The first method (no fishing by anyone for part of the year) or "single quota" system is at present the most widely used form of control in international fisheries. Since it is often associated with a predetermined catch quota (e.g. in Antarctic whaling, or yellowfin tuna in the East Pacific), it has sometimes been treated as being identical with control in terms of catch rather than effort. In principle, there is no reason why the single quota should not be defined in effort units - e.g. the quota for the yellowfin might be set at an effort of 30,000 standard days, rather than at a catch of 100,000 tons, fishing stopping when the effort quota is expected to be reached. Conversely, as discussed below, the amount of fishing can be controlled in terms of catch without necessarily involving a single quota system.
The system has some clear advantages. It is non-discriminating - or at least if there is discrimination, e.g. giving some advantage to those who can get the bigger share of the quota while the season lasts, the regulatory body is not explicitly involved in making a discrimination, i.e. between those who can fish, and those who cannot, or in determining the share of those who can. It is also comparatively easy to enforce. During the open season there are no restrictions, and there is little incentive for the misrepresentation of total catch, or other statistical data - e.g. of fishing effort, or exact location of catch, both of which are important elements for scientific study of the stocks. A complete prohibition of fishing during the closed season is much easier to police than a partial closure, with fishing permitted to only certain fishermen. It is even easier if the number of landing places is restricted, and the control is expressed, in terms of landing rather than catching. Thus the season for the yellowfin tuna is in terms of landing as a function of sailing date - those vessels sailing before the closing date can land unlimited yellowfin, those sailing later can only land small quantities of yellowfin (up to 15%) among their catches of skipjack or other unregulated tunas. There is no limit to the period or amount of fishing by the first group, until they have filled their holds, and land the fish; nor is there an explicit control of fishing by the second group, provided they land no more than 15% yellowfin; the timing of the end of the open season takes these two elements of yellowfin catch into consideration. On the first appearance the enforcement of the regulations needs no more than routine inspection of the landings, but there are two complications, both of which are examples of general complications arising in any application of the method.
The first concerns fishing for yellowfin tuna outside the area covered by the regulation. Unless fish from the two stocks can be clearly distinguished on the fish market (and ultimately perhaps in a court of law) the landings of fish outside the open season are not evidence of a breach of the regulations. Undoubtedly, fishermen wishing to fish in the closed season will be tempted to do so and claim that the fish came from outside the regulation area. Thus there has been a large rise since regulations were introduced by I-ATTC in yellowfin catches reported to have come from the western region just outside the Commission regulatory area. Of course some, or indeed possibly all, may truly be taken by vessels moving to these unregulated stocks, though a degree of deliberate misreporting is very likely. Unless all stocks of the same species can be adequately managed by the same closed season, some enforcement and inspection at sea - which adds greatly to the administrative costs - is therefore inevitable. In the case of the I-ATTC these costs are passed to the fishermen by requiring them to carry an independent qualified navigator as observer if they wish to fish yellowfin west of the regulated area. However, the management requirements of separate stocks are unlikely to be the same; for instance, the surface living shoals of yellowfin tuna are heavily exploited in the East Pacific, becoming heavily exploited in the Atlantic, but are as yet almost untouched in the Indian Ocean. A lack of balance between the exploitation of different stocks is likely to be increased by a single closed season; as this becomes shorter the attraction of the grounds nearer port (allowing more trips within the open season) become greater. The stocks on nearer grounds thus become increasingly over-exploited, while those further away are neglected. In the Pacific halibut fishery this process has occurred and has been countered by a more complex regulatory season, involving different seasons for different grounds.
The other complication concerns other species which may he caught simultaneously, or with the same gear, in the regulation area, e.g. skipjack tuna in the I-ATTC regulatory area. The problem of joint regulation of several stocks is discussed in detail later, though it may be noted here that only rarely can a species he considered in isolation. The I-ATTC is concerned with obtaining the maximum sustainable yield of all tunas - not with that of yellowfin alone (the question of whether in any case the maximum sustainable yield is or is not a proper objective of management is not discussed here). Therefore, the Commission has failed to reach its objective so long as the skipjack stock (or stocks) remain under-exploited, even if the maximum yield of yellowfin is being achieved; regulations to maintain the yellowfin catch at the desired level at best only partially serve the Commission's objectives if they tend to inhibit increased fishing of skipjack (so long as skipjack remain under-exploited). Specifically fishing skipjack should be allowed during the closed season for yellowfin.
Inevitably, since the species may be mixed, or misidentified in the water, some yellowfin will be caught while fishing for skipjack. If these cannot be landed, they will be wasted, since few if any will survive if dumped back into the sea - also the incidental catches of the higher priced yellowfin make the skipjack fishery more attractive. Therefore, a certain percentage of yellowfin has bad to be permitted - similarly a percentage of "protected" species (cod, haddock) are allowed in the North Atlantic trawl fisheries for herring, etc., using a mesh size below the normal regulation minimum size. Based on observations in the pre-regulation period a limit of 15% yellowfin was set. The result has been that most fishermen have, in order to maximise the value of a load, set this as a normal target, catching yellowfin up to 15% of their total capacity early in their trip. Inevitably some more yellowfin are taken later in the trip and have to be dumped and wasted. Some measure of the extent of this was reported at the 1969 meeting of I-ATTC, when the dumping in 1968 was stated from log book records to have been appreciably greater than in 1967. Only exceptionally are the interests of the management in the regulated species given high priority over the development of the fisheries of other species. One exception is the Pacific halibut; not only are there restrictions on the gear used in halibut fishing (only long-line), but there is a prohibition on landing halibut caught incidentally in other gears. Halibut are tough fish, so that discarded halibut may survive, especially if returned to the sea quickly, though to what extent this is done in commercial practice is uncertain.
A major economic disadvantage in a single quota system is that there is no control of the size or fishing capacity of the fleet. (Fishing capacity may be defined, in the sense used here, as the fishing mortality that could be exerted by a fleet of vessels if it operated without restriction). If the regulations achieve their objective in increasing the stock and the catch rates, and so make fishing more profitable, additional ships will be attracted into the fishery. The enlarged fleet will reach the desired catch quota more and more quickly, so that the open season becomes shorter and shorter. This effect, readily predictable in theory, has been observed in most fisheries where a single quota system of regulation has been used - e.g. the Antarctic baleen whaling, where, prior to the agreement on the division of the quota, the season had been reduced rather steadily from 121 days in 1945/6 to 58 days in 1955/6. More recently, in the first three years of effective regulations of yellowfin tuna fishing in the East Pacific, the length of the open season has been reduced to 3½ months.
This shortening of the season will add to the costs of fishing. The extent will depend on the relative magnitudes of the different costs - capital costs of ship and equipment; running costs; and crew costs - an also on the degree to which some of the fixed costs can be spread over alternative operations during the closed season. For instance, there is little alternative for whaling ships, but tuna vessels can fish for skipjack or move to the Atlantic and fish for yellowfin there.
The long-term result will be that costs will rise with the shortening season until a new equilibrium position is reached, as before regulation, in which the costs of fishing are equal to the value of the catch, and the potential economic benefits of the regulation are lost. Therefore, if the economic benefits are to be obtained the alternative system - preventing some people from fishing for all the time - need to be considered, either as the sole method of regulation, or as a modification to the simplest form of single quota system.