Fishery And Survey Data example essay topic

ABSTRACT The outstanding features of the Peru upwelling system are high productivity and great variability. No large changes in the parameters of the anchoveta population were detected in the fishery and survey data analyzed in studies done before 1972, but because of deficiencies in the data such changes may have occurred and gone undetected. These studies might have been adequate in a less variable fishery, and even in the anchoveta fishery were useful in that they prevented an excessive increase in fishing effort. But because they did not allow for the possibility of large changes in the behavior of the population, they were of little value when recruitment failed in 1972. The stock's collapse in that year and its apparent failure to recover since are still not understood. In the light of this experience, future studies and management of anchoveta fisheries should take into account the potential for large changes in the parameters of the fish populations and in the meaning of the usual fishery statistics and survey data.

INTRODUCTION Because of upwelling, the coastal waters of Peru are among the world's most productive. The chief direct consumer of this immense planktonic production is the Peruvian anchoveta, Engraulisringens Jenyns, and it in turn is the chief forage item of the region's higher level consumers, including fish, birds, and marine mammals. In some years the normal processes of production and consumption are interrupted when upwelling ceases and warm surface waters advance to the coast with lethal effects on the native biota, a phenomenon called El Nino. In the absence of a large market, no large scale fishery developed to exploit Peru's marine production until the second world war, when high demand and low supplies in the United States and elsewhere offered large profits from the export of canned tuna and bonito. After the war, as normal fishing operations resumed in the former belligerent countries, Peruvian exports were steadily displaced from foreign markets by cheaper domestic products, and in Peru the boats and factories that had been built during the war were increasingly idle. Reduction plants had been installed in the canning factories to make fish meal from the leavings of the canning process, and beginning about 1950 some factory owners resorted to buying anchoveta for reduction to cut their losses when the canning lines were idle.

This incidental activity soon became profitable in itself as world demand for fish meal increased and other supplies declined, in particular the California sardine. As new boats and plants entered the industry, the catch of anchoveta grew exponentially, doubling each year from 100, tons in 1955 to 3.3 million tons in 1960 (Boere ma andGullard, 1973). At this point the Peruvian government, with technical assistance from the Food and Agriculture Organization of the United Nations (FAO), began to collect fishery statistics and conduct fishery investigations with the aim of rationally managing the resource. The first assessment of the fishery, done in 1965, showed that the stock was fully exploited, or nearly so, by the current annual catch of 8 million tons, and for the next few years the catch was limited to approximately this amount by closed seasons and quotas. Later studies, done after the population offish eating birds had been reduced by some 75%during the 1965 El Nino, showed that the anchoveta stock could yield 10 million tons per year on the average. The quota was consequently raised in 1968, and the annual catch was around 10 million tons through 1971.

While the annual quotas prevented excessive increases in the catch, they did not prevent and in fact encouraged excessive increases in the industry's capacity (catching and processing) since the companies with the largest capacities obtained the largest shares of the quota. As a result, the industry by 1971 was heavily overcapitalized. At the end of 1971, the anchoveta fishery appeared to be a model of successful management, by biological standards if not economic ones. But then, within months, the population suffered two catastrophes. First it became clear early in 1972 that recruitment had practically failed, and after that the adult stock, crowded against the coast by the severe 1972 El Nino, was greatly depleted, either by heavy fishing or by a combination of heavy fishing and extraordinary mortality due to the extreme environmental conditions that then prevailed.

Bythe middle of 1972 only a small part of the former stock appeared to have survived. The stock of anchoveta did not recover rapidly after the collapse of early 1972, and since then the fishery has operated at a low level. After catching about 4.5 million tons in the first months of 1972, the fishery in effect remained closed until March 1973 when about 2 million tons were caught during a brief open season, but acoustic surveys and the composition of the catch showed that recruitment.