A group of Australian scientists has created the world’s first computer model that can accurately predict the movements of baby coral trout across the Great Barrier Reef.
The computer model confirms the importance of no-take zones to ensuring healthy fish populations within fishing zones.
Tracking the lives of thousands of tiny baby fish is no easy task. But knowing where they’ll settle and spend their lives as adults is invaluable data for the fishing industry and reef managers.
The model is detailed in a recent study that tests and validates the computer predictions with field data. This is a world-first achievement, combining the movement of ocean currents in and around the Great Barrier Reef with the genetic and behavioural data of fish.
“The behaviour of fish in their first few weeks after hatching can really influence where they eventually settle,” Dr Michael Bode said. He led the study while he was at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University (JCU).
“The model is a unique conservation collaboration between marine biologists, geneticists, and recreational fishers.”
“This was a major field effort combined with some clever molecular work that involved matching baby fish to their parents to understand their movement,” co-author Dr Hugo Harrison, also from Coral CoE at JCU, said.
The study focussed on coral trout, Plectropomus maculatus, which is one of the most valuable species of fish regularly caught on the Great Barrier Reef.
To validate the computer model, 1,190 juvenile and 880 adult fish were tracked—from spawning locations to settlement—across the reef for two years. There were 69 parent–offspring relationships within the group, connecting 18 different patch reefs that were separated by distances ranging from a few hundred metres to more than 200 km.
The computer model recreates the movements of baby fish across space and time by considering what depth the coral trout swim at, how fast they swim, and how they orient themselves as they grow older.
The predictions also highlighted the interconnectedness of reefs, and how important no-take zones are to ensure future adult fish populations within fishing zones.
“Our model proves that the Great Barrier Reef’s no-take zones are connected with invisible threads,” Dr Bode said.
“Knowing how reefs are connected to one another means fishers and managers alike can identify which areas are likely to be most productive and need protecting,” Dr Harrison said.
“It’s the babies from these protected areas that will continue to restock fish populations on neighbouring reefs where fishing is allowed.”
Dr Bode said establishing the credibility of these models is a matter of urgency.
“Their predictions are not only a decision-making tool for planning and policy but are the foundation of important new theories in marine ecology and evolution,” he said.
“Our match between models and data provides reassuring support for existing applications, but also directions for future improvement.”
Bode M, Leis J, Mason L, Williamson D, Harrison H, Choukroun S, Jones G (2019). PLOS Biology. ‘Successful validation of a larval dispersal model using genetic parentage data’. DOI: https://doi.org/10.1371/journal.pbio.3000380
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