A fishing shelter generally requires regular maintenance to keep it functioning properly.
Shelter maintenance falls under two broad headings:
- Environmental control of naturally occurring phenomena. This type of maintenance includes dredging (sand may silt up the entrance to the shelter periodically) and controlling floating weeds and flotsam.
- Antipollution control of fishing activities. This covers the collection and proper disposal of liquid and solid wastes generated by fishing activities.
If a shelter lies on a sandy coast it may be prone to silting up periodically. In most cases this calls for dredging. Dredging involves the quick removal of accumulated sand by mechanical means and it is a very costly operation.
Before any dredging operations are undertaken, a fairly precise estimate of the volume of dredged material is usually required. This is best achieved by drawing up a grid map of the soundings in and around the shelter area (see Chapter 2) and updating it as required (every six months or yearly). The amount of deposited material can then be calculated and the best type of dredging equipment to use determined.
Loose sand. For very small quantities of sand (1 000 m3 or less) in the inshore zone, consideration should be given to using either a submersible pump suitable for suspended solids or a hydraulic excavator. Either or both of these items may be available from a local contractor.
A hydraulic excavator should be operated from a mound of core material (see Chapter 3) that has been specially dumped for the purpose. It should work backwards towards land, scooping up both the sand to be dredged and the core.
A suitable submersible pump usually runs on compressed air. The pump can be installed on a fishing boat if the area to be dredged is faraway from the quay.
The size and operating pressure of the compressor determine the maximum working depth of the pump.
For large quantities of sand (1 000 - 10 000 m3) distributed over a large surface area, a pontoon-mounted excavator should be considered. The operating depth will be governed by the length of the excavator's forearm.
Larger quantities of sand should be tackled by professional
dredging contractors using suction dredgers.
When dredging, care should be given to where the dredged sand is to be dumped. It should not be dumped where currents can transport it back to where it was dredged from.
Cemented sand, coral and clay. When
the materials to be dredged include lightly cemented sand (weak
sandstone), coral and coralline deposits and clays a cutter
suction dredger, like the one shown in Figure 68, is usually
required to break up the material before it is pumped away for
For very small quantities, a hydraulic excavator equipped with a very narrow-toothed bucket may suffice.
Hard rock and boulders. In general, a rocky sea-bed cannot be dredged economically. However, rocky outcrops or the occasional boulder can be tackled by explosives and then dredged as normal.
Seaweed. Seaweed may be indigenous
to the area where the shelter is located or it may be brought in
as flotsam by wind or currents. Non-indigenous seaweed is usually
When seaweed is indigenous the shelter should be dredged to rid the area of roots. This operation may have to be repeated frequently to prevent fresh weed from growing again.
Before uprooting indigenous weed the advice of the fisheries department should be sought. Some seaweeds have important biological functions, such as providing food or nursery grounds for local species of fish, and removing them may damage the environment.
Dead seaweed can either be caught in nets strung across the mouth of a harbour during certain times of year or else it can be collected by hand off the beach after a storm. Dredging by any other means is very time-consuming and uneconomical because seaweed tends to foul most moving mechanical parts.
Flotsam and bulky waste. In addition
to dead seaweed, flotsam can also consist of dead-timber or cane
brought down a river by a flood. A harbour may also contain
manmade rubbish, such as old tyres, pieces of old rope, oil cans
and batteries, that has been dumped overboard.
Cleaning a shelter of natural flotsam can be very laborious. Consideration should be given to preventing flotsam from entering the harbour in the first place by stringing a fishing net across the shelter entrance when the wind blows from directions known to bring in floating debris.
Manmade rubbish can only be picked up by a diver or dredged by a crane-operated clam-shell bucket. Both solutions are expensive and antidumping laws should be strictly enforced by the harbourmaster to cut down on the amount of manmade rubbish.
The pollution in and around most fishing shelters falls into three main groups:
- Visible pollution of the harbour water by spilt fuel or discharged raw sewage. This visibly affects the quality of the water.
- Invisible pollution of the water by hazardous wastes, such as heavy metals (cadmium, mercury, lead, nickel and so on) and paint solvents. This does not affect the appearance of the water but causes invisible pollution.
- Degradation of the natural harbour environment by discarded litter, above and below water level. Though not necessarily toxic, litter dumped into the harbour basin interferes with routine dredging operations, making maintenance very expensive.
The most common pollutants associated with fishing are:
- Spilt diesel fuel from faulty hose pistols, leaking drums and generally careless handling during refuelling operations.
- Discarded used engine oil and bilge water dumped overboard.
- Raw sewage dumped into the harbour from the onboard toilets.
- Offal from fish being gutted and cleaned onboard boats inside the harbour.
- Discarded starter batteries, rechargeable nickel-cadmium cells from radios, torches and walkie-talkies and button cells from watches, calculators, clocks, etc.
- Unwanted tyre fenders, lengths of wire rope, chain and nets dumped into the water.
- Discarded engine blocks and rusting hulls and trailers.
- Discarded containers, such as polystyrene fish boxes, oil and grease cans and paint containers.
All of these pollutants arise from human activities that should be controlled by:
- Quayside regulations and enforcement.
- Waste management and recycling.
Quayside regulations are laws designed to protect the environment from abuse by unscrupulous harbour users. In particular, such regulations should prohibit:
- The dumping of crank-case oil and bilge water overboard.
- The flushing of onboard toilets inside the shelter.
- The cleaning of fish onboard moored vessels.
- The discarding of any type of battery.
- The littering of the port area with any kind of waste.
- The use of toxic antifouling paints.
Annex 3 provides a complete series of cartoon drawings entitled "Cleaner harbours". These outline both the sources of pollution and the remedial measures recommended to mitigate them.
Each of the regulations mentioned generates a concentration of waste product which, if not collected and recycled properly, becomes a hazard to the well-being of the fishing community.
To manage this waste properly, a good collection system and a method of recycling or safe disposal are necessary. Both are important and the one cannot be implemented without the other. It is pointless collecting used oil in a big container if the person collecting the oil does not know what to do with it. For waste management to function properly, it must be integrated into the existing commercial or artisanal activities.
The proper ways to collect and recycle various kinds of waste are described in the following pages.
Used engine oil
Collection. The waste oil should be collected in modified 200-litre oil drums (Figure 99) strategically placed inside the fishing shelter. The drums must not remain in contact with the ground because, if they get wet or damp, they may corrode and leak oil.
Recycling. Specialist oil processing companies take back used oil for reprocessing if you can guarantee them a regular supply. Some government agencies actually run a collection system on a national scale for a small fee.
Collection. Bilge water consists of sea water mixed with oil that has leaked out of the engine oil-seals. Bilge water should be pumped out from the boats and put into a receiving tank similar to that shown in Figure 100.
Recycling. Bilge water is easily separated into oil and sea water if it is allowed to settle naturally. Water, being heavier than oil, will settle to the bottom. Using the small tap, it can then be gently drained off into a container and evaporated. The oil/diesel residue can then either be used for heating purposes or poured into the usedoil storage tank.
12-volt starter batteries
Collection. Spent 12-volt batteries contain plates of lead immersed in acid inside a plastic case. Sunlight may decompose the plastic casing, so it is important not to abandon the batteries out in the open. Lead is very toxic and if not handled properly may enter the food chain. Used batteries can be stored in a large bin, as shown in Figure 101, until collected.
Recycling. Most suppliers take spent batteries back for industrial reprocessing. If done properly, lead plates can be recycled at village level to make sinkers for nets. The acid must be disposed of separately in plastic tanks.
Toxic solid waste
Collection. Toxic solid waste comprises all those manufactured items that cannot be dissembled. Oil filters, spark plugs, torch and radio batteries, button cells from watches, containers of paint stripper and hydraulic oil are all forms of toxic solid waste. Plastic drums (Figure 102) should be strategically placed around the shelter. Old oil drums which rust and permit toxic chemicals to leach away into the ground are not suitable for these materials.
Recycling. Very little recycling can be done with these items and generally speaking they should be buried in special landfills away from drinking-water wells.
Non-toxic solid waste
Collection. Non-toxic solid waste comprises all other bulky rubbish, such as old tyres, old pieces of rope and netting, broken fish boxes and so on. Figure 103 shows a typical collection point made of locally available stone and concrete (the size of the waste centre depends on local requirements).
Recycling. Metal items should be collected and sold to scrap dealers. Tyres can be turned into fenders, timber fish boxes can be sold as fuelwood. Styrofoam boxes should be avoided because they break up easily and cannot be recycled safely (they give off dangerous fumes when burnt).
Collection. Fish should be cleaned and gutted on the journey back to the harbour and the offal should be dumped out at sea where it provides food for other fish. Offal should never be dumped inside the harbour basin or discarded in corners within the harbour area or village because, besides giving off offensive smells, it also poses a health hazard by attracting pests. Plastic 100-litre drums with airtight lids (Figure 102) should be bought and used to collect offal from fish markets or moored boats.
Disposal. When mixed with some types of grain, offal can be used as animal feed or fish silages.. Very small quantities can safely be buried.
In or around the fishing harbour or landing, the sources of raw sewage may include the village outfall together with the boats' onboard facilities that discharge directly into the water. As described in Chapter 6, the harbour should be provided with toilets and the whole area should be connected to a septic tank and soakaways (Figure 90).
Dumping raw sewage near the fish landing exacerbates health problems, creating a potential flashpoint for disease.
Special note on plastics
Most common household plastic containers (buckets, containers and basins) are not suitable for outdoor use because the PVC they are made from ages rapidly and cracks when exposed to the sun's rays. If such items contain foul or toxic waste, they should not be left exposed to the sun for lengthy periods.
The following are some additional environment-friendly tips:
- Try not to use polystyrene fish boxes unless absolutely necessary. Rigid plastic ones are available and last longer. If these are too expensive, wooden ones should be used.
- If the fishing village is a long way from a main town or city, consumables should be bought in bulk at village level. For example, instead of buying 50 1-litre cans of oil, a 50-litre drum of oil should be bought by the village and sold by the litre to individual users. A 50-litre drum may be returnable but the 50 1-litre cans have to be disposed of locally because nobody will take them back.
- Moving mechanical parts (such as hinges, winches and ratchets) should be greased and not oiled. Grease tends to stick to the moving part so requires fewer applications. Oil, on the other hand, runs off the part very quickly and needs constant replenishment.