This is a guest post by Andrew McKay, who is a trained ecologist and currently works in fisheries in New Zealand. In his spare time he writes about peak oil and energy issues at Southern Limits.

Within the fields of harvest and fisheries management catch per unit effort (CPUE) is one method that is used to determine the health of a biological resource. The underlying assumption is that as a population declines it becomes harder to catch and therefore CPUE decreases.

Effort can be measured in a number of ways. In fisheries this unit of effort could be vessels in a fishery, days fished, hours fished, number of tows or sets in a season or any number of other units of measurement. Theoretically these should all show similar results.

As a very basic example of CPUE, if in the first year a vessel fishes 10 hours per day for the season and catches 4,500,000 kg of fish and in the second year still fishes 10 hours per day for the season and catches only 2,000,000 kg of fish the CPUE has dropped from 5000 kg/hr to 2778 kg/hr. A standardised CPUE would show a drop from maximum catch of 100 (the maximum of the data set) in the first year to 56 in the second year. A drop of almost half.  All other things being equal this would give fisheries managers reason for concern as the effort has stayed the same while the catch has decreased. However, an increase or no change in catch can also sometimes mask an underlying problem. If in the second year the vessel fishes 15 hours per day for a season and still catches 4,500,000kg the CPUE drops to 3333 kg/hr. This is a standardised CPUE of 67. This represents an increase in effort for the same amount of catch.

There are a number of limitations to CPUE in fisheries management that largely come from fish stocks being highly mobile, impacted by a number of environmental conditions, disease and predation from other species. That being said, what if we applied the concept of CPUE to a non-biological resource such as oil? What if instead of catch per unit effort we calculate production per unit effort (PPUE)? This is exactly what I am proposing and what the rest of this post will address.

Production Per Unit Effort (PPUE)

In the case of oil these units of effort could be number of rigs, footage drilled or money invested. We can hypothesise that when peak oil occurs we would expect to see PPUE decline for all these factors. As rig numbers increased the amount of production would decrease, as footage drilled increased the amount of production would decrease and as the money invested increased the amount of production would decrease.

I have standardised the PPUE figures below so that they can be easily compared across all regions. The basic calculation is simply to divide the production figure (thousands of barrels per day) by the corresponding unit of effort for each year. This is then standardised by dividing each figure by the largest figure in the data set and then multiplying by 100 to assign a ranking of 1 to 100. A PPUE of 100 represents a minimal amount of effort for the maximum amount of production while a PPUE of 1 represents a large amount of effort for minimal production. Obviously it is in the best interests of oil producing nations to be at the upper end of this scale. From what I have calculated below this is by and large not the case. The majority of regions around the world are facing falling PPUE which signals one thing: oil is getting harder and harder to get out of the ground. If this is indeed the case then high oil prices are here to stay and will only continue rising in the future.

via The Oil Drum – Discussions about Energy and Our Future http://www.theoildrum.com/node/10026