https://phys.org/news/2018-06-scientists-link-ocean-dispersal-baby.html

"It's not like studying deer in a forest, where one need only count births and deaths to understand how population size changes, which is difficult enough," says senior author Mark Hixon, professor in the Department of Biology at the University of Hawai'i at Mānoa.

"The challenge of understanding changes in reef fish abundance in a metapopulation is to measure simultaneously egg production by adults on multiple reefs and the dispersal of baby fish among those reefs, as well as other factors," explains first author Darren Johnson, assistant professor in the Department of Biological Sciences at California State University, Long Beach.