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1.1 Introduction

Artificial Reef is one or more objects of natural or human origin deployed purposefully on the seafloor to influence physical, biological, or socioeconomic processes related to living marine resources. Artificial reefs (ARs) are becoming a popular biological and management component in shallow water environments which is characterized by soft seabed, representing both the importance of marine habitats and tools to manage coastal fisheries and resources. The unstable nature of sediments has made them to require a detailed and systematic investigation that acoustic systems can provide. An AR into the marine environment acts as an open system where it has exchange of material and also the energy, altering the physical and biological characteristics of the surrounding area. The AR stability will depend on the balance of scour, settlement, and burial resulting from ocean conditions over time.

Artificial reefs have been constructed and placed in Kelantan island to provide structure for a wide range of reef associated fish species and also to further the management goals; the enhancement of recreational and commercial fishing and the rehabilitation of depleted fish. Artificial reef material has been deployed to provide hard-bottom substrate in an area that naturally consists mostly of sand, mud, and hard-bottom structure with little vertical relief. Once dropped in the water, artificial reefs require monitoring to track the impact on the environment and maintenance needs. Artificial reefs don’t actually increase the amount of fish, but that they instead concentrate them around a specific area. Higher density of fish not only aids in the spread of fish diseases but it also makes it easier for them to be caught, adding to the overfishing problem.

Reef spacing is one of the physical components of artificial reef complexes that may affect the recruitment of fishes to the structures. The management of artificial reefs should include consideration of reef spacing to minimize the overlap due to consequences of resource depletion.

A multi beam echo sounder is a type of sonar that is used to map the seabed. Like other sonar systems, multi beam systems emit sound waves in a fan shape beneath a ship’s hull. The amount of time it takes for the sound waves to bounce off the seabed and return to a receiver is used to determine water depth. Unlike other sonars, multi beam system use beamforming to extract directional information from the returning soundwaves, producing a swath of depth readings from a single ping

Fine-scale distribution of reef units, unprecedented level of resolution, coverage, and spatial definition can be obtained through the potential of the high frequency multi beam echo sounder. Detailed and systematic investigation are required that acoustic systems can provide due to the unstable nature of sediments. They have been deployed around the world for a wide number of reasons including fisheries protection and enhancement, environmental protection and rehabilitation, research, education, and tourism. ARs can modify flow velocity and turbulence intensity around and in the vicinity of the structures, which can lead to scouring and changes in sediment accumulation in the surrounding area. The environmental changes on the adjacent seafloor can physically affect the artificial structures. Thus, the stability of ARs will depend on the balance of scour, settlement, and burial resulting from ocean conditions, over time.
Multi beam sonar can be used for both bathymetric mapping and backscatter imaging. MBES has been widely used in mapping seabed morphology and composition, pipeline routes, coral reefs, wrecks, mines and their extent of burial. Besides, MBES is also used to monitor the artificial reef units or to investigate the horizontal and vertical movements and subsidence. This monitoring program useful in generating a baseline of data to assist decision makers and researchers to evaluate the artificial reef function, test design, choices and verify whether the reef is achieving or not its objective. The record of artificial reef status, fish abundance and habitat characteristics are done with the frequency of once a year during the first five years after the reef were placed and of every two or three years thereafter.

Later, multi beam echo sounders have been employed giving metric information and providing a useful description of the local hydrodynamics and geological processes affecting the reef. The performance of MBES required the data to be processed to achieve a careful data collection in order to reduce instrumental and integration artefacts that could easily mask the scale of feature in mapping. High-resolution multi beam bathymetry data were collected and used to evaluate the terrain changes around the structures. Usually, all multi beam data were cleaned and processed using software QPS Fledermaus, Qinsy, Qimera and FMGT. Post processing data includes editing, cleaning and resolving position and vessel attitude problem. Tidal correction was applied to the depth soundings using verified tide data. 3D spatial coverage of the MBES data, the seafloor depth was determined quantitatively through statistical examinations or drawing out seafloor profiles. The depth of the scour pit or the top of each artificial reef unit was measured directly through profiling across the scour pit or the artificial reef unit.
MBES also provide direct estimates of AR unit which were buried depth and surface area that reach the limits of accuracy of the MBES system. The detail and coverage provided by the multi beam sonar, along with the ability to render and visualize the seafloor bathymetry and every single AR structure in 3D offered several approaches to map the reef and measure the depth of burial of its unit by the MBES surveys.
Bulk volume of the reef was defined as the overall volume within the AR boundaries including the volume of the material and the space enclosed within the external AR structures and the free space between them. It is given by:
Bulk Volume = ????????
The area of the reef, is the mean height of all estimated submerged structures. Further MBES water column surveys are underway in combination with set-netting samplings to evaluate abundance and spatial distribution of fish schools as well as scuba diver observations and Remotely Operated Vehicle (ROV) video are planned in order to verify the MBES bathymetry data. When combined with other comprehensive field studies and modelling efforts, the multi beam sonar came in handy for providing a unique perspective on the nature of the seafloor surrounding the AR deployment site and new insights into the AR site burial process.

1. 2 Company Background

University Malaysia Terengganu (UMT) is the 14th public university established in Malaysia. It first became fully autonomous as a university college on 1 July 2001 and was renamed University Malaysia Terengganu on 1 February 2007 from Kolej Universiti Sains dan Teknologi Malaysia (KUSTEM) to Universiti Malaysia Terengganu(UMT). UMT is located along the South China Sea in Kuala Terengganu and not far from Lake Kenyir, the largest man-made lake in South-east Asia. Its strategic location makes UMT among the top public universities in a number of specialized fields such as oceanography and marine science. A peaceful environment, experienced staff and a friendly community makes UMT an institution that is conducive in teaching and learning.
In the aspect of research, UMT has been and continues to strive for excellence in the fields of sciences, technology, and management of natural resources. UMT also expands its opportunities, scope and research activities in maritime studies, economics, management, basic sciences, physical sciences, engineering and computing. Achievements and awards received by senior researchers at various exhibitions and research competitions at national and international levels is proof that these fields of studies were recognized. The slogan of UMT, Ocean of Discoveries definitely describes that UMT’s efforts in innovation meet the aspirations of the nation.

1.2.1 Company logo

Figure 1 1Logo of Universiti Malaysia Terengganu

1.2.2 Vision

To be an institution that generates, disseminates and applies innovative knowledge and can be a catalyst for the development of progressive and a sustainable environment.

1.2.3 Mission

To drive the fields of science, technology and management of natural resource via the generation of excellent academic and research programmes towards the development of individuals who ensure the sustainability of religion, race and the nation.

1.2.4 Organization chart
1.3 Background project

This project tells about the application of multibeam sonar on artificial reef mapping. The data is taken in year 2016. This method is used as the satellite could not map what lies under the sea water. Plus, satellites have certain resolution and most of the it is not suitable to be used in mapping the artificial reef. The average depth of the artificial reef in Tumpat is 20m from the sea surface. So, in this project the mapping area of artificial reef can be proved whether this method is suitable or not to map features in the seabed. Raw data is taken during conducting sampling in the survey area which is located at Tumpat, Kelantan. The estimated coordinate for the location is 6.1991° N, 102.1694° E. From the data obtained, processing and cleaning are necessary to get the result before it can be used for other purposes. The software used to process this data is by using QPS Qimera software. After the final results is out, then the data can be concluded either this method is suitable or not to map seabed features.

1.3.1 Aim

To study the potential of multibeam sonar for mapping artificial reef in Tumpat, Kelantan.

1.3.2 Objectives

1. To apply backscatter technique for determining the distribution of artificial reef.
2. To map the distribution of artificial reef using multi beam sonar method.

1.3.3 Problem statement

The issue of this study is, we want to know the distribution of the artificial reef in Tumpat and to determine whether multi beam sonar method is suitable or not for mapping the features. The determination of the location for the artificial reef is really important so that the data can be obtained without dislocate the exact location where it lies. When the distribution of the ARs can be mapped, it might be useful for the people to locate the location for fishing and other purposes. The depth of the artificial reef from the sea surface is important to ensure the safety of the ship from having collision. Both navigators and the ecosystem habitat below the sea surface can receive benefits. As for the navigators, they will be more alert with the ship route; suitable and safe route for ships. On the other hand, the artificial reef conditions will can be avoided from damages and at once can preserve the marine lives.

1.3.4 Study area

The location of this study area is located near with Tumpat, Kelantan. The estimated coordinate is 6.1991° N, 102.1694° E. The method used to obtain the data is by using the application of multibeam sonar using. This method is used to show how much the capability of the multibeam can detect the artificial reef in the seabed.

Figure 1 3Study area of artificial reef in Tumpat, Kelantan.

1.3 5 Scope and limitation

The data needs an exclusive software to be processed due to its difference data processing. Tide data need to be merged together to ensure the level of the sea water where the sensor is placed is equal with the Mean Sea Level (MSL). The instruments used to detect the ARs also has a limit to reach the seafloor. ?


2.1 Introduction

Artificial reef or commonly known as tukun is a man made, underwater structure built for the purpose of promoting marine life in areas of generally featureless bottom. Usually it serves to improve the hydrodynamic for surfing or to control beach erosion. Generally, it is designed to provide hard surface for algae and invertebrates to attach. It helps the accumulation of attached marine life to provide intricate structures and food for assemblages of fish. Hence, it can improve the growth rate of small fishes and other marine lives.
However, artificial reef was built back then were not for ecological reasons but for trapping enemy ships and thwarting Indian pirates. Japan is the first to build the artificial reef for the purposes of ecology in 17th century when rocks and rubble were used to grow kelp (brown seaweed) and increase fish yield.
Specifically, artificial reef was introduced by Royal Australian Air Force where based in Butterworth, Penang in 1970s. They built artificial reef using tires and mounted on Songsong Island in Langkawi for recreational purposes. Malaysia is the first country in Southeast Asian region to construct artificial reef in 1975. The first artificial reef was on Pulau Telur, Kedah on March 6, 1975 by using about 6329 tires. Meanwhile on October 11, 1975, about 5229 tires are used to build artificial reef at Payar Island.
Artificial reef Recreational reef
The aim is for conservation purposes. The aim is for capturing the most responsive recreational fishing
Tires are used by Research and Development (RnD) program of artificial reef in Malaysia begin in year 1975. During that time, tires are being used as it is more easy to be purchased and more cost effective. Moreover, it produces and enhances the marine life on the seafloor of the ocean. Then, Department of Fisheries and Researchers created various designs of artificial reef by introducing new material like PVC pipes, ceramics, boats and concretes enclosed within an area of less than five nautical miles. In year 2006, Department of Fisheries constructed concrete artificial reef made up from mixture of sand and stones and reinforcement of some iron. Department of Fisheries classify artificial reef as artificial reef and recreational reef. Table below show the number of artificial reef in Kelantan.

Table 2 1 Differences Between Natural Reef and Artificial Reef

2.2 Artificial Reef

Basically, artificial reef is constructed for protecting, regenerating and enhancing the populations of living marine resources. Reef materials are based on several considerations which are their functions, compatibility, durability and stability. Now, artificial reefs are made from more durable items ranging from discarded tires, concrete rubble, derelict vessels, and other discarded solid materials to prefabricated and highly engineered structures made from concrete, steel, fiberglass, and polyvinyl concrete (Grove and Sonu, 1985).

2.3 Difference between AR and natural reef

Artificial reefs can attract a lot of marine species including corals, sponges, and algae, increasing overall reef biomass and aggregating fish species, which in turn can support an entire marine ecosystem. In creating homes, breeding areas and protective spaces, the artificial reef is designed using safe pH neutral material with textured surfaces. These permanent structures are placed and fixed on the seabed to avoid being displaced by storms and extreme weather conditions.
The importance of habitat differences between artificial and natural reefs for the difference in fish density include the materials used to build the reef (e.g. rocks, concrete, sunken boats, etc.), substrate complexity, vertical relief, size, and spatial configuration. The increases of habitat complexity are due to the higher densities of fish on artificial reefs than on natural reef. However, artificial reefs differ from natural reefs in additional ways where usually natural reef have a higher ratio of reef perimeter to reef surface area compared to natural reef. This difference has also results for higher density of fish found on artificial reefs (Jessee et al., 1985; Belmaker et al., 2005) by attracting fish from a larger area which have low edge to area ratios (DeMartini et al., 1989). Moreover, artificial reefs may enhance larval settlement of some species (Rilov and Benayahu, 2000).
Artificial reefs provide habitat for the same diversity of fish, invertebrates, and plants that natural reefs do. Common endpoints used to evaluate successfulness of artificial reefs are numbers, biomass, and species richness of both fish and coral. The duration of recruitment and the extent of attainment are also important to be considered. It is possible that the same or better level of fish species richness and density found in undisturbed natural coral reefs may be obtained with artificial reefs within 1 year of deployment (Clark and Edwards, 1999).
Artificial reefs are often promoted as mitigating human impacts in coastal ecosystems and enhancing fisheries; however, evidence supporting their benefits is equivocal. It must be compared with natural reefs in order to differ their performance. During comparison between coral and fish communities on two large (;400,000 m3) and mature (;25 year) artificial reefs with six natural coral patches, the result shows that coral cover was higher on artificial reefs (50%) than in natural habitats (31%), but natural coral patches contained higher species richness (29 vs. 20) and coral diversity (H? = 2.3 vs. 1.8). Multivariate analyses indicated strong differences between coral communities in natural and artificial habitats. These results indicate that large artificial reefs can support diverse and abundant coral and fish communities. However, these communities differ structurally and functionally from those in natural habitats, and they should not be considered as replacements for natural coral and fish communities.

2.4 Purpose of Artificial Reef

The main purpose of artificial reef constructions is due to the damages that struck the coral reef lives in the seabed of the ocean. During the global bleaching crisis in 2015, more than 70% of coral reef worldwide experienced prolonged warm ocean temperature which is hot enough to kill them. The number of coral reef live in the seabed play an important role in controlling the production of the fishes. Thus, authorities in charge has took an initiative by constructing various types of artificial reef to preserve the ecosystem due to the extinction of the coral reef. The material of the artificial reef makes it durable and functions in longer period and at the meantime helps with the increment of the number of fishes.
An AR within the marine environment acts as an open system with exchange of material and energy, altering the physical and biological characteristics of the area where it is deployed.

2.5 Benefits from artificial reef

Nonetheless, if habitat is limiting, new reefs can potentially increase fish production through three mechanisms: an increase in the foraging habitat of adult, or newly recruited fishes, an increase in the nesting habitat of adult fishes, and an increase in the amount of resting habitat from predators. As a result, stock sizes of economically important species increase, and both recreational and commercial fishers benefit. Construction of additional artificial reefs will have no effect on fish production; it will merely cause a redistribution of existing biomass (Bohnsack 1989; Polovina 1991). This may have differing effects on stock size depending on the stock segment affected. For example, if reefs disperse exploitable biomass and have no effect on unexploited biomass, then construction of new reefs should reduce the chance of stock overexploitation, assuming that fishing effort or power does not increase (Polovina 1991). However, if reefs concentrate both exploited and unexploited segments of a stock, then the probability of stock overexploitation increases, even if effort does not change (Polovina 1991). If effort increases concomitantly, then the probability of overexploitation may increase substantially. Given that the relationship between reef construction and the probability of stock overexploitation is influenced by changes in fishing effort, it is appropriate to assess the likely effects of new reefs on fishing effort in a given area. One of the greatest benefits of artificial reefs is that they have lifted the pressure off natural reefs which, over the past few decades, have been over-fished and over-visited. By diverting attention to artificial reefs, natural reefs have now been given a greater chance to repair and to regenerate.

2.6 Threat to Artificial Reef

Poly-chlorinated biphenols (PCBs) and heavy metals (Pb, Cu, Ni, Cd, Zn, Ag, and Hg) have become an issue of concern with artificial reef development which may contain quantities of these toxic materials that may potentially be transferred through the food chain. This transference, may have unforeseen effects on the marine environment and at the same time human health through consumption of contaminated fish and shellfish from these reefs. However, thousands of ships have met their expiry without the environmental cleansing and preparation that artificial reefs require and may be potentially greater health risk to consumers and divers.
Overfishing has led to an alarming decline of certain fish species in the ocean’s natural food chain. New industrial fishing methods have the ability to devastate fish stocks beyond recovery. Bottom trawling and dynamite fishing are the land equivalent of razing a forest to the ground. 76% of the world’s fisheries are already fully exploited or overfished. The removal of herbivorous fish transforms the ocean substrates in destroying natural marine habitats and coral reefs.
Marine pollution, is the spreading of harmful substances such as oil, plastic, industrial and agricultural waste and chemicals in to the ocean.
On average humans use over 300 million tonnes of new plastic every year and only half is used once. 8 tonnes of plastic waste have been dump into the ocean annually.
Marine species suffer directly from plastic pollution, 90% of sea birds have plastic in their stomachs. Plastic attracts toxic chemicals released from industry and agriculture and so the concentration of toxins increases as it moves up the food chain. Entry of plastic toxins into the human food chain is a concern and have been suggested to contribute to some cancers, infertility and behavioral disorders.
Oil (liquid petroleum hydrocarbon) enters the ocean from oil spills, routine shipping, run offs and dumping. About 12% of oil in the ocean is directly from oil spills. Oil directly affects the water repellency of bird feathers and destroys the growth ability of fur-bearing animals exposing them to the harsh elements of the environment and the creatures often die from hypothermia.

Figure 2.1 Illegal Activities Around Artificial Reef Location
The fast-paced action of the Pahang Fisheries Department’s Resource Protection Unit, which uses 600-horsepower-powered speedboat with two Vietnamese fishing boats with 22 crewmen carrying fish-carrying activities in Nenasi waters, Pekan. the location is located at about 29 nautical miles from the beach Sungai Miang, Pekan. besides, from the inspection made by the Protection Unit they found that the boat used did not have a license, used gunting trawlers and catch gamat using a special tool called penny. The action charged is they could be compounded up to RM20,000 or boat license suspended or canceled under the Fisheries Act 1985.

2.7 Different method in evaluating reef according to its purpose

Methods used to evaluate the performance of an artificial reef will vary according to the purpose for which the reef was built. To determine how well artificial reefs mitigate losses due to human activities on natural reefs, the performance of artificial reefs should be evaluated using contemporaneous comparisons with relatively undisturbed natural reefs. Unfortunately, comparisons between artificial and natural reefs are typically confounded by differences in reef size, age, and isolation. Species richness and fish abundance (all species combined) were greater on natural reef rather than artificial reef, but substantial differences in species composition were not detected. Because of the open nature of most reef fish populations, estimated of the contribution of artificial reefs in attracting and producing reef fishes will require a regional assessment of rates of demographic processes on both artificial and nearby natural reefs (Carr and Hixon, 2011)

Figure 2.2 The Deployment of Cuboid Tukun in The Area of Chempaka, Kuantan.

Department of Fisheries, DOF) Pahang have made some effort to rehabilitate the reproduction of fishes by deploying 41 units of concrete artificial reefs with two types which are cuboid and tetrapod in area Chempaka, Cherok Paloh and Pantai Sepat, Kuantan within seven years. The distance between the artificial reef and the shore in the three location are about five nautical miles and depth exceeds 10 meter. The artificial reefs are placed between two meters of each other. In addition to being used as a breeding ground for various types of fish, the cuboid type has also become a barrier to the activity of trawlers who previously had been reported in the waters of the state.

The four-dimensional (Kuboid) artificial reefs of size 2.5 x 2.5 x 3 meters serve as breeding grounds for various types of fish such as grouper, keris, merah, kuning selangar, kembung, prawn and squid. Artificial reefs placed in the three waters of this area are expected to increase the income of local fishermen involved in fishing activity.

2.8 Tukun in Malaysia

2.8.1 Concept Of The Construction Of Artificial Reefs

There are two concepts of construction of artificial reefs by the Department of Fisheries of artificial reefs artificial reef conservation and recreation
• Artificial Reef conservation – aimed at conservation, not arrests.
• Artificial Reef Recreation – is to catch recreational fishing in a controlled manner.

Table 2 2 The Number of Artificial Reefs Sites in Every State in Malaysia
PERLIS 2 – 2
KEDAH 18 1 19
PERAK 4 3 7
MELAKA 3 1 4
PAHANG 7 2 9
JOHOR 3 2 5
W.P LABUAN 9 2 11
SABAH 16 21 37
SARAWAK 10 4 14
TOTAL 118 42 160

2.8.2 Types of artificial reef in Malaysia

Malaysia have produced several types of artificial reef based on its function and suitable materials that will not pollute surrounding environment. Table below shows the types and the suitable depth in placing the artificial reef.

Table 2 3 Types of Artificial Reefs Used in Malaysia
Types of artificial reef Dimensions (m) Weight (kg) Depth (m)
Tyres 150 16-20
Ships Depends on the size of the ship Depends on the size of the ship 16-20
Ball reef 1.8288 x 0.9144 1800 20
Cuboid type 2.5 x 2.5 x 2.5 8000 25
Soft base reef 3.45 x 3.45 x 2.5 28000 15
Recreation reef 1.8 x 1.85 8000 20
Barrier trawlers reef 3.45 x 3.45 x 3.725 30,000 20-25

Table 2.3 above shows each types of artificial reef and their characteristics that were introduced in Malaysia.
The average weight of reef-concrete artificial reefs are between 0.3 – 42 tones. Grade cement used is between grades 30 – 50. For reefs steel using steel with a thickness of 6-8mm. Tires-type reef

Although tires seem not to be the most suitable material to be used as artificial reef, but there is opinion proves that tires not contaminate the sea water. The statement is proved by the US National Artificial Reef Plan (Stone, 1995) includes tyres as a reef construction material, noting that no toxic effects attributable to leaching or decomposition have been demonstrated. Ship-type reef

Ship-types reef used to save up the space and to avoid from being a waste. The ships at first is cleaned from any oil. After the level of cleanliness is suitable for the habitat in the seabed to live, then the ship is placed on the sea floor with minimum depth of 16m. Ball-typed reef

Reef Balls have been developed over a period of 20 years and have a multitude of advantages over regular artificial reefs. Most importantly, Reef Balls are designed artificial reefs, which mean they are specifically designed for individual project goals. many of the main features unique to Reef Balls such as stability rated for hurricanes and large wave climates, durability (lasting over 500 years), specialized features for enhancing the marine habitat they create such as a marine friendly concrete, specialized surface textures for better colonization, holes that are shaped to create whirlpools to provide better water circulation, protective void spacing (areas where fish and other free swimming marine life can shelter from currents), variable light regimes (surfaces that face every possible direction to the given sunlight to provide a wider biodiversity in that just like a forest is more diverse when it has both high light and low light areas that is also true for reefs).

2.8.3 Tukun in Kelantan

For the state of Kelantan during the Rancangan Malaysia Kesembilan dan Kesepuluh (2006-2013) period, the Kelantan Fisheries Department allocated RM 2.5 million for the construction of artificial reefs under the provisions of the Pakej Rangsangan Ekonomi Kedua (PRE) and Peruntukan Pembangunan Tukun Tiruan. This provision has been used to develop the base of the reefs as follows:

i. White Sand District (Pachakan) – 1 site
ii. Tumpat District (Kuala Tumpat) – 2 sites
iii. District of Kota Bharu (Kuala Besar) – 2 sites
iv. District of Kota Bharu (Kuala Sabak) – 1 site
v. Bachok District (Kuala Kemasin) – 2 sites
vi. Bachok District (Irama Beach) – 1 site

The types of reefs built are Tukun Tetrapod, Tukun Dasar Lembut, Tukun Dasar Lembut Penghalang Pukat Tunda dan Tukun Rekreasi. These artificial turbines are built with 40-50 concrete grade that lasts for 50 years in the sea.

The design of artificial reef will form a current movement that pushes nutrient-rich seawater and creates a ‘upwelling’ phenomenon. This will make the site of the reefs rich in plankton and the focus of a small pelagic fish. This small pelagic fish will attract the attention of large fish like mackerel to be near the reef..
The construction of the reef will benefit the existing fishermen’s association including the local fishing communities and establishments created by the Fisheries Department, especially Fisheries Volunteer (SUPER) and the Fisheries Ecosystem Community (KEP).

Number of Kelantan Fishermen – 9,300 people
Number of Kelantan Coasters – 4,200 people
Number of Kota Bharu District Fishermen – 1,300 people
Number of Kota Bharu District Beach Fishermen – 1,000 people
Number of Fisheries / Traditional Fisheries of Kota Bharu – 700 people

The Artificial Program is for the benefit of the fishermen in general, taking into account the views of fisheries and fisheries issues in particular in the state to ensure that this sector remains beneficial and provides good economic returns and job opportunities to the people of this state. All fishermen in the state always receive and support all fish conservation efforts undertaken by the department to ensure the sustainability of fisheries resources in the present and future.

In this current development phase, Kelantan fishing fishermen will become modern fishermen in terms of fishing methods, organizational management includes new ways of thinking. Fishermen should not place fishermen’s livelihoods for example just using traditional equipment instead of using modern technology and engaging in various branches of economic activity including promoting recreational fishery activities as a new economic source for fishermen. Various technology and advisory services as well as training can be obtained from the Department of Fisheries Malaysia and other related agencies.

Figure 2.3The Deployment of Ship-Type Artificial Reef in Pasir Puteh, Kelantan

Figure 2.3 above explains that artificial tussle from boats is more economical and effective in promoting fish breeding outside the state Marine Park area. The artificial reef also reduced the case of fishermen invasion to the Marine Park area. NMP provided many artificial reefs outside Marine Park area throughout the country through the Alternative Living program by allocating RM200,000 to provide artificial reefs around 42 Marine Parks nationwide and built concrete, concrete and plastic reefs but it turns out the reefs of wood boats are cheaper and what is important is more appropriate to promote fish breeding. Reefs parked outside the Marine Park area, two miles (nautical miles) (3.6 kilometers) from the island also helped local fishermen. Seven boats were disposed of at only RM50,000 around the waters of Tok Bali. The success of creating many artificial reefs outside the Marine Park has led the tourism industry in the islands to become increasingly lucrative, thereby benefiting tourists and chalet. Before being sunk, the boat is cleaned so that it is free from the effects of oil that can affect the environment.
2.9 Multi beam sonar

A multi beam sonar is an instrument that can map more than one location on the ocean floor with a single ping and with higher resolution than those of conventional echo sounders. The bottom locations are arranged such that they map a contiguous area of the bottom. This area is a called swath. The dimensions of the swath in the accrosstrack or athworship direction (perpendicular to the path of the ship) is called the swath width, and it can be measured either as a fixed angle or as a physical size that changes with depth.

2.10 Advantages of using MBES for artificial reef detection

Multi beam echo sounder advantages make it the best choice to obtain full coverage, high resolution, high accuracy and high efficiency. These instruments have been widely used in various fields, including investigations of the continental shelves and Exclusive Economic Zone, offshore-cable route survey, submarine-pipe detection, seabed topographic monitoring, submarine-object detection and not to be forgotten the detection and mapping of artificial reefs. Sometimes it is necessary to monitor changes in seabed topography. With their full coverage, high resolution and high accuracy, multi beam echo sounder have been widely used in this kind of field. Comparison, analysis and study of two maps yielded important conclusions.

Multi beam echo sounder can be mounted on many types of survey platforms; including tow fish, ship hulls and remotely operated vehicle(ROVs). Among the existing acoustical mapping systems, multi beam echo sounder are currently the main focus of attention because of its ability to provide both a bathymetric map and a backscatter image of the surveyed area. The purpose of a large-scale bathymetric survey is to produce accurate depths measurements for many neighboring points on the sea floor such that an accurate picture of the geography of the bottom can be established. To do this efficiently, two things are required of the sonar used: it must produce accurate depth measurements that correspond to well-defined locations on the sea floor; and it must be able to make large numbers of these measurements in a reasonable amount of time.

Multi beam sonar can map complete swaths of the bottom in roughly the time it takes for the echo to return from the farthest angle. As a consequence, multi beam sonars are the survey instrument of choice in most mapping applications, particularly in deep ocean environments where ship operating time is expensive.

2.11 Models of multibeam

Table 2 4 Moedel of Multibeam Echo Sounder

Model Frequency
(kHz) Min/max depth (m) Max swath width Available configuration
M3 Sonar 500 kHz 0.2 – 50 120 degrees 500m and 4000m depth ratings, Ethernet, Ethernet with sync, Ethernet with VDSL and auxiliary port.
GeoSwath 4R 125, 250, 500 0.3 – 200
0.3 – 100
0.3 – 50 12xD
195m Available configuration
125, 250, 500 kHz
GeoSwath 4 125, 250, 500 0.3 – 200
0.3 – 100
0.3 – 50 12xD
195m Available configuration
125, 250, 500 kHz
EM2040C 200 – 400 0.5 – 490 Single head
4.3Xd/ 525m/ 130 degrees
Dual head
10XD/ 625m/ 200 degrees
Single and dual head
EM 2040P 200 – 400 0.5 – 550
EM 2040 200 – 400 0.5 – 600 Single RX:
5.5xD / 800m /
140 degrees
Dual RX:
10xD / 900m /
200 degrees 0.4x 0.7
Single and dual RX conf. for increased swath and with single and dual swath capability for increased seafloor coverage
EM712 RD 40 – 100 3 – 600 5.5xD / 1300 m /
140 degrees *1×2,2×2
*Short CW transmit pulses
EM 712 S 40 – 100 3 –1800 5.5xD / 2800 m /
140 degrees *0.5×0,5, 0,5×1, 1×1, 1×2,2×2
*CW transmit pulses
EM 712 40 – 100 3 – 3600 5.5xD / 4200 m /
140 degrees *0.5×0,5, 0,5×1, 1×1, 1×2,2×2
*CW and FM transmit pulse
30 10 – 7000 5.5xD / 8000 m/
143 degrees *0.5×1, 1×1, 1×2, 2×2, 2×4 and 4×4
*Other customer specific conf. available on request
EM 122 12 20 – 11000 6xD/35000 m /
143 degrees *0.5×1, 1×1, 1×2, 2×2 and 2×4
*Other customer specific conf. available on request
*Estimated depth and coverage for EM 712, based on BS= -20dB, NL=35 dB, f= 40 kHZ

All product range includes models for all water depths and virtually any application. The benefits of multibeam echo sounders are that they map the seafloor by a fan of narrow acoustic beams, thus providing 100% coverage of the bottom. The resulting seabed maps are more detailed than those obtained using single-beam mapping. The maps are also produced faster, reducing your ship survey time. For a complete mapping system, the multibeam echo sounders are connected to positioning equipment, heading and motion sensing instruments, as well as sound velocity sensors in order to position the soundings correctly. Most of the multibeam echo sounders are operated from a graphic display workstation. Real-time software includes extensive tools for visualizing the sounding data as well as the seabed image data, and to check the system calibration and the data quality. Preliminary maps can be produced and plotted almost immediately after a survey is finished. Post-processing software for cleaning and correcting of multibeam sounding data is offered, as well as tools for producing seabed image mosaics and classification of the seabed sediment types.



3.1 Introduction

This chapter reviews some of the methods developed for multi beam data cleaning. A summary is presented highlighting some of the features for each method. Finally, procedures for the method by using Qimera software. The data acquired by multi beam echo sounder systems needs to be processed and validated.

The requirements for data cleaning depend on the purpose of the basic data product. In this study, the basic data product is a bathymetry data set. The objective of the bathymetry data set is to have information about the seafloor bathymetry and to preserve information about the features especially artificial reef in Tumpat, Kelantan. To achieve this goal, data cleaning must reject the soundings corresponding to gross errors (blunders) systematic errors and to assess the noise level. Herein swath mode is used to refer to a single swath and subset mode to refer to an area covered by several lines.

3.2 Study Area

The area of this study area is located near with Tumpat, Kelantan. The coordinate is obtained during data acquisition which is 6.1991° N, 102.1694° E. The method used to obtain the data is by using the application of multibeam. This method is used to show how much the capability of the multibeam can detect the artificial reef in the seabed.

Figure 3 1 Location of Survey Area in Tumpat, Kelantan
3.3 Flow Chart

Figure 3 2 Flow Chart of Data Processing?
3.3.1 Data acquisition

Raw data is obtained from the previous year of data collection at the island near Tumpat area. The data was collected using the multibeam method. To perform this important task of analyzing and cleaning the multibeam data set, it is important to define procedures. These procedures are important to give the orientation required for comprehensible and uniform methodologies to safely and efficiently accomplish the task of cleaning the data set for hydrographic charts. The result will be a cleaned data set available to be integrated in the nautical chart. The main interest of the following procedures is blunder detection. However, there are further steps that cannot be forgotten, and are included mainly to put blunder detection into context. There are two sources of errors in the MBES measurements: systematic errors, blunders. Systematic errors should be analyzed before the survey by the calibration test, also named patch test.
Survey is conducted at Tumpat, Kelantan with the estimated coordinate 6.1991° N, 102.1694° E. the survey is carried out in year 2016 by UMT students. Data is obtained by using the multibeam echo sounder sonar. Data is taken on August 19th 2016.

3.3.2 Patch test

The first step of multibeam data processing is to check the positioning, looking for jumps in the coordinates and sudden variations of heading. Roll, pitch, heave need to be checked and sudden variations should be browsed to check for biases in the depth data set. The hydrographer needs to judge when to interpolate or to reject some of the positions or attitude values.


Figure 3 3 Patch Test Using Roll Method

Figure 3.3 above shows the first method need to be applied for the patch test calibration. The roll test uses two lines of data, run in opposite directions with the same vessel speed over the same ground (need to overlap as much as possible). An area of flat seabed is best for this test.


Figure 3 4 Patch Test Using Pitch Method

Figure 3.4 above shows the second method after applying roll method. The pitch test uses two lines of data in opposite directions with the same vessel speed over the ground. A seabed with defined targets or is sloped (along track) is best for this test.

Figure 3 5 Patch Test Using Heading Method

Figure 3.5 above shows the heading test uses two parallel lines of data that were run in the same direction with the same vessel speed. These lines are spaced apart by about half a swath width or a little less. There must be an area with slope (along track) or a defined target in the area of overlap.

3.3.4 Static Surface

After known systematic errors had been corrected, there still remain some systematic errors (mainly due to sound velocity profile variations), gross errors or blunders and noise. For this purpose, one can derive color coded contours to look for irregularities in the image. The areas with irregularities need to be identified and kept separately. In this study high standard deviations are associated with irregular seafloor areas, and low standard deviations are associated with regular seafloor areas. The mean surface also provides information to define the irregular areas, areas with large variations in the bathymetry, and regular areas (bathymetry featureless areas). The acoustic backscatter image is used to identify these areas, in a general way, irregular areas correspond to high backscatter areas (correlated with rock), and regular areas correspond to low backscatter areas (correlated with mud and sand).

Figure 3 6 Comparison of Data Before and After Applying Static Surface Tools

Figure 3.6 shows that the bathymetry lines appear to be more smooth and clear after applying static surface tools. The area with artificial reef is not clearly shown before applying the tools.

3.3.5 Dynamic Surface

Qimera’s Dynamic Workflow engine works by taking advantage of the dependencies between raw measurements, processed soundings and derivative products. If a raw measurement is altered, or perhaps a processing configuration is changed, the engine can easily establish which set of processed soundings must be updated, it will establish exactly what type of re-processing must occur and also which derivative products must be updated.

3.3.6 Apply tide data

After the navigation, attitude, and tide have been validated, the data need to be reduced for the tide and the lines should be merged. All the following steps should be performed in the subset mode, i.e., by areas, allowing the analysis of the overlapping data of adjacent lines. The format for the tide data is in ASCII files. Tide data can be obtained from the National Hydrographic Centre as the Royal Malaysian Navy does not issue tide data anymore.

3.3.7 Sound Velocity Profile (SVP)

In order to achieve high quality bathymetric data, detailed sound speed information of the water column is needed. The MBES data has systematic errors, which are, in a general sense, the result of remaining system offsets mainly roll, and sound velocity profile (SVP) errors and they play the most important role in the depth measurement uncertainty. The determination of these calibration values are done before the survey. However, if one has survey lines run in the direct and reverse senses, measuring the depth difference between the outer beams from the two reciprocal lines one will be able to check the configuration determined during the patch test. SVP errors are measured on the inner beams from one line with the outer beams from a line run perpendicularly to the main survey line. To accomplish this task, lines run in reciprocal senses and check lines, the number of lines depends on the dimensions of the surveying area. The SVP errors result from the variation of the SVP between samples. The Sound Velocity Profile need to be checked for the effect of the refraction and to define the angular coverage, where the effect is not higher than the depth measurement accuracy specified by the International Hydrographic Organization standards. The results of any remaining systematic errors are reapplied and the data transformed to generate the corrected final sounding positions and depths.

3.3.8 Reject beams outside the accuracy

The swath that does not cover the artificial reef area can be remove from the dataset to ease the filtering and cleaning process. The data will be more specific to the area with artificial reef.

3.3.9 Filtering

Filtering is conducted using swath editor by applying on the whole of the bathymetry line. From this application, the bathymetry line will appear more smooth as the blunders have been slightly removed.

3.3.10 Cleaning

Cleaning is conducted onto this dataset after calibration, filtering and applying all the related data required. Cleaning is conducted to ensure the excess noise made by the habitat lives in the seabed is reduce. Removal of the noise is impossible; thus the noises just can be reduced to make the dataset smooth for the visualization and easy to be interpreted for research purposes. All existing data cleaning methods are based on depth data redundancy. Redundancy can be achieved by having plain overlap or overlapping beam footprints within one swath; by running the vessel slowly enough, or the MBES ping rate is fast enough, so that ping-to-ping swaths overlap; and/or by running cross-check survey lines perpendicular to the main survey lines. Before sounding data points can be analyzed and cleaned, it is necessary to check the ancillary data from each sensor (roll, pitch, heave), to detect spikes on these measurements. These inaccurate measurements should be rejected and interpolated with the adjacent measurements. Only afterward can the depth data set be clean from gross and systematic errors.

The soundings can be analyzed swath by swath (swath mode) or by areas covered by several swaths (subset mode). The sources of information available to aid the hydrographer in the data cleaning task are:
I. Soundings in the swath mode
• comparison with soundings corresponding to bottom detection for consecutive pings;
• comparison with soundings corresponding to bottom detection for adjacent beams in
the same ping;
II. Soundings in the subset mode
• comparison with soundings corresponding to the neighboring bottom detections (same
or different swaths);

3.3.11 Analysis of bathymetry map

The acoustic image should be used to correlate the targets with the bathymetric features, which is an efficient method to identify real features. If the irregularities in the data set are caused by blunders, they must be rejected from the data set and the remaining dataset should be analyzed as a regular area.
From the bathymetry map, it shows the capability of the multibeam sonar in detecting features on the sea floor even though there might be several parameters of characteristics that need to be taken from conducting the survey. The map shows that the average depth of the artificial that lies in the area is 12. 596m.


4.1 Introduction

This chapter review about the final output produced after the processing of raw data is complete. Map is produced to show the mapping area and to prove that this method is suitable for mapping seabed features. From the product, the data can be used in another places according to its purposes. This shows that the output produced is flexible to be used. Besides, apart from acquiring seafloor topographic data, seabed characterization can also be implemented using angular backscatter data. Such a classification technique for the seafloor sections involves the shape, variance, and magnitude of the angular response of the measured multibeam angular backscatter strength and is applied in this study. However, a careful selection of seafloor segments is necessary to provide the entire angle range of backscatter data within the segments. If the seafloor properties vary within a very small area, the full angular coverage may not be available for analyses due to the swath coverage.
4.2 Result

Figure 4.1 Result of Artificial Reef Detection Using The Method of Multibeam Sonar

4.3 Analysis

The result above shows that the application of multibeam to feature the seabed habitat which is artificial reef. The artificial reef can be detected as the swath used during data acquisition is in a full coverage. Thus, the bathymetry line that overlapped would cover the artificial reef area. From the result shown above, the image of the artificial reef lies on a flat seabed and have minimum slope area.
The application of multibeam is used because the conformance of the available equipment is more accurate and could provide better visual coverage of the features on the seabed. Satellite is not really suitable to be used as it has certain limitation of penetration of the sea water. Mostly, the artificial reef is constructs with the depth where the satellite cannot pass through the sea water to detect it. Thus, multibeam is considered as the best method to map the seabed features where it is not only cost saving but also time saver and provider higher accuracy.
Multibeam sonar can be various in reaching certain depth of the seabed. Sometimes it can reach down to 3600m and it depends with the type of the multibeam used and its purposes. It shows that the artificial reef in Tumpat lies on the seabed with the maximum average depth of 12.596m below.
Regular areas are defined by their low and uniform surface. Sloping surfaces can be considered irregular surfaces, since they do present high local variation of the backscatter strength. The errors in these dataset are spurious blunders, remaining systematic errors, and noise and in this phase the data set is only cleaned of known errors. This dataset can be processed automatically and it is important to keep in mind that during the survey, there must be at least one beam meeting the survey accuracy measurement specifications.

Irregularities area, defined either as areas with high standard deviation or areas with large variation of backscatter strength or rocky areas, need to be interactively analyzed, using the visualization tools that produce profiles. In the second case, it is necessary to choose a meaningful correlation. Low standard deviation areas do not mean an area free from blunders. This is highly dependent on the number of soundings per cell, i.e., a large number of soundings with a blunder will have a lower standard. These surfaces provide further detail to investigate blunders, they are efficient and can be used complementary to the standard deviation and mean surfaces. When cleaning the data interactively the hydrographer must use the surfaces of the standard deviation, maximum residual difference, and depth to check the irregular areas and look for noises in order to identify and reduce them.

Large features on the seafloor like tukun, will be detected by several beams. These features will be highlighted on the acoustical image due to the contrast of seafloor properties, steep slopes, or shadow.



5.1 Introduction

This chapter reviews the final results obtained from all the data acquisition until map production and after the objectives are achieved. All the recommendation for industrial training and projects can be added to help improvised this whole report. After all the analysis has been explained, the conclusion can be made so that the method used in this project can be determined either it is suitable or not for mapping other features that lies on the seafloor.

5.2 Conclusion

In this work, analyses of the multibeam angular backscatter data acquired in the Tumpat area are carried out. Processing of the angular backscatter data using the Qimera software is made for one location to map the distributions of artificial reef in Tumpat. A detailed methodology is developed to produce angle-invariant (normalized) backscatter maps to clarify different depth of seafloor from the sea surface. Such a presentation has advantages above the raw angular backscatter data since the impact of the incidence angle is removed. A qualitative analysis of the calculated mean backscatter values i.e. gray scale levels, utilizing angle-invariant backscatter data generally indicates that backscatter values are highest (lighter gray scale) from the seafloor. However, mound-related backscatter patterns only exist within the depth range of the mounds which is the height from top of the artificial reef. Contour currents are also supported by the backscatter data. The backscatter values are the lowest from the inter-channel areas (lowest gray scale level). Various factors of the mean backscatter response are also the highest for the mound areas where the artificial reef lies. This indicates higher seafloor roughness compared to the surrounding sediments. The location of buried artificial reef area are the highest in slope value. Meanwhile, moderate seafloor backscatter presents lowest slope and values.
However, the presently produced imagery provides good information for marine science because it also shows the degree of variability in terms of acoustic sediment properties. The technique developed is essentially applicable for geological interpretation, because changing sediment properties can be related to areas of different seafloor facies. The extent and variety of the seafloor features gives an indication for the geological interpretation of the upper part of the seafloor sediments and its spatial validity.

5.2.1 Applicability and advantage of multibeam sonar method

Seafloor features were distinguished in this study based on multibeam bathymetry and backscatter data. The areas of overlapping morphological and backscatter segments indicate locations that require additional detailed investigations. The scale of separated segments based on backscatter and morphology variation depends on the quantity of measurements and ranges from sizes smaller than the multibeam swath to areas that extent across the entire survey area.
Ship-borne multibeam surveys are one of a remote sensing tool and capable to cover large areas in comparatively short time. Limits of the spatial resolution of the presented multibeam data exist due to the distance of the hull mounted system from the seafloor. The application of multibeam angular backscatter data enables the user to define seabed facies of different acoustic properties. Angle invariant backscatter data serve as indicator for different acoustic features due to the relation of backscatter and sediment characteristics, multibeam backscatter data provide a useful tool for seabed classification.
The backscatter data provide first information for geological interpretations of the seabed in addition to bathymetry and sub-bottom profiles. Sampling sites selected basically on the acoustic segmentation (e.g. for sediment samples, video observation) then provide information on the characteristics of the seafloor features. Segments of the channels in Tumpat showed that the backscatter data is sensitive to variations of the sediment surface. Ground truth for backscatter data is important in these regions and the source of the backscatter variation is difficult to reveal with geological surface samples.

5.3 Recommendation

5.3.1 Recommendation for project

The results of this study were derived from the analysis of multibeam bathymetry and angular backscatter data obtained from the ground truth which is carried on in year 2016. Not all obstacles that were detected could be solved within of this thesis. In particular, issues regarding the spatial resolution, ground truth and technical aspects of the backscatter data need to be solved and form the outline of the future perspective. Spatial resolution

The target areas of this study are characterized by a small spatial extension. Limits of the application of hull mounted multibeam systems are generated by their spatial resolution and frequency. Remote sensing technique are the best technique for enhancement of resolution where it needs to come closer to the target, for example by towed systems or by deploying remotely operated vehicles (e.g. Huvenne et al., 2005; Klages et al., 2004; Edy et al.2004a). However, the deployment cost is much higher and consuming time. Investigations based on video observations provide the highest resolution of non-destructive in situ observations. Ground truth for angular backscatter data

Ground truth is necessary to verify the detection of the artificial reef. A systematic inventory of seabed depth and their acoustic properties is recommended to support rough scale interpretations at unknown sites prior to further sampling. This should also consider the different levels of resolution of seabed samples and the multibeam lines.

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