Most of these new species occur now in underexplored tropical areas, in very deep waters, in hidden habitats or in fish families with diversity higher than previously suspected.
In the last two decades, molecular biology and what we call "DNA barcoding" has greatly improved our ability to distinguish species limits and has enabled a better description of the diversity of living species. It easily permits making the link between various forms of the same species. As examples for barcoding, eggs, larvae, and adults, sexual dimorphisms between male and female, or variation of colour patterns are more effectively determined.
Representation of fish species in atlases, in addition to diagnostic keys and written descriptions, is a great assistance for fish determination. It helps biologists during marine inventories and fishery surveys, but it is also useful for the public interested in our marine environment. As a biologist, partly working on fish diversity and classification in European waters, I am particularly aware about obtaining the best images as possible of the fishes that contribute to the marine biodiversity or simply as part of the ecosystem. Special attention is given to rare species, living in habitats that are difficult to access and for which there is often not a single photograph available.
Weak and damaged
Most fin-fishes are particularly weak and damaged by trawls and other gears during capture. In addition, they cannot be maintained in a fresh natural state for a long time. Consequently, attempts to obtain good images of fishes in their natural state is a real challenge. Photography of offshore or deep-water fishes in their “natural state” requires the photographer to be present onboard vessels collecting these fishes. Time is often counted in minutes to obtain the best photos of a fish because within a few minutes the colour and shape of some species will be degraded. To obtain high quality images, a good camera and favourable light and sea condition are required. Most fish species have scales that reflect light and results in photos of poor quality. This can be avoided by placing the specimen into water. On a moving boat, manipulation of fishes inside aquariums and the large amount of photographic equipment required are big challenges.
Survey in the North
The research vessel Helmer Hanssen, from the UiT The Arctic University of Norway, is currently operating in the waters north of Svalbard for SI_ARCTIC and IMR-PINRO program to conduct baseline and process studies of the Arctic Ocean ecosystem and to conduct the Barents Sea Ecosystem survey respectively. After a week onboard the vessel, dozens of typical arctic fish species have been collected, photographed, preserved as vouchers for museum collections, and sampled for genetic analyses (Figs 1 to 6). The unique shape and colours of these species could also be appreciated for their particularly artistic appearance.
The fishes preserved as vouchers for institutional fish collections and photos of them will be used to complete the Atlas, "Handbook of the marine fishes of Europe and adjacent waters (A natural classification based on collection specimens, with DNA barcodes, and standardized photographs)". This project that I started eighteen years ago now includes about 850 species representing about 60% of the fish diversity of the area from the North Pole to the equator and from the mid-Atlantic to the Black Sea. As this Atlas is a long-term project, provisional versions of it are regularly uploaded to the internet and available for everyone here and here.