Characterizing fish communities must be a priority to safeguard resources and determine critical changes.

This study analyzed species richness and the spatial and temporal evolution in the structure of fish assemblages based on photos taken in underwater free-diving contests. A total of 29 contests held from 2008 to 2015 at four different locations along the northeastern Spanish coast, including a marine protected area (MPA, Medes Islands) were analyzed. It must be considered that those contests reward the number of species per participant and photographic quality.

The results show a total of 88 taxa recorded in the contests’ photographs, including 32 cryptobenthic species, which is, as the authors state, the highest number recorded in the Mediterranean littoral system so far.

The study highlights that catch image rates in the MPA were significantly higher for seven species of high commercial interest and for two of recreational interest, including an endangered species.

The authors conclude that, despite the potential weaknesses of photographic free-diving contest data, the obtained results show their effectiveness for evaluating species richness, in particular of cryptobenthic species, and for analyzing total fish communities. And highlight that the monitoring of photographic free-diving contests could be a complementary information source to scientific monitoring.

The authors underline additional positive aspects of this information source, being cost-effective, non-destructive, a potential observatory, a platform for interaction between scientists and free divers, and an alternative for spear fishers in MPAs.

Gordoa A, Boada J, García-Rubies A, Sagué O (2018)  Free-diving underwater fish photography contests: a complementary tool for assessing littoral fish communities. Scientia Marina 82:95-106.