1. Overview

Steel reefs are built as an artificial habitat where fish can live, spawn, and find shelter.  So this steel structure is often called an "apartment complex for fish".   Recently, the old concept of fishery based on 'catching fish' is giving way to a new concept of fishery 'growing fish'.  The demand for sophisticated coastal fishing ground is on the rise as well.  Against this backdrop, POSCO successfully obtained the certification on the three types of steel reefs from the Ministry of Maritime Affairs and Fisheries on March 2, 2001, laying the foundation for the commercialization of steel reefs.

2. Technological Overview

Three main technical factors which must be considered when designing and manufacturing steel reefs

	Structural Stability
	For designing and building stable structures, all elements of ocean environment including waves must be carefully considered.
	Fish Aggregation Effect
	Steel reefs should be designed and manufactured in a way that ensures proper shadow, enough attachable surface area and ample internal space, all the while considering the behavior pattern of inhabiting fish.
	Anti-Corrosive Technology
	Steel reef must be corrosion resistant so that it could remain functional for a long time without going rusty.

3. Types of Steel Reefs

SIZE / VOLUME : 14m*14m*9m / 804㎥ Features: As the base is large, it is very unlikely to turn over or get lost.  This type of steel reef has an advantage in attracting ground fish. East Sea South Sea SIZE /VOLUME : 9 m*9m*10.2m / 826㎥ Features : This type of steel reef interrupts the water flow, forming a side current which is a favorable environment for fish.  Also, its complicated structure attracts sedentary fish species.    East Sea South Sea SIZE / VOLUME : 10m*10m*2m / 164㎥ Features : Its broad base prevents soft ground from sinking or subsiding.  Nutrient salts float along the slope of steel structure, which creates an appealing environment for fish.   West Sea South Sea

4. Advantages

General Features

	Steel reefs can be produced in large sizes and installed in deep water.  The light weight of steel reefs is also suitable for an installation on soft sea floor.
	It is possible to manufacture various types of steel reefs.  They are also easy to transport and install.
	Steel surface releases iron ions, a vital nutrient for plant planktons, thus attracting a large number of fish.
	Compared to concrete reefs, steel reefs are more durable and environment-friendly.

Economic Aspects

Reef Types Size (m) Volume Remark Volume (㎥) Cost (won) Steel Reef 9*9*10.2 826 84,725 Fish Concrete Rectangular 2*2*2 8 90,260 " Hemisphere Φ2*1.3 3 155,280 Shellfish Overpass-type 2.4*2.4*1.2 2.4 219,790

Amount of Steel Corrosion (in 30years)

Classification  Up to 50m (depth of water) 50m~200m (depth of water) Warm water 2.4mm 1.8mm Cold water 1.8mm 1.35mm

Five years after installation, the speed of steel corrosion is reduced to half of the initial speed.  

5. Effects of Steel Reef

Research Institute : National Fisheries, Busan National University  Study Period : '92.6 ~ '93.11 Study Subject : Steel reefs which were installed in Nov. 1988 in the coastal area of Pohang