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Full Project – Isolation and identification of helminthes parasites of public health importance from commercial aquaculture ponds water

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CHAPTER ONE

INTRODUCTION

1.1 Parasitic Diseases of Fishes

A great number and diversity of animal species are capable of parasitizing fish, ranging from microscopic protozoan to grossly visible crustaceans and annelids. In the wild fish, there is large range of parasites but they are usually only present in small numbers, they can be considered a normal finding and rarely cause disease problems (FAO, 2016).

In cultured fish, there is a more limited range of parasites but they are often present in much large numbers than seen in the wild. There is always a risk of parasitic epizootic in farmed fish and these increases with intensified of the fish farming system.

The major parasitic diseases which afflict fish are caused by Protozoa, Monogenean trematodes, Digenean trematodes, Nematodes, Cestodes, Parasitic Crustaceans, and Leeches (FAO, 2016)

1.2 AQUACULTURE

Aquaculture is the farming of fish, crustaceans mollusks, aquatic plants, algae and other organisms. Aquaculture involves cultivating freshwater and salt water populations under controlled conditions, and can be compared with commercial fishing, which is the

harvesting of wild fish (Garner, 2016). Mari culture refers to aquaculture practiced in marine environments and in underwater habitat.

Farming involves some form of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Farming also includes individual or corporate ownership of the stock being cultivated. The reported output from global aquaculture operations in 2014 supplied over one half of fish and shellfish that is directly consumed by humans (FAO, 2016). However, there are issues about the reliability of the reported figures.

Particular kinds of aquaculture include fish farming, shrimp farming, oyster farming, marine-culture, alga-culture (such as seaweed farming), and the cultivation of ornamental fish. The farming of fish is the most common form of aquaculture. It involves raising fish commercially in tanks, fish ponds or ocean enclosure, usually for food. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species natural number is generally referred to as a fish hatchery. Worldwide, the most important fish species used in fish farming are in orders carp, salmon, tilapia and catfish (FAO, 2016).

1.2.1 FISH FARMING

Fish farming or pisciculture involve the rising of fish commercially in tanks or enclosures such as fish ponds usually for food. It is the principal form of aquaculture, while other methods may fall under mar culture. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species natural numbers is generally referred to as fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, tilapia, salmon, and catfish (FAO, 2014).Demand is increasing for fish and fish protein, which has resulted in widespread overfishing in wild fisheries. Farming carnivores’ fish such as salmon does not always reduce pressure on wild fisheries. Carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by FAO totaled 33.8 million tons worth about $US 60 billion (2016).

1.2.3 EXTENSIVE AQUACULTURE

Growth is limited by available food, commonly zooplanktons feeding on pelagic algae or benthic animals, such as mollusks. Tilapia filter feed directly on phytoplankton, which make higher production possible. Photosynthetic production can be increased by fertilizing pond water with artificial fertilizers mixtures, such as potash, phosphorous, nitrogen, and micro elements. Another issue is risk of algal blooms. When temperatures, nutrients supply, and available sunlight are optimal for algal growth, multiply at an exponential rate, eventually exhausting nutrients and causing a subsequent die off in fish. The decaying algal biomass depletes the oxygen in the pond water because it blocks out the sun and pollutes it with organic and inorganic solutes (such as ammonium ions), which can (and frequently do) lead to massive loss of fish.

1.2.4 INTENSIVE AQUACULTURE

In these kinds of systems fish production per unit of surface can be increased as long as sufficient oxygen, fresh water and food are provided. Because of the requirement of sufficient fresh water, a massive water purification system must be integrated in the fish farm. One way to achieve this is to combine hydroponic horticulture and water treatment. Fish do not use energy to keep warm, eliminating some carbohydrates and fats in the diet, required to provide this energy. This may be offset, though obtained, by the lower land costs and the higher production which can be due to the high level of input control.

Aeration of water is essential, as fish need a sufficient oxygen level for growth. This is achieved by bubbling, cascade floe, or aqueous oxygen. Clarias spp. can breathe atmospheric air and can tolerate much higher levels of pollutant than trout or salmon, which makes aeration and water purification less necessary and makes Clarias species especially suited for intensive fish production. In some clarias farms, about 10% of water volume can consist of fish biomass. The risk of infections by parasites such as fish lice, fungi (saprolegnia spp.), intestinal worms (such as nematodes or trematodes), bacteria (e.g. Yersinia spp., Pseudomonas spp.), and protozoa (such as dinoflagellates) is similar to that in animal husbandry, especially at high population densities (Weaver et.al, 2006). However, animal husbandry is a larger and more technologically mature area of human agriculture and has developed better solutions to pathogens problems. Intensive aquaculture has to provide adequate water quality (oxygen, ammonia, nitrate, etc.) levels to minimize stress on the fish. This requirement makes control of the pathogen problem more difficult. Intensive aquaculture requires tight monitoring and a high level of expertise of the fish farmer. Very high intensity re cycle aquaculture systems (RAS), where all the production parameters are controlled, are being used for high value species. By recycling water, little is used per unit of production. However, the process has high capital and operating costs. The higher the cost structures mean that RAS is economical only for high value products such as brood stock for egg production, fingerlings for net pen aquaculture operations, research animals, and some special markets such as live fish (Avnimelech, 1994).

1.3 FISH FARMS

Within the intensive and extensive aquaculture methods , numerous specific types of fish farms are used; each has benefits and applications unique to its design.

1.3.1 Cage System

Fish cages are placed in lakes, bayous, ponds, rivers, or oceans to contain and protect fish until they can be harvested. The method is also called “off shore cultivation” when the cages are placed in the sea. They can be constructed of a wide variety of component. Fish are stocked in cages, artificially fed, and harvested when they reached market size (Mayer, 2011). A few advantages of fish farming with cages are that many types of waters can be used (rivers, lakes, filled quarries, etc.), many types of fish can be raised and farming can co exist with sport fishing and other water uses.

Cage farming of fishes in open seas is also gaining popularity. Given concerns of diseases, poaching, poor water quality, etc., generally pond systems are considered more simple to start and easier to manage. Also, past occurrences of cage failures leading to escapes, have raised concern regarding the culture of no native fish species in dam or open water cages.

1.4 PUBLIC HEALTH ISSUES

Several parasites found in fish can infect humans as non traditional hosts. The mode of entry into humans is by ingestion of raw or undercooked infected fish. Proper cooking or freezing prevents transmission of ingested human pathogenic parasites. Some parasites are found only in tropical regions. The prevalence and importance of parasitic infections vary markedly and depend on local risk factors and conditions.

Health hazards resulting from trematode parasites in cultured fish exist primarily in South-East Asia (Lima et.al, 1995). According to World Health Organization Officials, food borne trematode infections are a major public health and are endemic in twenty countries, affecting millions of people. However, the extent of the problem as associated directly with farm-raised fish is undetermined. Another nematode of the genus Eustrongyloides has been acquired by persons consuming estuarine fish. Some other fish –borne parasites which can affect humans are the tapeworms Diphyllobothrium spp., Digrammabrauni, and Liguna intestinalis and the trematodes clonorchis sinensis, Opisthorchis spp., Heterophytes spp., Metagonmus spp. and Diorchitrema spp. (Durborow, 1997). Crustaceans are vectors of trematodes of the genus Paragonimus spp. which mature in human lungs. Bivalve mollusks may be vectors for human protozoa such as Giardia lamblia or Cryptosporidium parvum (Bier, 1990).

1.5 Justification of study

Although for the majority of poor people, fish production is in high demand to supplement other food sources which are dwindling with the vagaries of weather. It is a well known fact that animal maintained under crowed conditions are more susceptible to parasitic infections and disease, as this is true of mammals as well as both fin and shell fish populations (Perkins and Cheng, 1990).Parasitic infections of fishes can be a major setback in achieving production per unit area of culture. In other to achieve some millennium development goals on poverty and hunger, information is needed on fish infections so that strategies can be devised to fight these enemies of man which compete for the mean resources.

1.6 Aim

To isolate and identify parasitic protozoan in commercial aquaculture ponds within some selected local governments in kano.

1.7 Objectives

To determine the physico- chemical properties of water in fish pond

To identify parasites occurring in fish ponds

To determine the abundance of parasites in commercial fish pond water

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