# Scallop Hatchery and Suspended Culture ## Key Takeaways - Broodstock conditioning requires precise temperature control (2-4°C above ambient, not exceeding 18°C for temperate species) and a mixed algal diet (e.g., *Isochrysis galbana*, *Chaetoceros muelleri*, *Pavlova lutheri*) at 2-4% of dry body weight to achieve a condition index above 0.15 for optimal gamete quality. - Larval rearing success hinges on controlled stocking densities (5-10 larvae/mL), precise algal feed concentrations (10,000-50,000 cells/mL), and strict water quality management (ammonia, nitrite, pH) to prevent bacterial contamination and nutritional deficiencies leading to poor metamorphosis. - Spat collection and nursery phases necessitate careful management of settlement substrate and density (100-500 spat/collector) to avoid overcrowding-induced stunted growth, with genetic potential for growth improvement noted in Yesso scallop (*Patinopecten yessoensis*) with heritability estimates for shell height ranging from 0.328-0.853. - Suspended grow-out in lantern nets or ear hanging systems is critically influenced by stocking density and temperature, with density-dependent growth suppression observed above a 10-15°C thermal threshold, leading to significantly reduced growth rates at higher densities (e.g., 75% higher in low-density nets for Atlantic sea scallop). - Biofouling control through regular cleaning (every 4-8 weeks) and predator exclusion are essential for maintaining water flow and food availability, mitigating competition and weight increase on culture gear, thereby preventing poor growth and increased mortality. - Environmental monitoring of water temperature, salinity, dissolved oxygen, and chlorophyll a is paramount, with sites selected for moderate current velocities (0.1-0.5 m/s) and avoidance of high sediment loads or pollution to optimize growth and minimize stress. --- This article provides a practical guide for aquaculture farmers on scallop hatchery operations and suspended culture methods, covering broodstock conditioning, spawning, larval rearing, spat collection, and grow-out in lantern nets and ear hanging systems. The focus is on evidence-based management decisions, record keeping, and common failure patterns to improve production outcomes. ## At a Glance | Production Stage | Key Management Decision | Critical Monitoring Parameter | Common Failure Point | |---|---|---|---| | Broodstock conditioning | Temperature and feeding regime 4-8 weeks before spawning | Gonad development stage and condition index | Poor gamete quality from inadequate nutrition or thermal stress | | Larval rearing | Stocking density and algal feed concentration | Larval shell height and survival at each stage | Bacterial contamination or nutritional deficiency causing poor metamorphosis | | Spat collection and nursery | Settlement substrate type and timing | Spat density per collector and growth rate | Overcrowding leading to stunted growth or detachment | | Grow-out in suspended culture | Stocking density in lantern nets or ear hanging | Shell height growth rate and mortality per tier | Density-dependent growth suppression above 10-15°C thermal threshold | ## Broodstock Selection and Conditioning ### Source and Health Assessment Select broodstock from known disease-free populations or certified hatchery lines. Wild-caught scallops require a quarantine period of at least 14 days to observe for signs of disease or stress. Record the source location, collection date, shell height, and any visible abnormalities. The FAO provides guidance on cultured species selection and health management for bivalve hatcheries (www.fao.org/fishery/en/culturedspecies). Maintain individual records for each broodstock batch, including water temperature, salinity, and feeding rates during conditioning. ### Conditioning Protocols Condition broodstock for 4 to 8 weeks before the planned spawning date. Hold scallops in flow-through or recirculating systems with temperature adjusted to 2-4°C above ambient collection temperature, not exceeding 18°C for temperate species. Feed a mixed algal diet of *Isochrysis galbana*, *Chaetoceros muelleri*, and *Pavlova lutheri* at a ration of 2-4% of broodstock dry body weight per day. Monitor gonad development weekly by visual inspection or biopsy. A condition index (dry meat weight to shell weight ratio) above 0.15 indicates readiness for spawning. The USDA Agricultural Research Service supports research on bivalve nutrition and hatchery technologies (www.ars.usda.gov/animal-production-and-protection/aquaculture). ### Spawning Induction Induce spawning using thermal shock (alternating 3-4°C temperature cycles), chemical stimulation with hydrogen peroxide at 0.005-0.01% concentration, or a combination of methods. Place individual scallops in separate containers to prevent polyspermy and to track parentage for selective breeding programs. Record the time of spawning, number of eggs released, and fertilization success rate. A fertilization rate below 80% indicates poor gamete quality or environmental stress. Remove adults after spawning and incubate eggs in clean seawater at the species-specific optimal temperature, typically 14-18°C for temperate scallops. ## Larval Rearing ### Larval Culture System Maintain larvae in conical-bottom tanks with gentle aeration and flow-through or static water exchange. Stock D-stage larvae at 5-10 larvae per milliliter. Change 50-100% of water volume daily, depending on water quality parameters. Monitor ammonia, nitrite, and pH levels every 48 hours. The FAO Animal Production and Health division provides resources on aquatic animal health management (www.fao.org/animal-production/en). Record daily larval shell height, survival, and feeding rates. ### Feeding and Nutrition Feed larvae a mixed algal diet of *Isochrysis galbana* (T-ISO) and *Chaetoceros calcitrans* at concentrations increasing from 10,000 to 50,000 cells per milliliter as larvae grow. Adjust ration based on gut fullness observed under a microscope. Underfeeding causes slow growth and poor metamorphosis, overfeeding leads to bacterial blooms and larval mortality. A study on lion's paw scallop (*Nodipecten nodosus*) postmetamorphic growth found that food supply significantly influences survival and growth rates after settlement (Influence of food supply on postmetamorphic growth and survival of hatchery-produced lion's paw scallop, *Journal of Shellfish Research*, 2004, www.api.elsevier.com/content/abstract/scopus_id/2442435679). ### Water Quality and Disease Management Maintain temperature within 1°C of the optimal range for the species, salinity at 30-34 ppt, and dissolved oxygen above 5 mg/L. Use UV-treated or filtered seawater to reduce bacterial loads. Common larval diseases include vibriosis, which causes shell deformities and sudden mortality. Quarantine any tank showing signs of disease and escalate to a veterinary specialist if mortality exceeds 20% in 24 hours. The USDA National Agricultural Library provides resources on animal health and welfare in aquaculture (www.nal.usda.gov/animal-health-and-welfare). ### Metamorphosis and Settlement When larvae develop an eyespot and foot (typically 18-25 days post-fertilization for temperate species), introduce settlement substrate such as monofilament line, plastic mesh, or conditioned scallop shells. Stock settlement tanks at 1-2 larvae per milliliter. Provide a thin layer of sand or shell hash on the tank bottom for species that require substrate contact. Record the percentage of larvae that successfully metamorphose into spat. A settlement rate below 30% indicates poor larval condition or inappropriate substrate. ## Spat Collection and Nursery ### Collector Design and Placement Use spat collectors made of monofilament netting or plastic mesh bags filled with shade cloth or coconut fiber. Place collectors in the hatchery or in the field at depths of 3-10 meters, depending on local water quality and predator presence. Deploy collectors when water temperature is within the optimal range for the species, typically 14-20°C. Record the deployment date, depth, and location for each collector. ### Spat Density Management Monitor spat density on collectors every 2-4 weeks. Optimal density ranges from 100 to 500 spat per collector, depending on species and collector size. Overcrowding causes stunted growth and increased mortality. Thin spat to lower densities if growth rates fall below 0.5 mm per week. A study on Yesso scallop (*Patinopecten yessoensis*) in suspended culture found that heritability estimates for shell height at specific ages ranged from moderate to high (0.328-0.853), indicating genetic potential for growth improvement through selective breeding (Genetic Evaluation of Growth and Survival-Related Traits in Yesso Scallop, *Frontiers in Marine Science*, 2022, www.doi.org/10.3389/fmars.2022.865736). ### Nursery Grow-Out Transfer spat to nursery systems such as pearl nets, lantern nets, or upwellers when they reach 2-5 mm shell height. Stock at 500-1000 individuals per net for pearl nets or 100-200 per tier for lantern nets. Feed a mixed algal diet or rely on natural phytoplankton if in flow-through systems. Record weekly growth rates and mortality. Escalate to a nutrition specialist if growth rates are below 0.3 mm per week for two consecutive weeks. ## Suspended Culture Systems ### Lantern Net Culture Lantern nets consist of multiple tiers (typically 4-10) made of plastic mesh with a central support line. Stock scallops at densities of 10-20 individuals per tier for grow-out to market size. A study on Atlantic sea scallop (*Placopecten magellanicus*) in suspended culture found that during summer, growth rates were 75% higher in low-density nets (10 individuals per tier) compared to high-density nets (20 individuals per tier) (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). The same study identified an optimal growth temperature window of 10-15°C, with a distinct negative relationship between temperature and growth above this threshold. ### Ear Hanging Culture Ear hanging involves drilling a small hole in the scallop's ear (the wing-like projection near the hinge) and threading a monofilament line through it. Hang scallops at 10-20 cm intervals on a longline. This method provides better water flow and reduces biofouling compared to lantern nets. Use scallops of 30-50 mm shell height for ear hanging. Record the number of scallops per line, mortality, and growth rates monthly. ### Site Selection and Environmental Monitoring Select sites with moderate current velocities (0.1-0.5 m/s), adequate food availability (chlorophyll a > 1 μg/L), and temperatures within the optimal range for the species. Avoid areas with high sediment loads or pollution. A study on high-density suspended aquaculture in Sungo Bay, China, found that scallop culture zones reduced current velocities by up to 65% in the culture layer, which can affect food supply and waste removal (Impacts of High-Density Suspended Aquaculture on Water Currents, *Journal of Marine Science and Engineering*, 2022, www.doi.org/10.3390/jmse10081151). Monitor water temperature, salinity, dissolved oxygen, and chlorophyll a at the culture depth weekly. ### Stocking Density Management Adjust stocking density based on scallop size, water temperature, and food availability. A meta-analysis comparing suspended and bottom culture for pectinid scallops found that suspended culture has a significant positive effect on growth, with higher growth rates observed in suspended systems (Positive Effect of Suspended Culture to the Growth of Pectinid, *Bicol University Research and Development Journal*, 2020, www.doi.org/10.47789/burdj.mbtcbbgs.20192202.1). However, density-dependent growth suppression occurs at high densities, especially during warm months. Thin nets in spring before water temperatures exceed 15°C to avoid handling stress during summer. ## Grow-Out Management ### Feeding and Nutrition Scallops in suspended culture rely on natural phytoplankton for nutrition. In areas with low primary productivity, supplemental feeding with microalgae may be necessary. Monitor scallop condition by measuring meat weight to shell weight ratio monthly. A condition index below 0.10 indicates poor nutrition or environmental stress. Escalate to a nutrition specialist if condition index remains low for two consecutive months. ### Biofouling Control Biofouling organisms such as barnacles, mussels, and algae compete for food and space, reduce water flow, and increase weight on culture gear. Clean nets and ear hanging lines every 4-8 weeks during the growing season. Use high-pressure water jets or manual scraping. Avoid chemical antifoulants as they can accumulate in scallop tissue. Record biofouling species and severity to inform cleaning schedules. ### Predator and Disease Management Common predators include starfish, crabs, and octopus. Use predator exclusion nets or elevate culture gear off the bottom. Monitor for signs of disease such as shell deformities, gaping, or unusual mortality. Common diseases include vibriosis, Perkinsus, and herpes-like viruses. Quarantine affected animals and escalate to a veterinary specialist if mortality exceeds 10% in a week. The USDA National Agricultural Library provides resources on aquatic animal health (www.nal.usda.gov/animal-health-and-welfare). ### Harvest Timing Harvest scallops when they reach market size, typically 80-100 mm shell height for most species. Harvest in cool months (below 15°C) to reduce stress and improve meat quality. Record harvest date, number of scallops, average shell height, and meat weight. A study on Yesso scallop found that heritability for body weight at harvest in suspended culture ranged from 0.328 to 0.853, indicating potential for genetic improvement through selective breeding (Genetic Evaluation of Growth and Survival-Related Traits in Yesso Scallop, *Frontiers in Marine Science*, 2022, www.doi.org/10.3389/fmars.2022.865736). ## Records and Measurements ### Essential Records Maintain the following records for each production cycle: - Broodstock source, conditioning start date, temperature, feeding rate, and spawning date - Larval rearing tank number, stocking density, daily mortality, and shell height measurements - Spat collector deployment date, location, depth, and spat density - Grow-out system type, stocking density per net or line, and cleaning schedule - Water quality parameters (temperature, salinity, dissolved oxygen, pH, chlorophyll a) at least weekly - Mortality events with date, number, and suspected cause - Harvest date, number of scallops, average shell height, and meat weight ### Growth Monitoring Measure shell height (from hinge to the opposite shell margin) on a sample of 30-50 scallops per net or line monthly. Calculate specific growth rate as (ln(SH2) - ln(SH1)) / (t2 - t1) x 100, where SH is shell height in mm and t is time in days. Compare growth rates to benchmarks for the species and site. A growth rate below 0.5 mm per day during the optimal temperature window indicates a problem. ### Condition Index Calculate condition index as (dry meat weight / dry shell weight) x 100. Sample 10-20 scallops per net or line monthly. A condition index below 10% indicates poor nutrition or environmental stress. Escalate to a nutrition specialist if condition index is below 10% for two consecutive months. ## Common Failure Patterns ### Poor Larval Survival Causes include bacterial contamination, nutritional deficiency, or temperature stress. Prevention measures include UV treatment of seawater, use of axenic algal cultures, and maintaining stable temperature within 1°C of optimal. If larval survival is below 20% at metamorphosis, review water quality records and algal feed quality. ### Density-Dependent Growth Suppression High stocking density in lantern nets reduces growth rates, especially during warm months. A study on Atlantic sea scallop found that growth rates were 75% higher in low-density nets during summer (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). Stock nets at low densities in spring to avoid thinning during peak temperatures. ### Biofouling Overgrowth Heavy biofouling reduces water flow and food availability, leading to poor growth and increased mortality. Clean nets every 4-8 weeks during the growing season. In areas with heavy biofouling pressure, consider using ear hanging culture, which has less surface area for fouling organisms. ### Environmental Stress High temperatures above 15°C reduce growth and increase mortality. A study on Atlantic sea scallop found a distinct negative relationship between temperature and growth above 10-15°C (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). Select sites that maximize time within the optimal thermal envelope, such as mouths of estuaries and bays. ## Welfare and Safety Context ### Animal Welfare Scallops are sentient animals and should be handled with care to minimize stress. Avoid handling during summer months when temperatures are high, as this can cause mortality. A study on Atlantic sea scallop recommended that growers stock nets at low densities in spring to avoid thinning during peak temperatures (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). Provide adequate water flow and food availability to support normal growth and behavior. ### Worker Safety Working on water presents risks of drowning, hypothermia, and injury from equipment. Wear personal flotation devices at all times when on boats or near water. Use proper lifting techniques to avoid back injury when handling heavy nets. Train workers in emergency procedures and first aid. The USDA National Agricultural Library provides resources on agricultural safety (www.nal.usda.gov/animal-health-and-welfare). ### [Food Safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) Scallops can accumulate biotoxins from harmful algal blooms. Monitor local harmful algal bloom warnings and test scallop meat for toxins before harvest. Maintain records of harvest location and date for traceability. Follow local regulations for shellfish sanitation and processing. ## Professional Escalation Criteria Escalate to a veterinary specialist if: - Mortality exceeds 20% in 24 hours in larval tanks or 10% in a week in grow-out systems - Unusual lesions, shell deformities, or behavioral changes are observed - Disease is suspected and cannot be identified with available resources Escalate to a nutrition specialist if: - Growth rates are below 0.3 mm per week for two consecutive weeks in nursery or grow-out - Condition index is below 10% for two consecutive months - Poor larval survival or metamorphosis is suspected to be nutrition-related Escalate to an environmental specialist if: - Water quality parameters are consistently outside optimal ranges - Harmful algal blooms are detected in the culture area - Unexplained mortality events occur across multiple nets or lines ## Frequently Asked Questions ### What is the optimal temperature for scallop larval rearing? The optimal temperature for scallop larval rearing depends on the species. For temperate species such as Atlantic sea scallop and Yesso scallop, the optimal range is typically 14-18°C. A study on Atlantic sea scallop found that optimal growth occurred within a window of 10-15°C for grow-out, with a negative relationship between temperature and growth above this threshold (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). Maintain temperature within 1°C of the optimal range during larval rearing. ### How do I prevent density-dependent growth suppression in lantern nets? Stock lantern nets at low densities in spring before water temperatures exceed 15°C. A study on Atlantic sea scallop found that during summer, growth rates were 75% higher in low-density nets (10 individuals per tier) compared to high-density nets (20 individuals per tier) (The coupled effects of stocking density and temperature on Sea Scallop growth in suspended culture, *Aquaculture Reports*, 2021, www.doi.org/10.1016/J.AQREP.2021.100684). Avoid handling during summer and early fall as this may lead to mortality. ### What is the difference between lantern net and ear hanging culture? Lantern nets consist of multiple tiers made of plastic mesh that hold scallops in a stacked configuration. Ear hanging involves drilling a hole in the scallop's ear and threading a monofilament line through it. Ear hanging provides better water flow and reduces biofouling compared to lantern nets. A meta-analysis found that suspended culture has a significant positive effect on growth compared to bottom culture (Positive Effect of Suspended Culture to the Growth of Pectinid, *Bicol University Research and Development Journal*, 2020, www.doi.org/10.47789/burdj.mbtcbbgs.20192202.1). ### How do I select a site for suspended scallop culture? Select sites with moderate current velocities (0.1-0.5 m/s), adequate food availability (chlorophyll a > 1 μg/L), and temperatures within the optimal range for the species. Avoid areas with high sediment loads or pollution. A study on high-density suspended aquaculture found that scallop culture zones reduced current velocities by up to 65% in the culture layer, which can affect food supply and waste removal (Impacts of High-Density Suspended Aquaculture on Water Currents, *Journal of Marine Science and Engineering*, 2022, www.doi.org/10.3390/jmse10081151). Choose sites at the mouths of estuaries and bays for a combination of sufficient depth and space. ### What records should I keep for scallop hatchery and culture? Maintain records for broodstock source and conditioning, larval rearing parameters, spat collector deployment, grow-out system type and stocking density, water quality parameters, mortality events, and harvest data. Record shell height measurements monthly and calculate specific growth rate. A study on Yesso scallop used growth rings in the outer shells to longitudinally evaluate shell heights at 6, 10, 16, and 20 months (Genetic Evaluation of Growth and Survival-Related Traits in Yesso Scallop, *Frontiers in Marine Science*, 2022, www.doi.org/10.3389/fmars.2022.865736). ### How do I manage biofouling in suspended culture? Clean nets and ear hanging lines every 4-8 weeks during the growing season using high-pressure water jets or manual scraping. Avoid chemical antifoulants as they can accumulate in scallop tissue. In areas with heavy biofouling pressure, consider using ear hanging culture, which has less surface area for fouling organisms. Record biofouling species and severity to inform cleaning schedules. ### What are the common diseases in scallop hatcheries? Common diseases include vibriosis, which causes shell deformities and sudden mortality in larvae, and Perkinsus, which affects adult scallops. Quarantine any tank showing signs of disease and escalate to a veterinary specialist if mortality exceeds 20% in 24 hours. The USDA National Agricultural Library provides resources on aquatic animal health (www.nal.usda.gov/animal-health-and-welfare). ### When should I harvest scallops in suspended culture? Harvest scallops when they reach market size, typically 80-100 mm shell height for most species. Harvest in cool months (below 15°C) to reduce stress and improve meat quality. Record harvest date, number of scallops, average shell height, and meat weight. A study on Yesso scallop found heritability estimates for body weight at harvest in suspended culture ranged from 0.328 to 0.853, indicating potential for genetic improvement (Genetic Evaluation of Growth and Survival-Related Traits in Yesso Scallop, *Frontiers in Marine Science*, 2022, www.doi.org/10.3389/fmars.2022.865736). ## Related Farming Guides - [Systems Biology](/blog/news/systems-biology) - [Recirculating Aquaculture System Basics](/knowledge/animal-farming/aquaculture/recirculating-aquaculture-system-basics) - [Aquaponics Fish Health And System Management](/knowledge/animal-farming/aquaculture/aquaponics-fish-health-and-system-management) - [Veal Production Systems Housing Nutrition And Welfare](/knowledge/animal-farming/beef-cattle/veal-production-systems-housing-nutrition-and-welfare) - [Aquaculture Temperature Management And Seasonal Planning](/knowledge/animal-farming/aquaculture/aquaculture-temperature-management-and-seasonal-planning) ## Related Clinical & Scientific Guides * [Pond Sediment Management and Dredging Options](/knowledge/animal-farming/aquaculture/pond-sediment-management-dredging-options) * [Indoor Aquaculture Facilities: Lighting and Insulation](/knowledge/animal-farming/aquaculture/indoor-aquaculture-facilities-lighting-insulation) * [Greenhouse Aquaculture: Extending Growing Seasons](/knowledge/animal-farming/aquaculture/greenhouse-aquaculture-extending-growing-seasons) ## References and Further Reading - [www.fao.org](https://www.fao.org/fishery/en/culturedspecies) - [www.ars.usda.gov](https://www.ars.usda.gov/animal-production-and-protection/aquaculture) - [FAO Animal Production and Health](https://www.fao.org/animal-production/en). Food and Agriculture Organization of the United Nations. - [Animal Health and Welfare](https://www.nal.usda.gov/animal-health-and-welfare). USDA National Agricultural Library. - [The coupled effects of stocking density and temperature on Sea Scallop (Placopecten magellanicus) growth in suspended culture](https://doi.org/10.1016/J.AQREP.2021.100684). Aquaculture Reports, 2021. - [Genetic Evaluation of Growth and Survival-Related Traits in Yesso Scallop Patinopecten yessoensis in Sea-Based Culture System](https://doi.org/10.3389/fmars.2022.865736). Frontiers in Marine Science, 2022. - [Impacts of High-Density Suspended Aquaculture on Water Currents: Observation and Modeling](https://doi.org/10.3390/jmse10081151). Journal of Marine Science and Engineering, 2022. - [Positive Effect of Suspended Culture to the Growth of Pectinid](https://doi.org/10.47789/burdj.mbtcbbgs.20192202.1). Bicol University Research and Development Journal, 2020. - [Scallops and Scallop Aquaculture in China](https://doi.org/10.1016/B978-0-444-62710-0.00022-5). Developments in Aquaculture and Fisheries Science, 2016. - [Scallop Aquaculture and Fisheries in Venezuela](https://doi.org/10.1016/B978-0-444-62710-0.00027-4). Developments in Aquaculture and Fisheries Science, 2016. - [European Aquaculture](https://doi.org/10.1016/B978-0-444-62710-0.00020-1). Developments in Aquaculture and Fisheries Science, 2016. - [Scallop growout using a new bottom-culture system](https://doi.org/10.1016/S0044-8486%2800%2900362-8). Aquaculture, 2000. - [Response and condition of larvae of the scallops Nodipecten subnodosus and Argopecten ventricosus reared at the hatchery with different seawater sources](https://doi.org/10.1016/j.aquaculture.2009.08.028). Aquaculture, 2009. - [Influence of food supply on postmetamorphic growth and survival of hatchery-produced lion's paw scallop, Nodipecten nodosus (Linnaeus, 1758)](https://api.elsevier.com/content/abstract/scopus_id/2442435679). Journal of Shellfish Research, 2004. > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.