Could we use fish guts to monitor the health of the oceans?
The stomach contents and gut microbiome of tuna could be a viable near real-time monitoring tool for changes in oceanic ecosystems.
The gut contents of skipjack and yellowfin tuna can provide important feedback on the effects that the El Niño-Southern Oscillation (ENSO) cycle has on oceanic ecosystems, says a study led by the University of Canberra.
“By applying molecular techniques to the stomach contents and gut microbiome of tuna, we were able to detect ecological changes such as the diversity of prey in different areas and at different ENSO phases,” says lead researcher Dr Alejandro Trujillo-González. ENSO cycle events have far-reaching impacts on weather systems, wildfires and floods, ecosystems and economies – and the study indicates that they are far more diverse than previously recognised.
Instead of capturing animals anew for the study, the researchers accessed the Pacific Marine Specimen Bank and analysed the stomach samples of tuna captured between 2015 and 2017.
These were then analysed using the metabarcoding technique, which allows the genomic sequencing of a whole range of fauna at the same time, returning a result in under 24 hours. The number of consumed individual creatures was huge: from 96 collected stomach samples, the method identified 14,053,270 bacteria, 37,668,878 actinopterygians (ray-finned fishes), 12,903,281 crustaceans and 7,942,872 cephalopods.
One of the findings of the study was that fish captured during La Nina events had a higher diversity of prey in their stomach contents.
“This suggests that the nutrientpoor conditions during El Nino caused less prey to be available, and therefore resulted in less productive habitats,” Dr Trujillo-González says.
The team is now looking at how portable technologies could provide near real-time results for ocean-based field researchers.