Aquaculture and Environment · environment and aquaculture, management of aquaculture and the...

Pages 118 – 142. In: Ezenwaji, H.M.G., Inyang, N.M. and Orji, E. C. (Eds.). Proceedings of the UNDP-Sponsored Training Workshop on Artisanal Fisheries Development, held at University of Nigeria, Nsukka. October 29th – November 12th, 1995.

118

Environment and Aquaculture

EYO, J. E. Fisheries and Hydrobiology Research Unit, Department of

Zoology, POBox 3146, University of Nigeria, Nsukka. Email: [email protected]

ABSTRACT The paper addresses sensitive issues on environment and aquaculture with particular reference to the types of aquaculture (polyculture; intensive, semi-intensive and monoculture; intensive, semi-intensive/extensive aquaculture) that are environmentally save and socio-economically sustainable in Nigeria. Aquaculture impact on the environment, such as destruction of habitats along with its flora and fauna, pollution of the receiving fresh water ecosystem to specific public health hazard, are discussed. INTRODUCTION Aquaculture has considerable impact on the environment which may or may not be beneficial, and may include destruction of natural habitats, reduction of the abundance and diversity of plants and animal, changes in the soil, water, landscape, biotic and abiotic qualities. Simon (1989) has discussed similar problem vis-à-vis the development of agriculture. The fisheries sector of the developing counties contributes effectively toward animal protein security with a short fall from the capture fisheries. Aquaculture may thus be expected to make-up for the short fall. Aquaculture will remain the contributory part to the developing countries

mailto:[email protected]

Eyo, J. E. Environment and Aquaculture 119

economy, thus it is essential that the potential negative effects of development of aquaculture be appraised. Most aquaculture in Nigeria are extensive, uses low inputs and apparently, may have limited impact on the environment. That aquaculture might possibly have adverse impact in tropical regions has only begun to be recognized, let alone be subject of research, and inevitably, review drawn from the tropics. Emphasized are the relationship between the environment and aquaculture, management of aquaculture and the environment. This paper gives working definitions of terms (aquaculture and environment), discusses broad concepts, summarizes the status and future of aquaculture in Nigeria, emphasizing the search for sustainability in the face of rapid change. AQUACULTURE Aquaculture is the farming of aquatic organism, including fish, molluscs, crustaceans and aquatic plants among others. According to Pullin (1993), farming implies some form or intervention in the rearing process to enhance production, such as regular stocking, feeding and protection from predators among others.

Based on the energy inputs aquaculture can be broadly categorized as extensive, having no feed or fertilizer inputs semi-intensive, having some fertilizers and /or feed input; and intensive, largely reliant on feed inputs (Edwards e al, 1988). According to Pullin (1993), enhanced fisheries resemble extensive aquaculture with low levels of human intervention. The classification of aquaculture based on economic goals into “commercial” and “entrepreneurial” has been attempted in Nigeria. According to Satia (1990), the Federal Department of Fisheries reported that existence of about 2,000 small-scale earthen ponds (0.02 to ha each) and over 3, 000 homestead concrete ponds (25 – 40 m2) belonging to over 5,000 Nigerian. Furthermore, there are about 60 commercial aquaculture farms, 3 ha and above. The

Proceedings of the UNDP Training Workshop on Artisanal Fisheries Development

120

ultimate areas put to aquaculture was about 5,000 ha of freshwater and 230 ha or brackish water (Satia, 1990). In Nigeria all the homestead ponds are subsistence, and virtually all aquaculture has a profit motive in each or kind.

Extensive and semi-intensive freshwater aquaculture systems are the most widely practiced and account for 97 % of African’s total aquaculture production (Satia, 1990). Inputs are largely domestic wastes and plant wastes, or by-product such as compost. Annual yield vary with quality and quantity of inputs ranging from 0.5 to 5.0 tha-1. Additionally, semi intensive farming systems are becoming more prevalent, and finding acceptance. In addition to natural productivity, the system receives applications of manure, inorganic fertilizer and where possible, artificial feeds or wastes from farm produce, and animal droppings. ENVIRONMENT The environment in defined broadly as the whole ecosystem and its living and non-living components/resources, including human beings. Thus this paper addresses the effects of aquacultural practices to the environment, the impact of aquatic ecosystem on aquaculture, socio-economic impact of aquaculture development and lastly sustainability of aquaculture in Nigeria. EFFECTS OF AQUCULTURAL PRACTICES TO THE ENVIRONMENT Implimentationary Phase: The development of inland aquaculture facility (ponds) often results in disafforestation, displacement of resident macro fauna and mass destruction of soil micro and macro flora and fauna. For instance, there have been a number of accusations that fish farm development has a negative impact on wildlife, in particular predatory birds and mammals (Anon, 1988; Whilde, 1990). The development of coastal aquaculture often leads to destruction of coastal


mangrove and shoreline vegetations. Johannes (1975) reported that the construction of coastal aquaculture facilities has led to severe changes in hydrographic regimes, caused disruption of spawning runs of important fish species and thus reduced the numbers of recruits of various fish species. Furthermore, the earth moved during construction has contributed to siltation of our waterways. Also, salt-water intrusion into some of these freshwater aquifers may be accompanied by salinization of soils (Jayasinghe and Posilva, 1990), thus resulting in further devaluation of already marginal agricultural land. CULTURAL PRACTISES Output from Extensive and Semi-Intensive Aquaculture: King (1993) observed that the few direct negative impacts of these aquacultural practices on environment may include those arising from implementation phase, particularly loss of wetland habitats, which support diverse flora and fauna. In Mozambique, Pauly et al. (1989) reported that about 680.000 ha of mangrove which has been marked as natural nursery grounds for various species of fish were destroyed. Health hazards exiting from extensive and semi-intensive aquaculture has been reported. For instance, King (1993) observed that aquaculture facilities could create new habitats for snail intermediates hosts of schistosomiasis, black flies for onchocerciasis and mosquitoes for malaria, filariasis and viral infections. In human excreta feed aquaculture as highly practiced in Southeast Asia, the schistosome eggs in the excreta facilitates the infestation of the snail. The cercariae, which are shed by the snail into the pond, bore into human skin when in contact with the pond water. Edwards (1985) suggested that avoiding the use of fresh excreta in which the eggs can survive up to one week was a useful means of checking the infection.


122

CIFA (1987) reported that onchocerciasis whose vector is the black fly (Simulium) does not occur in slow-flowing or stagnant water such as fishponds, but may be found in associated raceways and water channels. Interactions between the vector and aquaculture concern mainly the effects of insecticides (DDT) use in vector control may be toxic to the fish. Calamari (1985) reported that several chlorinated hydrocarbons including DDT have been banned in some West African countries and replaced by less toxic organophosphorus compounds. It is worthy to note that in these West African countries, these chemicals are still seriously in use and openly displayed in market stalls, due to non governmental enforcement of the prohibition. King (1993) reported that recently built ponds are the habitat of malaria vectors such as Anopheles funestus and Anopheles gambiae.

Output from Intensive Aquaculture: The above reviewed on the output from the non-intensive system may be applicable to the intensive systems. According to Beveridge and Phillips (1993), the area of concern under intensive aquaculture wastes are; uneaten food, excreta, chemicals, therapeutants, dead fish and escaped fish. Uneaten food, fecal and urinary products: Beveridge etal. (1991) observed that a proportion of food remains uneaten because the quantities and qualities are often inappropriate and because aquaculture systems and their management tend to be perplexed with optimization of ingestion. Studies indicate that between 1 % and 30 % of the feed within intensive aquaculture are uneaten (Beveridge 1984; Beveridge et al, 1991). Furthermore, the eaten but undigested fraction of feed, together with mucus, sloughed intestinal cells and bacteria, are voided as feaces, whilst the digested portion is absorbed and metabolized. The waste products of such metabolism are excreted as either ammonia or urea. The data


on fecal production and ammonia excretion by fish are presented on Tables 1 and 2. It is worthy to note that the quantities of uneaten food, feaces and urinary products vary with species and the type of food and are influenced by body size and season (metabolic rate). It has been reported that the waste production within a system increases with biomass and with food use, thus although it is impossible to predict farm effluent characteristics form waste production data alone. There exist strong correlations between waste parameter like suspended solid (SS) and BOD and between NH3 and chemical oxygen demand (COD) (Alabaster 1982). At this point it is worthy to assess the environmental impact of uneaten feed, fecal matter and urinary products.

Table 1: Estimated diet digestibilities (%) and fecal production (g dry wt. 100g-1 ingested) from data for dietary components and proximate analysis (% dry wt). Typical diets for farmed tropical fresh water species have been used (modified from Beveridge et al. 1991)

Catfish Carp Tilapia Dietary Diet

(%) Digestibility

diet (%) Diet (%)

Digestibility (%)

Diet (%)

Digestibility (%)

Protein 35 80 35 85 35 70 Lipid 7 97 15 70 6 90 Carbohydrate 48 50 40 70 50 60 Ash 10 50 10 50 9 50 Overall diet digestibility (%) 64 73 64 Fecal production (g. 100g-1) 36 27 36

Boyd (1978) reported that although aquaculture

effluents characteristically have low levels of waste, nevertheless, even the waters drained prior to harvesting can have significantly higher level of suspended matter, BOD, COD, total phosphorus and total ammonia-nitrogen than the


124

receiving streams. According to Kilambi et al. (1976), Alabaster (1982), Bergheim et al. (1982), Beveridge (1984), Munro et al. (1985) and Philips et al.(1985, 1986), the discharged aquaculture effluents causes measurable changes in the water chemistry of the receiving bodies. The principal effect on running water is to increase ammonia-nitrogen and phosphorous concentration immediately downstream off the point of discharge. In addition, cage culture causes a long-term increase of lake carbon, nitrogen and phosphorous levels. Rast et al. (1989) observed that increase in nitrogen and phosphorous, or one of the other lead to eutrophication, thus a general elevation in algal densities. Stirling and Day (1990) reported that cyanobacteria become dominate as they are tolerant to high P: N ratios and such shift in phytoplankton community structure will have both hydrological and autotrophic food webs implications. Table 2: Ammonia excretion rates for carps and tilapias (Beveridge and Philips, 1993) Species Production rates C. carpio a110-581 mgN.kg-1. day 1-1

O. mossambicus b1.72 mgN.kg-1.hour –1

O. niloticus c1.7-9.4 mgN.kg-1.hour-1

Furthermore, changes in the benthic environment immediately under cages cultures arising from sedimentation of solid waste (uneaten food) have been reported by NCC (1991). The extent of sedimentation is governed by stokes law and dependent upon particle size and density. These sediments are richer in P, N and C levels than natural sediments and bacterial decomposition of organic matter can result in anaerobic conditions. Under completely anoxic conditions H2S has been reported to be evolved. The release of H2S gases may be enhanced by bioturbution caused by the high number of pollution-tolerant macroinvertebrates (Enell and Lof, 1983). The changes in water quality, aquatic community structure and productivity caused by intensive aquaculture


may be more rapid in the tropics, due to high ambient temperature. CHEMICAL AND DRUGS Chemicals and drugs either extensively used in the European aquaculture or less extensively utilized as in the African traditional aquaculture includes compounds deliberately employed in the hatchery (to induce spawning, control stickiness of eggs, determine sex), control pests (pesticides, insecticides, molluscicides, piscicides, herbicides), to improve productivity (lime fertilizers), treat or control disease (fungicides, parasiticides, disinfectants), control fouling and pacify fish during handling (anesthetics) among others. The chemical and drugs often leach into the aquatic environment. Lime increases the pH of pond soil and water, increases alkalinity and hardness, reduces humic acid content in the water and generally improves benthic and phytoplankton production (Boyd 1979). Boyd (1979) observed that lime has minimal adverse effect on the environment even when the ponds are unduly leaking and that fertilizers generally play major role in improving water quality when not applied in excess. Therapeutants usage in aquaculture has been reviewed by Solbe (1982). Aquaculture tends to rely on a fairly small number of the therapeutants. Furthermore, evidence form a tropical fish disease workshop (Shariff, 1989) suggests that comparatively the number of therapeutants used in tropical aquaculture was far lower than those used in the temperate aquaculture. Pantulu (1979) reported the common use of therapeutants like formalin, potassium permanganate, dipterex and malachite green in tropical aquaculture (Table 3). Administration of these chemical may be through bath, injection or administration in food, of which bath treatment is the most common practice for dealing with parasites (Sarig, 1971). Studies on the effects of these therapeutants on the pond ecology reveals that formalin is toxic to algae at around 0.7-1.2 mg/l and to zooplanktons at


126

around 5 mg/l (NCC, 1991), whilst the concentrations used in ponds varied typically between 25 and 100 mg/l (Table 3). Studies on the use of organophosphate insecticide, dipterex, (2,2,2-trichloro-1-hydroxyethyl phosphate) to control fish ectoparasites, predatory insects and large zooplankton in fry ponds revealed dipterex to be highly toxic to fish and rapidly hydrolyzed under tropical conditions (pH 7.5; 25 - 300 C) (Ellis, 1974). Table 3: Concentration of chemical used in the control of tropical fish diseases (Beveridge and Philips, 1993) Agent Concentration

(ppm) Use

Formation 25 – 100 Widely used for control of protozoa and ectoparasites

KMnO4 15 – 30 Bacteria, protozoa, ectoparasites

Malachite green

a0.1 - 0.15 Widely used for control of fungi, protozoa and ectoparasites

Dipterex 0.25 - 2.5 Control of ectoparasites (e.g. Pactyiogyrus sppand Gyrodactylus spp)

a Unless bath treatment for fungi, such as saprolegnia, when concentration of 65 – 70 ppm are more typically employed. Antibiotics are not commonly used in tropical aquaculture, although when in use are administered through injection or in food. According to Rasmussen (1988), the uptake, distribution and elimination of therapeutants are


determined by species, the formulation and physiochemical characteristics of the therapeutic, feed composition and environmental factors. In a comparison of antibiotic accumulation and elimination in tilapia and rainbow trout tissues, Miller (1984) found that levels were higher in the liver than in the muscles tissues. Among the tilapia all residues were eliminated within 96 hours while in the rainbow trout they were still detectable 144 hour after administration. The differences were attributed to varied temperature 27 % for tilapia and 6 – 8 % for rainbow trout (Table 4). Table 4: Toxic effects and nutritional hazards associated with the use of antibiotics in fish (Michael, 1986)

Undesirable effects on fish Drug Acute

toxicity Other effects Persistence

of residues Risks for human beings

Kanamycin Liver and kidneys of adult trout

- 8 – 10 days Allergies and neurosensory disorders (internal ear)

Chlorampheniol - Growth retardation after prolonged treatment

28 – 72 hours

Bone marrow aplasia

Oxytetracycline Rare Growth retardation, sterility immunosuppression

15–20days 60 days

Digestive disorders Hepatorenal disorders

Erythromycin - Reversible nephrotoxicity

48-72 hours Rare allergies

Suphonamides - Sterility and nephrotoxicity after prolonged use

8 days 15 days

Hepatorenal disorders Leukopenia, allergy

Trimethroprim or ormetoprim

- - 48 hours – 5 weeks

Hepatorenal disorders leukopenia, allergy

Nifurpirinol Rare - 24 – 48 Hours

Carcinogen


128

Furthermore, Austin (1985) observed decreases in bacterial number in effluent during antibiotics chemotherapy, indicating that the antibiotic adversely affected the natural bacterial communities. It has been clearly established that the continuous use of antibiotics in aquaculture usually led to increase in drug resistance among important groups of pathogenic fish bacteria (Austin, 1985 and Michael, 1986). No studies of drug resistance among fish pathogens have been carried out in the tropics. This aspect constitutes an area of tropical aquaculture research need. FERAL ANIMAL ESCAPES Despite all efforts through the use of screened sluice gates and monks, species originally confined to aquaculture systems eventually escape, often in large numbers, although they may not necessarily successfully colonize natural waters. The adverse impact of possible colonization can be summarized as alteration of the host environment, disruption of the host community (e.g. elimination of local species by competition and predation), genetic degradation of local stocks, introduction of disease and various socio-economic effects of fisheries importance. For instance, tilapias have caused the decline of native fish stock in various aquatic ecosystems world-wide, (Bruton, 1986). High fecundity, rapid early development, flexible phenotypes, wide environmental tolerance, catholic habitat preference and feeding habits are common among invasive species (Bruton, 1986). With regards to genetic degradation of local stocks, the fear is that genetic interactions between farmed and wild stock will adversely affect gene pools through the introduction of non adaptive genotypes to wild populations (Skaaka et al., 1990). Furthermore, it is possible to spread diseases through the movement of fish. The risks associated with aquaculture are believed to be particularly high given the conditions under


which fish are generally cultured (high stocking densities, sub-optimal water quality, relatively higher feed and fertilizer input). For instance, the spread of fish disease in Malaysia through the importation of pathogenic bacterial and parasites with grass carp (Ctenopharyngodon idella) and bighead carp (Aristichtys nobilis) has been reported (Shamsudin, 1986). There were differences in perception of the problems posed by feral species. Welcome (1988) observed that an objective evaluation may be difficult given the many difference views of natural ecosystems. From a strict conservation standpoint any change to the aquatic community is detrimental. Conversely, rural societies worldwide may be tolerant and accommodative of introductions is such lead to the improvement in animal protein security. THE IMPACT OF AQUATIC ECOSYSTEM ON AQUACULTURE The impact of aquatic ecosystem on aquaculture is yet to be given full attentions and may relate to the water quality conditions necessary for the establishment of aquaculture facilities. The quality of the aquatic medium largely determines success in aquaculture. In Africa, Alabaster (1981) and Calamari (1985) have identified pesticides and organic pollutants with high Biological Oxygen Demand as the potential sources of aquatic pollution of inland waters thus rendering such waters if not treated unsafe for aquaculture. Selah et al. (1988) in a study of man made reservoirs used for the drainage of agricultural wastewater in Egypt reported the potential dangers from inorganic pollutants (pesticides, fertilizers and heavy metals) with regards to fish production. The estuarine and costal environments may contain noxious algal species which can affect virtually every type of aquaculture operation. Shumway et al. (1990) observed that cultured bivalves react to the presence of toxic dinoflagellate in a variety of ways which includes, shell valve closure, reduced filtration relate; and change in oxygen consumption


130

among others. The implication is that bivalves are affected during toxic dinoflagellate blooms to a vary extent of starvation and death (Kodama, 1990). Apart form shellfish (bivalve), toxic dinoflagellates also affect fish. Fish larvae died rapidly on a diet of Gonyaulaxexcava a or of copepods which had been eating the dinoflagellates (White et al,. 1989). Toxicity of dinoflagellates to adult marine and freshwater fish was investigated experimentally by Saite et al. (1985). The raphidophyte Heterosigma akashiwo has caused major losses of caged fish in Japan and Europe since the early 1970’s (White, 1988). Nontoxic algae cause similar damage by creating anoxic conditions (Table 5). Pyredinium has caused extensive dead of marine life during decomposing bloom in Sabah, Malaysia (Maclean, 1989). Tainting of fish from bloom is another factor to be considered. Earthy tainting of freshwater fish flesh with geosmin was reported by Stirling and Day (1990). Furthermore, a bloom of the diatom Rhizosolenia chunli in southeastern Australia in 1987 caused a strong bitter flavor in cultured and wild bivalve molluscs, over a seven-month period, about 500 tones of mussels worth 1 million US dollar were discarded (Parrey et al., 1989). In summary, many toxins are produced by algae which in blooms can render bivalve molluscs toxic to humans. Some toxic can be fatal to humans, like paralytic shellfish poisons (PSP) and amnesic shellfish poison (ASP) while others, diarrheic and neurotoxic shell fish poisoning, are milder but severe enough to close fish farms and fisheries for a long period.

t

SOCIOECONOMIC IMPACTS OF AQUACULTURE DEVELOPMENT It is worthwhile to assess the human ecological impact per se of aquaculture development. This section will examine the potential impacts of aquaculture development on households, its intra-community consequences, impacts on external influences, as manifested in modifications of policy, programs


Table 5: Incidence of toxic alga problems in developing country aquaculture (Maclean, 1989) Country (site)

Algal species

Effect Status Relationship to aquaculture

Brunei Darussalam

P. bahamense PSP Chronic since

Losses to mussel farmer

China (Hupei and Shandong Prov)

Unknown Shrimp kill

First record, 1989

80 % shrimp in 2, 000 ha of ponds killed.

India (Tamil Nadu and Karnataka)

Unknown PSP First record PSP, DSP found in shellfish harvest beds, Karnataka

Rep. of Korea (mainly Jinhae Bay)

26 species Various Chronic increasing

“Sever damage” to farms

Malaysia Chattonella marina

Shrimp First record, 1985

Heavy losses in shrimp farms

Malaysia (Saoah)

P. bahamense var. compressum

PSP Chronic since 1976

Experimental cultured oysters toxic

Papua new guinea

P. bahamense var. compressum

PSP May be cyclic

Experimental cultured oysters toxic

Philippines P. bahamense var. compressum

PSP Increasing since first record, 1983

Caused mainly by eating cultured muscles

Singapore Cochlodinium Chattonella Heterosigma

First kills Occasional Mortality of groupers in cages

and projects, or in the provision of supplementary inputs to aquaculture and complementary physical and institutional infrastructures. Conclusively the proceeding section considering the non-physical, physical, human and environmental issues raised will examine if aquaculture is environmentally safe and socio-economically sustainable for Nigeria.


132

The introductions of aquaculture have serious social environmental impact when considering land tenure and use rights in Nigeria. The assess to land and water resources and their like, are vested on the individual. These have led to the non availability of land to most prospective aquaculturist. Where aquaculture has been adopted as in the Cross River State, Nigeria, the wet land is highly exploited. Adoption of aquaculture in this area is not perceived as disrupting the pre-existing labour allocation, because of having only a low labour demand often contracted during harvesting period. Where semi-intensive aquaculture is practiced, better use is made of on-farm resources and provided greater benefits than do customary practices alone. These lead to considerable advantages such as additional income, enhance social status within the community, provision of additional items for reciprocal exchange and lastly improve the household nutrition. Unlike traditional agriculture, the possession of fish ponds is seen as a major investment by members of the community thus is adopted by well to do men to accrue prestige.

The other sensitive aspect of the introduction of aquaculture is the public health aspect (discussed under output from extensive and semi-intensive aquaculture). Regardless of this, however, public health measures must be planned as an integral part of aquaculture development. Aquaculture development has the potential to increase human health hazards primarily from water borne diseases (schistosomiasis, malaria and guinea worm/and fish parasites). Schistosomiasis and malaria may perhaps be the most prevalent disease among major aquaculture zones in Nigeria.


SUSTAINABLE NIGERIAN AQUACULTURE Nigerian aquaculture development must be socially equitable, environmentally compatible, and have sufficient diversity and scope for change, to adopt to ever changing conditions, considering the fact that our natural environment presents still unresolved problems for food security, which together with civil strife, unstable economy, tribal wars, general poverty and lack of skilled personnel have caused a decline in food production per caput and shortfall in local supplies. Intensive aquaculture usually poses much greater threats to the environment than do the extensive and semi-intensive aquaculture. Intensive fish farm are heavy users of feed (above 50 % of the total running cost), antibiotics, disinfectants and other theraputants, whose release into the natural ecosystem often cause considerable environmental degradation. Pollution by intensive aquaculture as have been assessed in this paper threatens the sustainability of intensive aquaculture. Example from the Milkfish pen aquaculture in Laguna de Bay, a shallow 90,000 ha eutrophic lake adjacent to Metropolitan Manila Philippines grew from a single experimental pen in 1970 to about 7, 000 ha of pens in 1974 producing a mean yield of about 7 ton/ha/year (Pullin, 1981). Pullin (1981) reported that although its expansion phase was a ‘gold rush’, in which the pen owners got richer and the lakes small-scales fisheries and aquaculturist suffered greatly. The decline has been because of conflicts, losses due to typhoons and the reduction in the lake productivity attributed to pollution and altered flushing patterns due to flood control structures. This was a non-sustainable, socially inequitable and environmentally unfriendly development and one not to emulate.


134

Small-scale semi intensive/extensive aquaculture operations are socially and environmentally desirable. In traditional Nigerian agriculture, the bulk of food production lies with small-scale producers for the foreseeable future; this has good aquaculture implications vis-à-vis the utilization of on farm by-products as energy input in semi-intensive aquacultural systems. Small scale is a term synonymous with operations run by an individual, family or village community group. The aquaculture system best suited to small-scale producers is low-input systems. Pullin (1989) reported that small-scale, semi-intensive aquaculture systems particularly those integrated with agriculture are less environmentally disruptive that larger or more intensive systems. In the Cross River and Anambra River basins cashment area of Nigeria, aquacultural practices are mostly integrated semi-intensive and extensive. The diverse farming systems practiced in these areas permits the coexistence of agriculture, aquaculture, animal husbandry, wildlife and forestry.

In terms of management, small-scale semi-intensive and extensive aquaculture are easy to manage and economically less expensive considering the socio-economic restrictions in Nigeria. Furthermore, polyculture of various fish species may be desirable considering the exploitation of all possible trophic and adhafic niches of the pond ecosystem. Culturable fish species may either be carnivorous or herbivorous. Carnivorous species are desirable in semi-intensive polyculture with high fecund herbivore e.g. Tilapia among others. Additionally, the cultures of herbivorous species like Disticodus species among others are strongly desirable in both semi-intensive monocultures than carnivorous candidates.

It is worthy to mention that the opportunities for and needs of rural producers and consumers, urban consumers must be considered while developing an


aquaculture facility, since all kinds of aquaculture, small to large-scale and extensive to intensive monoculture-polyculture and enhanced fisheries, can make sense in developing country aquaculture depending upon the needs of different sections of the community, of which the semi-intensive and extensive aquacultural practices as highlighted above are sustainable in Nigeria.

Furthermore, in Nigeria, aquaculture developments are viewed as both an option for livelihood as well as meet nutritional need (animal protein security). Thus one must avoid the naïve assumption that aquaculture ‘must’ be able to fill the shortfall in fish supply or close the protein gap. As fish is only less than 20 % of the protein sources, expansion of fish supply through aquaculture must be weighed against the pros and cons of increased supply of plant and other animal proteins through agronomy and animal husbandry. CONCLUSION In Nigeria aquaculture development is needed to help alleviate poverty, provide livelihood and improve protein security. Aquaculture development must complement agronomy and animal husbandry in the light of protein security, and must be in harmony with realistic environmental conservation objectives, with transnational cooperation, efficient management and effective legislations. Above all aquaculture must be seen in the below context of (1) national development and sustainability (2) its environmental and socio-economic relationships to alternative sources of protein supply (3) its effect on the abiotic and biotic components of the environment (4) the possibilities of integration with other farming systems, (5) adaptive research infrastructure development and


136

extension to ensure further developments and sustainability (6) its impact on public health and (7) genetic conservation of the fish stock among others. REFERENCES Alabaster, J. S. (1981). Review of the state of aquatic

pollution of East Africa inland waters. Committee for Inland Fisheries of Africa. CIFA Occasional Papers, 9: 36 pp.

Alabaster, J. S. (1982). Report of the EIFAC workshop on fish-farm effluents. EIFAC Technical Paper, Number41: FAO Rome.

t r

Anon. (1988). Marine fish farming in Scotland: a discussion paper. Scottish Wildlife and Countryside Link. Perth. Scotland. 70 pp.

Austin, B. (1985). Antibiotic pollution from fish farms: effects on aquatic micro-flora. Microbial Sciences, 2: 113 – 117.

Bergheim, A., Hustvoit, H. and Selmer-Olsen, A. (1982). Estimated pollution loadings from Norwegian fish farms. 11. Investigations 1980 – 1981. Aquaculture, 36: 157 – 168.

Berveridge, M. C. M. (1984). Cage and pen fish farming. Carrying capacity, models and environmental impact. FAO Fisheries Technical Paper, 255: 131 pp.

Beveridge, M. C. M. and Philips, M. J. (1993). Environmental impact of tropical inland aquaculture. Pages 213 – 236. In: R. S. V. Pullin, H. Rosenthal and J. L. Maclean (Eds.) Environment and aquacul ure in developing countries. ICLARMConference P oceedings, 31: 359 pp.

Beveridge, M. C. M., Phillips, M. J. and Clarks, R. M. (1991). A quantitative and qualitative assessment


of wastes from aquatic animal production, Pages 506 – 533. In: D. E. Brune and J. R. Tomasso (Eds.). Advances in world aquaculture. Volume 3. World Aquaculture Society, New York.

Boyd, C. E. (1978). Effluents from catfish ponds during harvest. Journal of Environmental Quality, 7: 59 – 62.

Boyd, C. E. (1979). Water quality in warm water fish ponds. Auburn University, Alabama.

Bruton, M. N. (1986). The life history styles of invasive fishes in Southern Africa. Pages 201 – 208. In: I. A. W. Macdonald, F. J. Kruger and A. A. Ferrar (Eds.). The ecology and management of biological invasions in Southern Africa. Oxford University Press, Cape Town.

Calamari, D. (1985). Review of the state of aquatic pollution of West and Central Africa inland waters. Committee for Inland Fisheries of Africa. CIFA Occasional Papers, 12: 26 pp.

CIFA (1987). Report of the first session of the working party on pollution and fisheries, 16 – 20 June 1986, Accra, Ghana. Committee on Inland Fisheries for Africa. FIRI/R 369, (En). FAO Fisheries Report, 369: 33 pp.

Edwards, P. (1985). Aquaculture: a component of low cost sanitation technology. The World Bank, Washington DC. World Bank Technical Paper, 36: 78 pp.

Edwards, P., Pullin, R. S. V. and Gardner, J. A. (1988). Research and education for the development of integrated crop-livestock-fish farming systems in the tropics. ICLARM Study Review, 16: 53 pp.

Ellis, J. T. (1974). A review of the literature on the use of masoten in fisheries. US Fish and Wildlife Service, Washington DC.


138

Jayasinghe, J. M. P. K. and Desilva, J. A. (1990). Impact of prawn culture development on the present lead use pattern in the coastal areas of Sri Lanka. PaperPresented at the Symposium on Ecology and Land Scape Management of S i Lanka, June 1990 Colombo, Sri Lanka. 32 pp.

r ,

Johannes, R. E. (1975). Exploitation and degradation of shallow marine food resources in Oceania Pages 41-71. In: R. W. Force and B. Bishop (Eds.). The impact of urban centers in the Pacific. Pacific Science Association, Honolulu.

Kilambi, R. V., Hoffman, C. E., Brown, A. V., Adams, J. C. and Wickizer, W. A. (1976). Effects of cage culture fish production upon the biotic and abiotic environment of Crystal lake, Arkansas. Final Report to the Arkansas Game and Fisheries Commission and the US Department of Commerce, Department of Zoology, University of Arkansas, Fayetteville, Arkansas.

King, H. R. (1993). Aquaculture development and environmental issues in Africa. Pages 116 – 124. In: R. S. V. Pullin, H. Rosenthal and J. L. Maclean (Eds.) Environment and aquaculture in developing countries. ICIARM Conference Proceedings, 31: 359 pp.

Kodama, M. (1990). Possible links between bacteria and toxin production in algal blooms. Pages 52 – 61. In: E Graneli, B. Sundstrom, L. Elder and D. M. Anderson (Eds.). Toxic marine phytoplankton. Elsevier, New York.

Maclean, J. L. (1989) Red tides in Papua New Guinea waters. Pages 27 – 38. In: G. M. Hallegraeff and J. L. Maclean (eds.) Biology, epidemiology of Pyrodinium red tides. ICLARM Conference Proceedings, 21: 286 pp.


Michel, C. (1986). Practical value, potential dangers and methods of using antibacterial drugs in fish. Rev. Sci. Tech. Off. Int. Epiz. 5: 659 – 675.

Millar, S. (1984). Antibio ic residue study in rainbow trout and tilapia. MI Biology Thesis, Napier College of Commerce and Technology, Edinburgh. 60 pp.

t

t

f

t

Munro, K. A., Sumis, S. C. and Naissichuk. M. D. (1985). The effects of hatchery effluents on water chemistry, periphyton, and benthic invertebrates of selected British Columbia streams. Canadian Fisheries and Aquatic Science, Ms Report 1830: 147 pp.

NCC (1991). Fish farming and the Scottish freshwater environment. Report prepared for the Nature Conservancy Council by the Institu e of Aquaculture, University of Stirling: Institute of freshwater Ecology, Penisuik; and the Institute o Terrestrial Ecology, Banchory. Nature Conservancy Council, Edinburgh. 283 pp.

Parry, G. D., Langdon, J. S. and Huisman, J. M. (1989). Toxic effects of a bloom of the diatom Rhizosolenia chunii on shellfish in port Phillip Bay, Southeastern Australia. Marine Biology, 102: 25 – 41.

Pauly, D., Acere, T. O. and Vincke, M. (1989). On researchand aquacul ure in Africa. Report of a mission to assess the fisheries research needs of Kenya, Malawi, Mozambique and Zimbabwe. Study on International Fisheries Research. The World Bank, Washington DC.

Philips, M. J., Beveridge, M. C. M. and Ross. L. G. (1985). The environmental impact of salmonid cage culture in inland fisheries: present status and nature trends. Journal Fish Biology, 27: 123 – 137.

Philips, M. J., Beveridge, M. C. M. Stewart. J. A. (1986). The environmental impact of cage culture on


140

Scottish freshwaters. Pages 504 – 508. In: J. F. de L. G. Solbe (ed.) Effects of land use on freshwaters. Ellis Harwood Limited, Chichester.

Pullin, R. S. V. (1981). Fish pens of Laguna de Bay, Philippines. ICLARM Newsletter, 4(4): 11-13.

Pullin, R. S. V. (1989). Third-world aquaculture and the environment. Naga, ICLARM Quarterly, 12(1): 10-13.

Pullin, R. S. V. (1993). An overview of environmental issues in developing country Aquaculture, Pages 1 – 19. In: R. S. V. Pullin, H. Rosenthal and J. L. Maclean (Eds.) Environment and aquaculture in developing countries. ICIARM Conference Proceedings, 31: 359 pp.

Rasmussen, P. (1988). Therapeutants used in fish production: Pharmacokinetics, residues and withdrawal periods EIFAC/XV/88/Inf., 13: 25 pp.

Rast, W., Holland, M. and Ryding, S. O. (1980). Eutrophication management frame-work for the policy maker. MAB Digest 1. United Nations Educational Scientific and Cultural Organization, Paris. 83 pp.

Saitao, T., Noguchi, T., Takeuchi, T., Kamimura, S. and Hashimoto, K. (1985). Ichthyotoxicity of paralytic shellfish poison. Bulletin of Japanese Society for Science and Fisheries, 51: 257 – 260.

Saleh, A. S., Fouda, M. M., Saleh, M. A., Abdel-Hattif, M. S. and Wilson, B. L. (1988). Inorganic pollution of the man-made lake of Wadi El-Raiyan and its impact on aquaculture and wildlife of the surrounding Egyptian desert. Archives of Environmental Contamination and Toxicology, 17: 391 – 403.

Sarig, S. (1971). The prevention and treatment of diseases of warm water fishes under subtropical conditions,


with special emphasis on intensive fish farming. TFH Publications, Neptune City, New Jersey.

Satia, B. P. (1990). National reviews for Aquaculture Development in Africa: Nigeria. FAO Fisheries Circular, No 770: 29 – 193.

Shamsudin, M. N. (1986). Bacterial examination of fingerlings of bighead carp (Aristichtys nobulus) and grass carp (Ctenopharyngodon idella) imported into Malaysia, Pages 235 – 240. In: J. B. Maclean, L. B. Dizon and L. V. Hosillos (Eds.). The First Asian Fisheries Forums. Asian Fisheries Society, Manilla.

Shariff, M. (1989). Diseases of aquarium fishes and their treatment. Pages 67 – 81. In: F. M. Yusoff and K. T. Siow (Eds.). The proceedings of Aquarium Fish Industry - A New Frontier. Malaysian Fisheries Society, Johore Bahru, Malaysia.

Shunway, S. E., Barter, S. E., and Sherman-Caswell S. (1990). Auditing the impact of toxic algal blooms on oysters. Environmental Audi or, 2: 41 – 56. t

f

Simons, I. G. (1989). Land transformations during the period of pre-industrial agriculture. Outlook on Agriculture, 18: 85 – 91.

Skaala, O., Daale, G., Jorstad, K. E., and Naevdal, G. (1990). Interactions between natural and farmed fish populations: information from genetic makers. Journal o Fish Biology, 36: 44 – 460.

Stirling, E. P. and Dey, T. (1990). Impact of intensive cage fish farming on the periphyton and phytoplankton of a Scottish freshwater Loch. Hydrobilogia, 190: 193 – 214.

Welcome, R. L. (1988). International introductions of Inland aquatic species. FAO Fisheries Technical Paper, 294: 318 pp.

Whilde, T. (1990). Sharing the environment with the original inhabitants – some thoughts as


142

aquaculture and the environment. Pages 56 – 59. In P. Oliver and E. Colleran (Eds.). Interactions between aquaculture and the environment. A Taises: The National Trust for Ireland, Dublin.

White, A. W. (1988). Blooms of toxic algae worldwide, their affects on fish farming and shellfish resources. Pages 9 – 14. In: A. Jensen (Ed.). The impact of toxic algae on mariculture. Proceedings of Awuanor 87. Morske Fisheoppdretterss forening. Trondheim, Norway.

White, A. W., Fukuhaza, O. and Anraku, M. (1989). Mortality of fish larvae from eating toxic dinoflagellates or zooplankton containing dinoflagellate toxins. Pages 395 – 398. In: T. Okaichi, D. M. Anderson, and T. Nemoto (Eds.). Red tides, Biology environmental science and toxicology. Elsevier, New York.

Aquaculture and Environment · environment and aquaculture, management of aquaculture and the...

Documents

Transcript of Aquaculture and Environment · environment and aquaculture, management of aquaculture and the...