256 
BULLETIN OF THE BUREAU OF FISHERIES 
rate upon the density of the population might be expected. Here ordinarily it is im- 
possible for underfed fish to move to an area with more abundant food; they must 
subsist as best they can upon the food supply available within the lake. If the lake 
contains a “natural” population, a population not disturbed by any extensive re- 
moval of individuals through a fishery, then it may be assumed that in all probability 
a competition for food exists, and that this competition may in some lakes be quite 
severe. Several examples of the dependence of fish growth upon the density of the 
population have been observed in fresh-water lakes. 
The Norwegian farmers have long recognized the disadvantages of an over- 
crowded stock in trout lakes. The appearance of emaciated and undersized indi- 
viduals is taken as an indication that a more intensive fishery is desirable. Through 
the regulation of the intensity of the fishery they “keep the trout under discipline” 
(Huitfeldt-Kaas reviewed by Rugde (1923) in the Salmon and Trout Magazine). In 
another paper Huitfeldt-Kaas (1927) stated, “Very great rapidity of growth is shown 
by fish [trout] in lakes with quite small stock * * * This type of growth I think 
can suitably be termed ‘slender stock type’.” 
Surbeck (1921) stated that the decrease in numbers in the stock of the “Balchen ” 
( Coregonus schintzii helveticus Fatio) in Vierwaldstattersee following 1900 was ac- 
companied by a significant increase in individual size. 
Jarvi (1920 and 1924) was able to show that in the “kleine Marane” ( Coregonus 
albula ) of the Finnish lakes the poorest growth occurred when the fish were most 
plentiful and the best growth occurred when the fish were scarce. The fishermen 
consider the presence of large young fish in the early catches of the fishing season as an 
indication that the year will be bad. 
Pirognikoff (1927) stated that the decline of the intensity of the fishery for the 
rudd ( Rutilus rutilus lacustris Pallas) in Lake Chani and the consequent increase in 
the abundance of that form was accompanied by a distinct decline in the rate of 
growth. 
Hart (1931) found that whitefish taken in different parts of Lake Ontario showed 
different rates of growth, which he was able to explain in part by the selective action 
of the gear used in collecting the samples, but stated with reference to the slow growth 
of the fish taken at Pleasant Point, “An explanation on the grounds of detrimentally 
keen competition for food in the first years in the neighborhood of a much frequented 
spawning ground is a tempting one.” 
In his studies of the trout ( Salmo kamloops Jordan) of the Kamloops district, 
British Columbia, Mottley (1932) observed that the opening of a lake to intensive 
fishing was followed not only by a decrease in the abundance of trout but also by an 
increase in their “size for age.” He advocated that an annual determination of 
growth rates be included in the data upon which stocking policies for the lakes of the 
region are based. 
Juday and Schneberger (1933) reported the discovery of abundant populations 
of undersized smallmouth black bass in two small lakes in Vilas County, Wis. They 
considered the inferior growth of these bass as the results of a too great density of the 
populations in relation to the amount of available food. 
On the basis of experimental studies on young trout Wilier (1929) asserted that 
crowding operates as an inhibitor to growth in a manner over and above the effect 
it may have in producing competition for food. He considered this “Kaumfaktor” 
to account for the irregularities found by him (Wilier, 1924), and by Jarvi (1920) in 
