Sprat temperature

Fish from temperate zones have been most studied, and from these we learn that temperature may influence the character of metabolic rhythm both indirectly, through food supply, and directly, through the limited temperature ranges within which one or other vital activity can or cannot occur. It is the response or the preference that fish show to temperature that shapes the rhythmic pattern. This is well shown in two diametrically opposite fish from the Black Sea, the warm-water anchovy and the cold-water sprat (Figure 34). The curves that describe the course of triacyl-glycerol accumulation in these species mirror each other, as the fish oppose one another in their time of spawning. 

Temperature affects food supply in another way also. The Mediterranean sprat, which prefers cold waters, exploits a wider feeding area than fish that inhabit only warm waters, because it takes advantage of a greater water depth and can feed all the year round. It possesses a much greater lipid reserve than the warm-water anchovy, and its range of fatness over the annual cycle is wider (Figure 36). The feeding conditions in the warm Mediterranean waters are therefore more favourable to fish that prefer cooler waters rather than warm. 

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. 

In fish which require cold water (sprat and whiting), the annual rhythms are not nearly so well defined. Their preferred temperature zone is in deep water, where the temperature is relatively stable throughout the year. The temperature of the regions of the Black Sea inhabited by warm-water fish may vary by as much as 10-15° over the year, but the habitat of cold-water fish varies by only 3-5°. The latter fish have not only a smaller metabolic variation throughout the year, but also a higher consumption of food in winter (sprats consume 7.3% of their body weight daily at that time) than that of the species requiring warm water. 

Sprat recruitment has been shown to be driven by climate-induced temperature changes during the years 1955-2005 (MacKenzie and Koster, 2004 MacKenzie et al., 2008). MacKenzie and Koster (2004) found a positive correlation between recruitment and the average water column temperature in May (Fig. 18.9). In an exploratory analysis relating recruitment to monthly depth-specific temperatures, Baumann et al. (2006) observed significant temperature-recruitment correlations between March and July in mid-water... 

FIGURE 18.9 Relationship between May temperature at 45-65 m in the Bornholm Basin and sprat recruitment in Subdivisions 22-32 (MacKenzie et al., 2008). The dots are year classes 1973-1999 and the numbers represent year classes since 2000. The regression line (dotted) and 95% confidence limits (dashed) only includes the years 1973-1999 (MacKenzie and Koster, 2004). 

FIGURE 18.13 Scheme summarizing the processes leading to the present low cod/high sprat ecosystem in the central Baltic Sea grey arrows indicate salinity/oxygen-driven processes, hlack arrows indicate temperature-driven processes, dotted hlack arrows indicate a trophic cascade from cod to sprat and Pseudocalanus acuspes, F Fishery, C Cod, SPR Sprat, PS P. acuspes, AC Acartia spp. 

Nissling, A., 2004. Effects of temperature on egg and larval survival of cod (Gadus morhua) and sprat (Sprattus sprattus) in the Baltic Sea—implications for stock development. Hydrobiologia, 514, 115-123. 

The plant transient analysis code SPRAT-DOWN, described in Sect. 4.2, is extended for the analyses of abnormal transients and accidents. The calculation model is shown in Fig. 6.12. The models of the equipment, i.e., the AFS, SRV, MSIVs, and turbine bypass valves, are added for safety analyses. A hot chaimel, where the linear heat generation late and maximum cladding surface temperature are the highest in the core, is modeled as well as the average channel in order to calculate the highest values of cladding temperature and pellet enthalpy. The flow chart is shown in Fig. 6.13. 

Since the pressure is kept supercritical due to no depressurization, only SPRAT-DOWN is used. The reactor behavior is analyzed until a high temperature stable condition is obtained. 

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