Physico-Chemical Characterization of Shark-Fins

Shark-fins are one of the most expensive fish products in the world that fetch high prices in the oriental market. The value of the fins depends on the species, size and quantity of fin needles. These factors are largely determined by the intrinsic chemical and physical characteristics of the shark-fins which this study addressed. ' In order to formulate the relationship between body size and fin sizes of sharks, seven hundered and sixty-six shark specimens were measured and recorded from landing sites in Oman between July, 1991 to June 1992. The regression of body size in relation to the fin sizes revealed different R2 within and among the different species of sharks. The best correlation was between the precaudal length and all four fins (dorsal, pectoral, tail and lower lobe of tail), especially in the spinner shark (R2=0.97). This will aid shark-fin vendors and purchasers to estimate sizes of the identified species to predict their values in the market. In the yield studies, the white fins gave a higher yield than the black fins. However, the lower lobe of tail from black varieties gave the heighest yield in fin needles, especially in the silky shark. Processing and


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In order to formulate the relationship between body size and fin sizes of sharks, seven hundered and sixty-six shark specimens were measured and recorded from landing sites in Oman between July, 1991 to June 1992. The regression of body size in relation to the fin sizes revealed different R 2 within and among the different species of sharks. The best correlation was between the precaudal length and all four fins (dorsal, pectoral, tail and lower lobe of tail), especially in the spinner shark (R 2 =0.97). This will aid shark-fin vendors and purchasers to estimate sizes of the identified species to predict their values in the market.
In the yield studies, the white fins gave a higher yield than the black fins. However, the lower lobe of tail from black varieties gave the heighest yield in fin needles, especially in the silky shark. Processing and ii extraction of fin needles from pectoral fins of dogfish was more economical than from the tail as it required a about half the time of the tail processing.
The thickness of fin needles was directly proportional to the size of the fins. Due to swelling in preheated water at 60-7o 0 c, fin needles increased in thickness to an average of 79.8% of their original width and decreased in length to an average of 57% of their original length.
The proximate analysis of fin needles showed a very high nitrogen content, very low ash and no oil content.
' non-protein nitrogen was not detected. To the contrary, the fin's flesh had a higher content of non-protein nitrogen, ash and fat than the fin needles. The amino acid distribution of elastoidin is similar to that of collagen, except that the former contains cystine and a higher amount of tyrosine. The amino acid profiles indicate no signifcant difference between fin needles extracted from white varieties or black varieties of fins.
The essential amino acids score of elastodin was less than half that of casein. Thus shark-fin is of low nutritional value. Elastoidins are very rich in sulfur which may explain the peculiar hydrothermal properties that distinguish them from other collagens.
Needles extracted from shark-fins are of high commercial value and are in high demand among the Chinese.
This suggests that future studies could concentrate in iii finding innovative methods to produce artificial needles or use the extrusion techniques to prepare protein fibers from shark-fins simulating the shark-fin needles.  imported ).
The market is highly quality conscious and the quality l and quantity of fin needles in the shark-fins is very important. These fin needles or rays with the cartilaginous radials serve to support the fins are also called elastoidin fibers or ceratotrichia (Alexander, 1975;Budker, 1971;Jollie, 1962). Best prices are obtained for a complete set of fins from a single fish rather than a mixture of all sorts of fins together (King et al, 1984). However, present day exports are mainly graded by the type, size and color (black or white fins) . (cartilaginous fish) with skates, rays and chimaeras; the subclass Elasmobranchii with skates and rays; the order Selachii meanings sharks in Greek (Lineaweaver, 1970).
The fossil record of the cartilaginous fish consists mainly of teeth, spines and vertebrae since cartilage disintegrates shortly after death. These cartilaginous fish arose from the Placodermi (armored fishes) in the Devonian period. The placodermi mark a notable advance in vertebrae evolution in their possession of hinged jaws which revolutionized the feeding method and hence became more active and predaceous with paired fins development (Alexander, 1975;Castro, 1983;Keeton, 1967;Marshall, 1965) .
To provide a framework for considering the mainstream of elasmobranch evolution, scientists divided the shark evolution into three periods or levels:- (Castro, 1983; 3 Gilbert, 1967;Maisy, 1987).
The Cladodont Level: The most ancient and primitive sharks, which started some 400 millions years ago and lasted for about 50 million years. Their name is derived from their multicuspid teeth (cladodont = branched tooth) and the best known of the cladodont shark is Cladoselache.
As indicated by fossil records found in Ohio, Kentucky, and Tenessee, it was only about a meter long shark. The pectoral fins did not have narrow bases as in modern sharks, so their range of movement must have been limited. According to Marshall (1965) (Ronsivalli, 1978). There are usually five pairs of gill opening located laterally, rarely six or seven. The mouth is usually ventral or subterminal on the head. The teeth on the jaws are set in numerous transverse rows and are constantly replaced from inside the mouth (Fischer and Bianchi, 1984).
Mature sharks vary in length from 15-19 cm to 12.1 m or more, and with weight varying from 10-20 gm to several metric tons. Most sharks are of small or moderate sizes; about 50% are of small sizes, 32% between 1 to 2 m; 14% between 2 to 4 m; and 4% over 4 m in total length (Fischer and Bianchi, 1984).
Most sharks are carnivorous, they feed on benthic invertebrates to pelagic cephalopods, small to large bony fish, and other sharks and rays. Ironically, the two largest species, whale sharks and basking shark feed on plankton by filtering water through their gill slits (Stevens, 1987).
According to Fischer and Bianchi (1984)  c-Biological Characteristics of Sharks: 1-Biology of Sharks: Marine teleosts maintain their blood concentration much lower than the surrounding sea water, thus must drink sea water to make up the osmotic water loss (and ion gain) across the permeable surfaces. However, in elasmobranchs ' tend to have blood osmolarity slightly more concentrated than the sea; thus they are able to prevent excessive gain or loss of water physiologically (Boylan, 1967;Moyle and Cech, 1988;Ronsivalli, 1978).
The high osmolality is achieved by combining a total blood electrolyte concentration about the same as, or a little greater than, that of the marine teleost fish, with the retention of urea and trimethylamine oxide (TMAO) in the blood. Consequently, water enters the body by osmosis as well as electrolytes tend to enter by diffusion, + especially Na and Cl as the salt concentration in the blood is less than in the sea water. The concentration of the various solutes, mostly sodium, chloride, urea, and TMAO, in the blood of elasmobranchs combine for an osmolality of about 1000-1100 milliosmole (mOsm)/kg while in the sea water is about 930-1030 mosm/kg (Bond, 1979).
since elasmobranchs must excrete salts, they posses a unique physiological organ specialized in sodium excretion known as rectal gland. This gland supplement the kidney as a pathway for salt removal (Hickman Jr. and Trump, 1969;Bond, 1979;Oguri, 1990).
High urea concentration is maintained in elasmobranch by both the relative impermeability of urea by the kidney.
This is unique. The kidney of most other vertebrates excrete urea instead of retaining it (Oguri, 1990). As much as 90-95% of urea, which is produced as end product ' of nitrogen metabolism in the liver and 95-98% of the filtered TMAO are reabsorbed by the tubules of the kidney of dogfish, Sgualus acanthias (Hickman jr. and Trump, 1969;Perlman and Goldstein, 1988).
The origin of TMAO in elasmobranch is not clear and 8 it is synthesized at a very low rate, to compensate the losses in the kidney and the gills (Goldstein and Funkhouser, 1972). According to Yancey and Somero (1979) marine elasmobranchs contain urea at concentration averaging 0.4M, which is high enough to significantly affect the structure of many proteins and the functions of many enzymes. Also present in the cells of these fish  Marshall, 1982). According to Stryer (1988) evidences indicate that urea act by disrupting non-covalent interactions in polypeptide in which, the reduced, randomly coiled polypeptide chain devoid of enzymatic activity. However, the presence of these compounds and amino acids will counteract urea action by stabilizing many inter-and intra-macromolecular interactions involving non-covalent bonds.
cartilaginous fish have large fatty livers. As a result, their hepatosomatic index (HSI) which is expressed ' as a percentage ratio of liver weight to body weight is usually high (Oguri, 1990). The predominant component of lipids stored in the fatty liver is squalene (Heller et al., 1957;. These unsaponifiable substances of shark liver oil also includes besides squalene, pristane, zamere, and to a lesser degree glycerol alcohol have very low specific gravity; therefore, may be used by as sources for buoyancy control, especially in deep water sharks (Summers and Wong, 1992;Kizevetter, 1973). In a study conducted by Bone and Roberts (1969) they have shown the significance of static lift provided by the liver of some species, but the density of most species was determined by the density of tissues as well the liver. In recent study conducted on blue sharks, Hazin et al. (1991) found out there was no significant correlation between body size and weight of the liver in both the males and females of the blue sharks.
2-Body Temperature: some fish, such as the more advanced scombroids and some sharks are able to conserve the metabolic heat generated by the red muscle during cruising to maintain the myotomal muscle 7-lo 0 c above ambient water temperature. This remarkable discovery was reported by ' Carey and Teal (1969) as he measured the distribution of temperatures in mako and probeagle sharks. The pattern of isotherm was similar to that in a tuna with the warmest temperatures in the red muscle at the heaviest region of the body. These warm-bodied fish conserve heat through use of a set of countercurrent heat exchangers located in the circulation between the gills and the tissues. The heat exchanger form a thermal barrier which permits the flow of blood but blocks the flow of heat. These countercurrent heat exchangers are the rete mirabile (Carey and Teal, 1969;Bond, 1979;Bone and Marshall, 1982;Ronsivalli, 1978).
Black-tip sharks also have an elevated body temperature but they seem to lack the well-developed counter-current heat exchanger system. Carey et al. (1972) suggested that black-tip sharks are taking 11 advantage of the warm surface layer to raise their temperature, then manipulate their circulation to reduce heat loss. Ian Anderson (1987) who is probably the first scientist to drop a thermometer down the throat of a great white shark, have shown that the shark raises the temperature in its stomach by as much as 6.7°c during meal time to help the digestion of meals.

3-Metal Accumulation:
' Sharks accumulate mercury in their bodies, and the average level of mercury increases progressively with the age of the shark. Mercury residues differ between individuals of one species and between species. Younger individuals have usually a lower mercury level than older one (Kreuzer and Ahmed, 1978).
As top predators, sharks are considered as indicator of metals in the environment; therefore, obtained results reflect the bioavailability of the pollutants which also indicate the true state of pollution of the studied environment. In related studies by Marcovecchio et al. (1991) total mercury, cadmium and zinc accumulation was studied in muscle and liver from three species of sharks.
The mercury concentrations were similar in both muscle and liver while the concentration of cadmium and zinc were higher in liver than in muscle. They also found that the 12 metal concentration increased proportionally to the total length of the sharks. In previous studies Lyle (1984) has also shown that mercury concentration was highly dependent on the shark size and increased more or less exponentially with length. Maximum observed concentrations exceeded 1.5 mg/kg in species of hammerhead sharks. This exceeded the tolerance levels established by law which is 0.5 mg/kg, set by the Australian National Health and Medical Research council.
These studies concluded that metal accumulation is \ basically related to shark diets, longevity and slow growth rates which contributed significantly to the accumulation of such high concentration of metals especially, mercury.

4-Reproduction:
All sharks have internal fertilization and production of small numbers of large young, which hatch or born as active, fully developed miniature sharks after a long gestation period (Castro, 1983;Moyle and Cech, 1988).
There are three mode of reproductions in sharks; Oviparity, ovoviviparity, and viviparity. Oviparity is the most primitive in sharks, in which sharks lay large eggs enclosed in leathery cases for protection. This mode of reproduction found in four families of shark which 13 includes the whale shark (Castro, 1983). some livebearing sharks, including most requiem sharks, hammerhead and all weasel sharks are placental viviparous in which the embryos are dependent on stored yolk. The ovoviviparity is also known as a placental viviparity is the most common where the embryos are nourished by yolk stored in a yolk sac (Fischer and Bianchi, 1984;Ronsivalli, 1978).

5-Growth Rate:
' Unlike teleosts (bony fish), elasmobranchs are an extremely long-lived, slow-growing whose reproductive capacity is limited by late maturity, long gestation period, and low fecundity (Wood et al., 1979). Lower growth rates in sharks may be a consequence of their asynchronous and irregular feeding, slower digestion times, longer time of evacuation and elimination of a meal, thus new tissue production in sharks is slower compared with bony fish (Wetherbee et al., 1990).
As in most other fish, the rate of growth of a shark is determined in cm/yr which decreases continually as the shark ages. For example, Carcharhinus sorrah grows at a rate 20 cm/yr during the first five year after birth, then growth decline to 5 cm/yr or less while Carcharhinus tilstoni, grows at 17 cm/yr and by the time the shark are 14 5 years old, growth decline to 8-10 cm/yr (Davenport and Stevens, 1988). According to Stevens (1987) lemon sharks grow at about 15 cm/yr initially, but do not mature until around 240 cm which means they may take fifteen years to reach maturity. Age and growth of sharks show considerable variation between species and within species and the majority of sharks seems to have a maximum life span of 20 or 30 years (Hoenig and Gruber, 1990 (Kreuzer and Ahmed, 1978).

1-The meat:
Sharks have been used as food since men were able to catch them. According to Horn and DeBoer (1986)  In preparing fresh and frozen meat from shark, the fish must be bled as soon as possible to reduce the level of urea. For processing, the fish should be headed, gutted, washed and in some presentations, the shark is skinned. After processing, the shark meat needs to be washed to be frozen, dried, salted, and smoked. In case of freezing, shark meat frozen at -2s 0 c (-13°F) and then can be cut while frozen into fillets as the case of large \ sharks or into trunks with the head, tail, guts and skin removed in small sharks (Kreuzer and Ahmed, 1978). The flavor and quality of meat and its products depend on effective bleeding, shark species, and sanitary handling practice (Ronsivalli, 1978).
Salting is probably the most common way of preserving shark meat. This involves two general methods; pickle salting and dry salting. In the former, 2 cm thick fillets are covered with salt and packed into a water-tight container with salt sprinkled between each layer. In dry salting, granular salt is used on 2 cm thick fillets and exposed to the sun. Salt should be free of microorganisms especially halophillic bacteria which cause a pink discoloration as a result of using solar salt. Mineral salt is preferable as it contains less impurities, such as calcium and magnesium salts, and 16 halophilic bacteria (Limpus, 1991). Meanwhile, iodized salt should also be avoided, as flesh. turns black and shark will spoil during the drying process (Seymour and oanberg, 1980). In intial stages of drying, greater care should be taken to avoid flesh hardening due to rapid drying. For best results, shark fillets during night time are staked in piles and a heavy weight applied to facilitate drying and flatten the portions to hasten drying (Limpus, 1991 (Morris and Stouffer, 1975).

2-The Skin:
The special feature of sharks is strong and rough skin with the placoid scales embedded in the skin which make it very hard to cut and stitch the leather. Such denticles protect microbes lodge among them (Ronsivalli, 1978).
Shark skin is much more susceptible to damage of extremes of pH, heat, and microbial activity. However, properly skinned, fleshed and tanned skin makes the leather of shark much stronger and more durable than most mammalian leathers (King et al., 1984).
shark hides are graded according to species, size and defects on the skin. Hide from nurse shark is very valuable and skins from other species of sharks exceeding 1.5 m in length can generally be produced (Limpus, 1987).

3-The Liver:
The liver oils of many sharks have proved to be a ' valuable source of vitamin A. However, the subsequent development of a synthetic route for the commercial production of vitamin A contributed to the ultimate demise of shark liver oil industry (Kreuzer and Ahmed, 1978;Summers and Wong, 1992).
When liver lipids of bony fish are treated with alkali (saponification) a chemical soap and a free alcohol are formed and only traces of unsaponifiable matter remains.
However, in lipids of shark, a high concentration of unsponif iable matter remains as residue containing long-chain saturated or unsaturated fatty acids and vitamin A (Olsen, 1987). In sharks the bulk of unsaponifiable substances is squalene as well as pristane, zamene, glycerol alcohols, and saturated and unsaturated fatty acids (Kizevetter, 1973).
According to summers and Wong (1992) the world market for cosmetic products from recovered liver oil is growing rapidly. such oil should be first degummed (removal of metal oils), bleached and deodorized to produce moisturizing hand lotion and sunscreen lotion.
oiacylglyceryl ethers from natural sources such as liver oil have bacteriostatic action and inhibit tumor growth, thus make them extremely beneficial along with other hydrocarbons for cosmetic formulation and production.
Sharks have pharmaceutical value such as the heparin-like compounds in dogfish that tend to prevent blood clots; shark liver extract was also successful to treat cancer in mice, rats and chickens. Shark blood contains antibodies that fight disease causing in human (Ronsivalli, 1978 and about $ 1000.00 for a large one in Australia (Olsen, 1987) .

E-Shark Fisheries and Conservation:
The gear used for recreational purposes is usually limited to handlines and rod and reel. Commercially, longlines are the most popular method for catching large sharks (Castro, 1983 (Fischer and Bianchi, 1984).
During the post war period from 1947-1985, shark catches have tripled for thirty families of sharks, 20 especially in third world countries, as the world catches have increased from 200,000 to 600,000 MT (Compagno, 1990). Yet, sharks were caught off the south-east coast of the U.S. had jumped up from 504 tons in 1980 to 7,850 tons by the end of the decade, an increase of more than 1,500 percent (Fussman, 1991). Recent stock assessments indicate that the shark stock of the Western North Atlantic is exploited at a rate twice the maximum sustainable yield for all species, sizes, and relative abundance (Musick, 1993).
Elasmobranchs can provide a vital contribution to the economies of many small-scale fishing communities. For example, in Australia, several measures have been taken to protect, the depleted stocks of gummy shark and school shark which is a fishery industry valued as $ 15 million (Joll, 1993).
According to Dayton (1991)  similarities with the profile found in the wings of certain airplanes. Thomson and Simanek (1977) found in sharks that they examined that paired and unpaired fins were strikingly uniform in their position of insertion on the body, whatever the shape of the caudal fins.
Pectoral fins work just like the wings of an aircraft, as they provide lift and drag by the downward inclination provided by the moveable, narrow bases of these fins as part of the evolutionary specialization of modern sharks.
Caudal fins also exert a lift and a propulsive force during swimming, thus depressing the head. The lift due to the tail fin must be counterbalanced by that coming from the pectoral fins. These forces act as an upward force through the center gravity or point of balance (Harris, 1937). Thomson and Simanek (1970) suggested that the first 23 dorsal fin lies close to the vertical plane containing the center of balance. The interplay of ventral head area and pectoral fin area can be noted in the two species of hammerhead -Sphyrna tiburo and Sphyrna zygaena. The former have a larger head area and smaller total pectoral fin area but the combined area will be equal for both species. Unlike the bony fish, sharks spread their pectoral fins to provide lift while bony fish spread their pectoral fins to brake (Breder, 1926).
There is a need for this lift since most selachians ' are without a swimbladder which make them denser than the water. Their density can be determined by weighing the shark in the air and then immersed in water by applying Archimedes' Principle. The difference in weight between shark density and water specific gravity must be balanced by upward hydrodynamic forces of the pectoral fins and tail (Alexander, 1965(Alexander, , 1975. To keep afloat, most sharks use the liver which is rich in lipids as a buoyancy organ. Sharks possess high concentration of lipids in their liver, mainly squalene (Heller et al., 1957;Craik, 1978).

B-Anatomical Characteristics of Shark-Fins:
In vertebrate, cartilage and bones are the prominent structure of the skeleton which are specialized 24 derivatives of the connective tissues. Unlike bones, cartilage contains no canaliculi or haversian canal system. Therefore, blood vessels are absent (except in very large cartilage) ; the nutriment supplied to cells must be by diffusion (Romer, 1970;Webster et al., 1974).
In sharks, adult skeletons develop calcified cartilage especially in the vertebral column and the jaws, which produces a relatively hard and brittle endoskeleton.
calcified cartilage becomes infiltrated with calcium \ salts, thus resembles bone. Technically it is cartilage because it contains chondrocytes and chondroitin sulfate (Budker, 1971).
There are two types of fins, paired or unpaired. The median or unpaired include the dorsal, anal and caudal fin in sharks. The second type, the paired fins, represented by the pectoral and pelvic fins. Median fins develop by a fold of epidermis dorsally along the trunk to the tip of the tail. In case of dorsal fin, myotomes give off a muscle-buds which give rise to a muscle radials (Goodrich, 1930) . In the process of concentration of dorsal fins, the body grows faster in length than the base of the fin. Thus a dorsal fin derived from fourteen segments comes to occupy only about six myotomes in adult. (Alexander, 1975). These segments of cartilage rods called the pterygiophores are connected end to end. The larger one, which lies next to vertebral column called the basal, and the smaller one called the radial pterygiophore lie between the basal and sheets of packed ceratotrichia Norman, 1936), (Appendix 1).
Modern sharks are characterized by aplesodic fins in which the radials are limited to the basal half and several layers of ceratotrichia overlap the radials and extend out to the fin margin. In primitive sharks such as the cladoselach, radials extend nearly to the margin of the fin which is known as the plesodic fin (Jollie, \ 1991) .
In caudal fins, the major skeletal support is the neural and haemal arches with the vertebral column turning up into the dorsal part of the tail to form a heterocercal tail. Fin rays or ceratotrichia are present in both lobes of the tail-epicordal tail (dorsal side) and hypochordal tail (ventral side). In the lower lobe, these rays are more dense and well developed but modified and highly reduced in the upper lobe (Goodrich, 1930;Romer, 1970).
Pectoral fins are the anterior paired fins which are basically similar in structure to the dorsal fin. Its origin has been much debated but fin fold theory is more acceptable than modified gill structure theory as the origin of these fins (Goodrich, 1930;Romer, 1970).
Pectoral fins attached to the trunk by pectoral girdle 26 which articulate with three calcified cartilages called the basals. The central basal is termed the mesopterygium, which is the largest one. Metapterygium is the medial basal and propterygium is the lateral basal.
Distally, a series of segmented radial which are the main support of the pectoral fin is followed by ceratotrichia Applegate, 1967) (Appendix 1).
In sharks, ceratotrichia which is also called horny fin rays, dermal fin rays, and elastoidin fibers are unsegmented soft fin rays of epidermal origin (Jamieson, \ 1991;Goodrich, 1930;Romer, 1970;Howell, 1932;Applegate, 1967). During ontogeny ceratotrichia appears as a thickening of the basement membrane of the epidermis which are cut away by the movement of mesenchyme cells between the thickening and the membranes. With the first generation of ceratotrichium disposed into the dermis, a second one may form and dispose on both sides of the fin to which radial muscles become attached (Jollie, 1991).
In bony fish, fin rays differ from cartilagenous fins in that their rays are modified fin scales into elongated bony, jointed rays called lepidotrichia. The tip of the fins of bony fish may be additionally stiffened by tiny, unjointed, horny rods developed in the dermis of the skin which resembles ceratotrichia. These rods are called actinotrichia because of their fine structure (Goodrich, 1930;Jollie, 1991).

c-Biochemical Characteristics of Cartilaginous
Materials: Fibrous protein which includes collagen, elastin, alpha-keratin and silk are water insoluble. These contain a large percentage of non-polar, or hydrophobic amino acids, up to 93% in the case of elastin (Lehninger, 1970).
In their natural state, collagen fibers are inert, of high tensile strength, swell in acidic or alkaline media ' and exhibit a non-specific affinity for certain dyes, such as acid fuschin and anilin blue (White et al., 1959).
In order to determine the position of the atoms of a molecular or crystal structure in space such as fibrous protein, x-ray diffraction analysis is considered the ultimate experimental method. The spacing of regularly repeating atomic or molecular units in crystals can be determined by studying the angles and intensities at which x-rays of a given wavelength are scattered or diffracted by the electrons that surround each atom. Therefore, atoms having heavy metal, diffract x-rays the most and vice versa (Lehninger, 1970).
X-ray diffraction studies and the electron microscope, showed that collagen is a three-polypeptides chain twisted together to form a triple helix. The complete triple-helix unit is called tropocollagen. These units are arranged in a staggered alignment with characteristic cross striation at 600 to 700 Angstron, depending on their source and degree of hydration (White, 1973;Lehninger, 1 970;Bartley, 1968;Gustavson, 1964).
The triple helix structure is possible only because of the high incidence of glycine maintained by pairs of hydrogen bonds between the parallel peptide bonds, except for those involving proline or hydroxyproline. Increase in thermal stability of collagen has been attributed due to the increase in hydroxylated proline in collagen ' (Stryer, 1988;White, 1973). Thermal denaturation temperature is frequently sensitive to other forms of protein stabilization and destabilization treatment, such as ph, ionic strength, and the total number of imino acids residues (proline plus hydroxyproline) in collagen (Franks, 1988;Piez and Gross, 1960).
Heat denaturation of collagen yields a water-soluble protein, gelatin. Gelatin formation results from the separation or fragmentation of the three strands of the triple-stranded helix of collagen into a varying amount of smaller molecular species. This seems to involve only a physical change, since there is no chemical evidence of hydrolysis. Gelatin contains no tryptophan and small amount of tyrosine and cystine (Harper, 1987;harper, 1969) .
A distinctive amino acid in collage is hydroxylysine 29 which has two main functions: to participate in the formation of cross-links and to act as sites for the attachment of sugar groups (McGilvery, 1979).
Links within tropocollagen molecules and between different molecules are formed by lysine and hydroxylysine residues. such cross links are called aldol cross-link which stabilize and strengthen the collagen fibers (Stryer, 1988;Lehninger, 1975 (Gottschalk, 1972 A;Stryer, 1988 (Caplan, 1984). Blumenfeld et al (1963), concluded that glucose and galactose are attached to the protein through a glycosidic 30 bond in ichthyocol, and that the hydroxyl groups at positions 2, 3 and 4 of both hexoses are unsubstituted.
In galactose, the hydroxyl at position 6 is also unsubstituted. The hexosaminidic linkages are all (1 --> 4 ) and the glucuronidic (1 --> 3). In earlier studies Hoffman and Meyer (1962) showed that the hexosaminidic linkage was based mainly on the action of bacterial enzymes which acted by an elimination process with the appearance of alpha, beta -unsaturated acid.
In another study by Mathews (1971), trypsin and chymotrypsin were used to cleave the chondroitin sulfate-protein from the cartilage and notochord of some vertebrate and invertebrate species.
The mechanism of action of most of these regents such as urea, Beta-mercaptoethanol and guanidine hydrochloride is not fully understood, but it is evident that they act by disrupting nearly all non-covalent interaction in the polypeptides of native protein (Stryer, 1988).
In conjunction with collagen and polysaccharides, 33 elastin is found in most of the connective tissues.
unlike collagen, elastin can not be converted into gelatin bY boiling and its amino acid composition is different from that of collagen (Tables 1 and 2). The unique characteristics of elastin are its high content of glycine, alanine, proline and valine (Neuman, 1949).
About 93% of the side chains of the protein are non-polar or hydrophobic amino acids (Lehninger, 1970;Bartley,1968). However, hydroxylysine and glycosylated hydroxylysine are not present in elastin (Murray et al., ' 1990) .
Elastin disclosed a faint collagen-type diffraction based on small-angle diffraction pattern in beef ligament which would resulted from impurities in elastin.
Furthermore, results from electron optical studies concluded that elastin should be excluded from the collagen family (Bear, 1952). Spiro (1972 B) outlined the criteria to be a member of the collagen family. These include, the occurrence of hydroxylysine and hydroxyproline, the presence of approximately one-third of the amino acid (glycine), the observation of 640 Angstron periodicity under the electron microscope, infrared absorption spectrum, and the wide-angle x-ray diffraction pattern.
According to Bear (1952), x-ray investigations of collagen-containing tissues or derivatives involved in wide-angle diffraction exhibit essentially indentical patterns even with the degradation product of collagen, gelatin, yields, upon stretching, the same oriented diagram as tendon.
o-Biochemical Characteristics of Fin Rays (Elastoidin): Elastoidin, an insoluble fibrous protein found in the shark-fins which is also known as ceratotrichia, was first isolated from Mustelus laevis by c.s.w. Krukenberg as \ early as 1885 (Damodaran el al., 1956). In his remarks, Krukenberg noted its similarity to collagen but differed from the latter in not yielding gelatin on boiling with water. Yet, elastoidin classified in the collagen family on the basis of its wide-angle x-ray diffraction, and the presence of a 600-800 Angstron periodicity (Bear, 1952).
Finally, Damodaran et al (1956) showed the elastoidin amino acid composition which resembles the amino acid composition. Table 2 compares the chemical composition of elastoidin from shark-fin, bovine collagen and elastin.
The similarity of elastoidin to collagen can be summarized as follows: A high glycine content that amounts to 32%, the presence of hydroxyproline and proline that amounts to about 17% of the total residue, presence of hydroxylysine, threonine and serine in amounts usually found in mammalian 35 collagen, and the residues of non-polar amino acids up to 60 %, just about equal to the amount found in bovine collagen.
Elastoidin deviates from collagen in having a high tyrosine content and the presence of cystine which would contribute to the elastoidin distinctive hydrothermal properties.
It appears that elastoidin consists of a tightly bound mixture of a collagen-like substance which yields a water-soluble gelatin, rich in hydroxyproline, and a ' water-insoluble residue containing a remarkable a mount of tyrosine, 18-25%, and relatively little hydroxyproline upon autoclaving at 15 pound pressure for 16 hours . However, Ramachandran and Sastry (1964) and Ramachandran (1962) showed that elastoidin, Domadaran et al. (1956) have also reported such properties in elastoidin in which it contracted to about 30% of its original length at 63-64°c in water. However, applying longitudinal tension and cooling the shrunk fiber to 20°c, it regained about 85% of its initial length.
Bear (1952) shades light on formalin stabilization or formalin-treated specimens. Such specimens partially regain spontaneous length and the collagen wide-angle 38 pattern while untreated specimens remain shortened and iose their normal wide-angle diffraction as the case with avian tendons. This indicates that formalin stabilizes the protof ibril links of each fibril so that they do not become hopelessly disarranged during the shortening phase.
In the case of protofibril at the normal state (I), the fibril yields the collagen wide-angle diffraction pattern as protof ibrils possess the normal specific configuration.

E-Processing of Shark-Fins and Preparation of fin ' needles:
The processing of shark-fins requires skilled professional chefs, where a series of precise, week long procedures are used to make a bowl of soup from raw fin.

Recipes handed down from the time of the Southern Song
Dynasty, 800 years ago call for the raw fin to be scraped clean of meat, then boiled for two hours. The stock is then thrown away and the fin boiled again for two hours with fresh water. This is repeated for five days.
Finally, the fin is skinned and what little remains is transparent threads of gelatinous matter. To make a tastyand tempting dish of shark-fin soup, a rich and thick stock of chicken, mushroom, ham, ginger, scallions, soy sauce, sweet yellow rice wine, vinger, salt and sugar is mixed with the thread-like noodles (Sinclair, 1989).
For commercial purposes, shark-fins may be marketed in several forms; fresh, chilled, frozen, dried raw fins or processed (skin-off). Processed product forms include dried prepared fins and wet and dried fin nets (Appendix 4 ). Traditionally, the grading of shark-fin depends on the shark species or the natural color of the skin, size, thickness, form of presentation, and content of fin needles. However, present day exports are mainly graded by the type, size and color (black or white) ) and (Table 4). \ According to Limpus (1991) to insure the utmost quality of raw materials, the following proces.sing steps should be followed: 1) Cutting: Fins should be cut from the shark as soon as the fish is caught. Cutting and trimming of shark-fins need extreme care, otherwise their value is reduced. The dorsal fin has more meat at its base and should be cut with a broadly-curved, concave cut to eliminate the meat, but preserving as much of the fin as possible. This highly preferred cut by traders is called "half-moon cut" which can be applied to the pectoral fins as well ( Figure   6,8 and 13). Cutting meat from dried fins is not recommended as fins get harder and cause incorrect cutting. Trimming excess meat makes drying process much easier and fins will not become smelly as the case with irregular (crude) cuts where meat is left at the base of the fin. The residual meat often imparts a bad odour and color during processing with a deterioration of product quality. The lower part of the tail is cut off with a straight cut right under the thick cartilage that runs through the tail, keeping clear of the meaty part (Appendix 2).
2) washing and Sorting of Fins: Freshly cut fins have to be cleaned thoroughly by scrubbing away any dirt or \ adhering extraneous matter and washing them well in sea water. As restated by Table 3, bad handling and delay in cutting causes such defects as blemishes due to decay.
3) Chilling: If fins are to be sold or processed within a few days, they must be packed and stored at o 0 c.  (Table 3). Throughout the drying process, fins ' should be kept away from rain, sands and other extraneous matter that could contaminate the fins. The fins may be dried in the sun so that the moisture content is 10-15% level (MPEDA 1989;ISI, 1969) or to 7-8% moisture content (Clucas, 1982).
The properly dried fins make a characteristic sound when tapped against each other. Mechanical drying may be used when sun-drying is not possible. However, traders prefer sun-dried fins to oven dried fins ) .
In planning the processing facilities for fin processing line, Kreuzer and Ahmed (1978) recommended a plant designed for shark utilization that includes the following for fin processing: a working table 1 x 1 meter, a brine tank with 100 liter capacity, a working table 1.5 x 1 meter for trimming, a salting room with salting tanks, a drying yard at least 10 x 5 meter and a fin store 3 x 4 meter. Fins that are collected at the filleting and skinning line of the shark's pilot processing unit will be carried to the fin processing line. Fins will be handled at the working table, washed in the basin with 3% brine, then all traces of skin and meat are carefully removed at the trimming table. Finally fins are dried and stored.
In order to meet the market demand, many processing methods have been developed to extract fin rays and the ' most popular method is described by . In this method, fins are descaled and skinned in pre-heated water (80-90°C) to remove the skin (Appendix 3).
Sometime 3% hydrogen peroxide is used for bleaching and removal of blood stains. The final product is processed fin with the skin off but, otherwise, retaining its shape.
Some processors remove the very hard and non-edible cartilage base of the dorsal fins and the cartilaginous platelets between the two layers of fin needles in the pectoral and dorsal fins to obtain a better price (Appendix 4).
The final stage is preparation of the fin to extractthe fin needles by soaking and boiling the processed fin. Boiling will dissolve the membrane and expose the fin rays; then extraction of the fin rays by hand. The final product is wet or dried fin needles with 43 moisture content of 5-8%, just about ready for shark-fin soup ( Figure 11) .
In other modified processing methods, Nair and Madhavan (1974) and Ramachandran and Sankar (1989) used a simple process for extraction of fin rays from sharkfins by soaking the fins in 10% acetic acid for 24 hours to hydrolyze the collagen in the skin to gelatin. Therefore, skinning becomes easier. To soften the skin or muscles further, fins may be treated with acetic acid at 50-6o 0 c to allow fin ray extraction. However, in this method fin \ rays tend to swell due to acetic acid and shorten to about 30% of their original length.
In an improved chemical method for extraction of fin rays, Jayawardena (1980) used 1% HCl solution for quicker and easier extraction of different types of fins. Rays obtained with the use of dilute HCl were softer; however, dried fin rays' final product from white caudal fins using 1% HCl was of very poor quality, very thin, short and shrunk.
Jayawardena (1980) also tested the extraction of fin rays by using 0.1 NaOH and 10% acetic acid on other fins.
The products obtained by the former had soapy characteristics while the product from the latter had a reduction in length and increase in diameter. However, different method of extraction had no influence in the yield.  ). 1) Grading: Consumers and buyers are very conscious of the quality, processing method, and final presentation.
In general, traders prefer sun-dried fins to be a fin set of four fins from the same fish which will include 25% dorsal, 50% pectoral and 25% tail. Black fins generally fetch a lower price than white fins (Trachet et al. 1990). The most expensive of white varieties is Boon 1eong sit (in Chinese) while the most expensive of the black varieties is Tua sit (in Chinese), and in both cases they represent the largest sizes of fins (Tressler and Mewlemon, 1951;Domantay, 1958). small (10-20 cm), very small (4-10 cm) and mixed or assorted which includes the extremely small fins  and (Table 4). According to   2) Pricing: The wholesale and retail prices of raw dried fins are subject to frequent fluctuations, but those processed and prepared are more stable .

'
According to Walford (1931) ' Shark-fins are a unique commodity in the sense that their market is both a seller's and a buyer's market. The buyer is usually a processor who imports dried unprocessed fins, then sells to a wholesaler or a retailer and finally to an end-user.
Over 80% of imported shark-fins sold in Hong Kong ended in restaurants Infofish correspondence, 1991). However, according to  these channels of distribution are loosely structured and some large operators adopt the vertical integration approach in which they import, process, retail, export and re-export.
A few large seafood restaurants also import dried fins directly from abroad for their own use. c) Hong kong: The largest market for shark-fins is Hong Kong (Table   5 ). It continues to be very strong as rising incomes and improved living standards maintains Hong Kong as the biggest buyer of shark-fins. In comparing the total imports with re-exports, Hong Kong has re-exported only 15%, 19%, 20% of shark-fins between the year of 1985-1987, which indicates the size of the market and local consumption of shark-fins in Hong Kong (Infofish Trade ' strong in import and re-export (Table 5). Its own production of shark-fins is poor. Shark-fin trading in Singapore is sub-divided into unprocessed dried fins and processed or prepared fins.
The principal suppliers of dried shark-fins were Japan, India, and Sri Lanka in 1976.
However, in 1988-1989, India was the major supplier to Singapore as imports jumped up from 266 MT in 1988to 2348MT in 1989.
Singapore, also re-exported dried shark-fins and prepared fins to Hong Kong, Japan, and West Malaysia. The ' ratio of exports to total imports have been rising steadily since 1974 and 1976 (Kreuzer and Ahmed, 1978). Table 4 shows that this trend of decline in domestic consumption has continued between 1988-1990. Export of shark-fins in 1988 was 871 MT, which accounts for 46% of the total imports, but in 1990 exports jumped to 80% which leaves only 20% of the total imports for local consumption. According to Kreuzer and Ahmed (1978) this trend of decline in import and increase in export is probably due to a gradual change in the life style of the people, as less and less shark-fin is served on ceremonial occasions. e) Malaysia: Malaysia is a small market for shark-fins with a consumption of about us $ 0.5 million a year. The import and export of shark-fins consists of salted, dried or 51 in-brine and prepared shark-fins. The suppliers are mainly Japan, Taiwan and India. Shark-fin export to Malaysia suffered a major setback in 1983 due to increase in import taxes from 20% to 50% (Infofish Trade News, 1983 to continue the practice (Dayton, 1991).
According to Compagno (1990)  By these standards, the fins are measured by from the tip of the fin to a point in the middle part of the body where the cut is made as shown in Appendix 2.
Data collected in a one-year period, entered and stored in the computer to be analyzed for length frequency, species average length, seasonal variation, abundance, and percentage of ratio of fin length to shark length. 55 c-Morphometric Equations: In order to formulate the relationship between the body size (Standard/Precaudal length) and fin sizes (dorsal, pectoral and caudal fins) of each species, the linear regression formula Y = a + b x was adopted.
Data collected from sampling site was recorded and stored in the computer. A spreadsheet program (Lotus 123 or Quattro Pro 4.0) was used to analyze and compute the coefficient values and constant for a formula that ties one or more ranges of independent variables to a range of \ dependent variable, which also indicate the statistical precision of the actual or observed values during data collection.
In case of one independent variable, regression analysis allows the prediction of a value of a dependent variable based on other value of one independent variable: Where y is the dependent variable, ie. dorsal fin, a is the constant or the y intercept b is the slope or x coefficient x is the independent variable In case of more than one independent variable, regression analysis allows the prediction of a value of dependent variable on other values of more than one independent variables. In other words, multiple regression, which actually determines the possible 56 relationship between shark size to fins sizes (dorsal, pectoral and caudal fins) : The analysis was based on a one-year data collection which would provide morphometric equations based on each of the sampled species valued for its fins.

2-Physical Studies of Shark-Fins:
A-Yield studies: \ In order to study the yield of different types and grades of shark-fins on dry basis, fins were cut and collected according to the procedures described by  and processed by a modified method described by Nair and Madhavan (1974), and the Marine Products Export Development Authority (1989) (Figure 1) Fresh shark weight and precaudal length was recorded, then fins were measured by the standard measurements described previously (Appendix 2). Fin cutting involved the half-moon cut (Figures 6,8 and 13). The fins, sun-dried to determine the weight on dry basis. For processing, dried fins were soaked in water 24-48 hours.
The water was changed every 12 hours to soften the muscles. Then fins were placed in a container with 7% acetic acid solution for at least 24 hours to hydrolyze the skin to gelatine. The hydrolyzed skin was scraped off 57 by a brush in running cold water. The fin was then dried under the sun for another 48 hours and the weight was recorded (Figures 1,7,9 and 14). Thirty pectoral and thirty caudal fins were collected in the fresh form, washed, weighed, and the length was measured. The time was monitored in each step of the fin processing. Then, the excess meat of the pectoral fins was cut and trimmed. The weight was recorded before and after the cutting and trimming.
Fresh pectoral fins were soaked in 7% acetic acid for 24 hours while the tails soaked for an additional 24 hours to soften the skin and the meat of the tails. The skin ' was scraped off with a knife and the weight and the deskinning time was recorded.
For fin needle extraction, the processed fins were placed in boiling water and then needles extracted in chilled water. The extraction time was monitored and finally the wet fin needles were weighed and mechanically dried in an oven at 45°c for 5 hours. The dried needle weight was recorded and the percentage of yield was calculated as mentioned earlier.

C-Thickness and Hydrothermal studies of Fin Needles:
Thickness studies was performed in Oman on fresh, native fin needles (elastoidin) using a modified method described by Ramachandran and Sanker (1989). For this purpose, fin needles extracted from fresh pectoral fins of different grades of black fins and fresh dorsal fins of 59 different grades of white fins in their natural form. In this case, fresh fins were soaked in water for 24 hours, and then in 7% acetic acid for 1-2 hours only, just to soften the skin so the fin can be split into two halves.
The fin needles were extracted by hand in random and washed in fresh water. The color and appearance was determined visually. The length was measured by a ruler or a scale. Thickness was determined by measuring the maximum width of native fin needle using a standarized micrometer fixed in the eyepiece of a microscope.

\
Hydrothermal studies were conducted after the length and thickness of native elastoidin was determined. In this part of the study, native elastoidin was placed in pre-heated water between 60-7o 0 c to determine the shrinkage properties. Color and appearance was also observed, and length and thickness was determined as only one species which belongs to the Rhinchobatidae was identified as having white fins (Figure 8). These rays, or batoids, are close relatives of the sharks but differ from the latter in having their pectoral fin expanded forward and fused to the sides of their heads over the gill openings (Compagno, 1987). Thus, only their dorsal fins and caudal fins (whole tail) are cut and \ collected for export as white fins. These rays are also known as guitarfish. They are the main source of white fins which fetch a better price than black fins during export by shark-fin traders in India (Nair and Madhavan, 1974;MPEDA, 1989). In the grading system of shark-fins, fins are classified according to species and then by size within a species. Fins from Hammerhead sharks are graded as top grade while fins from the Black-tipped shark and guitarfish are considered as grade one fins King et al, 1984;).

B-Morphometric and Statistical Description:
Among the ten species observed at the landing site which have a potential value in the shark-fin market, only seven species were considered for statistical analysis.
The remaining three species, sicklefin lemon shark, H..egaporion acutidens, blacktip reef shark, Carcharhinus ~lanopterus, and guitarfish, Rhynchobatus djiddensis were rarely observed and were usually caught or landed in relatively small sizes. According to Nair and Madhavan (1974), fins from sharks over 1.25 min total length (approximately one meter in precaudal length) are considered of commercial value. Therefore, the three remaining species were not considered in the statistical analysis due to size and scarcity. ' During data collection, less than ten lemon sharks were recorded and only two attained the recommended size.
The blacktip reef shark was also are uncommon species with sizes recorded less than 1 m (PL). According to Last and Stevens (1994) the blacktip reef shark is a small-sized shark that can grow to a total length of 140 cm only.
Finally, the white spotted shovelnose ray or guitarfish was less common and just about a dozen rays were recorded.
Only one guitarfish was landed that attained a size of more than 2 m (PL) .
Such small sizes of sharks harvested off the coast of Oman suggests that sharks are caught as a bycatch using fishing gear for large pelagics. Figure 2 indicates that the majority of the shark landed are of small to medium size ranging from 1-1.5 m (PL). However, according to Fischer and Bianchi (1984), most of the sharks are of small to medium size; 50% are small, between 15 cm and 1 m (TL); and 32% are between 1 or 2 m (TL) .
.Among the seven species which is commonly observed during the study, the black-tip shark, Carcharhinus limbatus, and the pigeye shark, Carcharhinus amboinensis, attained the largest sizes (Table 7). The maximum reported size for these sharks is 250 cm and 280 cm (TL), respectively (Fischer and Bianchi, 1984). During data collection, the black-tip shark ranged from 121 cm to 202 cm (PL) (Appendix 9), while the pigeye sharks ranged from \ 134 cm to 178.7 cm (PL) (Appendix 12). These are heavy-bodied sharks with relatively large fins compared to body size (Table 8). These morphometric characteristics of having a large dorsal and pectoral fins are also shared by the sandbar shark . As indicated by Tables 7 and 8, the Scalloped hammerhead shark is an exception to the remaining species in that the average length or percentage fin length of pectoral fins is less than the average length or percentage fin length of the dorsal fin. This is probably a trade off in hammerhead sharks since they have a larger ventral head area and a smaller total pectoral fin area (Thomson and Simanek, 1970).
The smallest recorded body size of the seven species of sharks was observed in the spottail shark, carcharhinus sorrah. The average precaudal length was less than a meter with relatively small fin sizes (Table 7).
since the value of shark-fins depends on their natural color, form of presentation, content of fin needles and size of fins   (Table 4); the pigeye, the black-tip, the sandbar and the hammerhead sharks attained the best sizes of fins compared to their body sizes (Tables 7 and 8).
The best ratio of fin length to shark length in term of dorsal fin ratio is attained in hammerhead and sandbar sharks, in pectoral fin ratio the black-tip and sandbar sharks, while in tail ratio to body size in hammerhead and pigeye sharks. Thus, these four species are of superior quality out of the seven species studied for their morphometric characteristics.
During sampling, silky sharks were the most abundant and constituted about 33.6% of the total sampled shark 67 species (Figure 3). These results along with the findings from Anderson and Waheed (1990)   In the silky shark, regression formulas indicate that the best correlation is between precaudal length and all four fins (dorsal, pectoral, tail and lower lobe of tail) since the coefficient determination was the highest (Table 9). This set contained two hundred and forty-nine silky sharks ranging in size from 44 cm (PL) to 185 cm (PL) (Appendix 6).
A silky shark's precaudal length (PL) can be converted ' to its total length (TL) using the regression: (TL)= 3.4378 + 1.3358 (PL), R 2 = 0.997, N= 283 (Bonfil et al., 1993). Furthermore, Anderson and Waheed (1990) derived a length-weight relationship for silky sharks: However, it was found that size and weight vary greatly, not only among species and families, but also from one specimen to another (Kizevetter, 1973). With such formulas, shark-fin vendors and purchasers can predict the length of fins of silky sharks; thus they can grade the fins and predict its value in the market according to the size and type of fins of the silky shark (Table 4).
In hammerhead and spinner sharks, precaudal regression on the various fins revealed that fin length was the best predictor of shark size. However, fin lengths (dorsal, Pectoral, tail and lower lobe of tail) can be predicted 69 with good accuracy as the R 2 values were above 0.90 in both species (Tables 10 and 11) (Table 16) As previously mentioned, during the study, spottail sharks attained small to medium body sizes. The range of the shark body sizes sampled were between 59 cm to 155 cm (PL); however, the majority were less than a meter in precaudal length (Appendix 11) and (Table 7).
A precaudal length-to-fin length relationship for spottail sharks was based on a set of 97 measurements but three measureme nts were excluded from the analysis as outliers, leaving a total of 94 measurements (Appendix 11) and (Table 14).
Regressing tail length on body size revealed a good correlation among the four fins in the spottail shark; however, using all four fin regressed on body size was better correlated (Table 14, Table 16).
The worst correlation was revealed in pigeye sharks, especially with the regression of body size on dorsal fin or pectoral fin length (Table 15). As a large, slow-growing, and heavy bodied species (Randall, 1986), the pigeye shark can be expected to have an overlapping body si~e to fin sizes which caused bias in the results.
A reliable correlation was revealed in body size regresssion on all fins as well as with predicting the tail and the tail's lower lobe of the pigeye.
The use of multiple regression analysis by taking the fin sizes (dorsal, pectoral, tail, and lower lobe of tail) as a function of body size (precaudal length) revealed a stronger correlation than using the body size as the independant variable to predict the sizes of different fins (Table 16). Yet, by measuring the precaudal length with absolute precision, fin sizes can be determined or predicted to indicate the fin size or grade. Therefore, the value of such fin can be predicted in the market by knowing the size of the shark species that I have studied.  (Table   18). In the lower lobe, these fin rays (ceratotrichia) are more dense and well developed but modified and highly reduced in the upper lobe (Goodrich, 1930;Romer, 1970).

2-Physical
ThUS, in the black tails, needles are only available from the lower lobe. the rest of the tail (upper lobe) is discarded (Infofish International 2/91) . Among the black fins, the dorsal fins of the silky shark, the pectoral fins of the sandbar shark, and the tail or lower lobe of tail of the silky shark gave the highest yield of fin needles. This indicates that among black fins the difference in yield is due to differences in fin types as well as species difference.
Black fins from black varieties contain a considerable ' quantity of cartilaginous platelets interspaced between two layers of massive fin rays. Whereas, in white fins and the lower lobe of black tails the structure is constituted by rays and the gelatinous material with low cartilage content. Table 18 indicates that the white fin contains less than a half of the average content of cartilage of the black fins ( Figure 10). Since the pectoral and dorsal fins from black varieties contain large quantities of the cartilage platelets, many processors split the processed fins into two portions to remove the platelet. According to  such products increase the price of dorsal and pectoral fins, just like the processed tails, as it becomes packed only with individual strands of rays and gelatinous substances.
The yield of processed fins (skin off) from dried fins was higher in white fin than black fins which indicate 73 that black fins possess a thicker skin than the white variety, though the skin hydrolysis was not faster or easier with the white fins. Among and within different fins of different shark species there were different yield in the percentage of processed fins (Table 19).
ouring processing, dried fins required more soaking in water and acetic acid than the fresh ones to hydrolyze the skin, especially ones that had been dried and stored for a long period. Fins dried and stored for more than a year may need extended soaking in water and then treatment with ' hot acetic acid (MPEDA, 1989;Nair and Madhavan, 1974).
Fresh shark-fins usually give transparent fin needles of light color or golden yellow color when dried.
However, when the fin is dried and stored for a period of more than one year, a brown or reddish brown color was obtained. Prepared dried fin needles with 12%+2.0 moisture content have a brittle and hard texture. Soaking or boiling dried fin needles will cause hydration and swelling of fin needles due to water intakes. According to Bear (1952) dry elastoidin, unusually develops distortion at small angle diffraction, and unusually low axial periodicity of 600 Angstron as the long charged side chain at bands normally distort the vertical main chain helices from a straight course. Hydration in neutral water, causes the relaxation of attachment between protofibrils; therefore, more room becomes available for the charged side chains at bands which now permit straightening of the main chains and do not distort the main chain coil (Appendix 5).
Fin needle extraction was much easier with large fins than small fins. The latter contained tiny and thin needles that are extremly hard to extract and usually float in water during washing process. Thus they were easily lost during draining.
In the case of dogfish, the fins were in the range of very small to small fins because the size ranged between ' 5-10.9 cm in dorsal and pectoral fins while the tails ranged from 16-20 cm (Figure 12). Fin needle extraction was very tedious as they contained many tiny needles The actual effort to extract fin needles from the thirty pectoral fins was 223 minutes to get 131.55 grams of wet needles or an average of 7.43 minutes to get 4.385 grams from a single fin. In tails it required 396 minutes to get 110.06 grams of wet fin needles or an average of 13.2 minutes to get 3.668 grams from a single tail. The moisture loss was 77.53% and 72.9% for the pectoral and caudal fin at 45°C for 5 hours.

c-Thickness and Hydrothermal studies of Fin Needles:
Thickness of fin needles was directly proportional to the size of fins within species, but slightly varied among different species (Table 21). Among fin sizes of 20 cm and above, the white fin and blacktip reef shark contained thicker needles than in the other species. Fin needles from fins of 15 cm and below, contained thinner needles ' that usually dried up once exposed to the light of the microscope.
Prepared fin needles in the natural form (native elastoidin) have a physical characteristics of transparent light-yellow color, morphologically homogeneous with a hard but flexible texture. These needles shrunk immediately in the pre-heated water at 60-7o 0 c. As seen from Table 22, decrease in length or contraction at an average of 57% was associated with increase in thickness or swelling at an average of 79.8%. The transparency of the shrunk needles or elastoidins was reduced to a creamy yellow color with a softer and rubber like texture. Bear (1952)  Fin needles soaked in 10% cold acetic acid solution for 24 hours became thicker at an average of 1 mm in diameter with an appealing glassy appearance (Table 22) Angstron in acid-swollen fibrils based on electron microscope evidence (Bear, 1952;Balian and Bowes, 1977) 78 (Appendix 5) ·

3-Chemical Studies:
A-Proximate Analysis: Fin needles extracted from different fin types or different shark species showed a very high content in total nitrogen content. As indicated in Other studies revealed the content of little carbohydrate in elastoidin fiber such as glucose, galactose, glucoseamine and galactoseamine . The ratio of carbohydrate to nitrogen was extremely low at 0.061 in the elastodin fiber of tiger shark. Sastry and Ramachandran (1965) reported nitrogen content of 15.99% (dry basis) in fin needles extracted from tiger shark while Ramachandran and Sankar (l989) reported an average of 15.69% total nitrogen in the fin needles extracted from whale shark.
In contrast, the fin's flesh has a higher content of ash and fat than the fin needles (Table 24). According to Gordievskaya (1973), the flesh of almost all the shark species is lean except for the greenland and sevengill sharks. The protein content of shark meat is calculated by substracting the non-protein nitrogen from the total nitrogen content and the difference is multiplied by the conversion factor 6.25.
Impurities such as silica, sand and other extraneous materials could contaminate the fin and fin needles during drying or processing them. Thus such test is mainly to detect impurities in dried products that has not been prepared under hygienic conditions. c-Non-Protein Nitrogen: ' The component non-protein nitrogen in fin needles was not detected (Table 23). This is in contrast to fin flesh, which contained a considerable amount of non-protein nitrogen (Table 24). According to Kizevetter (1973), the specific taste of shark meat is due to the peculiar composition of nitrogenous substances in it.
These include the urea, TMAO, and nitrogen of volatile bases. Gordievskaya (1973) indicated that urea accounts for most of the non-protein nitrogen which scarcely depends on the size and weight of the shark. Furthermore, Yancy and Somero (1979) showed that the elasmobranchs contain a family of methylamine compounds, largely TMAO which is maintained at 1:2 molar concentration to urea.
At such concentration these methylamine compounds offset the destabilizing effects of urea, thus stabilize the protein structure in the elasmobranchs. progressively richer in sulfur also show increasing resemblance to keratin, whose resistance to swelling is attributed to stabilization of fibrillar structure probably by disulfide bridges between polypeptide chains.

E-Calculated Protein Efficiency Ratio:
As indicated in Table 26, the calculated essential amino acid score for elastoidins of hammerhead, guitarfish and dogfish were 45.1, 45.4, and 45.6, respectively as percent of essential amino acid score of casein. This 82 indicate that the protein's nutritional value of elastoidin is less than half of the casein since it contians very little of the essential amino acids.
Moreover, they are an insoluble fibrous protein which make them hard to react with digestive enzymes. Elastoidin extracted from fins of guitarfish (white fins) have a higher content of calcium, magnesium, and zinc but a lower phosphorus content than the fins of hammerhead (black fins) and dogfish. The mercury and lead content is low since the unit of measurement is part per billion. The tolerance level for mercury in the United States and Canada in fish is 0.5 ppm (Kreuzer and Ahmed, 1978 3-Among the seven species, the pigeye, the black-tip, the sandbar, and the hammerhead sharks attained the best ratio of fin sizes to body size. 4-Silky sharks were the most abundant species, followed by the spinner shark during data collection.

5-The regression of body size (precaudal length) to fin
sizes revealed different correlation within and among each species.
6-In the seven species, the best correlation was between precaudal length and all four fins (dorsal, pectoral, tail and lower lobe of tail) as the R 2 was the heighest.  23-Artificial needles should be considered for future studies by food scientists to satisfy the high demand for such product and make needles more accesible to people.             Figure 1. Stages of shark-fin processing and fin needle preparation during the study and end products.