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Cod off Newfoundland were fished for roughly five centuries, but after factory trawlers and sonar arrived in the mid-20th century the stocks crashed within a few decades. Canada declared a moratorium on northern cod in 1992 that put about 30,000 people out of work, after scientists and managers had overestimated the biomass while catches still looked healthy. The book leaves open whether the stocks will recover.
Dried and salted cod kept for years without refrigeration while staying light and protein-dense. That made it the ideal provision for long voyages and the Catholic meatless fast days. Demand from those two sources pulled Basque, Portuguese, and English fleets across the Atlantic and financed ships, crews, and routes that later served exploration and colonization.
New England merchants sold high-grade salt cod to Catholic Europe and shipped the cheapest refuse cod to the West Indies as cheap food for enslaved plantation workers. They brought back molasses and rum and turned them into profit and more trade. A commodity can hold a colonial economy together by linking one region's surplus to another's labor system, which makes an ordinary food a structural part of slavery.
For centuries cod seemed too abundant to run out, so each more efficient way of catching it was treated as progress rather than as a faster route to depletion. In the cod fishery, that belief in endless supply left fishers and managers unprepared for how finite the stock turned out to be.