Horse-mackerel temperature

E.V. Ivleva (1989a) found that, during the winter, Black Sea horse-mackerel displayed increased thyroid activity. This is directly related to the intensity of energy metabolism. Other workers found enhanced growth of the follicular cells of the thyroid gland of brown trout and brook trout during periods of low temperature (Woodhead and Woodhead, 1965a,b Drury and Eales, 1968), and increased thyroxine levels in the blood plasma (Eales et al, 1982). On the other hand, Leatherland (1994) has demonstrated a close positive correlation between water temperature and the concentrations of both forms of thyroid hormone (thyroxine and tri-iodothyronine) in the plasma of brown bullhead. 

The hexose monophosphate (Helly, 1976) and pentose phosphate (Hochachka and Hayes, 1962 Yamaguchi et al., 1976 Walsh, 1985 Malinovskaya, 1988 Kudryavtseva, 1990) shunts have also been found to increase in importance. The activity of transketolase, the enzyme which inhibits the peptide-phosphate pathway, is greater in fish from cold water, e.g. trout and smelt, than in those from warm water (Kudryavtseva, 1990). In the Black Sea horse-mackerel, a sharp decline in adenine nucleotide content (AMP, ADP and ATP) in white and red muscle tissues and in liver occurs at low temperature (Trusevich, 1978). In this case, the ATP is mosdy resynthesized by glycolysis. The increase in the glucose content of the blood of fish at low ambient temperatures may be of the same nature (Prosser, 1967 ... 

Temperature is therefore a determining factor influencing the timing and character of both somatic and generative production in Black Sea fish. All the species examined form a series, which is related to their temperature preference anchovy - horse-mackerel - red mullet - pickerel - whiting - sprat. In the first species the somatic and generative productions coincide, while in the last there is a large space of time between them. In horse-mackerel, red mullet and pickerel there is a partial overlap. 

Figure 58 Relationship between the oxygen consumption of different species and the temperature of the habitat in which they were caught 1, anchovy 2, sprat 3, horse-mackerel 4, pickerel 5, red mullet 6, whiting.

The rate of consumption differs among species when their feeding rate reaches its maximum. Anchovy eat most (in summer), with horse-mackerel coming next. Third are sprats, which have a small body and develop high swimming activity to compensate for the low temperature of the water at the depth in which they live. Red mullet come fourth, and lastly come pickerel and whiting the latter two engage in very little motor activity and consume food poor in calories. The relative levels of food consumption between species may be different when expressed in different ways fresh matter, dry matter or calories. 

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