AFM 210: Introduction to Aquatic Resources Management Flashcards

Principles of Fisheries Management in Inland and Marine Environments

  • Definition of Fisheries Management: It is the rational exploitation and conservation of aquatic resources in such a way that these resources are maintained on a sustainable yield basis.

  • Main Goal: The production of sustainable biological, social, and economic benefits from renewable aquatic resources.

  • Renewability of Fisheries: Fisheries are classified as renewable because aquatic resources of interest (fish, shellfish, reptiles, amphibians, and marine mammals) usually produce an annual biological surplus. This surplus is harvestable without reducing future productivity under judicious management.

  • Diverse Benefits to Humanity:

    • Commodity Output: The weight or number of fish produced. This is subdivided into production from fish capture in the wild and production from captive animals.

    • Economic Benefits: Measured as wholesale or retail economic value.

      • In commercial fisheries, products are sold to calculate value.

      • In sport or recreational fisheries, benefits are indirect; the quality of the fishing experience is the primary measure, making catch weight or number only partial measures of value provided to society.

    • Social Benefits: Includes existence value—the benefit derived from simply knowing a resource exists. Society receives intangible benefits from preserving species and habitats, particularly those facing extinction.

    • Ecological Benefits: Increasingly guided by ecological mandates in treaties and laws. For example, the Convention on Biological Diversity obligates nations to preserve biological diversity. Laws protecting species at risk act as constraints on the scope and intensity of fishing.

  • National Policy Goals: To ensure the attainment and continued satisfaction of human needs for present and future generations in an environmentally non-degrading, technically appropriate, economically viable, and socially acceptable manner, maintaining land, water, plant, animal, and genetic resources.

Broad Definitions and Classifications in Fisheries

  • The Fish: Includes every aquatic organism that is or could be harvested. Examples include:

    • Fin fish: Fish that have fins (e.g., mackerel, tilapia, tuna, guppies).

    • Shellfish: Clams, crabs, lobsters.

    • Others: Sea turtles, seals, whales, sea urchins, squid, and frogs.

  • The Fishery: A system comprising three interacting components:

    • The Aquatic Biota.

    • The Aquatic Habitat.

    • The Human Users.

  • Classification of Fisheries:

    • Environment: Freshwater (lakes, reservoirs, rivers, streams, ponds) vs. Saltwater (estuarine, coastal, open ocean).

    • Method of Harvest: Seining, trolling, trawling, fly casting, spearing, and dip netting.

    • Access: Open access, open access with regulation, limited/purchased access, and private property.

    • Organism: Salmon, shrimp, bass, turtles, squid, cod, sharks, sea horses, whales, swordfish.

    • Purpose: Commercial (selling products), Subsistence (direct food), and Recreational (sport and leisure).

    • Degree of Wildness: Totally wild, totally captive (ponds), or spawned in captivity but released into the wild.

Global Fisheries Trends and Resources

  • Historical Perspective: Fish utilization dates back to 90,000 BP90,000\,BP (years before the present).

  • Development: Improvements in boat design, preservation (drying, smoking, salting), and transportation led to the advent of commercial fishing in the middle ages.

  • Economic Contribution:

    • Over 36 million36\text{ million} people are employed in capture and culture fisheries.

    • Over 4,0004,000 species of aquatic animals are harvested globally.

    • Total global production is over 120 million metric tons120\text{ million metric tons} annually.

    • Annual per capita fish consumption is approximately 15 kg15\,kg globally.

    • Regional Consumption: Africa has the lowest per capita consumption; Europe and Asia have the highest.

Freshwater (Inland) Environments and Resources

  • African Inland Fisheries: Contained within 2525 large river basins and smaller coastal ones.

  • Classification of Water Bodies (FAO 1994):

    • Floodplains: Large flatlands where seasonal high tides cause large-scale flooding (e.g., Niger, Benue, Chari, Logone, Senegal).

      • Production depends on flood extent and duration.

      • Total production: 500,000 t/year500,000\,t/year (approximately 30-35%30\text{-}35\% of Africa’s inland total).

      • Productivity: Average 40 kg/y/ha40\,kg/y/ha of flooded area.

    • Watercourses without Floodplains: Well-defined channels with small production areas (e.g., Lower Congo, middle reaches of Black Volta, Bandama). Best fishing occurs during the low-water season.

    • Lagoons: Transitional environments between fresh and sea water. Typical species include Tilapia, Heterotis, Clarias, and euryhaline species like Mullet.

      • Shrimps are significant euryhaline resources in lagoons, reproducing at sea and migrating following a known cycle.

    • Shallow Lakes: Less than 30 m30\,m deep (e.g., Lake Chad, 5,000−10,000 km25,000 - 10,000\,km^2).

      • Fisheries are typically artisanal.

      • Natural productivity: Range from 15 kg/ha15\,kg/ha (poor lakes) to 100 kg/ha100\,kg/ha (volcanic regions). Average: 50 kg/ha/y50\,kg/ha/y.

    • Man-made Reservoirs: Created for energy or irrigation (e.g., Kainji, Volta, Kariba, Nasser).

      • Large reservoirs are over 1,000 km21,000\,km^2.

      • Productivity: Approximately 50 kg/ha/y50\,kg/ha/y.

      • Introduction of species: Often done to fill niches (e.g., Oreochromis niloticus in Lake Kossou; Sardinella in Lake Kariba).

    • Deep Lakes: Primarily in the Rift Valley (Victoria, Tanganyika, Malawi/Nyasa, Kivu).

      • Biotic Zone: Rich in plankton and fish; surface down to 70 m70\,m (Kivu) or 200 m200\,m (Tanganyika).

      • Abiotic Zone: Deep waters often without oxygen or fish.

      • Estimated production: Far exceeds 250,000 t/year250,000\,t/year.

Marine Environments and Resources

  • Coastal Zone:

    • Intertidal (Littoral) Zone: Transition between marine and terrestrial; shore between high and low tide.

    • Estuaries: Transition where fresh and salt water mix; critical breeding/feeding grounds.

  • Exclusive Economic Zone (EEZ): Established as a standard 200 nautical miles200\,nautical\,miles from base lines following the Third UN Conference on the Law of the Sea. Individual nations have sovereign rights over these resources.

  • Continental Area: Supports shelf communities. Waters above are termed neritic.

    • Neritic waters are rich in nutrients due to turbulence, wave action, upwelling, and river runoff.

  • Coral Reefs: Tropical ecosystems with high biomass. Types include:

    • Fringing reefs (directly from shore).

    • Barrier reefs (separated by a lagoon).

    • Atolls (summits of submerged volcanoes).

  • Mangroves: Tropical swampy forests with salt-tolerant halophytes. Specializations include:

    • Pneumatophores: Tube-like breathing roots growing vertically.

    • Viviparous seedlings: Germinate while still on the parent tree.

    • Functions: Prevention of erosion, nursery for aquatic organisms, and litter production (organic food factory).

  • Wetlands: Transitional ecotones between land and water. Types based on vegetation and water source:

    • Marshes: Characterized by emergent aquatic macrophytes.

    • Swamps: Dominated by trees.

    • Bogs: Acidic, low species diversity, abundance of Sphagnum moss.

    • Ferns: More alkaline, contain mosses and macrophytes.

    • Productivity Ranking: Marshes > Swamps > Ferns > Bogs.

  • African Marine Metrics: 30,490 km30,490\,km coastline. Marine capture (mostly on the western coast) contributes more than 50%50\% of total African landings.

Nigeria’s Aquatic and Fisheries Resources

  • Hydrological Profile: Nigeria has four major drainage systems:

    1. Niger River Basin Drainage System: Tributaries include Benue, Sokoto-Rima, Kaduna, Gongola, Katsina-Ala, Donga, Tarabe, Hawal, and Anambara.

    2. Lake Chad Inland Drainage System: Comprises Kano, Hadejia, Jama’are, Misau, Komadougou-Yobe, Yedoseram, and Ebeji.

    3. Atlantic Drainage System (East of Niger): Cross, Imo, Qua Iboe, and Kwa Rivers.

    4. Atlantic Drainage System (West of Niger): Ogun, Oshun, Owena, and Benin Rivers.

  • Hydrological Areas (HA):

    • HA-1: Lake Chad area (178,500 km2178,500\,km^2).

    • HA-2: Niger Central (154,600 km2154,600\,km^2).

    • HA-3: Niger North (135,100 km2135,100\,km^2).

    • HA-4: Niger South (53,900 km253,900\,km^2).

    • HA-5: Upper Benue (156,500 km2156,500\,km^2).

    • HA-6: Lower Benue (74,500 km274,500\,km^2).

    • HA-7: Eastern Littoral (57,400 km257,400\,km^2).

    • HA-8: Western Littoral (99,300 km299,300\,km^2).

  • Land and Water Metrics:

    • Inland freshwaters: 500,000500,000 to 885,000 ha885,000\,ha.

    • Major rivers cover approximately 10,812,400 ha10,812,400\,ha (11.5%11.5\% of Nigeria's surface).

    • Wetlands represent 2.6%2.6\% of the country's land area. The Niger Delta is the largest wetland in Africa and 3rd largest in the world.

    • EEZ: 216,325 km2216,325\,km^2; coastline length of 853 km853\,km.

  • Fishery Biodiversity and Production:

    • Marine: 104104 marine fish species from 5050 families. Dominant species include Croakers (Pseudotolithus spp.), Grunts (Brachydeuterus spp.), Soles, Catfish (Arius spp.), and Shrimps (Penaeus spp.).

    • Inland: Over 268268 fish species. Dominant genera include Lates, Tilapia, Citharinus, Chrysichthys, Mormyrus, and Clarias.

    • Marine production value: Past decade average exceeds 300,000 metric tonnes300,000\text{ metric tonnes} valued at over 750 million USD750\text{ million USD}.

    • Inland production: 339,499 tonnes339,499\text{ tonnes} (20132013) to 420,078 tonnes420,078\text{ tonnes} (20172017).

Aquaculture Systems and Technologies

  • Global Context: Aquaculture contributes over 46%46\% of total fish production (up from 16%16\% about 1515 years ago). In Sub-Saharan Africa, it accounts for only 3%3\%.

  • Nigeria’s Potential: Potential production of over 3 million metric tonnes3\text{ million metric tonnes}. Current output is 296,191 tonnes296,191\text{ tonnes} valued at 845.91 million USD845.91\text{ million USD}.

  • Types of Systems:

    • Mariculture: Seawater-based. Organisms include molluscs, prawns, and seaweeds (used for cosmetics/collagen and pearls).

    • Inland Fish Farming: Artificial ponds (typically 20 acres20\,acres, 6-8 ft6\text{-}8\,ft deep). Over 95%95\% of Nigerian farmed fish is in tanks or ponds.

    • Algaculture: Cultivation of algae for photosynthesized product and energy (e.g., Exxon Mobil research).

    • Integrated Multi-Trophic Aquaculture (IMTA): Mixes trophic levels to emulate natural ecosystems; waste from large organisms serves as food for smaller ones.

    • Recirculating Systems (RAS): Closed chambers with constant pumping and filtration. High power dependency but environmentally friendly with minimal water introduction.

    • Open-net pens/Cages: Offshore or in lakes. Risk of disease/parasite exchange with the environment and predator entanglement.

    • Flow-through/Raceways: Long units with flowing water. Common for trout.

    • Biofloc Technology: Wastewater treatment approach maintaining a higher C-N ratio by adding carbohydrates.

      • Heterotrophic microbes assimilate nitrogenous waste into single-cell protein.

      • Floc size: 50−200 microns50 - 200\,microns.

      • Nutritional value: 25-50%25\text{-}50\% dry weight protein; 0.5-15%0.5\text{-}15\% fat.

      • Advantages: Eco-friendly, judicial land/water use, biosecurity.

      • Disadvantages: High energy requirement for aeration, need for alkalinity supplementation.

  • Intensity-Based Classification:

    • Extensive: Ponds 1-5 ha1\text{-}5\,ha, stocking density < 5,000 fishes/ha5,000\,fishes/ha. No supplement feed. Yield: 500 kg500\,kg to 2 ton/ha2\,ton/ha.

    • Semi-intensive: Ponds 0.5-1 ha0.5\text{-}1\,ha, density 10,000-15,000 fish/ha10,000\text{-}15,000\,fish/ha. Fertilization and supplemental feeding used. Yield: 3-10 ton/ha3\text{-}10\,ton/ha.

    • Intensive: Tanks/raceways, density 10-50 fish/m310\text{-}50\,fish/m^3. Wholly formulated feed. Yield: 15-100 ton/ha15\text{-}100\,ton/ha.

Integrated Aquaculture Systems

  • Agriculture-Fish Integration:

    • Rice-Fish: Uses paddy fields and strong-rooted rice varieties. Species: African catfish, Common carp, Tilapia.

    • Horticulture-Fish: Dykes planted with coconut, mango, banana, or vegetables. Residues recycled into ponds.

    • Mushroom-Fish: Utilizes the high humidity of fish farming.

    • Seri-Fish: Silkworm feces directly fertilize the pond.

  • Livestock-Fish Integration:

    • Pig-Fish: 60-10060\text{-}100 pigs per hectare. 5 tons5\,tons of manure per year required. Ratios like 1:21:2 (Tilapia to Catfish).

    • Poultry-Fish: 25,00025,000 chicks per hectare. One chicken produces 25 kg25\,kg manure annually.

    • Duck-Fish: Ducks consume juvenile frogs/pests. 100-3,000100\text{-}3,000 ducks per hectare.

    • Cattle-Fish: Healthy cows excrete 4,000-5,000 kg4,000\text{-}5,000\,kg dung and 3,500-4,000 liters3,500\text{-}4,000\,liters urine annually. 5-65\text{-}6 cows per hectare provide adequate manure.

Biological and Operational Principles of Fish Culture

  • Primary Productivity: Fish rely on plants directly or indirectly. Natural fertility depends on soil in the pond bottom and watershed.

  • Limiting Factors:

    • Minerals and Nitrogen: Supplemented via fertilizers.

    • Carbon Dioxide (CO2CO_2): Limited after minerals/nitrogen are met; increased by organic matter and liming.

    • Oxygen (O2O_2): Most critical limiting factor at high intensities.

  • Oxygen Thresholds:

    • Lethal limit: < 1.0 ppm1.0\,ppm.

    • Resting state requirement: 1.0 ppm1.0\,ppm.

    • Active state requirement: 3.0 ppm3.0\,ppm.

  • Plankton Qualities: Microscopic plants (planktonic algae) are highly desirable due to short life cycles, mobility, and small size. Rooted plants are less desirable in intensive systems because they shade the water and are immobile.

  • Food Chain Conversion Rates:

    • Plant to fish: 5:15:1 to 10:110:1

    • Plant to insect: 5:15:1 to 10:110:1

    • Insect to fish: 3:13:1 to 10:110:1

    • Fish to fish: 2:12:1 to 5:15:1

  • Biological Control Methods: Repression (preventing reproduction), Predation (controlling young fish), and Starvation/Limited spawning area.

  • Economic Feeding: Maintenance food requirement per year is roughly equal to the feed required to raise the fish to that weight initially. Feeding to maintenance or satiety for extended periods is uneconomical.

Sustainable Catch Exploitation vs. Destructive Methods

  • Current Status: 90%90\% of global fish populations are fished at the maximum limit or overfished. World stocks: 29%29\% overfished, 61%61\% fully fished, 10%10\% underfished.

  • Destructive Methods:

    • Blast Fishing: Use of dynamite kills indiscriminately and destroys coral reefs.

    • Bottom Trawling: Tows huge nets (300 ft300\,ft wide) across the seafloor, destroying established ecosystems. Yields up to 16 kg16\,kg of bycatch per 1 kg1\,kg of target fish.

    • Cyanide Fishing: Sprays poison to stun fish (mostly for aquariums). 75%75\% of fish die within 48 hours48\,hours of capture.

    • Muro-ami: Pounding reefs with heavy blocks to scare fish into nets.

    • Ghost Fishing: Abandoned nets continuing to entangle and kill marine life.

  • Sustainable Methods:

    • Hook-and-Line: Limits volume but reduces bycatch significantly.

    • Spear Fishing/Harpooning: Targets individual large fish like swordfish; zero bycatch.

    • Traps and Pots: Stationary cages designed with escape holes for juveniles.

    • Purse Seining: Drawing a net around shoals like a drawstring purse; effective with single-species shoals.

  • Mitigation and Regulation:

    • Bycatch Discard: Estimated at 10.8%10.8\% global catch (9.1 million tonnes9.1\text{ million tonnes}) annually.

    • IUU Fishing: Estimated at 11%11\% to 33%33\% of annual global catch (11-26 million tonnes11\text{-}26\text{ million tonnes}).

    • Technological Solutions: Excluding devices (BRDs), non-tangling biodegradable materials, and acoustic deterrents.

    • Certification: The Blue MSC label (Marine Stewardship Council) identifies sustainable sources for consumers.

    • Removal of Subsidies: Eliminating government funding that makes overfishing beyond sustainable levels financially viable for deep-sea fleets.