ENV100Y5 Lecture Notes - Lecture 38: Atlantic Cod, The Big Questions, Groundfish
Module 4: July 3-13
Date: Saturday, July 7
SESSION 41: MARINE AND COASTAL SYSTEMS (III)
Readings: Chapter 12
The Big Questions:
● How come Atlantic cod yields continued to increase in the 1980s, even as the stocks
were being severely depleted?
○ Fisheries are super complicated. See “Several Factors Mask Stock Decline”
● Why didn’t anyone notice what was happening?
● And why didn’t those who did notice, do anything meaningful to stop it?
○ They tried, but fishers and scientists do not have much political power.
Government officials do not want to be the one who wants to stop people from
fishing after it has been one’s livelihood for so long.
Several Factors Mask Stock Declines
● Industrial fishing can deplete stocks while yield/catch remains stable, because:
○ Fishing fleets travel longer distances to reach less-fished portions of the ocean
○ Improved technologies: faster ships, sonar mapping, satellite navigation, thermal
sensing, aerial spotting
○ Fleets spend more time fishing
○ Data supplied to international monitoring agencies may be false or incomplete
○ Some fish cluster together so it is difficult to know exactly how many remain
We Are “Fishing Down the Food Chain”
● Figures on total global catch do not relate the species, age, and size of fish harvested
● As fishing increases, the size and age of fish caught decline
● As species become too rare to fish, fleets target other species
○ Shifting from large, desirable species to smaller, less desirable ones
○ Catching species at lower trophic levels
● Makes it look like the catch is staying the same but it’s actually declining
The Current Status of Atlantic Cod is Still Endangered
● The most severely depleted stocks are not recovering
● The entire ecosystem has shifted to a more shallow-water focus - greater pelagic
biomass, less groundfish biomass
● Social and economic impacts:
○ Devastating for communities in Eastern Canada
○ If the fishery were to reopened, fishers would come back in full force
○ If fishing capacity is not greatly reduced, the fishery will simply be depleted again
Fisheries Management is Based on Maximum Sustainable Yield
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Document Summary
They tried, but fishers and scientists do not have much political power. Government officials do not want to be the one who wants to stop people from fishing after it has been one"s livelihood for so long. Industrial fishing can deplete stocks while yield/catch remains stable, because: Fishing fleets travel longer distances to reach less-fished portions of the ocean. Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting. Data supplied to international monitoring agencies may be false or incomplete. Some fish cluster together so it is difficult to know exactly how many remain. Figures on total global catch do not relate the species, age, and size of fish harvested. As fishing increases, the size and age of fish caught decline. As species become too rare to fish, fleets target other species. Shifting from large, desirable species to smaller, less desirable ones. Makes it look like the catch is staying the same but it"s actually declining.
