Effect of food on the growth of carcase, liver and ovary in female Gasterosteus aculeatus L.

The effect of ration size on the growth of the carcase, liver and ovary in female three-spined sticklebacks, Gasterosteus aculeatus L., was studied experimentally at monthly intervals throughout the annual reproductive cycle. Temperature and photoperiod during each experiment corresponded to the average, natural conditions for that month.
Growth of the carcase was sensitive to ration in all months. At a given ration, the growth rate of the carcase was relatively constant. The water content of the carcase was inversely correlated with ration size. Growth of the liver was also sensitive to ration, but the sensitivity varied in different phases of the reproductive cycle. High rates of weight loss occurred in the liver under starvation, but at maximum rations the liver showed high rates of weight gain particularly in the post-spawning period. Growth of the ovary was relatively insensitive to ration but directly reflected the changes occurring naturally in the reproductive cycle.
It is suggested that the liver acts as a buffer between the carcase and the ovary and this helps to insulate the ovary from the immediate effects of fluctuations in food supply.
The growth rates of the carcase and liver may provide useful indices of the rate of food consumption in natural populations. Although, if the liver is used, its growth has to be interpreted in the context of the annual reproductive cycle.