An integrated system for microalgal and nursery seed clam culture

A PC-controlled integrated system for the production of algae and culture o f northern quahog seed was constructed. The diatom, Chaetoceros muelleri, w as cultured in covered 550 l tanks. The harvested alga was the food source for the land-based nursery seed clam system. The nursery clam system consis ted of six culture units constructed of clear PVC tubing, a 400 l feed rese rvoir, a solids separator, and a bead filter (0.03 m(3)). The culture units were 5 cm in diameter and 76 cm in height. The total system volume was 450 l and the recirculation flow rate was 40 Ipm. Components of the computer c ontrol system include a laptop computer, a multiport connector, analog to d igital converter (ADC) boards, and solid-state relays for each control outp ut. Sampling, harvesting, refilling, and redosing of the algal chambers, se ed clam feeding operations, cleaning of the seed bed by increased fluid flo w, purging of the separator wastes, and backflushing of the bead filter wer e all computer controlled. The integrated system was tested using Mercenari a seed clams. The initial shell length of the seed clams were 2.5 (+/- 0.5) mm, and were stocked at a density of 3.0 g whole wet weight cm(-2). During 83 days of culture using the system the seed clams were sorted twice and r eached an average shell length of 7.9 (+/- 0.8) mm. The percentage of survi val percent was determined at different stages of growth during the culture period and ranged from 67.3 to 88.0%. (C) Published by Elsevier Science B. V.