SU1732892A1 - Method for growing pilengas mullet larvae - Google Patents

Abstract

FIELD OF THE INVENTION The invention relates to the fishing industry, in particular to methods for growing mullet larvae. SUMMARY OF THE INVENTION: After hatching, the larvae are kept in tanks with a semi-closed water supply system with sea water and feeding for the first 12 days at a water temperature of 21-25 ° C, salinity not less than 18%, pH 8.1-8.4, planting density 25-30 mg / l larvae and water exchange from 1.5 to 3 volumes per day, from 13 to 19 days with a water temperature of 26–27 ° C, a gradual decrease in salinity to 13%. a decrease in planting density to 6 mg / l from day 20 to day 30 of the larvae at a water temperature of 28–29 ° C, a gradual decrease in salinity to 7%, and a water exchange of 3.5–4 volumes per day. 1 tab.

Description

The method relates to mariculture, namely to the cultivation of the larvae of the pelengas under artificial conditions.

After hatching, the larvae are kept in tanks with a semi-closed water supply system with sea water and fed for the first 12 days at a water temperature of 21-25 ° C, salinity not lower than 18 ° / oo, pH 8.1-8.4, density of larva landing 25-30 pcs / l and water exchange 1.5-3 v / l per day, from 13 to 19 days with a water temperature of 26 - 27 ° С, a gradual decrease in salinity to 13 ° / oo, a decrease in the density of planting to 6 pcs / l, from the 20th to the 30th day, the larvae contain, at a water temperature of 28–29 ° C, a gradual decrease in salinity to 7 ° / oo and a water exchange of 3.5–4 volumes per day.

Example 1. The larvae immediately after hatching were kept in tanks with a volume of 6 m3, temperature 21 ° С, salinity 18 ° / oo, density of planting 25-30 pcs / l, water exchange 1.5 volumes per day.

The first 3 days the withdrawal was 75%, from the 3rd to the 7th day the temperature was increased to 23 ° C. From the 4th to the 5th day, copepods were introduced as live food for rotifers and nauplii.

From the 7th to the 12th day, the water temperature after 2 days was raised by 1 ° C and brought to 25 ° C, the water exchange was increased to 3 volumes per day, the oxygen content was 5.5 mg / l. From the age of 13 days, the water temperature was increased by another 1 ° (up to 26 ° C), the salinity decreased to 13 ° / oo (from the 13th to the 19th day, not more than 1 ° / oo per day). The water exchange was 3 volumes per day, the oxygen content was 6 mg / l. By the end of the period, the density of planting was reduced to 6 pcs / l. Artificial food was added to the live feed in the amount of 50-60% of the total diet.

From 20 to 30 days old, the temperature was increased to 27 ° C, the salt water was reduced to 7 ° / oo (by 1 ° / day 2), water exchange

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- 4 volumes per day, oxygen content 6 mg / l. The ratio of live and artificial food 1: 1, fed at least 8 times during the daytime.

At the end of juicy-resistant fry from larvae that switched to active feeding, was 59%. The length of the larvae by the thirtieth day of cultivation was 37 mm. Slowing growth of larvae is obviously associated with an insufficiently high temperature at the last stage of growth.

In the control, the larvae were kept by a known method at a temperature of 21-25 ° С, salinity from 18 to 13 ° / 0 °, and water exchange from 1/3 to 1 volume per day.

The survival rate of the larvae was 2%, the length of the larvae, 55 mm.

PRI mme R 2. In analogy to Example 1, the larvae of the pelengas were grown to 12 days old, from 13 to 19 days of cultivation, the water temperature was first increased to 26 ° C, and then, to 16 days, to 27 ° C. From the 20th to the 25th day, the temperature was raised to 28 ° С, and on the 30th day the water temperature was raised to 29 ° С.

The larvae yield was 68%, the length of the larvae reached 26.3tO, 23 mm.

PRI me R 3. Analogously to Example 1, the temperature of the water on the 25th - 30th day was increased to 31 ° C. The oxygen content was maintained at 5 mg / l, however, the larvae yield was 61% due to the fact that the larvae did not feed at 30-31 °, the weight gain stopped, the length of the larvae was 21.8 ± 0.43 mm.

PRI me R 4. Analogously to example 1, the salinity was reduced to 5 ° / oo on the 25-30th day. The survival rate of the larvae decreased to 40%, the length of the larvae was 20.2 ± 0.98 mm.

Example 5. In analogy to Example 1, the water exchange from 12 days of age was 3 volumes per day. Survival rate was 58%, the length of the larvae was 26, OtO, 95 mm.

Example 6. In analogy to Example 1, the flow rate increased from 20 days to 5 volumes per day, the oxygen content increased to 7 mg / l, the survival rate was 67%, however, due to the strong flow, the feed was removed and increased its consumption, which is economically unjustified, the length of the larvae is 25,, 79 mm.

Example. Analogously to example 1, the larvae of the pelengas were kept for the entire period of cultivation at a temperature of 21-25 ° C, salinity from 18 to 13 ° / oo, water exchange from 1.2 to 2 volumes per day. The larvae grew poorly, the oxygen fell below 5 mg / l, therefore the survival rate was only 25%, and the length of the larvae was 20 mm.

For example, analogously to example 1, the water temperature in the period from the 13th to the 19th day was raised to 29 ° C and the larvae were kept at this temperature for 30 days. Survival decreased to 55%. The length of the larvae was 22, 48.

Example 9. In analogy to Example 1, the water temperature, starting from the 20th day of cultivation, was raised from 27 to 29 ° C and maintained at this level until the 30th day. The larvae grew worse than with a smooth increase in temperature, the survival rate was 66%, the length of the larvae, 8 mm.

An example. Analogously to Example 1, the water exchange from 13 to 25 days of cultivation was maintained at the level of 3 volumes per day, from 26 days increased to 4 volumes per day. The oxygen content from the 20th to the 25th day of cultivation was 5 mg / l. Survival — 60%; larvae length 22 0.32.

Example 11. Analogously to example 1

water exchange from 20 to 25 days increased from 3

Up to 3.5 volumes per day, the acid content of the genus has risen to 6 mg / l. Survival

was 65%, the length of the larvae was 25 ± 0.48.

Example 12. In analogy to Example 1, on the 20th day of cultivation, the salinity was reduced from 13 to 7 ° / °. A sharp drop in salinity 0 adversely affected the state of the larvae, the survival rate decreased to 42%, the length of the larvae was 20.3-0.71.

The results of the cultivation of the larvae of the Py- lungas under various hydrochemical conditions are tabulated.

As can be seen from examples 5 and 7, water exchange is less than 1.5-3 volumes per day during the growing period from 1 to 12 days and less than 1.5-4 0 volumes from 13 to 30 days adversely affects survival ( 58 and 25% respectively).

An increase in water temperature of more than 27 ° C from the 13th to the 19th day of growing 5 (example 8) and more than 29 ° C (example 3) from the 20th to the 30th day is also undesirable, since linear larval growth.

A necessary condition for the high survival rate of the larvae of the pelengas is the reduction of salinity at the cultivation stage from 20 to 30 days to 7 ° / oo (examples 1-3), but not less than 5% (example 4).

A stepwise increase in temperature or a decrease in salinity (examples 9 and 12) reduces the rate of growth and survival. The same applies to water exchange (examples 10 and 11).

Claims (1)

Thus, the proposed method is effective; it provides 60 - 68% of the survival rate of the pelengas with a length of 25-27 mm of larvae at the stage of its development from glue to month old. Claims method of growing mullet larvae of pelengas, consisting in keeping the larvae in containers with water and feeding the larvae, with the first 12 days the larvae contain at a water temperature of 21-25 ° C, salinity is not less than 18%, the density of planting 0 25-30 larvae larvae and 1.5-3 volumes of water per day, from 13 to 19 days, the larvae contain at a water temperature of 26 - 27 ° C, gradually reducing salinity to 13% o, reducing the density of planting to 6 pcs / l, from the 20th to the 30th day, the larvae keep at a water temperature of 28–29 ° C, a gradual decrease in salinity to 7%, and a water exchange of 3.5–4 volumes per day.