Aquaculture Study Guide

📖 Core Concepts Aquaculture – Controlled cultivation of aquatic organisms (fish, crustaceans, mollusks, algae, plants) for food, feed, or other products. Water‑type categories – Freshwater (rivers, lakes, ponds), Brackish (mix of fresh & sea water), Saltwater/Marine (sea cages, offshore). Production environments – On‑shore (tanks, ponds, raceways, aquaponics), In‑shore (sheltered shallow coastal waters), Off‑shore (open‑water cages, racks, bags). Mariculture – Aquaculture performed in seawater habitats; a subset of aquaculture. Pisciculture – Fish‑focused aquaculture for food production. Integrated Multi‑Trophic Aquaculture (IMTA) – Combines fed species (e.g., salmon) with extractive species (e.g., shellfish, seaweed) that use the waste nutrients. Recirculating Aquaculture System (RAS) – Land‑based, high‑density tanks that filter and reuse > 95 % of water. Fish‑in‑Fish‑out (FIFO) ratio – Kilograms of wild forage fish required to produce 1 kg of farmed carnivorous fish (e.g., salmon FIFO ≈ 4.9 : 1 in 2006). Animal welfare basics – Fish have nociceptors; high stocking density, low water flow, and handling increase stress and disease risk. --- 📌 Must Remember Global share – Aquaculture supplied  47 % of total fish production in 2016;  53 % when non‑food uses are excluded. Growth rate – Avg. 5.8 % annual increase (2001‑2016), fastest among major food sectors. Top farmed fish (by importance) – Carp > Salmon > Tilapia > Catfish. FIFO trend for salmon – 7.5 : 1 (1995) → 4.9 : 1 (2006). Feed composition shift – Plant proteins now ≈ 40 % of salmon feed; fish‑meal/oil < 30 % of total feed ingredients. Economic value – US $86 billion (2009) → US $312.8 billion (2022). Environmental services – Shellfish filter water; seaweed removes N & P and can sequester 2–3 t CO₂ ha⁻¹ yr⁻¹. Vaccines – DNA vaccines are EU‑approved, cut production costs, and reduce mortality > 70 % for some diseases. AquAdvantage salmon – Growth‑hormone transgene shortens market‑size time to 16–28 months (vs.  36 months). --- 🔄 Key Processes IMTA workflow Stock fed species → collect waste (uneaten feed, excreted N/P). Route waste‑rich water to extractive species (shellfish, seaweed). Extractive species assimilate nutrients → harvest → market product. Recirculating Aquaculture System (RAS) cycle Tank → fish waste → biofilter (nitrification) → settling tanks (solid removal) → UV/ozone (pathogen control) → return to tank. Biofloc formation Adjust C:N ratio → promote heterotrophic bacteria → bacteria aggregate into “flocs” → flocs clean water and serve as supplemental protein for fish. Sea‑ranching Hatchery → short‑term rearing → release into open ocean → natural growth → recapture at maturity. Vaccine administration Immersion → injectable water‑based → oil‑based → DNA vaccine (injectable, antigen‑encoding plasmid). --- 🔍 Key Comparisons Mariculture vs. Freshwater Aquaculture Mariculture: seawater, cages/racks, species like salmon, seaweed. Freshwater: rivers/lakes/ponds, species like carp, tilapia. On‑shore vs. Offshore systems On‑shore: land‑based tanks, high control, high capital, low environmental exposure. Offshore: open‑water cages, natural currents, lower land use, higher exposure to storms & escapes. IMTA vs. Monoculture IMTA: waste recycling, lower disease pressure, added products (shellfish/seaweed). Monoculture: higher disease risk, no nutrient reuse, often higher profitability per species. DNA vaccine vs. Traditional injectable vaccine DNA: no adjuvant needed, lower production cost, long‑lasting immunity. Traditional: oil‑based or water‑based, higher cost, may require boosters. --- ⚠️ Common Misunderstandings “Aquaculture always harms the environment.” – Not true; filter‑feeding bivalves and seaweed can improve water quality and sequester carbon. “Higher stocking density = more production.” – Excess density raises stress, reduces oxygen, increases disease, ultimately lowering growth and survival. “All fish feeds rely heavily on wild fish.” – Plant and insect proteins now supply  60 % of feed protein; FIFO ratios are dropping. “Genetically modified salmon are unsafe.” – AquAdvantage salmon has only a growth‑hormone transgene; FDA approved after safety assessment. --- 🧠 Mental Models / Intuition “Waste → Resource” loop – Imagine a kitchen sink: food scraps (fish waste) flow into a compost bin (shellfish/seaweed) that turns waste into a new dish (harvestable product). FIFO as “fuel efficiency” – Lower FIFO = better “miles per kg of wild fish” for farmed fish, analogous to a car using less fuel per mile. --- 🚩 Exceptions & Edge Cases Escaped fish – Even low‑density offshore cages can cause genetic introgression if escaped fish interbreed with wild stocks. Heavy‑metal accumulation – Copper & zinc build‑up under salmon cages; mitigation depends on feed formulation and cage cleaning frequency. Disease in monocultures – High‑density shrimp farms are especially prone to rapid disease spread; biosecurity measures may be insufficient without species diversification. --- 📍 When to Use Which Choose IMTA when you have a fed species that produces high N/P waste and a market for extractive species. Select RAS for inland/urban production, high biosecurity needs, or when water scarcity makes reuse essential. Deploy Biofloc in warm, high‑density systems where supplemental protein is needed and water exchange is limited. Apply DNA vaccines for high‑value, high‑mortality diseases where cost‑effective, long‑lasting immunity is desired. Opt for offshore cages for large, fast‑growing marine species (e.g., salmon) when land is limited and deep water is accessible. --- 👀 Patterns to Recognize Nutrient‑rich waste → algae growth → oxygen spikes – In IMTA, sudden algal blooms near cages often signal excess feed. Elevated ammonia + low flow → hypoxia signs (fish lethargy, surface gulping). Uniform mortality spikes after handling – Likely stress‑induced disease outbreak; look for recent vaccination or grading events. Heavy metal sediments beneath cages – Consistent with long‑term salmon cage operations. --- 🗂️ Exam Traps “All aquaculture uses fishmeal.” – Wrong: many modern feeds are plant‑based or insect‑based; FIFO is decreasing. “Seaweed farms only produce food.” – Misses carbon sequestration, nitrogen removal, and habitat creation. “Recirculating systems are only for freshwater species.” – RAS can support marine species (e.g., salmon) with appropriate filtration. “Higher FIFO ratio means higher profitability.” – Higher FIFO raises feed cost and environmental impact, reducing profitability. “IMTA always yields higher total profit than monoculture.” – Profit depends on market prices for extractive species; sometimes monoculture of a high‑value fish is more lucrative. ---