This document discusses the introduction of exotic fish species in India. It provides examples of exotic fish species introduced in India from other parts of the world between 1870-1972 for purposes like experimental culture, mosquito control, and aquarium keeping. It then discusses the potential impacts of exotic fish introductions, including predation on native species, competition for resources, habitat alteration, transmission of diseases and parasites, genetic effects, and economic impacts. The document concludes with recommendations for steps that should be taken to prevent adverse impacts from exotic fish introductions.

1. SUBMITTED BY-
DEBIPRASAD KANTAL
FS-10/14
B.F.SC-3RD YEAR -2ND SEM
SUBMITTED TO –
PROF.S.K.ROUT
DEPT OF AEM

2. Introduction
• Exotic fish species have been receiving international attention in
different forums including the important ones like Convention on
Biological Diversity and also in the FAO Code of Conduct for
Responsible Fisheries.
• While much of the recent attention has been mainly focused on the
adverse impacts of alien fish introduction.
• There is realization that all alien species perform bad under every
circumstances.

3. Why are they introduced?
• Exotic species of the fishes were introduced in many parts of the world
with high hopes of promoting……..
1. Improving local fishery potential and for broadening species diversity in
aquaculture programmes,
2. Sport fishing,
3. For aquarium keeping,
4. Improving aquaculture or open water fishery productivity,
5. Controlling of unwanted organisms (mosquitoes)

4. Exotic fishes transplanted in
INDIA

5. Species Home Year Purpose
Tench (Tinca tinca) U.K. 1870 Experimental culture
Tilapia (Oreochromis mossambicus) Africa 1952 Experimental culture
Common Carp (Cyprinus carpio) Thailand 1957 Experimental culture
Grass Carp (Ctenopahryngodon
idella)
Japan 1957 Experimental culture and weed
control
Silver Carp (Hypophthalmichthys
molitrix)
Hong Kong 1959 Experimental culture
Tawes (Puntius javanicus) Indonesia 1972 Experimental culture

6. Species Home Year Purpose
1) Guppy
(Poecilia reticulata)
South America 1908 Mosquito control.
2) Top Minnow (Gambusia affinis) Italy 1928 Mosquito control.
Species Home Purpose
1) Live bearers
(27 species)
From various countries Aquarium keeping
2) Egg layers
( 261 speceis)
From various countries Aquarium keeping

7. A.Deliberate introductions
 Harvestable species – plants, fishes, rabbits in Australia, terrestrial plants
 Domesticated species
 To have 'familiar' species around
 Biocontrol mosquito fish (gambusia) predaceous on native fish eggs and
other
invertebrates; not very effective in controlling mosquitoes
 Ornamentals – garden plants, fishes, water hyacinth
 Bait (fishes)
Types/routes of introductions

8. B.Accidental introductions
 International commerce
with cargo (insects, frogs, lizards, spiders)
on hulls (barnacles, shipworm)
passive spread through navigation channels (many aquatic spp.)
on vehicles, boat trailers, airplanes
packing material (plants)
 Introduced accidentally with deliberately introduced species
 Escapes - aquarium trade, pet trade, bait, experimentation
 Mistakes
pink salmon
smelt
Types/routes of introductions

9. 1. predation on natives
2. competition
3. habitat alteration
4. parasites/diseases
5. genetic effects
6. ecosystem engineers – radically change structure of communities
and habitats, e.g., zebra mussels
Effects of exotics

10. • Top carnivores are often viewed the most significant threat as
introduced fishes.
• Although the generality of this statement is not borne out by an
analysis of the records in the Database on Introductions of Aquatic
Species (DIAS).
• Predation directly reduces population size of the prey species, and
may cause cascading ecological effects, such as increased plant
growth when herbivores are removed by top predators.
• Nile perch introduced into Lake Victoria - responsible for loss of
over 200 species of cichlids
Predation on natives

11. • Competition can occur between alien and resident species for food,
habitat, mates, or other essential resources.
• Tilapia (Oreochromis spp.) and especially the Mozambique tilapia,
Oreochromis mossabicus, are considered to be a threat to native
diversity in many areas where they have been introduced and most of
the impacts have been reported for inland waters.
• O. mossambicus competes for algae and other resources and has
displaced preferred species of mullet, Mugil cephalus, brackishwater
shrimp, Penaeus merguiensis, and milk fish, Chanos chanos in brackish
water fish ponds.
Competition

12.  Many species of freshwater animals greatly modify aquatic habitats
when placed into a new area, e.g. crayfish, common carp, and grass
carp.
 The Asian clam, Corbicula fluminea, was probably introduced into the
USA by Chinese immigrants as a food item (though possibly not for
intentional farming) in 1938.
 The clam has since spread widely to inland and coastal areas of 38
states in the USA. The most significant affect is in biofouling of
freshwater systems, but the clam can grow in such large numbers as
to alter the flow and substrate in streams and lakes and can remove
large amounts of phytoplankton from the water column.
Habitat alteration

13. • The spread of pathogens along with species transported or traded in
aquaculture is a serious concern that is being dealt with by several
international agencies such as FAO, World Health Organization (WHO),
World Trade Organization (WTO) and the International Office of
Epizootics (OIE).
• Of particular concern to exotic species is that the level of uncertainty will
be higher with new introductions on what pathogens may be present and
may cause problems in the new environment.
• For example, along with abalone that the California aquaculture industry
imported from South Africa came a sabellid worm parasite that caused no
problems in South Africa but has had devastating effects of abalone
under culture in California; the impact on other Californian mollusks is
unknown.
Disease Impact:-

14. • The economic impacts can be seen at two levels -
1. capture fisheries and
2. aquaculture.
• Since the exotic fishes never fetch higher price than the native varieties
and also the decline of native fish production is observed in the presence
of exotic species in natural waters , the total economic returns declined
for the stakeholders of the capture fisheries.
• In aquaculture however it provided immediate gain, in most cases
without consideration of the long term ecological consequences.

15. Extinction Due To Hybridization
• Hybridization between exotic and native species has not only
brought in genetic contamination but even resulted in species
extinction in some cases.
• Apache trout (Oncorhynchus apache) & Gila trout (O. gilae), two
native species of Southwest USA, have faced extinction primarily
due to hybridization with the introduced species, Cutthroat trout
(O. clarkii)

16.  Information on the biology of alien species and their probable impact on the
indigenous biodiversity has to be evaluated on a pilot scale before listing as
probable for introduction.
 Strict quarantine before entry into a new country / region.
 Dominantly herbivore species should get preference in selection for culture.
 Indigenous species should be preferred for stocking and given similar
treatments as given to exotics.
 The ratio of stocking surface, column and bottom feeders should be relevant to
the natural carrying capacity of these niches.
 Utilizing a vacant niche by appropriate exotic species
 Increasing exotic fish production in the introduced environment
 Not accompanying with pest, parasites or diseases such as “Ulcerative
syndrome” which might attack native species.
Stepes to be taken to prevent bad impact

17. • The global experience and the present status of
introduction of exotic species in different counties
including India their ecological, biological and genetic
impact analysis in this contribution indicates their
generally deleterious effect on autochthonous
species.
• In addition to direct devastating eco-biological
impacts, it has also been seen that some fish are even
extinct owing to loss of genetic variability and
heterozygosity.

18. • Consequence Of Alien Fish Introduction –
- by P. Das.(In Fishing Chimes, Vol 26 No. 10,January 2007).
• Plecostomus multiradiatus an armored catfish from freshwater ponds
near Kunnamkulam, Kerala and its possible impact on indigenous
fishes – by Ajithkumar, C.R., C.R. Biju and R. Thomas (1998). LAK
News, Limnological Association of Kerala, 1-2.
• Fish fauna of Bharathapuzha (Nila river), Kerala. J. Bombay nat. Hist.
Soc – by Bijukumar, A. and S. Sushama (In press).