Fisheries & Aquaculture Biology

How are fisheries doing right now?

Near universal consensus that they’re unsustainable - more depleted stocks & more catches in low trophic levels

Negative Stigmas around Aquaculture

1. “Net consumer of fish”

2. Destruction of habitat

3. Creator of poverty, not an alleviator (doesn’t provide well-paying jobs)

Broad Categories of Aquaculture

1. Sea cages (like Norwegian salmon farms)

2. Coastal ponds (like prawn aquaculture)

3. Land-based systems

What drives perceptions of underperformance in aquaculture? (5)

1. Over-inflation of aquaculture production (especially in China)

2. Sustainability issues with vulnerability to disease, pollution feedback loops, & typical “slash & burn” operations

3. Developed countries often use more fish flesh than they produce (to feed predatory fishes)

4. Poor hatchery performance in developing economies - consumes unsustainable quantities of wild larvae

5. Depends on sources of Marine Fish Oil from capture fishery (scope not certain)

Aquaculture Definition

Aquatic production achieved through the physical control in the life cycle other than at the point of harvest

3 historic roles of aquaculture

1. Produce cheap protein to contribute to total world food

2. Seed to supplement conventional fisheries & prevent decline

3. Meet a specific market demand producing a product at a cost less than the market price, thus providing economically viable industry

Aquaculture vs. Fisheries Operations

1. Management of fisheries is entirely via catch regulation (quotas, gear, & vessels)

2. Most aquaculture involves land ownership, most animals are secondary consumers of animal protein, most are genetically similar to wild type, many more species than in terrestrial agriculture

Economic Value of Aquaculture

1. Value shot up from $35B (1995) to $390B (2024)

2. Equal volume of fishing before 2010, 60% of animal biomass eaten by humans comes from aquaculture

Changes in Global Profiles of Aquaculture

Strong increases in Africa & Asia, kind of unstable in South America, not growing in North America, Europe, & Oceania

Which groups are best represented in aquaculture?

Freshwater & (less so) diadromous fishes, crustaceans, & molluscs, not very good for marine fishes yet

Is aquaculture growing at a satisfactory rate to meet demand?

It can close the gap in a way that fisheries can’t, but it also cannot fully meet the demands

Accidental Instances of Aquaculture

1. Monks in Europe

2. Farmers in Asia

3. Fishers of closed & flooded valleys or fjords in Europe

4. Ponds & river overflows in Africa

Fully Intensive Aquaculture

Has all 3 of the major aspects of aquacutlure

1. Seed (larval) production by farmer or specialized hatchery

2. Provision of holding facility for at least some stages in life cycle

3. Provision of food by the farmer

(Babies, Water, & Snacks)

Production Advantages of Fully Intensive Aquaculture

1. Genetic manipulation & strain selection

2. Simplification of food chain (ideal food to meet requirements)

3. Removal of predators & competitors

4. Control of growth conditions to maximize growth rate, yield per unit effort, and/or profit

5. Independence from natural breeding cycles

Successful aquaculture will always outcompete fisheries

Economic Disadvantages of Aquaculture

1. High capital costs & overheads

2. Disruption of socio-economic structures

3. High level of inherent instability

4. Development of profit centers that consume ecological & protein resources

Economic Advantages of Aquaculture

1. Economic growth & job creation

2. Output of high value goods to world markets, providing hard currency

3. Revenue for purchase of low value foods in greater quantity

Limits on Fisheries Production

1. Rate of primary production

2. Trophic level of stock & efficiency of energy transfer between trophic levels

3. Abundance of non-fished competitors & predators

4. Relationships: mortality-growth, age-size

Yield = excess of production over other losses

Limits on Aquaculture

1. Production of Juveniles (modification of time of breeding, nutrition of brood stocks, & larval rearing systems)

2. Food supply & growth (finite supply of fishery products, potential to optiomize growth rate via temp, photoperiod, & stocking density)

3. Disease control (prevention via design, treatment & immunization)

How to remove aquaculture constraints

1. Manipulate breeding season & hatcheries for larvae

2. Development of fishery-independent foods

3. Immunizations & treatments

Methods of Aquaculture Classification

1. Culture system/structure

2. Level of intensity

3. Water exchange system

Examples of Culture Systems

1. Ponds - shrimp & tilapia

2. Raceways - trout

3. Tanks - halibut

4. Cages - salmon, seabass, & seabream

5. Pens - sea cucumber

6. Racks - oysters

7. Long-lines - shellfish & seaweeds

8. RAS - research aquaculture systems

Pond Aquaculture Pros (4) & Cons (3)

PROS

1. Cheap to construct

2. Low energy cost

3. Low water exchange

4. Low tech (good for developing nations)

CONS

1. Often extensive site & land requirements

2. Coastal land resource competition & impacts on systems

3. Very open (biologically)

Pond System Setups

Most basic farming enclosure - earth structure with some form of drainage, often rectangular w/ gravity- or tidal-fed inflow & outflow, can be any salinity depending on location, require impermeable soil (clay of an appropriate pH & organic content) or a liner, suitable water supply & drainage

Series vs. Parallel Pond Layouts

Series has water quality gradients, no disease barrier, easier animal transfer, & lower water usage

Pond Design Basics (8)

1. Inlet & outlet must be basic & operable

2. Inlet controls all water exchange

3. Outlet controls water level & collection

4. Wall slope may vary w/ soil type & height

5. Depth 1-2 m, shallow for light

6. 0.25 - 0.5 m free wall

7. Ponds can be very large, impracticalities arise

8. Rectangular causes circulation problems

Pros (5) & Cons (4) of Aquaculture Tanks

PROS

1. Allows use of more sites

2. More controlled environment (cleaner & less biotic, current)

3. Sustainable for larval stages

4. Suitable for high value ongrowing

5. Raceways suitable for high-flow organisms like salmon

CONS

1. Often higher capital costs

2. Higher water requirements (source & pumping requirements as well)

3. Energy & building requirements

4. Shape & design requirements

Types of Aquaculture Tanks

Concrete, fiberglass, or even wood, shape matters (dead water, waste accumulation, no flow, circular w/ conical base best for this), rectangular/raceway for unidirectional or looped flow

Raceways

Water flows almost like a concrete river, a tank with a heavy flow (like that girl in Mean Girls)

Tank & Raceway Considerations (8)

1. Materials

2. Shape & Size

3. Hydrodynamics

4. Aeration

5. Waste removal

6. Cleaning

7. Space

8. COST

Pros (2) & Cons (5) of Cages

PROS

1. Intermediate cost, cheap to run (ecosystem services free)

2. Allows intensive farming

CONS

1. Initial capital is expensive

2. Site requirements (limited sheltered coasts)

3. Transport & logistics

4. Coastal land resource competition & systems impact

5. Openness (biologically & socially)

6. Cage maintenance (fouling, damage & repairs, SCUBA access, removal of mortalities, net exchanges)

Modern Sea Cage Components (8)

1. Ring Float

2. Nylon Net

3. Moorings

4. Collar (base ring to maintain structure)

5. Hamster-wheel float

6. Bird netting, jump netting, & predator net

7. Automated feeding system

8. Video monitoring in-cage & above cage

Sea Pen Components

Sticks & ropes

Rack Components

Something solid for a fouling organism to attach to (usually oysters)

Longlines

Backbone buoyed - extended between 2 moorings w/ hanging cultures (usually for mussels, scallops, & macroalgae)

Cons of Longlines

1. Space competition

2. Openness (biological & social)

3. Maintenance - fouling, replacement, buoys

4. Equipmrent requirements (cranes, etc.)

5. Only suitable for extractive species

6. Easily damaged