SEASONAL PLANKTON CYCLES IN A TEMPERATE FJORD AND COMMENTS ON THE MATCH MISMATCH HYPOTHESIS

As a field test of the 'match-mismatch hypothesis' (Cushing, 1972, 1975, 1990), we sampled the ichthyoplankton and different size fractions of zooplankton at two stations in a temperate fjord (Dabob Bay, Washington, USA) between May 1985 and October 1987. We present the results of this study together with historical data on seasonal abundances of phytoplankton and invertebrate predators. The peak abundance of fish larvae in late winter/early spring preceded the peak abundance of prey organisms by an average of 3 months. Correlation analysis resulted in one negatively significant and three non-significant correlations between ichthyoplankton and appropriately sized prey organisms. These field observations, showing a distinct temporal lag between abundances of larval fish and their zooplankton prey, do not support the match-mismatch hypothesis as originally formulated. We use these field data and a simulation model of the growth of young fish to discuss the role of two alternative processes-food limitation during late larval/juvenile stages and predation-that may constrain the timing of spawning of marine fish and which may have implications for recruitment variability as well. This leads us to propose that the match-mismatch hypothesis be extended to include a 'critical period' that lasts longer and occurs later in the life history of marine fish than has previously been supposed.