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Fish Bulletin No. 21. Analysis of Boat Catches of White Sea Bass (Cynoscion nobilis) at San Pedro, California

  • Author(s): Whitehead, S S
  • et al.
Abstract

Determining the condition of a fishery is a first step in its administration. It is equally as important to learn that a fishery is withstanding a strain as to know that it is being overexploited. If depletion is evident, legislation should be passed to give protection. When the status of a fishery is in question the length of time taken to determine this status is a big factor and the administrator should be advised in the least time possible whether or not protection is necessary. By using the method of determining the return per unit of effort expended as a criterion these needs are met; provided statistics over a long period of years have been collected to give the return per unit of effort. In California the Bureau of Commercial Fisheries of the Division of Fish and Game has been gathering statistics since 1918 for analyses of its fisheries. By legal requirement the fish buyer records the amount of each species purchased, port of delivery, price, fisherman's name, boat name, boat number, and the date. This record is made out in triplicate in a receipt book issued free of charge by the Division of Fish and Game to all fish buyers. The fisherman's copy is a white receipt, the buyer's yellow, and that of the Division of Fish and Game pink (known as the "pink ticket"). These pink tickets provide the required data for a catch analysis when the catches are the product of one day's fishing. When the catches are the product of more than one day's fishing, the pink tickets are apt to be inadequate because the unit of effort frequently fluctuates. In a fishery where the catches are landed each day, the unit of effort will be one day's fishing, and the amount of fish caught will be the return. As this method of determining increase or decrease of return per unit of effort is a comparison from year to year, it is necessary that the unit of effort remain constant. This means that the gear of the boat as well as the time interval must remain unchanged throughout the period of investigation. The question as to the condition of the population of white sea bass, Cynoscion nobilis, a species of the Croaker family, has been brought to the attention of the Bureau of Commercial Fisheries. As it is the function of the California State Fisheries Laboratory of the Division of Fish and Game to determine the condition of the commercial fisheries of California, the following investigation has been pursued.

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