Empirical and quantitative analysis of marine fish larvae dynamics

This dissertation investigated growth variability of larval fish, size-selective predation upon them, and their population dynamic response. Larval fish dynamics were investigated using: a general analytical model, an individual-based simulation model, and, a multi-cohort comparison of empirical growth.A generalized analytical model described time-dependent cohort size, both in current numbers and cohort biomass. The model takes larval growth rates in length and weight into consideration when calculating larval mortality. Increases in prey biomass were dependent on growth in weight, mortality and decreases in numbers, N(t), and, cohort biomass, B(t), both dependent on predator size, search volume, capture efficiency, and initial larval cohort biomass, current biomass, and growth in length. Small search volumes equaled high predator densities, high encounter rates, and high larval mortalities. Large volumes equaled low predator densities, low encounter rates and low mortalities.A numerical model estimated cohort survivorship, S(t), B(t), and size frequency distributions of surviving larvae. Predator ration was added to balance the trophodynamics between cohorts and predator. At small search volumes, S(t), and B(t), were not just dependent on the interaction between the B(0), and current biomass, B(t), but also on predator ration. At intermediate volumes, average predator ration reached a maximum.Size distributions were affected by size-selective predation leading to slightly higher presence of larger size classes and removal of smallest sizes. Partially size-independent reaction distance displayed higher intermediate size classes, causing the distribution no longer to be skewed.Empirical data of spotted seatrout exhibited variation in growth rates during specific early life history stages. Developmental stage-specific growth was variable at intra- and inter-cohort levels. Growth rates were parabolic with a maximum during the period from flexion into post-flexion. Growth rates of younger larvae were less significant in determining overall average growth rates.Comparison between models revealed a transition in biomass and change from negative to positive growth rates. Research suggested a Flexion-Transition Period (FTP) where growth maximized biomass increase. Environmental conditions during this period may have implications for recruitment success and sustainable fisheries production