Abstract
Clarias macrocephalus Günther, 1864 is a Near Threatened freshwater catfish found in the Philippines and other Southeast Asian countries. Its numbers have dwindled over the past few years because of habitat loss and competition. This study examined the genetic diversity of the remaining viable populations of C. macrocephalus in the Philippines. Primers were designed to amplify via polymerase chain reaction (PCR) the complete mitochondrial DNA (mtDNA) control region (870-bp) in 120 specimens collected from three sites: (1) Buguey, Cagayan; (2) Camalaniugan, Cagayan; and (3) Agusan del Sur. Of the 120 sequences generated, only three haplotypes and two polymorphic sites were found. Overall haplotype and nucleotide diversity (h=0.479, π=0.00058) were alarmingly low, consistent with populations of other freshwater fishes that have experienced a genetic bottleneck. The overall FST value was 0.80050, indicative of large genetic differentiation between populations. The very low genetic variation found in all three C. macrocephalus populations calls for conservation and management efforts for the protection of the remaining populations of this economically important species.
Highlights
Clarias macrocephalus Günther, 1864, commonly known as Bighead Catfish, is a freshwater catfish native to Thailand, Laos, Cambodia and Vietnam
The species was reported in Laguna de Bay (Conlu 1986), Lake Taal (Mercene 1997), Lake Manguao, Palawan (Matillano 2003), Cuyapo, Nueva Ecija (Froese & Pauly 2016), Lake Lanao in Mindanao (Rosagaron 2001), Bicol Region (Southeast Asian Fisheries Development Center 1999), Aurora (Tayamen 2007), and island provinces in Visayas and Mindanao (Tayamen 2007)
Assuming misidentification by Juliano et al (1989), there is a possibility that the catfish introduced from Thailand in 1972 was C. macrocephalus and not C. batrachus
Summary
Clarias macrocephalus Günther, 1864, commonly known as Bighead Catfish, is a freshwater catfish native to Thailand, Laos, Cambodia and Vietnam. Roxas & Martin (1937), Fowler (1941), and Herre (1953) listed C. macrocephalus in their checklist of Philippine fishes and all of them cited Meyer (1885) as reference who reported the presence of the species in Laguna de Bay, the largest lake in the Philippines. Assuming misidentification by Meyer (1885), reports of the presence of C. macrocephalus in the Philippines since 1972 (Conlu 1986; Mercene 1997; Southeast Asian Fisheries Development Center 1999; Rosagaron 2001; Matillano 2003; Tayamen 2007; Quilang & Yu 2015; Santos et al 2015; Froese & Pauly 2016) could be due to this introduction. The presence of C. macrocephalus in the Philippines was established definitively by these studies
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