From Hagfishes to Halibuts, Thanks for All the Fishes. by Don Orth

More than one-half of the world’s living vertebrates are fishes.  With more than 69,000 vertebrate species, one must ask how we know that these facts are true (IUCN 2018).  Scientists around the world are continually adding to our knowledge and the names and numbers keep changing. It’s hard to check facts in news reports on the fishes. When I took Ichthyology as a student I learned that there were 18,818 species of fishes in the world. That's no longer true. The most up-to-date inventory indicates that there are 35,025 valid species of fishes in the world and 4,109 new species were added in the last ten years (Fricke et al. 2018).  That averages 411 species per year or more than 1 species per day!

In 1976, Joseph S. Nelson  published the first edition of Fishes of the World.  It was the definitive source of information on fish classification and a must-have reference for serious Ichthyologists.  New editions were published in 1984, 1994, 2006, and 2016.   The Catalog of Fishes maintained by the California Academy of Science  provides online information for all fish species and other web-based databases, such as FishBase  make ichthyological fact checking easier (Froese and Pauly 2018).  

Number of valid fish species, families, and orders recognized in Fishes of the World by publication year.  Data for 2019 from Catalog of Fishes.

Year	Species	Families	Orders
1976	18,818	450	46
1984	21,450	445	50
1994	24,618	482	57
2006	27,977	515	62
2018	32,000	536	85
2019	35,025	584	77

The most recent edition of Fishes of the World captures the explosion of published research on fishes and the emergency of 3D scanning, Next-Gen sequencing, molecular systematics, and large collaborative projects, such as the NSF All Catfish Species Inventory and Cypriniform, Euteleost, and Chondrichthyan Tree of Life projects.  From the most recent Catalog of Fishes, the three largest fish families are the Gobiidae, Cichlidae, and Cyprinidae.  Some familiar families of fish are monotypic, which means there is only one species.   Monotypic families include the familiar Whale Shark Rhincodontidae, Megamouth shark Megachasmidae, Bowfin Amiidae, Milkfish Chanidae, Salamanderfish Lepidogalaxiidae, Pirate Perch Aphredoderidae, Swordfish Xiphiidae, and Louvar Luvaridae. 

Top thirteen fish families (based on number of valid species) and number of species added in last ten years (Fricke et al. 2019)

Rank	Family Name	Common Name	Species	New Species
1	Gobiidae	Gobies	1,894	332
2	Cichlidae	Cichlids	1,720	189
3	Cyprinidae	Minnows and Carps	1,695	212
4	Characidae	Tetras	1,180	245
5	Loracariidae	Suckermouth Armored Catfishes	983	231
6	Nemacheilidae	Stone Loaches	724	192
7	Leuciscidae	True Minnows	674	75
8	Serranidae	Sea Basses and Groupers	570	53
9	Labridae	Wrasses	556	52
10	Cynolebiidae	Killifishes	457	128
11	Liparidae	Snailfishes	556	52
12	Pomacentridae	Damselfishes	416	33
13	Blenniidae	Blennies	404	11

The changes in numbers are due to discovery, lumping, splitting, and changes in classification.   The snailfishes Liparidae are deepwater fishes and pioneering video technology is responsible for discovery of many new snailfish species.   In other cases, reexamination of collected specimens may result in splitting species into several new species (e.g., Collins et al. 2017).  In other cases, the rarity of the species can explain how it was overlooked until recently.   In other cases, changes in numbers is due to a wholesale revision of the systematics (e.g., Cypriniformes Tan and Armbruster 2018).

 

Pseudolithoxus nicoi is an armored catfish endemic to Columbia and Venezula was recently split into two species (Collins et al. 2017.  Photo by PlanetCatfish.com

Among the new species discovered in 2018, are the Sailfin Fairy Wrasse and the Sunset Perchlet found during a survey of the deep reefs of Easter Island (Rowlett 2019).   

Sailfin Fairy Wrasse, AKA Blue Thorat Fairy Wrasse (Cirrhlabrus cyanogularis) Credit: Y.K. Tea / Tea et al. 2018

Sunset Perchlet Plectranthias ahiahiata, holotype, 39.95mm. Credit: Luiz Rocha / Shepherd et al. 2018

It’s not common for scientists to discover a new family of fishes.   However, in 2018 a new family was discovered from the Amazon (de Pinna et al. 2017).   This new species Tarumania was collected in isolated pools of tributaries of the Rio Negro where it is capable of burrowing in decomposing leaf litter and gulping air.  Why a new family?   There is no family in which to place this strange new fish with a curiously shaped swimbladder, eel shaped body, and scales on the head that face forward. 

 

Tarumania walkerae holotype. Credit: De Pinna et al. 2017

Novice and experienced Ichthyologists often struggle with the names of fishes because the precise meaning of many names is poorly known.  There is no definitive reference for the latinized names given.  The local endemic Bigmouth Chub Nocomis platyrhynchus was named from the Greek platurrhunkhos meaning “broad snouted” In the species description Lachner and Jenkins (1971, p. 39) wrote "the specific names, platyrhynchus, and the vernacular name, bigmouth chub, is in reference to the large gape width." The genus name Nocomis was given by Charles Frédéric Girard apparently because he liked the sound of the native American word, Nokomis which means grandmother.  Fish names are researched by The ETYFish project  and archived in the  Fish Name Etymology Database developed by Christopher Scharpf and Kenneth J. Lazara. In the North America, a group of fish taxonomist meet periodically and published the Common and Scientific Namesof Fishes form United States, Canada, and Mexico.   In the 2013 edition, they report on 3,875 species and 260 families.

Knowledge of fish numbers is essential for estimating extinction rates and providing a baseline for protection of rare and common fishes.  Fish taxonomy is an often overlooked specialty and the lack of support for taxonomy is a threat to biodiversity conservation.  For example, almost half of the nineteen species of popular black basses Micropterus spp., have been identified in the last twenty years (Taylor et al. 2019).  New fish species discoveries are a testament to the perseverance of dedicated taxonomists.  But the rate is slow and many cryptic fish species remain hidden or lumped with similar forms due to lack of analysis 

References

Collins, R.A.,  et al. 2017.  Biogeography and species delimitation of the rheophilic suckermouth catfish genus Pseudolithoxus (Siluriformes: Loricariidae), with the description of a new species from the Brazilian Amazon.  Systematics and Biodiversity 16:538-550. 

De Pinna, M.,  J. Zuanon, L. R. Py-Daniel, and P. Petry. 2018. A new family of neotropical freshwater fishes from deep fossorial Amazonian habitat, with a reappraisal of morphological characiform phylogeny (Teleostei: Ostariophysi). Zoological Journal of the Linnean Society, zlx028, https://doi.org/10.1093/zoolinnean/zlx028

Fricke, R., W.N. Eschmeyer, and R. van der Laan, editors.  2019. CATALOG OF FISHES:

GENERA, SPECIES, REFERENCES. (http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp). Electronic version accessed 9 January 2019.

Froese, R. and D. Pauly. Editors. 2018. FishBase. World Wide Web electronic publication.

www.fishbase.org, version (06/2018).

IUCN Red List of Threatened Species, Table 1: Numbers of threatened species by major groups of organisms (1996–2018) Source

Lachner, E.A., and R.E. Jenkins,. 1971.  Systematics, distribution, and evolution of the chub genus Nocomis Girard (Pisces, Cyprindae) of eastern United States, with descriptions of new species.  Smithsonian Contributions to Zoology, Number 85.   97 pp.  

Rowlett, J. 2019.  Top ten new fish species from 2018.  World Wide Web. https://reefs.com/2018/12/27/top-ten-new-fish-species-from-2018/   accessed 9 January.

Tan, M. and J. W. Armbruster.  2018. Phylogenetic classification of extant genera of fishes of the order Cypriniformes (Teleostei: Ostariophysi). Zootaxa 4476 (no. 1): 6-39.

Taylor, A.T., J.M. Long, M.D. Tringali, and B.L. Barthel. 2019.  Conservation of black bass diversity: An emerging management paradigm.  Fisheries  43