Fish Resources

Wild populations of fish have long been exploited as food. In recent decades, there have been enormous increases of the rate of harvesting of wild fish, and also in the cultivation of certain species in semi-domestication, a practice known as aquaculture. Like crop plants, livestock, and forests, populations of fish can be harvested in a sustainable manner, which would allow the yields to be maintained. However, fish stocks can also be over-harvested to the degree that their regeneration is impaired. When this happens, productivity declines and the bio-resource can disastrously collapse. Regrettably, the recent history of many of the world’s major fisheries provides abundant examples of over-exploitation causing rapid declines in resources.

The global harvest of fish, crustaceans, and shellfish in 2012 was about 91-million tonnes. This included 66-million tonnes of marine fish (representing a 4% decrease over 1993), 10 x 10⁶ t of freshwater fish (a 91% increase), 1.7 x 106 t of diadromous fish (these are mostly salmon that migrate between salt and fresh water; +6%), and 44 x 10⁶ t of fish grown in aquaculture (294% increase) (Table 14.11).

Table 14.11. Fish Catches and Aquaculture in Selected Countries. Data are in 10⁶ t/y in 2012, with percentage increase since 1993 given in brackets. Countries are listed in order of decreasing catches of marine fish (data include diadromous fishes). Source: Data from FAO (2014).

Image 14.3. Bottom-dragging is a technology used to harvest fish or scallops by drawing an open net along the sea floor, which in some respects is the marine equivalent of clear-cutting a forest. This boat is used to drag for scallops off southwestern Nova Scotia. Source: B. Freedman.

p class=”comments-section”>Canada is a major fishing nation, with an annual harvest of 803-thousand tonnes of marine fish in 2013, with a value of $2.1 billion (Table 14.14). There was also a substantial harvest of freshwater fish, equivalent to 29 x 10³ t and a value of $67 million. Aquaculture is also becoming increasingly important. The total harvest of fish in 2013 was 174-thousand tonnes, with a value of $834 million. Total exports of fish products had a value of $4.15-billion. The exports were partly offset by fish imports of $2.74-billion, for a net trade balance of $1.41-billion in this economic sector.

The most important marine species harvested are summarized in Table 14.12. Note that these data are for Canadian landings only. Some foreign nations also fish waters within Canada’s 320 km management jurisdiction, but their landings are not included in the table.

Table 14.12. Landings of Selected Fishes in Canada. Catch biomass is in 10³ t/y, and economic value is in millions of dollars. Data are for 2012. Source: Data from Fisheries and Oceans Canada (2014a).

In 1992, the total catch of cod in Atlantic Canada was 239-thousand tonnes, of which 80% was landed by Canadian vessels and 20% by the foreign fleet working within the 320-km management zone (see Canadian Focus 14.2). The 1992 catch was, however, much smaller than what had been attained in previous decades, which averaged as much as 598-thousand tonnes during 1982–1986 (81% was Canadian landings). In fact, the declining harvest reflected a collapse of the cod stocks throughout eastern Canadian waters, a resource calamity that resulted in the closure of virtually the entire fishery in 1992. The cod stocks were still largely closed to commercial exploitation in 2014 (when this was written), and will likely remain so for several years. In 2012, the cod landings in the Atlantic region were 11-thousand tonnes, only 5% of the catch in 1992. The devastation of cod stocks in the northwestern Atlantic Ocean, mostly caused by Canadian over-fishing, is a world-class example of the mining of a potentially renewable bio-resource.

Canadian Focus 14.2. Mining the Cod
In 1497, John Cabot explored waters around Newfoundland on behalf of the English Crown. On his return, he wrote with enthusiasm that the Grand Banks were so “swarming with fish [that they] could be taken not only with a net but in baskets let down [and weighted] with a stone.” At that time, cod (Gadus morhua) was a bountiful resource on the Grand Banks, a relatively shallow marine ecosystem of 25-million hectares. Large cod stocks also occurred off Labrador, Nova Scotia, the Gulf of St. Lawrence, and New England.

By 1550, hundreds of ships were sailing from coastal Europe, catching cod and preserving it by drying or salting to sell in their home markets. By 1600, about 650 ships were fishing off Newfoundland, and by 1800, it was about 1,600 vessels. Between 1750 and 1800, the average landings were 190-thousand t/y which increased to 400-460-thousand t/y during 1800-1900, and almost 1-million t/y between 1899 and 1904 (Mowat, 1984; Cushing, 1988).

In those early times, the cod were harvested using hand-lines, long-lines, traps, and seines. Many men fished from small dories, often launched from a larger mother ship, such as one of the celebrated fishing schooners that sailed from Newfoundland or Nova Scotia. Although this technology is inefficient, the total fishing effort was large and therefore so was the catch. Consequently, some near-shore cod stocks became depleted, although not those of the offshore banks.

The fishery greatly intensified during the twentieth century because of such technological innovations as the following:

• the development of more efficient netting technologies, particularly trawls and monofilament gill nets
• the use of sonar equipment to locate schools of fish
• increases in ship-borne capacity to store and process fish, which allowed vessels to stay at sea for a longer time

The improved technology allowed enormous catches to be made, particularly in the 1960s when the fishery was essentially an unregulated, open-access enterprise. By this time, unsustainably high catches were causing cod stocks to collapse (see Figure 1).

Image 14.4. Before the stocks of cod were heavily exploited, individual fish were much larger than they are today. Huge “mother cod” are now exceedingly rare. This is unfortunate because they have much greater spawning capacity than smaller cod. This photo was taken in Battle Harbour, Labrador in the 1890s. Source: National Archives of Canada.

Because the declining stocks of cod were causing an economic crisis to occur in the Atlantic fishery, in 1977 the Government of Canada declared a 320-km wide fisheries-management zone within which quotas of fish were allocated. The conservation actions resulted in short-lived increases in cod stocks and landings. However, exploitation levels were still too high, and the fishery experienced an even more serious collapse. In 1992, the federal government declared a moratorium on commercial fishing for cod, a ban that was still largely in force in 2014 (when this was written). Because only small populations of adult cod are available for spawning, the recovery of the stocks has been slow. However, if allowed, the cod may eventually recover to again be a bounteous resource.

Figure 14.3. Recent History of Landings of Cod off Eastern Canada. Note the large decrease in overall landings, and the increasing proportion of Canadian landings after the declaration of a 320-km management zone in 1977. A moratorium on cod fishing was declared in 1992, but there have been some by-catch and sporadic quotas since then. Data are in thousands of tonnes. Sources: Statistics Canada (1994) and Fisheries and Oceans Canada (2014a).

Several explanations have been proposed for the collapse of cod stocks in the Northwest Atlantic, each based on more or less convincing logic and information. The most important of these are discussed below (Freedman, 1995; Hutchings and Myers, 1995).

The hypothesis of over-exploitation suggests that the cod resource was exploited faster than it could regenerate, which caused a decline that became especially acute from the 1970s to early 1990s. The excessive harvesting was caused by several factors. Over the years, scientists had estimated the size and productivity of cod stocks and their maximum sustainable yield (MSY). The scientific information was, however, imperfect. First, it is extremely difficult to estimate the abundance of fish in the open ocean. In addition, a population model being used in the 1980s to determine stock size and to set quotas was systematically overestimating cod biomass and MSY, and that resulted in the allocation of unsustainable fishing quotas.

Moreover, politicians and other decision makers in Canada (and everywhere else) are influenced by socio-economic considerations in addition to the advice of scientists. In the context of cod, these pressures come from individual fishers, their associations, and fish companies. These interest groups all need cash flows and livelihoods, in a context where there are few alternatives to fishing for employment and revenue generation. These powerful socio-economic influences led to political decisions to set larger quotas than were being recommended by fishery scientists, a factor that has contributed to the mismanagement of cod stocks and many other resources.

Most of the Grand Banks falls within Canada’s 320-km management zone. Some parts, however, extend into international waters, where, until 1995, there was an unregulated multinational fishery. Because cod and most other marine species are mobile and do not recognize the boundaries of management zones, foreign over-fishing in international waters compromised efforts to conserve the stocks. However, between 1977 and 1991, Canadians landed about 85% of the cod caught in the Northwest Atlantic, and their fishery was being regulated. Humans are not the only predators of marine resources. The harp seal (Pagophilus groenlandicus) is the most abundant marine mammal in the Northwest Atlantic (more than 7-million). The seal population consumes about 1 million tonnes of food per year. However, this seal’s prey consists of a wide variety of species, especially crustaceans and small fish such as capelin (Mallotus villosus) and Arctic cod (Boreogadus saida). Even though the cod stocks collapsed at the same time that the seal population was increasing, the minor role of cod in their diet makes it unlikely that seals were an important cause.

Finally, some people believe that the recruitment of cod may have been somehow impaired by environmental changes, including several years of cold surface-water temperatures in parts of the Northwest Atlantic. However, there is no direct evidence to support such an environment-related cause of the collapse of the cod stocks. The simplest and most compelling hypothesis offered to explain the collapse of cod stocks is this: the valuable resource was exploited at an intensity that exceeded its capability for renewal. In other words, the cod stocks of the Northwest Atlantic, one of the world’s greatest potentially renewable bio-resources, were fished to commercial extinction.

From: Chapter 14 ~ Renewable Resources by Dalhousie University. Licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.