Seasonal Changes in Bluegill Metabolism1
Authors: WOHLSCHLAG DONALD E. , JULIANO AND ROGELIO O. 
Published: March 2010

A one‐year study of bluegill metabolism in a California reservoir indicated that field determinations of oxygen uptake rates and multivariate analyses of results with respect to weight, activity, and temperature during each season were feasible in the form,

urn:x-wiley:00243590:media:lno1959420195:lno1959420195-math-0001

where Yc is the expected log milligrams of oxygen consumed per hour, X1 is the log weight in grams, X2 is the swimming velocity in meters per minute, X3 is the temperature in degrees centigrade, and where b1, b2, and b3 are the respective partial regression coefficients. By delimiting “seasons” on the basis of thermal and related limnological characteristics, the data yield the equations:

urn:x-wiley:00243590:media:lno1959420195:lno1959420195-math-0002

The multiple correlation coefficients for these equations are highly significant as are all the partial regression coefficients, excepting the low spring b3 = 0.0069.

The weight relationships expressed by b1 are remarkably close to Krogh’s constant of approximately 0.85 except in the summer when the calculated higher rate may be due to the spawning condition of the larger fish and the post‐spawning condition of the smaller fish.

There are similar relationships of respiratory rates with respect to swimming movements over the spring, summer, and autumn seasons, but during winter it appears that relatively higher oxygen consumption is required for comparable swimming activity.

The respiratory rates with respect to temperature appear to be of the same order during spring and autumn when they are lower than in summer and much lower than in winter. The high respiration‐temperature regressions in winter, and possibly in summer, may be due to excessive spontaneous activity not reflected as swimming motion at temperature extremes.

Females during each season have higher metabolic rates than the males over the range of temperatures and activities encountered, but the differences are not statistically significant.

Groups of fish during the spawning season have higher than average respiratory rates than do single fish, other conditions being equal. Limited data suggest that social facilitation exists during the summer after spawning.

Variations in Felt Lake limnological conditions are considered from the standpoint of about a 50 per cent reduction in volume from spring to autumn, the absence of a well developed littoral zone, and the rather drastic spring to autumn and winter declines in bottom fauna and average weights of the larger fish. A comparison of the above regressions over average spring and autumn conditions reveals that metabolic rates would be about equal,

although in spring the fish grow rapidly and spawn, while in autumn and winter they lose weight. Similarly the calculated winter metabolic rates are higher at comparable temperatures than those of spring or autumn due possibly to cold adaptation.

While the potential growing season in Felt Lake would be about twice as long as that for the northern portion of the native bluegill range, the growth rates are of the same order. The biological productivity of the bluegill in Felt Lake and similar western U. S. waters is interpreted to be much poorer than in eastern areas because of the longer growing season without adequate food (especially bottom fauna) production and because there appears to be no adaptive mechanism for lowering the metabolic requirements during seasons of poor food supplies.