Fishery bulletin of the Fish and Wildlife Service - NOAA

PART II
FLUCTUATIONS IN THE PRODUCTION AND ABUNDANCE OF WHITEFISH
AND IN THE INTENSITY OF THE WHITEFISH FISHERY IN THE STATE
OF MICHIGAN WATERS OF LAKES HURON AND
MICHIGAN, 1929-1939
INTRODUCTION
In the proper administration of commercial fisheries it is of primary importance
to have at hand statistical data that afford a reliable indication of changes in the
abundance of the commercially available stocks of the leading species. These data
must include a record not only of the quantity of fish taken, but also of the extent of
the fishing operations that led to the reported catch. Obviously, a decrease in production
cannot be held with certainty to represent a depletion of the stock unless it
can be demonstrated that this lowered yield has not resulted from a reduction of
fishing intensity. On the other hand, an increase in catch with its suggested danger
of possible overfishing may not be the result of an expansion of fishing activities but
may originate in an increase in the abundance of fish on the grounds. Nor can it be
said that a sustained production over a period of years demonstrates a corresponding
stability of abundance, for abundance may decline or increase greatly while compensating
fluctuations of fishing intensity hold the total catch at a nearly constant level.
The true condition of the fisheries, therefore, cannot be measured accurately by statistics
of catch alone, but should be expressed in terms of production in relation to fishing
intensity, that is, catch per unit of fishing effort.
It was with a view toward obtaining complete and reliable information on the
fisheries of the Great Lakes waters under the jurisdiction of the State of Michigan that
the senior author devised and recommended to the Michigan Department of Conservation
the monthly report system now in effect. Under this system all licensed commercial
fishermen must submit each month a complete record of their daily fishing activities.
The required data on each day's fishing include: fishing locality; kind and amount of
gear fished; the length of time (number of nights out) stationary gear fished before
it was lifted; and the catch in pounds of each species taken. From these data it is
possible to determine both the yield and the intensity of the fishery.
The law requiring the submission of monthly reports became effective in September
1927. The early returns were incomplete and the individual reports were often faulty.
By the beginning of 1929, however, the fishermen had obtained sufficient experience in
making out their reports so that almost all returns contained the complete data necessary
for statistical analysis. These records for the 11-year period, 1929-1939, comprise
the basic materials on which part II of this paper is founded.
METHODS OF ANALYSIS
Methods proposed for the analysis of Great Lakes fishery statistics were described 4 ,
by Hue and Duden (1933). 15 In general, the procedure outlined in this publication has.
proved satisfactory, although subsequent experience has shown certain simplifications-,
of the original methods to be valid. (See discussion under "Units of Fishing Effort" in
this section.) As an addition to the original procedure, methods have been devised fora
more precise statement of changes in abundance and fishing intensity.
STATISTICAL DISTRICTS
Statistical tabulations and analyses have been made separately for six areas in
Lake Huron and eight in Lake Michigan. (The boundaries of the different districts
are indicated in the accompanying chart, fig. 4.) It was attempted to make these dis-
i> Hue Ralph and William R. Duden. Method: for the Investigation of the Statistics of the Commercial Fisheries of the Great Lakes Trans
Am. R»h. Soc., vol. 63, 1933, pp. 292-305.
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