Harvest efficiency in the production functions of fisheries should increase over time with the introduction of new technology and with increasing knowledge of the biology and behaviour of the target species. This implies that the estimated catchability coefficients of Gordon-Schaefer or Fox...

A microscopic, soil-borne fungus has been gradually spreading through the Jarrah forest of W.A. for most of this century. On some sites this fungus can cause almost total forest destruction. Infection is incurable and the effects are irreversible. This paper develops a means for evaluating...