Study of such fishing activities could have either direct

Study of species richness, density and abundance is a fundamental
in biodiversity. Malaysia has one of the largest continental shelf areas within
the tropical world. In comparison with other areas, this region is very rich in
biodiversity, and considered to contain the greatest species diversity of
marine life in the world According Mohsin & Ambak (1996), a total of 1500
species of fishes were estimated to occur in Malaysian water. Mohsin & Ambak (1996) also described that marine fishes and
fisheries of Malaysia and neighbouring countries have a total number of 710
species. There also a total number of 358 commercially important marine fishes
in the South of China Sea (Mansor et al., 1998). Chin (1998) has listed 376
species of marine fishes representing the major group of food fishes that
commonly found in Sabah, Malaysia in his book on the marine food fishes and
fisheries of Sabah. Marine-euryhaline water with 250 species and 81
barackish-water species occupy the various coastal habitats such as mangrove,
seagrass meadows, estuaries or mixed habitats, at one stage of their life
history. The largest number of marine species is found in coral reefs with 925
species including 815 exclusive species. Fishes can be good signs of the health
of specific habitats or ecosystems (Harris, 1995; Helfman et al., 1999) and in
monitoring aquatic biodiversity (Leidy & Moyle, 1998). Based on Annual
Fisheries Statistics (2005), the present marine fish landing in Malaysia is 1.2
million which had arisen by about five times since fisheries statistics were
first documented in 1961.

Unfortunately, various coastal habitats have been traditionally and
commercially used in many ways, either directly which is used by in situ marine
organisms or their products, or indirectly which means any form of alienation
of the habitats to various human uses such as aquaculture. The most important
causes of current and future threats for the marine species are habitat loss
and degradation, pollution, overexploitation through unsustainable aquaculture
and fishing, eutrophication, maritime traffic, invasive alien species, human
disturbance, climate change and bycatch (Cuttelod et al., 2008; Coll et al.,
2010). Lotze et al. (2011) stated that temporal patterns show that
overexploitation and habitat loss are the main human factors of historical
changes. Some irrational and unsustainable fishing activities have significant
negative impacts on the fisheries resources and the ecosystem generally as well
as on the fish biodiversity, particularly in the benthic and the demersal
environments. The impacts of such fishing activities could have either direct
effect by removal of species or indirect effect via habitat modification or changes
in prey or predator densities. These effects include bycatch which means the
capture of non-target species. Bycatch includes species that are unwanted and
thrown away, and species that are retained and sold or known as byproduct such
as the juveniles and commercially important species. Golani et al. (2002) described
the abundant populations of fish of no economic importance is another example
of economic burden to fishermen as fish are caught in fishing gears and have to
be discarded.

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Sediment disturbance and changes in turbidity in the ocean, can
cause the oxygen level and water chemistry often stress fish populations. The only
the hardiest species can survive the reduced water quality due to human
disturbance. Endemic fishes are therefore vulnerable to environmental changes
such as habitat degradation, human disturbance and pollution because almost no
endemic marine fishes become an indicator to marine waters that are relatively
more homogeneous and habitats are less isolated.  WEPA (2009) recently reported that there is vast
improvement in water quality attributed to good environmental management
practices and increased enforcement.

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