Red mullet

Red mullet (Mullidae), Mullus barbatus-, gills Coutou, France... 

Red mullet, Mullus barbatus Spain, Mediterranean coast, summers 1989, 1990 muscle ... 

Scorpion fish Turbot Red mullet Whiting Pickerel... 

When the production of different Black Sea fish is compared, the six species investigated divide roughly into two groups, one comprising anchovy and sprat and the other, pickerel, whiting, horse-mackerel and red mullet. The sizes and biomasses of fish within a group are similar, as are some biological features. 

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. 

A considerable quantity of body proteins are also involved in generative synthesis, evidenced by substantial consumption of these proteins during the pre-spawning period by horse-mackerel, red mullet, whiting and pickerel. This would not have occurred if the food proteins had been adequate for the purpose. As horse-mackerel, red mullet and scorpion fish mature, the transport of serum proteins (albumin, a- and 3-globulins) proceeds more intensively (Golovko, 1964 Kondratyeva, 1977). The... 

The activity of alkaline phosphatase in fish scales is relevant to the study of the biochemical characteristics of production (Senkevich, 1967 red mullet, round goby). This enzyme promotes calcification of bones and scales, and its activity correlates well with the linear growth of the fish (Figure 55), so it is most intense during the warm season. Data from cold-water fish are not available. 

Figure 55 Activity of alkaline phosphatase in scales of red mullet during the annual cycle. (After Senkevich, 1967.) Age (years) , 1 A, 2 , 3 0,4 x, 5-6.

It is not difficult to assess the average biomass of a fish stock over many years, using data on the numbers and biomass of samples. In Black Sea anchovy, it is 284 kt in May. By November the figure doubles as a result of replenishment and of somatic increase. The average annual biomass (B) amounts to 426 kt for anchovy, 280 kt for sprat, about 36 kt for horse-mackerel, 6 kt for red mullet and 9 kt for whiting (no data are available for pickerel). Results of the studies on annual specific and absolute production in populations of the fish examined here and Px/B coefficients are given in Table 11. 

Anchovy Sprat Horse-mackerel Red mullet Pickerel Whiting... 

Having tested this method, many workers will still want to asses annual production from positive values only. If such is the case, Table 12 can be used to determine coefficients of conversion for annual production estimates for all components or for positive values only. Estimates are highest for anchovy, somewhat less in red mullet, horse-mackerel, pickerel and sprat, while there is no difference in whiting. This is the ranking of the species studied for differences between somatic and generative production. It has... 

There is an inverse relationship between the absolute and the specific production of anchovy, sprat, horse-mackerel and red mullet (Figure 57). High absolute production is a result of the extensive mode (high initial abundance), while high specific production is related to the intensive mode with a more efficient increase of the biomass. 

Figure 57 Relationship between absolute production (g) and specific production (g g- mass) O, anchovy , sprat A, horse-mackerel x, red mullet.

From the data of Danilevsky et al. (1979), the natural mortality and losses from the fishery of red mullet can be reckoned as 60% and 30%, respectively. Assuming that predators remove 10% of the stock, the total elimination would amount to 100% of the biomass or 6 kt. However, production yielded by red mullet is 8 kt - the difference is 25%. Data on the natural mortality of whiting are lacking. These comparisons therefore show a reasonable correspondence between the two basic characteristics of stocks of Black Sea fish - production and elimination. 

The share of total production contributed by different age groups varies between species (Table 14). In anchovy 70% of the total production (fresh weight) is contributed by yearlings and 2-year-old fish in sprat the value is 80%, and in red mullet over 80%. Three age groups (yearlings, 2- and 3-year-old fish)... 

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.

As Belokopytin (1968, 1978) reported, the percentage of basal metabolism ( b) estimated from standard (Qn) was 40% in highly mobile horse-mackerel and anchovy, 75% in moderately mobile red mullet and about 100% in the sluggish scorpion fish. Sometimes basal metabolism is named supporting metabolism, which is incorrect and leads to misunderstanding. Metabolism and diet support the balanced equilibrium, P = 0. 

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