Growth and reproductive patterns in Venerupis pullastra seed reared in wastewater effluent from a fish farm in galicia (n.w.spain)

摘要

The use of effluent water from a turbot (Psetta maxima) farm for culturing Venerupis pullastra juveniles (seed) was evaluated. Reproductive activity, growth, condition, and survival rate were investigated. After a 2-mo acclimation period, clam seed (mean live weight = 360 +- 18 mg SD mean length = 14 +-1.7 mm SD) were grown from June 30 to November 20 of 1993 in three different flow-rates of wastewater. Thirty individuals were sampled from each tank biweekly. Stability in the main environmental parameters of the effluent (temperature, salinity, oxygen, etc.) provided good conditions for seed growth. After the acclimation period, mortality was less than 18%. Growth-rate coefficients (K values) of V. pullastra were correlated positively with increase in the effluent flow and were significatnly hihger than in the control taks (K = .001). Shell length (27.4 +-1.8 mm SD) and , in particular, live weight (2,907.6+-530.9 mg SD) were highest in tanks with a flow of 4 vol/h and these tanks also produced the fastest growth rate (K = .0445). In tanks with flows of 1 vol/h and 2 vol/h, final weights and lengths were 1.823 +-273.2 mg SD, 23+-1.8 mm SD and 2,361 +-351.4 mg SD, and 25 +-1.4 mm SD, respectively. Condition indices of clams followed a similar pattern reaching final values ranging from 18 to 28 and were significantly higher than in the control tanks. High condition index values might be due mostly to the high amount of food present in the effluent water throughout the experiment. Stereological and histological techniques were used to determine gametogenic activity. Successive spawnings and recovery of the gonad. which are characteristic of this species, were noted in clams in experimental tanks. However, they occurred in a shorter time period. Results suggest that it is possible to rear V. pullastra seed under these special culture conditions and that a better balance between volume of effluent used and clam productivity was achieved with a flow rate of 2 vol/h.