CHAPTER ONE 1.0 

 INTRODUCTION

1. 1 General Background of Research

Fish is one of the most diverse groups of animals known to man with more than 20,500 species in existence (Lagler et al.1977) as referenced by Eyo (2001).These species consist of  teleost or the bony fishes (20,000 species) and the elasmobranchii or cartilaginous fishes (500 species).  The bony fishes are of two types, the pelagic and demersals. The pelagic are the shoal moving fatty fishes such as sardines, mackerel, bonga, herring, tuna etc which move at the surface of the water bodies. The demersals dwell at the bottom of the water bodies with less than five percent fat in their tissues. Examples of demersals are cod, haddock and croakers amongst others.

 Fish is highly perishable especially in the tropical temperature and needs to be preserved for long term storage. Soon after harvest; the fish dies and begins to spoil. In a healthy fish, all the complex biochemical reactions are balanced and the fish flesh is sterile. After death however, irreversible changes begin to occur resulting in fish spoilage. The resultant effect is the decomposition of the fish (Akinola et al. 2006). A lot of factors are responsible for fish spoilage. Some of these factors are the fish health status, the presence of parasites, bruises, and wounds on the skin and mode by which fish was captured. The caught fish quality depends on the handling and preservation, the fish received from the hands of fishers after capture (Akinneye et al. 2007).The handling and preservation practice after capture affects the degree of the spoilage.  Wrong fishing method does not only cause mechanical damage to the fish but also creates stress and the conditions which accelerates fish deterioration after death (Okonta and Ekelemu, 2005). The less developed countries capture 50%   of the world’s  harvest and a large proportion of this is consumed internally (FAO,1999) as referenced by Eyo (2001) .In some Asian countries more than 50%   of the animal protein intake comes from fish whereas in Africa the proportion  is 17.5%  (Willman et al.1998). Here in Nigeria fish contributes about 40% of animal protein intake (Olatunde,1989) as referenced by Eyo (2001). The implication of this fact is that any shortfall in fish availability will affect the animal protein intake of people in tropical countries.

1.1.1 Importance of fish

The uses of fish are so enormous in practice such that it is enumerated as follows.

Use of fish as food

Fish has long been recognised as a healthy food in many countries of the World. Fish is one of the most abundant animal protein foods available in the tropics. It is also rich in minerals and essential fatty acids, vitamins A and D and rich in iodine. Above all man can digest it easily. In Southern part of the World, fish is an essential part of their nutrition often providing most, if not all their animal protein.  In the North too, fish is considered a healthy food choice and is therefore in demand. Appropriate processing of fish enables maximal use of raw material and production of value added products which is obviously the basis of processing profitability. The processing of fresh water fish like other food raw materials should ensure best possible quality; provide proper form of semi-processed final products. It should apply the most appropriate processing method and reduce wastes to the barest minimum

Fish for controlling diseases: Diseases like malaria, yellow fever and other dreadful diseases that are spread through mosquitoes can be controlled. Larvivorous fish eat larva of mosquito. The important larvivorous fish are Gambusia, Panchax, Haplochitus, Trichogaster, etc

Aesthetic value of fish: A large number of fishes are cultured in aquarium for their beauty and graceful movements. The important aquarium fish are Macropodus, Trichogaster, Carassinus (gold fish) and Pterophyllum (angel fish)

Fishery bye-products:

(a) Fish oil: The by-products obtained during the drying process include fish oil, which when taken, can help regulate cholesterol in the body. It can be extracted from the liver of the sharks, sawfishes, skates and rays and has medicinal value. These mainly include cod liver oil and shark liver oil .There is a wide variety of delicious dishes that can be prepared from dry fish.  Fish meal is a commercial product made from both whole fish and the bones and offal from processed fish. It can be used as protein concentrate animal feed. It is a brown powder or cake obtained by pressing the whole fish or fish trimmings to remove the fish oil. Fish emulsion is a special kind of coat that is produced as a by-product. Example is the fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and meal industrially. The emulsion is anti corrosive and has wide industrial usages as paints and coating.

(b) Fish manure: The fish waste after the extraction of oil, is used as fertilizers,

(c) Fish glue:  It is a sticky product, obtained from the skin of the cod and is used as gum.

(d) Isinglass: It is a gelatinous substance, obtained from the air bladder of perches, Indian Salmons and cat fish used in the preparation of special cement and in the clarification of wine and beer

(e) Shagreen: The skin of sharks and rays, which has pointed and sharp placoid scales are used in polishing the wood and other materials. It is also used for covering the jewellery boxes and swords,

(f) Leather: A highly durable type of leather is prepared from the skin of sharks and rays,

(g) Artificial pearls: The silvery boney scales of cypnmids (a type of fish) are used in the manufacture of artificial pearls especially in France.

h)Fish meal : Many fishes are dressed and cooked. Then they are dried. Fishes are made into fine powder. This is called fish meal. It is used by weak and convalescent people.

i) Fertilizers: The ‘fish waste’ materials have more calcium, protein, phosphorous and other substances. These materials are ground into powder. It is used as fertilizer to Grape gardens, Coffee and Tea plants.

Fish harvesting, handling and distribution provide livelihood for millions of people as well as providing foreign exchange earning to many countries. (Al-Jufaili and Opera, 2006).

 j) Employment: Development of fishing industry generates more employment opportu­nities.

k) Source of Income: The fishing industry has brought a lot of income to the farmers in particular and the country in general. Now we can talk about “Blue Revolution” (fish production) on the same lines as ‘Green Revolution’ (for producing enough food for all).

1.1.2 Importance of fish drying Drying basically dehydrates or removes the moisture from the fish. This action inhibits the growth of bacteria, mold, and yeast. It also slows down the enzyme action without deactivating them .This factor ensures that fish does not spoil easily and hence makes drying an effective fish preservation technique. Since drying removes water from the fish, the weight of the fish is also reduced. This makes the fish lighter and also shrinks in size.  

1.1.3 Importance of thin layer drying and pretreatment of fish with salt.

Thin layer drying is a process of drying of individual particles or grains of material which are fully exposed to the drying air. In thin layer drying, the product thickness is sufficiently small such that the air flow characteristics, humidity and temperature is considered uniform at a given section parallel to the product. The process is often divided into two periods of drying: (1) the constant drying rate period and (2) the falling drying rate period. Radiation, conduction or convection provides the energy needed for drying.

It has been observed that fish is a highly perishable food material especially when solar drying is considered. Since equilibrium moisture content is likely to be achieved in solar drying after several hours as compared to drying with firewood, natural gas or electricity, pre-treatment is often recommended. The pre-treatment with salt helps to preserve the quality of fish until equilibrium moisture content is achieved. The pre-treatment   is able to accomplish this task by decreasing water activity in the fish, inhibits the growth of micro organisms by drawing out water from their tissues through osmosis.

1.1.4 Importance of modeling

Modeling is a process of providing a representation of the construction and working of some system of interest. A model is often simpler than the system it represents. The main purpose of a model is to enable the analyst to predict the effect of changes to the system. A model should be a close approximation to the real system and incorporate most of the salient features.  It should be simple and easy to experiment. Simulation practitioners recommend increasing the complexity of a model iteratively. Simulation is a tool to evaluate the performance of existing or proposed model under different configurations of interest over long periods of real time. A simulation of a system is the operation of a model of the system. Model can be reconfigured and experimented with, usually this is impossible, too expensive or impractical to do in the real system it represents.

1. 1. This material content is developed to serve as a GUIDE for students to conduct academic research work
2. 2. As a source for additional understanding of the subject.
3. 3. As a source for ideas for your own research work (if properly referenced).
4. 4. For PROPER paraphrasing (see your university definition of plagiarism and acceptable paraphrase)
5. 5. Direct citing (if referenced properly)
Thank you so much for your respect to the authors copyright.