In September and October 2020, combined acoustic and trawl surveys were conducted in the northwestern sea of Jeju Island. In the survey area, a region, so called Jeju region, was designated to esimate the biomass of chub mackerel and jack mackerel using a trawl survey method and frequency difference method. In the September survey, the weight ratios of jack mackerel and chub mackerel to the total catch were 24.6% and 2.8%, respectively, and in the October survey, those ratios were 24.9% and 20.7%, which were used to calculate their biomass (trawl survey). Using the frequency difference range (–8 to –3dB) corresponding to two species in 120 and 200 kHz, their biomass was estimated (frequency difference method). As a result, the biomass of two species from the trawl method was 3252.3 tons in September and 5777.0 tons in October. The estimated biomass by the frequency difference method was 4926.6 tons in September and 7521.5 tons in October. It was the first trial to estimate the biomass of two species using the trawl and frequency differencing methods in South Korea although there were some differences between two methods. In addition, horizontal distributions of acoustic backscattering strength over the entire survey area were mapped.

In this study, Target strength for multi-frequency (38 kHz, 70 kHz, 120 kHz and 200 kHz) of chub mackerel (Scomber japonicus) was estimated using by the KRM model. The body shape of the Chub mackerel was described by an X-ray system and the body length of 20 individuals ranged from 16 cm to 28 cm. The swimbladder tilt angle ranged between – 8 and – 14°, the maximum TS value according to the swimming angle of chub mackerel was – 33.0 dB at – 11°. The averaged TScm according to fork length was – 66.02 dB at 38 kHz, – 66.50 dB at 70 kHz, – 66.00 dB at 120 kHz and – 67.35 dB at 200kHz, respectively.

The purpose of this study is to compare short-term price predictive power among ARMA ARMAX and VAR forecasting models based on the MDM test using monthly consumer price data of frozen mackerel. This study also aims to help policymakers and economic actors make reasonable choices in the market on monthly consumer price of frozen mackerel. To analyze this study, the frozen wholesale prices and new consumer prices were used as variables while the price time series data were used from December 2013 to July 2021. Through the unit root test, it was confirmed that the time series variables employed in the models were stable while the level variables were used for analysis. As a result of conducting information standards and Granger causality tests, it was found that the wholesale prices and fresh consumer prices from the previous month have affected the frozen consumer prices. Then, the model with the highest predictive power was selected by RMSE, RMSPE, MAE, MAPE, and Theil’s inequality coefficient criteria where the predictive power was compared by the MDM test in order to examine which model is superior. As a result of the analysis, ARMAX(1,1) with the frozen wholesale, ARMAX(1,1) with the fresh consumer model and VAR model were selected. Through the five criteria and MDM tests, the VAR model was selected as the superior model in predicting the monthly consumer price of frozen mackerel.

Diet composition and trophic level of Trachurus japonicus were studied using 417 specimens collected by trawls, set nets and purse seine fisheries from March 2019 to February 2020 in the South Sea of Korea. The size of T. Japonicus ranged from 7.0 to 49.8 cm in total length. T. japonicus were a carnivore that fed mainly on euphausiids and pisces. In eddition, T. japonicus fed on small quantities of cephalopods, crabs etc. T. japonicus showed ontogenetic changes in feeding habits. The proportion of euphausiids decreased inversely proportional to body size whereas the consumption of pisces gradually increased. As body size of T. japonicus increased the mean number of prey per stomach and the mean weight of prey per stomach tended to increase, but the mean number of prey per stomach was not significantly different. As a result of the feeding strategy analysis, T. japonicus were specialized feeders with pisces and euphausiids as their dominant prey. The trophic level ranged between 3.57 ± 0.54 and 3.91 ± 0.65, and increased asymptotically with size of specimens. The average trophic level of the T. japonicus was 3.79 ± 0.61.

In this study, spray-dried double emulsion loaded bromelain was applied to Japanese Spanish mackerel fillets to develop fish-type, elderly-friendly foods. Japanese Spanish mackerel, treated with spray-dried double emulsions, were stored at 4oC for 24 h. For the characterization of emulsion particles, the particle size, ζ-potential, and morphology were determined. The color, TBARS, VBN, TMA, hardness, and adhesiveness of fish fillets treated by emulsion were measured for physicochemical properties. All the particle sizes of spray-dried emulsion were decreased while their double emulsion structure was maintained. Spray-dried emulsion reduced the color difference of fish fillets and did not catalyze lipid oxidation and protein decomposition. Values of TBA, VBN, and TMA of all fish did not exceed 0.5 mg MDA/kg, 30 mg/100 g, and 10 mg/100 g, respectively, which are considered edible limits regardless of bromelain or emulsion application. Bromelain modified fish fillets' hardness and adhesiveness to be suitable for elderly food, although it was encapsulated in the emulsion. Thus, spray-dried fish oil W/O/W double emulsion-loaded bromelain can be applied as a fish tenderizer, and this study’s results can be utilized to develop elderly-friendly food.

Recently, the annual emission rate of CO2 that is the main reason for domestic greenhouse gases is the third highest globally, which means it is an extremely serious issue. It is considered that these greenhouse gases affect climate changes. Especially, the emissions of CO2 in the fishing industry are nearly 4.11 million tons each year, occupying 0.7 percent of domestic total emissions. Therefore, this study clearly analyzed fuel consumption of major fish species over the recent five years focusing on large purse seines. It was revealed that mackerels occupied 55.7 percent of total fish catches of large purse seines and 57.5percent of total fishing earnings. Also, fuel consumption was 236.62 liters per ton caught and 179.51liters per million won earned.

본 연구는 근해에서 잡은 고등어의 신선도유지효과를 확인하기 위해 해수 슬러리얼음(SS), 해수 큐브얼음(SC), 수돗물 슬러리얼음(TS), 수돗물 큐브얼음(TC)에 저장하며, 신선도분석을 시행하였다. 각 얼 음 성분 중 세균수는 음용수 기준 이하였고, 암모니아성 질소는 해수 기준치인 11 mg/L를 초과했다. 민물에 비해 바닷물의 탁도가 심했다. 고등어의 일반성분 분석결과 수분 함량이 72.7%, 단백질 20.5%, 지질 5.25%, 회분 함량이 1.3%로 나타났다. 해수 슬러리 얼음은 수돗물 얼음과 비교하여 pH가 낮게 유지되었다. 저장 초기에는 모든 저장소에서 VBN 증가가 억제되었다. 전반적으로 해수빙이 담수 얼음보다 휘발성 염기질소(VBN) 값이 낮게 유지 되었다.

The purpose of this study was to develop an indirect enzyme-linked immunosorbent assay (indirect ELISA) based on a monoclonal antibody (MAb) that is specific to mackerel thermal stable-soluble protein (TSSP), that can be used for the rapid detection of mackerel in processed marine foods. Among the four MAbs (3A5-1, 2, 9, and 12) developed in previous studies, the 3A5-2 MAb that showed high specificity and sensitivity were selected and used to develop the indirect ELISA method. The detection range of the indirect ELISA was 0.02%-0.001% and the detection limit of 0.001% was shown. No cross-reaction to other marine products and food ingredients was observed by the indirect ELISA. Processed marine foods containing mackerel with ≥ 0.3 O.D. value at 405 nm were estimated as positive samples by the indirect ELISA. Therefore, the indirect ELISA can be used as a rapid and sensitive method to identify mackerel authenticity and adulteration in processed marine foods.

The age and growth of Pleurogrammus azonus in the coastal of Gangwon-do, East Sea were determined, from monthly samples of commercial catches, caught by the gill net and set net fishery from January to December in 2008. Gonadosomatic index (GSI) began to increase in September, and reached the maximum between November and December. After spawning GSI began to decrease from January. The annuli of P. azonus are formed once a year, with the boundary between opaque and translucent zones forming from December to January. The relationships between fork length (FL) and body weight (BW) were BW = 0.005 FL3.240(R2 = 0.963) for females and BW = 0.006 FL3.238(R2 = 0.946) for males. The FLs at annuli formation in otoliths were back-calculated from the otolith-length relationship and were adjusted to von Bertalanffy growth curves to FLt = 70.54 (1–exp(-0.099(t+1.188))) for females and FLt = 51.87 (1–exp(-0.135(t+1.697))) for males. Until the age of 3 years, males grew faster than females; however, from the age of 4 years, females grew faster than males. In the future, we want to study the relationship between early growth and water temperature changes in the East Sea