New expedition

Osa Peninsula

Chris Thompson | March, 2019

Chris Thompson

April – May, 2018

  Cover image

Isla del Caño, Costa Rica.
Photo: Chris Thompson

SUMMARY

In March 2019 the Marine Futures lab was involved in a three-week expedition to the Osa Peninsula, Costa Rica aboard the Undersea Hunter vessel, Argo. The expedition was led by National Geographic Pristine Seas in collaboration with Osa Conservation and the Universidad de Costa Rica.
The Osa Peninsula is famous for its terrestrial fauna. It is home to the largest national park in Costa Rica, Corcovado National Park, described as the most biologically intense place on the planet and providing a home for 2-3% of the world’s terrestrial biodiversity within its 424 square kilometers. On this expedition, we set out to sample the much less known waters of this coast, and discover if they harbor a similar richness.
Multiple sampling teams conducted comprehensive sampling from the shallows surrounding the peninsula down to the deep sea and to the blue waters surrounding it. Divers conducted Underwater Visual Census’ of the coastal fish life and invertebrates, the Deep See submersible conducted surveys down to 400 m including investigations of some interesting methane seep environments, the National Geographic deep DropCams sampled deeper waters and the pelagic assemblages surrounding the island were assessed using mid-water baited remote underwater video systems (BRUVS).
The waters surrounding the already protected Isla del Caño were thick with fish, with huge schools of grunts, snapper, and barracuda. Humpback whales were seen cruising down the coast, as the Golfo Dulce to the south of the Peninsula is the only place in the world known to be frequented by both northern and southern humpback whales. The pelagic waters were thick with jellies and other zooplankton forming the basis for a rich ecosystem. Turtles were regularly seen resting on the surface and sailfish were plentiful, often seen leaping out of the water. Bait balls with tuna and pantropical spotted dolphins feeding in large numbers along with diving seabirds were a common sight. Conspicuous by their absence were oceanic sharks with only one blacktip observed on our mid-water camera systems in an otherwise rich pelagic community. Fishing pressure on sharks is known to be high in this region and we hope that the protection of these waters will provide an effective refuge and allow their populations to rebuild. A community event held in Agujitas showed promise with great community engagement from locals, academics and government officials alike.

01

OSA PENINSULA COMMUNITY

Local children getting involved in the community event at Agujitas, adding the finishing touches to a mural by artist Carlos Hiller

02

IN THE WATERS OF OSA PENINSULA

An Indo-Pacific sailfish (Istiophorus platypterus), Leopard round stingray (Urobatis pardalis) and Pantropical spotted dolphins (Stenella attenuata).

03

JELLY SNACK

An olive ridley sea turtle (Lepidochelys olivacea) about to eat a ctenophore

04

HIDDEN IN THE CORAL REEFS

Hancock’s blenny (Acanthemblemaria hancocki)

05

EXPLORING THE DEEP

The DeepSee submersible beginning its descent

FUNDING & ACKNOWLEDGEMENTS

This expedition was undertaken aboard the Undersea Hunter vessel, Argo. A National Geographic Pristine Seas project in collaboration with Osa Conservation and the Universidad de Costa Rica.