Fisheries Fisheries and and

Fishing MethodsFishing Methods

By K. MannetteMason Hall Government

Secondary

WHERE ARE WE?WHERE ARE WE?

Trinidad and Tobago is: an archipelagic state 10 km (7miles) off

the Venezuelan coast a geological extension of the South

American shelf. separated by 33 km (21 miles) of sea. north of 17 South American rivers

including Orinoco and Amazon Trinidad’s fishery is influenced fresh water Tobago’s fishery is more oceanic

GUIANA-BRAZIL CONTINENTAL GUIANA-BRAZIL CONTINENTAL SHELFSHELF

N

G U YA N A

S U R IN A M E

B R A Z IL

T R I N I D A D& T O B A G O

F R E N C HG U I A N A

O rin oc oR iv er D e lt a

A m a zo nR iv er D e lt a

S T A T E O FA M A PA

S T A T EO F P IA U Í

S T A T E O FC E A R A

N

AT L A N T IC O C E A N

S T A T E O FPA R A

parrot fish

parrot fish

Spanish hogfish

grunt

snapper

grouper

Why do we catch fish?Why do we catch fish?

Our FisheryOur Fishery Pelagic - swim continuously in open swim continuously in open

water, offshore. Nomadic as they do not water, offshore. Nomadic as they do not remain in one area.remain in one area. Coastal pelagics Oceanic pelagic (migratory)

Demersal- bottom foraging fish living bottom foraging fish living near or on the seabednear or on the seabed Soft bottom Hard bottom Deep bottom

Baraccuda

Common Fish Species in Common Fish Species in TobagoTobago

Wahoo

Cavalli

Shark

Marlin

Dolphinfish

Flying fish

Kingfish

Tuna

Grouper

LobsterSnapper

Conch

Fishing Methods in Trinidad and Tobago

Gillnetting Fillet net

(multifilament) Mono-filament net

Trawling Beach Seining Trolling Palangue (drift long

line)

Fish potting Spear

fishing A la vive

(live bait) Hook and

line

GillnettinGillnettingg

•Monofilament

•Multifilament

TrawlingTrawling

Beach Beach SeiningSeining

TrollingTrolling

Outrigger

Common in Tobago

Line with hooks are towed from outriggers

LonglinesLonglines

•Demersal

Pelagic

Fishpotting

Spear fishing

Water Safety and Water Safety and PollutionPollution

By K. MannetteMason Hall Government

Secondary

Water Water Safety DevicesSafety Devices

Life raft

Inflatable tubeInflatable tube

Rescue can

Life jacket

Water Safety DevicesWater Safety Devices Work by making it easier to float Work by making it easier to float

by reducing our densityby reducing our density

The safety device and your body The safety device and your body behave as one objectbehave as one object

This safety device is bigger than your This safety device is bigger than your body without being heavierbody without being heavier

Volume has increased but the weight Volume has increased but the weight has not increased so density has not increased so density decreases and you float more easilydecreases and you float more easily

Navigation DevicesNavigation Devices Accurate navigation around the ocean depends Accurate navigation around the ocean depends

on use of:on use of: Satellite navigation systems in boats that send Satellite navigation systems in boats that send

signals from boats to satellites and backsignals from boats to satellites and back

Stars as the position of Polaris (Pole Star) coincides Stars as the position of Polaris (Pole Star) coincides with the direction of the Earth’s North Pole. with the direction of the Earth’s North Pole.

Magnetic compass

Magnetic CompassMagnetic Compass depends on magnetismdepends on magnetism

compass needle always points to the compass needle always points to the Earth’s magnetic North Pole not the Earth’s magnetic North Pole not the true North Poletrue North Pole

The compass and the North Star are The compass and the North Star are

both used to find the true North Poleboth used to find the true North Pole

Hazards associated with Hazards associated with scuba divingscuba diving

If the diver holds his breath when If the diver holds his breath when ascending, air expands in the lungs causing ascending, air expands in the lungs causing the lungs to rupture.the lungs to rupture.

Decompression Sickness (Bends)Decompression Sickness (Bends) Nitrogen gas and Oxygen are pressurized in the Nitrogen gas and Oxygen are pressurized in the

scuba tankscuba tank The diver breathes in the pressurized air that The diver breathes in the pressurized air that

dissolves in the blooddissolves in the blood As the diver ascends, the dissolved air forms As the diver ascends, the dissolved air forms

bubbles as it leaves the bloodbubbles as it leaves the blood The Nitrogen bubbles accumulate in the joints of The Nitrogen bubbles accumulate in the joints of

the body causing a painful condition known as the body causing a painful condition known as Bends.Bends.

Water PollutionWater Pollution

It is the loss of any of the actual or It is the loss of any of the actual or potential beneficial uses of water potential beneficial uses of water caused by any change in its caused by any change in its composition due to human activity.composition due to human activity.

Water can look clean and clear but it can Water can look clean and clear but it can be pollutedbe polluted

Sources of Water PollutionSources of Water Pollution

Direct (Point) SourcesDirect (Point) Sources The origin can be identified e.g factory The origin can be identified e.g factory

outfalls, waste treatment plantsoutfalls, waste treatment plants

Indirect (non-point) sourcesIndirect (non-point) sources Origin cannot be pinpointedOrigin cannot be pinpointed Contaminants can enter water supply Contaminants can enter water supply

from soils and groundwater from soils and groundwater contaminated by human activities.contaminated by human activities.

Types of Water PollutionTypes of Water Pollution Toxic pollutionToxic pollution

A chemical pollutant that is not naturally occurring in A chemical pollutant that is not naturally occurring in aquatic ecosystems that poisons and kills organisms aquatic ecosystems that poisons and kills organisms in and near aquatic systemsin and near aquatic systems

Low levels of chemicals can accumulate along the Low levels of chemicals can accumulate along the food chain as predators consume large amounts of food chain as predators consume large amounts of slightly poisoned organisms. slightly poisoned organisms.

Examples:Examples: automotive productsautomotive products paints and solventspaints and solvents battery acidbattery acid industrial waste chemicalsindustrial waste chemicals toxic substances in car toxic substances in car

exhaust and solid waste exhaust and solid waste incinerator smoke.incinerator smoke.

PesticidesPesticides HerbicidesHerbicides Household cleaning Household cleaning

agentsagents GasolineGasoline OilOil

Sediment pollutionSediment pollution

Dirt, minerals, sand, and silt eroded from the land Dirt, minerals, sand, and silt eroded from the land and washed into the water from areas without and washed into the water from areas without enough vegetation to slow runoff.enough vegetation to slow runoff.

Particles suspended in water cause cloudinessParticles suspended in water cause cloudiness decreases the amount of sunlight reaching underwater decreases the amount of sunlight reaching underwater

plants that provide food and oxygen for aquatic animals.plants that provide food and oxygen for aquatic animals.

Particles settle into spaces between rocks, Particles settle into spaces between rocks, destroying the habitat of manydestroying the habitat of many aquatic insects and aquatic insects and macroinvertebrates.macroinvertebrates.

Clogs the gills of fish and aquatic organisms.Clogs the gills of fish and aquatic organisms.

Buries fish and insect eggs, preventing them from Buries fish and insect eggs, preventing them from hatchinghatching

Types of Water PollutionTypes of Water Pollution

Soil ErosionSoil Erosion SedimentationSedimentation

Caused by land clearing…

Nutrient pollutionNutrient pollution Presence of excess nutrients (nitrogen and Presence of excess nutrients (nitrogen and

phosphorus)phosphorus) Living things need nutrients, but too much Living things need nutrients, but too much

damages the aquatic environment. damages the aquatic environment. Too much nutrients cause excessive plant growth Too much nutrients cause excessive plant growth

(algae and vascular plants) causing water to be (algae and vascular plants) causing water to be clouded so sunlight cannot reach plants below.clouded so sunlight cannot reach plants below.

When those plants die, bacteria decompose them When those plants die, bacteria decompose them using up dissolved oxygen that aquatic organisms using up dissolved oxygen that aquatic organisms need to survive (Eutrophication)need to survive (Eutrophication)

Types of Water PollutionTypes of Water Pollution

Nutrient pollutants:Nutrient pollutants: fertilizersfertilizers animal manureanimal manure discharge from boat discharge from boat

toiletstoilets household detergentshousehold detergents

Sources of nutrient pollution:Sources of nutrient pollution: overflow from sewage treatment overflow from sewage treatment

plantsplants leaks from poorly maintained leaks from poorly maintained

septic systemsseptic systems discharge from factoriesdischarge from factories automobile exhaustautomobile exhaust

Disposal of sewage & Disposal of sewage & wastewaterwastewater

Results in unclean coastal water

Algae

CoralDeath of coral by

algal growth

Thermal PollutionThermal Pollution

Water near power or industrial plant is used as Water near power or industrial plant is used as coolant then returned to the environment at a coolant then returned to the environment at a higher temperature.higher temperature.

Decreases level of dissolved oxygen in water Decreases level of dissolved oxygen in water that aquatic organisms need to survive.that aquatic organisms need to survive.

Types of Water PollutionTypes of Water Pollution

Bacterial pollutionBacterial pollution An excess of harmful bacteriaAn excess of harmful bacteria

Water has beneficial bacteria but small amounts of Water has beneficial bacteria but small amounts of harmful bacteria are safe.harmful bacteria are safe.

Large concentrations of bacteria can be harmful to Large concentrations of bacteria can be harmful to organisms that ingest or are in contact with water.organisms that ingest or are in contact with water.

Sources of bacterial pollution:Sources of bacterial pollution: overflow from sewage treatment plantsoverflow from sewage treatment plants leakage from poorly maintained septic systemsleakage from poorly maintained septic systems animal manureanimal manure discharge from boat toilets.discharge from boat toilets.

Types of Water PollutionTypes of Water Pollution

Water PollutionWater Pollution CausesCauses

Organic matter (Nitrates, phosphates)Organic matter (Nitrates, phosphates) Fertilizers and manure from farms (plant and Fertilizers and manure from farms (plant and

animal remains)animal remains) Faeces from:Faeces from:

Septic tanksSeptic tanks YatchsYatchs Wastewater treatment plantsWastewater treatment plants

Chemical wasteChemical waste Oil spills, garage waste, oil leaksOil spills, garage waste, oil leaks Pesticides at home and commerciallyPesticides at home and commercially Cleaning agents from householdsCleaning agents from households

LitteringLittering

results in death of coral reefs…

& runoff into coastal waters

Beach ErosionBeach Erosion

Caused by coastal development…

& removal of coastal trees

& loss of beaches

Results in beaches with steep slopes…

SOLUTIONSSOLUTIONS

Keep or plant vegetationKeep or plant vegetation

Build walls & silt traps

SOLUTIONSSOLUTIONS

ACT RESPONSIBLY!

Water PurificationWater Purification Water can be cleaned and made safe for Water can be cleaned and made safe for

use by humansuse by humans

Methods of purificationMethods of purification FiltrationFiltration

Removal of large pieces of debris using a Removal of large pieces of debris using a filterfilter

Water enters a settlement tankWater enters a settlement tank Alum is added causing small particles to Alum is added causing small particles to

stick together and sink to the bottomstick together and sink to the bottom

Water PurificationWater Purification Methods of purificationMethods of purification

Removal of dissolved materialsRemoval of dissolved materials Done by distillationDone by distillation Water then percolates (drips) through huge filter Water then percolates (drips) through huge filter

beds.beds. Microorganisms in filter beds feed on dissolved Microorganisms in filter beds feed on dissolved

organic matter.organic matter. When water reaches the bottom of the filter bed When water reaches the bottom of the filter bed

all the organic matter has been removed.all the organic matter has been removed.

Removal of bacteriaRemoval of bacteria Chemicals (chlorine or sodium hypochlorite Chemicals (chlorine or sodium hypochlorite

solution) addedsolution) added

Water PurificationWater Purification Treatment of seawaterTreatment of seawater

Seawater can be treated to make drinking Seawater can be treated to make drinking water by the removal of salt through:water by the removal of salt through:

Solar distillationSolar distillation Heat from the sun evaporates water in trenches covered Heat from the sun evaporates water in trenches covered

in plastic. in plastic. Pure water vapour condenses on plastic, drips into Pure water vapour condenses on plastic, drips into

gutters and is collected for drinking.gutters and is collected for drinking.

ElectrodialysisElectrodialysis An electric current draws charged particles of sodium An electric current draws charged particles of sodium

and chloride (salt) out of the seawater across a special and chloride (salt) out of the seawater across a special membrane.membrane.

Water PurificationWater Purification Treatment of seawaterTreatment of seawater

Seawater can be treated to make drinking Seawater can be treated to make drinking water by the removal of salt through:water by the removal of salt through:

Vacuum freezingVacuum freezing Seawater frozen in a special vacuum chamberSeawater frozen in a special vacuum chamber As seawater freezes, some water ‘flash evaporates’ to As seawater freezes, some water ‘flash evaporates’ to

steam and is pumped out leaving salt behind.steam and is pumped out leaving salt behind.

Flash distillationFlash distillation Seawater heated under a low pressure.Seawater heated under a low pressure. Pure water vapour is condensed and drawn off as Pure water vapour is condensed and drawn off as

drinking waterdrinking water