The new goldfields
Study reveals large un-fished stocks of skipjack tuna in Cook Islands waters, estimated to be worth hundreds of millions of dollars

Friday 23rd March 2012 – A stock assessment carried by the French Space Agency (CSL) for the Ministry of Marine Resources (MMR) has estimated 190,000 tonnes of skipjack tuna in Cook Islands waters.
According to the report most of skipjack are found in the northern Cook Islands north of 15 degree latitude above Suwarrow with the adult fish foraging in the equatorial waters above 10 degrees latitude, i.e. north of Manihiki.
Skipjack tuna are short lived species that mature at 10 months of age and because of their rate of breeding the population can withstand high levels of fishing pressure.
Assuming a sixty per cent harvest the MMR estimates that up to 110,000 tonnes of skipjack tuna could be fished. At a landed value of US$2 per kg, the fishery would be worth several hundreds of millions of dollars.
The latest stock assessment is significantly greater than the confidential estimates that MMR had provided Cabinet prior to launching its skipjack tuna exploratory fishing report. The under-estimate occurred because the historical model is biased towards areas with catch data and is limited by assuming a constant density and operates at the scale of 5 degree blocks.
The MMR commissioned a consultancy with CSL to use advanced space technology and satellite images to carry out a stock assessment using the SEAPODYM model. This highly advanced modelling software is less dependent on fishing data and uses environmental parameters such as ocean productivity, detailed population age structure and trophic interactions and is able to estimate skipjack tuna biomass at much finer resolution then previous models.
MMR Secretary Ben Ponia says that the timing of this information is useful because next week commission members of the Western Central Pacific Fisheries Commission (WCPFC) will meet in Guam to discuss measures to limit the catches of skipjack tuna and “we now have some scientifically credible data to show that the Cook Islands have a right to participate in this fishery, even if we are not currently exercising that right at the moment”.
At present only US flagged purse seine vessels are allowed to target skipjack in the Cook Islands waters, provided for under a US multi-lateral fisheries treaty signed in 1984. The treaty is currently being renegotiated with some members of the PNA tuna cartel demanding that the US pay up to US$10,000 dollars a day for every day a purse seine vessel fishes or searches in its waters.
In reality very few purse seine vessels fish in the Cook Islands although there has been a recent spike in activity possibly related to the La Nina conditions.
While Ponia believes that the results of this survey indicates that skipjack tuna could be one of the most valuable natural resources after seabed minerals he cautions that the catch-ability of skipjack remains to be proven and whether a fishery can be established. For example whether the currents are suitable for FAD fishing and if weather conditions will be calm enough to detect and fish free schools are some of the factors that need to be taken into account.
According to the report the average catch of skipjack tuna in Cook Islands waters is 1,851 tonnes a year which varies depending on the ENSO cycle. This catch is just 0.16% of the total WCPFC regional catch, even the Cook Islands has 2.89% of the total biomass. In comparison the western high seas pocket (i.e. international waters) accounts for 13.68% of the total regional catch, even though the amount of skipjack biomass in these waters is estimated at half the quantity found in the Cook Islands waters
The estimates are rather promising for the Cook Islands and the most favourable zone is north of 10 degrees south as expected says the lead author of the report, Dr Patrick Lehody, “There is likely a good potential that needs to be prospected and monitored carefully”, he added.
The Cook Islands Maori name for skipjack tuna is Au’opu.

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