Introduction of exotic fish & its impact
- 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).