Culture Ropes Research Articles

Impacts of seeding density on the abundance and size of juvenile mussels and biofouling accumulation in Greenshell™ mussel aquaculture

Growth of the Greenshell™ mussel (Perna canaliculus) industry, New Zealand's most significant aquaculture sector, is limited by spat abundance in the early stages of the aquaculture cycle. However, there are few management techniques to improve spat production. Here, we tested the effects of seeding density (low: 257, mid: 515, and high: 1030 mussels per 10 cm of culture rope) – a putative method to manage spat seeding efficiency and yield – on the abundance and size of P. canaliculus spat at four depths at two sites in the Marlborough Sounds. We also recorded the abundance and size of blue mussels, Mytilus galloprovincialis, which are a problematic biofouling species, as well as the biomass and composition of the biofouling accumulating on mussel culture ropes under the same experimental treatments. Although the abundance of P. canaliculus was greatest at the highest seeding density (∼200 mussels per 10 cm of rope at 87 days), this seeding density also experienced the greatest losses. However, while fewer spat were lost from the low-density seeding treatment, the overall number of spat per 10 cm was significantly reduced, resulting in few operational gains in terms of biofouling reduction or spat size. Overall, the seeding density of suggesting that seeding density of ∼1030 spat per 10 cm of rope was the optimal density tested in this study and could be a useful target density for mussel farmers.

Seasonal Algal Host Shifts of the Symbiotic Amphipod Ceinina japonica Stephensen, 1933 (Amphipoda: Eophliantidae) in the Sea of Japan (East Sea)

The phenology of the alga-dwelling amphipod Ceinina japonica Stephensen, 1933 (Amphipoda: Eophliantidae) was studied at Rishiri Island, Hokkaido, Japan, from May 2016 to March 2017. Seasonal shifting between the host algal species was confirmed through observations at a coastal field site and a nearby aquaculture facility for kelp. Amphipods mainly occurred in the farmed biennial kelp Saccharina japonica var. ochotensis and wild algae Undaria pinnatifida, with Agarum clathratum, Costaria costata, Saccharina cichorioides, and Sargassum boreale as new host algal records. Amphipods occurred in sporophytes of U. pinnatifida at the field site from February to March and from May to July, but they were found in the kelp of S. j. var. ochotensis during the rest of the year, from August to the following January. Individuals of C. japonica infected sporophytes of the large brown alga Undaria pinnatifida from February to July, and C. japonica reproduced from July to September, a period during which the amphipods switch to a different host in July, the sporophytes of the saccharinan kelp S. j. var. ochotensis, where they stay until January. The amphipods then switched back to U. pinnatifida in January or February. Experimental evidence from a kelp-culturing facility also confirmed the timing of this host shift. The removal of U. pinnatifida from algal culture ropes in such facilities is suggested as a method to prevent amphipod damage, which is important for commercially farmed S. j. var. ochotensis.

Impacts of seeding density on the oxidative stress response of the Greenshell™ mussel, Perna canaliculus

The Greenshell™ mussel, Perna canaliculus, is the most lucrative aquaculture species in New Zealand; however, losses of commercial juvenile mussels (spat) are common and can drastically reduce the yield of adults. Modification of seeding density is a potential method to manage loss of spat (~ 1–20-mm shell length), by reducing biofouling and intraspecific competition. Understanding the stress responses of spat in production systems during the early stages of aquaculture is a high priority for mussel farmers who aim to manage and optimise mussel production. Here, the effects of seeding density (low: 257, mid: 515, and high: 1030 mussels 10 cm−1 of culture rope), space (depth, site), and time (December 2019 and February 2020) on oxidative stress responses (total antioxidant capacity [TAC] and lipid peroxidation [LP] biomarkers) in spat and their viability (freshwater immersion test) were assessed in the Marlborough Sounds, New Zealand. The effect of seeding density on TAC was variable among depths, sites, and times, whereas seeding density had no impact on LP. In late summer (February 2020), oxidative stress appeared to be higher compared to early summer (December 2019). This indicates that mussels were exposed to more stressful conditions later in summer, although this did not reduce their short-term viability. This research found that seeding density had no major impact on oxidative stress biomarkers and suggests that stress responses and viability of Greenshell™ mussel spat during the summer months are not affected by the seeding density levels measured in this study.

Effects of culture conditions (stocking density, water depth and aquaculture gear) on the aquaculture performance of a new Crassostrea angulata variety “Golden oyster#1”

Bivalve molluscs are a high quality animal protein source for humans, and the demand for farmed bivalves is increasing. Among the bivalve molluscs, the Portuguese oyster Crassostrea angulata, is one of the most popular species and is intensively farmed in warm water. In order to further increase the aquaculture yield of C. angulata through cost-effective farming practices, this study was conducted to evaluate the effects of stocking density, water depth and aquaculture gear on the aquaculture performance of C. angulata in the nursery and grow-out phases. The results of this study revealed that both stocking density and water depth affected the survival rate and growth rate of C. angulata in the nursery and grow-out phases. In the nursery phase, high stocking density reduced the survival rate, but was beneficial to the growth of C. angulata spats, while 1.5 m and 3 m were optimum for the survival and growth of C. angulata spats. In the grow-out phase, the use of lantern net/ rope culture, low stocking density with narrow substrate spacing and shallow water (1.5 m) were beneficial to the survival, growth and yeild of C. angulata. The results of this study can be used as a guide to further improve C. angulata aquaculture practices, and fill the knowledge gap on the effects of stocking density, water depth and aquaculture gear on C. angulata aquaculture.

Prospects and opportunities for mussel Mytilus trossulus farming in the southern Baltic Sea (the Gulf of Gdańsk)

In the Baltic Sea, where osmotic stress limits the growth of marine organisms, mariculture is driven primarily by the need to improve the status of the environment. To this end, several mussel farms have been attempted in selected areas, except the southern Baltic. The pilot culture of Mytilus trossulus was carried out with the use of a modified long-line system in the Gulf of Gdańsk in 2009–2012, providing the first evaluation of the mussel farming potential in this area. The growth rate of mussels (3.0–6.7 mm year-1) in the gulf was in the low range, but the mean wet biomass gain (1.50 kg m-1 normalized culture rope) was among the highest in the Baltic. After a two-year growth period, one tonne of mussels fixed in their soft tissues from 93 to 98 kg N t-1 and 11 kg P t-1. The cost-benefit analysis revealed a negative budget balance of production for human consumption, with a total income covering only 12.0% of the cumulative costs. Mussel farming in the gulf can therefore only be justified to improve the environmental quality if additional funding mechanisms are put in place to support farming activity.

Geographical variation in the carbon, nitrogen, and phosphorus content of blue mussels, Mytilus edulis

Shellfish farming contributes to nutrient removal in coastal and estuarine systems, as bivalves incorporate nutrients into their tissues and shells, which is removed from the marine system on harvest. Fourteen locations around the UK were surveyed to explore geographic variation in carbon, nitrogen and phosphorus content of tissue and shell in blue mussels. Phosphorus in tissue had a significant negative relationship with mean annual seawater temperature for both rope and bottom cultured sites. Per tonne of live mussel, rope culture removed significantly more nitrogen (8.50 ± 0.59 kg) and phosphorus (0.95 ± 0.07 kg) than bottom cultured (5.00 ± 0.013 kg nitrogen and 0.43 ± 0.01 kg phosphorus). Bottom culture, however, provides significantly more C removal in shell (60.15 ± 0.77 kg) than in rope cultured (46.12 ± 1.69 kg). Further studies are required to examine the effect of growth rate, on the nitrogen and phosphorus remediation, and carbon stored in shell, of rope culture and bottom cultured mussel aquaculture.

Culture of the seaweed, Gracilaria tenuistipitata in brackishwater pond as well as lagoon of Muttukadu, Chennai, Tamil Nadu

In this study, an attempt was made to standardise the method of culture of the seaweed Gracilaria tenuistipitata in brackishwater ecosystems. The species was selected as it is available in abundance due to its tolerance for a wide range of salinity, as seaweed culture in brackishwater ecosystem requires a suitable species which is adaptable and proliferating, An experiment was conducted to estimate the proliferation capacity of G. tenuistipitata with different methods of propagation viz., rope culture and net bag culture with different initial biomass intensity (50, 100 and 200 g m-1 in rope and 50, 100 and 200 g m-2 in net bag) in different ecosystems viz., lagoon and pond. The results showed that G. tenuistipitata proliferates in both lagoon and in pond ecosystem, with high SGR in rope culture compared to net bag method. With respect to different initial biomass intensity in rope method, there was no significant difference in specific growth rate (SGR) between 50 g m-1 (12.86±0.35%) and 100 g m-1 (10.94±0.34%) but it was significantly higher when compared to 200 g m-1 (6.14±1.1%) during 20 days of culture in lagoon ecosystem. It was also observed that SGR was significantly higher with 50 g m-2 (7.23±0.46%) when compared with 100 g m-2 (5.86±0.03%) and 200 g m-2 (5.64±0.02%) in net bag culture in pond ecosystem. Moreover, 20 days of culture showed significantly higher SGR with 50 and 100 g m-1 than 40 and 60 days of culture period in lagoon ecosystem. It can be concluded that rope cultivation of G. tenuistipitata with 50-100 g m-1 of initial biomass intensity was ideal in lagoon for 20 days of culture at brackishwater salinity regime of 19-25 ppt.

The current situation and environmental conditions of green mussel farming in the gulf of Thailand

This study investigated the current situation and environmental conditions of green mussel Perna viridis farming in Surat Thani, Phetchaburi and Samut Prakan provinces where were located in the gulf of Thailand. Samples were collected during April, August and November in 2014. Based on the results of this study, there were three major types of mussel culture patterns in Thailand: bouchot culture, longline culture (rope culture), and raft culture. Mussel farmers encountered problems on decreasing of larvae mussel in the water column, water quality degradation, high production cost and farmer’s lack of negotiation power to control the price. The water quality of the mussel farms, such as dissolved oxygen (DO), pH, salinity, electrical conductivity (EC), fecal coliforms bacteria and the total coliforms bacteria met the standard for aquaculture. However, the nutrient, such as ammonium (NH4-N), nitri-nitrogen (NO2-N), nitrate-nitrogen (NO3-N) and soluble reactive phosphorus (PO4-P) were higher than the value of marine aquaculture standard. The results of the contamination of Salmonella spp. bacteria were not found in the mussel’s tissue, however Escherichia coli was found at very low level.

Reduction of diarrhetic shellfish poisoning (DSP) toxins accumulation in cultured mussels by means of rope clustering and hydrodynamic barriers

Accumulation of marine toxins in the organisms is one of the most important problems of the bivalve aquaculture. Mitigation methods are difficult to implement especially in species, as the mussel Mytilus galloprovincialis, which have a relatively low commercial value. For this species, one possible way of decreasing the toxin accumulation is to restrict the availability of toxic cells to the mussels by means of the reduction of the water flow around the perimeter of the culture ropes. We have checked the effectivity to decrease the accumulation of DSP toxins (okadaic acid) in mussels of two ways of obtaining that reduction: surrounding the ropes with a fishing net (1cm mesh); and grouping the ropes (groups of four). During a four week period – with relatively high concentrations of particulate matter – those two ways were tested and shown to effectively reduce both, toxin concentration and toxin burden of cultured mussels exposed to toxic populations of Dinophysis acuminata. The observed reductions were important, 41% and 37% for grouping and surrounding with a net, respectively. Both methods can be used for mussel rafts and long lines and it is very likely they could be also effective with other kinds of toxicity and with other environmental conditions. Statement of relevanceIt would allow a substantial reduction of toxin accumulation.

A model for the growth of mariculture kelp Saccharina japonica in Sanggou Bay, China

The kelp Saccharina japonica is one of the most important mariculture species in China. To predict kelp growth and provide a component for a general multitrophic ecosystem model, a dynamic individual growth model was developed to evaluate environmental effects on kelp growth. This model was calibrated and validated using data from 2 annual mariculture cycles (2008−2009, 2011−2012) from Sanggou Bay, China. Gross growth of S. japonica was described as functions of temperature, light and nutrient contents in plant tissues (internal nutrients), and nitrogen (N) and phosphorus (P) in seawater. Net growth was defined as gross growth minus respiration. The simulation results showed that nutrients were the key limiting factor for growth throughout the kelp growth cycle, whereas both temperature and light only limited kelp growth during simulation days 60−120, i.e. from 1 January to the end of February. Scenario simulations showed that fertilizing with nitrogen could improve kelp growth by as much as 4.4 times. The model also predicted that individual dry weight of S. japonica would increase by 18% when lifting the culture ropes up to the surface. Sensitivity analysis indicates that the empirical coefficient of respiration (r), maximum growth rate (μmax) and minimum internal quota for nitrogen (Nimin) were among the most sensitive parameters. This model shows that the introduction of culture methods such as cage culture, which allows more effective fertilization and depth control, would result in more effective kelp farming.

European aquaculture of sugar kelp (Saccharina latissima) for food industries: iodine content and epiphytic animals as major problems

Abstract There is little use of cultivated kelp including Saccharina latissima (syn. Laminaria saccharina) in the European food industry, in contrast to the extensive use of Pyropia (syn. Porphyra) as Nori, e.g. in sushi restaurants. A major reason for this discrepancy is possibly the extremely high iodine content in laminarian species, i.e. 3–10 g I kg-1 dry weight, in contrast to the situation in Pyropia with its approximately 10 times lower iodine content. Another serious problem for commercial use of S. latissima from rope culture for food is the presence of epiphytic animals on the blades from May onwards as an unwanted food addition. This investigation presents data on iodine content in commercial samples of S. latissima, with indications of lower iodine values from rope cultivation in the Kattegat (Baltic) at reduced salinities, and in general from tank cultivation, possibly mainly due to rapid iodine depletion of seawater in the tanks. Boiling dried blades for several minutes in fresh water resulted in a reduction of the iodine content to approximately one third of the initial value after 2 min. Results from rope cultures in a Norwegian fjord showed the presence of epiphytic animals from early May onwards in the sea, which ruined the food quality of the blades, but the complete absence of such animals throughout the year in parallel tank-grown S. latissima, probably mainly due to mechanical prevention of larval settlement in tank tumble culture.

Seasonal variation in Azumiobodo hoyamushi infection among benthic organisms in the southern coast of Korea.

BackgroundRecent studies have reported that soft tunic syndrome (STS) in the edible ascidian Halocynthia roretzi is caused by the kinetoplastid parasite Azumiobodo hoyamushi. In this study, we attempted to detect and quantify the pathogen in benthic animals.MethodsFour species of ascidians, three species of echinoderms, two species of bivalves, one species each of sponge and algae, as well as seawater, were collected in 2014 and 2015 from an ascidian farm on the southern coast of Korea by SCUBA diving. Samples were collected from ascidian hanging culture ropes or the sea bottom. Inhalent siphons were excised for the analysis of ascidians, and soft body tissues were excised from the other species. Membrane filters were used to filter collected seawater. Tissues and membrane filters were analysed using culture testing, PCR testing, and qPCR diagnoses.ResultsOnly organisms belonging to Ascidiacea are susceptible to A. hoyamushi infection. The infection rate (% infected of the total number collected) and infection intensity (number of cells infected/g tissue wet weight) varied depending on the seasonal variation in seawater temperatures. Most ascidians examined were infected with A. hoyamushi and showed higher infection intensity in cold water seasons (April 2014 and February 2015), followed by a dramatic drop during warm water seasons (August and November, 2014). In addition, infection intensity of A. hoyamushi during the warm water period was higher in ascidians from the sea bottom than those from the hanging culture rope.ConclusionsAmong benthic organisms that inhabit the southern coast of Korea, most ascidians are susceptible to A. hoyamushi infection. Seasonal cycle of infection rates and intensities of the pathogen correspond well with the STS disappearance and onset cycle observed in ascidian farms. The high intensity of A. hoyamushi infection in the ascidians on the sea bottom of ascidian farms during summer suggest further studies on the role of the pathogen in resumption of STS occurrence in late fall or early winter in the southern coast of Korea.

The Effects of Ambient and Aquaculture Structure Hydrodynamics on the Food Supply and Demand of Mussel Rafts

ABSTRACT A field and modeling study of the food supply and demand of mussel (Mytilus edulis) rafts in Maine established the hydrodynamic and particle consumption characteristics of shellfish aquaculture structures. Mussels on rafts filtered about 8 × 106 L/h and consumed about 40 g chlorophyll a (chl a)/h under favorable conditions. Because of the drag of the culture ropes and predator nets, velocity inside the rafts was reduced by 75%–80% in relation to ambient conditions. Chlorophyll consumption by mussels increased with increased food (chl a) concentration and also with increased water velocity inside the rafts. Clearance rates per raft also increased with food concentration. Model results allow for an estimation of water flux and seston depletion within the rafts through the use of point measurements and correction factors. Water velocity measurements taken mid depth in the middle of the rafts underestimated the mean flow through the raft by 10%. Measurements of current velocity and chl a concentratio...

Increasing seaweed crop yields through organic fertilisation at the nursery stage

Extractive seaweed aquaculture is gaining attention in the western Baltic Sea and in particular the co-cultivation with other species for bioremediation or nutrient delivery. However, there are still limitations to viable seaweed production yields in a brackish habitat with a short production period for Saccharina latissima. This investigation presents the specific growth-enhancing effect of Mytilus edulis on the seaweed early nursery stages during the hatchery and during the grow out period at sea in a Baltic fjord. Gametogenesis and juvenile sporophyte development were evaluated with and without blue mussels during 9 weeks of seaweed hatchery. The presence of mussels resulted in a significantly higher abundance of large multicellular sporophytes. After the hatchery period, seedling lines were transferred into the field and installed both in the direct vicinity of and 25 m away from mussel culture ropes. The previously observed supporting effect of mussel co-culture on seaweed development during the hatchery period was still visible after 6 months at sea. Sporophytes were larger, had a higher biomass and had higher carbon content if previously combined with mussels in the hatchery. This investigation suggests that the co-cultivation of seaweed and mussels during seaweed hatchery can increase seaweed crop yields in the following grow out period at sea, with the possibility of being certified organic.

Narrow valve gaping in the invasive mussel Limnoperna securis: implications for competition with the indigenous mussel Mytilus galloprovincialis in NW Spain

The black pygmy mussel Limnoperna securis (Lamarck 1819) is endemic to the brackish waters of New Zealand and Australia, but over the past decade, it has successfully invaded the inner Galician Rias of NW Spain. There is growing concern that L. securis will expand its range to the outer zones of the Rias, where it would pose a threat to the intensive raft culture of the indigenous mussel Mytilus galloprovincialis (Lamarck 1819). In this paper, we compare the valve-opening behaviour of the two mytilids under simulated raft conditions, i.e. full-strength seawater (35 g l−1) and a low current flow regime (2–5 cm s−1). Modes of valve-opening amplitudes that were most frequently observed in both species were in the range of 60–90 %, indicating a tendency towards full valve openness. Both species displayed circadian periodicity (τ = 24 h): maximal gaping was generally observed during periods of darkness and minimum gaping during daylight hours. The only prominent difference in behaviour between the two species was related to the degree of valve opening. The maximum recorded gape angle was 8.2° (SE = 0.9) for L. securis versus 14.8° (SE = 1.4) for M. galloprovincialis. This difference may place L. securis at a competitive disadvantage on substrates, where the two species coexist, such as over rocky shores or potentially mussel culture ropes.

北海道南西日本海沿岸の磯焼け対策としてのコンブのロープ養殖に関する研究

北海道南西日本海沿岸の磯焼け対策としてのコンブのロープ養殖に関する研究

Where to Settle—Settlement Preferences of Mytilus galloprovincialis and Choice of Habitat at a Micro Spatial Scale

The global mussel aquaculture industry uses specialised spat catching and nursery culture ropes made of multi-filament synthetic and natural fibres to optimise settlement and retention of mussels for on-growing. However, the settlement ecology and preferences of mussels are poorly understood and only sparse information exists in a commercial context. This study quantified the settlement preferences of pediveligers and plantigrades of Mytilus galloprovincialis on increasingly complex surfaces and settlement locations at a micro spatial scale on and within ropes under commercial hatchery operating conditions using optical microscopy and X-ray micro-computed tomography (µCT). M. galloprovincialis has clear settlement preferences for more complex materials and high selectivity for settlement sites from the pediveliger through to the plantigrade stage. Pediveligers of M. galloprovincialis initially settle inside specialised culture ropes. Larger pediveligers were located close to the exterior of ropes as they increased in size over time. In contrast, smaller individuals were located deeper inside of the ropes over time. This study demonstrates that X-ray µCT is an excellent non-destructive technique for mapping settlement and attachment sites of individuals as early as one day post settlement, and quantifies the number and location of settled individuals on and within ropes as a tool to understand and optimise settlement in complex multi-dimensional materials and environments.

Cultivation of the two perennial brown algae Ecklonia cava and E. stolonifera for abalone feeds in Korea

Ecklonia cava and Ecklonia stolonifera are perennial brown algae that form sea forests off the coast of Korea. Both species are cultured to supply a summer feed for the abalone industry. Recent expansion of the abalone industry in Korea has been bringing an increase in demand for fresh algal supply. Zoospores of the two algae were seeded in October 2006 on seed frames coiled with 100 m of seed fibers. After 2 months of indoor culture and 2 months of intermediate culture, growth and production of the two algae were compared during their main cultivation period from March 2007 to June 2008, in the culture ground in Wando, Korea (34°26′18.68″ N, 127°05′43.88″ E), in situ. Growth rate of E. cava and E. stolonifera was 1.058 and 3.089 mm day−1, respectively. The mean production of E. stolonifera obtained from the culture ropes was ca. 12 kg wet wt. m−1 of culture rope while production of E. cava was ca. 3 kg wet wt. m−1 of culture rope. The difference in production was attributed from the different growth strategies of the two algae, with only E. stolonifera being able to regenerate blades from the holdfast. The ability to regenerate blades from the holdfast therefore makes E. stolonifera the preferred species for biomass production for abalone feeds. In a 120-day feeding experiment, growth rate, weight gain, and survival rate of abalone showed that E. cava and E. stolonifera feeds could provide an alternative feed to Saccharina japonica during summer months.

Artificial seed production and cultivation of the edible brown alga Sargassum naozhouense Tseng et Lu

Sargassum naozhouense Tseng et Lu is a perennial brown alga found in the coastal area of Leizhou Peninsula, Guangdong, China, and it has considerable commercial potential for further exploitation. To develop a commercial-scale aquaculture of this edible species, the growth, maturation, artificial seeding, and cultivation of this alga and harmful co-existing organisms were investigated from March 2009 to April 2010. In the alga’s natural environment, the receptacles began to form in April and bloomed in May. Artificial cultivation reduced the time required for thalli maturation by at least 1 month. Seedlings were cultured for 1 month in tanks with flowing seawater, until the seedlings had grown to a length of 1.5–2.0 mm. The seedlings were then transferred to a nursery culture ground at sea for an additional 5 months until they reached a mean length of 5 cm. The control of fouling organisms was crucial for establishing a successful seedling culture both indoors and at sea. Afterwards, 45,000 germlings were reared in a grow-out sea area using a full floating raft cultivation system on 2-km-long ropes. The mean yield from this rearing was 1,750 kg wet wt. km−1 culture rope during the farming period of 95 days. Adult S. naozhouense has a greater tolerance to high temperatures than other cultivated Sargassum species and can withstand a temperature as high as 33.7 °C. A preliminary commercial cultivation protocol was also established. The results demonstrate the potential to aquaculture S. naozhouense at relatively high seawater temperatures.

Outplanting time and methodologies related to mariculture of the edible kelp Undaria pinnatifida in the Atlantic coast of Spain

Little is known about offshore cultivation of the edible seaweed Undaria pinnatifida outside Asian waters. However, currently its commercial cultivation is being considered in the North Western Atlantic coast of Spain (Galicia). The effect of outplanting time and methodologies related to the cultivation of U. pinnatifida in this area was studied. Biomass yield, morphological features, and growth rate were examined on sporophytes outplanted from October to December at the same site in a coastal bay. Experiments were conducted over two years, applying different harvesting and cultivation methods. Results indicate that the most suitable months for outplanting were October and November, with larger biomass production as well as improved sporophyte quality (i.e., morphology). Cultivations from October to December ended when most of the sporophytes had developed sporophylls (reproductive structures) and this occurred between early and late April in all the outplanting trials. The similar harvest time for all plants suggests that harvesting time is not related to outplanting period but should be mainly influenced by the photoperiod. These results suggest a single harvest as the most appropriate method. Moreover, results also showed that cultivation was successful using the two tested methods: seedling string all along the culture rope and seedling strings inserted at regular intervals into the rope. Finally, this paper also discusses the suitability of two different systems of offshore farming: in long-line and in vertical rope.