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Chapter 6 Habitat Suitability Index (HSI) models of selected endangered and endemic fish species of Kerala 6.1. Introduction The convention on Intemational Trade in Endangered species (CITES) was established in 1973 under the auspices of the United Nations Environmental Programme (UNEP) identified that because of the biased nature of endangered species list and the lack of information regarding the endangered species the species to species approach to biodiversity conservation faces a major h
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  Chap er 6 Habi a Sui abili y Index (HSI) models of selec edendangered and endemic fish species of Kerala  6.1. In roduc ion The conven ion on In ema ional Trade in Endangered species (CITES) was es ablished in 1973 under he auspices of he Uni ed Na ions Environmen al Programme (UNEP) iden ified ha because of he biased na ure of endangered species lis and he lack of informa ion regarding he endangered species he species o species approach o biodiversi y conserva ion faces a major hurdle. They also poin ed ou ha habi a conserva ion hrough he es ablishmen of pro ec ed areas is he sui able me hod o overcome his problem. There are links be ween he diversi y of species (biological diversi y or biodiversi y) and he way ecosys ems func ions (Osbome, 2000). From his s a emen i is clear ha any change in he ecosys em will have significan influence on  he inhabi ing fauna and flora. Wi h his view Conserva ion In ema ional (CI) was formed in 1987 wi h a mission ha is focused on he pro ec ion and sus ainable use of biologically diverse ecosys ems and in 1989 hey developed he Rapid Assessmen Programme (RAP) o provide informa ion necessary o develop a ra ional conserva ionmanagemen s ra egy for a par icular area. More han 48%of na ural habi a s have beenseverely affec ed by human ac ivi ies (Hannah e al., 1994), and his process of habi a des ruc ion is probably he major cause of biodiversi y loss. This process is escala ing owing o he enhance living s andards and our ever increasing capaci y o exploi na ural resources. River fish provide a major source of food and recrea ion and are also useful in predic ing ecological condi ions in s reams and rivers. The bio ic diversi y and na ural charac eris ics of fish communi ies are direc ly rela ed o he varie y and ex en of na ural habi a s in a river basin (Cowx and Welcomme, 1998). In i s broades sense, he erm 95  habi a defines where a fish species lives wi hou specifying resource availabili y or use. (Cowx and Welcomme, 1998) Many species of fish are endangered because of habi a change brough abou by human in erven ions, and many more will be affec ed as al era ion of habi a and human abuse of freshwa er resources con inue (Pos el e al., 1996; Sala e a1., 2000; Tilman e al., 200l).Unders anding and managing human impac s on fish require a clear unders anding of he rela ionship be ween a species and i s enviromnen (Rosenfeld, 2003). The habi a associa ions, usage and requiremen s of fishspecies could reveal delica e rela ionships wi h heir environmen (Arun, 1998). Habi a requiremen s of fish have o be considered in any effor o main ain or rehabili a e rivers for fish biodiversi y (Freeman e al., 1997). S udies on he habi a use and requiremen s are very essen ial for he proper managemen and res ora ion ac ivi ies or ransloca ion of popula ions o new habi a s (Harig e al., 2000). Basic informa ion on life his ory andhabi a requiremen s are essen ial for species conserva ion. So iden ifying he sui e of condi ions ha defines he habi a requiremen of a species is a primary goal of aqua ic research. The concep of habi a requiremen , however, is poorly defined (Rosenfeld, 2003). Sui abili y cri eria res on he assump ion ha animals preferen ially occupy areas  ha bes suppor survival, grow h and reproduc ion (Freeman e al., 1997). Broadly speaking, requiremen s can be defined as fea ures of enviromnen ha are necessary for  he persis ence of individuals or popula ions (Bjomn and Reiser, 1991). The concep s of habi a selec ion, preference and requiremen are some imes confused in habi a s udies, and informa ion on habi a selec ion is frequen ly used o infer habi a requiremen (Rosenfeld, 2003). Habi a selec ion (ie. differen ial occupancy) occurs when an organism avoids a par icular habi a (nega ive selec ion) or uses a habi a in grea er 96  propor ion han i s availabili y in he environmen (posi ive selec ion) Selec ive use of differen habi a s is of en used o infer habi a preference. Bu rue preference can only be es ima ed when he influence of ex raneous fac ors like preda ion risk, compe i ion, availabili y of differen habi a s e c. are con rolled (Rosenfeld, 2003). Therefore, differen ial use of habi a s in he wild is usually referred o as habi a selec ion ra her han preference. On he o her hand, habi a requiremen s are abio ic fea ures of he environmen ha are necessary for he persis ence of individuals or popula ions. The individual habi a requiremen considers only he essen ial habi a condi ions where individuals will achieve posi ive grow h and reproduc ion. Bu he requiremen s for a popula ion (fundamen al niche) will include he habi a requiremen s of individuals and  he me apopula ion requiremen s such as landscape-scale fea ures rela ed o immigra ion and emigra ion ra es be ween popula ions and he minimum popula ion size (Pulliam 1988; Dunning e al. 1992) as well as broader regional cons rain s ac ing as condi ional fil ers on species presence (Poff 1997). Mos habi a models are based on covaria ion be ween environmen al variables and habi a use in he wild (Rosenfeld, 2003). S ream habi a s are s rongly hierarchical (Frissel e al. 1986; Hawkins er al.1993), and habi a associa ions can be modeled a a varie y of spa ial scales. According o Rosenfeld (2003), here are usually hree fundamen al ypes of predic ive models which can be used o define habi a requiremen s fi'om correla ive da a; dis ribu ional or macro habi a models, which predic he presence or absence of species a large spa ial scales (eg., wi hin differen drainage basins);capaci y models(mul iple regression), which predic densi y or popula ion size when a axon is presen (usually a he reach or channel uni scale);and microhabi a 97
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