Effects of gill lice (Salmincola edwardsii) on brook trout (Salvelinus fontinalis) in lakes. (Fisheries research report: 1761)

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fish in each lake. In four lakes gill lice populations developed exponentially,
and the rate of increase was inversely related to initial number of gill
lice on fish.
Introduction
Causes of natural mortality of trout stocked in lakes have not
been definitely determined (Johnson and Hasler, 1954; Alexander and
Shetter, 1961, 1969; Eipper, 1961; Hatch and Webster, 1961; Latta,
1963). Davis (1956) states, "Small ponds... may provide so favorable
an opportunity for the multiplication and spread of copepods that they
become exceptionally abundant and may cause great mortality. " Six
small lakes at the Pigeon River Fisheries Research Station, Vanderbilt,
Michigan, have well established populations of the parasitic copepod
Salmincola edwardsii. The causes of natural mortality of brook trout
(Salvelinus fontinalis) in these lakes have not been identified (Latta, 1963).
The gill louse appeared to be a likely source of mortality. The objective
of this study was to measure the degree of infestation of the gill louse on
the brook trout and to determine the effects of this infestation on the
condition and the rate of natural mortality of the trout. A secondary
objective was to possibly identify some of the factors influencing
development of gill lice populations.
The lakes of the Pigeon River area are considered by geologists
to be limestone sinks; i. e., they were formed through the solution of
underlying limestone by groundwater, accompanied by a settling of the