Early in the time series there may be stations with a 0 in either biomass or abundance which then turns the stratified means into zeros. This was noted in the mackerel index for Georges Bank in Spring of 1969. There is a chance that individual strata are being zero'd out but masked with other strata when summed.
Early in the time series there may be stations with a 0 in either biomass or abundance which then turns the stratified means into zeros. This was noted in the mackerel index for Georges Bank in Spring of 1969. There is a chance that individual strata are being zero'd out but masked with other strata when summed.