Exotic Aquatic Organisms - International Development Research ...
Exotic Aquatic Organisms - International Development Research ...
Exotic Aquatic Organisms - International Development Research ...
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46<br />
Present Status of <strong>Exotic</strong>s in India<br />
The major exotic introductions and their impact on the indigenous fauna in ,eneral and<br />
aquaculture in particular, are dealt with in the following section and are listed in Tabls 1 and 2.<br />
Food Fishes<br />
Trout<br />
The areas around the Himalayas in the north and the peninsular hilly regions in the south are<br />
temperate in climate, and suitable for the culture of cold water fish. The first attempt to introduce<br />
trout as a sport fish was made in 1863 by Francis Day in Nilgiris of peninsular India. However,<br />
rainbow trout (Salmo gairdneri) from Sri Lanka, Germany and New Zealand were the first<br />
salmonids to be established in many streams of Nilgiris. The submergence of a number of trout<br />
streams in the newly formed reservoirs and increasing pollution of the remaining s'ieams have<br />
led to a sharp decline in the trout fishery in the post-independence era.<br />
In an attempt to improve the trout fishery efforts have been made to introduce some new<br />
species such as brown trout and tiger trout (hybrid between brown trout and eastern brook trout<br />
(Salvelinusfontinalis) and sockeye salmon (Onchorhyncus nerka). Among the various species of<br />
trout introduced in Nilgiris so far, only the rainbow trout has survived under the existing climatic<br />
conditions. It appears that trout culture is no longer an economical proposition in NiIgiris region<br />
due to pollution of streams and serious disease problems (Sreenivasan et al. 1988). Similarly, in<br />
the Himalayan region, introduction of trouts commenced after nearly three decades of their<br />
introduction in the Nilgiris region. Of all the introductions into the Himalayan region only brown<br />
trout provides a fishery on a commercial scale in streams (Sehgal 1988). Though attempts are<br />
being continued to establish trout populations in the cold regions of northern and eastern India,<br />
the success is not always commensurate with the efforts, largely due to stocking of undersized<br />
fish and the increasing pollution of streams. However, in some high altitude lakes, like Deodital<br />
of Central Himalayas, the brown trout has established itself and is breeding naturally (John and<br />
Prasad 1988).<br />
According to Jhingran and Sehgal (1978), altogether 719 km of trout streams are available<br />
in the country, in addition to over 4000 ha of natural and man-made lakes with trout ?opulations.<br />
The analysis of creel census data provided by the anglers has revealed that the brown trout<br />
catches were around 608-640 g/rod/hr/km fishable length in the Himalayan region in 1971, while<br />
in the Nilgiris in the south, the catch was about 457 g/rod/hr/km during 1966-68 (Jhingran and<br />
Sehgal 1978).<br />
As compared to some other introduced fish species, the trout have remained noncontroversial<br />
because of their restricted distribution and lack of indigenous cold water sport<br />
fishes. The populations of Schizothorax spp. do not appear to have been adversely affected by<br />
the presence of trout.<br />
Golden carp<br />
The crucian carp or golden carp (Carassius carassius) was introduced into India in 1874 in<br />
the Ooty lake at Nilgiris. The fish thrived well in Nilgiri waters and formed an important fishery