Tag 11-4482 · Western & Central Pacific

The long way round

One skipjack's year, logged the way you'd log a season of Brumley bike rides. The profile below is a dive profile. It is also, if you turn your head, an elevation profile.

Skipjack · Katsuwonus pelamis 3.6 kg 184 days at sea

day — · — m · —

Distance—km

Elapsed184d

Avg depth—m

Max depth—m

Total descent—km

Jurisdictions8

Segments

Same swim, cut into the waters it happened to be in. The fish did not notice the transitions; the paperwork did.

departs Solomon Sea184 days later

Water	Days	Avg depth	Vessel days sold

What a vessel day is

Eight Pacific states — the Parties to the Nauru Agreement — sell access to their waters not by the tonne of fish but by the day of fishing. They agree a total number of days across all their waters, split it between themselves, and sell those days to whoever bids highest. Days can be traded between countries. Roughly half the world's skipjack comes from the water this scheme governs.

It is a quietly radical piece of design. Selling tonnage rewards whoever catches most; selling days caps the effort and lets eight small states set the price together, against fleets from much larger economies. The fish above swam through all of it without once being told.

Comments

Purse seiner · day 63

saw you out there. couldn't stay — out of days.

OBS

Observer, WCPFC · day 96

Logged. Set was on a free school, not a FAD. Noted for the record.

Geographer · today

Eight sovereignties, one continuous swim, and not a single border in the water. Happy birthday, Elizabeth.

Kudos from 3 purse seiners, 1 observer, and everyone who has ever tried to govern something that keeps moving.

What's real here, and what isn't

The fish is a composite. There is no tag 11-4482. The track, the daily depths and the day counts are generated to be plausible, not transcribed from a real animal.
The behaviour is real. Skipjack sit above the thermocline at night and bounce-dive below it through the day, typically working the top ~260 m; the deepest recorded dive is 596 m, at 7.7 °C. That diel sawtooth is what makes the profile look like terrain.
The rules are real. The Parties to the Nauru Agreement are eight sovereign states — Federated States of Micronesia, Kiribati, Marshall Islands, Nauru, Palau, Papua New Guinea, Solomon Islands and Tuvalu — with Tokelau a ninth participant. The Vessel Day Scheme caps and sells purse-seine days, allocated per country and tradeable between them.
The argument is someone else's, and better made in Rights-based management in the Western and Central Pacific Ocean tuna fishery (2013), Science, scale and the frontier of governing mobile marine species (2016), and Unsettled sovereignty and the sea (2021).

Sources for the two factual claims above: PNA on membership and the scheme, and Kitagawa et al. on skipjack diving behaviour.

Made for a geographer · ppr3.com