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Species

Labrids

 

Labrids 

Labridae (wrasses) belong to the Order Perciformes, the richest in species within the teleosts. The Labridae family is in turn one of the most diverse within the order, represented by at least 80 genera and over 600 species, all very different in their shape, colour and size. All wrasses are marine and live in the Atlantic, Pacific and Indian Oceans and the Mediterranean Sea, usually near the substrate or buried in the sand in shallow waters, at sites such as coral reefs and rocky coasts. With a few exceptions, they are small, usually less than 15 cm long. They have a protractile mouth with thick lips and a fast protrusion mechanism, cycloid scales, a continuous or uninterrupted lateral line and a long dorsal fin with spines at the anterior part running along most of the back. Many species are brightly coloured, and even within a single species, there may be different colouring patterns, including sexual dichromatism. They have different mating systems and many species are protogynous hermaphrodites. The males of some species are territorial. Wrasses are efficient carnivores and feed on a wide range of small benthonic invertebrates, although some species are planktivorous. Many species follow the feeding routes of larger fish, capturing invertebrates disturbed along the way. Other species establish cleaning symbioses and act as “cleaner fish”, feeding on the ectoparasites of another fish, which benefits from having them removed. Cleaner wrasses are being used in the biological control as a support or alternative to the use of chemotherapy for ectoparasites. Since the mid-1980s, they have been used in marine co-culture with Atlantic salmon (Salmo salar) and rainbow trout (Onchorhynchus mykiss) against “sea lice” Lepeophtheirus salmonis and Caligus elongatus. The most commonly used Labridae species are Centrolabrus exoletus (rock cook wrasse), Labrus mixtus (cuckoo wrasse), Ctenolabrus rupestris (goldsinny wrasse), Labrus bergylta (ballan wrasse) and Symphodus melops (corkwing wrasse), with the latter two being the most important, either due their biomass or number. The alarming rise in resistance acquired by ectoparasites to chemical biocides has increased enormously the demand for cleaner fish, leading to the capture of large numbers from their natural environment and transportation over great distances. However, their susceptibility to viral, bacterial and parasitic agents has been sufficiently documented, and highlights the clear sanitary risk involved in the use of wild specimens. Although many of the wrasses currently being used as cleaner fish are still wild, there are farms that raise them intensively, particularly goldsinny wrasse, ballan wrasse and corkwing wrasse. It has been proven experimentally that farmed Labrus bergylta is as efficient as wild specimens at delousing salmonids of sea lice and the use of farmed wrasse farming will  reduce the risk of introducing pathogenic agents. In general, there are few studies of the health status, ecology, life history and basic demography of these species or of their behaviour when farmed, so further studies are needed to learn about the sustainability of wrasse fisheries.