The silverfish migration and fishing technology I. Overview With the deep development of the market economy, the material living standards of the people in our country have been continuously improved, and the demand for famous and special aquatic products in the domestic and foreign markets has been increasing. Therefore, the development of famous special aquatic products has been vigorously developed. Increasing cultivation has become an inevitable trend in the development of aquaculture in China. Silverfish is a small, wild and economic fish living in the Changshui area. It is famous for its tender meat, delicious taste, and high nutritional value. It is one of China's famous special aquatic products and has been renowned both at home and abroad for many years. I have a vast area of ​​land water in China, including lakes, reservoirs and other large and medium-sized water bodies of about 140 million acres, and most of the water quality, food resources are very rich. However, most of our country’s fisheries are still in a low-yielding and low-benefit state, the water productivity has not been fully utilized, and the potential for fishery production to increase production efficiency is great. Utilizing its superior water quality and the advantages of natural feed resources, the proliferation of whitebait resources and the development of the whitebait fishery have become increasingly valued by the aquaculture community. Many years of practice have proved that the transplantation and acclimatization of whitebait is a resource proliferation technology with less investment, quick results, high efficiency, and convenience. After a one-time transplant investment and receiving the fishery effect, as long as there are planned and rational use of resources, annual input of fish species, bait, and facilities will not be needed. Silverfish products are popular among consumers at home and abroad for many years because of their deliciousness and high nutritional value.
The international market has gradually expanded from Japan, Hong Kong, and other regions to other parts of Asia, as well as Europe, the Americas, and Australia. Domestically, whitebait is not only an indispensable dish on banquets at major hotels, but also serves as a nutritious, low-fat dish. Placed on the tables of ordinary people's holidays, the market is rapidly expanding. At present, the supply of products is in short supply and prices have increased year by year. Practice and experiments have proved that whitebait has a strong ability to adapt to the environment. China’s vast inland waters range from south to north, from plains to mountainous regions and plateaus. Where appropriate water bodies, silverfish can grow, reproduce, and form population productivity. Silverfish transplantation has a broad prospect in China. To make full use of the advantageous conditions of inland waters, organize and plan and guide the rational promotion of transplanted silverfish. After several years of unremitting efforts, it will not only expand the distribution of whitebait, increase the output of silver fish products, and greatly increase the inland areas. The production capacity of the water area can further develop its fisheries in the direction of “high yield, high quality, and high efficiency†and reach a new level, which will inevitably have a positive effect on the poverty alleviation of the people in the lake (kuo) area and the vegetable and basket projects of the urban and rural people. . As the fishermen who have benefited from said, “Introduce a fish to save a pool of water and enrich the people.†The author has conducted more than 10 years of biological, ecological, and population changes of the whitebait in Taihu Lake and their resource conservation and protection technologies. Investigations and researches were carried out and experiments on the techniques of transplantation and domestication and theories were conducted. The results, techniques, and experiences we have obtained are introduced in conjunction with relevant information. We hope to promote the proliferation of whitebait resources and the development of the whitebait fishery in China.
Second, the classification of silverfish and its morphological characteristics
(A) The classification of the whitebait The whitebait is a kind of bony fish, a species of carp and a subspecies. There are 20 genera of 8 genera in two subfamilies (New Silverfish Subfamily and Silverfish Subfamily). According to the survey, there are 6 genera and 15 species in China, namely, the big whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the silver New silverfish, near Taihu new silverfish, small Japanese whitebait, silverfish between foreheads, whitebait between short-kissed fish, whitebait and whitebait, whitebait and Chinese silverfish, among which there are many new species of silverfish. A total of eight kinds, as shown in Table 1. At present, the best-selling domestic and foreign markets are Taihu Lake New Whitebait, Great Whitebait, and Oligodon New Whitebait. The three methods of use are: Observing silverfish according to the requirements of 1; , 3... Until the implementation of a fish species; if the characteristics of the whitebait do not match the characteristics of the 1 requirement, follow the hints in () in the back () to carry out the search and always implement the fish species. Example: Observe the whitebait according to 1 requirements. If there is no 2 black spots in the middle of the caudal fin, then check 10 and continue to check 11 according to the 10 required characteristics. If it matches the 11 feature, it is the new whitebait; if not, continue Check 14, and 14 is in line with the new whitebait near Taihu Lake.
(B) The characteristics of the silverfish family Silverfish fish, small, slender body, cylindrical body in front of the body, the whole body without scales or with sparsely arranged thin scales, fat fins, caudal fins forked, with a forehead Teeth or tongue teeth, living body in addition to eyeballs black, the body has a small number of black spots, the whole body transparent; habitat in fresh water, brackish water or sea water, there are migratory, land seal two types.
(3) Characteristics of the Great Whitebait and the New Whitebait of Taihu Silverfish Protosalanx hualocranins (Abbott) The genus of the silverfish is the genus of the new whitebait, the subspecies, which is the only one of this species. The whitebait has a flat head, a triangular shape, a pointed snout, and a lower mandible that is longer than the upper jaw; the maxilla has a series of fine teeth and the tongue and mandible have two rows of fine teeth. The fat fins are located at the anterior end of the anal fins; the anal fins are located below the dorsal fin ends, with 29 to 32 fins; 15 to 15 dorsal fins; and 23 to 26 pectoral fins. The live large whitebait is transparent and has black lines on each side of the abdomen; the body turns white after death. The eel is long and only one room has a fistula communicating with the esophagus. Adult males and females have obvious differences. The male body length is 5.8-6.8 times the body height, which is 4.1-4.6 times of the head length. The tail shank length is 2.1-2.4 times the height of the tail shank; the female body length is 6.1- 6.8-fold, 3.8-4.2 times the head length, and 1.9-2.2 times the height of the tail shank. Males have secondary sexual characteristics. The fins of the pectoral fins are longer and extend rearward. They have sharp horns. The anal fins are large. The anterior fins are thick and the back is slightly wavy. The anal fin base above the breeding period Hip scales on each side: 20 to 29; heart area is red. Females do not have the above traits. Taihu Lake produces the largest individual with a total length of up to 20 cm. Taihu new whitebait Neosalanx taihuensis Chen Taihu new whitebait belongs to the new whitebait. The body is slender, and the pelvic fins have previously been cylindrical. Later, they are laterally flat. The head is flat, the snout is short and blunt, and the upper jaw is shorter than the lower jaw. There are a series of fine teeth on the upper and lower jaws and no teeth on the tongue surface. There are 12-14 back fins, 20-24 anal fins, 25-26 pectoral fins, and 7 pelvic fins. The living body is transparent and white after death. Each side of the abdomen has a line of small black spots. The pelvic fins have no melanin and the caudal fins are black on the upper and lower leaves. The fat fins are smaller, opposite to the anal fin base, and the lipid fin base is longer than the free part. Adult anal fins, male and female fish have obvious differences, males are larger, fan-shaped, the front part of the fins thick, breeding period has 14-22 hip scales, females are smaller elongated. Taihu Lake, the largest individual in Taihu Lake, has a total length of about 8 centimeters. It has a single chamber ridge, and has a sacral canal through the esophagus. The sacral canal is relatively long, 0.72 times the length of the pupa.
Third, the biological and ecological characteristics of silverfish
(A) The reproduction and reproduction of whitebait is an important part of the fish's life process, and breeding can breed offspring and expand its population. The life cycle of the whitebait is 1 year. The hatched larvae grow and develop after nearly 1 year. After the gonads mature, they undergo reproductive activities and produce new offspring. The broodstock that have died will soon die. 1. Large whitebait (l) Genital organs: The genital organs are relatively simple but special. The female has two ovaries. The ovaries are not arranged in pairs in the body cavity like in the quadrangular fish, but are arranged one behind the other. The left ovary is located in the left front side of the digestive tract, and the right ovary is located in the right rear side of the digestive tract. Between the two ovaries there are They are separated. The mature egg is discharged from the ovary into the body cavity and is then produced by the gonopore. The male has only a small testis, located to the right of the back of the digestive tract. (2) Reproductive groups: individual differences are larger. Females have a total length of 9-27 cm and a body weight of 3.5-40 g. Males have a total length of 9-21 cm and a body weight of 4-38 g. (3) Gonadal development: The rate of gonadal development differs depending on the environment in which it is inhabited. The gonads of Tai Yinhu giant silverfish are still in phase I until October, and they are phase II-III in November and phase IV in December. A few individuals started spawning in mid-December. Mature eggs are round, egg diameter 0.90-1.07 mm, surrounded by an egg membrane. (4) Breeding period: The breeding season is from mid-December to mid-March of the following year with a water temperature of 1-10°C. The breeding season is mid-January and the water temperature is 2-7°C. (5) Reproductive ability: Spermophilus has strong reproductive ability, with at least 3190 absolute absorptive eggs and a maximum of 43580 grains; relative fecundity is at least 524 grains/g body weight and at most 1540 grains/g body weight. (6) Fertilization and hatching: The ratio of broodstock during the reproduction changes greatly, the ratio of male to female in the early stage is 1:2-4, the male-male ratio in the prosperous stage is approximately 1:1, and the ratio of male to female in the late stage is 2-3:1. The whitebait belongs to the batch type of spawning and may have individuals with different stages of development in the same batch of fish. The ovaries of the same individual have egg cells at different phases. Table 2 Embryo development process of large silverfish. Water temperature (°C) duration of development 5.1 Fertilization at 4.41O 54 minutes; Water uplift at 4.516 hours and 11 minutes for the first time; 2 Cell division at 4.816 for 35 minutes; 4 cell stage 4.918 at 13:00 3rd split; 8 cell stage 4.553 at 24 minute high blastocyst 5.975 at 47 minute low blastocyst 5.884 at 02 minute early gastroenteric at 8.7122 hour 7 at 9.1146 at late stage 1 1 1 minute embryo formation At 9.0164, 24 minutes of vesicular appearance at 8.9353 at 17 minutes; embryonic body twitching; heartbeat at 8.2626 at 13 minutes; embryos twitching vigorously; head and tail detached from the yolk sac; heartbeat 63 beats/min at 8.1636; 27 larvae ruptured and hatched. The salt development ability in embryo development is strong. In the water with a salinity of 0.5‰-12%o, the embryonic development rate, the final hatching rate and the survival condition of larvae were basically consistent with those in freshwater. 2. New silverfish in Taihu Lake Due to the different breeding seasons, the new whitebait of Taihu Lake is usually divided into two ecological groups: Chunzong and Qiuzong. The genital organs are similar to the big whitebait. The left ovary of the female is located on the front left side of the digestive tract and the right ovary is located on the right side of the digestive tract. The male testis is located on the right rear side of the digestive tract. Individual reproductive groups are 53 to 100 mm in length and 0.5 to 5 grams in weight, with little difference between male and female. Due to the influence of environmental factors, the individual size of different populations or different generations of the same population, or different ecological groups of spring and autumn of the same generation are often significantly different. Mature eggs are round, egg diameter 0.43-0.73 mm. Absolute fetal volume of 500-2570 tablets, usually 1500-2000 tablets, is proportional to body length. The relative ovulation amount was 1476-1673 grains/g body weight (only four hundred home fishes were only 100--200 grains/g body weight). Spawning occurs mostly in lakes (ku) bays 1-2 meters deep in the water body and in shallow water areas upstream of the reservoir, and is spawned in batches. Fertilized eggs are sinking. Under natural conditions, the incubation period shortens as the water temperature continues to increase. At a water temperature of 10-23.5°C, the incubation period is 3-8 days. The newly hatched larvae are 2.5-3.5 mm long. The breeding period of the spring population in Taihu Lake ranges from early March to mid-May, and the breeding season is mid-April in April. Individual bodies also have early and delayed phenomena. At this time, the water temperature is 6-25°C, and the water temperature during the rich period is 11.8. 15.4°C. Its embryonic development is shown in Table 3. During the breeding period of the Qiutian group, from late September to early November, a few broodstocks have an early and delayed phenomenon, and the water temperature is 12-26.46°C. The peak period of concentrated spawning is not obvious. It is usually mid-to-late October and the water temperature is 20.2-18°C. Table 3: Embryonic development process of neocissima taihuensis. Water temperature (°C) Duration of development 21 Fertilization 210 hours 15 minutes Disc formation 19.21 hours 10 minutes First division, 2 cell period 19.21:55:55 Second division, 4 cell period 19.22 at 20 minutes, third division, 8-cell period 19.52 to 44 minutes, fourth division, 16-cell period, 19.53-fold 16-fold, fifth division, 32-cell period, 19.73- 40 minute, sixth division, 64-cell period, Monolayer minicells, covering the surface of eggs l/6 to 1/520.0 4:12 minute cell morula stage 20.15 o'clock 11 o'clock blastocyst stage 18.824 o'clock 51 minutes gastrula stage 19.226 o'clock 40 o'clock neurons 20.130 o'clock 46 minutes Foam, sarcolemma 4 pairs of 2O.136 when 51 points olfactory sac appeared, sarcolemma 18 pairs of 20.239 36 minutes sarcolemma 22 pairs, embryonic body package 6/719.5 45 minutes 56 minutes of cardiac primordium formation, sarcolemma 28 pairs , 83.052 when the Buckwheat sac appeared at 11 points 19.160 hours 21 points from the yolk sac, heartbeat 27 beats / min 18.572 44 minutes brain, embryo twitching, heartbeat 65 beats / min 17.892 hours 26 minutes heart beat 88 beats / min, Embryonic body around the yolk sac 19.0105 36 minutes heart rate 121 beats / min, tail hatched first, then the overall hatch
(B) The Growth Law of Silverfish The so-called growth refers to the increase in body length and weight. The growth of fish, like any other organism, depends on the inherent characteristics of its species. In the long evolutionary process, each species has its own growth characteristics and is inherited from generation to generation. Outside living conditions cannot be changed overnight, but within their genetic growth characteristics, the growth depends on the ecological factors of the inhabited waters. There are many ecological factors that affect the growth of fish, the most important of which are food, water temperature, and oxygen in the water. Growth involves important issues such as the selection of proliferating objects, the adjustment of the number of populations in the water body, and the determination of reasonable fishing specifications. Therefore, special attention has been given to fishery management. Silverfish, like other fish, its growth is affected by the nature of the species constraints and the impact of the ecological environment and show different characteristics, each with its own characteristics, but its growth type and growth laws are basically the same, is a uniform growth type. Juvenile growth is extremely rapid, especially in the first 4 months of age, and all parameters of growth indicators are high. First, the body length grows rapidly. After the growth of the body length becomes slower, the body weight rapidly increases until the inflection point is reached. After rapid growth to the slow-growing junction of the age of the month, body length and body weight growth tend to be slow, and the gonad begins to develop rapidly. Since the life of silverfish is only one year, its growth is studied and analyzed using the age of months. The age of the moon is determined in this way. It is represented by the larvae during the productive period. The date of hatching is 0 months, 1 month is 1 month, 2 months is 2 months, and so on. Take the growth of big silverfish and Taihu new whitebait in Taihu Lake as an example. The introduction is as follows: 1. The length, weight and growth of the big whitebait at each month are shown in Table 4.
The growth rate of body weight of large silverfish is the highest at the age of one month, and gradually decreases with the increase of the age of months. The increase in body length is also the highest in 1 month and gradually decreases with the increase of the age of the month. The increase in body weight at the age of one month is very low, and gradually increases with the increase of the age of the month, and it decreases significantly after 7 months of age. The length and body weight of a large silverfish is a power function. The relationship is: W=aLb where: W is body weight; L is body length; calculated a=3.98110-6; b=2.9359 (close to 3). It is a uniform growth type. The Von BertaLanffy growth equation is applied. The equation is: Lt=L∞[lek(t−t0)] Wt=W∞[lek(t−t0)] 3 Where: L∞ is the body length limit; W∞ is the weight limit; K is Brod The growth coefficient is a constant that determines the rate of decrease in body length growth. The larger the value of K, the greater the decrease in growth, the greater the growth rate from a fixed point; t and to represent the age of the month, and Lt represents the month of t. Body length at age, Wt represents the body weight at t months of age. The growth curve of the large silverfish was an asymmetrically elongated S-shape, and the inflection point was 7.8 months old. At this time, the body weight was 8.81 g. After that, the growth of silverfish began to slow. The growth curve of the length of the silverfish does not have an inflection point, and the initial curve rapidly rises. With the increase of the age of months, the rise of the curve gradually becomes slower and tends to be an asymptotic value (L∞), indicating that the length of the large silverfish grows in young and young. The fish stage is extremely rapid and gradually becomes slower as the age of the moon increases. Changes in growth rate and growth acceleration can further explain the growth characteristics of big whitebait. At 2.2-7.8 months of age, the growth curve of weight gain of large silverfish increased, while the acceleration curve of weight growth decreased, but the acceleration was positive, indicating that the growth rate of body weight between 2.2 and 7.8 months of age was an increasing phase, increasing in speed (ie, Acceleration) gradually decreased; after 7 or 8 months of age, the body weight growth rate curve and acceleration curve both declined, and the acceleration was negative, indicating that after 7 or 8 months of age, the body weight growth rate was in a decreasing stage, and in the negative area, it was followed by a month. As the age increases, the curve has a tendency to rebound. It can be assumed that the natural acceleration is zero when it reaches the limit. The growth rate of the body length of the silverfish decreases with the increase of the age of the month, and the body growth acceleration is always negative, and increases with the increase of the age of the month, indicating that the growth acceleration of the body length is always in a decreasing stage, and the decreasing speed (ie Acceleration gradually gets faster, which means that the growth rate of body length gradually decreases with the increase of age. 2. Table 5, Table 6 The body length, body weight and corresponding month age of the spring whitefish and the whitebait of the new whitebait, Taihu Lake and the whitebait.
The international market has gradually expanded from Japan, Hong Kong, and other regions to other parts of Asia, as well as Europe, the Americas, and Australia. Domestically, whitebait is not only an indispensable dish on banquets at major hotels, but also serves as a nutritious, low-fat dish. Placed on the tables of ordinary people's holidays, the market is rapidly expanding. At present, the supply of products is in short supply and prices have increased year by year. Practice and experiments have proved that whitebait has a strong ability to adapt to the environment. China’s vast inland waters range from south to north, from plains to mountainous regions and plateaus. Where appropriate water bodies, silverfish can grow, reproduce, and form population productivity. Silverfish transplantation has a broad prospect in China. To make full use of the advantageous conditions of inland waters, organize and plan and guide the rational promotion of transplanted silverfish. After several years of unremitting efforts, it will not only expand the distribution of whitebait, increase the output of silver fish products, and greatly increase the inland areas. The production capacity of the water area can further develop its fisheries in the direction of “high yield, high quality, and high efficiency†and reach a new level, which will inevitably have a positive effect on the poverty alleviation of the people in the lake (kuo) area and the vegetable and basket projects of the urban and rural people. . As the fishermen who have benefited from said, “Introduce a fish to save a pool of water and enrich the people.†The author has conducted more than 10 years of biological, ecological, and population changes of the whitebait in Taihu Lake and their resource conservation and protection technologies. Investigations and researches were carried out and experiments on the techniques of transplantation and domestication and theories were conducted. The results, techniques, and experiences we have obtained are introduced in conjunction with relevant information. We hope to promote the proliferation of whitebait resources and the development of the whitebait fishery in China.
Second, the classification of silverfish and its morphological characteristics
(A) The classification of the whitebait The whitebait is a kind of bony fish, a species of carp and a subspecies. There are 20 genera of 8 genera in two subfamilies (New Silverfish Subfamily and Silverfish Subfamily). According to the survey, there are 6 genera and 15 species in China, namely, the big whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the new whitebait, the silver New silverfish, near Taihu new silverfish, small Japanese whitebait, silverfish between foreheads, whitebait between short-kissed fish, whitebait and whitebait, whitebait and Chinese silverfish, among which there are many new species of silverfish. A total of eight kinds, as shown in Table 1. At present, the best-selling domestic and foreign markets are Taihu Lake New Whitebait, Great Whitebait, and Oligodon New Whitebait. The three methods of use are: Observing silverfish according to the requirements of 1; , 3... Until the implementation of a fish species; if the characteristics of the whitebait do not match the characteristics of the 1 requirement, follow the hints in () in the back () to carry out the search and always implement the fish species. Example: Observe the whitebait according to 1 requirements. If there is no 2 black spots in the middle of the caudal fin, then check 10 and continue to check 11 according to the 10 required characteristics. If it matches the 11 feature, it is the new whitebait; if not, continue Check 14, and 14 is in line with the new whitebait near Taihu Lake.
(B) The characteristics of the silverfish family Silverfish fish, small, slender body, cylindrical body in front of the body, the whole body without scales or with sparsely arranged thin scales, fat fins, caudal fins forked, with a forehead Teeth or tongue teeth, living body in addition to eyeballs black, the body has a small number of black spots, the whole body transparent; habitat in fresh water, brackish water or sea water, there are migratory, land seal two types.
(3) Characteristics of the Great Whitebait and the New Whitebait of Taihu Silverfish Protosalanx hualocranins (Abbott) The genus of the silverfish is the genus of the new whitebait, the subspecies, which is the only one of this species. The whitebait has a flat head, a triangular shape, a pointed snout, and a lower mandible that is longer than the upper jaw; the maxilla has a series of fine teeth and the tongue and mandible have two rows of fine teeth. The fat fins are located at the anterior end of the anal fins; the anal fins are located below the dorsal fin ends, with 29 to 32 fins; 15 to 15 dorsal fins; and 23 to 26 pectoral fins. The live large whitebait is transparent and has black lines on each side of the abdomen; the body turns white after death. The eel is long and only one room has a fistula communicating with the esophagus. Adult males and females have obvious differences. The male body length is 5.8-6.8 times the body height, which is 4.1-4.6 times of the head length. The tail shank length is 2.1-2.4 times the height of the tail shank; the female body length is 6.1- 6.8-fold, 3.8-4.2 times the head length, and 1.9-2.2 times the height of the tail shank. Males have secondary sexual characteristics. The fins of the pectoral fins are longer and extend rearward. They have sharp horns. The anal fins are large. The anterior fins are thick and the back is slightly wavy. The anal fin base above the breeding period Hip scales on each side: 20 to 29; heart area is red. Females do not have the above traits. Taihu Lake produces the largest individual with a total length of up to 20 cm. Taihu new whitebait Neosalanx taihuensis Chen Taihu new whitebait belongs to the new whitebait. The body is slender, and the pelvic fins have previously been cylindrical. Later, they are laterally flat. The head is flat, the snout is short and blunt, and the upper jaw is shorter than the lower jaw. There are a series of fine teeth on the upper and lower jaws and no teeth on the tongue surface. There are 12-14 back fins, 20-24 anal fins, 25-26 pectoral fins, and 7 pelvic fins. The living body is transparent and white after death. Each side of the abdomen has a line of small black spots. The pelvic fins have no melanin and the caudal fins are black on the upper and lower leaves. The fat fins are smaller, opposite to the anal fin base, and the lipid fin base is longer than the free part. Adult anal fins, male and female fish have obvious differences, males are larger, fan-shaped, the front part of the fins thick, breeding period has 14-22 hip scales, females are smaller elongated. Taihu Lake, the largest individual in Taihu Lake, has a total length of about 8 centimeters. It has a single chamber ridge, and has a sacral canal through the esophagus. The sacral canal is relatively long, 0.72 times the length of the pupa.
Third, the biological and ecological characteristics of silverfish
(A) The reproduction and reproduction of whitebait is an important part of the fish's life process, and breeding can breed offspring and expand its population. The life cycle of the whitebait is 1 year. The hatched larvae grow and develop after nearly 1 year. After the gonads mature, they undergo reproductive activities and produce new offspring. The broodstock that have died will soon die. 1. Large whitebait (l) Genital organs: The genital organs are relatively simple but special. The female has two ovaries. The ovaries are not arranged in pairs in the body cavity like in the quadrangular fish, but are arranged one behind the other. The left ovary is located in the left front side of the digestive tract, and the right ovary is located in the right rear side of the digestive tract. Between the two ovaries there are They are separated. The mature egg is discharged from the ovary into the body cavity and is then produced by the gonopore. The male has only a small testis, located to the right of the back of the digestive tract. (2) Reproductive groups: individual differences are larger. Females have a total length of 9-27 cm and a body weight of 3.5-40 g. Males have a total length of 9-21 cm and a body weight of 4-38 g. (3) Gonadal development: The rate of gonadal development differs depending on the environment in which it is inhabited. The gonads of Tai Yinhu giant silverfish are still in phase I until October, and they are phase II-III in November and phase IV in December. A few individuals started spawning in mid-December. Mature eggs are round, egg diameter 0.90-1.07 mm, surrounded by an egg membrane. (4) Breeding period: The breeding season is from mid-December to mid-March of the following year with a water temperature of 1-10°C. The breeding season is mid-January and the water temperature is 2-7°C. (5) Reproductive ability: Spermophilus has strong reproductive ability, with at least 3190 absolute absorptive eggs and a maximum of 43580 grains; relative fecundity is at least 524 grains/g body weight and at most 1540 grains/g body weight. (6) Fertilization and hatching: The ratio of broodstock during the reproduction changes greatly, the ratio of male to female in the early stage is 1:2-4, the male-male ratio in the prosperous stage is approximately 1:1, and the ratio of male to female in the late stage is 2-3:1. The whitebait belongs to the batch type of spawning and may have individuals with different stages of development in the same batch of fish. The ovaries of the same individual have egg cells at different phases. Table 2 Embryo development process of large silverfish. Water temperature (°C) duration of development 5.1 Fertilization at 4.41O 54 minutes; Water uplift at 4.516 hours and 11 minutes for the first time; 2 Cell division at 4.816 for 35 minutes; 4 cell stage 4.918 at 13:00 3rd split; 8 cell stage 4.553 at 24 minute high blastocyst 5.975 at 47 minute low blastocyst 5.884 at 02 minute early gastroenteric at 8.7122 hour 7 at 9.1146 at late stage 1 1 1 minute embryo formation At 9.0164, 24 minutes of vesicular appearance at 8.9353 at 17 minutes; embryonic body twitching; heartbeat at 8.2626 at 13 minutes; embryos twitching vigorously; head and tail detached from the yolk sac; heartbeat 63 beats/min at 8.1636; 27 larvae ruptured and hatched. The salt development ability in embryo development is strong. In the water with a salinity of 0.5‰-12%o, the embryonic development rate, the final hatching rate and the survival condition of larvae were basically consistent with those in freshwater. 2. New silverfish in Taihu Lake Due to the different breeding seasons, the new whitebait of Taihu Lake is usually divided into two ecological groups: Chunzong and Qiuzong. The genital organs are similar to the big whitebait. The left ovary of the female is located on the front left side of the digestive tract and the right ovary is located on the right side of the digestive tract. The male testis is located on the right rear side of the digestive tract. Individual reproductive groups are 53 to 100 mm in length and 0.5 to 5 grams in weight, with little difference between male and female. Due to the influence of environmental factors, the individual size of different populations or different generations of the same population, or different ecological groups of spring and autumn of the same generation are often significantly different. Mature eggs are round, egg diameter 0.43-0.73 mm. Absolute fetal volume of 500-2570 tablets, usually 1500-2000 tablets, is proportional to body length. The relative ovulation amount was 1476-1673 grains/g body weight (only four hundred home fishes were only 100--200 grains/g body weight). Spawning occurs mostly in lakes (ku) bays 1-2 meters deep in the water body and in shallow water areas upstream of the reservoir, and is spawned in batches. Fertilized eggs are sinking. Under natural conditions, the incubation period shortens as the water temperature continues to increase. At a water temperature of 10-23.5°C, the incubation period is 3-8 days. The newly hatched larvae are 2.5-3.5 mm long. The breeding period of the spring population in Taihu Lake ranges from early March to mid-May, and the breeding season is mid-April in April. Individual bodies also have early and delayed phenomena. At this time, the water temperature is 6-25°C, and the water temperature during the rich period is 11.8. 15.4°C. Its embryonic development is shown in Table 3. During the breeding period of the Qiutian group, from late September to early November, a few broodstocks have an early and delayed phenomenon, and the water temperature is 12-26.46°C. The peak period of concentrated spawning is not obvious. It is usually mid-to-late October and the water temperature is 20.2-18°C. Table 3: Embryonic development process of neocissima taihuensis. Water temperature (°C) Duration of development 21 Fertilization 210 hours 15 minutes Disc formation 19.21 hours 10 minutes First division, 2 cell period 19.21:55:55 Second division, 4 cell period 19.22 at 20 minutes, third division, 8-cell period 19.52 to 44 minutes, fourth division, 16-cell period, 19.53-fold 16-fold, fifth division, 32-cell period, 19.73- 40 minute, sixth division, 64-cell period, Monolayer minicells, covering the surface of eggs l/6 to 1/520.0 4:12 minute cell morula stage 20.15 o'clock 11 o'clock blastocyst stage 18.824 o'clock 51 minutes gastrula stage 19.226 o'clock 40 o'clock neurons 20.130 o'clock 46 minutes Foam, sarcolemma 4 pairs of 2O.136 when 51 points olfactory sac appeared, sarcolemma 18 pairs of 20.239 36 minutes sarcolemma 22 pairs, embryonic body package 6/719.5 45 minutes 56 minutes of cardiac primordium formation, sarcolemma 28 pairs , 83.052 when the Buckwheat sac appeared at 11 points 19.160 hours 21 points from the yolk sac, heartbeat 27 beats / min 18.572 44 minutes brain, embryo twitching, heartbeat 65 beats / min 17.892 hours 26 minutes heart beat 88 beats / min, Embryonic body around the yolk sac 19.0105 36 minutes heart rate 121 beats / min, tail hatched first, then the overall hatch
(B) The Growth Law of Silverfish The so-called growth refers to the increase in body length and weight. The growth of fish, like any other organism, depends on the inherent characteristics of its species. In the long evolutionary process, each species has its own growth characteristics and is inherited from generation to generation. Outside living conditions cannot be changed overnight, but within their genetic growth characteristics, the growth depends on the ecological factors of the inhabited waters. There are many ecological factors that affect the growth of fish, the most important of which are food, water temperature, and oxygen in the water. Growth involves important issues such as the selection of proliferating objects, the adjustment of the number of populations in the water body, and the determination of reasonable fishing specifications. Therefore, special attention has been given to fishery management. Silverfish, like other fish, its growth is affected by the nature of the species constraints and the impact of the ecological environment and show different characteristics, each with its own characteristics, but its growth type and growth laws are basically the same, is a uniform growth type. Juvenile growth is extremely rapid, especially in the first 4 months of age, and all parameters of growth indicators are high. First, the body length grows rapidly. After the growth of the body length becomes slower, the body weight rapidly increases until the inflection point is reached. After rapid growth to the slow-growing junction of the age of the month, body length and body weight growth tend to be slow, and the gonad begins to develop rapidly. Since the life of silverfish is only one year, its growth is studied and analyzed using the age of months. The age of the moon is determined in this way. It is represented by the larvae during the productive period. The date of hatching is 0 months, 1 month is 1 month, 2 months is 2 months, and so on. Take the growth of big silverfish and Taihu new whitebait in Taihu Lake as an example. The introduction is as follows: 1. The length, weight and growth of the big whitebait at each month are shown in Table 4.
The growth rate of body weight of large silverfish is the highest at the age of one month, and gradually decreases with the increase of the age of months. The increase in body length is also the highest in 1 month and gradually decreases with the increase of the age of the month. The increase in body weight at the age of one month is very low, and gradually increases with the increase of the age of the month, and it decreases significantly after 7 months of age. The length and body weight of a large silverfish is a power function. The relationship is: W=aLb where: W is body weight; L is body length; calculated a=3.98110-6; b=2.9359 (close to 3). It is a uniform growth type. The Von BertaLanffy growth equation is applied. The equation is: Lt=L∞[lek(t−t0)] Wt=W∞[lek(t−t0)] 3 Where: L∞ is the body length limit; W∞ is the weight limit; K is Brod The growth coefficient is a constant that determines the rate of decrease in body length growth. The larger the value of K, the greater the decrease in growth, the greater the growth rate from a fixed point; t and to represent the age of the month, and Lt represents the month of t. Body length at age, Wt represents the body weight at t months of age. The growth curve of the large silverfish was an asymmetrically elongated S-shape, and the inflection point was 7.8 months old. At this time, the body weight was 8.81 g. After that, the growth of silverfish began to slow. The growth curve of the length of the silverfish does not have an inflection point, and the initial curve rapidly rises. With the increase of the age of months, the rise of the curve gradually becomes slower and tends to be an asymptotic value (L∞), indicating that the length of the large silverfish grows in young and young. The fish stage is extremely rapid and gradually becomes slower as the age of the moon increases. Changes in growth rate and growth acceleration can further explain the growth characteristics of big whitebait. At 2.2-7.8 months of age, the growth curve of weight gain of large silverfish increased, while the acceleration curve of weight growth decreased, but the acceleration was positive, indicating that the growth rate of body weight between 2.2 and 7.8 months of age was an increasing phase, increasing in speed (ie, Acceleration) gradually decreased; after 7 or 8 months of age, the body weight growth rate curve and acceleration curve both declined, and the acceleration was negative, indicating that after 7 or 8 months of age, the body weight growth rate was in a decreasing stage, and in the negative area, it was followed by a month. As the age increases, the curve has a tendency to rebound. It can be assumed that the natural acceleration is zero when it reaches the limit. The growth rate of the body length of the silverfish decreases with the increase of the age of the month, and the body growth acceleration is always negative, and increases with the increase of the age of the month, indicating that the growth acceleration of the body length is always in a decreasing stage, and the decreasing speed (ie Acceleration gradually gets faster, which means that the growth rate of body length gradually decreases with the increase of age. 2. Table 5, Table 6 The body length, body weight and corresponding month age of the spring whitefish and the whitebait of the new whitebait, Taihu Lake and the whitebait.
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