Anchovy lipids

Figure 9 Lipid content of the flesh of anchovy caught in different areas of the Sea of Azov, as a percentage. (After Shulman, 1972a.)...

There is a strong interannual variation in the lipid concentration in the flesh of planktivorous fish such as anchovy, kilka and sprat, which is governed by the varying abundance of the plankton (Shulman, 1972b, 1996 Luts and Rogov, 1978 Luts, 1986). 

Calculations show that total lipid production is 20-25% less in infested populations of anchovy and goby than in those clear of the parasites. What is more, infestation weakens fish, rendering them scarcely able to migrate, survive the winter or spawn. This thesis is not indisputable, however. Like predators, parasites regulate the numbers of their victims, rather than wiping them out, by withdrawing the most weakened or unviable hosts from the process of competition for food. 

Figure 33 Seasonal dynamics of lipid unsaturation in anchovy. (After Shulman, 1978a Yuneva, 1990.) Continuous line, iodine value broken line, total polyenoic acids.

While the character of metabolism is greatly influenced by temperature, its rate depends on foraging conditions. In Chapter 2, distinctions were made between the lipid contents of three races of anchovy. Here, the curves in Figure 35 show the rates of lipid accumulation in Engraulis encrasicholus maeoticus, E. e. ponticus and E. e. mediterraneus from the Azov, Black and Mediterranean Seas, respectively. The abundance of zooplankton in the three... 

Figure 34 Lipid accumulation and withdrawal (schematic) in different months by the anchovy and sprat. (After Shulman, 1978a.) Continuous line, sprat broken line, anchovy.

Figure 35 Lipid dynamics of three races of anchovy. (After Shulman, 1978a.) Broken line, Azov Sea anchovy solid line, Black Sea anchovy dotted and broken line, Mediterranean anchovy.

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. 

Figure 36 Annual lipid cycle in anchovy (broken line) and sprat (continuous line) in the Mediterranean. (After Shulman, 1978a.)...

In some species, like the cold-water fish of the Black Sea, protein and lipid accumulation may occur together, while in fish which prefer warmer water in the same sea, such as anchovy and horse-mackerel, they do not. Both the degree and duration of such concordance are important in the adaptation of fish. 

Figure 40 The lipid content of Black Sea anchovy following the feeding period, in relation to the average temperature of the water in spring. Temperature data from published sources., lipid content , temperature. (After Shulman and Dobrovalov, 1979.)...

Figure 46 The lipid level of Azov anchovy and the temperature at which they migrate.

Figure SO Somatic production of anchovy 3 years old. Right-hand scale 1, calorific value (broken line). Left-hand scale 2, lipids 3, proteins 4, dry matter.

Figure 52 Seasonal changes in somatic and generative growth in populations of anchovy and sprat (mg g-1 fresh tissue) solid line, proteins broken line, lipids dotted and broken line, mineral matter and glycogen.

Figure 53 Seasonal changes in the lipid fractions of the white muscle of anchovy O, triacyl-glycerols , phospholipids A, non-esterified fatty acids.

In the anchovy, the total saturated fatty acids content in the reserve and structural lipid fractions is maximal in the autumn and minimal during the rest of the year. However, the polyenoic acids in these two fractions are maximal in winter, spring and summer, but minimal in autumn. During spring and summer, a substantial reduction is observed in the quantity of 16 0,18 1 and 22 6 in the triacyl-glycerols, perhaps because of transfer to sexual products in which they accumulate as stored energy (saturated and monoenoic acids) or as structural elements (polyenoic acids). They are of similar importance in this context in capelin, horse-mackerel, cod, Pacific saury, eelpout and trout (Jeffries, 1972 Dobrusin, 1978 Ackman, 1983 Henderson etaL, 1984). 

Figure 61 Expenditure of substances on total metabolism during a year by anchovy. Whole column wet matter light stipple lipids heavy stipple proteins. The small numbers represent age groups.

Figure 64 Food consumed by anchovy during a year, age groups 1-5. Total column, dry matter open column, total mineral matter, solid black area, glycogen light stipple, lipids heavy stipple, proteins.

The transformation of food is very similar in populations of anchovy and sprat (Figure 66). The total amount of lipid and protein assimilated into the body is also similar in the two species, but their proportions differ between the food and the fish body the food is richer in protein and poorer in lipid when compared with the fish which consume it. Somewhat less than half of the body lipid appears to be formed from ingested protein ( liponeogenesis ), whereas all of the body protein originates in the diet. Some of the dietary lipid and, possibly, protein is transformed into glycogen. The mechanisms responsible... 

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