Summary: Hydrobiologia 484: 4959, 2002.
O. Vadstein & Y. Olsen (eds), Sustainable Increase of Marine Harvesting: Fundamental Mechanisms and New Concepts.
© 2002 Kluwer Academic Publishers. Printed in the Netherlands.
The influence of turbidity on growth and survival of fish larvae:
a numerical analysis
Řyvind Fiksen, Dag L. Aksnes, Magni H. Flyum & Jarl Giske
Department of Fisheries and Marine Biology, University of Bergen, P.O. Box 7800, N-5020 Bergen, Norway
Key words: larval feeding, model, phytoplankton concentration, recruitment, turbidity, vision
Growth and survival through the early larval phase probably limit the production potential of many commercially
important fish stocks. Attempts to increase the production of these stocks by restocking of juveniles have generally
failed. Here, we analyse how enhanced concentrations of phytoplankton and zooplankton affect the survival of fish
larvae during their early life stages. The analysis is developed for larvae feeding on copepod eggs and nauplii,
with fish and invertebrates as major predators. A model of feeding and growth of fish larvae is applied to assess
the benefit of enhanced phytoplankton and zooplankton abundance. The analysis shows that the shading effect of
higher phytoplankton concentration may reduce predation rates on fish larvae substantially. This `top-down' effect
may be more important for the cohort survivorship than the `bottom-up' mechanism in situations when larval food
is sufficiently abundant. However, while increased algal biomass will improve recruitment at high zooplankton