The Relative Importance of Spawning Stock Biomass and Environmental Conditions in Determining Recruitment in Marine Fishes: a Meta-Analysis

The assembly of a large data base on spawner recruit relationships by Ransom Myers in the 1990s led to considerable advances in large scale evaluation of the relationship between spawning stock and recruitment for marine fishes and showed that recruitment overfishing was indeed common when spawning stocks were driven to low levels.  An alternative hypothesis proposed by Dave Gilbert is that recruitment comes in periods of high and low recruitment driven by environmental regimes.  During periods of high recruitment, spawning stock is higher, and during periods of low recruitment spawning stock is lower.  Thus Gilbert proposed that what appears to be a relationship between spawning stock affecting recruitment, may in fact be a relationship between recruitment affecting spawning stock, and that concern about recruitment overfishing may be exaggerated.  We conducted a meta analysis of marine stock recruitment relationships, pitting a traditional spawner recruit model against a regime shift model as proposed by Gilbert.  We found that there is far more support for the regime shift model than for recruitment depending upon spawning stock.  We discuss the implications for fisheries management.