DEPENSATION IN FISH STOCKS - A HIERARCHICAL BAYESIAN METAANALYSIS

The probability of different levels of depensation within four taxonom ic groups was calculated using a Bayesian technique called hierarchica l modeling. With this method we combined spawner-recruit data from man y stocks within a taxon to estimate the distribution describing the va riability of depensation within that taxon. The spawner-recruit model we use allows for both depensation (lower than expected recruits at lo w population levels) and hypercompensation (where recruits are higher than expected at low population levels). The end product of our analys is is a probability distribution that can be used as a Bayesian prior when analyzing a new data set. We examined four taxonomic groups (the salmonids, gadiforms, clupeiforms and pleuronectiforms) and found that , for all of the taxa, the most likely values fell close to or within the range of no depensation. However, because the distributions were v ery broad we suggest that analysis of stock recruitment data should in corporate spawner-recruit curves that include the possibility of depen sation and hypercompensation.