• 한국수산과학회지
• /
• 제54권1호
• /
• pp.73-79
• /
• 2021

The feeding habits of Chub mackerel Scomber japonicus were investigated using 329 specimens collected from coastal waters of the South Sea of Korea. S. japonicus is mainly a piscivore, consuming small fish such as Engraulis japonicus (%RI: 81.0 %). The diet of Chub mackerel also includes small quantities of thaliaceans, euphausiids, and amphipods. We calculated the trophic level as 3.92 for S. japonicus. The dietary composition of S. japonicus did not show significant differences with size, but differed with season. As the body size of S. japonicus increased, the mean weight of prey within the stomach (mW/ST) increased (One-way ANOVA, P<0.05).

• Proceedings of the National Institute of Ecology of the Republic of Korea
• /
• 제3권3호
• /
• pp.165-171
• /
• 2022

The Chinese crested tern (Thalasseus bersteini) is one of the most globally endangered species, listed as "Critically Endangered (CE)" on the IUCN Red List, with only approximately 30-49 individuals surviving in the wild. Chinese crested terns were discovered to breed in South Korea for the first time in 2016 while conducting a census on uninhabited islands. The Ministry of Environment has declared the breeding habitat of the Chinese crested terns as "Specified Island" to protect this CE species. However, brown rats (Rattus norvegicus) inhabiting the breeding grounds of the Chinese crested terns and Black-tailed gulls may potentially pose a threat to the breeding of these avian species. Therefore, we conducted a study on the feeding behavior of brown rats involving stable isotope analysis to determine their food sources. Fecal analysis showed that brown rats mainly fed on plants, whereas they scarcely fed on animals, such as insects. In addition, the stable isotope analysis showed that the δ¹³C values of brown rats, insects, and Indian goosegrasses were approximately -16 to -11‰, whereas the δ¹³C value of Chinese crested terns that obtained their food from the marine ecosystem was approximately -22 to -18‰. Hence, we conclude that the source of carbon for brown rats on this island is the terrestrial ecosystem. We ruled out the possibility of any direct prey-predator interaction between the brown rat and the Chinese crested tern or Black-tailed gull.

• 한국수산과학회지
• /
• 제55권3호
• /
• pp.345-352
• /
• 2022

In this study, the dietary habits of the spinyhead sculpin Dasycottus setiger were investigated based on 156 specimens collected seasonally between May 2018 and February 2019 from the East Sea off the Korean coast. In terms of the weight contribution (%W), the main food items of the spinyhead sculpin were found to be teleosts (33.5%), followed by carid shrimps (13.8%), amphipods (13.3%), cephalopods (12.0%), and polychaetes (7.1%). Dietary analyses based on the weight contribution of different prey taxa in the diet of the spinyhead sculpin revealed considerable variation in the dietary composition in terms of the sampling region and fish size implying intra-specific dietary segregation. The spinyhead sculpin showed a size-related trends in dietary shift from amphipods to carid shrimps and teleosts in northern region, and from carid shrimps and mysids to teleosts and cephalopods in middle eastern coast. Multivariate analyses of dietary changes revealed that the dietary composition of spinyhead sculpin is significantly associated with the sampling site, but not the fish size. Amphipods contributed more to the diets of the northern population, while mysids typified the diets of spinyhead scuplin inhabiting the middle eastern coast, indicating differences in available food resources between the two study regions.

• 한국수산과학회지
• /
• 제55권3호
• /
• pp.374-378
• /
• 2022

The feeding habits of the Glowbelly Acropoma japonicum were examined based on 849 specimens collected from the coastal waters of the South Sea of Korea. The total length (TL) of these specimens ranged from 2.6 to 13.0 cm. A. japonicum fed majorly on Euphausia pacifica (Euphausiacea, % index of relative importance; IRI, 51.9). However with growth, its diet shifted from copepoda to euphausiacea. Overall, as the body size of A. japonicum increased, the mean weight of prey within the stomach (mW/ST) increased.

• 한국수산과학회지
• /
• 제54권6호
• /
• pp.989-999
• /
• 2021

The sound of finless porpoises Neophocaena asiaeorientalis was recorded with an acoustic recorder to confirm their emergence in the South Sea of South Korea in February, June, and November 2020. Sea water temperature and salinity were also measured. In addition, a sighting survey was conducted to observe the behavior of the finless porpoises and the marine environment, and the clicks of the finless porpoises were recorded every day. The results showed that they always emerged in the survey area. The finless porpoises mainly foraged, whereas some played or rested. The water temperature range of areas where the finless porpoises emerged was 7.5-23.5℃. Assuming that the number of clicks corresponds to the number of finless porpoises, the finless porpoises emerged the most during spring. The emergence decreased during winter and was the lowest during autumn. The finless porpoises emerged more during the daytime than during the nighttime in all seasons, indicating a temporal difference in the usage of the survey area. This might be due to the movement of prey organisms according to regional characteristics. A long-term survey and research on habitat use and environment is needed to manage and conserve the finless porpoises.

• 한국수산과학회지
• /
• 제54권6호
• /
• pp.1052-1057
• /
• 2021

The diet composition of common flying squid Todarodes pacificus was studied using 1,084 specimens collected through trawl and jigging from June 2018 to June 2020 in the East Sea of Korea. The mantle length (ML) of the collected individuals ranged from 13.6 to 31.1 cm. Todarodes pacificus is a carnivore. In the study area, T. pacificus was observed feeding mainly on fish and cephalopods, in addition to small quantities of crustaceans. The calculated trophic level value for T. pacificus was 4.10. Small individuals (ML, <18.0 cm) mainly fed on cephalopods, while intermediate (ML, 18.0-23.0 cm) and large (ML, ≥23.0 cm) individuals fed mainly on fish and occasionally on cephalopods. Overall, as the body size of T. pacificus increased, the mean weight of the consumed prey increased (one-way ANOVA, P<0.05).

• 생태와환경
• /
• 제55권4호
• /
• pp.259-273
• /
• 2022

먹이망은 군집의 종구성과 종간 관계를 나타내줄 뿐만 아니라 먹이망을 구성하는 요소를 정량화하여 구조를 분석하고 이해하는 데 유용하다. 먹이망에 관한 연구는 군집의 영양 패턴, 피식자와 포식자 사이의 개체군 동태, 생태계 안정성, 생태계 내 물질/에너지 흐름 등의 이해에 도움을 준다. 먹이망 모델은 생태계 군집의 종간 관계 복잡성을 이상적으로 표현해 주며 자연 생태계에서 관찰된 유형에 대한 정보를 제공해주므로, 먹이망 모델은 대상 군집의 특성과 동태를 연구하는 도구로 사용될 수 있다. 본 연구에서는 국내외에서 사용되는 주요 먹이망 모델을 정적 모델과 동적 모델의 유형으로 구분하여 주요 모델의 특성과 적용 사례를 고찰하였다. 정적 모델로 Ecopath 모델이 많이 사용되고 있고 이는 동적 모델인 Ecosim과 연계되어 Ecopath with Ecosim으로 통합되어 사용되고 있다. 또한 동적 모델로 독성물질 특성 등의 영향을 분석하고자 하는 경우 AQUATOX 모델이 많이 사용되고 있다. 효율적인 먹이망 모델을 구축하기 위해서는 대상 생태계의 생물 요소들 사이의 섭식선호성 관계가 충분히 파악되어야 하고 또한 주요 환경인자들이 이들 생물에 미치는 영향에 대한 기초자료 수집이 필요하다. 효율적인 생태계 관리를 위해서는 환경변수만을 고려하는 관리가 아닌 환경과 생물 특성과 관계, 그리고 먹이망을 같이 고려하는 생태계 수준의 연구가 요구된다.

• Ocean and Polar Research
• /
• 제45권2호
• /
• pp.43-55
• /
• 2023

This study was conducted to understand the seasonal patterns and variation of the copepod community in the Anma Islands of Yeonggwang, Yellow Sea, with a focus on seasonal surveys to assess the factors affecting their occurrence. Throughout the survey period, Acartia hongi, Paracalanus parvus s. l., and Ditrichocorycaeus affinis were dominant species, while Acartia ohtsukai, Acartia pacifica, Bestiolina coreana, Centropages abdominalis, Labidocera rotunda, Paracalanus sp., Tortanus derjugini, Tortanus forcipatus occurred differently by season and station. As a results of cluster analysis, the copepod communities were distinguished into three distinct groups: spring-winter, summer, and autumn. The results of this study showed that the occurrence patterns of copepod species can vary depending on environmental conditions (topographic, distance from the inshore, etc.), and their spatial occurrence patterns between seasons were controlled by water temperature and prey conditions. One of the physical mechanisms that can affect the distribution of zooplankton in the Yellow Sea is the behavior of the Yellow Sea Bottom Cold Water (YSBCW), which shows remarkable seasonal fluctuations. More detailed further studies are needed for clear grounds for mainly why to many Calanus sinicus in the central region of the Yellow Sea are seasonally moving to the inshore, what strategies to seasonally maintain the population, and support the possibilities of complex factors.

• 한국해양학회지:바다
• /
• 제25권4호
• /
• pp.160-172
• /
• 2020

2014년 춘계에 독도 주변해역에서 전례없이 높은 개체수를 나타낸 야광충의 섭식특성을 이해하고자 야광충 식포 내 먹이생물의 조성과 출현량을 분석하였다. 출현 야광충 개체수는 4,328~17,791 inds.m^-3이었고, 야광충 식포 내 먹이생물 출현율은 평균 32%(24~50%)이었다. 관찰된 먹이생물의 조성은 분변립, 원생생물, 꽃가루, 규조류, 와편모조류, 요각류, 어란, 그리고 치자어로서 매우 다양하였고, 분변립의 출현율이 가장 높았다(43%). 원생생물(19%)과 꽃가루가 18%를 차지한 반면, 규조류와 와편모조류가 각각 7%와 4%를 나타냈다. 식포 내의 출현율을 근거로 분변립, 원생생물과 꽃가루가 어란, 규조류, 와편모조류 그리고 치자어에 비해 더 선호된 것으로 여겨졌다. 본 연구결과는 연구기간에 독도 주변해역에서 출현한 높은 개체수의 야광충이 기존에 알려진 먹이생물 규조류보다 다른 먹이생물과 관련이 높음을 의미하였다.

• ALGAE
• /
• 제39권2호
• /
• pp.109-127
• /
• 2024

High production and efficient harvesting of microalgae containing high omega-3 levels are critical concerns for industrial use. Aeration can elevate production of some microalgae by providing CO₂ and O₂. However, it may lower the production of others by generating shear stress, causing severe cell damage. The mixotrophic dinoflagellate Gymnodinium smaydae is a new, promising microalga for omega-3 fatty acid production owing to its high docosahexaenoic acid content, and determining optimal conditions and methods for high omega-3 fatty acid production and efficient harvest using G. smaydae is crucial for its commercial utilization. Therefore, to determine whether continuous aeration is required, we measured densities of G. smaydae and the dinoflagellate prey Heterocapsa rotundata in a 100-L semi-continuous cultivation system under no aeration and continuous aeration conditions daily for 9 days. Furthermore, to determine the optimal conditions for harvesting through centrifugation, different rotational speeds of the continuous centrifuge and different flow rates of the pump injecting G. smaydae + H. rotundata cells into the centrifuge were tested. Under continuous aeration, G. smaydae production gradually decreased; however, without aeration, the production remained stable. Harvesting efficiency and the dry weights of omega-3 fatty acids of G. smaydae + H. rotundata cells at a rotational speed of 16,000 rpm were significantly higher than those at 2,000-8,000 rpm. However, these parameters did not significantly differ at injection pump flow rates of 1.0-4.0 L min^-1. The results of the present study provide a basis for optimized production and harvest conditions for G. smaydae and other microalgae.