Global habitat loss of a highly migratory predator, the blue marlin (Makaira nigricans)

Aim Climate change is driving the redistribution of species throughout the oceans. However, the speed and magnitude of species responses, including shifts in their distribution, are variable and species specific. Quantifying the effect of environmental conditions on species distributions is crucial to informing management and conservation efforts. Blue marlin (Makaira nigricans) is a wide-ranging top predator occurring circumglobally in tropical and subtropical waters and is heavily impacted by international longline fisheries. This study aimed to predict the global distribution of blue marlin and characterize the effects of climate variability thereon. Location Global. Methods To conduct this study, pop-up satellite archival tags (n = 144) deployed by recreational anglers through a global citizen science programme were used to generate a large tracking data set (14,928 days, 210,983 km from deployment to pop-up locations) of blue marlin movement across three ocean basins. State-space modelled tracking position estimates were used to create a species distribution model to represent global habitat suitability for blue marlin. Habitat suitability was determined by fitting a generalized additive mixed model (GAMM) as a function of environmental covariates which was used to predict monthly global blue marlin habitat from 2000 to 2016. Results Blue marlin habitat preference had the strongest association with sea surface temperature. Seasonal variation in blue marlin habitat occurs primarily at the latitudinal edges of the distribution range. Over the duration of the study, 96% of core habitat declined in suitability, with a concurrent poleward increase in suitability of marginal habitat. Main Conclusions This study highlights the successful application of citizen-based science to develop a long-term global telemetry dataset. The present-day loss of highly suitable habitat suggests ocean warming may be making equatorial waters less suitable even to highly mobile species. Blue marlin is likely to respond by following preferred habitat as it shifts poleward.

Automated summary

This study predicts the global distribution of blue marlin and characterizes the effects of climate variability on their habitat. The research highlights the successful use of citizen-based science and shows that ocean warming is making equatorial waters less suitable for highly mobile species like blue marlin, leading to a poleward shift in their preferred habitat.