Effect of turbulence on feeding of larval fishes: a sensitivity analysis using an individual-based model

Recent research has shown that turbulence can be important in the feeding o f larval fishes. The interplay of turbulence with other important factors a ffecting larval feeding and growth rates is less known because of the diffi cult problems associated with multi-factor in situ experiments. We use an i ndividual-based model (IBM) of the early life stages of walleye pollock (Th eragra chulcogramma) to examine the sensitivity of growth and mortality to turbulence. This probabilistic and mechanistic model follows individual fis h through the egg, yolk-sac larvae, feeding larvae, and juvenile stages, an d includes development, behaviour, feeding, bioenergetics, and growth for e ach life stage. Biological processes are driven by physical factors (temper ature, salinity, and turbulence) derived from a companion hydrodynamic mode l and configured for environmental conditions prevalent in 1987. A foraging submodel explicitly incorporates the effect of turbulence, prey density, a nd larval size. Monte Carlo simulations using Latin Hypercube Sampling meth ods were used to perform a sensitivity analysis. The error analysis examine s the relative importance of various feeding-related factors on larval grow th and mortality. Model results conform to wind-induced turbulence/contact- encounter rate theory with maximum consumption rates occurring at windspeed s of 7.2 m s(-1). Reactive distance, minimum pursuit time, and weight-lengt h conversion parameters were the most important input parameters affecting the turbulence-consumption processes. The rank order of important input par ameters shows that the weight-length conversion power coefficient and react ive distance (directly through the reactive distance-length proportionality coefficient) were two factors that influenced the largest number (17 out o f 24) and largest percentage (71%) of output variables. Feeding depth was r anked third, influencing 50% of the output variables. Our results show that smaller and younger larvae are more sensitive to turbulent effects than ar e larger and older larvae.