Shark Muscle Research Articles

Inhibition of Tyrosine Phosphorylation of Vascular Endothelial Growth Factor Receptors in Human Umbilical Vein Endothelial Cells: A Potent Anti-Angiogenic Lipid-Rich Extract from Shark

We have previously reported that an ethanolic extract of dried shark muscle mixed with olive oil (shark muscle-olive oil [SMO]) has potent anti-angiogenic activity and that this extract appears to inhibit the binding of vascular endothelial growth factor (VEGF) to its receptor(s). In this study, we investigated the effects of SMO on the phosphorylation of VEGF receptor(s) in human umbilical vein endothelial cells (HUVECs). In vitro cell proliferation assays showed that SMO significantly reversed the VEGF-promoted increase in HUVEC proliferation. Western blot analysis revealed that SMO treatment markedly inhibited the VEGF-promoted tyrosine phosphorylation of VEGF receptor-2 (KDR) and VEGF receptor-1 (Flt-1) in a dose-dependent manner. These results demonstrated that SMO might interfere with or block the binding of VEGF with its receptors, and thereby inhibit the VEGF receptor(s) signal transduction pathway and so inhibit angiogenesis.

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) in tissues of humans, dolphins, and sharks from the United States

Concentrations of tetrabromobisphenol A (TBBPA) and α-, β-, and γ-isomers of hexabromocyclododecanes (HBCDs) were determined by liquid chromatography–tandem mass spectrometry (LC–ESI-MS/MS) in human adipose tissue obtained in New York City, and in three marine top-level predators – bottlenose dolphin, bull shark, and Atlantic sharpnose shark – collected from coastal waters of Florida, USA. The overall mean concentrations (mean ± SD) of TBBPA and HBCDs were 0.048 ± 0.102 and 0.333 ± 0.571 ng/g lipid wt in human adipose tissue samples, 1.2 ± 3 and 7.38 ± 18 ng/g lipid wt in bottlenose dolphin blubber, 9.5 ± 12 and 77.7 ± 128 ng/g lipid wt in bull shark muscle, and 0.872 ± 0.5 and 54.5 ± 88 ng/g lipid wt in Atlantic sharpnose shark muscle. Overall mean concentrations of HBCDs were 5–10-fold higher than mean TBBPA concentrations, in all of the samples analyzed. The highest concentrations of TBBPA and HBCDs were detected in the bull shark muscle at concentrations of 35.6 and 413 ng/g, lipid wt, respectively. Concentrations of TBBPA and HBCDs, after log-transformation, were significantly correlated with each other in human adipose tissue and bottlenose dolphin blubber, but not in bull shark muscle samples. In the human adipose tissue samples, the concentrations of HBCDs were 3–4 orders of magnitude lower than the concentrations of polybrominated diphenyl ethers (PBDEs) previously reported for the same set of tissue samples. Concentrations of HBCDs in human samples from the United States were 1–5-fold lower than the concentrations reported from several European countries. HBCD concentrations in bottlenose dolphins from the United States were 1–2 orders of magnitude lower than the concentrations reported for other cetacean species from Europe. The present report is the first to determine levels of TBBPA and HBCDs in humans, bottlenose dolphins, and sharks from the United States.

Essential and toxic metals in nine fish species for human consumption from two coastal lagoons in the Eastern Gulf of California

With the aim of knowing concentrations of Cd, Cu, Fe, Mn, Pb and Zn; percentage of daily mineral intake (PMI) for essential elements and percentage of weekly intake (PWI) of toxic metals in commercial fish from 2 coastal lagoons in the Eastern Gulf of California, analyses were carried out in 9 species. Highest values of Cd were detected in the liver of the sharks Sphyrna lewini and Carcharhinus leucas, Pb was mostly detected in the liver of S. lewini; Cu and Mn in the liver and gills of the mullet Mugil cephalus, respectively; Fe in the liver of the catfish Galeichthys peruvianus; and Zn in viscera of the catfish Cathorops fuerthii. From the point of view of public health and considering the edible portion, only in a few cases levels were above limits considered as safe for human consumption, such is the case of Cd in muscle of bull shark C. leucas (2.8 μ g g− 1) and catfish G. peruvianus (1.55 μ g g− 1), Pb in muscle of scalloped hammerhead S. lewini (5.2 μ g g− 1), Cu in muscle of scalloped hammerhead S. lewini (20.6 μ g g− 1) and Zn in muscle of Pacific herring Opisthonema libertate (53 μg g−1) and S. lewini (104 μ g g− 1).

Effective Diffusivity Determination Considering Shrinkage by Means of Explicit Finite Difference Method

Drying data of salted shark (Carcharhinus limbatus) muscle pieces samples, dried in a convective dryer, by using three different air conditions and two different air velocities, were treated by Fick's second law. The shrinkage during drying process was considered as a linear function of sample moisture. The Fick's second law equation was numerically solved by the explicit finite difference method to obtain effective diffusivity, considering shrinkage and with and without simplification of moisture content profile. The experimental data fitted very well independently of the simplification introduced on the moisture content profile. The best fit was obtained by considering volumetric average of sample moisture content. The effective diffusivity values calculated considering the shrinkage varied from 0.72 to 2.20 × 10−10 m2/s with the mean relative deviation modulus from 1.02 to 6.51%. The activation energy expressed in function of air temperature varied from 3.42 to 19.23 kJ/mol.

DSC measurements on sharks

Sharks are commonly termed fish, even though they are only distantly related to the classical (bony) fish. What differentiates a shark from a bony fish? Sharks have a spinal column and are thus vertebrates. However, their skeleton is not made of bones, but of cartilage, and together with their nearest relatives the rays and the chimeras they form the class of cartilaginous fish. Since the late 1980s trade in shark fin was considered to be one of the most valuable fishery products in the world. Another valuable shark product is cartilage. Shark meat has been used as food in coastal regions for over 5000 years. Small sharks are preferred for meat in many markets. In Germany, the belly flaps of spiny dogfish ( Squalus acanthias) are smoked as “Schillerlocken”, an expensive gourmet item. The question came up to us recently if we were able to detect whether shark muscle were heat-treated as in the case of smoking or not. Different tariffs for heated and untreated fishery products make it important for processors to label their products correctly. According to customs departments this necessitates investigations into whether the declaration of goods is true or not. Looking at the relevant literature, papers dealing with thermal stability of shark muscle were very scarce. Therefore, we decided to perform DSC measurements on a variety of shark using a SETARAM MicroDSC VII and to compare the DSC patterns obtained. Beside thermal stability the colour of different shark meats were also measured instrumentally. To answer the question of whether DSC measurement can differentiate previously heat treated sharks from those lacking this treatment, the cutlets from smooth-hound ( Mustelus spp.) underwent thermal treatment in the range from 40 to 70 °C. DSC patterns of the shark muscle and the skin were used to observe the influence of heat treatment.

Inhibition of Pro-Angiogenic Factors by a Lipid-Rich Shark Extract

This study aimed to determine whether a shark muscle oil-olive oil mixture influences activators of human angiogenesis. The mixture completely abolished the stimulation induced by vascular endothelial growth factor (VEGF), fibroblast growth factor-2, transforming growth factor-beta, and platelet-derived growth factor. This suggests that it may compete with these growth factors for their binding sites on the endothelial cell surface either by binding to the growth factor or by blocking the actual receptor. The possibility of the oil binding to the VEGF receptor was studied through the use of soluble forms of the receptors (VEGF-R1 and VEGF-R2). It was found that the shark oil-olive oil inhibited the formation of the complexes of VEGF with both of the receptors. This could have been because the oil bound to either the VEGF or the receptor or both. To determine which is possible, the shark oil-olive oil was mixed with the receptors. The molecular size of the receptors increased, and these larger forms of the receptor had reduced capacity for complexing with VEGF. Therefore, one mode of potential anti-angiogenic action of the shark muscle oil-olive oil is the inhibition of the activity of a number of stimulatory molecules, including VEGF. This study demonstrates that the blend of shark and olive oils antagonizes VEGF activity by binding to at least two receptors for the factor, thereby inhibiting the activation by the growth factor.

Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako shark (Isurus oxyrinchus)and the ectothermic blue shark (Prionace glauca) and leopard shark(Triakis semifasciata)

Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako shark would be greater than those of the ectothermic blue shark (Prionace glauca) and leopard shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako shark than in both ectothermic species, due to a lower proton conductance in the blue shark and a lower liver mitochondrial content in the leopard shark, and thus may contribute to endothermy.

Polybrominated Diphenyl Ethers and Polychlorinated Biphenyls in a Marine Foodweb of Coastal Florida

Nine species of marine fish, including teleost fishes, sharks, and stingrays, and two species of marine mammals (dolphins) collected from Florida coastal waters were analyzed for polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) to evaluate biomagnification factors (BMF) of these contaminants in a coastal foodweb. In addition, bottlenose dolphins and bull sharks collected from the Florida coast during the 1990s and the 2000s were analyzed for evaluation of temporal trends in PBDE and PCB levels in coastal ecosystems. Mean concentrations of PBDEs in muscle tissues of teleost fishes ranged from 8.0 ng/g, lipid wt (in silver perch), to 88 ng/g, lipid wt (in hardhead catfish), with an overall mean concentration of 43 +/- 30 ng/g, lipid wt. Mean concentrations of PBDEs in muscle of sharks ranged from 37.8 ng/g, lipid wt, in spiny dogfish to 1630 ng/g, lipid wt, in bull sharks. Mean concentrations of PBDEs in the blubber of bottlenose dolphins and striped dolphins were 1190 +/- 1580 and 660 ng/g, lipid wt, respectively. Tetra-BDE 47 (2,2',4,4'-) was the major congener detected in teleost fishes and dolphin samples, followed by BDE-99, BDE-153, BDE-100, and BDE-154. In contrast, BDE-209 was the most abundant congener in sharks. Concentrations of PBDEs and PCBs in dolphins and sharks were 1-2 orders of magnitude greater than those in lower trophic-level fish species, indicating biomagnification of both of these contaminants in the marine foodweb. Based on the analysis of sharks and dolphins collected over a 10-year period, an exponential increase in the concentrations of PBDEs and PCBs has occurred in these marine predators. The doubling time of PBDE and PCB concentrations was estimated to be 2-3 years for bull sharks and 3-4 years for bottlenose dolphin.

Purification Procedure and Monoclonal Antibodies: Two Instruments for Research on Vertebrate Porins

On Western blots of skeletal muscle preparations of different vertebrate classes, four monoclonal anti-human type 1 porin antibodies recognize one single band of either 30.5 or 31 kDa, respectively. To confirm that it is eukaryotic porin which is labeled by the antibodies, we used a purification procedure developed for human type 1 porin for porins from skeletal muscle of shark, frog, and turkey. Applied to different mammalian species and tissues, this procedure exclusively provides type 1 porin. However, applied to shark skeletal muscle, it provides two porin isotypes in nearly equal amounts. In the case of frog skeletal muscle, the procedure provides mainly type 2 porin and a lower amount of type 1 porin. Applied to turkey skeletal muscle, the method provides exclusively type 2 porin. As demonstrated by two-dimensional Western blots, both shark and frog porin isotypes and the turkey type 2 porin are recognized by our antibodies. Furthermore, we elucidated the entire amino acid sequence of frog type 2 porin.

Functional characterization of a muscarinic receptor in the smooth muscle of the shark (Squalus acanthias) ventral aorta

A suite of muscarinic receptor blockers was used to characterize the receptor(s) mediating the contractile effect of acetylcholine (ACh) on isolated rings of ventral aorta from the dogfish shark, Squalus acanthias. The M2/M4-specific inhibitor N,N’-bis(6-{[(2-methoxyphenyl) methyl] amino} hexyl) -1,8- octane diamine tetrahydrochloride (methoctramine) did not reduce the efficacy of ACh, and the M3-specific inhibitor 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP) displaced the ACh concentration-response curve to the right at much lower concentrations than the M1-specific inhibitor (5-11-dihydro-11- [4-methyl-l-piperazinyl)acetyl] -6H-pyrido[2,3-b] [1,4] benzodiazepin-6-one dihydrochloride) (pirenzepine). It appears, therefore, that an M3-type muscarinic receptor is expressed in the aortic vascular smooth muscle of the dogfish shark.

Influence of process variables on the hydrolysis of shark muscle protein / Influencia de las variables de proceso en la hidrólisis de proteína del músculo de tiburón

Muscle tissue from the spiny dogfish ( Squalus acanthias) was enzymatically hydrolysed using a bacterial endopeptidase. The influence of the process variables (temperature, pH, enzyme/ substrate ratio and reaction time) was investigated with regards to the extent of proteolytic degra dation and the recovery of soluble nitrogen from the substrate. Maximum significant nitrogen recovery (NR) was found to be 76.2%, in a 2 h proteolytic reaction. Optimum conditions were 55 °C, pH 8.0 and an enzyme/substrate ratio of 40 mg enzyme/g minced shark muscle (wet weight basis). Under these conditions, a degree of hydrolysis (DH) of 18.6% was obtained. A linear corre lation ( R2 = 0.99) was found to exist between the two measured parameters, NR and DH.

Effects of Urea on Thermal Gelation Process of Myosin B Prepared from Shark Muscle

Effects of Urea on Thermal Gelation Process of Myosin B Prepared from Shark Muscle

DIFFUSIONAL MODEL WITH AND WITHOUT SHRINKAGE DURING SALTED FISH MUSCLE DRYING

The drying process of salted pieces of shark muscle (Carckarhinus limbatus) was accomplished using three air conditions (20 °C -40 %RH; 30 °C - 30 %RH; 40 °C - 45 %RH) and two air velocities (0.5 m/s; 3.0 m/s). Shrinkage of material during drying was correlated as a linear function between linear dimension and moisture content. The experimental drying data were obtained using both the diffusional model with moisture content parameter (considering no shrinkage) and the diffusional model with moisture concentration parameter (considering shrinkage). The values of effective diffusivity varied between 1.50×l0−10m2/s and 2 85×l0−10m2/s for drying process considering no shrinkage and between 0.87×l0−10m2/s and 1.61×l0−10m2/s for process considering shrinkage. The activation energy was calculated assuming an Arrhenius' type equation. The values were 17.94 KJ/mol with the air velocity of 0.5 m/s and 21.94 kJ/mol with the air velocity of 3,0 m/s for effective diffusivity without shrinkage. The values were 2.04 kJ/mol with the air velocity of 0.5 m/s and 16.12 kJ/mol with the air velocity of 3.0 m/s for effective diffusivity with shrinkage. These low activation energy values, calculated considering the shrinking effect, show that the side effects during drying reduces the effective diffusivity dependence on temperature

Organochlorines and other environmental contaminants in muscle tissues of sportfish collected from San Francisco Bay

Edible fish species were collected from 13 locations throughout San Francisco Bay, during the spring of 1994, for determination of contaminant levels in muscle tissue. Species collected included white croaker, surfperch, leopard and brown smoothhound sharks, striped bass, white sturgeon and halibut. 66 composite tissue samples were analysed for the presence of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (P0CBs), pesticides, trace elements and dioxin/furans. The US EPA approach to assessing chemical contaminant data for fish tissue consumption was used for identifying the primary chemicals of concern. Six chemicals or chemical groups were found to exceed screening values (SVs) established using the US EPA approach. PCBs (as total Aroclors) exceeded the screening level of 3 ng g −1 in all 66 muscle tissue samples, with the greatest concentrations (638 ng g −1) found near San Francisco's industrial areas. Mercury was elevated (> 0.14 μg g −1) in 40 of 66 samples with the greatest concentrations (1.26 μg g −1) occurring in shark muscle tissues. Concentrations of the organochlorine pesticides dieldrin, total chlordane and total dichlorodiphenyltri-chloroethane (DDT) exceeded screening levels in a number of samples. Dioxin/furans (as toxic equivalent concentrations (TEQ's)) were elevated (> 0.15 pg g −1) in 16 of the 19 samples analysed. Fish with high lipid content (croaker and surfperch) in their muscle tissue generally exhibited higher organic contaminant levels while fish with low lipid levels (halibut and shark) exhibited lower organic contaminant levels. Tissue samples taken from North Bay stations most often exhibited high levels of chemical contamination. The California Office of Health Hazard Assessment is currently evaluating the results of this study and has issued an interim Health Advisory concerning the human consumption of fish tissue from San Francisco Bay.

Use of cysteine to remove mercury from shark muscle

The efficiency of cysteine to remove mercury from sliced and minced shark was evaluated. Treatment with 0.5% cysteine at pH 2.0–2.5 and subsequent washing with sodium chloride (5%) failed to remove the mercury from the sliced shark. The efficiency of 0.5% cysteine at pH 7.0 in removing mercury from minced shark was 40–45% (dry material), obtained by two of the three methods studied. This removal rate was considered relatively low for it failed to attend to the practical proposal of decontaminating species of fish highly contaminated by mercury. The need for fuller understanding of the mechanisms involved in the removal of mercury by cysteine was also considered.

Optimization of nitrogen recovery in the enzymatic hydrolysis of dogfish (Squalus acanthias) protein. Composition of the hydrolysates

The recovery of nitrogen in the enzymatic hydrolysis of dogfish shark muscle was optimized by the use of response surface methodology. The optimum values for enzyme/substrate ratio, temperature and pH were found to be 3.7% (w/w), 55.3°C, and 8.3, respectively. The dogfish protein hydrolysate produced under these conditions contained a high crude protein concentration (>85%), and its high nutritional value was indicated by the presence of all essential amino acids, and by high PER values. These results indicate the potential for dogfish protein hydrolysate to be used in lieu of vegetable proteins as a protein supplement in foods.

Protein Dispersions and Hydrolysates from Shark (Isurus oxyrinchus)

Manually-deboned muscles of shark (Isurus oxyrinchus) were ground and then washed sequentially with water, 0.5% NaCl and 0.5% NaHC03 solutions. Washed myofibrillar proteins were dispersed in water and then acidified. Dispersions so obtained were stable to heat treatment at 100°C followed by centrifugation at 5000 x g, as approximately 90% of proteins remained in solution. The acidified dispersions had low solubility in the pH range of 5 to 8, but were highly soluble under other pH conditions. Apparent viscosity of dispersions was dependent on temperature, pH and protein concentration. The amino acid composition and calculated protein efficiency ratio (PER) of washed proteins were similar to that of the original meat; howevcr, over 85% of free amino acids were removed upon aqueous washings of the meat. Hydrolysates obtained via an Alcalase-assisted process from the original shark muscles or washed myofibrillar proteins exhibited unique functional characteristics with respect to their water-holding capacity...

ETB-type receptors mediate endothelin-stimulated contraction in the aortic vascular smooth muscle of the spiny dogfish shark, Squalus acanthias.

Using various agonists, and the specific antagonist BQ-123, we have examined the sensitivity to endothelin of the vascular smooth muscle of the ventral aorta of the spiny dogfish shark, Squalus acanthias. Human endothelin-1 produced significant contraction of isolated vascular smooth muscle rings, with an EC50 of 10 nmol.l-1. The presence of an intact endothelium did not alter this response but the magnitude of the contraction was greater in rings with an intact endothelium. The response to 0.2 mumol.l-1 endothelin-1 was equivalent to that of 0.1 mmol.l-1 acetylcholine, and significantly greater than that to 80 mmol.l-1 KCl, suggesting high sensitivity even to the heterologous, mammalian peptide. The Hill plot of the contractile response was a straight line with a slope of 1.12, indicating that a single receptor was mediating the response. Endothelin-1, endothelin-3, and sarafotoxin S6c produced similar concentration-response curves, and the response to endothelin-1 was insensitive to the ETA-specific inhibitor BQ-123. Our data are consistent with the hypothesis that the receptor involved in the contractile response to endothelin of shark aortic vascular smooth muscle is of the ETB-rather than the ETA-type.

Lipids of cartilaginous fish: Composition of ether and ester glycerophospholipids in the muscle of four species of shark

The levels and hydrocarbon chain distributions of alk-l′-enyl-acyl, alkyl-acyl and diacyl subclasses of choline glycerophospholipid (GPC) and ethanolamine glycerophospholipid (GPE) in the muscles of four species of shark were investigated. The prominent subclasses in the EGP fraction were 1-O-alk-1′-enyl-2-acyl-sn-glycero-3-phosphoethanolamine (alk-l′-enyl-acyl-GPE) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (diacyl-GPE), accounting for 24.8% to 54.4% and 40.8% to 69.4%, respectively, of the total glycerophospholipids. In the GPC fraction, 1,2-diacyl-sn-glycero-3-phosphocholine (diacyl-GPC) was the most prominent subclass, ranging from 73.2% to 94.7% in the total glycerophospholipids. The levels of 1-O-alkyl-2-acyl-sn-glycero-3-phosphoethanolamine (alkyl-acyl-GPE), -phosphocholine (alkyl-acyl-GPC) and alk-l'-enyl-acyl-GPC were below 15% in the corresponding subclasses. The prominent alk-l'-enyl and acyl chains of the alk-l′-enyl-acyl-GPE were 16:0 (42.3 to 63.4%), 18:1 (10.0 to 30.0%) and 18:0 (5.7 to 10.9%) alk-l′-enyl chains, and 22:6n-3 acyl chain (48.8 to 75.7%). In the alkyl-acyl-GPE fraction, the prominent alkyl and acyl chains were similar to those of the alk-l′-enyl-acyl-GPE, but the levels of alkyl and acyl chains with 16 carbons were higher. The hydrocarbon chain compositions of alk-l′-enyl-acyl- and alkyl-acyl-GPC were also similar to those of the alkyl-acyl-GPE. The prominent acyl chains of diacyl-GPE and -GPC were 18:0, 16:0 and 22:6n-3, but the GPE fraction was richer in 18:0 acyl chain and the GPC fraction was richer in 16:0. These characteristics in alk-l'-enyl and alkyl chains of ether glycerophospholipids from shark muscles suggested that these muscles are suitable as sources of dietary ether-linked lipids for a certain disease that prints syndrome of deficiency in ether-linked lipids.

Thermal Stability and Gel‐Forming Ability of Shark Muscle as Related to Ionic Strength

ABSTRACTThermal stability and gel‐forming ability of silvertip, hammer‐head and thresher shark as affected by ionic strength were investigated. Low temperature endothermic peaks (LTEP, between 30 and 44°C) were observed in differential scanning calorimetric (DSC) thermograms of the shark muscles and surimi samples. Increases in ionic strength reduced the thermal stability of surimi as shown by depression of transition temperature, denaturation enthalpies and LTEP. Although gel strength of heat‐treated surimi increased with increasing NaCl concentration, the three species had different sensitivities to ionic strength. The highest NaCl‐induced gel‐forming ability of surimi was achieved at 0.5M salt concentration for silvertip and thresher; at 1.0M for hammer‐head shark.