Influence of food quality
and quantity on the growth and development of Crassostrea gigas
larvae: a modeling approach
E.N. Powell, E.A. Bochenek, J.M. Klinck, E.E.
Hofmann-2002
Aquaculture, 210(1-4): 89-117
Abstract:
A biochemically based model was developed to simulate
the growth, development and metamorphosis of larvae of the Pacific oyster, Crassostrea
gigas. The model is unique in that it (1) defines larvae in terms of
their protein, neutral lipid, polar lipid, carbohydrate and ash content; (2)
tracks weight separately from length to follow larval condition index and
(3) includes genetic variation in growth efficiency and egg quality to
better simulate cohort population dynamics. The model includes
parameterizations for larval filtration, ingestion and respiration that
determine growth rate and processes controlling larval mortality and
metamorphosis. Changes in tissue composition occur as the larva grows and in
response to the biochemical composition of the food.
The simulations show that genetically determined
variations in growth efficiency produce significant changes in larval
survival and success at metamorphosis. Larvae with low growth efficiency are
successful under a much narrower range of culture conditions than larvae
with high growth efficiency. The impact of low growth efficiency is
primarily controlled by the ability of larvae to store lipid for
metamorphosis. Culture conditions that provide increased dietary lipid
counterweigh low growth efficiency. Changes in food quantity and quality had
little effect on size at metamorphosis. On the other hand, larval life span
and success rate at metamorphosis varied over a wide range depending upon
the conditions of the simulation. Food quality and food availability both
influence larval life span and, hence, larval survival. As ingestion rate
decreases, larval life span increases and cohort survival declines.
Increased lipid or decreased protein in the diet improves cohort survival.
Changes in carbohydrate content are less influential. If cohort success is
significantly affected by mortality during larval life rather than success
at metamorphosis, the influence of food quality becomes more complex. The
range of food compositions yielding high survival is restricted by a balance
between improved success at metamorphosis obtained by increased lipid
storage and the shortening of larval life span as a result of more rapid
growth, a function of protein availability. These simulations illustrate the
strength and utility of numerical models for evaluating and designing
hatchery protocols for optimizing yield of C. gigas larvae.