Academic proposes ‘optimal control model

Brian Tobia
The international tuna fishery is on the brink of being over-exploited for less than marginal profit.

This was revealed by Professor Tom Kompas of the Australian National University at a recent PNG Economic Update seminar in a paper titled “Tuna Resource Management: Economic Profit and Optimal Effort in the Western and Central Pacific Tuna Fisheries”.

He said the tuna resource in the Western and Central Pacific is in danger of being over-exploited due to the more open-access granted to foreign fishing companies and vessels, and the use effective modern fishing technologies.

He warned that if this trend continues, tuna stocks will be depleted and harvest of the fishery will decline, thus directly affecting profit levels of countries in the Western and Central Pacific (including the Pacific States) which depend on tuna for bulk of their revenue.

He said the situation could be prevented if the tuna resource is managed effectively by reducing catch levels to sustain the resource in the long-term.

“There are few international fisheries (if any) that will not be over-exploited and less than fully profitable unless they are managed effectively.

An economically efficient outcome is important not only because it protects fish stocks and guarantees sustainability, but because it ensures resources are allocated correctly and in a way that maximises returns,” he said.

He said the solution to this imminent problem is to use a ‘optimal control model’ to manage the distribution of gear types used over a 50-year planning horizon.

Emphasis should be placed on controlling the harvest of the three main species—yellowfin tuna, bigeye tuna and skipjack—and the distribution of four gear types or fishing methods used (that include purse-seine, pole-and-line, frozen tuna and fresh tuna longline) to each fishery.

Purse-seine and longline contribute more than 75 percent of the total catch of yellowfin tuna.

He said a substantial effort is required to reduce the harvest of these tuna species and controlling and managing catch at low levels to enable stocks to increase in size and population.

WCPTF is diverse and involves small-scale artisanal operations in the coastal waters to large-scale, industrial purse-seine, pole-and-line and long line operations in the exclusive economic zones (EEZs) of Pacific States and on the high seas.

It is one of the largest and most valuable tuna sources in the world, providing approximately two million metric tonnes per annum or half of the global tuna supply and plays a vital social and economic role in the region generating about US$3 billion a year, said Kompas.

WCPTF has also been a food source and important foreign currency earner in terms of licence fees and exported products.

Total fish landed in the WCPTF has been increasing steadily since 1950 at a rate of 5 percent a year.

Fishing effort in the WCPTF has been growing rapidly in that total boat-days for purse-seine fisheries have increased on an average at a rate of 10 percent a year between 1970 and 2000.

But in 2004, total fishing effort for the purse-seine fleet was more than 70,000 boat-days.

Likewise, total hooks increased from more than 100 million in the 1950s to 700 million hooks in 2004 for longline fisheries.

But this trend (increase in purse-seiner fleet and total boat days and the increase in the number of hooks) has gradually depleted tuna stocks in Australia prompting Australian companies to seek open access into EEZs of Pacific states.

Based on this, a bio-economic analysis of the region was done on stock assessment and a stock recruitment relationship resulting in the development of a ‘bio-economic model of WCPTF’ aimed at reducing fishing from the 2004 levels.

It recommended that largest cuts must occur in the purse-seine fishery. Effort must also be reduced in the frozen and fresh longline fishery.

Reductions must be made to allow stock recovery and increased profits through reductions in per unit costs of fishing.

Increase in profits from this change would be substantial in the order of 30 percent per annum. The move would also allow for increased licence fees by Pacific islands states.

He warned that countries in WCPTF would experience a substantial loss in profits if nothing is done to resolve the problem of over exploitation.

Additionally, reduction in harvest will create a demand for species on the market and push prices up.