PERCENT OF MAXIMUM CATCH OR YIELD in the catch gives an estimate of the rate at which the fishery is removing fish. Tags were recovered at a greater rate in 1961 than in 1960, and have been recovered at an even greater rate so far in 1962. This confirms other evidence that the rate of fishing is increasing, and it also shows that the fish have not moved elsewhere. If an important part of the stock had moved beyond the range of the fishery, fewer tags, rather than more tags, would have been recovered. The condition of yellowfin tuna stocks also has been examined by studying changes in the death rate of fish. Once they reach a size large enough to be caught in the fishery, yellowfin are subject to a fairly constant rate of natural mortality (deaths caused by enemies, parasites, diseases, etc.). Fishing adds another cause of death (called fishing mortality by fishery scientists), and as the rate of fishing increases, so does the total death rate. When death rate increases, the average age of fish in the population decreases. This causes a decrease in average age and size of fish in the catch. The average size of yellowfin in the 1961 catch was decidedly less than in 1960. All these facts confirm earlier estimates that the maximum sustainable annual catch of yellowfin tuna in the eastern tropical Pacific is about 97,000 tons. There is abundant evidence that the stock has been overfished in 1961, so that yellowfin tuna in the eastern tropical Pacific have been reduced to a level of abundance at which they can no longer sustain an annual yield of 97,000 tons. At the present population size, it has been estimated that the sustainable yield is 10,000 tons less than this. If the population is reduced still further, as it will be under the present intense fishery, the potential annual catch will be even lower. The only practical solution is to place a limit on total catch. If the maximum sustainable yield of 97,000 tons a year is to be restored and maintained, we must restore the depleted "principal" by allowing more fish to accumulate. The Commission has recommended that this be achieved in several steps, and has proposed a total quota for all countries of 83,000 tons in 1962. This ends my testimony, Mr. Chairman. I will be glad to answer questions if the committee so desires. FISHING INTENSITY (Thousands of Fishing Days of a Class 4 Clipper) Dr. McHUGH. I am Dr. J. L. McHugh, Chief of the Division of Biological Research in the Bureau of Commercial Fisheries, and as Mr. Bennett and Mr. Herrington have already told you, I am also one of the three U.S. Commissioners on the Inter-American Tropical Tuna Commission. The original recommendation that proposed regulation of the tuna fishery in this area of the ocean was made at a special meeting of the Commission in Long Beach, Calif., on September 14, last year, and at the meeting last week in Quito, this recommendation was reaffirmed. As far as the Commission's scientific staff is concerned, as early as 1957 it was recognized that there is a rather definite limit to the total catch that the yellowfin tuna resource can sustain. I would like to refer you, Mr. Chairman, to the chart on page 5 of my prepared report. You will notice two lines there, the line joining the black dots represents a typical fishery in which there is a maximum yield somewhere at an intermediate level of fishing intensity. That is, when fishing intensity is very low it is quite obvious that the fishery is not able to take all the fish that it possibly could. But at a certain level the theory of fishing says that the maximum sustainable yield can be taken, and beyond that point, if the fleet fishes harder, then the sustainable catch begins to go down, and the fleet can no longer make the maximum possible catch. This is one possible situation for the yellowfin tuna stocks in the eastern tropical Pacific. The other is represented by the curve which connects the open circles. This is the type of situation, as we say in fishery science, in which the stock is density independent. That is, within rather broad limits, no matter how few or how many tuna there are in the ocean the number of young produced each year is about the same. You will notice that both these curves reach a maximum at about the same place, and this maximum is at a level of about 35,000 standard fishing days. Standard fishing day is simply a fishing day rated according to a certain type of tuna clipper. This is done in order that the fishing operations of different kinds of boats can be comparable. So, this chart shows that at about 35,000 standard fishing days the maximum sustainable yield would be obtained from this resource whether the annual supply of young depends on the numbers of adult spawners present or not. Now, of course, there is a difference between these two curves, but you will observe that both of them fall off beyond that point of 35,000 fishing days. There would be a decline in the sustainable catch if fishing becomes any more intense. Now, let's look at the next chart on page 6. This shows the same curve that was shown in the previous chart, the dotted line that runs in the center of the other two more or less parallel dotted lines represents that curve. And superimposed on it are numbered points which represent the catches and the levels of fishing intensity in a whole series of years dating back to about 1934. This covers the entire history of the fishery as we know it in scientific terms, and you will see that these points, though they stray a little bit from the line, follow this curve rather closely and in general the pattern of the fishery has followed quite closely, in fact remarkably closely, the principle on which the management of the stock has been based. The departure of these points from the lines simply represent variations in the availability of fish to the fleet through various causes, probably slight changes in the success of spawning from year to year, and a certain amount of error in our ability to measure these numbers exactly. Now, of course, these curves show you that it is possible, by fishing hard enough, to catch more fish than the scientific staff of the Commission has predicted as the maximum yield that could be sustained year after year. But it is possible to do this only by taking away from the stock the catch that you might make in later years; in a sense, removing money from the "bank" on which the industry is drawing "interest," when you consider that money in the "bank" in terms of this analogy is the stock of spawning yellowfin tuna in the sea, and the "interest" is the crop of new fish that each year reaches commercial size. The Commission has determined that as the shift from bait fishing to purse seining has come along, as previously described by Mr. Herrington, in 1960 the amount of fishing effort put forth was just almost exactly the amount that the Commission has determined is the amount of fishing necessary to produce the maximum sustainable yield. The Commission also has determined that in 1961 this amount of fishing had increased from about 35,000 standard units to almost 42,000almost a 20-percent increase in the amount of fishing effort that the fleet was able to exert. And this has removed from the ocean some of the yellowfin tuna that should remain as a reserve, as a deposit in the "bank" to produce new crops of young year after year. Now, if this condition goes on without regulation, it is the prediction of the scientific staff that the yellowfin tuna stock will decline in abundance. Eventually probably it would decline to the point where it would no longer be profitable to fish yellowfin for itself alone. The yellowfin catch then probably would become just an incidental catch made while the fleet went out fishing for skipjack tuna. This attrition, this steady incidental catch of yellowfin at that stage of the history of the stock, probably would be sufficient to hold the stock down at a very low level and the fishery would not be reaping the maximum annual harvest that it could under a properly managed fishery. Now, to correct this situation the recommendation has been that it will be necessary not only to hold the catch to a certain level but to reduce it somewhat below that level in order to, as it were, put money back in the "bank," to allow the stock to accumulate back to its maximum level. And so, rather than limit the catch to the level of 97,000 tons which has been determined as the optimum yield that can be produced year after year, it is necessary to cut it down to a lower level; namely, the figure of 83,000 tons that has been recommended by the Commission. This will gradually allow the stock to accumulate and bring it back to its maximum productive level. I think all I need to emphasize in addition, Mr. Chairman, is to repeat that the committee last week reaffirmed its 1961 recommendation and recommended a quota of 83,000 tons in 1962. This ends my testimony, Mr. Chairman, and I will be very happy to answer questions. Senator BARTLETT. Thank you for your statement, Dr. McHugh. How long have you been on the Commission? Mr. McHUGH. I have been a member of the Commission for about a year and a half. I was appointed by President Eisenhower in 1960. Senator BARTLETT. Your resignation has not been requested under the new administration? Mr. McHUGH. When the new administration came in I submitted my resignation, Mr. Chairman; it has not been recognized. Senator BARTLETT. I inferred that it had not or else you would not be here in your capacity as a member of the Commission. Will you tell us something for the record about the life of the yellowfin tuna? Mr. McHUGH. Yellowfin tuna in this particular area spawn reasonably close to the coast. As far as we know they perform rather extensive movements up and down the coast in a northerly-southerly direction, but they do not move very far offshore. Dr. Scheafer has, by tagging, shown that they don't migrate very far to the westward because all the tag returns he has received back from the fishery have come from the fishery in the eastern tropical Pacific. He has had no returns from the Japanese fishery, no returns from the western part of the Pacific at all. The fish when they enter the fishery are about 12 years old and at this time they weigh about 712 or 8 pounds. Most fish die by the end of their fourth year. They are a rather short-lived and rapidly growing fish; average weight at 4 years is about 134 pounds. So, you see, they grow very rapidly after their first year. Senator BARTLETT. The average weight after 4 years is 134 pounds, and the average weight at the end of the first year is about what? Mr. McHUGH. Seven and a half pounds. Senator BARTLETT. At what age are they considered best for human food purposes? Mr. McHUGH. Anywhere from 711⁄2 pounds up. They are taken in the fishery and used from that size up. It has been demonstrated that if the fishery were to be regulated in some way to increase the average age of first capture the maximum sustainable yield could be even higher than the 97,000 tons that is predicted now, but there is no practical way of doing this. Senator BARTLETT. Why? Mr. McHUGH. Well, one way of doing it would be by a mesh size regulation, but this would be very difficult because it is impossible to achieve a sharp cutting off point for the catching of fish of a certain size. Nets, even though they have large meshes will catch numbers of small fish that should pass through the meshes. Moreover, an increase in the mesh size would allow many skipjack to escape, for these tuna are smaller than yellowfin. Senator BARTLETT. Is the Commission addressing itself to this very point which seems to a layman like myself to be of supreme importance, the loss is considerable if you take a fish that weighs 7 pounds as against one that might weigh 120 or more? Mr. MCHUGH. This is true, this doesn't mean by any means that all fish are caught at 71/2 pounds. Senator BARTLETT. I understand, it might be anywhere in between. Mr. MCHUGH. Yes. The Commission has considered the matter of raising the size at first capture but has determined that the means of achieving this objective would be so difficult and so costly to the |