Chapter 5 FISH CONSERVATION STUDIES I. Evaluation of changes in fish assemblages through comparison with past records Monitoring the occurrence of species and their populations has been a basis for * assessing the effects of environmental impacts (Spellerberg 1996). Fish fauna of an area may change for reasons such as habitat alteration, pollution and over fishing. To have an insight into the various threats that contribute to the decline of a species or an assemblage of species, there has to be a basic data of the distribution and abundance of the species of an area. Such information could be the basis of evaluation of past, present or future changes in the species composition and abundance of the fish fauna. Inspite of a number of publications on the freshwater fishes of Kerala, there have been no attempts to compile this information since Hora & Law (1941). In this chapter, an attempt is made to review some of the earlier work carried out prior to the present study. An attempt is also made to compare the present findings with some of the earlier records so as to evaluate changes that have occurred in the fish assemblages. Discussion Prior to the present study, about 149 species of freshwater fishes belonging to 24 families and eight orders had been recorded from Kerala, of which 73 species were reported after the study of Hora & Law (1941) (Table 5.1). Out of these 73 species, 24 were newly described species, of which 5 species are reported from northern Kerala . A total of 100 species were recorded by earlier workers from the rivers of Northern Kerala (Table 5.1). In the present study a total of 96 species of fishes were recorded from northern Kerala (Table 2.5), 14 species recorded by earlier workers were
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Chapter 5
FISH CONSERVATION STUDIES
I. Evaluation of changes in fish assemblages through comparison with
past records
Monitoring the occurrence of species and their populations has been a basis for
* assessing the effects of environmental impacts (Spellerberg 1996). Fish fauna of an area
may change for reasons such as habitat alteration, pollution and over fishing. To have an
insight into the various threats that contribute to the decline of a species or an assemblage
of species, there has to be a basic data of the distribution and abundance of the species of
an area. Such information could be the basis of evaluation of past, present or future
changes in the species composition and abundance of the fish fauna.
Inspite of a number of publications on the freshwater fishes of Kerala, there have
been no attempts to compile this information since Hora & Law (1941). In this chapter,
an attempt is made to review some of the earlier work carried out prior to the present
study. An attempt is also made to compare the present findings with some of the earlier
records so as to evaluate changes that have occurred in the fish assemblages.
Discussion
Prior to the present study, about 149 species of freshwater fishes belonging to 24
families and eight orders had been recorded from Kerala, of which 73 species were
reported after the study of Hora & Law (1941) (Table 5.1). Out of these 73 species, 24
were newly described species, of which 5 species are reported from northern Kerala .
A total of 100 species were recorded by earlier workers from the rivers of
Northern Kerala (Table 5.1). In the present study a total of 96 species of fishes were
recorded from northern Kerala (Table 2.5), 14 species recorded by earlier workers were
not recorded in the present study (missing species) (Table 5.2). Two of the 'missing
species' are 'single records', i.e., not recorded by any other worker after their first record,
either from the same or any other place. They are Pangio hashai and Glyptothorax
clevissinghi.
Two of these 'missing species' are commercially important and are exploitatively
fished for food (H.periyclrensis and Channa micropeltus). Use of various destructive
methods of fishing such as explosives or poison in the rivers may be the reason for their
disappearance. Dynamiting also destroys or alters the habitats of the fishes. It was
observed that these commercially important species were mostly found in the lowland
areas. Another threat faced by this group of fish was habitat loss by sand mining, which
disturbed and destroyed the breeding grounds. This was observed in all the major rivers.
Twelve of the 'missing species' were hill stream fishes. These species were affected
mainly due to alteration in their habitats. All these species were smaller in size and were
not commercially important. Pollution and deforestation were the other threats. Many of
the highland areas in Kerala are occupied by rubber, coffee, tea and cardamom plantation,
and pesticides and herbicides runoff from these plantation affecting the fish fauna.
In the present study 10 species that are not recorded by earlier workers are
reported. Of these 2 species are new additions to the fish fauna of Kerala, viz., Tor tor
and Esomus thermoicos, 3 species viz., Puntitis parrah, P. sophore, Barilius bendelisis
are widely distributed along the lowland waters. Dayella malabaricu was not listed by
earlier workers, but this species is included in the list due to its record from moderately
high altitudes. With the inclusion of these species to the earlier list the total number of
typical freshwater fishes recorded from Kerala is coming to 110.
New species from northern Kerala
Compared to the southern Kerala the number of new species recorded from
northern Kerala was less. Indra & Rema Devi (1981) and Rema Devi & Indra (1984)
described two new species from Silent Valley (Kunthi river), Homaloptera pillai and
Garra menoni respectively.
Shaji & Easa (1995) described another new species, H. Me~ioni, from
Indekkuthodu, a tribuatty of Bhavani river at Simvani in the Western Ghats.
Easa & Shaji (1995) recorded a new species, Pangio bashai, from the Chalickal
tributary of Chaliyar river in Nilambur. Manimekalan & Das (1998) described a new
species, qbptothorax davissinghi, from Karimpuzha of Chaliyar river basin.
Other additions from northern Kerala
Rema Devi & Indra (1986) studied the fish fauna of Silent valley National Park
and added Glyptothorux annandalei to the list of fish fauna of Kerala. Easa & Basha
(1995) added 26 species to the basic list. Of these 3 species were introduced and 2
species were migratory, excluding these 5 species, the following 21 species are included
to the basic list. They are Puntius clrola, Osteocheilus brevidorsalis. 0. Nashii, Labeo