Effects Of Environmental Factors On Metabiolism And Growth Of Hard Clam Mercenaria Mercenaria

With the swift development of mariculture, the self-pollution of mariculture and its effect on the coastal ecosystem became more serious, so it's very need to conduct the studies on interaction between the filter-feeding bivalve farming and coastal ecosystem and it is also very benefit for the protection and restoration of the coastal ecosystems and the sustainable development of filter-feeding bivalve culture.In this dissertation, preliminary studies on effects of environmental factors on metabiolism and growth of hard shell clam Mercenaria mercenaria had accomplished in the fields and laboratory. Results as follows: 1 The salinity range suitable for juvenile survival and growth was 18-42, and the optimum range was 24-36. According to the survival rate and daily growth rate, the consequence of raised effect of different diets is Isochrysis galbana>Isochrysis Tahiti> Dicrateria sp.>mixed algaes(Isochrysis Tahiti mixed with Chlorella sp.)>Chlorella sp.>Platymonas subcordiformis >Spirulina>DHA(substitutional diet). Hard clam had some selection on substrate, the survival rate and daily growth rate of larval and juvenile in the sandy sediments were higher than that in the clay sediments. 2 The relationship between individual oxygen consumption rate and its dry fresh weight under different temperature could be expressed by OR=aWb, where OR is oxygen consumption rate(mgO2?ind-1h-1), W is individual dry fresh weight(g), and a ranged from 0.05 to 0.70, b ranged from 0.45 to 0.65. The ammonia-N excretion rate-temperature curve was unimodal, the maximum ammonia-N excretion rate per gram dry fresh weight was about 25℃. The relationship between individual ammonia-N excretion rate and its dry fresh weight under different temperature could be expressed by NR=aWb, where NR was ammonia-N excretion rate(μgNH4-N?ind-1h-1), W was individual dry fresh weight(g), and a ranged from 1 to 27, b ranged from 0.40 to 0.75. The oxygen consumption rate of hard clam slightly decreased with the salinity decreased when salinity was between 16 and 31, and with the salinity increased, OR decreased, when salinity was above 41, OR increased in reverse. When salinity was between 21 and 41, with the salinity decrease or increase, the NR of hard clam was decreased.3 The ingestion rate of M. mercenaria havn't distinct change between 15℃ and 30℃. When temperature was below 10℃, ingestion rate was decreased. M. mercenaria has the highest clearance rate in natural sea water, with the salinity decreased or increased, CR decreased, and in the high salinity, CR decreased more distinctly when salinity was above 41 or below 21. The relationship between individual CR and its dry fresh weight under different temperature could be expressed by CR=aWb, b ranged from 0.34 to 0.60. Temperature and salinity hadn't distinct effects on assimilation rate of M. mercenaria . The assimilation rate of hard clam ranged from 0. 3 to 0.7 between 10℃ and 30℃ and ranged from 0.23 to 0.80 when salinity was between 16 and 46.4 The effect of salinity on scope for growth of M. mercenaria was distinct, the mature individual had highest scope for growth(242-520J?g-1?h-1) when salinity was between 26 and 36, and juvenile had the highest scope for growth in natural sea water. With the salinity increases, scope for growth of M. mercenaria decreased distinctly, and occured negative growth at 46. 5 Three algaes had different raised effects on M. mercenaria, and the consequence was Isochrysis galbana> Isochrysis galbana > Chlorella sp.