Open Wide

Deep-sea fish have large gapes so they can eat everything they encounter, which might make them resilient to ecosystem changes, says postdoctoral researcher, Dr Monique Ladds.

View from the captain’s deck of the Tangaroa on the Chatham Rise. The front of the ship is shown clearly with the ocean and various seabirds out ahead.
View from the captain’s deck of the Tangaroa on the Chatham Rise.

Last summer, Monique spent a month on board the NIWA research ship, Tangaroa, on the Chatham Rise to collect data, in the form of photographs, of fish.

“This data will contribute to building an ecosystem model, which will allow us to test different scenarios on the Chatham Rise. We can look at how the abundances of different fishes change with increasing sea temperatures or fishing pressure.”

Monique is now working with a team of five volunteers to analyse 850 photos of fish that were captured on the boat. “We are using an image analysis program to collect 14 measurements of each fish. The gape information will be used to inform the model of how large prey can be for a given predator.”

Learning about how fish adapt gives researchers insight into why a fish is—or isn’t—successful in a given environment. “We looked at how gape and body size vary with trophic level. Generally, this relationship produces a positive correlation, where fish with bigger mouths eat at higher trophic levels. But, in the case of deep sea fish, we found no correlation.”

This research found that fish that live in the deep sea have evolved to have the largest mouth possible. “This helps the fish to eat in an environment where food may not be abundant. They’ve adapted to the deep sea by becoming generalists—eating everything that is available.

“Fish that have a highly adaptive, or generalised, diet might be more successful. If all deep-sea fishes are relatively adaptive, this could make deep-sea fishes robust and resilient to ecosystem changes and the effects of fishing.”

Monique is employed by the National Science Challenge: Sustainable Seas and collaborates with researchers from Victoria, NIWA and the Scottish Association for Marine Sciences.