Background: The biological information of fish, which include reproduction, is the prerequisite and the basis for the assessment of fisheries. Methods: The aim of this work was to know the reproductive biology with the first sexual maturity (TL50) and the spawning period for 58 mainly fish species in the waters around La Réunion Island (Western Indian Ocean). Twenty families belonging to the Actinopterygii were represented (acanthuridae, berycidae, bramidae, carangidae, cirrhitidae, gempylidae, holocentridae, kyphosidae, labridae, lethrinidae, lutjanidae, malacanthidae, monacanthidae, mullidae, polymixiidae, pomacentridae, scaridae, scorpaenidae, serranidae, sparidae; 56 species; n = 9,751) and two families belonging to the Elasmobranchii (squalidae, centrophoridae; 2 species; n = 781) were sampled. Between 2014 and 2022, 10,532 individuals were sampled covering the maximum months number to follow the reproduction periods of these species. Results: TL50 for the males and the females, respectively, ranged from 103.9 cm (Acanthurus triostegus ) to 1,119.3 cm (Thyrsitoides marleyi ) and from 111.7 cm (A. triostegus ) to 613.1 cm (Centrophorus moluccensis ). The reproduction period could be very different between the species from the very tight peak to a large peak covered all months. Conclusions: Most species breed between October and March but it was not the trend for all species around La Réunion Island.

In order to understand characteristics on bycatch of Korean tuna purse seine fishery, especially operations associated with Fish Aggregating Device (FAD) in the Indian Ocean, we conducted analyses related to bycatch by school association type (unassociated school, FAD associated school and log associated school) using the data collected by scientific observers from 2016 to 2018. The FAD used by Korean tuna purse seine fishery in the Indian Ocean was a drifting FAD, which belongs to non-entangling FADs according to the category proposed by the International Seafood Sustainability Foundation (ISSF). The target species of Korean tuna purse seine fishery are skipjack, yellowfin and bigeye tunas, accounting for 99% of the total catch. The ratio of bycatch was 0.97% in total catch and the discard accounted for less than 1%, indicating that most catch was retained on board. In terms of bycatch ratio by school association type, it accounted for 0.12% for unassociated school, 1.09% for FAD associated school and 1.25% for log associated school. As for the catch proportion of shark species by school association type, it accounted for 0.01% for unassociated school, 0.11% for FAD associated school and 0.10% for log associated school, which showed that unassociated school type was the lowest to affect bycatch of non-target and shark species. Given the proportion of bycatch compositions, however, it is considered that FAD associated school of Korean tuna purse seine fishery has less caught bycatch species of non-target and shark, compared to other fleets operating in the Indian Ocean.

This study examines the changes of an interdecadal circulation over the Asian continent to find cause of the surface warming in Siberia from 1958 to 2004. According to our study, there is a coherency between a long-term change of sea surface temperature in the Indian Ocean and the rapid increase of air temperature in Siberia since 1976/1977. In this study, we suggest that mean wind field changes induced by the positive sea surface temperature anomalies of the Indian Ocean since 1976/1977 are caused of inter-decadal variations in a large-scale circulation over the Asian continent. It also indicates that the inter-decadal circulation over the Asian continent is accompanied with warm southerly winds near surface, which have significantly contributed to the increase of surface temperature in Siberia. These southerly winds have been one of the most dominant interdecadal variations over the Asian continent since 1976/1977. In addition, we investigated the long-term trend mode of 850 hPa geopotential height data over the Asian continent from the Empirical Orthogonal Function (EOF) analysis for 1958-2004. In result, we found that there was an anomalously high pressure pattern over the Asian continent, it is called 'the Asian High mode'. It is thus suggested that the Asian High mode is another response of interdecadal changes of large-scale circulations over the Asian continent.

This study standardized catch per unit effort(CPUE) of the Korean longline fishery, which has been used to assess the status of stock as an index of abundance, for bigeye and yellowfin tunas in the Indian Ocean. The Generalized Linear Model(GLM) was used to analyze the fishery data, which were catch in number and effort data collected each month from 1971 to 2007 by 5 × 5 degree of latitude and longitude. Explanatory variables for the GLM analysis were year, month, fishing area, number of hooks between floats(HBF), and environment factors. The HBF was divided into three classes while the area was divided into eight subareas. Although sea surface temperature(SST) and southern oscillation index(SOI) were considered as environmental factors, only SST was used to build a model based on statistical significance. Standardized CPUE for yellowfin tuna showed a declining trend, while nominal CPUE for the species showed an increasing trend.

본 연구에서는 인도양 해수면 온도의 변동성과 1970년 중 후반 이후 동아시아 여름 몬순의 변화의 상관성을 분석하였다. 전반기의 인도양 해수면 온도는 동아시아 여름강수편차(EASRA), 북서태평양 몬순지수(WNPMI)와 상관관계가 거의 없었지만 후반부에서는 인도양 전 부분에 걸쳐 상관관계가 크게 증가하였다. 인도양 해수면 온도와 동아시아 몬순과의 상관성 관계는 봄철과 여름철 각각 지역적으로 차이를 보였다. 봄철의 경우에는 적도 인도양을 중심으로 높은 상관성을 보인 반면 여름철의 경우에는 벵갈만 근처의 인도양에서 높은 상관성을 보였다. 인도양 해수면 온도의 수십년 주기의 변동성은 ENSO의 변동성보다 동아시아 여름 강수편차에 상관성이 높게 나타나고 있으며 따라서 ENSO보다도 인도양 해수면 온도의 변동성이 동아시아 여름몬순에 더 큰 영향을 줄 수 있다. 이러한 인도양 해수면 온도의 수십년주기의 변동성 차이(후반기 해수면 온도와 전반기 해수면 온도의 차이)를 모델의 강제력으로 주고 AGCM실험을 수행하여 그 결과를 비교하였다. 모델 실험 결과 실제 전 후반기 강수량의 차이 패턴인 동아시아 북부의 강수 감소, 한반도와 일본 남부의 강수 증가, 중국 남부의 강수 증가의 패턴이 보였다. 특히 8월의 북서태평양고기압의 확장으로 인한 강수의 증가는 실제 기후변화 차이를 나타낸다. 인도양 해수면 증가로 인한 모델상에서의 대기 순환은 벵갈만-인도양과 북서태평양의 상승기류 중심을 더욱 강화시키는 역할을 해주며 북서태평양에는 고기압성 기류를 강화시키고 동아시아 지역에서는 저기압성 기류를 강화시키는 역할을 한다. 또한 상승기류 중심을 북쪽으로 이동시킨다. 따라서 인도양 해수면 온도의 증가 효과는 동아시아 지역과 북서태평양 지역의 반대위상의 변화를 강화시키는 역할을 하고 있다. 인도양지역별 해수면 온도의 민감성 실험에서는 적도인도양의 강제력의 경우에 북서태평양 상승기류을 강화하여 동아시아 여름몬순에 영향을 주었다.

본 연구에서는 엘니뇨현상과 인도양 쌍극자 모드(Indian Ocean Dipole, IOD) 현상의 상호 관련성과, 우리나라 기온, 강수량에 대한 두 현상의 영향을 분석하였다. 1954년부터 2004년까지 51년간 NINO 3 지수, IOD지수, 그리고 전국 11개 지점 지역평균한 월별 평균기온과 강수량 자료를 사용하였다. 엘니뇨현상과 IOD현상은 봄과 가을에는 동시 상관관계가 존재한다. 인도양에서 해수면온도 분포는 엘니뇨 해에는 남북진동이, IOD 해에는 동서진동 형태가 뚜렷하였다. 엘니뇨 해 우리나라에서는, 여름철에 냉하다우, 겨울철에 온난다우 경향이 뚜렷한 반면에, IOD 해에는 유의한 상관성을 찾을 수 없었다. 대기대순환에서도 엘니뇨 해에는 우리나라를 포함한 중위도에 통계적으로 신뢰할 만한 편차패턴이 나타나지만, IOD 해에는 그렇지 않았다.