Species persistence: a re-look at the freshwater fish fauna of Chennai, India

Chennai is amongst the few Indian cities that has had a long history of biodiversity studies. The erstwhile Madras that has since expanded considerably into today’s Chennai has extensive and diverse aquatic habitats that amongst others attracted the attention of ichthyologists for at least 100 years. Two perennial rivers Adyar and Cooum, numerous reservoirs that provide water for irrigation and drinking, seasonal tanks and extensive flood plains (example Pallikaranai Marsh), canals, channels, rice fields and open wells are typically freshwater habitats that add to the heterogeneity of the otherwise maritime landscape. One of the earliest and most comprehensive of fish studies that considered a wide range of Chennai’s aquatic habitats is that of Raj (1916). Raj’s study carried out around 1910 is in fact the bench mark of the series of fish surveys that spanned the 100 years dealt with in this paper. Raj (1916) recorded a total of 57 species of which 44 species may be treated as primary freshwater fishes (Menon 1999). He mainly surveyed the Adyar and Cooum rivers and sporadically the drinking water reservoirs of Sembarambakkam (Chembarampakkam) and Red Hills. Subsequent surveys of fish carried out by other authors focused mainly on the Adyar and Cooum rivers (Panikker & Aiyar 1937; Ganapati 1964; Evangeline 1967; Mary Bai 1993) with a few surveying the Chembarampakkam Lake (Raghunathan 1978; Daniels & Rajagopal 2004). The few other available publications are based on studies around Chennai and its environs (Devi et al. 1999) with a couple focusing on specific habitats (Raghunathan et al. 2005; Raghunathan et al. 2008). The present study focused mainly on the freshwater habitats around Chennai such as the Rettai Eri (near Red Hills), Madipakkam Lake, wetlands of Velacherry, Kovillampakkam Lake, Adyar River and the Chembarampakkam Lake. Dipnet, dragnet and castnet were used for the surveys and in deep waters where these methods could not be used, fishermen’s gill nets were regularly monitored. A dip net of 45 x 30 cm with mesh size less than 1mm, a cast net of radius 480cm with mesh size 10mm and a dragnet of dimensions 210 x 120 cm with mesh size less than 1mm were used, apart from regularly monitoring fishermen’s catches. Fishermen used four types of gill nets approximately 400 x 2 m each with different mesh sizes viz 25mm, 40mm, 55mm and 100mm. The species collected were identified using the available literature on freshwater fishes (Talwar & Jhingran 1991; Jayaram 1999). The identity of a few primary freshwater fish which were recorded in the previous surveys conducted over the past hundred years by various authors (Raj 1916; Panikker & Aiyar 1937; Ganapati 1964; Evangeline 1967; Raghunathan 1978; Bai 1993; Devi et al. 1999; Daniels & Rajagopal 2004; Raghunathan et al. 2005; Raghunathan et al. 2008) have since undergone nomenclatural changes/ revisions and the present paper is based on the current identity and geographical distribution of the species. Aplocheilus blockii is restricted to the west coast and very similar to A. parvus a species which is quite common in the Coromandel Coast (Menon 1999). Therefore in this paper the species present in Chennai and its environs is confirmed to be A. parvus which is frequently confused with A. blockii (Jayaram 1999) and a few authors even consider them as synonyms (Talwar & Jhingran 1991). The next species under question recorded in four surveys (Raghunathan 1978; Bai 1993; Devi et al. 1999; Raghunathan et al. 2008) is Colisa fasciata. This species is known to be a northern Indian species. C. lalia a very similar species is known from Chennai from the 1960s (Daniels & Rajagopal 2004) but did not feature in any of those surveys. Even though C. lalia was common for the past 50 years it was first officially reported only in 2004 (Daniels & Rajagopal 2004) and subsequently in 2005 OPEN ACCESS | FREE DOWNLOAD Date of publication (online): 26 November 2010 Date of publication (print): 26 November 2010 ISSN 0974-7907 (online) | 0974-7893 (print)

Chennai is amongst the few Indian cities that has had a long history of biodiversity studies.The erstwhile Madras that has since expanded considerably into today's Chennai has extensive and diverse aquatic habitats that amongst others attracted the attention of ichthyologists for at least 100 years.Two perennial rivers -Adyar and Cooum, numerous reservoirs that provide water for irrigation and drinking, seasonal tanks and extensive flood plains (example Pallikaranai Marsh), canals, channels, rice fields and open wells are typically freshwater habitats that add to the heterogeneity of the otherwise maritime landscape.
One of the earliest and most comprehensive of fish studies that considered a wide range of Chennai's aquatic habitats is that of Raj (1916).Raj's study carried out around 1910 is in fact the bench mark of the series of fish surveys that spanned the 100 years dealt with in this paper.Raj (1916) recorded a total of 57 species of which 44 species may be treated as primary freshwater fishes (Menon 1999).He mainly surveyed the Adyar and Cooum rivers and sporadically the drinking water reservoirs of Sembarambakkam (Chembarampakkam) and Red Hills.
Subsequent surveys of fish carried out by other authors focused mainly on the Adyar and Cooum rivers (Panikker & Aiyar 1937;Ganapati 1964;Evangeline 1967;Mary Bai 1993) with a few surveying the Chembarampakkam Lake (Raghunathan 1978;Daniels & Rajagopal 2004).The few other available publications are based on studies around Chennai and its environs (Devi et al. 1999) with a couple focusing on specific habitats (Raghunathan et al. 2005;Raghunathan et al. 2008).
The present study focused mainly on the freshwater habitats around Chennai such as the Rettai Eri (near Red Hills), Madipakkam Lake, wetlands of Velacherry, Kovillampakkam Lake, Adyar River and the Chembarampakkam Lake.Dipnet, dragnet and castnet were used for the surveys and in deep waters where these methods could not be used, fishermen's gill nets were regularly monitored.
A dip net of 45 x 30 cm with mesh size less than 1mm, a cast net of radius 480cm with mesh size 10mm and a dragnet of dimensions 210 x 120 cm with mesh size less than 1mm were used, apart from regularly monitoring fishermen's catches.Fishermen used four types of gill nets approximately 400 x 2 m each with different mesh sizes viz 25mm, 40mm, 55mm and 100mm.The species collected were identified using the available literature on freshwater fishes (Talwar & Jhingran 1991;Jayaram 1999).
The identity of a few primary freshwater fish which were recorded in the previous surveys conducted over the past hundred years by various authors (Raj 1916;Panikker & Aiyar 1937;Ganapati 1964;Evangeline 1967;Raghunathan 1978;Bai 1993;Devi et al. 1999;Daniels & Rajagopal 2004;Raghunathan et al. 2005;Raghunathan et al. 2008) have since undergone nomenclatural changes/ revisions and the present paper is based on the current identity and geographical distribution of the species.
Aplocheilus blockii is restricted to the west coast and very similar to A. parvus a species which is quite common in the Coromandel Coast (Menon 1999).Therefore in this paper the species present in Chennai and its environs is confirmed to be A. parvus which is frequently confused with A. blockii (Jayaram 1999) and a few authors even consider them as synonyms (Talwar & Jhingran 1991).
The next species under question recorded in four surveys (Raghunathan 1978;Bai 1993;Devi et al. 1999;Raghunathan et al. 2008) is Colisa fasciata.This species is known to be a northern Indian species.C. lalia a very similar species is known from Chennai from the 1960s (Daniels & Rajagopal 2004) but did not feature in any of those surveys.Even though C. lalia was common for the past 50 years it was first officially reported only in 2004 (Daniels & Rajagopal 2004)  ( Raghunathan et al. 2005).As both the species are very similar with reddish cross bands on the body it is likely that they have been confused.Therefore it is presumed that the record of C. fasciata is indeed C. lalia which is very common even today in Chennai and its environs.
Earlier taxonomic revisions have replaced O. melastigma which is the next species in question with Oryzias dancena and O. carnaticus (Daniels 2002;Parenti 2008).Oryzias sp. reported in the other surveys is being treated as O. dancena as the male specimens collected during the present study had filamentous extensions of the anal fin (Daniels 2002) and smaller adult size (Parenti 2008).
Puntius mahecola recorded by Raj (1916) is actually P. filamentosus.The two have frequently been confused and occasionally treated as synonyms (Menon 1999).P. mahecola is now known to be a species very similar to P. amphibius and the taxonomic status of P. amphibius is questionable (Pethiyagoda & Kottelat 2005).P. melonostigma recorded by Raghunathan et al. (2008) is being considered as P. mahecola (Pethiyagoda & Kottelat 2005).
Barring these, of the 66 species reported by earlier surveys, eight species were not recorded during the present study, while 17 others were added for the first time to the list of fishes known from Chennai.Thus, during the present study the presence of 75 species of fish has been validated.This is the highest number of primary freshwater fish species reported from Chennai and its environs.The eight 'missing' species are Nandus nandus, Clarias magur, Ompok bimaculatus, Sperata aor, Cirrhinus reba, Salmostoma acinaces, Puntius amphibius and Anguilla bengalensis.Poecilia reticulata, Xiphophorus helleri, X. maculatus and Brachydanio rerio reported from Chennai (Devi et al. 1999) have not been included in the checklist, as they were collected from a farm and not in the wild.
Four species of fish have been recorded after 100 years.Raj (1916) recorded Anguilla bicolor, Labeo calbasu, Wallago attu, Channa gachua in the year 1910-11 and these fish which were not reported in any other surveys were collected during the present study.Macrognathus aral though not collected in the recent study was captured from Chembarampakkam recently (E.Ramanujam pers.comm.).The non-native Osphronemus gourami is one other species not collected in the present study but has been added to the checklist as there is a recent report of its presence in the Adyar River (Knight 2010a).
Exotic fish recorded for the first time can be attributed to more recent introductions by the ornamental fish trade and aquaculture.Species like Pterygoplichthys disjunctivus, P. pardalis, Hemichromis bimaculatus and Amphilophus trimaculatum (Knight & Devi 2009a) are sure to have been brought in by the aquarium trade.Clarias gariepinus, Pangasius pangasius, Oreochromis niloticus, O. aureus (Knight & Devi 2009b) and the large carps have been brought in for aquaculture.
The recent record of northern Indian fish like Badis badis (Knight & Devi 2009c), Puntius gelius (Knight 2010b) and P. orphoides are rather interesting.These may have been brought in by the Krishna water transported to Chennai recently or earlier by ways of water imports from the north.What is more interesting is that these fish neither feature in the list of fishes of Hyderabad (Chandrasekhar 2004) which includes those of the River Krishna nor in the checklist of fishes of the River Krishna (Jayaram 1995).
Eighty-three species of fishes belonging to 49 genera and 23 families are known to inhabit the fresh water habitats of Chennai (Table 1).The presence of almost 90% of the fishes known in the past 100 years was validated in the present study, highlighting that species do persist.Conclusions and reports of species extinction can well be premature and misleading.

Table 1. A consolidated list of the fishes of Chennai
and subsequently in 2005 OPEN ACCESS | FREE DOWNLOAD Date of publication (online): 26 November 2010 Date of publication (print): 26 November 2010 ISSN 0974-7907 (online) | 0974-7893 (print) Editor: R.J.R. Daniels Manuscript details: Ms # o2519 Received 22 July 2010 Finally accepted 05 October 2010 Citation: Knight, J.D.M. & K.R. Devi (2010).Species persistence: a relook at the freshwater fish fauna of Chennai, India.Journal of Threatened Taxa 2(12): 1334-1337.Copyright: © J.D. Marcus Knight & K. Rema Devi 2010.Creative Commons Attribution 3.0 Unported License.JoTT allows unrestricted use of this article in any medium for non-profit purposes, reproduction and distribution by providing adequate credit to the authors and the source of publication.