Oyster seedlings are the first ring of oyster farming. Whether or not they can harvest good quality and quantity of seedlings will play a decisive role in apology. Although the people along the coast of China have a long history of breeding oysters and have a rich economy, in the past there were still a lot of farmers who, when they were going to put their seedlings, closed without knowing the sea conditions, seedlings, and seedlings, and they blindly went to the sea. Putting in the applicator not only failed to pick up the seedlings, but also caused the attachment base to be filled with floating organisms such as floating mud and barnacle, causing damage. Therefore, it is very important to know how to master the changes in sea conditions in the searing area and the changes in the number of oyster seedlings in the sea area in order to predict the correct time for seedlings and to put in attachment bases so as to obtain high manual labor and quantity of seedlings.
The preparation of oyster seedlings forecast must master the following items:
(1) Grasp the objective laws of the sea state change; in the various factors of the sea state, we must grasp the two main factors of water temperature and salinity, according to the observation of years of water temperature of the Pearl River estuary oyster farm: During the oyster spawning period from March to September (Lunar Calendar, The same), the range of 21.5-31.5 °C. From April to May in the most prosperous period of oyster breeding, the average water temperature was 26.2-29.8°C. It is appropriate to use 26.2-29.5°C when preparing forecasts. According to the characteristics of salinity: during the peak season of oyster attachment in April-May, the salinity ranged from 3.8 to 20 ‰ and the average salinity was 13.85 ‰. When preparing the oyster juvenile shell adhesion forecast, the saltiness should be 6.95-17.5 ‰. It is appropriate to prepare oyster plankton larvae with the salinity of 9.45-20.33 最 in the most prosperous period.
(2) Grasp the oviposition rate of oysters on a monthly basis: According to the analysis of oyster gonad development records, the Pearl River estuary is in the majority of sexual protozoa formation period in January. February is the majority of sexual cell differentiation. From March to September, sexual cell maturation and ovulation and fertilization were carried out (of which the April-June period was the peak of egg production and release). During the end of October-December, during the spawning season, the oyster spawning rate often varies greatly at different times of the same month, which is mainly related to changes in temperature gradient caused by tidal changes. The salinity is generally high at high tides and low at low tides. Almost 80-90% of oysters are spawning spermatozoa several days after tidal currents. This is due to the high salinity shift to low salinity during this period. Due to the stimulation of the changes, however, due to the different geographic shapes and orientations of some bays, affected by wind and waves, they also affect the salinity of these bays. Therefore, when analyzing the spawning of oyster tides, it is necessary to consider the wind direction at the same time. Effect on salinity, and make appropriate corrections to the data. In addition, in sex ratios of oysters of all ages at each tidal period, if females account for more than 50%, generally better seedlings can be taken during the lower tide period.
(3) To master the changes in the metamorphosis and quantity of oyster planktonic larvae: The mature larvae of the oysters from the D-type stage to the late stage of the crust were measured and the shell length ranged from 76 to 394 μm, of which the D-type shells were 76-158 μm long. The initial period is 108-203 μm, the mid-range of the shell is 190-260 μm, and the top of the shell is 254-394 μm. Under normal sea conditions, the D-phase to the initial period of the crust roof averaged 38.5 microns. From the beginning of the shell to the middle of the top of the shell, the average growth period is 69.5 microns. From the middle of the shell to the late period of the shell, the average growth period is 99 microns. To compile the seedling harvesting forecast, first of all, the most concentrated situation of planktonic larvae in each period is used to determine the tendency of the larvae to cluster and attach. Secondly, in order to facilitate better application in forecasting, the growth rate of planktonic larvae was changed to the average “daily growth rate†according to the size of planktonic larvae at each developmental stage, ie, the average daily growth from D-type period to the initial period of the shell top was 25 μm. From the beginning of the shell to the middle of the top of the shell, the average daily growth was 31 microns. From the middle of the shell to the late period of the crust, the daily growth rate is 32 micrometers. From the high or low growth rates, it is possible to determine whether the expected number of clings and development of the juvenile tide will be good. The third is to master the changes in the number of planktonic larvae. During the oyster spawning season, changes in the number of larvae are related to the geographical environment, salinity, tides, and wind direction. There are two types of site environmental conditions.
1 During the seedling season, from high salinity to low salinity oyster mining sites (again, growing farms), the oyster larvae cluster size can be increased to meet the production requirements, most of them appear in the tidal period, the frequency of its occurrence More than 75% of the total.
At 2 places in the bay (the river catchment in the upper reaches of Jiangkou, it was almost a freshwater area in the early seedling season. During the tide period, the seawater increased in a negative flow and salinity increased gradually. In this type of site, the larval colony of oysters increased to meet production needs. The quantity is mostly in the tide period, and its occurrence rate is about 90%.
For the above two types of seedling collection farms, under normal normal sea conditions (salinity variation 6.1-22.96 ‰, water temperature 26.5-31.5 CC), the number of larval rear larvae in oyster shells is 25-60 per cubic meter of water, and its future The amount of adhesion is only enough for production needs. If there are 100-300 per cubic body of water, the amount of one attachment is sufficient for production.
(4) To master the trend of oyster shell attachment: According to the records of the Pearl River estuary and the Red Sea Bay in the South China Sea for many years, there were oyster seedlings adhering to the river in the whole year. From March onwards, the amount of attachment began to rise. At the beginning of October it has fallen to a low point. From April to May, it was the peak of attachment. The second is from June to September. From the end of July to the end of September, due to the inhibition of early oviposition of oysters in some years and the fullness and maturity of the reproductive glands, short-term attachment of oyster seedlings to secondary peaks often occurs, and the amount of adhesion from October to December is extremely small.
During the most prosperous period of oyster attachment, different oyster fields have different characteristics. In the high salinity seedling collection sites, the peaks of oyster attachment mostly appeared in the low tidal period (upper and lower chords). Only the salinity dropped below 4.8 ,, and the attachment peak appeared in the tide period.
The most prosperous period of oyster attachment is the period of the barnacles. The abundance of barnacle attachments suddenly abruptly decreases, and large amounts of oyster larvae often appear. Therefore, during harvesting, according to the emergence trend of barnacle, it can be used as an auxiliary index to predict the attachment of oyster seedlings.
To compile the seedling collection forecast, we must determine the current and next period of pelagic larvae's attachment quantity based on the number of attachments of the pupae, the size of the attachment groups, and the date of attachment, ie, the attachment of pups, and correct the state of the sea. The number of planktonic larvae and other organisms, such as barnacles, are related to one another.
Prepare the method of seedling forecasting. To prepare forecasts, we must first select representative water areas in the mining area to record, collect, and analyze samples of various sea conditions such as water temperature, salinity, number of water bodies, oysters, barnacle larvae, and 150 square centimeters (equivalent to a 2.5 - The amount of seedlings attached to the 3-kilogram stone attachment base in the seabed), the gonad development of each age oyster, and the production of eggs. All kinds of samples required to be collected are checked on the same day and marked on the chart for discussion and preparation of forecasts.
In order to accurately determine the amount of oysters and barnacles attached by microscopic examination, a 150-square-centimeter round-shaped electric board is used as the attachment base. In order to make the forecast easy to use in production, it is advisable to divide the amount of deposition into several stages (grades are omitted).
Example: Short-term forecast time: Year Month Day (May 3rd, Lunar Calendar)
Location: The oyster field of Shenzhen Bay in the east bank of the Pearl River estuary was inspected: (1) The water temperature was 27.5-27.6°C. (2) The salinity (or specific gravity) is 17.17-17.25 ‰. (3) The oysters floated 1033/m2 of larval shells in the late stage, 1900/m2 in the early period of the shell, and 637/m2 in the D-type, with normal size. (4) Barnacle nauplii was not found. (5) Adherence of the seedlings in the previous period: the number of attachments was 28-38/150 cm2, and the length of the attached shell was 296-809 μm. There were many upper layers of the adherent water layer and less layers.
Data analysis: (1) Water temperature and salinity are suitable for picking seedlings. (2) The number of planktonic larvae at the top of the shell and at the beginning of the shell is very large. The larvae have normal morphology. It is expected that there will be sufficient larvae that can effectively join in the current period. If the sea conditions are stable, the potential for the next period will be greater. (3) The size of the seedlings attached to the previous period was uneven, indicating that the group was different from the group of larvae. This batch of larvae will enter the front attachment of this period, and the peak of attachment should be in the next period. (4) Barnacle nauplii and Venus larvae were not found, indicating that the amount of barnacles attached was very small during the current period. Conducive to the attachment of oyster larvae.
The preparation of the forecast is as follows: "Shenzhen oysters short-term seedling forecast." ****, Shenzhen Bay, May 3rd (Lunar New Year, same below), measured salinity 17.17-17.25 海. Water temperature 27.5-27.6°C. The actual seedling volume from April 30 to May 3 in the bay is tier 3 (30-80) of oyster seedlings per 150 square centimeters (equivalent to 2.5 kg of heavy stone).
According to the data analysis at each observation station, it is expected that there will be an increase in seedlings in the Bay within the next 3 days, up to 5 (200-500). Barnacles have very little adhesion. Among them, the amount of seedlings attached to the deep-water oyster area in the west and south back areas is sufficient for production. From the Daoye and Shatou areas of shallow water oysters, a large number of seedlings are attached, and sufficient production is needed. Suitable for large-scale seedlings.
The preparation of oyster seedlings forecast must master the following items:
(1) Grasp the objective laws of the sea state change; in the various factors of the sea state, we must grasp the two main factors of water temperature and salinity, according to the observation of years of water temperature of the Pearl River estuary oyster farm: During the oyster spawning period from March to September (Lunar Calendar, The same), the range of 21.5-31.5 °C. From April to May in the most prosperous period of oyster breeding, the average water temperature was 26.2-29.8°C. It is appropriate to use 26.2-29.5°C when preparing forecasts. According to the characteristics of salinity: during the peak season of oyster attachment in April-May, the salinity ranged from 3.8 to 20 ‰ and the average salinity was 13.85 ‰. When preparing the oyster juvenile shell adhesion forecast, the saltiness should be 6.95-17.5 ‰. It is appropriate to prepare oyster plankton larvae with the salinity of 9.45-20.33 最 in the most prosperous period.
(2) Grasp the oviposition rate of oysters on a monthly basis: According to the analysis of oyster gonad development records, the Pearl River estuary is in the majority of sexual protozoa formation period in January. February is the majority of sexual cell differentiation. From March to September, sexual cell maturation and ovulation and fertilization were carried out (of which the April-June period was the peak of egg production and release). During the end of October-December, during the spawning season, the oyster spawning rate often varies greatly at different times of the same month, which is mainly related to changes in temperature gradient caused by tidal changes. The salinity is generally high at high tides and low at low tides. Almost 80-90% of oysters are spawning spermatozoa several days after tidal currents. This is due to the high salinity shift to low salinity during this period. Due to the stimulation of the changes, however, due to the different geographic shapes and orientations of some bays, affected by wind and waves, they also affect the salinity of these bays. Therefore, when analyzing the spawning of oyster tides, it is necessary to consider the wind direction at the same time. Effect on salinity, and make appropriate corrections to the data. In addition, in sex ratios of oysters of all ages at each tidal period, if females account for more than 50%, generally better seedlings can be taken during the lower tide period.
(3) To master the changes in the metamorphosis and quantity of oyster planktonic larvae: The mature larvae of the oysters from the D-type stage to the late stage of the crust were measured and the shell length ranged from 76 to 394 μm, of which the D-type shells were 76-158 μm long. The initial period is 108-203 μm, the mid-range of the shell is 190-260 μm, and the top of the shell is 254-394 μm. Under normal sea conditions, the D-phase to the initial period of the crust roof averaged 38.5 microns. From the beginning of the shell to the middle of the top of the shell, the average growth period is 69.5 microns. From the middle of the shell to the late period of the shell, the average growth period is 99 microns. To compile the seedling harvesting forecast, first of all, the most concentrated situation of planktonic larvae in each period is used to determine the tendency of the larvae to cluster and attach. Secondly, in order to facilitate better application in forecasting, the growth rate of planktonic larvae was changed to the average “daily growth rate†according to the size of planktonic larvae at each developmental stage, ie, the average daily growth from D-type period to the initial period of the shell top was 25 μm. From the beginning of the shell to the middle of the top of the shell, the average daily growth was 31 microns. From the middle of the shell to the late period of the crust, the daily growth rate is 32 micrometers. From the high or low growth rates, it is possible to determine whether the expected number of clings and development of the juvenile tide will be good. The third is to master the changes in the number of planktonic larvae. During the oyster spawning season, changes in the number of larvae are related to the geographical environment, salinity, tides, and wind direction. There are two types of site environmental conditions.
1 During the seedling season, from high salinity to low salinity oyster mining sites (again, growing farms), the oyster larvae cluster size can be increased to meet the production requirements, most of them appear in the tidal period, the frequency of its occurrence More than 75% of the total.
At 2 places in the bay (the river catchment in the upper reaches of Jiangkou, it was almost a freshwater area in the early seedling season. During the tide period, the seawater increased in a negative flow and salinity increased gradually. In this type of site, the larval colony of oysters increased to meet production needs. The quantity is mostly in the tide period, and its occurrence rate is about 90%.
For the above two types of seedling collection farms, under normal normal sea conditions (salinity variation 6.1-22.96 ‰, water temperature 26.5-31.5 CC), the number of larval rear larvae in oyster shells is 25-60 per cubic meter of water, and its future The amount of adhesion is only enough for production needs. If there are 100-300 per cubic body of water, the amount of one attachment is sufficient for production.
(4) To master the trend of oyster shell attachment: According to the records of the Pearl River estuary and the Red Sea Bay in the South China Sea for many years, there were oyster seedlings adhering to the river in the whole year. From March onwards, the amount of attachment began to rise. At the beginning of October it has fallen to a low point. From April to May, it was the peak of attachment. The second is from June to September. From the end of July to the end of September, due to the inhibition of early oviposition of oysters in some years and the fullness and maturity of the reproductive glands, short-term attachment of oyster seedlings to secondary peaks often occurs, and the amount of adhesion from October to December is extremely small.
During the most prosperous period of oyster attachment, different oyster fields have different characteristics. In the high salinity seedling collection sites, the peaks of oyster attachment mostly appeared in the low tidal period (upper and lower chords). Only the salinity dropped below 4.8 ,, and the attachment peak appeared in the tide period.
The most prosperous period of oyster attachment is the period of the barnacles. The abundance of barnacle attachments suddenly abruptly decreases, and large amounts of oyster larvae often appear. Therefore, during harvesting, according to the emergence trend of barnacle, it can be used as an auxiliary index to predict the attachment of oyster seedlings.
To compile the seedling collection forecast, we must determine the current and next period of pelagic larvae's attachment quantity based on the number of attachments of the pupae, the size of the attachment groups, and the date of attachment, ie, the attachment of pups, and correct the state of the sea. The number of planktonic larvae and other organisms, such as barnacles, are related to one another.
Prepare the method of seedling forecasting. To prepare forecasts, we must first select representative water areas in the mining area to record, collect, and analyze samples of various sea conditions such as water temperature, salinity, number of water bodies, oysters, barnacle larvae, and 150 square centimeters (equivalent to a 2.5 - The amount of seedlings attached to the 3-kilogram stone attachment base in the seabed), the gonad development of each age oyster, and the production of eggs. All kinds of samples required to be collected are checked on the same day and marked on the chart for discussion and preparation of forecasts.
In order to accurately determine the amount of oysters and barnacles attached by microscopic examination, a 150-square-centimeter round-shaped electric board is used as the attachment base. In order to make the forecast easy to use in production, it is advisable to divide the amount of deposition into several stages (grades are omitted).
Example: Short-term forecast time: Year Month Day (May 3rd, Lunar Calendar)
Location: The oyster field of Shenzhen Bay in the east bank of the Pearl River estuary was inspected: (1) The water temperature was 27.5-27.6°C. (2) The salinity (or specific gravity) is 17.17-17.25 ‰. (3) The oysters floated 1033/m2 of larval shells in the late stage, 1900/m2 in the early period of the shell, and 637/m2 in the D-type, with normal size. (4) Barnacle nauplii was not found. (5) Adherence of the seedlings in the previous period: the number of attachments was 28-38/150 cm2, and the length of the attached shell was 296-809 μm. There were many upper layers of the adherent water layer and less layers.
Data analysis: (1) Water temperature and salinity are suitable for picking seedlings. (2) The number of planktonic larvae at the top of the shell and at the beginning of the shell is very large. The larvae have normal morphology. It is expected that there will be sufficient larvae that can effectively join in the current period. If the sea conditions are stable, the potential for the next period will be greater. (3) The size of the seedlings attached to the previous period was uneven, indicating that the group was different from the group of larvae. This batch of larvae will enter the front attachment of this period, and the peak of attachment should be in the next period. (4) Barnacle nauplii and Venus larvae were not found, indicating that the amount of barnacles attached was very small during the current period. Conducive to the attachment of oyster larvae.
The preparation of the forecast is as follows: "Shenzhen oysters short-term seedling forecast." ****, Shenzhen Bay, May 3rd (Lunar New Year, same below), measured salinity 17.17-17.25 海. Water temperature 27.5-27.6°C. The actual seedling volume from April 30 to May 3 in the bay is tier 3 (30-80) of oyster seedlings per 150 square centimeters (equivalent to 2.5 kg of heavy stone).
According to the data analysis at each observation station, it is expected that there will be an increase in seedlings in the Bay within the next 3 days, up to 5 (200-500). Barnacles have very little adhesion. Among them, the amount of seedlings attached to the deep-water oyster area in the west and south back areas is sufficient for production. From the Daoye and Shatou areas of shallow water oysters, a large number of seedlings are attached, and sufficient production is needed. Suitable for large-scale seedlings.