Growth and survival of larval and early juvenile Lesser Sandeel in patchy prey field in the North Sea: An examination using individual-based modeling

Abstract

Disentangling physical–biological interaction processes during early life-stages of fish is crucial for the understanding of fish stock recruitment. Among many individual and environmental aspects affecting mortality during the early life-stages of fish, encountering food at greater than average concentrations is regarded important for survival. Intense aggregations of zooplankton in near-surface waters provide these conditions for larval fish. Simulation studies by individual-based modeling can help understanding of the mechanisms for survival during early life-stages. In this study, we examined how growth and survival of larvae and early juveniles of Lesser Sandeel (Ammodytes marinus) in the North Sea are influenced by availability and patchiness of the planktonic prey by adapting and applying a generic bioenergetic individual-based model for larval fish. Input food conditions were generated by modeling copepod size spectra dynamics and patchiness based on particle count transects and Continuous Plankton Recorder time series data. The study analyzes the effects of larval hatching time, presence of zooplankton patchiness and within patch abundance on growth and survival of sandeel early life-stages in the North Sea. Simulations of patchiness related starvation mortality are able to explain observed patterns of variation in sandeel growth. Reduced prey densities within patches decrease growth and survival rate of larvae and match–mismatch affect growth and survival of larvae with different hatch time due to plankton seasonality. Of general scientific and environmental management interest, the results indicate a steep threshold concentration critical for survival at around 0.04–0.05 no. zooplankton/mL.