Acartia tonsa - Premier Calanoid Copepod for Marine Aquaculture & Fish Larviculture

Scientific Classification & Taxonomy

Kingdom: Animalia | Phylum: Arthropoda | Subphylum: Crustacea | Class: Maxillopoda | Subclass: Copepoda | Order: Calanoida | Family: Acartiidae | Genus: Acartia | Species: A. tonsa

Complete Acartia tonsa Species Profile for Marine Aquaculture

Acartia tonsa represents the most widely used calanoid copepod species in commercial marine fish hatcheries worldwide, serving as the industry standard for larviculture operations producing grouper, snapper, sea bass, sea bream, pompano, cobia, halibut, cod, and dozens of other commercially valuable marine fish species. This cosmopolitan species occurs naturally in temperate and subtropical coastal waters throughout Atlantic Ocean, Mediterranean Sea, Baltic Sea, and introduced Pacific locations.

Adult Acartia tonsa measure 0.9-1.4 millimeters in body length, with females (1.1-1.4mm) larger than males (0.9-1.2mm). This moderate size fills a critical gap between rotifers (too small, 100-300 micrometers) and Artemia nauplii (too large, 400-500 micrometers), providing ideal prey for marine fish larvae during critical developmental stages.

Body coloration ranges from transparent to pale cream or light tan. The semi-transparent appearance makes Acartia less visible than bright orange Tigriopus californicus, but active swimming behavior ensures fish detect copepods through movement patterns. The body structure is characteristic of calanoid copepods - elongated tear-drop shape with prominent cephalothorax, narrow abdomen, and distinctive long first antennae. Female Acartia typically broadcast spawn, releasing free-floating eggs directly into water column.

Pelagic Lifestyle and Behavioral Characteristics

Acartia tonsa exhibits strictly pelagic (free-swimming) lifestyle, remaining continuously suspended in water column through constant swimming. Unlike benthic harpacticoid copepods (Tigriopus, Tisbe), Acartia never associates with substrates, living exclusively in planktonic realm. This behavior precisely mimics natural prey presentation marine fish larvae encounter in ocean environments, triggering instinctive feeding responses. Research consistently demonstrates higher larval feeding success on planktonic copepods versus benthic species.

Environmental Requirements and Tolerance

Salinity: 5-40 ppt tolerance, optimal reproduction at 15-30 ppt. Culture at 25-35 ppt for marine larviculture, 20-25 ppt for cost optimization reducing salt expenses 20-40%.

Temperature: 5-30°C (41-86°F) tolerance. Temperate strains optimal 15-20°C (59-68°F), subtropical strains 20-25°C (68-77°F), maximum production 18-22°C (64-72°F). Broad tolerance makes Acartia suitable for temperate species (cod, halibut, sea bass) and tropical species (grouper, snapper, cobia).

Water Quality Requirements:

• Ammonia/Nitrite: Must be 0 ppm - highly toxic
• Nitrate: <20 mg/L preferred, <50 mg/L maximum
• Dissolved Oxygen: >6 mg/L required, >7 mg/L optimal
• pH: 7.8-8.4 optimal

Planktonic copepods have higher oxygen demands than benthic species. Inadequate aeration causing oxygen below 5 mg/L stresses Acartia. Severe hypoxia (<3 mg/L) causes mass mortality. Continuous moderate to vigorous aeration essential.

Life Cycle and Reproduction

Egg Stage: Females broadcast spawn 10-40 eggs per clutch into water column. Eggs sink slowly while developing. Development: 15°C (3-4 days), 20°C (1.5-2.5 days), 25°C (1-2 days). Eggs measure 70-90 micrometers diameter.

Naupliar Stages: Six stages (N1-N6). Nauplii hatch at 90-130 micrometers, ideal for first-feeding larvae. Development: 15°C (8-12 days), 20°C (5-8 days), 25°C (4-6 days). Feed on fine phytoplankton (Nannochloropsis, Isochrysis). Strong positive phototaxis facilitates visual predation by larvae.

Copepodid Stages: Five stages (C1-C5). Development: 15°C (12-18 days), 20°C (8-12 days), 25°C (6-10 days). Size progression 200-900 micrometers perfectly matches larval growth from 3mm to 8-10mm.

Adult Stage: Sexual maturity: 15°C (25-35 days), 20°C (18-25 days), 25°C (14-20 days). Females produce eggs 2-5 days after maturity, releasing batches every 2-5 days. Lifespan: 15°C (2-5 months), 20°C (1.5-3 months), 25°C (1-2 months). Lifetime fecundity 200-1200 offspring per female. Populations double every 10-18 days under optimal conditions.

Nutritional Composition and Critical Value

Protein: 45-55% dry weight with complete amino acid profile matching larvae requirements.

Essential Fatty Acids - EPA and DHA:

• EPA: 15-30% of total fatty acids (Nannochloropsis, Chaetoceros, Phaeodactylum)
• DHA: 10-20% of total fatty acids (Isochrysis, Tisochrysis, Pavlova)
• Total Omega-3: 35-55% with balanced diet

Critical Importance:

• Neural Development: DHA comprises 30-40% of brain tissue. Deficiency causes reduced brain size, abnormal development
• Vision Development: DHA comprises 50-60% of retinal photoreceptors. Deficiency causes poor vision, abnormal eyes
• Skeletal Development: EPA/DHA regulate calcium metabolism. Deficiency causes jaw deformities, spinal curvatures, fin malformations
• Immune Function: EPA/DHA modulate inflammatory responses, reduce disease susceptibility

Studies document larvae fed EPA/DHA-rich copepods show 200-500% higher survival and 150-300% faster growth versus deficient foods.

Enrichment Strategy: For EPA: Nannochloropsis oculata (25-40%), Chaetoceros calcitrans (20-35%) For DHA: Tisochrysis lutea (12-18%), Pavlova lutheri (18-25% DHA plus 20-30% EPA) Balanced: Pavlova lutheri or mixed Nannochloropsis + Tisochrysis

Accumulates carotenoids providing pigmentation, vision support, antioxidants. High digestibility (85-95% absorption) maximizes feed conversion.

Commercial Marine Fish Hatchery Applications

Industry Standard: Primary live food producing Atlantic Cod, Haddock, Halibut, Turbot, European Sea Bass, Grouper, Snapper, Cobia, Pompano, Barramundi, Amberjack.

Why Hatcheries Prefer Acartia:

1. Optimal Size Progression: 90-130μm nauplii → 200-900μm copepodids → 900-1400μm adults perfectly scale with larval growth
2. Superior Nutrition: High EPA+DHA prevents deformities, supports neural/visual development
3. Natural Presentation: Planktonic behavior mimics ocean plankton, triggers instinctive responses
4. Proven Results: 3-10 fold survival improvements versus rotifer-only protocols
5. Scalable Production: Fast reproduction enables industrial-scale operations

Typical Protocol: Days 1-3: Yolk absorption Days 3-12: Enriched rotifers (100-210μm) Days 10-25: Acartia nauplii/copepodids replacing rotifers Days 20-35: Large copepodids/adults plus Artemia Days 30-45: Artemia and weaning to microdiets

Reef Aquarium Applications

Planktivorous Fish: Acartia ideal for anthias (improved coloration, reduced aggression, increased spawning), chromis, dartfish, firefish, cardinalfish, fairy wrasses, flasher wrasses. Swimming in water column provides natural prey presentation.

Marine Fish Breeding: Breeding programs report 2-4 fold improved larval survival using Acartia versus Artemia. Appropriate size, behavior, and nutrition dramatically improve success for clownfish, dottybacks, gobies, cardinalfish, blennies.

Mandarin Supplementation: While mandarins primarily hunt benthic copepods, they opportunistically consume suspended Acartia near substrate. Mixed populations (Tigriopus/Tisbe + Acartia) provide maximum diversity.

Culture Requirements and Methods

Culture Setup: Small-scale (20-200L): Food-grade cylindrical/conical containers, air stones at bottom, indirect lighting (12-16 hour photoperiod), temperature control via heaters Medium-scale (200-1000L): Multiple tanks for staggered production, central aeration, filtered seawater, climate-controlled room Large-scale (1000-10,000+L): Automated feeding/water exchange, egg collection systems, separate tanks for life stages

Design Principles: Minimum 50cm water depth (1-2m ideal), gentle aeration for oxygen without excessive turbulence, dark/conical bottoms facilitate egg collection, surface overflow with fine mesh preventing escape.

Feeding: Optimal species: Nannochloropsis oculata (2-4μm) for all stages, Isochrysis galbana (4-6μm) for copepodids/adults, Tisochrysis lutea (4-6μm) highest DHA, Rhodomonas salina (6-10μm) exceptional protein, Tetraselmis chui (10-14μm) for large copepodids/adults.

Mixed diet: 60-70% Nannochloropsis, 20-30% Isochrysis/Tisochrysis, 10-20% Rhodomonas. Maintain light green tint (200,000-800,000 cells/ml). Feed daily maintaining consistent concentration.

Water Management: Batch: 30-50% changes 2-3 times weekly, siphon bottom collecting eggs, replace with filtered seawater matching temperature/salinity Semi-continuous: 10-30% daily exchange via surface overflow with 80-100μm mesh Monitor: Temperature daily (±1°C), salinity weekly (±2 ppt), pH 2-3x weekly (7.8-8.4), DO daily in dense cultures (>6 mg/L), ammonia/nitrite weekly (0 ppm), nitrate weekly (<20 mg/L)

Egg Collection (Broadcast Spawners): Daily/twice-daily siphon bottom water through 50-80μm mesh. Eggs retained, adults wash through. Transfer eggs to separate hatching tanks with fresh water and phytoplankton. Prevents cannibalism, optimizes conditions for each life stage.

Harvesting: Net (200-300μm gently sweeping), siphon (large tubing through mesh), or overflow (increase flow to surface collector). Harvest 10-25% weekly sustainable, 30-50% possible with excellent management.

Production Yields: Low (50-200/L), Medium (200-800/L), High (800-2000/L). Commercial hatcheries target 500-1000/L, achieving 100-200/L daily harvest.

Advantages and Considerations

Advantages: Industry-proven track record, optimal larval fish nutrition (high EPA+DHA), perfect size progression, natural prey presentation, temperature versatility (cold temperate to warm tropical), scalable production, extensive scientific literature.

Considerations: Higher maintenance than hardy Tigriopus, egg separation beneficial for broadcast spawners, equipment dependency (continuous aeration essential), lower visibility than orange Tigriopus, specialized for larviculture and planktivores.