Optimized protocols of cold shock treatment for the induction of triploidy were developed in Pacific abalone Haliotis discus hannai. Time windows of polar body extrusions were analyzed and various technical parameters including initial treatment times, treatment temperatures (－1ºC, 1ºC and 3ºC) and treatment durations (10 to 24 min) were tested in order to develop the best combination(s) among parameters enabling the efficient blocking the polar bodies. Based on a series of tests regarding hatchability of embryos, normality of larvae and induction efficiency of triploidy, the most appropriate protocol to block the first polar body was proven to be the cold shock treatment at 1ºC for 14 min with an initial treatment at 11 min post insemination. On the other hand, the most efficient condition for blocking the second polar body was the cold shock at 1ºC for 14 min with an initial treatment at 25-27 min post insemination. Under these treatment conditions, larval yields of cold-shock treated groups relative to non-treated control groups were up to 70% with a fairly consistent triploidy rate up to near 100%. Efficacy and reproducibility of triploid induction were further validated under scaled-up conditions; however, the yield of triploid larvae was highly influenced depending on the gamete quality used. Results from this study could be a useful basis for developing the practical protocol for mass production of triploid seedlings in this abalone species.
This study was performed to determine the effect of marine algae and water temperature on dietary feeding of juvenile geoduck (Panopea japonica) There was a significant difference on daily feeding efficiency of geoduck depend on temperature. In particular, it was shown that an ingested algal concentration was higher at 10, 15, and 20℃ than 5 and 25℃ for 24 hours. Clearance rate and ingestion rate of geoduck was relatively high at 15℃, showing 30.19 ± 1.06 L/hr/g, 21.83 ± 2.04 × 105 cells/mL, respectively. When two marine algae, Isochrysis galbana and Tetraselmis suecica, were provided to geoduck, there were no significant differences on clearance rate (CR), absorption rate (AR), absorption efficiency (AE) (p > 0.05) However, filtration rate (FR) was high when feeding on T. suecica compare to I. galbana. In conclusion, this study suggests that feeding activity of geoduck is considered to be high at 15℃. In addition, both I. galbana and T. suecica are necessary for geoduck though there was no difference between feeding efficiencies except filtration rate.
In order to investigate the growth performance, triploid and diploid Pacific oysters, Crassostrea gigas, were introduced into the rack oyster farm on the tidal flat in Wando waters, Korea. No significant differences were observed in monthly growth performance but in total weight in August, 2017 with significant higher in triploid. Whereas a relatively higher specific growth rate was observed in triploid for shell height and total weight as much as 76% and 56% than diploid. This could be attributed to feeding behavior which digestive gland atrophy was much higher in triploid throughout the experiment period except August, 2017. The growth differences were also attributed to a difference of reproductive behavior that triploid, mostly male sex, can easily recover the loss of energy after spawning. No significant difference was observed in proximate composition and hydrolyzed amino acid composition, but more delicate studies required for tasty compound. A hardened triploid spat could be a good approach to introduce a tidal flat rack oyster culture in Wando, being avoid the unnecessary social confliction for fouling contamination for abalone culture in Wando, Korea.
With the increasing production of shellfish farming in Korea and neighboring countries, mountainous accumulations of waste seashells have become environmental problems. To recycle the waste seashells into any product, the first process step is to clean the dirt and other organic materials from the surface of the shells. The cleaning process should be effective and low cost in order for the final product to be commercially competitive and viable. In this paper, we report the cleaning effect of five different commercially and readily available and popular industrial and household cleaning chemicals on the surface of abalone shells: Finish, Quickclean, Chlorox, Metex TS-40A, and NaOH. The abalone shells were treated with the chemicals at 40 °C for 22 hours. All the chemicals removed effectively the organic layers in the inner and outer surfaces. Specially, we found that the NaOH solution removed the outer calcite regions preferentially than the inner aragonite region.
In parallel with the increasing consumption of cultured fishery products, securing the food safety for marine products is becoming a social problem. Among them, shellfish can cause food poisoning due to pathogenic microorganisms. The total pollutant loads were estimated as following: 10,004 tons/year in BOD, 2,371 tons/year in T-N, and 714 tons/year in T-P. Tidal current speed did not exceed 10cm per second within the survey period, the mean water temperature was 18.96 ± 5.51℃, the mean salinity 31.70 ± 1.34 psu, the mean pH 7.96 ± 0.13, the mean DO 6.50 ± 1.36 mg/L, and the range of mean COD was from 1.30 ± 0.63 to 2.77 ± 1.13 mg/L. Total coliform at <1.8-14 MPN/100mL, and fecal coliform at <1.8-7.8 MPN/100 mL was founded in the microbiological test. Physicochemical factors did not affect the variation of total coliform and fecal coliform. It is also needed to prohibit eating raw oysters when in excess of standards, to designate Goseong-man bay as an specialized area for oyster farming in order to shift floating fish cage and manage marine manufactures, or minimize pollution in development of Nampo port for oyster farming.
In this study, we examined bacteriological and toxicological safety of shellfish produced in the Narodo area from January 2015 to December 2017. The sampling stations for this study were composed of 3 stations for oyster and 2 stations for short neck clam. The range of total coliform, fecal coliform and E. coli levels for 62 oyster samples was < 18-3,500, < 18-230 and < 18-170 MPN/100 g respectively. That for 72 short neck clam samples was < 18-5,400, < 18-330 and < 18-220 MPN/100 g respectively. And Salmonella sp. and Shigella spp. were not detected in all samples. Also paralytic shellfish toxin was not detected and diarrhetic shellfish toxin was detected below the limit of quantification. These results indicate that shellfish produced in Narodo area meets the standard of shellfish hygiene of Food Sanitation Act and assessed to be the Grade A of EU criteria.
We conducted a preliminary study on the bay scallop Argopecten irradians aquaculture in two different culturing sites (Changri and Tangae) of Cheonsu bay, West Sea in 2017. Water temperature during the culturing period (July to December) was 6.2-27.9℃. Water quality and nutrients (NH4-N, NO2-N, NO3-N, Total nitrogen, PO4-P, SiO2-Si) from surface water were satisfactory for bay scallop culture. During the growing period (July to November), dominant phytoplankton species were Cryptomonas sp. in both sites. Biomass of phytoplankton was the highest in July, but it was low in other period of both sites. Final survival rates of cultured scallop in Changri and Tangae were 79.58 ± 4.00% and 74.86 ± 2.66%, respectively. In Changri, mean daily growth rates (DGR) for shell length and total weights were 0.176 mm/day and 0.085 g/day, respectively. In Tangae, mean DGR for shell length and total weights were 0.248 mm/day and 0.160 g/day, respectively. These results suggest that Cheonsu bay is suitable for the aquaculture of bay scallop and growth was more satisfactory in outer site than inner site of this bay.
Two provinces of Korea, Jeonnam (J-site) and Gyeongnam (G-site), take longline systems for the Pacific oyster Crassostrea gigas aquaculture. The two sites, however, differ in the system deployment and operation. We monitored growth performances of the two oysters from May to November, 2018, together with environmental variables in waters and sediments. J-site system was characterized by higher culture density and earlier seed load. In the comparison of growth performance, survivals were highly comparable, but growths differed. The earlier load of seeds in J-site made the oysters grow faster in first two months, particularly in shell length, shell width, and meat weight. The difference, thereafter, became clearly narrowed due to retarded growth in J-site, even though it was still statistically different at P < 0.05. Of all the environmental variables monitored, chlorophyll-a, dissolved oxygen, and suspended solid were less favorable for J-site oysters while still being remained in levels allowable for the oyster aquaculture. Higher culture density appeared to be an additional factor responsible for the retarded growth of J-site oysters. However, we might need further studies covering expanded years and locations to generate realistic information representing the oyster growth performance for each site.
This study describes the reproduction characteristic in net cage cultured abalone, Haliotis discus hannai in Wando on 2016 and 2017. Sex ratio analysed female significantly higher than male (1:0.79-0.81). The spawning period was July to September on summer breeders. Atretic follicles were observed every month and the rate of occurrence was high at late active and ripe stage (from April to September). It is suggested that spawning disruption is caused by atretic follicle.
Although Manila clam, Ruditapes philippinarum, is one of the most economically important marine bivalves in the west coast of Korea, profitability of the clam business has reduced recently because of a shortage of seed clam supply. Thus, this study intended to secure wild spats in clam beds by developing suitable substrates for a spat collector on which Manila clam spats adhere. For this, 10 substrates were individually placed into 2 L onion bags and were deployed in Hajeon clam bed and Gomso port, in Gomso Bay on the west coast of Korea. The spat collectors were designed to suspend in water by buoys during high tide. About 3 months later, Manila clam and other bivalve spats were identified and counted by morphological and molecular diagnoses. The number of Manila clam spats on each substrate varied from 12 to 153 and 17 to 728 in Gomso port and Hajeon clam bed, respectively. The highest number of manila clam spats were collected on a sun shade mesh sheet. The size and total weight of the Manila clam spat averaged at 2 mm and 5 mg, respectively. Our study showed that the sun shade mesh sheet is the most efficient substrate for Manila clam spat collection, but a nursery growing technique after spat collection is needed to develop for the use of the spats for grow out because spats collected are not sufficient size in the region.
The Ministry of Oceans and Fisheries(MOF) and Marine Biodiversity Institute of Korea(MABIK) have initiated a project on a trial basis dedicated to improve the existent Korean names of 60 species and to add names to 20 species that are currently without Korean names. In collaboration with the MOF and MABIK, the Malacological Society of Korea also joined the project, specifically to correct the names of 7 species of mollusks from the species mentioned above. Based on the morphological characteristics of these species, five species have unanimously received new Korean names. Due to two compelling opinions, however, the final names for the remaining two species were determined by results from a public preference survey. Through this process, Diodora sieboldii with the Korean name 'Siboltsatgatjogae' is now called 'Gyeopjibunggumeongsatgatjogae', named after its distinctive features a double layered roof and a hole.
