With so many species under threat due to human activity and climate change it's encouraging to hear about one population that's doing well for itself.
The estimated population size of the community of manta rays is more than 10 times the number thought to be in other regions.
Commercial fishing is the largest threat to the species, whether that's through direct targeting or unintentionally.
Joshua Stewart is a quantitative ecologist from Oregon State University. It's a rare story of ocean optimism. This species is very vulnerable due to the fact that we have population estimates of 1,000 to 2,000 animals.
It's not easy to study and monitor these animals, they spend a lot of time in hard to access offshore locations, and their movements can be unpredictable.
Scientists have been keeping a close eye on this group of manta rays. Researchers used more than a decade's worth of photos and observations to estimate a current population of over 22,000.
This area is a hot spot for these fish. The team thinks that a plentiful supply of food could be one of the reasons the population has grown, with cold, nutrient-rich water rising up from the depths and delivered on ocean currents providing a steady stream of zooplankton snacks
Stewart says that it is a cautionary tale. Changes in ocean temperatures and food availability seem to be sensitive to environmental disruptions.
If upwelling strength and the abundance of food changes alongside ocean temperatures, they will likely be impacted.
Scientists get a better idea of population levels around the world from long-term surveys. It's important that outliers such as this group of M. birostris are included in estimates of abundance and average.
The more precise the data is, the more targeted it can be. The capture of manta rays in this part of the world is now illegal, but other issues such as bycatch, fishing net entanglement and strikes from vessels remain a problem.
The study was a success for citizen science. More than 2,800 fish could be individually identified in more than 3,300 images, one of the main reasons that the population could be assessed.
The spots on the manta rays' bellies are similar to human fingerprints or the white spots on whale sharks. Researchers can track and count the rays over time. They can estimate population size based on re-sightings.
Many of the photos used in our study were contributed by recreational divers who became citizen scientists when they snapped photos of manta rays.
The photographs give us a lot of information about the animals.
The research was published in the marine ecology progress series
All Rights Reserved © 2024
