17
4
According to the Management Entity, PD/
A CRSP does not introduce alien species into
areas where they have not already been
introduced.
Efforts to develop hydrological resources for economic development (e.g.,
hydropower) have reduced water levels and depleted wetlands. Asian reservoirs
are usually constructed to be multipurpose water bodies that will serve the fishing
industry, agriculture community, local water users and power generation
(Amarasinghe et al. 2001). The conversion of flowing rivers to reservoirs has
changed the species assemblages in many rivers since reservoirs favor lacustrine
species, not riverine. Typically, to maintain or expand fisheries, reservoirs are
stocked with lacustrine species, which are often alien species (e.g., carps and
tilapias) and potentially invasive.
Aquaculture of alien species, a common activity in reservoirs, has
contributed to local economies and food security. However, poorly managed cage
and pen aquaculture production can have negative consequences on human
livelihoods, since organic loading from added feed and fish excretion reduces
water quality (Starling et al. 2002, Santiago 1994). Given that fish often escape
from their cages and pens, aquaculture can increase the region's risks of adverse
impacts from an alien species (Courtenay and Williams 1992). Furthermore,
cages and pens can occupy vast areas of the water body and thus interfere with
natural movements and reproduction of the native fish species (Delos Reyes 1993,
Pullin et al. 1993).
Until recently, aquaculture has depended on a handful of species
throughout the world (Welcomme 1984). Several development assistance projects
have been instrumental in bringing alien species into countries where they had
not been previously found
4
. The results of these introductions have not always
been beneficial; projects that sought to improve the livelihoods of local
communities may have actually resulted in long term costs that exceeded the
short term benefits derived from increases in fisheries production (Msiska et al.
1991). If development projects are to provide long-term benefits to local
communities, project managers must evaluate the potential effects of IAS on
their projects and natural systems.
Some development agencies have begun to recognize the links between
development projects and IAS. For example, USAID has sponsored this
assessment to better understand the linkage between development projects and
IAS in the freshwater systems of Southeast Asia; the Swedish International
Development Cooperation Agency has sponsored a study on the role of alien
species in aquaculture in the Mekong.
Tilapia aquaculture pond in Philippines (A. Gutiérrez), tilapia specimen. (Norainy
Mohd Husin).