Finding Hemingway’s Marlin

‘He’s headed north,’ the old man said. The current will have set us far to the eastward, he thought. I wish he would turn with the current. That would show that he was tiring.

Ernest Hemingway – The Old Man and The Sea

Hemingway's Marlin

In American literature, swordfish and marlin are symbols of our ocean obsession and an underlying quest for wealth. With massive population growth and technological advancement in the late 20th century, large-scale industrial fisheries are equipped with swaths of data on where these animals live. Fishing operations have depleted billfish populations and we’re now tasked with maintaining a healthy reserve. Population management is broken up into discrete geographical stocks across the world’s oceans, overseen by fisheries, government organizations, and research institutions.

Swordfish Migration

Because no centralized dataset exists, scientists pull most of their information from individual fisheries. A research team out of Italy gathered anecdotal data from fisherman’s logbooks and sea-vessel observations, to draw swordfish heat maps across the Tyrrhenian Sea. Climate change has a profound effect on these maps. They found that a spike in sea surface temperature in 2003 caused a drastic habitat redistribution and pulled the fish out of their normal feeding range. Goodyear et al avoided fishing data altogether, and produced three-dimensional maps that represent the physical form of the marlin’s habitat. The team noticed that temperature fluctuations are able to contort and displace the amorphous habitat models. Contemporary fisheries do not consider these changes in ocean temperature during routine stock assessments.

Marlin Habitat

The National Oceanic and Atmospheric Association developed the satellite system Argos to monitor marine animals with computer hardware. Over 100,000 sailfish are currently equipped with pop-up satellite archival tags, which send out real-time data as the animals move through the ocean. Armed with the precise location of our world’s sea life, governments will gain regulatory power over fisheries. For the general public, will this knowledge diminish the mystery of the unknown ocean?

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