Studies On Technique Of Large-scale Seed Production In Atrina Pectinata

The pen shell (Atrina pectinata), which belongs to Pinna, Pinnidae, Mytiloida, is a commercially important marine bivalve. It has a large latter adductor muscle that can be processed into delicious "Dried Scallops" which is enrichment in nutrition. However, during the recent 10 years, the resource of A. pectinata in our country has experienced significant declines because of excessive capture and the deterioration of the environment, now it is difficult to collect them in many natural sea areas. To fulfill the needs of markets both in and out of country, it is urgent to promote the artificial breeding and reproduction of A. pectinata.The research of artificial seed production in A. pectinata had started from 1980s, but has not established the techniques for large-scale seed production by now. There are some problems such as conglutination among larvae, convergence on surface and low survival rate. So, from 2003 to 2005 we undertook the project of the development of seed production techniques of A. pectinata which was granted by Shandong Province.During the three years, from the beginning of calefactively induced maturation, we enriched the nutritional diet of broodstock, feed them with a mixture of microalgae and ediable foodstuffs and employed temperature-induced maturation to observe the changes of relative fatness to decide the artificial spawning time of A. pectinata, also we exploited new inducement methods using Hydrogen peroxide or first by dipping in vitamin and then adding spermatic fluid or ova fluid obtained from dissection, which have an inducement rate above 90%. During cultivation, the larvae density was controlled by 3-4 individuals per milliliter in prophase and 1-2 in anaphase. The diet lists were also altered along with their growth, they were fed mainly on Isochrysis galbana Parks 3011 with auxiliary Platymonas subcordiformis in prophase, and Platymonas subcordiformis with auxiliary Chaetoceros mulleri and Isochrysis galbana Parks 3011 in anaphase, photosynthetic bacteria was also demanded every regular time. The microalgae supplied as diet were ascertained to be fresh, non-aging, non-pollution in quality. To prevent the conglutination and convergence on surface among larvae, we adopted series methods including water and air changes, grade culling and transfer between concrete tanks.When the larval length reached 400μm different substrates were deposited to carry out different kinds of seedling collection including collection without sediments, collection with sand on the bottom of the tanks, collection with substrates of scallop and sand hanging in the tanks and collection with sand in floating cages. In general perspectives of metamorphosis success, the unit picks of seedling collection, growth speed, our results showed that seedling collection without sediments has the highest metamorphosis success of eyebot larvae which was above 30% and the best output capacity of unit water body just after metamorphosis, but half a month later the growth rate became the slowest with the lowest survival rate 20%. So the seedlings that were collected by this method must be transferred to floating cages or bags with sand on the bottom after 600μm. The second best method was collection with substrates of scallop and sand hanging in the tanks which had a metamorphosis success of around 30% and the fastest growth that contributed to the biggest spat in average, but the cost was comparatively higher. Next to this method was collection with sand in floating cages, it had a rapid growth and the highest survival rate which was suitable for cultivation of spat in later period. The worst effect came from collection with sand on the bottom of the tanks with the metamorphosis success of only 20%. From the experiments, we found out that collection with sand in floating cages and collection with substrates of scallop and sand hanging in the tanks to be two ideal seedling collection methods which had a good impact on promoting the metamorphosis success rate, growth rate and survival rate of spat of A. pectinata.In a collaboration of three years efforts, one million spat with average size of 2.2mm were reared with an average output of 13.4000/m~2, and a set of technique of productive scale seedling rearing of A. pectinata was created, which is in the leading level of China.