• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.79-85
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• 2015

Three specimens of larvae (5.2~7.8 mm in standard length (SL)), of the family Scombridae, were collected from the southeastern waters off Jeju Island in August, 2014. These specimens were identified to Katsuwonus pelamis have melanophores distributed on the 1st dorsal-fin spines and post ventral margin on caudal peduncle. An analysis of the cytochrome oxidase submit I (COI) sequences (652 base pairs) of mitochondrial DNA showed that our specimens must be K. pelamis, because their sequences were concordant with those of the adult K. pelamis (genetic distance= 0.000~0.002), followed by Auxis rochei (genetic distance= 0.061~0.063) and Euthynnus affinis (genetic distance= 0.077~0.079). During the larval stage, K. pelamis differed from Thunnus spp. species in melanophores distribution period of 1st dorsal-fin spines, lower jaws and ventral margin on caudal peduncle. In conclusion, occurrence of K. pelamis larvae means Korean waters are potential spawning ground of K. pelamis.

• Proceedings of the Korean Society of Life Science Conference
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• 2001.09a
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• pp.95-95
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• 2001

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.489-497
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• 2015

To reveal the spatial and temporal variability in the distribution, growth, and maturation of skipjack tuna Katsuwonus pelamis in the western tropical Pacific, we compared two El $Ni{\tilde{n}}o$-Southern Oscillation (ENSO) signals and the sea surface temperature (SST) in the main fishing area with fishery and biological data. An index of skipjack tuna distribution was calculated using Korean purse seine fishery data from 1985 to 2003. Biological data for skipjack tuna were collected monthly from Korean catches during the 1994-2003 period. The catch was more closely related to the SST in the main fishing area than to the ENSO signals. However, cross-correlated function analysis showed delayed interactions between abiotic and biotic factors. The El $Ni{\tilde{n}}o$ events preceded the eastward movement of the fishing center by 2-3 months. El $Ni{\tilde{n}}o$ had a positive effect on the skipjack tuna catch, and the change in the Southern Oscillation Index (SOI) preceded the catch fluctuation by ca. 5-7 months. In addition, negative El $Ni{\tilde{n}}o$ effects on gonad maturation and the mean length of skipjack tuna were detected with time lags of 12 and 7 months, respectively. The length frequency indicated that the regime-specific growth pattern at each discrete period seemed to be related to the ENSO.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.473-480
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• 2017

We investigated the nutritional characteristics of the uncooked Skipjack tuna Katsuwonus pelamis frame (U-STF) as a basic resource for preparing flavor-enriching concentrates. The bone rate based on the fish frame (FF) was 53.2% in U-STF, thus lower than those of cooked skipjack tuna frame (C-STF), the uncooked salmon frame (U-SF), and beef leg bone (BLB). The composition of FF had 48.6-58.0% moisture, 18.4-21.3% crude protein, 7.0-15.0% crude lipid, and 12.8-22.1% ash. Compared to the proximate composition of BLB, that of FF was higher moisture and crude protein but lower solids, crude lipids, and ash. The total amino acid contents of FF was 17.6-20.8 g/100 g, which was higher than that of BLB. The levels of calcium and phosphorus of FF were 4.7-8.5 g/100 g and 2.4-4.2 g/100 g, respectively, thus lower than those of BLB. The brix concentration of FF extract was $5.0-8.2^{\circ}$, being highest in U-STF extracts, followed by extracts of U-SF and then extracts of C-STF. Our results indicate that U-STF is an optimal resource for preparing flavor-enriching concentrates.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.12-17
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• 2014

The cooling of precooked skipjack Katsuwonus pelamis is a critical thermal process in tuna canning because it affects the quality and yield of the canned tuna, as well as productivity. The combined method of vacuum cooling followed by water spraying (VC-WS) was investigated to increase cooling rates, and prevent loss of yield of the precooked tuna during vacuum cooling. For VC-WS, the precooked skipjack was cooled to $30^{\circ}C$ by vacuum at 31 mmHg and then wetted by spraying water for 2 min. The effects of VC-WS on cooling times, cooling loss, color, texture and lipid oxidation of the precooked tuna were compared with conventional spray cooling (SC).The cooling times for precooked skipjack from $75^{\circ}C-30^{\circ}C$ were 11 min for VC-WS and 145 min for SC. The cooling losses were 1.7 % for VC-WS and 1.6 % for SC. Peroxide and thiobarbituric acid (TBA) values of VC-WS were lower than those of SC. The loin of the VC-WS-treated skipjack was brighter and harder than the SC loin, as indicated by higher lightness and hardness values. Based on these results, we believe that the VC-WS process could compensate for the cooling loss of vacuum cooling and minimize changes in quality that occur during cooling of precooked skipjack tuna.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.3
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• pp.377-385
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• 2015

The age and growth of the skipjack tuna Katsuwonus pelamis were determined using otoliths sampled from a Korean tuna purse seine fishery in the Western and Central Pacific Ocean from January 2005 to September 2006. A total of 312 otoliths were used to estimate the ages of skipjack tuna, which ranged from 1 to 7 years. The relationships between otolith ring radius (R) and fork length (FL) for female, male, and sex combined were FL = 19.74R + 1.50 ($r^2=0.54$), FL = 17.66R + 6.35 ($r^2=0.47$), and FL = 18.83R + 3.36 ($r^2=0.53$), respectively. The back-calculated fork lengths of each age ($FL_{year}$) were $FL_1=36.2cm$, $FL_2=43.3cm$, $FL_3=48.3cm$, $FL_4=52.6cm$, $FL_5=56.5cm$, $FL_6=60.8cm$, and $FL_7=63.2cm$. The relationships between fork length (FL) and total weight (TW) for female, male, and sex combined were $TW=0.00001FL^{3.19}(r^2=0.95)$, $TW=0.00001FL^{3.17}(r^2=0.95)$, and $TW=0.000009FL^{3.23}(r^2=0.95)$, respectively. The von Bertalanffy growth parameters of skipjack tuna estimated in this study were $L_{\infty}=77.4cm$, K = 0.176/year, and $t_0=-2.569years$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.6
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• pp.776-784
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• 2014

Tuna cooking juice concentrate (TCJC) is by-produced during the canning processing of skipjack tuna Katsuwonus pelamis and it is well known that TCJC contains various nutritional components. Therefore, the immuno-stimulating activity of TCJC was investigated using macrophage RAW 264.7 cell line and the spleen cell isolated from BALB/c mice. The TCJC increased the production of IL-6, TNF-${\alpha}$, and IL-$1{\beta}$ in a dose-dependent manner compared to the control in RAW 264.7 cells without any toxicity. In particular, the production of TNF-${\alpha}$ was increased over 300-fold. The production of both Th1 cytokine (such as IFN-${\gamma}$, TNF-${\alpha}$, IL-2, and IL-12) and Th2 cytokine (IL-4, IL-6, IL-10) was also increased by TCJC treatment in splenocytes. Moreover, the TCJC increased the splenocyte proliferation in a concentration-dependent manner compared to control. These results indicate that TCJC may enhance immune function by promoting various cytokine production.

• 한국수산학회:학술대회논문집
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• 2005.05a
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• pp.91-92
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• 2005

• Proceedings of the Korean Society of Life Science Conference
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• 2001.09a
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• pp.96-96
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• 2001

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.6
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• pp.635-639
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• 2012

Thawing is very important in tuna canning because it affects the yield and quality of the canned tuna, and productivity. The effects of vacuum thawing on the quality, yield, and thawing times of frozen skipjack were compared with conventional water immersion thawing. The time required to thaw frozen skipjack tuna (weight 2.5-3.0 kg) from $-10^{\circ}C$ to $-2^{\circ}C$ was 75, 60, and 37 min at a pressure of 17, 23, and 31 mmHg, respectively, corresponding to temperatures of 20, 25, and $30^{\circ}C$. The thawing time decreased with increasing pressure. Vacuum thawing shorten the thawing time by 58-80% compared with water immersion thawing at $20^{\circ}C$, and there was less difference between the core and skin temperatures than with water immersion thawing. No significant change in pH or histamine was observed according to thawing method, while the volatile basic nitrogen (VBN), trimethylamine (TMA), and K value were lower with vacuum thawing than water immersion thawing. Based on these results, we believe that vacuum thawing minimizes the biochemical and microbial changes that occur while thawing frozen skipjack tuna.