Growth and condition index of mussel Mytilus galloprovincialis in experimental integrated aquaculture

Integrating mussel and finfish aquaculture has been recognized as a way to increase profits and decrease environmental impacts of finfish aquaculture, but not enough is known about the effects of finfish aquaculture on mussel growth. Here we present a pilot study aimed at determining how distance from finfish aquaculture affects mussel growth. To this end, we measured growth and condition index of mussel (Mytilus galloprovincialis) at three different distances (0, 60 and 700 m) from finfish aquaculture in the eastern Adriatic Sea. There was a statistically significant difference in growth of tagged mussels with respect to site. Average measured lengths of mussels at sites 1, 2 and 3 after the 10 months of the experiment were 57.60, 62.73 and 58.66 mm. Mussels grew fastest from March to May, and slowest from July to September, regardless of their position. Condition index showed spatial and temporal variations with higher values during fall and winter (∼23), and lower values during spring and summer (∼20). Our results show that production cycle in areas traditionally considered suboptimal for aquaculture can be equivalent to the cycle in areas traditionally considered optimal for mussel aquaculture if mussel aquaculture is integrated with finfish aquaculture.     

Betanodavirus ability to infect juvenile European sea bass,Dicentrarchus labrax,at different water salinity

Viral encephalopathy and retinopathy (VER) is one of the most devastating and economically relevant diseases for marine aquaculture. The presence of betanodavirus in freshwater fish is recorded, but very little is known about VER outbreaks in marine species reared in freshwater. Our study investigated the ability of betanodavirus to cause disease in European sea bass, Dicentrarchus labrax, reared at different salinity levels. Fish were challenged with RGNNV or mock infected by bath at different salinity levels (freshwater, 25‰ and 33‰). Fish were checked twice a day and the dead ones were examined by standard virological techniques, by rRT‐PCR and by histochemical and immunohistochemical analyses. All the infected groups showed a significant higher mortality rate than the one of the mock‐infected group. VERv presence was confirmed by rRT‐PCR. Histochemical and immunohistochemical analyses highlighted the typical lesions associated with VER. Our results highlight that salinity does not affect the ability of betanodavirus to induce clinical signs and mortality in European sea bass infected under experimental conditions. These results underline the great adaptation potential of VERv, which in combination with its already known high environmental resistance and broad host range, may explain the diffusion of this disease and the threat posed to aquaculture worldwide.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds I: Clearance Rate of Chlorophyll-α

The production and livelihood of aquaculture facilities depend on increased growth of species being harvested. Only 15%-25% of nitrogen and phosphorus are retained in farmed fish even when all feed is consumed. In both marine and freshwater aquaculture systems, bivalves have proven to be an inexpensive method for controlling algal growth through suspension feeding. With 25% of the native U.S. freshwater mussel species under federal protection, their use in aquaculture ponds could lead to further propagation and restoration of natural populations. Elliptio complanata is an important species in Delaware rivers and connected estuaries; a recent two-year study by the United States Geological Survey found that 98% of mussels found in the Delaware River were Elliptio complanata. The objective of this study was to calculate the clearance rate of E. complanata in a laboratory study. This would help us determine if mussels can serve as an addition to chemical and mechanical filtration regiments and thrive in an aquaculture setting. Using feeding chambers we investigated the effect of E. complanata on algae grown from an aquaculture pond and on a cultured alga over a four-hour period. Temperature, dissolved oxygen, and pH were monitored, and samples were than analyzed for total chlorophyll-α. The average of both the single cell using Chlorella vulgaris and mixed assemblage treatments chlorophyll-α clearance rate was 0.187 liters per hour per mussel. Prior to this experiment, these mussels were held for a period for two months in the holding system in the laboratory. The resulting low clearance rate as compared to the previous studies in the field is possibly due to the stress from holding these mussels. However, our study demonstrated that mussels have the potential to be used in an aquaculture setting and/or recreational ponds to help reduce algae populations that can occur as a result of eutrophication.     

Physiological Indices of Maricultured Mussel Mytilus galloprovincialis Lamarck, 1819 in Istria,Croatia: Seasonal and Transplantation Effect

Transplantation of mussels to new aquaculture sites is currently being undertaken in Istria (Croatia) to increase production, minimize potential seasonal urban contamination, and secure safer seafood products. The purpose of this study was to determine the effects of season and transplantation on physiological indices (condition index and meat yield) of mussels, Mytilus galloprovincialis. Mussels were obtained from five aquaculture areas in Istria (central Lim Bay, Ra?a, Budava, Vabriga, and Pomer) and moved to a reference site in inner Lim Bay from April to July. Results showed that both season and transplantation affected physiological indices of mussels. Higher physiological indices were found in cultivated mussels from all areas in summer compared to spring, except in mussels from Vabriga and Pomer. In addition, higher physiological indices were found in mussels transplanted from central Lim Bay to the reference site in inner Lim Bay. Transplantation negatively affected physiological indices of mussels from Vabriga and Pomer, with no change in mussels from Ra?a and Budava. In conclusion, mussels from all areas exhibit satisfactory commercial results (≥15%) during the peak summer harvesting season. For most transplanted mussels, transplantation itself represents additional stress, bringing into focus adaptation processes, stock genetics, and favorable ecological conditions.     

Growth and mortality of Mediterranean mussel Mytilus galloprovincialis Lam., 1819, in relation to size on longline in Mersin Bay, Izmir (Turkey – Aegean Sea)

The growth and mortality rate of different size of mussels, Mytilus galloprovincialis, were compared in Mersin bay, Izmir. Mussel sampling was performed on a monthly basis over 1 year, together with hyrobiological parameters. Water temperature, salinity, chlorophyll a, total particulate matter (TPM) and particulate organic carbon (POC) were determined. Average chlorophyll a, TPM and POC values were 3.88±1.62 μg L⁻¹, 13.12±3.68 mg L⁻¹ and 252±121.89 μg L⁻¹ respectively. Initial mean lengths of mussels for each size group were 10 mm (9.91±0.25 mm), 20 mm (20.14±0.29 mm), 30 mm (30.66±0.21 mm), 40 mm (40.14±0.21 mm), 50 mm (50.62±0.21 mm), 60 mm (59.77±0.21 mm) and 70 mm (69.47±0.62 mm). Maximum growth in length occurred during the spring–summer months. The annual length increments of mussel size groups were 46.22, 41.42, 30.3, 28.03, 20.63, 16.34 and 12.03 mm from small to large size groups respectively. Small mussels grew faster than large mussels and reached commercial size at the same time. Mortality was <5% for all groups at the end of the experiment.     

Protective socking material for cultivated mussels: a potential non-disruptive deterrent to reduce losses to diving ducks

Predation of cultivated mussels by diving ducks can threaten the viability of mussel farms. Conventional scaring tactics have had limited success at deterring ducks from feeding on cultivated mussels, because of rapid habituation and 24-h feeding cycles of some waterfowl species. We tested a socking material containing a biodegradable protective layer against predation by diving ducks on experimental blue mussel (Mytilus edulis) aquaculture sites in Prince Edward Island, Canada. We also assessed the effect of this new socking material on mussel growth and survival. Results showed that the protective socking has the potential to reduce losses to ducks, but did not perform well for all mussel seed sizes used by the industry. The protective layer also did not biodegrade fast enough, trapping a portion of mussels inside the sock, affecting growth and survival of these mussels. Improvements are needed to make this solution effective for all mussel sizes used by the industry and to make its production more cost effective.     

Polyculture of sea scallops (Placopecten magellanicus) suspended from salmon cages

Commercial and developmental operations for the culture of the seascallop, Placopecten magellanicus, are present in AtlanticCanada and New England. In an experiment designed to examine the commercialfeasibility of polyculture of scallops with Atlantic salmon(Salmo salar), we measured growth andsurvival of sea scallops grown in suspension at two salmon aquaculture sites innortheastern Maine (Johnson Cove (JC) and Treats Island (TI)). Sea scallop spatwere grown in pearl nets and deployed on drop lines containing ten nets inAugust 1994. One drop line of ten nets was sampled about every four months andscallops were counted, measured and weighed. Scallop tissues were also analysedfor paralytic shellfish toxins (PSP). The maximum level of PSP recorded duringthe study was 1174 g STX equiv.·100 gtissue^–1 (excluding adductor muscle weight). After one year,shell heights were 53.6 and 56.4 mm, growth rates were 0.11 and0.12 mm per day and wet adductor muscle weights were 3.3 and 4.1g (TI and JC, respectively). These growth rates were comparable tosea scallops grown in suspension culture to a nearby scallop aquaculture siteand other areas in Atlantic Canada. Reduced rates of survival were found duringthe latter part of the experiment and were attributable, in part, to heavyfouling, predators and high stocking density. The potential for supplementalincome, diversification of the salmon aquaculture industry, and feasibility ofculturing scallops at adjacent sites to salmon operations does exist.     

The effects of holding space on juvenile red king crab,Paralithodes camtschaticus (Tilesius, 1815), growth and survival

Rearing crustaceans communally for aquaculture, stock enhancement or research often results in high rates of cannibalism and low yields. One potential strategy to reduce loss from cannibalism is to rear crustaceans in individual cells. As small holding cell size can result in decreased growth or increased mortality, it is essential to identify the optimal holding cell size, both for mass culturing efforts and for experimental design purposes. In this study, we reared juvenile red king crab, Paralithodes camtschaticus (3.67–8.30 mm carapace length) in 20, 40 and 77 mm diameter holding cells, and monitored growth and survival over a 274‐day experiment. A trend of lower growth per molt in the smallest holding cells resulted in crab 17% smaller than those in the large holding cells at the end of the experiment. In addition, mortality rates were an order of magnitude higher in the small holding cells compared with the large or medium cells. For individual rearing of this size of juvenile red king crab, the medium‐sized cells (40 mm diameter) are the optimal size as there was no increase in mortality and only marginally lower growth rates compared to the large‐sized cells.     

Growth,Mortality, and Biochemical Composition in Octopus vulgaris Reared Under Different Conditions of Sex Ratio

Octopus vulgaris is a potential candidate to diversify marine aquaculture. Even though mortality under rearing conditions has been related to reproductive processes, the benefit of sex segregation remains unclear. In order to clarify this, wild octopuses (862 ± 101 g) were reared in floating cages under three proportions of male : female sex ratio: 1:1, 1:0, and 4:1 (n = 30 per treatment). The experimental period lasted 2 mo and octopuses were fed on bogue, Boops boops (aquaculture by‐product). Higher growth rates were observed in octopuses reared under 1:1 and 1:0 (1.8%/d) in comparison with those reared under 4:1 conditions (1.6%/d). Regarding sexes, a lower growth was detected in females reared under 4:1 (1.1%/d) in comparison with females (1.8%/d) and males (1.7–1.9%/d) reared under 1:1 conditions. Survival was 97, 97, and 90% in sex ratio 1:1, 1:0, and 4:1, respectively. Sexual maturity data showed that males were all mature, while most females were still maturing (60–84%) at the end of the rearing period. High lipid content in bogue (44% dw) did not reflect on octopus muscle. This tissue showed a similar biochemical composition irrespective of the sex ratio condition, with a high protein (87% dw), a low lipid (5% dw), and a high n‐3 HUFA content (42%).     

Completion of the Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel) life cycle

Tuna aquaculture is currently dependent on the wild capture of juveniles for production. The development of hatchery technology for bluefin and other tunas would be a major step forward in improving sustainability of their aquaculture. The present study overviews the technology in the life cycle completion of the Pacific bluefin tuna (PBT) Thunnus orientalis (Temminck et Schlegel) under aquaculture conditions in Kinki University, and the problems to be solved for the establishment of tuna hatchery technology. On 23 June 2002, broodstock of PBT that were artificially hatched and reared spontaneously spawned in captivity. The resulting eggs hatched and were subsequently reared to the juvenile stage. The spawning fish were the result of a research project started in 1987 to rear wild‐caught juvenile PBT that were several months old. Fertilized eggs were obtained from these fish in 1995 and 1996. Resulting juveniles (the artificially hatched first generation) were reared to maturity and spawned in 2002. Over the summer of 2002, 1.63 million eggs from these fish were used for a mass rearing experiment, and 17 307 juveniles were produced and transferred to an open sea net cage. Of these artificially hatched second‐generation PBT, 1100 grew to approximately 95 cm total length and 14 kg body weight in 22 months. This procedure means the completion of PBT life cycle under aquaculture conditions, which was first attained among large tuna species. The problems awaiting solution in PBT hatchery production are their unpredictable spawning in captivity, to improve survival during the first 10 days post hatch, to reduce cannibalism in larval and juvenile stages, and to solve collision problem causing high mortality during the juvenile stage.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds II: Effects on Aquaculture Pond Water Quality

Bivalves have been proven to be an inexpensive method for removing suspended solids, dissolved nutrients, and controlling algal growth through suspension feeding. The freshwater mussel, Elliptio complanata, is one of the most abundant species in Delaware, and it is additionally favorable for this experiment because of its hardiness against environmental stress and its filtration efficiency. This study examines the possibility that biomechanical filters such as E. complanata can supplement existing chemical and mechanical filtration regiments in aquaculture pond management. Twelve earthen aquaculture ponds located at the Delaware State University were stocked at a density of 4,000 catfish (Ictalurus punctatus) per hectare. Four different concentrations (0, 75, 150, and 300) of E. complanata were placed in trays within the ponds with three replicates of each concentration. The trays were suspended 15 cm below the surface of the water for a period of five months. Fish were fed a 32% protein diet twice daily at a rate of 1% of their body weight. Water quality was analyzed weekly while fish and mussel growths were measured biweekly. Results from water quality parameters varied significantly and were not conclusive based on the data obtained in this study. Water quality did not improve within the mussel treatment ponds during the course of this study and was found to be significantly below that of control ponds for all of the water chemistry parameters measured, with the exception of ammonia. Catfish in the 150 mussel treatment ponds grew the fastest; the 75 mussel treatment provided the most growth in mussels; and the 300 mussel group maintained the highest mussel survivorship. Although there were differences between ponds, fish growth and survivorship were not significantly different between treatments. While our mussel densities may have not been sufficient, their placement within the water column may have added additional stress. Being removed from the sediment can result in a decreased clearance rate in a benthic species such as E. complanata. This study may not have been conclusive in proving that mussels can be used to maintain water quality in aquaculture ponds, but we did see positive growth and survivorship of mussels and fish that indicated that the mussels were thriving in the aquaculture pond setting. This study may show that aquaculture ponds provide a suitable habitat in which propagated mussels may be held until their release into native areas.     

Growth, mortality and moulting rate of noble crayfish, Astacus astacus L., juveniles in aquaculture experiments

Growth, mortality, moulting rate and cheliped loss were examined in aquaculture experiments with noble crayfish, Astacus astacus L., juveniles from four different Norwegian populations in the period September 1987-June 1988. The juveniles were hatched indoors in May 1987 from parents wild-caught in 1986. The experiments were performed at 18-19°C in communal rearing units. Mean total length at experiment start was about 20mm in all groups. There were no significant differences in mean size (final mean total length: 32-2-34-8mm). mortality (83a-900%) or cheliped loss (429-700%) among juveniles from the different populations when exposed to similar conditions (food: dry pellets; photoperiod: L:D = 8:16). Among crayfish fed fish and potatoes in addition to dry pellets, and with continuous light conditions, mortality was reduced significantly to about 70%. Continuous light conditions significantly increased mean size (final mean length: 36-1-389mm). Moulting occurred from November throughout the experiment period. Moulting rate was positively correlated to mortality and growth rate (i.e. mean length increase). A positive correlation between mortality and cheliped loss, along with direct observations of cannibalism, indicated that agonistic behaviour and cannibalism were the dominating mortality factors. It is suggested that continuous light conditions reduce agonistic behaviour and thereby decrease mortality.     

Experiences of integrated mariculture in a southern Tyrrhenian area (Mediterranean Sea)

To ascertain the potential for exploiting marine areas for mariculture, data on the cultivation of molluscs and fish in the open sea of the southern Tyrrhenian were collected from May 1994 to June 1995. The aims of this integrated study were to test simple breeding methods for molluscs and fish, to apply these to the practices employed by local fishermen and to experiment with the use of a cage system requiring a low level of investment. Crassostrea gigas (Thunberg) and Mytilus galloprovincialis (Lamarck) were cultivated on submerged long lines around cages used for cultivating Seriola dumerili (Risso) and Diplodus puntazzo (Cetti). S. dumerili specimens were placed in two cages and fed with either fish scraps or pellets, while in a third cage, D. puntazzo were fed with pellets only. After a period of 12 months, the following results were obtained: the oysters measured 47.50 ± 12.30 mm and weighed 0.13 ± 0.09 g; the mussels placed in culture as juveniles reached a length of ≈ 40 mm, while the mussels placed in culture as subadults reached the commercial size of about 60 mm. The mean length and weight measurements of the two fish species were as follows: Diplodus 228 ± 14.4 mm and 228 ± 40.48 g; Seriola (lot A) 438.1 ± 25.28 mm and 1149 ± 172.2 g; Seriola (lot B) 347 ± 25.6 mm and 576 ± 139 g.     

Effect of temperature on somatic growth and survivorship of early post-settled green sea urchins, Strongylocentrotus droebachiensis (Müller)

A laboratory experiment was run for 171 days to assess growth and survivorship of recently settled juveniles of the green sea urchin, Strongylocentrotus droebachiensis (Müller), reared at five temperatures: 4.7±0.8, 9.0±1.1, 12.9±1.1, 16.0±1.5 and 19.7±1.3°C (mean±SD, n=7942). Individual sea urchins were housed separately in PVC pots with Nitex mesh bottoms (10 per tank and five replicate tanks per temperature treatment) and fed a combination of benthic diatoms and macroalgae (Porphyra sp.). The test diameter of each urchin was measured and survivorship recorded on a monthly basis. Mean (±SE) test diameter of all individuals at the beginning of the experiment was 2.41±0.03 mm (n=250). At the end of the experiment, mean test diameter (±SE) was significantly larger at 9.0°C (8.46±0.06 mm) and 12.9°C (8.20±0.25 mm) than at 4.7°C (7.27±0.05 mm), 16.0°C (6.72±0.17 mm) and 19.7°C (2.65±0.24 mm) and significantly larger at 4.7 and 16.0°C than at 19.7°C. When growth was expressed as a per cent increase in test diameter from the start of the experiment, however, there were no significant pair‐wise differences among 4.7, 9.0, 12.9 and 16.0°C treatments at the end of the experiment, but all these treatments were significantly greater than at 19.7°C. Mean per cent survivorship (±SE) at the end of the experiment for the various temperature treatments was 76.0±6.0%, 90.0±5.5%, 100.0±0.0%, 98.0±2.0% and 26.0±11.2% at 4.7, 9.0, 12.9, 16.0 and 19.7°C respectively. Per cent survivorship was significantly greater at 4.7, 9.0, 12.9 and 16.0°C than at 19.7°C and significantly greater at 12.9 and 16.0°C than at 4.7°C. Mean area increase of urchins per replicate tank at the end of the experiment – taking into account both test diameter growth and survivorship – was significantly larger at 9.0 and 12.9°C than at 4.7, 16.0 and 19.7°C, and significantly larger at 4.7 and 16.0°C than at 19.7°C. The results of this study suggest that young juveniles of S. droebachiensis should be reared at 9–13°C in order to optimize production for aquaculture.     

Differential growth of the brown mussel,Perna perna (Linnaeus, 1758), in longline and pole cultures in Dakhla Bay (SW Morocco,Atlantic Ocean)

There is a great interest in establishing mussel farming in Dakhla bay. Selection of suitable sites is more meaningful only if a reliable culture method at proposed site is included. We compared two different culture methods, longline and pole, over 1 year (June 2016 to June 2017). Growth indicators for Perna perna (size and weight growth rates, frequency distributions and estimating growth curves) were analysed from seeding to harvest. The results highlighted the influence of culture method on growth rates of mussels (p < 0.05). At harvest, individuals reared on longline presented higher growth rates and consequently reached greater weight and length values than those reared on pole. Mussels reared at the longline grew 73.2 mm and gained 53.5 g W_L (live weight) and 3.3 g W_t (tissue dry weight) after 12 months of cultivation. However, mussels cultured at the pole gained only 52.3 mm, 26.7 g W_L and 1.6 g W_t. Aerial exposure of mussels at low tides could explain this reduced performance on pole compared with longline. Size frequency distributions at harvest fitted bimodal distribution in both cultures due to an asymmetric competition among individuals. Effect of density started in both treatments after 7 months of culture when mussels reached 60–70 mm, implying an increment of their food and space requirements. To prevent overcrowding, the initial density should have been reduced through “thinning‐out.” The longline method exhibited high‐performance growth and hence is highly recommended for cultivation of P. perna in Dakhla bay.     

Role des individus conditionnes dans l'initiation a l'auto-nourrissage et dans l'adaptation a la captivite du loup,Dicentrarchus labrax, 0+ sauvage,en periode hivernale

It is shown that the presence of pre-conditioned fish in a wild naive group reared under limiting ecological conditions (winter) facilitates the adaptation of the group to captivity by accelerating the learning of self-feeding and minimizing rearing stress and mortality. The reasons for this phenomenon, which has implications for aquaculture and fishing, are discussed and related to the learning capacity of this species when imitating pre-conditioned fish.     

Influence of temperature on growth and survival of juvenile winter flounder,Pseudopleuronectes americanus (Walbaum) reared under continuous light

Winter flounder, Pseudopleuronectes americanus, has emerged as a promising candidate flatfish for cold‐water aquaculture and restocking. Here, juveniles were reared for 8 weeks at three temperatures: 10, 15, and 20°C under 24‐hr light. All fish were imaged at stocking and at 2‐week intervals, where growth was measured as changes in standard length (S_L) and body area (B_A). By week 2, fish reared at 15 and 20°C were larger than those grown at 10°C. At weeks 4 to 6, fish at 15°C were larger than fish at 20°C. Linear regressions were used to model growth dynamics over time at each temperature. Highly significant linear growth trajectories were detected over time for S_L and B_A. S_L and B_A regressions also showed a significant difference among the slopes across temperatures, where comparing slopes showed the best temperature to rear the flounder was 15°C. Weights of fish held at 15°C and 20°C were greater than at 10°C at the termination of the experiment. Within each temperature, the growth rate of malpigmented fish was not different from that of the normally pigmented fish. Overall, growth of winter flounder was comparable to that of other commercially produced flatfish species, providing strong evidence for this flatfish species as a potential species for aquaculture.     

Novel effects of salinity and water reuse on growth of juvenile New Zealand turbot, Colistium nudipinnis (Waite 1910), a potential aquaculture species

Juvenile New Zealand turbot, Colistium nudipinnis (Waite 1910), produced during the first aquaculture development project for this endemic flatfish, were reared at ambient and reduced salinities to determine the effect of salinity on growth and survival and the possible implications for aquaculture. Juveniles aged from 176 days to 17 months showed a high level of salinity tolerance, with minimal mortality attributable to salinity reduction over the range 33–18 g L^?1. Growth rate was slightly increased at the slightly reduced salinity of 28 g L^?1 (5 g L^?1 below ambient) but was significantly decreased at the markedly reduced salinity of 18 g L^?1. The growth response at 23 g L^?1 was markedly different between ‘new’ water and water that was recycled from a previous set of rearing tanks, with juveniles reared in 23 g L^?1‘new’ having a mean growth rate that was 29% lower than that of the control juveniles (in 33 g L^?1‘new’ water), whereas juveniles in 23 g L^?1‘reused’ water grew 45% faster than the controls. The implications of this novel effect are discussed in relation to the aquaculture potential of the New Zealand turbot.     

Effects of Hyperoxic Conditions on Growth Performance in Juvenile and Adult Green Sea Urchin,Strongylocentrotus droebachiensis

The effects of hyperoxic conditions on survival, gonad growth, feed intake, and food conversion of adult and somatic growth and survival of juvenile green sea urchin, Strongylocentrotus droebachiensis, were examined. Juvenile and adult sea urchins with initial diameters of 11.5 and 75 mm, respectively, were reared in water with constant oxygen saturations of 100 (control), 115 and 130% for 42 d (juvenile) and 51 d (adult sea urchin) at 8 C and 33‰ salinity. During the experiment the gonad indices of the adults tripled from 7.3% (±1.5) to 21.4% (±4.3), 19.4% (±4.7), and 22.0% (±4.4) for the groups kept at 100, 115, and 130% oxygen saturation, respectively. At the end of the experiment, the differences in gonadal size among the groups were not significant. Neither were there any significant differences in food intake or food conversion ratio among the groups. Only one animal died during the experiment. The juvenile sea urchin kept at 100, 115, and 130% oxygen saturation doubled their test diameter from initially 11.5 mm (±1.5) to 19.9 mm (±1.4), 21.4 mm (±2.1) and 20.6 mm (1.0), respectively, but there were no significant differences in growth among these groups. There was no mortality during the experiments in these groups. Overall, the findings suggest that juvenile and adult S. droebachiensis are unable to utilize hypersaturation of oxygen to increase somatic or gonad growth, but can be reared at hyperoxygenated water for prolonged periods of time without harmful effects.     

Growth and Survival of Juvenile Freshwater Mussel,Chamberlainia hainesiana (Lea, 1856), at Three Densities in the Natural Reservoir and River Environments,Thailand

The effects of location and density on the growth and survival of juvenile freshwater pearl mussel, Chamberlainia hainesiana, 150–360 d after metamorphosis were investigated to determine the optimal ranges for commercial farming in Thailand. Juveniles were reared outdoors in two locations (the Mae Klong Reservoir and the Khwae Yai River, Kanchanaburi Province). Three density levels (25, 50, and 100 mussels/basket) were established at each location, with three replicates per density level. Phytoplankton from the water column in the natural habitats served as feed; no supplemental feed was provided. The mussels cultured in the reservoir had significantly higher growth rates than those cultured in the river (P < 0.01). The density level of 25 mussels/basket exhibited the highest average growth rates (in weight, length, height, and width per day). The density levels of 25 and 50 mussels/basket did not show significant differences in growth from each other (P > 0.05), but both showed significant differences in growth from the density level of 100 mussels/basket (P < 0.01).