© MAY 2019 | IRE Journals | Volume 2 Issue 11 | ISSN: 2456-8880 IRE 1703057 ICONIC RESEARCH AND ENGINEERING JOURNALS 354 Role Of Fish as Bioindicators: A Review OKWUOSA, OBINNA B. 1, 2 , EYO, JOSEPH E. 2 , OMOVWOHWOVIE EMMANUEL E. 3 1 Department of Science Laboratory Technology, Akanu Ibiam Federal Polytechnic, Unwana. 2 Department of Zoology and Environmental Biology, University of Nigeria, Nsukka, Nigeria 3 Department of Fisheries Technology Federal Polytechnic Ekowe Bayelsa State, Nigeria. Abstract- Growing human population and industrialization have led to the pollution of most aquatic ecosystems and consequent deterioration in environmental water quality. Indicator organisms are needed to improve assessment programmes on the ecological impacts of anthropogenic activities on the aquatic environment. Fish have been widely documented as useful indicators of environmental water quality because of their differential sensitivity to pollution. This study discussed the roles of fishes as bioindicators as uses as biological indicators. The comprehensive knowledge of taxonomy, habitat requirements, and physiology of fish is a key prerequisite of using fish as indicators. No other aquatic organism is suitable for the application of so many different methods which allow the evaluation of the severity of toxic impacts by determining the accumulation of toxicants in tissues, by using histological and haematological approaches or by detecting morphological anomalies. Due to its complex habitat requirements the fish fauna is a crucial indicator of the ecological integrity of aquatic systems at different scales, from microhabitat to catchment. Thus bioindication using fish represents a good monitoring tool especially with regard to both pollution aspects and to river engineering, e.g. river restoration and management. In order to further strengthen the role of fish as valuable indicators of the ecological integrity of aquatic systems, research is required ranging from the ecological demands of certain target species to ecosystem processes. There is need to broaden knowledge in aquatic environmental impact assessment by the use of fish as a bioindicator to assess aquatic environment. This study recommends the use of fish as valuable biological indicators in aquatic environmental pollution assessment. Indexed Terms- Fish, Bioindicator, Environmental Pollution, Biological indicator, Organisms, Ecotoxicity I. INTRODUCTION Bioindicators are organisms or communities of organisms, which reactions are observed representatively to evaluate a situation, giving clues for the condition of the whole ecosystem. The bioindicator has particular requirements with regard to a known set of physical or chemical variables such that changes in presence/absence, numbers, morphology, physiology or behavior of that species indicate that the given physical or chemical variables are outside their preferred limits (Whitfield and Elliott, 2002). Mostly, bioindicators are restrictively defined as species reacting to anthropogenical effects on the environment, whereas bioindicators for "natural" environmental changes and conditions are not much used. However, a general, all-encompassing definition of a biological indicator would be: "a species or group of species that readily reflects the abiotic or biotic state of an environment, represents the impact of environmental change on a habitat, community or ecosystem or is indicative of the diversity of a subset of taxa or the whole diversity within an area". The impacts of human activities on water bodies require appropriate monitoring tools to facilitate detection and characterization of the causes and sources of chemical, physical and biological impairment of the aquatic habitats. Among these tools, aquatic biota (fish, frogs, insects, benthos and plants) are identified as potential bioindicators to detect pollutant loads in water (Muyibi et al., 2008). In tracking long-term changes of a specific water body such as a river system, fish (such as Tilapia, Oreochromis mossambicus) are known to be useful and reliable indicators of long-term effects and broad habitat conditions as highlighted by many investigators over the years (Araújo et al., 2000; Vidal, 2008). Tilapia is the common name for around 70 species of perch-like fishes (family Cichlidae) native