Experts reveal the nutritional quality of fish and squid caught in New Zealand could be declining

13-Jun-2018 - Last updated on 13-Jun-2018 at 02:17 GMT

Fish and squid captured by gannets were found to have significantly lower ratio of healthy oils to protein during warm water events. ©iStock

New research has uncovered that the nutritional balance of fish and squid changes and is of lower quality under warm water events, while under cold water events it is of higher quality.

Conducted in New Zealand, the research used a highly successful marine predator seabird –the Australasian gannet – as a biological monitor of the marine environment and food sources.

The team combined miniature bird-borne GPS loggers, fish and squid nutritional analysis and nutritional modelling, and quantified colder and warmer water events by comparing the mean sea surface temperature with 10 years of data.

Fish and squid captured by gannets were found to have significantly lower ratio of healthy oils to protein during warm water events (where sea surface temperature was warmer than the 10-year mean) and better nutritional quality during cold water periods (lower than the 10-year mean).

Published in the Journal of Animal Ecology, the research was a collaboration between the Charles Perkins Centre, School of Life and Environment Sciences and School of Mathematics and Statistics at the University of Sydney; James Cook University in Queensland; Massey University in New Zealand; and the Ornithological Society of New Zealand. It forms part of the human-animal interactions and Human Food Chain project nodes at the Charles Perkins Centre.

Nutritional landscape

Lead author Dr Gabriel Machovsky-Capuska, adjunct senior researcher at the University of Sydney, said the findings had implications for marine life and its predators, including humans.

Co-author Professor David Raubenheimer, said: “Our approach, which we call nutritional landscapes, allows us to associate the nutritional quality of marine resources – otherwise very challenging, as marine life continuously moves – with geographic location, water depth and environmental conditions such as sea surface temperature and chlorophyll levels.”

“These findings underline the importance of linking marine environmental fluctuations with the nutritional quality of fish and squid for human consumption – and provide significant insights for fisheries that are capturing fish for humans to eat.”

Dr Machovsky-Capuska said the findings were also revealing for environmental and conservation purposes.

“The work shows that diet and foraging behaviour of marine predators are significantly influenced by warm and cold events,” he said.