Wars and fish stocks

During the first half of the twentieth century the fisheries of the north-east Atlantic were twice interrupted by war. Conditions on some of the major fishing grounds visited by British vessels have fluctuated correspondingly, with symptoms of underfishing during war years and severe overfishing in peacetime. For example, the North Sea provides an important fishery for haddock. During the years prior to 1914, the total landings of haddock from this area showed a fairly steady decline. During the period of the 1914-18 war, fishing in the North Sea was greatly reduced. When normal fishing was resumed after the war, greatly increased yields were at first obtained, amounting to approximately double the pre-war landings, but during subsequent years the catches gradually diminished. By the later 1930s the annual landings of haddock had fallen below their pre-1914 level to about a quarter of their 1920 weight.

During the war of 1939-45, fishing in the North Sea virtually ceased. When normal fishing was re-established, there was at first again a marked increase in haddock landings, but subsequently the yield of the fishery again fell (Figure

These diminishing peacetime yields have not been the result of any reduction of fishing effort, rather the reverse. Furthermore, as the yields decline the percentage of the catch consisting of small fish shows a great increase (Figure

Figure 9.26 Haddock catch per unit of fishing effort by Scottish trawlers in the North Sea.

------Landings per days absence from port; ——- Landings per 100 hours.

(From Graham, M. (1956), by courtesy of Edward Arnold.)

Figure 9.26 Haddock catch per unit of fishing effort by Scottish trawlers in the North Sea.

------Landings per days absence from port; ——- Landings per 100 hours.

(From Graham, M. (1956), by courtesy of Edward Arnold.)

Years

Figure 9.27 Catch, per unit of fishing effort, of North Sea haddock, and percentage of the 'small3 category, 1923-38. O—O large; X— X medium; •—• small; □-□

percentage 'small\

(From Graham. M. (1956), by courtesy of Edward Arnold.)

Years

Figure 9.27 Catch, per unit of fishing effort, of North Sea haddock, and percentage of the 'small3 category, 1923-38. O—O large; X— X medium; •—• small; □-□

percentage 'small\

(From Graham. M. (1956), by courtesy of Edward Arnold.)

c i i i i I i i i i_' I ' ' ' i ■ ' ' ' ' I '_i i i_i i i_i_i i i

1906 8 10 12 1/, 1920 22 24 26 28 30 32 34 36 38 1946 48

Years c i i i i I i i i i_' I ' ' ' i ■ ' ' ' ' I '_i i i_i i i_i_i i i

1906 8 10 12 1/, 1920 22 24 26 28 30 32 34 36 38 1946 48

Years

Figure 9.28 Catches of North Sea plaice by first-class English steam trawlers. (From Wimpenny (1953), by courtesy of The Buckland Foundation.)

cn 60 c

Length groups(cm)

Figure 9.29 Size distribution in plaice landings at Lowestoft before and after World War II. □ 1938 m 1946.

(From Wimpenny (1953), by courtesy of The Buckland Foundation.)

Length groups(cm)

Figure 9.29 Size distribution in plaice landings at Lowestoft before and after World War II. □ 1938 m 1946.

(From Wimpenny (1953), by courtesy of The Buckland Foundation.)

In the plaice fishery, comparable changes have occurred (Figure 9.28). The largest sizes of plaice in the North Sea have only been abundant in immediate post-war years, and since then the catch has consisted mainly of small fish (Figure 9.29). Although the total weight of plaice landed from the North Sea has remained fairly constant over the first half of this century, the effort and expense of catching them have greatly increased, i.e. the yield per unit of fishing effort has become less. During the 1960s there was some reduction of fishing for plaice in the North Sea because of poor returns. Attention turned to other species and some old vessels were laid up and not replaced. Consequently there was some recovery of plaice stocks in the late 1960s and landings considerably improved.

In normal peacetime operation, plaice and haddock fisheries of the North Sea have therefore shown major features of overfishing, namely, declining yields and a preponderance of small fish. Similar trends have been observed in many areas for such important species as cod, plaice, haddock, halibut and hake.

The war years, on the other hand, produced some symptoms of underfishing. The stock of fish increased greatly, and this was reflected in the heavier catches obtained when fishing was resumed. These early post-war catches contained a high proportion of large fish of the older age groups, but some were diseased and of poor quality. In the case of plaice, there is some evidence that the stock increased to such an extent that the average growth rate of the fish was reduced, presumably by food shortage.

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