Study of species richness, density and abundance is a fundamentalin biodiversity.
Malaysia has one of the largest continental shelf areas withinthe tropical world. In comparison with other areas, this region is very rich inbiodiversity, and considered to contain the greatest species diversity ofmarine life in the world According Mohsin & Ambak (1996), a total of 1500species of fishes were estimated to occur in Malaysian water. Mohsin & Ambak (1996) also described that marine fishes andfisheries of Malaysia and neighbouring countries have a total number of 710species. There also a total number of 358 commercially important marine fishesin the South of China Sea (Mansor et al., 1998). Chin (1998) has listed 376species of marine fishes representing the major group of food fishes thatcommonly found in Sabah, Malaysia in his book on the marine food fishes andfisheries of Sabah.
Marine-euryhaline water with 250 species and 81barackish-water species occupy the various coastal habitats such as mangrove,seagrass meadows, estuaries or mixed habitats, at one stage of their lifehistory. The largest number of marine species is found in coral reefs with 925species including 815 exclusive species. Fishes can be good signs of the healthof specific habitats or ecosystems (Harris, 1995; Helfman et al., 1999) and inmonitoring aquatic biodiversity (Leidy & Moyle, 1998). Based on AnnualFisheries Statistics (2005), the present marine fish landing in Malaysia is 1.2million which had arisen by about five times since fisheries statistics werefirst documented in 1961. Unfortunately, various coastal habitats have been traditionally andcommercially used in many ways, either directly which is used by in situ marineorganisms or their products, or indirectly which means any form of alienationof the habitats to various human uses such as aquaculture. The most importantcauses of current and future threats for the marine species are habitat lossand degradation, pollution, overexploitation through unsustainable aquacultureand fishing, eutrophication, maritime traffic, invasive alien species, humandisturbance, climate change and bycatch (Cuttelod et al.
, 2008; Coll et al.,2010). Lotze et al. (2011) stated that temporal patterns show thatoverexploitation and habitat loss are the main human factors of historicalchanges.
Some irrational and unsustainable fishing activities have significantnegative impacts on the fisheries resources and the ecosystem generally as wellas on the fish biodiversity, particularly in the benthic and the demersalenvironments. The impacts of such fishing activities could have either directeffect by removal of species or indirect effect via habitat modification or changesin prey or predator densities. These effects include bycatch which means thecapture of non-target species. Bycatch includes species that are unwanted andthrown away, and species that are retained and sold or known as byproduct suchas the juveniles and commercially important species. Golani et al.
(2002) describedthe abundant populations of fish of no economic importance is another exampleof economic burden to fishermen as fish are caught in fishing gears and have tobe discarded. Sediment disturbance and changes in turbidity in the ocean, cancause the oxygen level and water chemistry often stress fish populations. The onlythe hardiest species can survive the reduced water quality due to humandisturbance. Endemic fishes are therefore vulnerable to environmental changessuch as habitat degradation, human disturbance and pollution because almost noendemic marine fishes become an indicator to marine waters that are relativelymore homogeneous and habitats are less isolated. WEPA (2009) recently reported that there is vastimprovement in water quality attributed to good environmental managementpractices and increased enforcement.