Biology In Embryo Development And Techniques Of Propagation And Aquaculture Of American Shad (Alosa Sapidissima)

American shad (Alosa sapidissimd) is a largest species in family Clupeidae of order Clupeiformes. It is an anadromous fish, native to the Atlantic coast of North America. A. sapidissima is one of the best-known tastiest species(Sapidissima means’very delicious’), as well as economic importance in aquaculture. It has been extensively introduced to other countries. American shad has the morphological similarity and competitive taste to the Chinese favorite species of Reeve’s shad (Tenualosa reevesii). Hence, the introduction of this species plays a significant role in the commercial aquaculture in China; especially when the Chinese Reeve’s shad is extinct nowadays. Although the plan for introducing fertilized egg of American shad was initialed in China as early as the late 1990s, however the actual progress of propagation and culture of this species were not successful due to the lack of systematic research on its early development biology and early larval rearing technology. In this study, I investigated the embryonic development of American shad and provided the techniques of artificial breeding and larval rearing in order to facilitate the commercial aquaculture of this species in China.1. Artificial breeding and rearing ofAmerican shad(Alosasapidissima) in greenhouse-earthen pondsusing well waterwere succeeded. The processes of embryonic development of this species was observed and recorded. Results showed that the gonad maturation rate of 2-year old A. sapidissima reached 60%-80% after applying the supplement of hormone, unsaturated fatty acid and vitamin E along withwater flow stimulation.Induced spawning of broodstock can be achieved through adequate water temperature ranges from 16 to 23℃ and constant water flow. A total of 90,000 eggs were collected from 50 pairs of broodstockfrom the lateApril to the end of May in 2010.The average fertilization rate was 10% and the hatchability reached 70%-80%. The artificial breeding was also successful through injection of 3 types of mixed regents including 1) LHRH-A2 and hormone,2) LHRH-A2+HCG+DOM and hormone, and 3) LHRH-A2+ HCG and hormone. A total of 105,700 eggs were obtained, average fertilization rate ranged from 0 to 21.5% while the hatchability ranged from 0 to 70%. Fertilized eggsof A. sapidissima were oval in shape with an average size of 4.03 (± 0.25) mm in diameter. The embryonic development can be divided into 7 physiological stageswith 30 development durations based on embryo morphology and conformation. It took 71 h and 40 min to complete the whole embryonic development under water temperature of 20 (± 1)℃.2. The morphological development of American can be classified into larvae, fry and juvenile stages during their early life stage. Newly hatched larvae reached 6.75 (■0.60) mm in total length. Two-day-old larvae revealed feeding activities under the ambient temperature of 20 (±1)℃. Larvae started to feed on available food when their yolk sacw absorbed 4 days after hatching. The swim bladder, vertebrae and fins were developed duringthis stage. Thirty-six days after hatching, occurrence of some scale-like substance around the sites of back of the operculum andlateral lines of body indicated that larvae metamorphosed into the stage of fry. Thereafter, fry developed into juveniles at the age of 65 days.The scales andperitoneumof juveniles were completely developed at this stage. It is very important to understand the morphological development of the early life stages of American shad for the purpose of their aquaculture. Results indicated t that temperature, water quality, and primary feeding strategy are critical to American shad aquaculture. Therefore, recommendations for the aquaculture management included:1) control water temperature at 20 (±1)℃ during the early culture stage; 2) feed larvaerotifers at a density of 5-10 ind./ml from the second day after hatching;3) feedfry cladocerans and copepods. In addition to above, semi-buoyant artificial pelletswere developed as an additional food supply for the fry of A.sapidissima. Introducing artificial pellets to fry was succeeded after 20 days duration in this study before fry canfeed on commercialfloating pellets. This is the key technique that ensures the success in aquaculture of A.sapidissima.