Fish stocks and fishing intensity by group, Tuna

Fish stocks are measured by biomass: the number of individuals multiplied by their mass. Fishing intensity by thefraction of the fish population that is caught in a given year.Both are given as a ratio of their levels at the maximum sustainable yield – the level at which we can catch themaximum amount of fish without a decline in fish populations. A value of one maximises fish catch withoutdecreasing fish populations. This is the target level.