Nursery Culture Research Articles

Assessing new microalgae species as potential feed for bivalve spat in nursery culture

ABSTRACT Microalgae remains a primary food source for hatchery and nursery culture of juvenile bivalves. However, there is a mismatch between the characteristics of the microalgae currently used in nursery culture and the feeding abilities and nutritional requirements of juveniles of some bivalve species, such as the green-lipped mussel, Perna canaliculus. Therefore, there is a need to identify new species of microalgae for this purpose that have favourable cell size, good growth performance under culture conditions and appropriate nutritional content for juvenile bivalves by using these characteristics as primary selection criteria. In this study, the growth performance under standard culture conditions of four microalgae species (Chrysochromulina camella, Gymnodinium simplex, Pyramimonas parkeae and Stephanodiscus niagarae) which are of a sufficiently large cell size to meet the needs of juvenile mussels (i.e. 10–20 µm size range) were tested in comparison to three commonly cultured commercial species (Chaetoceros muelleri, Diacronema lutheri and Tisochrysis lutea). Results show that G. simplex, S. niagarae and the two strains of P. parkeae (P. parkeae (C) and P. parkeae (I)) can achieve similar biomass as the reference species in the intermediate (1 L) culture stages despite the large difference in cell densities. The poor growth of C. camella in F/2 media indicates a necessity of determining its appropriate culture conditions before further assessing its suitability as a nursery feed for juvenile bivalves. The proximate analysis of S. niagarae, G. simplex and P. parkeae (I) reveals nutritional profiles conducive to spat development. However, the P. parkeae (C) strain contained low carbohydrate content, suggesting inferior nutritional value compared to the P. parkeae (I) strain, showing that variants of the same species can have different biochemical composition and suggesting the former might have limited suitability for feeding in nursery culture. The findings indicate that G. simplex, S. niagarae and P. parkeae (C) hold sufficient promise as spat feed in nursery culture to warrant further testing to confirm their efficacy as live microalgal feed for bivalve spat.

Effectiveness of the garlic (Allium sativum) juice on removing the Pacific abalone postlarvae (Haliotis discus hannai) and subsequent growth evaluation

The Pacific abalone (Haliotis discus hannai) is widely cultivated in East Asian countries. Aquaculture of this species has become a thriving industry in China, with adequate seed production being a key contributing factor. However, maintaining sufficient diatom abundance during the nursery phase remains challenging. In this study, we assessed a transfer nursery culture method that involves prolonged cultivation with a sufficient diatom supply. This method involved treating postlarvae on diatom-depleted plates with a garlic juice (GJ) solution to facilitate detachment, followed by transfer to newly diatom-precoated plates for further growth in the nursery. We investigated the effects of garlic juice concentration (GJC) and animal size on detachment and mortality rates using a two-factor design. Our negative binomial regression analysis uncovered significant impacts of both factors and their interactions on the target traits. We noticed that the optimal GJC for smaller groups of abalone postlarvae (2.2 ± 1.0 mm) was 0.7 %, while for larger groups (3.8 ± 2.2 mm), it increased to 1.0 %. Notably, suitable GJC concentrations during post-treatment recovery resulted in no apparent mortality in Pacific abalone postlarvae. Our study demonstrated the effectiveness of the transfer nursery method, showing an improvement of over ∼1.1 mm in shell length and a 43.1 % increase in survival during a 30-day experiment. Our study presents a significant advancement, as it likely introduces the first reported method of large-scale postlarval removal of H. discus hannai for prolonged nursery periods with sufficient diatom provision. The integration of GJ treatment and the transfer nursery method exhibited promising results, highlighting the benefits of its application for enhancing husbandry procedures, nursery management, and the overall industrial productivity of Pacific abalone.

Different protein levels in a super-intensive culture of juvenile Pacific white shrimp (Litopenaeus vannamei) in biofloc systems during the early rearing phase

The determination of crude protein level in diets of aquatic organisms allows maximizing growth, decreasing feed costs and improving water quality. A nursery culture of Litopenaeus vannamei was carried out in superintensive biofloc systems using five diets with different protein levels (320 g kg-1 CP, 360 g kg-1 CP, 400 g kg-1 CP, 440 g kg-1 CP and 480 g kg-1 CP); each diet was used in quadruplicates. The experimental period lasted 35 days, and the shrimps (0.59± 0.001 g) were stocked at a density of 600 PL m-³, using 20 experimental units (50 L of useful volume). There were no significant differences in animal survival between treatments (p>0.05). The animals fed with 480 g kg-1 presented higher final weight, SGR when compared to the treatments fed with 320 g kg-1 (p<0.05). Furthermore, feeding shrimp with 32% CP diets results in a reduction in feed utilization and nutrient retention, thus increasing feed costs. Overall, the results show that it is possible to reduce the protein content of L. vannamei diets to up to 360 without affecting the zootechnical performance, survival and antioxidant capacity of the animals.

Nutritional condition of wild and hatchery‐reared, green‐lipped mussel (Perna canaliculus) spat used for aquaculture

AbstractThe nutritional condition of seed mussels (spat) at the time of seeding is thought to play a major role in influencing spat losses on mussel farms, with nutritionally compromised spat thought to be more likely to be lost from aquaculture substrata than those in good condition. New Zealand's Greenshell™ mussel (Perna canaliculus) aquaculture industry relies almost exclusively (∼85%) on wild caught spat, with the vast majority, typically > 90%, lost shortly after being seeded onto coastal mussel farms. This study sought to quantify the extent of the variability in the nutritional condition (i.e., calorific, protein, lipid and carbohydrate content) of samples of spat used by the Greenshell™ industry between 2014 and 2021 (i.e., wild caught and hatchery produced) as a first step towards determining whether variability in nutritional condition may be a significant contributor to the marked variation observed in spat performance after it is seeded onto coastal farms. All parameters measured were highly variable among wild spat samples, with all but lipid content varying, including for samples of wild spat harvested at different times within the same month. Furthermore, there were no clear patterns in the nutritional condition of spat across months or years, suggesting environmental factors that limit feeding during the harvest and transport of spat may be contributing to marked differences in the quality of spat being used by the industry to seed farms. These results provide a baseline for assessing the nutritional condition of Greenshell™ spat and point towards a need to develop interventions to improve the quality of wild spat supply for this industry to help and prevent the ongoing massive losses of spat from farms. These measures could include, testing nutritional condition of spat at harvest or prior to seeding, development of nursery culture methods and development of artificial spat feeds that have the potential to replace live phytoplankton during nursery culture.

Evaluation of separation of seed mussels from macroalgae using chlorination

AbstractGrowing seed mussels (spat) to larger sizes in single‐seed nursery culture systems prior to seeding onto coastal mussel farms is an effective approach for greatly reducing costly spat losses during this stage of mussel aquaculture. However, the production of single‐seed mussel spat in nursery culture systems relies on first separating spat from the settlement substrata to which they are attached, whether spat are settled in a hatchery or gathered from the wild. This study sought to determine whether chlorination could be an effective approach for separating wild Greenshell mussel (Perna canaliculus) spat from beachcast macroalgal material (Kaitaia spat material) harvested from a beach in northern New Zealand. The results demonstrate that chlorination (i.e. in solutions of up to 0.625% sodium hypochlorite) is a highly effective approach for separating spat, resulting in the detachment of up to 94.6% in one treatment without increasing mortality relative to controls. The effectiveness of chlorination was modulated by spat density, with increasing spat densities, lowering rates of detachment. While chlorination is effective at separating small spat (i.e. successfully separating 72.4% of spat <750 μm in shell length) overall spat densities, further investigation is required to determine how to effectively separate larger spat (i.e. with chlorination only successfully separating 21.5% of spat >750 μm). The high survival (relative to the control treatments) also suggests that chlorine concentrations and exposure durations could be increased from those used in this study. These results demonstrate that chlorination can be used to separate spat from substrate prior to their transfer to nursery systems for ongrowing, paving the way for such approaches for reducing spat losses to be integrated into the aquaculture production cycle.

Plankton community in Penaeus vannamei nurseries with synbiotic system under different frequencies of adjustment on Ca:Mg:K ratio in low salinity water

The aim of this study was to evaluate plankton communities in Penaeus vannamei nurseries under different frequencies of adjustment on Ca:Mg:K ratio in low salinity water and with synbiotic system. A nursery culture was carried out for 40 days, using 2000 shrimp m⁻³. Following treatments were established: 1IA (Ca:Mg:K ratio adjustment to 1:3:1 on day 1); 2IA (Ca:Mg:K ratio adjustment to 1:3:1 on day 1 and day 20); 3IA (Ca:Mg:K ratio adjustment to 1:3:1 on day 1, day 10, and day 20); SW (seawater - salinity of 31 g L−1); and SWD (seawater diluted to a salinity of 2.3 g L−1). Rice bran processed by probiotic microorganisms was used as an organic carbon source. Treatments did not have a significant effect on phytoplankton and zooplankton composition. However, plankton composition was significantly different over the experimental course. A reduced abundance of Cyanophyta was observed compared to traditional aquaculture systems. This can be explained by the probiotic bacteria addition to the system, along with fertilization, which may have limited the growth of this harmful algae. Throughout the experiment, zooplankton community had a dominance by protozoan microorganisms, such as amoebae and ciliates. The presence of copepods and rotifers was also observed throughout the experimental course. This proves that the use of the synbiotic system provides conditions for the microbial loop development, mimicking a natural environment. Different adjustment frequencies in the water Ca:Mg:K ratio do not significantly change plankton composition in P. vannamei intensive nurseries using low salinity water and synbiotic system. Temporal variation in plankton composition probably occurred due to fertilization of the system with an organic carbon source. The use of the synbiotic system proved to be efficient in microbial loop development, providing the growth of a high load of microorganisms that can influence water quality and shrimp growth in low salinity water.

Census of potential predators and competitors of sandfish, Holothuria scabra, juveniles during floating hapa ocean nursery culture

AbstractPredation and competition are among the most important factors affecting sandfish, Holothuria scabra, growth and survival in ocean‐based production systems. In this study, the potential predators and competitors of sandfish juveniles reared at two sites in the Philippines using the floating hapa ocean nursery system were assessed. A total of 26 species of potential predators and competitors from 16 different families of fishes, molluscs and crustaceans were recorded. These taxa were dominated by the opisthobranch Stylocheilus striatus at Bolinao (north–west Luzon) and the isopod Cymodoce sp. at Maliwaliw (eastern Visayas). Highest number of potential predators and competitors that recruited and/or migrated to the inside of floating hapa nets was recorded on day 23 at Bolinao and day 30 at Maliwaliw, then decreased over the 69‐day duration of the study. Mean length, absolute growth rates (AGRs) and survival of sandfish juveniles reared in floating hapas at the two sites varied during the study. AGRs were highest at 1.17 ± 0.06 mm day−1 at Bolinao, and 1 ± 0.08 mm day−1 at Maliwaliw, by days 23 and 60, respectively. Mean lengths of sandfish juveniles reared at Bolinao and Maliwaliw by the end of the study were 46.7 ± 0.15 and 58.8 ± 2.4 mm, respectively, and survival at both sites was high at 96% by the end of the study. Negative correlations were observed between the number of individual predators and competitors, and survival and growth rates of sandfish juveniles reared at Bolinao and Maliwaliw, respectively. Our results highlight the importance of predator and competitor management measures and appropriate site selection to optimize growth performance and survival of sandfish juveniles reared in ocean‐based culture production systems.

Nutrient Availability Has a Greater Influence than Pot Host on Seedling Development of Hemiparasitic Hawaiian Sandalwood (Santalum paniculatum Hook. and Arn.)

Sandalwood (Santalum spp.) has been overharvested throughout its range, including the Hawaiian Islands, where 6 of the 19 species Santalum spp. are endemic. As hemiparasitic plant species, Hawaiian sandalwoods require a host plant for optimal forest establishment, yet the importance of a host during seedling development is unclear. Furthermore, understanding interactions between pot hosts and nutrient availability on sandalwood seedling development during nursery culture will help to promote the production of high-quality sandalwood seedlings for restoration and commercial purposes. We evaluated the effects of controlled-release fertilizer (CRF), chelated Fe treatments, and two pot host species (Acacia koa and Dodonaea viscosa) on the seedling development of Hawaiian sandalwood (Santalum paniculatum). Increased nutrient availability (CRF) led to increased dry mass, root collar diameter, shoot height, chlorophyll index, and nutrient status values, confirming that the hemiparasitic S. paniculatum can be successfully grown in early stages of cultivation by providing adequate mineral fertilizers. There was a significant interaction between the nutrient availability and chelated iron treatments associated with increased height, root collar diameter, dry mass, chlorophyll index, Fe concentration, and Fe content when chelated Fe was applied (vs. not) in a nutrient-limiting environment. The pot host treatment did not affect any growth metrics, but it did affect the total count of haustoria, with A. koa-hosted seedlings developing 60.3% more haustoria than D. viscosa-hosted and control seedlings. Our results demonstrate that high-quality S. paniculatum seedlings can be grown in containers by providing adequate nutrition and that S. paniculatum in a nutrient-limiting growing environment may benefit from chelated iron fertilizers.

Potential for Concentrated Microalgae as Replacement Diets for Juvenile Green-Lipped Mussels, Perna canaliculus

The nursery culture of bivalves typically relies on the feeding of costly live microalgae, while the use of natural sources of phytoplankton for feed is uncertain due to their variable quality and abundance. Replacement diets have been applied in bivalve nursery culture to replace live microalgae with varying success. This study investigated the potential use of two concentrated microalgal diets at a range of levels of substitution with live microalgae. Shellfish Diet 1800® (called SD) and LPB™ Frozen Shellfish Diet® (called LPB) were fed to juvenile green-lipped mussels (Perna canaliculus) at five levels of substitution for live microalgae (i.e., 0, 25, 50, 75, and 100%) for 27 days. The mortality of mussels fed with 100% LPB replacement was significantly higher than the mortality of mussels fed at the lower levels of replacement, i.e., 0 and 25%. The overall final size of spat tended to decrease with the increasing level replacement of live microalgae. Proximate analysis (i.e., crude ash-free dry weight, crude protein, crude lipid, and carbohydrate) showed that only the proportion of carbohydrate content of spat was influenced by feeding treatments, with the mean total carbohydrate content of mussels tending to decrease with increasing levels of replacement of live microalgae. The results indicate that both concentrated microalgal feeds (SD and LPB) are effective at replacing live microalgae by up to 50% without compromising the survival and nutritional profile (AFDW, protein, lipid, and carbohydrate content) of juvenile green-lipped mussels and are therefore a useful resource for improving the efficiency of production.

The tradeoff strategy between growth and survival in Quercus variabilis seedlings: determining the most limiting resource in the field drive shoot dieback

Abstract Shoot dieback is an important survival strategy in juvenile Quercus spp. However, it is unknown how nursery practices can influence the regulatory mechanisms of shoot dieback after planting. Furthermore, there is scarce information about the interactive effects between container depth and nursery fertilization on field seedling performance, and in combination with field weed control. Here, Quercus variabilis seedlings were cultivated the first year in with two container depths (25 cm, D40; 36 cm, D60) and with two nitrogen-loading levels (25, N25; 100 mg seedling−1, N100) in the nursery, and the following year, they were out-planted with/without weed elimination. We evaluated first year seedlings’ functional traits after nursery culture (plant and root morphology and nutritional status) and second year field performance (survival, shoot dieback, growth and nutrient increments), and their relationship. Independently of nursery culture, weed management was an irreplaceable practice to optimize seedling field performance. Seedlings grown in deep containers (D60) showed enhanced field growth and nutrient acquisition and reduced shoot dieback. Fertilization increased N and K loading (content and concentration) in the nursery, but showed no effect in the field. Low quality seedlings (low fertilization and normal container) maintained high survival rates at the expense of increasing shoot dieback rate. Thus, field survival did not differ among seedlings with differing nursery practices. Together, deep container and high N fertilization, increased plant nutritional reserves (content) and improved root system development, consequently, mitigating field shoot dieback. Under our experimental conditions, improved seedling quality by the use of deep container (D60) was sufficient to optimize field seedling performance without weed competition. However, both, deep container and nitrogen loading (D60-N100) were the best nursery practices to optimize seedling success without weed control in the field. Our study highlights that shoot dieback is a paramount trade-off strategy between growth and survival, which should be considered as an important indicator for further evaluating seedling field performance.

Aspek Teknis Budidaya Dan Profitabilitas Pendederan Ikan Nila Merah (Oreochromis niloticus) Studi Kasus Di Turbo Farm, Kota Bogor Jawa Barat

Nursery culture of tilapia (Oreochromis niloticus) is an important segment to support a comprehensive tilapia culture business. Requirements for business sustainability involve the high profitability of the company and high growth of the reared fish. This experiment aimed to observe the profitability aspect, fish growth, water quality, and culture techniques applied in a tilapia farm. The experiment was done using case study method, where Turbo farm, located in Bogor West Java, was used as a model. The data collected involved primary data from field observation and secondary data from interview activities. The results showed that tilapia juvenile had a good growth, and that the water quality (temperature and pH) ranged within optimal range for tilapia culture. At stocing density of 2.000 juvenile per production unit in one cycle, the total production was 68.400 juvenile per year, in which 10% of the total produced juvenile were sold at size of 7-8 cm, while the remaining juveniles were at size 11-12 cm. Price of juvenile at size 7-8 cm was half of the size 11-12 cm, Rp 600 vs Rp 1.200 per juvenile, respectively. The profit of the business was Rp 43.989.000 per year with value of revenue/cost (R/C) ratio 2,29, and payback period (PP) 6,27 year. Based on the previously mentioned profitability parameters, the nursery culture of tilapia performed by Turbo farm was profitable. However, an efficiency of facility use was needed to increase profit and shorten the return on investment period.

Improved ocean-based nursery culture of blacklip pearl oyster (Pinctada margaritifera) juveniles in mesh baskets using cyanoacrylate adhesive

The blacklip pearl oyster, Pinctada margaritifera, supports well-established cultured pearl industries throughout the Pacific with various nursery culture methods used to on-grow juvenile oysters to a size suitable for pearl production. Locally-available plastic baskets are commonly used to rear juvenile oysters, but they do not prevent oysters from aggregating, which negatively impacts production. To develop an understanding of how basket-based nursery culture might best be adapted for rearing juvenile P. margaritifera, this study examined growth and survival of juveniles of varying sizes and stocked at varying densities in mesh baskets when using a cyanoacrylate adhesive to prevent aggregation. During a 3.5-month ocean-based nursery culture period, stocking density was shown to have a significant effect on growth (F = 11.53, p < 0.001), yet a minimal influence on oyster survival (χ2 = 5.05, p = 0.28). By contrast, stocking size influenced survival (χ2 = 7.17, p = 0.03), but had minimal impact on growth (F = 3.24, p = 0.08). Given that mean ( ± SD) survival of juveniles ranged from 65.0 ± 14.4% to 94.0 ± 8.2% and dorsoventral shell growth ranged from 13.9 ± 6.2 mm to 19.7 ± 6.3 mm, depending on stocking density and stocking size, these factors clearly merit consideration before fixing juvenile oysters to baskets with an adhesive. Such results broaden our knowledge of nursery culture methods for P. margaritifera and improve options for small-scale pearl farmers in the Pacific.

Using relative return‐on‐effort scoring to evaluate a novel coral nursery in Malaysia

Coral reefs in Malaysia have been degraded by environmental and anthropogenic stressors, and enthusiasm for coral propagation aimed at site restoration is rapidly growing as a local management tool. However, coral propagation activities in the region are in their infancy and little data currently exists to guide and inform effective practices. We therefore established the first multi‐taxa coral tree nursery (6 species and 300 fragments) in Malaysia and tracked survival and growth to determine the relative return‐on‐effort (RRE) over an approximately 14‐month monitoring period. We observed differences in growth and survival among six coral species and were successful at benchmarking results against coral restoration operations globally and in the East Asian Seas region. Major findings include (1) overall ranges in species level survivorship of 34–94% and specific growth rate of 0.14–0.29%/day, leading to variable RRE scores among species, (2) variable growth rates among coral species based on seasonal changes in environmental conditions, (3) similar RRE scores to other nursery locations worldwide, which suggests effective practice, and (4) calculation of RRE scores for species not previously reported in nursery culture (Acropora florida, A. hoeksemai, and Echinopora horrida). Ultimately, our study supports previous findings that RRE is an effective technique for comparing coral nursery performance and offers valuable insight to guide future restoration activities in Malaysia.

Quantifying baseline costs and cataloging potential optimization strategies for kelp aquaculture carbon dioxide removal

To keep global surface warming below 1.5°C by 2100, the portfolio of cost-effective CDR technologies must expand. To evaluate the potential of macroalgae CDR, we developed a kelp aquaculture bio-techno-economic model in which large quantities of kelp would be farmed at an offshore site, transported to a deep water “sink site”, and then deposited below the sequestration horizon (1,000 m). We estimated the costs and associated emissions of nursery production, permitting, farm construction, ocean cultivation, biomass transport, and Monitoring, Reporting, and Verification (MRV) for a 1,000 acre (405 ha) “baseline” project located in the Gulf of Maine, USA. The baseline kelp CDR model applies current systems of kelp cultivation to deep water (100 m) exposed sites using best available modeling methods. We calculated the levelized unit costs of CO2eq sequestration (LCOC; $ tCO2eq-1). Under baseline assumptions, LCOC was $17,048 tCO2eq-1. Despite annually sequestering 628 tCO2eq within kelp biomass at the sink site, the project was only able to net 244 C credits (tCO2eq) each year, a true sequestration “additionality” rate (AR) of 39% (i.e., the ratio of net C credits produced to gross C sequestered within kelp biomass). As a result of optimizing 18 key parameters for which we identified a range within the literature, LCOC fell to $1,257 tCO2eq-1 and AR increased to 91%, demonstrating that substantial cost reductions could be achieved through process improvement and decarbonization of production supply chains. Kelp CDR may be limited by high production costs and energy intensive operations, as well as MRV uncertainty. To resolve these challenges, R&amp;amp;D must (1) de-risk farm designs that maximize lease space, (2) automate the seeding and harvest processes, (3) leverage selective breeding to increase yields, (4) assess the cost-benefit of gametophyte nursery culture as both a platform for selective breeding and driver of operating cost reductions, (5) decarbonize equipment supply chains, energy usage, and ocean cultivation by sourcing electricity from renewables and employing low GHG impact materials with long lifespans, and (6) develop low-cost and accurate MRV techniques for ocean-based CDR.

Coral micro-fragmentation assays for optimizing active reef restoration efforts.

The global decline of coral reefs has driven considerable interest in active coral restoration. Despite their importance and dominance on mature reefs, relatively few coral restoration projects use slower growth forms like massive and encrusting coral species. Micro-fragmentation can increase coral cover by orders of magnitude faster than natural growth, which now allows cultivation of slow growing massive forms and shows promise and flexibility for active reef restoration. However, the major causes of variation in growth and survival of outplanted colonies remain poorly understood. Here, we report simple outplanting assays to aid in active reef restoration of slower growing species and increase the likelihood of restoration success. We used two different micro-fragmentation assays. Pyramid assays were used to examine variation associated with fragment size (ranging from ≈1–9 cm2), nursery residence time (for both in-situ and ex-situ nurseries), and 2D vs. 3D measurements of growth. Block assays were used to examine spatial variation among individual performance at outplanting sites in the field. We found 2D and 3D measurements correlated well, so measured survivorship and growth using top-down planar images for two of the main Hawaiian reef building corals, the plating Montipora capitata and the massive Porites compressa. Pyramid assays housed and outplanted from the in-situ nursery showed no effect of residence time or size on overall survivorship or growth for either species. Results from the ex-situ nursery, however, varied by species, with P. compressa again showing no effect of nursery residence time or size on survivorship or growth. In contrast, nursery culture resulted in improved survivorship of small M. capitata fragments, but net growth showed a weak positive effect of nursery time for medium fragments. Small fragments still suffered higher mortality than either medium or large fragments. Due to their lower mortality, medium fragments (≈3 cm2) appear to be the best compromise between growth and survivorship for outplanting. Likewise, given weak positive gains relative to the investment, our results suggest that it could be more cost-effective to simply outplant medium fragments as soon as possible, without intermediate culture in a nursery. Furthermore, the block assay revealed significant differences in survivorship and growth among sites for individuals of both species, emphasizing the importance of considering spatial variation in coral survival and growth following outplanting. These results highlight the value of using short-term micro-fragmentation assays prior to outplanting to assess size, and location specific performance, optimizing the efficiency of active reef restoration activities and maximizing the probability of success for active coral restoration projects.

Microencapsulated diets using thraustochytrids and macroalgae side streams for nursery rearing of Mytilus galloprovincialis spat

AbstractGlobal expansion of bivalve aquaculture can drive sustainable protein production. Inland culture of mussel spat can play an important role in supporting extensive mussel farming. Nursery culture of bivalves is, however, dependent on nutritious, cost‐efficient, and more reliable diets for spat. The aim of this study was to assess the impact of dietary alternatives to commercial algal feeds (Shellfish Diet 1800) on the survival and growth of Mytilus galloprovincialis spat, widely farmed in Europe. Spat (6.8 ± 1.1 mm) were supplied with different diets for 6 weeks: commercial microalgal diet (A), microencapsulated feeds containing a 1:1 blend of the macroalga Undaria pinnatifida and the microalga Schizochytrium (BioBullets; BB), or commercial microalgae and BioBullets combined (ABB). Unsupplemented spat showed no growth and little change in body condition (CI). Spat fed microcapsules grew at comparable rates, and body condition rose at higher levels (shell growth rates: 8.5 ± 3.7 μm day−1; ΔCI: 6.1 ± 1.1%) relative to those fed commercial microalgae (8.5 ± 5.7 μm day−1; ΔCI: 3.3 ± 0.8%). Supplementing microencapsulated feeds with the commercial microalgal diet did not significantly improve growth performances (9.3 ± 2.3 μm day−1; ΔCI: 4.7 ± 1.4%) relative to mussels fed microcapsules alone. Microencapsulated feeds for M. galloprovincialis spat production can significantly reduce nursery costs compared with commercial feeds or cultured microalgae. By sourcing encapsulated algae from aquaculture side streams, microencapsulated feeds can further promote circular economies.

Probiotic additions affect the biofloc nursery culture of white shrimp (Litopenaeus vannamei)

In a biofloc technology (BFT) system, the bacterial community is crucial for organic matter metabolism and toxic nitrogenous compound recycling. This study evaluated the effects of the addition of either of two commercial probiotics (P1 and P2) on the biofloc condition, water quality, and growth and survival of white shrimp ( Litopenaeus vannamei ) in indoor BFT systems; indoor BFT systems without the addition of any probiotic was used as the control. The culture density was 150 juvenile shrimp (weight, 0.06 ± 0.01 g) in 200-L tanks with a culture period of 40 days. The salinity of the culture water was 15 ppt, and molasses was added to the tank for maintaining a C/N ratio of 15. In the P1, P2, and control groups, the floc volume was 3.7 ± 0.5, 3.5 ± 0.6, and 3.0 ± 0.6 mL/L, respectively, and the total heterotrophic bacterium densities were (5.8 ± 1.4) × 10 6 , (4.5 ± 1.5) × 10 6 , and (3.6 ± 1.1) × 10 6 colony forming unit (CFU)/mL, respectively; these values were significantly higher in the treatment groups than in the control group (all P < 0.05). The major groups in the biofloc comprised zooplankton community were provided by rotifers, copepods, nematodes , and protists . The addition of probiotics increased nitrite‑nitrogen and nitrate‑nitrogen levels in the culture water of P1 (7.7 ± 1.0 and 5.9 ± 0.5 ppm, respectively) and P2 (8.4 ± 0.7 and 6.2 ± 0.6 ppm, respectively) groups; they were significantly higher in the treatment groups than in the control group (6.1 ± 0.8 and 5.0 ± 0.8 ppm, respectively). L. vannamei growth rates were significantly higher in the P1 group than in the P2 and control groups. However, the between-group differences in the survival rates were not significant. In conclusion, the addition of probiotics to the BFT system with L. vannamei effectively enhanced the water quality, floc volume, and total bacterial number in the water and the growth performance of the shrimp. • Both probiotics resulted in higher floc volumes and total heterotrophic bacteria. • Both probiotics increased NIN and NAN in water. • P1 increased growth performance (weight gain and FCR); P2 and control did not. • Vibrio harveyi challenge provided no significant differences among treatments.

Effect of Distillery Spent Wash at Different C/N Ratio on Biofloc based Nursery Culture of Penaeus vannamei

Background: Biofloc technology is one of the methods to overcome the problems associated with high ammonia-nitrogen and nitrate-nitrogen concentration in the water. The addition of carbon source is one of the practical ways to increase the C/N ratio and to promote the floc development in the culture system. The present research was carried out to assess the effect of distillery spent wash (DSW) at different C/N ratios on floc formation and growth of the shrimp under an intensive culture system. Methods: A 35-day experiment was conducted to study the effect of DSW at different C/N ratios (10, 15, 20 and 25) on the development of biofloc in the nursery culture of Penaeus vannamei. Floc development, water quality and growth performance of P. vannamei were also studied. Result: It was observed that significantly (p less than 0.05) higher specific growth rate (12.03±0.15), survival, final weight gain and better feed conversion ratio (1.25±0.02) of the shrimp at C/N 15 treatment. The study also recorded an increase in C/N ratio decreases the growth performance of the shrimp. The present study reported that, in a DSW based biofloc system, C/N ratio of 15 showed a positive effect on water quality parameters, survival and enhanced growth of cultured shrimp.

Induction of adventitious buds and establishment of an efficient regeneration system in Polygonatum cyrtonema Hua

Polygonatum cyrtonema Hua is not only a widely used traditional Chinese medicine, but also processed into food and cosmetics. However, its large-scale cultivation and application are limited by the low reproduction rate for traditional artificial propagation technology. Therefore, the aim of this study was to establish an efficient and stable adventitious buds induction system for P. cyrtonema by using one bud rhizome segment as initial explants. The results showed that the optimal medium for the rhizome growth, adventitious buds occurrence and proliferation was MS medium supplemented with 3.0 mg·L–1 BA, 1.0 mg·L–1 NAA and 1.0 mg·L–1 KT, with a proliferation coefficient of 6.5. The best rooting medium was found to be half strength of MS medium with 0.5–1.0 mg·L–1 NAA. The survival rate was higher than 95%. Finally, an asexual rapid propagation system of P. cyrtonema was established, which can provide the technical basis for the development of nursery culture.

Yeast Meyerozyma guilliermondii inoculation in mature and heterotrophic biofloc systems for Litopenaeus vannamei nursery rearing exhibits bioremediation potential and improvement of shrimp survival

This study aimed to isolate a yeast strain and evaluate its potential to be inoculated in the biofloc technology culture of Pacific white shrimp employing in vitro and in vivo assays. A yeast strain identified as Meyerozyma guilliermondii (CPQBA 1459/17 DRM-01) was isolated from the soil of an estuary. Its growth kinetics under different salinities (0%, 1.0%, 2.0%, 3.0% NaCl) and Vibrio alginolyticus inhibition were evaluated in vitro. For the in vivo assay, a factorial design was employed to evaluate the effects of yeast addition and biofloc management strategy in the nursery culture of Litopenaeus vannamei as regards shrimp growth performance, water quality and water microbiology. The two factors evaluated were biofloc (mature and heterotrophic) and yeast (addition or no addition), totaling four treatments. In the in vitro trials, the yeast strain was capable of growing under all salinities evaluated, but no pathogen inhibition was observed. In the in vivo experiment, the addition of yeast significantly reduced the concentration of total suspended solids (p < 0.05), in addition to promoting a higher post-larvae survival when considering only the two mature biofloc treatments (p < 0.05). No significant effects on water Vibrio spp. and total heterotrophic bacteria counts were found (p ≥ 0.05). In conclusion, the inoculation of yeast in the biofloc culture of L. vannamei exhibited bioremediation potential and improvement in shrimp survival, the latter being modulated by the biofloc management strategy.