Effects of locally-isolated micro-phytoplankton diets on growth and survival of sea scallop (Placopecten magellanicus) larvae

The micro-phytoplankton Navicula pelliculosa, Chaetoceros septentrionalis and Prymnesium sp., indigenous to the coastal waters of Nova Scotia, Canada were isolated, cultured and used in laboratory feeding experiments with larvae of the giant sea scallop (Placopecten magellanicus) to evaluate their dietary benefits. The effects of these micro-phytoplankton on larval growth and survival were compared with three species of micro-algae commonly used as commercial feed for bivalve larvae: Tahitian Isochrysis sp., Pavlova lutheri and Chaetoceros calcitrans. The experiments were conducted at 14 °C over approximately one month. Larvae were fed at concentrations of 25,000 cells ml−1 from Day 3 to Day 9 and 35,000 cells ml−1 from Day 10 to Day 35. Total growth and survival were determined by sampling the larvae at intervals of 4 to 5 days. Eight dietary formulations were compared for larval survival and growth. Two way, repeated measures ANOVA using both larval shell height and percent larval survival as dependent variables and diet and time as factors resulted in significant variation (p < 0.001) in both larval growth and survival. Prymnesium sp. supported significantly better growth as a monospecific diet than local Chaetoceros or Navicula, and when used in combination with the commercial diets which included other flagellates. Local Navicula and Chaetoceros were found to be better diets for the later stages of larval growth. Our studies showed that these two local diatoms Navicula pelliculosa and Chaetoceros septentrionalis could also be used as a component of multispecies diets along with flagellates.