Juvenile Shellfish Research Articles

Inventory of Pests and Parasites in the Cultivation of Hotate Shellfish (<i>Patinopecten yessoensis</i>) in Funka Bay, Hokkaido, Japan

Hotate Shellfish Cultivation is the largest shellfish cultivation in the world, but many pests and parasites are found. This research aims to inventory the types of pests and parasites found in the cultivation of Hotate Shellfish (Patinopecten yessoensis) in Funka Bay, Hokkaido, Japan. The objects used for this research were 54 Hotate shellfish, consisting of three life stages of shellfish, namely seed shellfish, juvenile shellfish, and adult shellfish. This research was carried out using observation and random sampling methods to determine the types and percentages of pests and parasites present during the research. This research was carried out for seven months from 13 April to 6 December 2022 at the Daisan Matsui Company, Ohama, Oshamambe, Hokkaido, Japan. The results of this research show that there are four types of pests, namely Starfish, Purple Shellfish, Crustaceans, and Sea Pineapples as well as two types of parasites, namely Annelid Worms and Barnacles which attack shellfish cultivation. The percentage of shellfish at three life stages that were attacked by parasites was 75.93%. There are several factors that control the attachment of pests and parasites, including substrate availability, nutrient availability, and environmental considerations. The surfaces and nutrients provided by hotate culture facilities provide adequate conditions for pest settlement and growth.

First simultaneous assessment of macro- and meiobenthic community response to juvenile shellfish culture in a Mediterranean coastal lagoon (Thau, France)

Abstract Shellfish aquaculture has the potential to alter benthic assemblage composition with subsequent modifications of ecosystem functioning. While the impacts of aquaculture on the taxonomic structure of macro- and — to a lesser extent — meiofauna, have been widely studied, the functional changes of these communities remain relatively unknown. The recent development of biological trait analysis (BTA) has made it possible to produce information about how ecosystem functioning could change across specific terrestrial or aquatic system. In the present study, we used a BTA in parallel with standard taxonomic analysis to evaluate how well the two approaches detected the potential influence of juvenile oyster culture on the benthic community in the French Mediterranean Thau Lagoon. Two sites were sampled under farm structures and compared with two reference sites beyond the influence of farming. This study is the first detailed parallel description of macro- and meiofauna (nematodes). A total of 118 and 41 taxa were determined for macrofauna and nematodes respectively. Some taxa were more abundant or exclusively observed under farm structures such as Chaetozone gibber and Neanthes acuminata for macrofauna and Daptonema fallax and Anticoma eberthi for nematodes. Overall, our results indicate that biological traits and functional indices both detected the impact of shellfish culture on benthic assemblages, whereas macrofauna taxonomic indices revealed no difference. Our results thus suggest that trophic and ecological groups are particularly good indicators of the effects of shellfish culture. This study confirms the relevance of the functional approach, and more generally of multi-index approaches, to detect the influence of aquaculture on benthic communities. Further work is required to test multiple traits in different regions and under different systems, but this work paves the way for environmental impact assessment using a trait based approach.

Influence of organic components and inorganic components of reed as a concrete admixture

Vegetation in closed water area improves the natural environment by providing a habitat for juvenile shellfish and fish and by facilitating the intake of nutrients by plants. For these aquatic fauna, nutrient discharge occurs as mature individuals are harvested as fishery resources. However, aquatic plants are not typically harvested, so nutrients taken up by the plants as they grow return to the water in dead vegetation. These plants will not make a sustained contribution to the purification of the overall aquatic environment unless a system is developed to harvest them. In this research, we examine how reeds can be recycled. A potential application for the reeds is in mineral/chemical concrete admixtures. Reeds are rich in inorganic silica and organic lignin, both of which are effective as concrete admixtures. Silica is typically amorphous and is used as a pozzolanic admixture to impart long-term strength to concrete. Lignin is used as a water reducer admixture, which reduces concrete water content or slows the setting rate. The silica and lignin contained in the reed were examined from the viewpoint of strength development and flow of concrete. From the viewpoint of strength development, it was confirmed that long-term strength can be expected by replacing ashes of reeds with 5% of cement. Then, to improve mortar flow, reed powder was added to mortar as a water reducer at a weight fraction of 1% and was suitable in terms of phenol concentration. The results indicate that reed can be used as a chemical and physical concrete admixture.

Increased pCO2 changes the lipid production in important aquacultural feedstock algae Isochrysis galbana, but not in Tetraselmis suecica

Increased anthropogenic CO2 emissions are leading to an increase in CO2 uptake by the world's oceans and seas, resulting in ocean acidification with a decrease in global ocean water pH by as much as 0.3–0.4 units by the year 2100. The direct effects of changing pCO2 on important microalgal feedstocks are not as well understood. Few studies have focused on lipid composition changes in specific algal species in response to ocean acidification and yet microalgae are an indispensable food source for various marine species, including juvenile shellfish. Isochrysis galbana and Tetraselmis suecica are widely used in aquaculture as feeds for mussels and other shellfish. The total lipid contents and concentrations of I. galbana and T. suecica were investigated when grown under present day (400 ppm) and ocean acidification conditions (1000 ppm) to elucidate the impact of increasing pCO2 on an important algae feedstock. Total lipids, long-chain alkenones (LCAs) and alkenoates decreased at 1000 ppm in I. galbana. I. galbana produces higher lipids than T. suecica, and is perhaps as a result more impacted by the change in carbon available for lipid production under higher pCO2.I. galbana is an important feedstock, more easily assimilated for growth in juvenile shellfish and reductions in lipid composition may prove problematic for the growth of future shellfish aquaculture. Our findings suggest that higher pCO2 impacts on algal lipid growth are species specific and warrant further study. It is therefore vital to examine the impact of high CO2 on algal lipid production, especially those commercial shellfish feed varieties to predict future impacts on commercial aquaculture.

Growth of Tetraselmis suecica in a tubular photobioreactor on wastewater from a fish farm

Wastewater from a fish farm was remediated in a continuously operated tubular photobioreactor in which Tetraselmis suecica was cultured. The N and P removal efficiencies and the productivity of T. suecica growing on the wastewater were determined. Possibilities to optimize the productivity by adding extra orthophosphate were investigated. At a biomass concentration of 0.5 g L−1 on only wastewater, the N and P removal efficiencies were 49.4% and 99.0%, respectively. When extra phosphate was dosed to the wastewater, a 95.7% N removal efficiency and a 99.7% P removal efficiency could be reached at a biomass concentration of 1.0 g L−1. This also resulted in significantly higher average net volumetric productivity ranging from 0.35 g L−1 d−1 at a biomass concentration of 0.5 g L−1 to 0.46 and 0.52 g L−1 d−1 at biomass concentrations of 0.75 and 1.0 g L−1, respectively.This study shows the feasibility of an integrated multi-trophic aquaculture approach where wastewater from the fish farms is used to produce feed for juvenile shellfish at high productivity and constant quality.

First occurrence of the invasive tunicate Didemnum vexillum in eelgrass habitat

During the late 20th century, several species of alien tunicates invaded New England marine coastal waters. In Autumn 2008, we surveyed for tunicates in Lake Tashmoo, a protected marine pond with shellfish aquaculture operations and restored bay scallop Argopecten irradians irradians habitat on Martha's Vineyard, Massachusetts. We found the invasive tunicates Ascidiella aspersa, Botrylloides violaceus, Botryllus schlosseri, Didemnum vexillum, Diplosoma listerianum, Styela clava and native tunicate Molgula manhattensis attached to artificial substrates throughout Lake Tashmoo and B. violaceus, B. schlosseri, D. vexillum, D. listerianum and M. manhattensis attached to eelgrass Zostera marina in the middle of Lake Tashmoo. Tunicates were growing on the stalk and blade of in situ eelgrass, floating pieces of eelgrass (a transport and dispersal mechanism), and pieces of eelgrass in fouling communities on boat hulls and aquaculture floats. Botrylloides violaceus, B. schlosseri, D. listerianum and M. manhattensis have been previously recorded as utilizing eelgrass as substrate, but this is the first recorded occurrence of D. vexillum to utilize eelgrass as substrate. Perhaps because of lack of substrate space in Lake Tashmoo, D. vexillum spread to eelgrass. Eelgrass serves as a juvenile shellfish and fish habitat and threats to it are of concern by coastal managers and the fishing industry.

Burial, crawling and drifting behaviour of the bivalve Macomona liliana in response to common sediment contaminants

To investigate the effect of sediment contamination on the tellinid bivalve Macomona liliana, juvenile shellfish (about 1.3 mm long) were exposed to copper- and zinc-dosed sand, and sediments collected from several contaminated sites. The behavioural responses measured included burial rate, crawling and drifting. In copper-dosed sediment, a significant reduction in the number of shellfish burying after 10 min occurred at 25 mg Cu kg −1 (dry wt). After a 96-h exposure, shellfish crawled away from sediment with 10 mg Cu kg −1 (dry wt), and when a weak current was provided they left this 10 mg Cu kg −1 (dry wt) sediment by drifting. Zinc-dosed sediment slowed burial at 80 mg Zn kg −1 (dry wt), and stimulated crawling and drifting at 40 mg Zn kg −1 (dry wt). Some of the field-collected contaminated sediments slowed burial and stimulated drifting, but none affected crawling. It appears that juvenile drifting induced by sediment contamination could play a role in determining M. liliana distributions.