Spawner-recruit relationships and fish stock carrying capacity in aquatic ecosystems

Few marine ecologists have addressed important questions about the relative productivity and carrying capacity of different ecosystems required to support fish populations. Whereas many researchers have investigated interannual variability in recruitment within a stock, we asked whether relationships between spawner abundance and subsequent recruitment are similar among populations (n = 3 to 20) of the same species, and among species (n = 14).

We found that a large and significant amount of the variation (R 2 = 75 to 95 %) in mean- log recruitment is explained by mean-log spawner biomass when the spawner-recruit relationship is examined among populations of the same species. The slopes of these relationships are close to 1 (i.e. proportional).

However, mean recruitment per spawner varies greatly among species (range 3 to 10). Some ecosystems allowed cod Gadus morhua, haddock Melanogrammus aeglefinus and herring Clupea harengus populations to produce an average of ca. 8-fold more recruits per spawner than other ecosystems. Also, the abundance of at least 1 species (cod) is strongly related to habitat size.

Reasons for the differences in recruit production per spawner between ecosystems are unclear, but the differences themselves may need to be considered in marine ecosystem management contexts.