Seasonal variation in direct and indirect measures of energy status was examined using estimates of glycogen, lipid and protein levels in a single cohort of male three-spined sticklebacks from an annual population collected each month over one complete year. Condition factor, somatic condition factor and hepatosomatic index (HSI) were calculated as indirect indices of energy status and the accuracy of these indirect measures as predictors of energy status was investigated. Results indicate that both condition factors were significant predictors of energy reserves (lipid, protein, glycogen and total energy), but that the proportion of variance accounted for was small. Both condition factors perform better as predictors of energy content per unit body weight. The HSI was a significant, but a weak predictor of total glycogen levels over the whole year. On a seasonal basis the relationship between HSI and energy reserves was highly variable. These indices are therefore poor predictors of energy reserves in male three-spined sticklebacks. '(', 1995 The Fisheries Sociely of the British Isles

Wet and dry weights of tissue were measured and concentrations of glycogen, lipid and protein were estimated for the liver, gonad and carcass of male sticklebacks from an annual population collected each month over one complete year. In young-of-the-year there is one period of rapid weight gain, in all three body regions (liver, carcass and gonads) but particularly of the carcass, in the autumn and a second in spring and early summer. This is accompanied by an increase in the water content of all three body regions. The gonadosomatic index also increases sharply in spring and early summer. Young sticklebacks accumulate lipid and glycogen slowly during the autumn and winter of their first year of life and more rapidly from late winter to early summer. Thus, the period of most rapid accumulation of these reserves coincides with the time when body weight and gonad maturation are also increasing sharply. Lipid and glycogen levels fall during the reproductive season in those males that breed? so that by July they are reduced to 43% and 37% (respectively) of their peak values in May. Levels of protein increase throughout the year as the fish grow, but in breeding males by July the concentration of protein in the carcass falls to 70% of pre-breeding levels. Breeding males therefore reach the end of the reproductive season with their total energy reserves severely reduced, and consequently they suffer a very high mortality. In contrast, adult males that fail to reproduce survive beyond the breeding season. They continue to gain weight and to accumulate lipid and glycogen from August to September, but these. energy reserves fall (to levels comparable to those of post-breeding fish) in December, when these fish probably die. These results demonstrate that in male sticklebacks, growth and gonad maturation can be sustained in parallel with the accumulation of energy reserves, which are subsequently extensively depleted as a result of reproductive activities.

I953 activity of diphosphopyridinenucleotidase is greatly increased (Nason et al. 1951)-there is no reason to attribute invariably the disorders of metabolism which occur in zinc deficiency to a primary impairment of protein synthesis. Copper deficiency has been claimed to have marked effects on the protein metabolism of green plants (Gilbert, Sell & Drosdoff, 1946; Wood & Womersley, 1946; Lucas, 1948; Gilbert, 1951), and so the observation that the aldolase activity in the leaves of copper-deficient oats remains unimpaired, suggests that the lowered aldolase activity in the leaves of zinc-deficient oats is not due primarily to a decreased protein synthesis; although zinc might be specifically involved in the synthesis of the enzyme itself. The third possibility that the aldolases of green leaves are activated by Zn2+ or by zinc-containing co-enzymes is being examined. SUMMARY Aldolase activity was found to be materially decreased in tissue suspensions prepared from the leaves of zinc-deficient plants of Trifolium subterrane,um and of Avena 8ativa, but was unchanged by copper deficiency. The author is grateful to K. Powrie for supplying some of the experimental material: to G. B. Jones for the polarographic estimation of zinc and copper and to V. Stephen who set up the aeration apparatus and is particularly indebted to H. R. Marston, F.R.S., Chief of the Division of Biochemistry and General Nutrition, C.S.I.R.O., for his advice and criticism during the experiment and his help in preparation of the manuscript. Glasshouse accommodation was made available by Prof. J. G. Wood of the Botany Department of the University of Adelaide, and this courtesy is gratefully acknowledged.

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