ISSN : 1225-3480
Growth-line analysis was carried out on 221 hard clam (Meretrix petechialis) from the Bronze Age Konam-ri Shell Midden B-4, Anmyeon Island, Korea, to determine the seasonality of the clam collection and site occupation. Growth increments and the marginal index (MI) of the specimens were examined. And then the marginal index was compared to the monthly MI of modern specimens under the assumption that the growth pattern was the same as it is today. MI of the archaeological specimens ranged from 0.050 to 1.65 and was divided into four categories: < 0.63, spring; 0.63-0.76, summer; 0.76-0.89, fall; ≧ 0.89, winter collection. As a result, 193 specimens (87.33%) of 221 specimens represented spring, 14 (6.33%) summer, 6 (2.71%) fall and 8 (3.62%) winter collection. These results show that the collection of the clam at the Konam-ri Shell Midden during the Bronze Age could be carried out year-round, especially with an emphasis on spring.
In order to investigate the effect of stocking time on the growth performances, the oyster, in a density of 100 individuals per bag, introduced into rack culture farm on Wando tidal flat at three different time, April 2011 (APR-11), June 2012 (JUN-12) and November 2012 (NOV-12), respectively. In APR-11 and NOV-12, the growth of oysters was, with an initial size of 20 g in total weight and 3-5 cm in shell height, reached to commercial size over 80 g in total weight within 6-8 months. Regardless of stocking time, the crash season from summer mortality began in June, which difference between air and surface seawater temperature become increasing. Age or size dependent mortality was observed by 20-30% for 1-year-old oysters (APR-11), and 70-80% for 2-year-old oysters (NOV-12), respectively. Because of the stresses from transfer handling in hot summer season and direct impact of typhoons in 2012, JUN-12 did not reached to commercial size throughout the experimental period. Our data indicated that stocking time is one of the most important cultural practices for strategic approach to achieve the successful oyster farming of rack culture. In Wando, to avoid disastrous mortality, it is not recommend for 2 year old oysters to be exposed by oversummering for more growth.
In the present study, a violet blanket octopus, Tremoctopus violaceus Chiaje, 1830, was collected for the first time in Korea. This species is widely distributed in tropical and subtropical oceans. To data, only a single Tremoctopus species, Tremoctopus gracilis (Souleyet, 1852) has been reported from Korean waters. In the case of T. violaceus, there is insufficient evidence to register it as a domestic species because the mobility and migratory characteristics of octopus have not been confirmed. Herein, we provide the morphological characteristics of T. violaceus with mitochondrial cytochrome c oxidase I (cox1) partial sequence.
The habitat of the Manila clam (Ruditapes philippinarum) was assessed using habitat suitability index (HSI) factors considering growth (Chlorophyll a, Hydrodynamics), survival (Sediment-sand, Exposure time) and water- environment (Dissolved oxygen, Salinity). As a result, data layer assessed Manila clam habitat, it was possible to calculate the preferred area. Consequently, it was found that areas which seemed to prefer for Manila clams (HSI > 0.5) covers 1.23 km2 (Weight) out of 5.32 km2 and (HSI < 0.5) covers 4.09 km2 (Weight) out of 5.32 km2. Based on these results, it is estimated that Manila clams preferred habitat can be distinguished in areas other than the Boryeong tidal flat. Additionally, continuous environmental monitoring will have to be carried out for habitat management of tidal flats, and it is expected that these studies will develop habitat-based evaluation methods.
In Korea, Ellobium chinense is one of the well-known small, air-breathing snails, and was registered as the endangered species in 2005. The number of E. chinense populations has rapidly declined in recent years. In this context, genetic information of E. chinense is needed for species conservation in the future. However, the registered genetic information of E. chinense in NCBI is only 55 nucleotides and 53 proteins. Thus, we sequenced an E. chinense cDNA library using the Illumina platform, and selected arginine kinase (AK) gene which has been used as a molecular phylogenetic marker. AK sequence of E. chinense was analyzed through bioinformatic programs, and the biological importance of E. chinense was discussed in conjuntion with molecular phylogenetic trees.