in public health or epidemiology.
• Agronomist / plant breeder: develops crop varieties and practices to feed growing populations; B.Sc. in agriculture or plant science, often graduate study.
• Environmental consultant or planner: assesses development projects' effects on populations and ecological footprints.

Canadian contributors you met in this unit (A2.2): Charles Krebs (snowshoe hare research in the Yukon), David Schindler (Experimental Lakes Area), William Rees and Mathis Wackernagel (ecological footprint), Robert MacArthur (born in Toronto; r- and K-selection, resource partitioning), Charles Saunders (Marquis wheat), Baldur Stefansson and Keith Downey (canola), Stanley Zlotkin (Sprinkles), Ransom Myers (fisheries decline), and Albert and Murdena Marshall (Two-Eyed Seeing).