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Open Access Publications from the University of California

Fish Bulletin No. 24. An Analysis of the Catch Statistics of the Striped Bass (Roccus lineatus) Fishery of California


In order that the owners of a fishery or any other natural resource may derive the greatest benefit from that resource, it must be utilized to the fullest possible extent. A policy of unwarranted restriction or miserly hoarding does not give the maximum benefit to the owners, since they then are deprived of their legitimate profits. Nor does a program of wasteful extravagance produce the greatest possible good from a fishery. Indeed of the two courses the latter is the more unwise and harmful, since the resource may be reduced to such an extent that it is either obliterated or brought to a level so low that it can no longer produce profitable returns. Therefore, the persons administering a fishery are confronted with the problem of getting the greatest possible returns from the resource, without harming the supply or breeding stock. There appears to be no method by which it is possible to determine how large a catch a fishery can produce without injury to itself, until depletion becomes apparent at least to a small extent. It would seem then that the only course remaining is to proceed to utilize cautiously the fishery, endeavoring to keep on the safe side so that depletion will not occur. Then if it is evident that the resource is being injured by over-production, either the supply must be increased artificially or the total take reduced. Evidently then in conjunction with this method of trial and error, it is necessary to have some means of judging the point at which a state of injurious over-production is reached, in order that some remedy or regulation may be applied before the breeding stock of the fishery is depleted seriously. Probably the most common method in the past of judging the condition of a fishery has been to accept the opinions of people working or interested in the resource as evidence in the case. These opinions are usually of doubtful value, since depletion must proceed to an advanced stage before it becomes apparent to the casual observer, and it is then often too late to save the fishery. Also people deriving their sport or living from a fishery are apt to be prejudiced and their opinions biased or founded on a few observations of outstanding instances. Figures showing the annual total catch of a species of fish are also often used as a basis for judging the relative abundance of a fish. When such data are used without careful analysis and other supplementary information, as is often the case, they are usually without value and often misleading. This is necessarily so, because the abundance of a fish is only one of many factors which ordinarily cause fluctuations in the total take of that species. The total catch may remain constant or even increase while the species of fish is being depleted. Such a situation can be readily brought about by the effort expended on the fishery, number of men and boats, being increased, new and more productive fishing grounds being opened up, or a more effective type of gear coming into use. An increase in fishing effort may be caused by higher prices, failure of another fishery making it necessary for fishermen to change over to the one in question, or a greater demand offering opportunities for more men and boats. Likewise a drop in total catch might occur when the supply of the species is holding its own or increasing. This may be caused by a decrease in fishing effort, legislation preventing use of effective gear or good fishing areas or fixing closed seasons, which diminish the available fishing time. Unfavorable weather or strikes of fishermen also may pull down the total catch for a brief time. Therefore, since the total amount of any species taken in a calendar year is dependent on several factors other than the relative abundance of the species, namely: fishing effort, legislation, shifts in fishing grounds, weather, changes in another fishery, labor and economic conditions, some method of treating the catch figures, which will eliminate as nearly as possible factors other than abundance must be resorted to in order to secure any dependable index of abundance from the catch data. By expressing catch returns in some definite unit which is subject as little as possible to influence by factors other than abundance, such a desired result may be accomplished. The catch return per a constant amount of fishing effort, gear and time, is such a unit. In other words the catch resulting from a constant amount of fishing gear and effort used for a constant period of time should be indicative of the relative abundance of a species of fish, or at least the availability of the species to the fishermen, providing the data used are representative samples of the catch results from the entire fishery. It is reasonable to assume that as a species of fish becomes less abundant, the same amount of gear employed in the same manner and for the same length of time will catch a lesser quantity of the fish as the supply decreases, or more fish as the supply increases.

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