Under the sea, it really is survival of the fittest.
A new study has found that the reef fish humans find ‘ugly’ are more likely to be endangered than their more beautiful cousins.
Researchers from the University of Montpellier, France, used machine-learning to rank thousands of different fish species on their attractiveness to humans.
They then compared that ranking to the species’ placement on the International Union for Conservation of Nature (IUCN) Red List, which evaluates their conservation status.
It was discovered that fish species listed as ‘Threatened’ tended to be seen as less beautiful than those categorised as ‘Least Concern’.
The plainer fish were also more likely to be fished, and thus had greater commercial importance.
The scientists concluded that conservation of the less attractive species should be made a higher priority.
The Holacanthus ciliaris, also known as the queen angelfish, was ranked highly in attractiveness due to its bright colours and rounder silhouette
The Diplodus annularis, or annular sea bream, was rated as one of the least beautiful reef fish. It is a very important catch for artisanal fishermen and can often be found in local fish markets
Graphs showing the negative correlation between the aesthetic value and (left) the age of the species, and (right) the functional distinctiveness of species. The plain line represents results that did not account for phylogenetic relatedness, and the dashed line did
Senior research scientist Nicolas Mouquet said: ‘Our study provides, for the first time, the aesthetic value of 2,417 reef fish species.
‘We found that less beautiful fishes are the most ecologically and evolutionary distinct species and those recognised as threatened.
‘Our study highlights likely important mismatches between potential public support for conservation and the species most in need of this support.’
The team asked 13,000 members of the public to rate the aesthetic beauty of 481 photographs they found online of ray-finned reef fishes in a survey in 2019.
They removed the background of each photo and made sure all fish were facing the same direction, and the camera had a similar viewpoint.
The data collected from the survey was then used to train a ‘convolutional neural network’ – an artificial intelligence tool that can process images.
The neural network was able to predict human bias of an additional 4,400 photographs featuring 2,417 of the most encountered reef fish species.
After combining the public’s ratings with the neural network’s predictions, the researchers discovered that bright, colourful fish species with rounder bodies tended to be rated as the most beautiful.
The scientists found that species listed as ‘Threatened’ by the IUCN, or whose conservation status has not yet been evaluated had lower aesthetic value on average than species categorised as ‘Least Concern’.
Examples of fishes representative of the range of predicted aesthetic values, decreasing in aesthetic value from left to right and top to bottom: Holacanthus ciliaris, Aracana aurita, Amphiprion ephippium, Ctenochaetus marginatus, Scarus spinus, Amphiprion bicinctus, Epinephelides armatus, Fusigobius signipinnis, Diplodus annularis, Odontoscion dentex, Nemadactylus bergi, Mendosoma lineatum
The striped cowfish (left) and mandarinfish (right) are among the reef fish species with the highest aesthetic values, according to a survey and machine-learning algorithm
Furthermore, the species that were ranked as less attractive were found to be more distinctive in terms of their ecological traits, like habitat type and body size.
They were also more phylogenetically isolated, so they had a more distinctive evolutionary history.
This means that they contribute more to the biodiversity of a coral reef and play a greater role in its functioning.
The loss of their contribution to the gene pool could have larger consequences on the ecosystem than that of a more aesthetically pleasing fish.
The researchers also compared species’ aesthetic value with their importance to fisheries.
Unattractive species also tended to be of greater commercial interest, as aesthetic value did not correlate to those of most value to small-scale, traditional fisheries.
The preferences humans have for shape and colours are likely a consequence of the way the brain processes them, the authors concluded.
However the mismatches between aesthetic value, ecological function, and extinction vulnerability may mean that the species most in need of public support are the least likely to receive it.
The results of the study were published today in the open-access journal PLOS Biology.
Fish on Australia’s Great Barrier Reef are losing their COLOUR as coral reefs decline, study finds
Fish on Australia’s Great Barrier Reef are losing their colour as coral reefs degrade and die during bleaching events, a new study shows
Researchers from James Cook University in Townsville in Queensland, Australia have found a link between dull-coloured fish and corals that have undergone coral bleaching and turned white.
In particular, the abundance of yellow and green fish has dropped steadily by about three quarters over the past 27 years, they found.
Currently, experts don’t know the exact reason for the link between dull coloured fish and bleached coral, or if one causes the other
Fish that inhabit coral reefs are extremely diverse in colour, although the specific environmental factors that lead to this remain unclear
James Cook University researchers have found brightly coloured fish are becoming increasingly rare as coral declines, with the phenomenon likely to get worse in the future. Pictured is the lemon damselfish (Pomacentrus moluccensis), one of the species looked at for the study
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