IKENWEIWE Bolatito Nafisat (PhD) DEPARTMENT OF AQUACULTURE AND FISHERIES MANAGEMENT UNIVERSITY OF AGRICULTURE, ABEOKUTA PRODUCTION IN INLAND AND MARINE WATERS

Production in inland and Marine Waters FIS 702 (2 Units) Elective

Course outline Types of aquatic ecosystem, Limiting factors controlling fish production. Allochthonous and autochthonous migration and Resource distribution

INTRODUCTION The current overall fish production is estimated at metric tones, whereas the requirement or demand for fish production is about 5 million metric tones (Dada 2004). This clearly shows that there exist a wide gap between fish production and demand for fish products. Fish production can only be increased when the spatially variable production factors controlling aquaculture and inland fisheries are well understood and properly addressed.

CONCEPT OF ECOSYSTEM An ecosystem is defined as “a spatially explicit unit of earth that includes all of the organisms, along with all the components of the abiotic environment within its boundaries” (Likens, 1992). An Ecosystem is a combination of two words "Ecological" and " system“.

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving, physical components of the environment with which the organisms interact, such as air, soil, water and sunlight

Types of ecosystem There are two broad classification of ecosystem: – Natural and – Artificial

A. Natural ecosystem It is classified into two parts 1) Terrestrial ecosystem Few examples are: * Forest Ecosystem * Sahara Desert Ecosystem * A Grassland Ecosystem * A Semi-forest Ecosystem * An ecosystem on a snow field * A Scrubland ecosystem * A Cold desert ecosystem * Wetland ecosystem * Wild Life Sanctuaries, National Parks, Animal Reserves 2) Aquatic ecosystem (to be discuss later)

B. Artificial ecosystem Artificial ecosystems are created by humans. Examples include – animal reserve or a giant terrarium e.g. zoo – Gardens are also artificial ecosystem – Crop lands like maize, sugarcane, rice-fields, wheat, orchards, – dams, aquarium, cities, and manned spaceship.

The basic biotic and abiotic components are defined by man in artificial ecosystem.

TYPES OF AQUATIC ECOSYSTEM Aquatic ecosystem is divided into two parts- Marine ecosystem and freshwater ecosystem.

Marine Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production.

Marine ecosystems can be divided into the following zones: – oceanic (the open part of the ocean where animals such as whales, sharks, and tuna live); – profundal (bottom or deep water); – benthic (bottom substrates); – intertidal (the area between high and low tides); – estuaries; – salt marshes; – coral reefs; and – hydrothermal vents (where chemosyntheticsulfur bacteria form the food base).

Classes of organisms found in marine ecosystems include – brown algae, – dinoflagellates, – corals, – cephalopods, – echinoderms, and – sharks. Fish caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.

Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas.

Freshwater Freshwater ecosystems cover 0.80% of the Earth's surface and inhabit 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish species.

There are three basic types of freshwater ecosystems: Lentic: slow-moving water, including pools, ponds, and lakes. Lotic: rapidly-moving water, for example streams and rivers. Wetlands: areas where the soil is saturated or inundated for at least part of the time

Lake ecosystems Lake ecosystems can be divided into zones: – pelagic (open offshore waters); – profundal; – littoral (nearshore shallow waters); and – riparian (the area of land bordering a body of water). Two important subclasses of lakes are ponds, which typically are small lakes and water reservoirs.

Abiotic characteristics temperaturesalinity Abiotic environmental factors of aquatic ecosystems include temperature, salinity, and flow. dissolved oxygen The amount of dissolved oxygen in a water body is frequently the key substance in determining the extent and kinds of organic life in the water body. Fish need dissolved oxygen to survive. Conversely, oxygen is fatal to many kinds of anaerobic bacteria.

Biotic characteristics The organisms (also called biota) found in aquatic ecosystems are either autotrophic or heterotrophic. Autotrophic organisms – Autotrophic organisms are producers that generate organic compounds from inorganic material. – Algae use solar energy to generate biomass from carbon dioxide and are the most important autotrophic organisms in aquatic environments. – Chemosynthetic bacteria are found in benthic marine ecosystems. These organisms are able to feed on hydrogen sulfide in water that comes from volcanic vents.

Heterotrophic organisms – Heterotrophic organisms consume autotrophic organisms and use the organic compounds in their bodies as energy sources and as raw materials to create their own biomass. – Euryhaline organisms are salt tolerant and can survive in marine ecosystems, while – stenohaline or salt intolerant species can only live in freshwater environments.

– lake – ocean – creek – lagoon – bog – sea – glacier – tidal pool – geyser – fen – flood plain – bog – estuary – aquifer – salt lake Other forms of Aquatic ecosystem

Marsh - shallow water with non-woody plants growing above water level Swamp - like a marsh but with bushes and trees growing from the water as well Pond - a small and shallow body of water with plants growing above water level only on the edges; River - a moving body of water that flows from one place to another. Stream - smaller than a river, Puddles - body of water that lasts for a few days Spring - area where underground water is discharged onto the land surface forming a pond or stream

LIMITING FACTORS CONTROLLING FISH PRODUCTION

Fish production is dependent on a number of factors: these factors have been termed production factors because fish yield/output is' a function of various combinations of parameters or factors. The factors fall under environmental, physical, economic, and social factors and all these will show spatial variability within and between given areas or zones.

Attempt is made here to identify some production functions controlling aquaculture and inland fisheries based on FAO 1991 are: – Land availability – Capital ownership – Topography – Climate – Season and area – Water availability – Water quality – Potential for competitive water use

Soil properties Predators Adjacent land uses Proximity to supporting infrastructure Access roads Local political, social & economic factors Environmental constraints Security Availability of skilled manpower Exploitation method Pollution Aquatic macrophytes Communication, Etc

The greatest threat to the maintenance of ecological integrity is habitat destruction (Biodiversity Working Party 1991). Such changes could include serious pollution of sediments, reduction in stream flow by river regulation, removal of habitat (de- snagging, draining wetlands) or significant changes in catchment land use, any of which could cause significant ecosystem deterioration.

Further Readings Beverton, R.J.H Dynamics of single species. p.13-58, in: R.M. May (ed). Exploitation of Marine Communities. Berlin: Springer Verlag. Beverton, R.J.H Small marine pelagic fish and the threat of fishing; are they endangered? Journal of Fish Biology, 37(Supplement A): Christensen, V Indicators for marine ecosystems affected by fisheries. Marine and Freshwater Research, 51:

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