A Review of Fish Taxonomy Conventions and Species Identification Techniques

Journal of Survey in Fisheries Sciences 4(1) 54-93 2017 A Review of Fish Taxonomy Conventions and Species Identification Techniques Keat-Chuan Ng C.1; Aun-Chuan Ooi P.1; Wong W.L.1; Khoo G.1* Received: December 2016 Accepted: March 2017 Abstract Taxonomists, ecologists, geneticists or researchers from other biological fields who wish to adopt fish as a constituent of their studies often become discouraged when they find that ichthyology is a complex subject. In fish-based studies, the failure to recognize fishes as distinct biological units can lead to wrong diagnosis. Hence, this review paper attempts to clarify and discuss the latest schools of thought pertaining to fish taxonomy and the techniques for species identification. It is hoped that the contents and illustrations in this paper will assist researchers in laying a good foundation to inform their studies. Keywords: Fish, Morphology, Molecular, Taxonomy, Species identification 1-Faculty of Science, Universiti Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, 31900 Kampar, Perak, Malaysia. *Corresponding author's Email: [email protected] 55 Keat-Chuan Ng et al., A Review of Fish Taxonomy Conventions and Species Identification … Introduction interbreed in natural conditions. In the The term “fish” is usually a convenient “evolutionary species” concept, a species description for a group of poikilothermic is a representative of a lineage having its (cold-blooded) aquatic vertebrates under own evolutionary affinity and historical the Chordata phylum that breathe with destiny. As for the “phylogenetic species” gills (Nelson, 2006). Scientifically, the concept, species is viewed as a collective term of “fish” primarily refers monophyletic set of organism with to Agnatha (jawless fishes), common ancestors. In practice, each of Chondrichthyes (sharks and rays), these major concepts is prone to some Sarcopterygii (lobe-finned fishes), and level of subjectivity. Regardless of Actinopterygii (ray-finned fishes). concept, wildlife scientists, especially Actinopterygians, the bony or ray-finned ichthyologists, typically identify and fishes, are without a doubt the majority of name fishes by either by their consistency fishes found in freshwaters. in morphological, and more recently, Actinopterygians have lepidotrichia which molecular characteristics. are characterized by fins of membranous While most researchers are concerned webs held together by bony spines, or with fishes as a food source and their rays. This niche character differentiates work involves enriching the body of Actinopterygians from Sarcopterygians aquaculture knowledge, there are some which possess lepidotrichia that are who are interested in their diversity, fleshy. distribution patterns, ecology and Although in early 20th century, the functional physiology. Recently, there has ichthyologist Regan (1910) defined a fish also been an overwhelming interest in the species as a product of interrelated molecular constitution of fishes (Wong et communities with common morphological al., 2011; Pereira et al., 2013; Rakshit et features (today this is termed as al., 2015 Quraishia et al., 2015) and their “morphospecies”), it should be noted that function as biological indicators to the species classification concept differs monitor waterbody pollution (Fonge et among scientists. While authorities such al., 2011; Khodadoust et al., 2013; as Nelson (2006) and Mayr (1942) accept Authman et al., 2015). Correspondingly, the “biological species” concept, others the interest in fish has expanded like Simpson (1951) promotes the exponentially, and the ichthyology “evolutionary species” concept. Then discipline is often sought to contribute too there is Cracraft (1983) who prefers to many other fields of studies (Padilla and adopt the “phylogenetic” or “cladistic” Williams, 2004; Lauder et al., 2007; Feist species concept. and Longshaw, 2008; Rudkowska et al., The oldest and most widely practised 2010). Generally, species is the basic unit “biological species” concept postulates in these studies and sound taxonomy is a that species are part of a group prerequisite to prevent confusion and composition that breed or can potentially misinterpretation. Journal of Survey in Fisheries Sciences 4(1) 2017 56 However, researchers who wish to rules, and yet set out to conduct fish- adopt fish as a major or minor component based studies and publish papers. Since of their studies will be discouraged when they lack field experiences, many are they discover that ichthyology is not an unaware of distinctive fish characteristics easy subject, more so fish taxonomy. such as phenotypic polymorphisms, Also, it is a common knowledge that there sexual dimorphism and behavioural is already an acute shortage of fish divergence due to the regional speciation taxonomists and finding a fish taxonomist process (Waugh, 2007). Failing to to assist in a study is often difficult. Such recognize such exceptions can lead to is the same case with many other taxa. wrong species diagnosis. Some Since fish diversity can be high, researchers restrict themselves to especially in tropical countries, a laboratories, ornamental fish and taxonomist is typically overwhelmed with aquaculture farms, and their specimens constant scientific name revisions, field may look very different from the wild collection expeditions and managing a type which the scientific name was museum. Moreover, taxonomy cannot be derived from. Ideally, it is advisable to commercialized and it sees very little treat a selective bred variety raised in funding in many countries. Thus, the artificial conditions differently. discipline rarely attracts students or can Otherwise, publication with nomenclature sustain career taxonomists in the errors will be perpetuated through citation universities. Such a problem has caused and cause a chaotic situation. taxonomic errors in published papers and In lieu of concerns highlighted, this the condition is now widely known as the review attempts to provide a concise “taxonomy impediment” (Wheeler et al., introduction to this complex but important 2004; de Carvalho et al., 2007). It is often field. To understand fish as a biological said that the discipline of taxonomy unit, the readers should also have some would be extinct earlier than most background in zoology. Our objective is endangered species. not to polarize techniques for fish On hindsight, the advancement of identification because we are convinced molecular, computerized and statistical that each technique has its merits. Their techniques have led many to believe that shortcomings will, however, be discussed “species” can be easily characterized by to assist researchers in making sound nucleotide sequences, software and judgments and decisions. mathematical calculations, and the This paper reviews and discusses knowledge in taxonomy is no longer taxonomic concerns of freshwater species needed. Ebach and Holdrege (2005) warn that belong to the Actinopterygii class, us that there are a growing number of and we assume that readers have some researchers who have never wet their feet familiarity with ray-finned fish anatomy in the rivers to observe species or build and the common species. Given that a competency in applying nomenclature picture is worth a thousand words, we 57 Keat-Chuan Ng et al., A Review of Fish Taxonomy Conventions and Species Identification … believe that taxonomy can be easier to clustering species that looked similar master if the reader is provided with because they believed that these species detailed scientific illustrations and colour share a common biological lineage. In the images. This review is by no means mid-18th century, the evolution hypothesis comprehensive but we hope it will set a was a new and strange concept. good foundation for those who wish to Eventually this was proven to be factual make a competent start in species-level in the advent of modern molecular and research. genetic assessment technologies. In general, today, there is a consensus Why are there do many species? among scientists that all species on Earth Teleost species form the largest category are interlinked with a hierarchical and among vertebrate animals and their evolutionary tree with millions of numbers have reached more than 32,500 branches. Each branch itself is a valid marine and freshwater species under representation of the natural history of a 515 families (Nelson, 2006). In the global particular species and its pedigree. But context, there are roughly 11,952 of why did the branches have to extend and freshwater species (Helfman et al., 2009). multiply in the first place? What causes Ricklefs (2004) suggests that competition the divergence? and mutualism among species have an When gene flow among populations is effect on species abundance while Wright interrupted by natural (e.g., geographic et al. (2003) speculate that species barriers created by earthquakes) or diversity is the result of productivity from artificial means (e.g., man-made barriers available “energy” in a particular region. in aquaculture farms and dams), two types If a region lacks energy (e.g., low food of speciation will occur, namely allopatric availability in the desert), species richness speciation and sympatric speciation is typically low. However, in the case of (Butlin et al., 2016) (Fig. 2). Allopatric fish, MacArthur’s (1969) hypothesis speciation occurs when a population is seems to be the most probable as he separated by a barrier and such isolation suggests that species diversity is prevents the two

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