Marine coastal ecosystems provide a habitat for a wide variety of marine life. For us humans, these
areas play an extremely important role as fishing grounds. However, much of what ends up in our
nets has not been scientifically described yet – even some very popular species used as seafood. Still
less is known about the genetic diversity of these species. Information on the genomics and
distribution of different subpopulations of a species is extremely important in order to assess how
vulnerable individual species are to environmental change and fishery. For their study, Ricardo
Pereira and his team took a closer look at a species of octopus that has been fished for centuries but
was only described and recognized as a separate species in 2008: Octopus insularis.
The red-brown, predatory octopus lives in tropical reefs along the American East Coast and is
distributed from Florida to southern Brazil, as well as around some remote islands in the Atlantic
Ocean. While the adult octopods lead a sedentary lifestyle and do not travel far, the larvae are so
small that they passively travel longer distances as plankton, carried by ocean currents. Through the
planktonic larvae and with the help of ocean currents, this octopus managed to colonize even more
remote islands (this also earned it its name insularis).
Pereira's team found that the species Octopus insularis divides into at least six different populations
that rarely reproduce among each other. This is not a big problem for the large populations along the
mainland coast. The smaller island populations, on the other hand, have a much lower genetic
diversity and significantly higher rates of inbreeding. A population in which all animals are genetically
very similar is less able to cope with environmental changes. If population size is reduced, the
pressure of (over-) fishing becomes even stronger and can thus endanger the survival of the whole
population.
In order not to further reduce the genetic diversity and thus the resilience of the island populations,
Pereira and his team argue that those need a higher protection status and also propose so-called no-
take zones for some island groups, where fishing would be completely prohibited. This is crucial to
sustainably manage and conserve this ecologically and economically important octopus species.