Of the trade figures for the EU evaluated between 2014 and 2017, over a third of the fish species were also not assessed by the IUCN Red List.  Therefore, it is inestimable which impact these removals have on the fish population and coral reefs. In 2018, almost 45 percent of all known coral reef fish species remained unassessed by the IUCN Red List due to a lack of biological and ecological knowledge. The Red List is responsible for the conservation status of animals and plants but has not the authority to grant any protection.
Damselfishes (Pomacentridae) and wrasses (Labridae) seem to be the most traded fishes. They account for almost half of the trade figures. Other species often traded are angelfishes (Pomacanthidae), surgeonfishes (Acanthuridae), gobies (Gobiidae) and butterflyfishes (Chaetodontidae). 
ENDEMIC SPECIES – SMALL DISTRIBUTION AND SMALL POPULATIONS
Example: Banggai cardinalfish (Pterapogon kauderni)
P. kauderni lives in small populations, shallow waters in coral reefs and sea grass beds commonly in sea urchins, coral heads, and anemones. It has an extremely limited distribution area and is endemic to only 23 square kilometres in an archipelago off the coast of Eastern Central Sulawesi, Indonesia. Within this area, the species range is restricted to 34 out of the 67 islands that form the Archipelago, 21 of them being less than 6 kilometres in length. 
Its unusual biological traits such as obligate commensalism with its hosts, sex-role reversal, and long incubation period with advanced parental care where the male incubates 50-60 eggs and post-hatched embryos orally, with very low fecundity and absence of larval phase. This resulted in a very strong population structure and unique genetic signatures.
This remarkable fish has become emblematic of the exploitation of marine ornamentals for the international aquarium trade and the difficulties of associated conservation efforts.
P. kauderni was only discovered in 1994 and was included as ‘endangered’ in the IUCN Red List in 2007, because over 90 percent of its population size had been fished out for the aquarium trade. Although these fishes can be successfully farmed, wild capture is cheaper
We collaborated in a study to assess the impact of international trade Banggai cardinalfish.
Unfortunately, two attempts to include this species in the appendices of CITES (Convention on International Trade in Endangered Species failed due to political issues – see Protection. One proposition to include the species in Appendix II to regulate and monitor its trade had been submitted by the United States of America in 2007 and one by the European Union in 2016 which asked the same. Both were withdrawn.
Example: Common cleaner wrasse (Labroides dimidiatus)
L. dimidiatus keep other coral reef fishes, sharks and rays free from parasites. They play a key role for reef diversity. Studies have shown that in a coral reef where all cleaner wrasses have been removed, other coral fishes disappear as well after only four months the biodiversity is reduced. 
L. dimidiatus are very difficult to keep and only survive in a species-rich aquarium, so that even the aquarium specialists advise against keeping them.
Example: Blue tang or blue surgeonfish (Paracanthurus hepatus)
In 2016, the P. hepatus became famous as the character ‘Dory’ in the Walt Disney film ‘Finding Nemo’. Due to its fame, it is now a popular aquarium fish. It can grow up to 40 centimetres, which is a problem for conventional aquariums. In addition, the blue tang behaves aggressively towards other coral fishes. Although breeding has been successful, animals are still taken from the wild since the demand is so great. If such a fish is advertised as ‘farmed’, it has most likely been caught wild as a juvenile and then raised to the desired size in an aquarium and not bred in captivity over several generations.
Example: Parrotfishes (Cetoscarus bicolor)
Juvenile fishes are often caught due to their special colour or small size as they either are more economic for transport or are more attractive. Hence threatening sustainability of removal. In addition, the age structure of the reef species is altered. If too many juveniles are continuously caught, the adult population suffers, as only a limited number of juveniles reach adulthood to replenish the overall population.
Example: Mandarin fishes (Synchiropus splendidus)
Some populations of S. splendidus are already considered extinct in the wild. Due to their special colouration, they are very often traded. Since primarily the male S. spendidus are targeted for aquariums, this has resulted in a change of their population biology. Studies have shown that males in the wild now measure only 3 centimetres instead of 6 centimetres, which is the prime breeding size. 
S. splendidus are usually fished with a hand spear. This can cause serious injuries or even death to the animals.
Example: Blue-green damselfishes (Chromis virdis)
C. viridis is the world’s most traded coral fish. The US alone imports almost one million individuals per year.  Catching and transport methods cause great losses. In the main exporting countries, Indonesia, and the Philippines, they are often still caught illegally with poison. Many blue-green damselfishes die, as do many other animals and often the fishermen are poisoned themselves.
In our own scientific study on the trade of marine ornamental fishes into the EU, we classified all traded species according to four parameters: The number of specimens traded over four years, the trend in trade volume (increase), the conservation status according to the IUCN Red List and the vulnerability according to FishBase (www.fishesbase.org). Caution is warranted as all species ‘not evaluated’ or ‘data deficient’ in the IUCN Red List were not uses for this evaluation.
According to our study, 17 species were placed on a so-called ‘watchlist’, meaning these species are possibly endangered by international trade and should be monitored by CITES.
Contrary to freshwater ornamental fishes, where the majority is captive bred, of the more than 2,300 coral fish species in trade, only about 25 can be bred in captivity in commercial numbers. For about 340 species, breeding success is still in the research stage.
According to the United Nations, it is difficult to breed coral fishes because the fishes larvae need a special diet and nutritional supplements that are not easy to replicate naturally. Older fishes larvae need different food as they mature, therefore harvesting them from the wild is much cheaper than breeding them.
One example of a species group which can easily be bred:
After the Disney film ‘Finding Nemo’ hit the cinemas, the demand for anemonefishes skyrocketed. As a result, an enormous number of anemonefishes were caught in eastern Australia to the point that certain stocks have not yet recovered.
Primarily anemonefishes and seahorses are bred; however, breeding anemonefishes cannot meet the demand, meaning most anemonefishes in trade are still harvested from the coral reef. Anemonefishes live in a symbiosis with anemones; if the fish is removed, the anemones, and the overall coral reef, suffers as well.