Creating fishing grounds
A fishing ground is a place in the sea where many fish live and can be caught. Fish like places with hiding spots, food and calm water. A flat sandy bottom has none of these.
So people create fishing grounds:
- Artificial reef: concrete or stone blocks placed on the sea floor. Weed and tiny animals grow on them, small fish hide in the holes, and big fish come to eat the small fish.
- Seaweed and sea-grass beds: plants in shallow water give food and shade. Baby fish and crabs grow up among them.
- Shallow-water and tidal-flat improvement: sand and mud are added or shaped so that shellfish and young fish have a home.
Before building, experts check the depth, current, sea-floor type and what the local fishers need. A reef put in the wrong place may do nothing, or may block nets.
Waterfront development
The waterfront is the edge where land meets sea. People build things here to use the sea safely.
- Breakwater: a long wall in the sea. It breaks the waves so that the water behind it is calm.
- Quay: a strong wall along the shore where boats tie up and unload fish.
- Fishing port: breakwater + quay + fish market + ice plant + fuel and repair places.
- Sea wall and beach works: protect houses and roads from waves.
A good waterfront also keeps the shore healthy. A wall can change how sand moves, so engineers study the currents first.
Environmental improvement technology
The sea gets dirty from sewage, factory waste, farm fertiliser, plastic and oil. Dirty water takes away oxygen and kills sea life.
- Waste-water treatment: clean the water from towns and factories before it reaches the sea.
- Oil boom and skimmer: a floating fence keeps spilled oil in one place so it can be collected.
- Dredging: removing dirty mud from the bottom of a harbour. The mud must then be disposed of safely.
- Artificial tidal flats, seaweed and shellfish beds: living filters. Shellfish and plants take in extra nutrients and make water clearer.
- Monitoring: measuring oxygen, clarity and pollution so we know that it works.
Try it
Put a sponge and a few small stones in a tray of water with some plastic fish. Add more stones and more hiding places. Then scoop dirty water out and pour clean water in. Notice how the 3D works the same way: more shelter and cleaner water give a better home.
Key formulas and definitions
- Key words: reef (home for sea life), breakwater (wave-stopping wall), quay (boat wall), dredging (removing bottom mud), boom (floating fence).
- Reef volume = number of blocks x volume of one block.
- Fish in the 3D = 4 + 3 x (number of reef blocks).
Worked examples
1. A reef is made of 8 concrete blocks. Each block is 2 m x 1 m x 1 m. What is the total volume of concrete?
Volume of one block = 2 x 1 x 1 = 2 cubic metres. For 8 blocks: 8 x 2 = 16 cubic metres.
2. Before the reef, a spot had 4 fish. In the 3D lesson each block brings 3 more fish. How many fish are there with 8 blocks?
Extra fish = 8 x 3 = 24. Total = 4 + 24 = 28 fish.
3. Why is a breakwater built at a fishing port and not just a tall quay wall?
A quay only gives a place to tie up. Waves would still move the boats and bump them on the wall. The breakwater stops the waves first, so the water inside is calm and boats stay safe.
4. A waste-water plant cleans 6000 litres of water each hour. How much does it clean in a 10-hour day?
6000 x 10 = 60,000 litres in a day.
Common mistakes
- Thinking a reef creates fish out of nothing. It gives homes and food, so fish stay and grow there. The fish still need a healthy sea.
- Thinking a breakwater is only for ships. It also protects the shore, fish farms and people.
- Dumping the dirty mud back near the same place after dredging. Dredged mud has to be put in a safe, planned place.
- Thinking that more concrete is always better. Too many blocks in the wrong place can block nets and harm the sea floor.