When, in the 1970s in Malaysia, rice cultivation
intensified (double rice cropping, pesticides) yields of
T. pectoralis declined dramatically (Tan et al. 1973;
Ali 1992a, b). Also, in Vietnam, intensification of
rice culture (double or triple rice cropping with
short duration rice varieties, lower water levels,
pesticide use) led to a reduction in fish yield (Lazard
& Cacot 1997). From this and the results in
Tables 2 and 4 it seems that rice intensification
alters the aquatic environment in an unfavourable
way for T. pectoralis. Indeed, although T. pectoralis
can be found in rice fields, the adult fish prefer the
deeper water of ponds and consider the rice field as a
favourite site for building their bubble nests
(Heckman 1979). In Sri Lanka, where T. pectoralis
was introduced into rice fields (de Zylva 1999), the
species are no longer found; it can now be found in
marshes contiguous with rice fields (Fernando
1995).
When, in the 1970s in Malaysia, rice cultivationintensified (double rice cropping, pesticides) yields ofT. pectoralis declined dramatically (Tan et al. 1973;Ali 1992a, b). Also, in Vietnam, intensification ofrice culture (double or triple rice cropping withshort duration rice varieties, lower water levels,pesticide use) led to a reduction in fish yield (Lazard& Cacot 1997). From this and the results inTables 2 and 4 it seems that rice intensificationalters the aquatic environment in an unfavourableway for T. pectoralis. Indeed, although T. pectoraliscan be found in rice fields, the adult fish prefer thedeeper water of ponds and consider the rice field as afavourite site for building their bubble nests(Heckman 1979). In Sri Lanka, where T. pectoraliswas introduced into rice fields (de Zylva 1999), thespecies are no longer found; it can now be found inmarshes contiguous with rice fields (Fernando1995).
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