Economic Importance of Fish and Fish Products

February 16, 2023 Globalinfo247

There are so many economic importance of fish and fish products to mankind which we will be discussing about today but first, Fish can literally be defined as a scaly skinned vertebrate that flaps its tail to swim through water and breathes using gills. Most fish have a skeleton made from bone, just like amphibians, reptiles, birds, and mammals. But sharks and rays have skeletons made of a softer, rubbery substance called cartilage.

Aside being part of our everyday delicacies due to its nutritional profile, fish also serves as great source of income as fish farming business without any doubt is one of the highly lucrative businesses to venture into in animal production.

Therefore it is important for us to that fishes are one of the most important group of vertebrates serving as food for human. They possess a great economic, nutritional, medicinal, industrial, aesthetic and religious values as well as providing employment for millions of people in the world.

They contribute to food security in many regions of the world, providing a valuable supplement for diversified and nutritious diets. Consumption of fish has so many health, nutritional, environmental and social advantages over other terrestrial animal meat. The importance of fishes can be discussed under the following headings.

Meanwhile, the above mentioned reasons are not the only benefits of fish and fish products which is why today we will be focusing on the detailed economic importance of fish and fish products.

Below are the amazing importance of fish and products that can be gotten from fish (fish products):

List of Fish Products

1) Fish meal

The dried and ground preparation of unused or trash fish is called fish meal and is a highly nutritive product that makes an excellent feed for poultry, pig, cattle and fish.

Fish meal contains about 60-70% crude protein, 2-15% oil and 10-20% minerals. The protein of fish meal is highly digestible and contains all amino acids. It is also very rich in vitamins, calcium, phosphorous and iodine.

2) Fish oil

Fish oil is of two kinds, body oil and liver oil. The oil extracted from the whole body of the fish is called fish body oil. For the extraction of body oil, the fishes are minced, steamed, and then pressed for oil recovery, then subject to filter for refine. It is very rich in iodine.

The fish body oil is mostly used in manufacture of paints, varnishes, soaps, lubricants, candle, printing inks, etc. It is also used in dressing of leather, tanning of skin and smearing the surface of boats for longer preservation.

The oil obtained from the liver of fishes is called fish liver oil. For the extraction of liver oil, livers are chopped and boiled in water. The oil is then skimmed out from the surface of the water and purified.

Fish liver oil has medicinal value. It contains 55-75% fat and 5-10% protein. It is very rich in Vitamin A and D. Shark (Carcharhinus spp.) and Cod (Gadus callarius) liver oil are well known in pharmaceutical industries.

3) Fish silage

Fish silage is a liquid or semi-liquid product made from whole or part of the fish that are liquefied by the action of enzymes in the fish in the presence of an added acid (Hydrochloric or Sulfuric acid).

The enzymes break down fish proteins into smaller soluble units, and the acid helps to speed up their activity while preventing bacterial spoilage. It is a highly nutritive animal feed. It contains about 15% protein; however, the composition of fish silage depends on the fish species from which it is made.

4) Fish flour

Fish flour is made up of dried and powdered fish. It is a superior quality of fish meal which is used for human consumption. It is considered an ideal protein source to supplement diet. It can be mixed with wheat or maize flour and used for enriching the nutritive value of bread, biscuits, cakes, etc. It is also known as hydrolyzed protein of fish.

5) Fish manure and guano

Low grade, un-edible fish and offal from the fish-canning factories, fish-salting plants, fish-filleting plants and other fish processing industries are utilized to prepare the fish manure. These residues are dried, ground, mixed with ash and converted into manure, which contains a high percentage of nitrogen and phosphorous.

The word ‘guana’ means dung in Spanish language. Fish guano is prepared from the material left over after extracting oil from the fish. It has high content of nitrogen (8-10%), and has been found more effective than animal manure.

Read Also: 8 Uses of Fish and Fish Products

6) Fish glue

The gelatinous adhesive material obtained from the connective tissues of skin and bones of certain fish, principally cod fish, is called fish glue. It is used in gummed tape, letterpress printing plates, blueprint paper and adhering the wood, leather, glass, etc.

7) Isinglass

Isinglass is a substance obtained from the dried swim bladders of fish. It is a high-grade collagen used mainly for the clarification of wine, beer and vinegar. It can also be cooked into a paste for specialized gluing purposes.

For making isinglass, the air bladder is removed from the fish, washed thoroughly and flattened by beating. The beaten pieces are then dried for the preparation of isinglass. It is in the form of shiny powder. Isinglass is generally made from sturgeon and cod fish.

8) Fish leather

The coarse scaly skins of several fishes (e.g., sharks and rays) are used for manufacturing, polishing and smoothing materials in place of sand paper. The dried and processed skin is also used for preparing high-quality shoes, moneybags, suitcases, belts, phone cases, etc. Fish leather is an eco-friendly alternative to the typical exotic leathers such as crocodile and snake that threaten endangered species.

The production of fish leather is a long and complicated process. For this purpose, skins from larger fish is collected and soaked in brine for a day then salted and again put in brine containing 10% hydrochloric acid.

After that, skin is scraped on the surface and tanned by usual process. Actually, the exact details of the process are a closely guarded secret as only few manufacturers in the world are able to make it to a high standard after years of experimentation and fine-tuning.

9) Fish fin

The fins of the sharks and rays are used to make tasteful sauce and soups. It is a popular soup item of Chinese cuisine usually served at special occasions such as weddings and banquets, or as a luxury item in Chinese culture.

10) Fish caviar

Caviar is a high value fish product. It is a salt-cured eggs of certain species of fish such as sturgeon, salmon and trout. Traditionally the term caviar refers only to the eggs from some species of wild sturgeon in the Caspian and Black Sea.

Depending on the country, caviar may also be used to describe the eggs of other fish such as salmon, trout, lumpfish and whitefish. Caviar is considered a delicacy and luxurious food and is eaten as a garnish or a spread.

For preparation of caviar, ovaries are first removed from the sedated female sturgeon and passed through a sieve to remove the membrane. Then the eggs are rinsed to wash away impurities. The eggs are then ready to become caviar by adding a precise amount of salt for taste and conservation.

The fresh preparation is tasted and graded according to quality. Finally, the shiny eggs are packed into lacquer lined tins that will be further processed or sold directly to customers. It can be sold as fresh (non-pasteurized) or pasteurized, with pasteurization reducing its culinary and economic value.

The price of caviar generally depends on age and species of the fish. For example, caviar of 60 to 100 years old Iranian beluga sturgeon costs about $35,000/kg. Caviar from salmon and trout are cheaper.

11) Fish pearls

The material obtained by scraping the silvery coating of the scales of certain fishes is used for polishing the hollow glass beds. These beds are then filled with wax and marketed as artificial pearls which are used as jewelry.

12) Fish insulin

Insulin is extracted from the pancreas of large sized fishes such as sharks. Prior to the introduction of biosynthetic insulin, insulin derived from sharks and other fishes was extensively used for glycemic control in human.

You can read more about the different products of fish (fish products) by clicking on the link below:

Now going back to the economic importance of fish and fish products as our main topic of the day, below are the economic importance of fish and fish products to mankind.

The Economic Importance of Fish and Fish Products

1) Importance of Fish: Fish as Food

Fishes are consumed everyday by man, they are rich in protein and are delicious to taste. The protein in fish and shellfish is very easy to digest and research shows that the amino acids in fish are more bioavailable (your body can absorb and use them more readily) than beef, pork or chicken.

Fish and shellfish also have a balanced quantity of all of the essential amino acids, giving them very high Amino Acid Scores.

2) Importance of Fish: Fishes are Medicinal

It has been discovered that the consumption of fish can help to prevent various types of cancers, cardio-vascular diseases, skin, and hair problems, and they also help in keeping the brain stimulated. In traditional Chinese medicine, Sea horse, star fish, sea urchin and sea cucumber are used.

Fish can also assist in controlling diseases like malaria, yellow fever and other dreadful diseases that are spread through mosquitoes. For example, the Larvivorous fish eat larva of mosquito and the important larvivorous fish are Gambusia, Panchax, Haplochitus, Trichogaster.

(1) The pancreas of shark is very rich in insulin. Whales also provide a considerable quantity of insulin. Fish replaces catties in providing raw material for the manufacture of insulin.

(2) The large otoliths of Sciaenids are removed from the head and after rubbing and mixing them with water, are given to convalescent children suffering from rickets.

(3) Amphipnous cuchia has been considered by fisher folks as a highly medicinal fish. As soon as the fish is caught, gram flour (besan) or wheat flour is rubbed on its body, so as to wipe out all the mucous. The flour with mucous is then made into small balls and then dried. Such balls (tablets) are prescribed to the persons suffering from impotency. It has been claimed that such persons soon regain their vigour and strength.

(4) Live fishes such as Clarias batrachus, Heteropneustes fossilis and Channa sp. are valued for their high nutritive and medicinal properties.

(5) Sillago sihama is considered good and nourishing for nursing mothers.

3) Importance of Fish: Fish Fertilizer/Emulsion

Fish emulsion is a fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and fish meal industrially.

4) Importance of Fish: Fish as a Source of Employment

Most farmers engage in the raising of fishes. They feed their families and pay their workers from the money realized after selling their fishes. The fish farmers use that as their own job, some specialize in catching fishes form the rivers, seas, oceans, lakes etc while others specialize in smoking, processing, freezing and packaging of the fishes.

Some farmers raise the fishes in the pond and sell them after they grow.

5) Importance of Fish: Fish as a Source of Income

The money realized from the sales of the fishes by the farmer becomes his/her income after sales because of this, fish also serves as a source of income not only to the farmer but also to his or her workers whom he pays for their services being rendered to the farm.

6) Importance of Fish: Fishes as Source of Oil

Fish oil is oil derived from the tissues of oily fish which contains the omega-3 fatty acids.

Fish liver oil is one of the most important by-products of fish. Liver, which is a part of the offal discard during dressing of landed fish, is the storehouse of glycogen and fat along with Vitamins A and D.

This property of fish livers of certain fishes like Cod, Shark, Ray, Halibut, Tuna, etc. has rendered it of immense commercial value of providing highly medicinal ‘liver oil’.

(a) Composition of fish liver oil:

Water — 20% to 36%

Proteins — 5% to 10%

Fats — 55% to 75% (Unsaturated fatty acids higher in concentration than saturated ones).

As fat carries with it high concentration of Vitamins A and D, the fat of fish liver is the source of vitamins A and D rich liver oil. However, the concentration of vitamin A and fat in the liver varies from fish to fish and from season to season.

Halibut (Psettodes sp.) and tuna (Thunnus sp.) liver have low fat but high vitamin A content (50,000 to 3,00,0001.U. per gram), while cod (Gadus sp.) liver is rich in fat but poor in vitamin A (1000-3000 I.U. per gram).

Vitamins A and D present in fish liver oil is in proportion most suitable for human needs, as it has medicinal use in the form of prophylactic and curative.

(b) Method of extraction of fish liver oil:

For extraction of quality liver oil it is essential that the liver of fishes be in good condition (either fresh or properly preserved). This is to guard the protein and fat rather than vitamin A content which is very stable.

Depending upon the method of extraction used, fish liver oils are of the following grades:

(1) Crude oil used for burning,

(2) High quality technical grade oil,

(3) Intermediate grade oil, and

(4) Edible oil for medicinal use.

The first three grades of oil are produced from diseased or discoloured livers while the last one is produced from fresh or suitably preserved livers.

(i) Oil extraction:

Some popularly used methods of oil extraction are given below:

(1) By autofermentation:

Fish livers are first chopped into small pieces and exposed to sun in earthen pots for several days, so that it undergoes decomposition. As it undergoes decomposition, the oil that is released is collected. This oil is crude and used for burning lamps in curing yards.

(2) By boiling:

Chopped livers are boiled with sufficient quantity of water. The released oil is then decanted off easily. Although this method is simple, the yield, however, is moderate as all the oil is not extracted from liver. This method is generally followed in small scale industries.

(3) By steaming:

Minced livers of fishes such as cod (which has high oil content) are steamed at a temperature of 85-90°C under a pressure of 2 kg/sq. cm. The liver cells disintegrate and the oil is collected from the top layer. This method is good for operation while on board of fishing vessels or trawlers, where steam is readily available.

(4) By chemical digestion:

Chemical digestion is done by the following three methods:

Aquacide digestion:

Aquacide is a patented mixture of sodium bicarbonate and paraldehyde. When fresh liver is mixed with it, it partly denatures the protein and yields a pulp. The pulp is stirred with warm water as it is passed through a series of tanks or cylinders. This gives rise to an emulsion of water and released oil. As soon as the emulsion breaks, the oil floats on the top from where it is collected.

Alkali digestion:

Digestion of proteins in the liver with alkali has proved to be the most successful method. The livers of halibut, tuna and some sharks, which are relatively poor in oil but high in vitamin A potency, are processed in this manner. In this case, the oil is held strongly by proteins and is not totally released by steaming or boiling.

Minced liver is mixed with dilute caustic soda (1-2% by weight) or sodium bicarbonate (2-5% by weight). It is then steamed at 82-88°C with constant stirring. The pulp is then centrifuged and the supernatant oil is collected.

Enzyme-alkali digestion:

This chemical digestion is a modified version of the above, where alkali (sodium bicarbonate) is added after the chopped liver is treated with an enzyme (pepsin). As pepsin acts best in an acidic medium, HC1 is added to the mixture.

At first the chopped liver is brought to pH level of 1.2 to 1.5 by the addition of HCl. Then commercial pepsin (0.5% by weight of the liver) is mixed with the pulp and digested at 43-49°C. The pH is then raised to about 9.0 by the addition of sodium bicarbonate and the temperature is increased to 80°C. After complete digestion, the oil that has gathered at the top is collected.

(5) By solvent extraction:

This is an advanced and expensive process although the yield is higher. This involves solvent extraction plant/equipment and solvents, like ethylene dichloride, solvent ether, chloroform, light petroleum, etc.

In this method, at first the minced liver is dehydrated with the application of an anhydrous salt, generally sodium sulphate. When the moisture has been removed, the pulp thus formed is mixed with the solvent (preferably ethylene dichloride) and put to extraction process.

After distillation the oil is separated out. Any free fatty acid present in the liver is removed during refinement of the oil. The solvent extracted oil is darker in colour and has a higher viscosity.

(ii) Refinement of liver oil:

The oil after collection from the above methods is left to stand, so that water and any particulate matter present in it settles down. Oil is then removed from the top and is subjected to filtration, centrifuging, or treatment with Fuller’s earth. The oil that is obtained is congealing oil.

It has stearine (triglyceride of stearic acid) present in it. Destearinated or non-congealing oil is obtained by separating stearine, which is done by cooling the oil slowly to 10°C. The oil, thus obtained, is again filtered in a chill room.

(iii) Standardisation of vitamin A potency in the extracted oil:

Due to its richness in vitamin A content, the liver oil has immense medicinal value.

For commercial purposes, it is thus subjected to standardisation of vitamin A potency by the following methods:

1. Biological estimation:

By this method standardisation is done by feeding the refined oil to 5 weeks old albino rats which are raised on vitamin A deficient diet. The response in growth is then matched with the growth rates of rats grown on known potency of vitamin A.

2. Colorimetric estimation with tintometer:

In this method the oil is dissolved in chloroform and then to it antimony trichloride is added. A blue colour develops and the intensity of this colour is read on a tintometer. The vitamin A potency is thus determined.

3. Photoelectric spectrophotometry estimation:

In this method the principle of characteristic and selective absorption of a certain zone of ultraviolet region of the spectrum is used. For this, the extracted oil is first dissolved in a suitable solvent and the solution is kept in the path of ultra violet rays. The intensity of absorption is measured with photoelectric unit and can be read on its galvanometer.

(c) Uses of fish liver oil:

Fish liver oil has the following uses:

(1) Crude liver oil is used for burning purposes or making lights in curing yards by fishermen.

(2) Fish liver oil because of its high vitamin A and D contents can cure or prevent occurrence of disease caused by the deficiency in the body of these two vitamins, such as rickets, xeropthalmia, impaired vision and eye defects, abnormalities of skin, mucous membranes and vertebrae.

(3) When taken orally it will ensure good growth of bone and teeth and will develop more resistance to counter bacterial attack.

(4) The stearin obtained by chi I ling the oil is used to make soaps of inferior grade and in leather curing.

(5) Inferior pharmaceutical grades are used in animal and poultry feeds.

(6) The volatile fraction of the liver oil, distilled at 250°C is toxic to bacteria and fungi.

(7) Alkoxyglycerol present in shark liver oil provides a unique immune supporting nutritional effect.

(8) Squalene present in certain shark liver oil as a constituent of the unsaponifiable fraction of fish oil, is used as a mordant in the dyeing of synthetic fibres.

(9) Lecithin, present in high concentration in dogfish liver oil (and in the oil of fish eggs) is used as a wetting and an anti-bloom agent in the chocolate industry.

7) Importance of Fish: Fish Used to Produce Body Oil

Fish body oil is one of the importance of fish and fish products, Fish body oil is the oil obtained from the entire body of fishes like Herring, Sardine, Salmon, Mackerel, Anchovy, etc. It is also extracted from offal and other wastes discarded from canneries or curing yards. Fatty fishes like Sardine yield more oil than non-fatty fishes. However, on an average about half kg of fish body oil can be obtained from five kg of fishes.

Fish body oil varies according to season, sex, size, age, nature of food and the locality from which it is caught. It has been observed that the body oil content in mackerel rises to a maximum in October- November and falls thereafter.

Fish body oil substantially differs from fish liver oil. Fish body oil is poor in vitamins A and D contents and has less unsaponifiable matter as compared to fish liver oil. The presence of various proportions of the glycerides of fatty acids (both saturated and unsaturated groups) has resulted in various uses of fish body oil.

Methods of fish body oil extraction:

There are two methods of extraction of fish body oil:

(i) Dry method and

(ii) Wet method.

(i) Dry method of extraction:

This method of extraction is used in fishes with low body oil content and the oil recovery is less than the wet process. The fishes are grounded in a grinder, cooked (with constant stirring) and pressed to recover the oil.

(ii) Wet method of extraction:

The wet method is employed for obtaining body oil in fishes such as Oil Sardine (Sardinella longiceps), which are rich in oil content. In the wet method, the fishes are crushed to a pulp and cooked with steam in a continuous vertical cylindrical cooker. The cooked material is then pressed and a mixture of oil and stick-water (pressed liquid of fish soluble) are collected into setting tanks or are centrifuged to separate the oil.

Refinement of fish body oil:

In both the above methods of oil extraction the residue (after pressing) is processed as a by-product — the fish meal. The oil thus collected after pressing contains protein debris and lots of other impurities such as water soluble and non-fatty acids of the body tissues.

The pressed liquid is first filtered and then subjected to various refinement processes such as:

(1) To neutralise the acids it is treated with caustic soda.

(2) To remove bad odour, the liquid is treated with super-heated steam and sodium carboante.

(3) To bleach the unwanted dark colouration, it is subjected to aeration.

(4) To remove moisture, it is heated to a temperature Of 105°C.

(5) To remove any stearine content, it is subjected to refrigeration.

Uses / Importance of fish body oil:

(1) After various refinement processes (as above), the better grades of body oils thus formed, are used for edible purposes.

(2) The fish body oil of high iodine value is very suitable for manufacture of paints and varnishes, as it is a drying oil.

(3) It is used in dressing of leather and tanning of skin.

(4) Body oil of low iodine value are generally preferred for making solid fats, such as margarine and lard (refined fat from the abdomen of a pig) substitutes.

(5) It is used in the manufacture of laundry soap and cheaper grades of toilet soap, insecticidal soap, etc.

(6) It is used in steel and iron industry for tempering of steel, concentration of low grade iron ores, etc.

(7) Due to the presence of vitamins A and D, the fish body oil is used for medicinal purposes, for animal and poultry feed and in aquaculture practices.

(8) It is used in the manufacture of chemicals such as alkyl halides, silicons and quaternary ammonium salts.

(9) It is used in the manufacture of cosmetics, lubricants, candles and cutting oils.

(10) Fish oil formulations when sprayed on citrus trees have proved effective as fungicide.

(11) It is used in the manufacture of printing inks, water-proofer preparations, plastics and linoleum (a substitute for rubber).

(12) Body oil is used for smearing the surface of boats for longer preservation.

8) Importance of Fish: Fish as a Source of Animal Feed

Fish meal is a brown powder which is made from both the whole fish and the bones while offal is made from processed fish which used as a high-protein supplement in aquaculture feed.

Fish meal is the next most important product after fish liver and body oil. It is a preparation where the body of fresh fish is ground, cooked and dried. It is a highly nutritive product and is an excellent poultry and animal feed, which increases egg and milk production.

The nutritive value of fish meal depends upon:

(1) Type of fish used (low fat and salt content to be used),

(2) The state of freshness of fish,

(3) Season of landing and

(4) Manner of preparation.

Chemical composition:

Moisture —6-12% (Moisture content is greater in lean fish than in fat fish).

Proteins — 55-70% (The protein of fish meal is of high digestibility coefficient and contains all the essential amino acids).

Oil/fat -2-15%.

Minerals — 10-20% (calcium 5%, phosphorous 4% and iodine).

Vitamins — Very rich in vitamins A, B, B₁₂, D, K and E.

Raw material:

The raw materials include fishes such as sardines, mackerels, ribbon fish, silver bellies and other fishes. Sharks and rays yield superior quality of fish meal. Fish meal is also obtained as a by-product of the canneries and fish oil industries.

Preparation of fish meal:

For manufacturing of fish meal the following methods are employed.

(a) Preparation for small scale production:

The fish is first minced and then cooked. To remove moisture, the cooked mass is pressed in screw presses. The cake thus produced is dried in the sun, or in flame driers in which the material is exposed to high temperature or generally in steam-jacketed drums under partial vacuum.

(b) Preparation for large scale production:

Here huge amount of raw material is used, that includes.

(i) Entire landed fish of poor food value,

(ii) Wastes from filleting plants (of canneries) and

(iii) Curing yards.

The raw materials, thus collected, are ground well to crush bone and flesh. The minced mass is then heated in steam, either by external application of steam (dry process) or by pressure-steaming through the minced mass (wet process).

Hydraulically operated pressing is then done and after extraction of oil and water, dry cakes are ready for sac filling and marketing. Fish meal is generally packed in gunny or coir bags, which are insect and vermin proof. Storage, if done in tin containers, is done under an atmosphere of nitrogen and with soldered lids.

Use of fish meal:

(1) Fish meal being a highly nutritive product (it contains all the essential amino acids) makes it an excellent poultry and animal feed which is practically good for all classes of livestock. By its use milk and egg production gets increased.

(2) As fish meal contains calcium, phosphorus, iodine and rich variety of vitamins, it is important for growing catties, for it promotes building of tissue and bone.

(3) Trash fish meal mixed with rice bran and vitamins, forms an excellent feed in aqua- culture.

9) Importance of Fish: Fish as a Source of Manure and Guano

Fish manure and guano are inferior quality of fish meal. It is not fit for animal consumption. Fish manure is a by-product of the curing yards, fish glue industries and oil extraction plants, where trash or spoilt fishes have been employed. Mackerel, horse mackerel, sardine, etc., which are spoilt and unfit for use as food is used for preparation of fish manure.

This manure has a high content of nitrogen (5-7%), phosphates about 4-6% and lime (CaO) 1-5%. For such nutrient content, fish manure is useful in raising coffee, tea and tobacco crops.

Fish guano is the by-product of the body oil extraction plant which is the dried refuse left after the oil is pressed out. Here oil bearing species such as oil sardines are used as raw material. Fish guano contains high concentration of nitrogen (8-10%) and appreciable quantities of phosphoric acid. For this, guano is several times more effective than any animal manure.

10) Fish as a Source to Produce Fish Flour (Hydrolised Protein)

Fish flour is a superior quality fish meal, produced under strict control and care, and forms an ideal protein supplement for human diet, even for infants of 3-4 months old. On commercial scale, it is produced by a sophisticated solvent extraction process.

The process is complicated and is not expensive. Fish is chopped and washed. It is then boiled with dilute acetic acid at 80°C. The mass is then washed thoroughly and the water is pressed out.

This is then treated with petroleum to remove fat and also to increase its keeping quality. The mass, thus, obtained is then hydrolysed with an alkali, preferably with caustic soda (10% at 80°C). The entire mass is then liquefied when it is neutralised with acetic acid (85%). The liquid is then dried with a spray, which subsequently forms a dry, cream coloured powder.

Use of fish flour:

(1) It is considered as an ideal protein source to supplement diet for both adults and infants.

(2) It is used to enrich bakery products such as bread, biscuits, cakes and soup.

(3) As the product contains high protein (35%), it is very suitable for convalescing patients struck with malnutrition, anaemia, etc.

11) Importance of Fish: Fish as a Source to Produce Fish Silage

‘Silage’ generally means fodder converted in a cylindrical tank called ‘silo’. Fish silage is a liquid or semisolid fish meal and is a highly nutritive animal feed. It is produced by adding 3-4% of an acid to a minced fresh fish or fish offal. Generally formic acid is used but sulphuric or propionic acid can also be used.

By using these acids the pH of the mixture can be lowered to 4.0 or below. This inhibits bacterial decay. The enzymes present in the chopped fish act upon it and reduce the mixture to slurry. An antioxidant is added to prevent rancidity of fats and the liquid can be stored in a silo up to 6 months.

Fish silage is also obtained by fermentation with lactic acid bacteria in molasses. The advantage fish silage has over fish meal is that the vitamins remain unaffected to a large extent and the product is free from fishy odour. Its production is more preferred in temperate regions (Norway, Denmark, etc.) than in tropical countries.

12) Importance of Fish: Fish Solubles as a By-Product of Fish

The residual part of the liquid which is obtained during the extraction process of fish oil is known as fish solubles. It is valued as additives to dry feeds for animals.

It is rich in protein and vitamin B-complex and has the following composition:

Water —50.0%

Protein —33.9% (all essential amino acids)

Fat —2-6%

Ash — 9.4%

Vitamin B-complex and choline.

13) Fish as a Source to Produce Fish Sausage and Ham

Fish sausages are prepared from minced fish flesh that are stuffed into a prepared intestine or similar other casings. Fish ham, on the other hand, has small pieces of solid fish meat (pieces of one square cm), mixed with pasted fish meat. In both the preparation, spices and additives are added to improve the taste, flavour and keeping quality.

Spices include salt, sugar, chillies, onion, corriander, glutamate, egg- white, hydrogenated vegitable oil, etc. Additives comprise antiseptics and antioxidants (ascorbic acid) to prevent rancidity. Colouring agents also may be added. These products are commercially manufactured in Japan, Russia and USA, and are prepared from less valuable trash fishes.

14) Importance of Fish: Fish is Used to Make Fish Macaroni

Macaroni is a pasta (flour and egg food preparation of Italian origin), prepared from wheat flour in the form of dried, hollow tubes. Fish macaroni is a product which is prepared from Puntius carnaticus. The fish is first minced and then mixed with tapioca or sorghum flour in equal parts.

It is then spiced with salt, chillies and tamarind. The product (paste) is extruded and dried. The product has good keeping quality, is cheap and easy to manufacture. It is manufactured on commercial scale by the Mysore Institute of India.

15) Importance of Fish: Fish is Used to Produce Fish Biscuits

Fish biscuits are manufactured in Chile and Morocco. It is blended with biscuit mixture prior to baking.

16) Importance of Fish: Fish as Source of Fish Glue

Fish glue is made by boiling the skin, bones and swim bladders of fish which has long been valued for its use in all manner of products.

Fish glue is a good adhesive obtained from trimmings, bones and skin of fishes belonging to order — Gadiformes (Cods, Pollack, Hakes, etc.). The raw materials are washed, chopped and steam-heated in steam-jacketed cookers.

The mass is then covered with water and to it is added small quantity of acetic acid. It is then cooked for 6-10 hours. The liquor is extracted and concentrated to form glue. The residue is dried and is used as manure.

Fish glue is used for:

(1) Smearing the backs of glued stamps and labels.

(2) Glue obtained from cod is of better quality and is used in photo-engraving.

(3) Low quality fish glue is used as adhesive for paper boxes, shoes and other things like furniture where joining is required.

17) Importance of Fish: Fish By-Product No. 17: Isinglass

Isinglass is a gelatin-like material obtained from the swim bladder or air-bladder of certain fishes. When put in water, it swells up but does not dissolve in it. At high temperature it hydrolyses in water to produce strongly adhesive gelatin.

Swim bladder is a hollow sac, the outer layer is thick and fibrous, while the inner one is thin, often with a silvery lustre. The thin, inner silvery shiny layer of the air-bladder of some fishes, such as sturgeons, carps and catfishes, is used to derive isinglass.

For preparing isinglass the air-bladders are collected, washed thoroughly to remove blood and other extraneous matters. Then the outer thick and fibrous layer of the wall is separated from the inner layer, which is exclusively isinglass raw material. This is then sun-dried and marketed.

Isinglass has the following uses:

(1) Isinglass is used mainly for clarification of wine, beer and vinegar.

(2) It is used for the preparation of special grade cement and plaster.

(3) Formerly it was used as a substitute for gelatin in confectionery.

18) Importance of Fish: Fish Product No. 18: Fish Skin

The skin of larger fishes is collected, soaked in brine and left for a day. On the next day it is salted and again put in brine containing 10% hydrocholoric acid. The skin is then taken out, drained and scraped on the surface, particularly to remove fine denticles present in the skin of sharks. They are then limed and tanned by the usual process.

Fish leather has various uses, such as:

(1) Natives of old age used the dried and spiny skins of Globe fishes or Porcupine fishes for making war helmets.

(2) In Japan the dried skin of Puffer fishes is inflated and used to make lanterns.

(3) Now-a-days the skins of larger fishes, such as cod, salmon, halibut, toadfish, sharks and rays are tanned and marketed as ornamental leather and can be dyed in different colours.

(4) Fish leather, particularly of sharks, is used in making shoes, wallets, bags and tobacco pouches.

(5) The skin of sharks, ray, skates are very hard and is used as an abrasive for polishing wood or metal.

(6) Suitably prepared and dyed skin of sharks providing ‘Shagreen’ issued for covering card cases, jewellery boxes, sword scabbards, etc.

19) Importance of Fish: Fishes Used for Artificial Pearls

The silvery scales of Europen cyprinid have been used for the manufacture of artificial pearls. By scrapping the scales, a glossy pigment is obtained. It is then coated on the inner surface and formed into hollow glass beads. The beads are then filled with wax.

20) Importance of Fish: By-Product No. 20: Fish Fins

The fins (except caudal fin) of shark are cut near the root, washed in sea water, dusted with a mixture of wood ashes and lime and dried in the sun or smoked. The cured product is crisp and brittle. In China and Philippines the shark fins are used in soup.

21) Importance of Fish: By-Product # 16. Fish Roe and Fish Caviar

Roe (mass of eggs or spawn) of a number of fishes is considered as food. The protein of roe is tasteless and its digestibility co-efficient and biological value are 81 % and 88%, respectively. Roe fat is characterised by high lecithin (59%) and cholesterol (14%). Roe is a good source of vitamin B. It also has vitamins C, E and D.

Caviar is the processed and salted form of roe of any large sized fishes. The caviar of sturgeons is held in high esteem as a very delicious food and serves as an appetiser.

22) Importance of Fish: Processed fish products

Surimi refers to a Japanese food product intended to mimic the meat of lobster, crab, and other shellfish. It is typically made from white-fleshed fish (such as pollock or hake) that has been pulverized to a paste and attains a rubbery texture when cooked.
Fish glue is made by boiling the skin, bones and swim bladders of fish. Fish glue has long been valued for its use in all manner of products from illuminated manuscripts to the Mongolian war bow.
Fish oil is recommended for a healthy diet because it contains the omega-3 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), precursors to eicosanoids that reduce inflammation throughout the body.
Fish emulsion is a fertilizer emulsion that is produced from the fluid remains of fish processed for fish oil and fish meal industrially.
Fish hydrolysate is ground up fish carcasses. After the usable portions are removed for human consumption, the remaining fish body – guts, bones, cartilage, scales, meat, etc. – are put into water and ground up.
Fish meal is made from both whole fish and the bones and offal from processed fish. It is a brown powder or cake obtained by rendering pressing the whole fish or fish trimmings to remove the fish oil. It used as a high-protein supplement in aquaculture feed.
Fish sauce is a condiment that is derived from fish that have been allowed to ferment. It is an essential ingredient in many curries and sauces.
Isinglass is a substance obtained from the swim bladders of fish (especially sturgeon), it is used for the clarification of wine and beer.
Tatami iwashi is a Japanese processed food product made from baby sardines laid out and dried while entwined in a single layer to form a large mat-like sheet.

23) Importance of Fish: Other processed products

Pearls, mother-of-pearl, and abalone are valued for their lustre. Traditional methods of pearl hunting are now virtually extinct.
Sea horse, star fish, sea urchin and sea cucumber are used in traditional Chinese medicine.
The Sea snails Murex brandaris and Murex trunculus are used to make the pigment Tyrian purple.
Some sepia pigment is made from the inky secretions of cuttlefish.

24) Importance of Fish: Fish Byproducts

A shimmery substance found on fish scales, most usually obtained from herring and one of many by-products of commercial fish processing, can also be used for pearlescent effects, primarily in nail polish, but is now rarely used due to its high cost, bismuth oxychloride flakes being used as a substitute instead.

25) Importance of Fish: Live Fish & Pets

Fish may also be collected live for research, observation, or for the aquarium trade.

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