Design and Development of an Underwater Explosion Detection Robot for Monitoring Dynamite Fishing in the Philippines

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Blast fishing is a big problem around the world. It damages ecosystems and destroys underwater habitats. CBobby is an underwater explosion detecting robot to detect blast fishing activity and triangulate the location to inform the local authorities. It analyzes the audio spectrum and transient properties of acoustic events to detect explosions. It is an open-source platform, made with off the shelf components to make it cheap, easily replaceable and repairable. The device will be camouflaged as a stonefish to attract less attention. It uses hardware processing to reduce power consumption. At the current stage of development, it can distinguish simulated blast fishing activity from background noises. In the Philippines, around 583,000 people are fishermen among them at least 70,000 practice blast fishing. Blast fishing is also affecting their economy. Working with Development Alternatives Inc (DAI), the plan is to deploy it in the Philippines to prevent illegal blast fishing activity.

Every year more than 179 million tons of fish are being produced and 156 million tons of that production is used for human consumption. In one way or another, a large portion of the human population is reliant on the fishing industry [1]. To meet the demand of the ever-growing population, several methods have been utilized to catch fish shoal and the school of fishes. One of the most detrimental ways of catching these shoaling fishes is blast fishing.

Blast fishing ensures a large harvest but at the cost of degradation of the underwater habitat. Even though for the fishermen the target is the large fishes, this process also kills the small fishes and marine species [2,3,4,7,6]. This destruction of underwater habitat and marine lifeform leads to the extinction of many species and coral habitat.

Many countries have already made blast fishing illegal but the ease of available materials to produce explosives, lack of proper regulation, and most importantly basic needs and poverty has made it difficult to control this illegal fishing method [5-8]. Due to the destructive nature of this fishing method, hundreds of years of coral growth is being diminished in seconds. As a result, fishes and other animals are losing the habitat, fish eggs and larvae are dying and the underwater ecosystem is losing their natural feeding and mating environment. It is a very negative impact also in the sense that in future there will not be enough food and habitat for the fishes to reproduce and eventually that will lead to more drastic methods of fishing until there is no place to fish anymore and that will happen very quickly if we do not take any measures soon [2,4].

When an explosion occurs, a pressure wave passes through the sea, within a few meters of the area the strength of the shock wave is very high and within this radius, it kills most of the living creatures. The fishermen normally target the school of fishes, the shockwave of the explosion ruptures the swim bladder along with damaging the other internal organs. The dead and injured fishes either floats on the surface or sink to the bottom of the reef [2-4] and become easy prey to the fishermen.

This method of destructive fishing is not only harmful to the underwater habitat but also for the people whose life revolves around it. Excessive fishing in one area will essentially lead to the decline of the growth of new fishes and eventually, that will cause lots of fishermen to lose their jobs. The Fishermen using their homemade explosives also suffer from the lack of knowledge of preparing explosives property, often they lose their limbs due to the unsafe handling process of explosives [9-11]. The chemicals used in these explosives are making the water more polluted and that leads to various health issues. That is certainly creating a negative impact on tourism and ultimately that is affecting the economy [3,6].

Blast fishing or dynamite fishing has been going on for decades. North Korea, Hong Kong, Malaysia, Japan, USA, Papua New Guinea, Philippines, Palau, etc. countries have reported the event of blast fishing as early as 1900. During and after world war I and II, soldiers inspired local habitants to use explosives to catch fish and after the war ended, the local people used the abundant leftover explosives to catch fish and also educated themselves to make their version of explosives [5,6]. Mixed fertilizer with kerosene or diesel essentially creates ammonium nitrate, a very easy to prepare explosive. Plastic bottle, waterproof fuse, and cheap detonator, everything all together cost around the US $3, which can be earned back with only 10 minutes of fishing [14-16]. Acoustic data collected from one research shows that, only in Tanzanian’s coastal area, daily 318 confirmed blasts occurred within 31 days in March and April 2015 [7]. Around 70 million people’s livelihoods are married to the coastal area of the Philippines. The country’s coastline shapes around 18,000 km and coastal...

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RAR Archive - 31.42 kB - 10/06/2020 at 12:57



Circuit Diagram and Code

RAR Archive - 191.21 kB - 08/30/2020 at 20:24


  • Combined MotherBoard and DaughterBoard Schematic

    ifthekhar ahammad10/06/2020 at 10:03 0 comments

    To minimize the size of the design a new schematic was prepared to combine the MotherBoard and DaughterBoard  but it still have not been produced because later on the Buffer section of the design was needed to be added and also for the final design, the prototyping features are also needed to be removed form the PCB. But this can be used to create the BOM of the current design (MotherBoard and DaughterBoard).

  • Demonstration Video

    ifthekhar ahammad10/06/2020 at 02:44 0 comments

  • Datalogger Schematic

    ifthekhar ahammad10/06/2020 at 02:35 0 comments

  • Buffer Circuit Schematic

    ifthekhar ahammad10/06/2020 at 02:34 0 comments

  • Buffer Circuit

    ifthekhar ahammad10/06/2020 at 02:32 0 comments

    During the initial test of the device, some variables had to be changed. For the field test, three
    identical devices were made and due to that reason, two new hydrophones were needed as
    well. After recording data with each hydrophone (9 meters long cable) with all three devices,
    no noticeable loss of performance was observed. At one stage a decision was made to increase
    the length of each hydrophone cable and one important property was overlooked, the new
    cable that was used was made of few different materials and also had a thin layer of tissue
    paper in between the jacket and the cables. That may have added some additional pyro-electric
    activity and after connecting them to the existing cables, CBobby has recorded higher
    noise activity. Based on the current perspective the added length (extra 30 meters to each
    hydrophone cable) or the property of cable or both can be the reason for that noise activity.

    To verify the detection ability and to monitor & record the acoustic activity, a Zoom H2a
    recorder was also connected in parallel with the CBobby. Now the observed data from the
    hydrophone was sent to both the H2a recorder and CBobby simultaneously. It
    resulted in a lot of noise generation on both the recorder and the CBobby end. It also
    dramatically reduces the amplitude of the received signal.
    One reason for this is the crosstalk between the recorder and the CBobby and another reason
    is the impedance mismatch. To solve the impedance match issue, An Operational Amplifier
    based stereo buffer/Amplifier circuit has been implemented in the system separately. Where either the buffer or the amplifier circuit or both in conjunction can be used to
    stabilize the microphone signal. But that approach did not solve the problem completely.

  • The Datalogger

    ifthekhar ahammad10/06/2020 at 02:28 0 comments

    A custom datalogger was designed to record the data collected from the CBobby. The
    datalogger was designed to verify the explosion detection ability of CBobby for long-term
    (24- hours or more) operation. It will verify the data by comparing its recorded data with the
    Zoom H2a audio recorder data. The data from the Daughterboard was sent to the datalogger
    through serial communication protocol with a baud rate of 9600. This data consists of the
    frequency band detections and the transient event detection pulses. To verify the data collected
    from the data logger, an audio recorder was also connected with the microphone of the
    CBobby. The datalogger and the recorder were synchronized by pulling up the transient
    detector line and the microphone’s bias line high (after DC blocking capacitor) for a short
    time or by creating a continuous loud noise for a couple of times (Clapping).
    The datalogger has an I2C protocol based IMU (GY-80) and an LCD, SPI protocol-based
    Memory (MicroSD card), and Real-time clock, and UART Serial communication-based GPS
    module (Figure 7,8). The Arduino of the Daughter Board sends its data through the UART
    based serial communication protocol to the virtual UART serial communicator of the
    Datalogger. And the hardware-based UART communicator of the datalogger is connected to
    the GPS module.
    Due to this reason, while programming the datalogger’s
    microcontroller, the GPS module is needed to be disconnected

  • Calibration outcome

    ifthekhar ahammad10/06/2020 at 02:22 0 comments

    Calibration outcome of a single channel: 

    Figure 25: Signal processing of one of the frequency bands (After Pre-Amplification and filter section (yellow), Amplification stage (green), BWPC stage (blue) and LLC stage (magenta))


  • Primary calibration

    ifthekhar ahammad10/06/2020 at 02:18 0 comments

    The environmental condition of different locations will be different and based on the shallowness of water, underwater habitat, water temperature and distance from the explosion, etc., the calibration of the device will change but for the primary test condition the whole system will have a fixed sets of parameter and only the gain of the pre-amplifier will vary (motherboard), and this method of calibration will be put on to the trial at the actual field test. So, to achieve this single variable-based calibration process, the following steps were taken:

    1. From the function generator, the amplitude of the test signal (sinusoidal wave) has been set to 100mVp
    2. Set the Pre-Amplifier output to 1V
    3. Set all the amplifiers (only for ASA) output to 2V
    4. Set all the LLC’s threshold voltage to 600mV (Positive level detector, threshold value)

  • DaughterBoard ​PCB

    ifthekhar ahammad10/06/2020 at 02:13 0 comments

    The DaughterBoard pcb was prepared. 

  • DaughterBoard ​Schematic

    ifthekhar ahammad10/06/2020 at 02:09 0 comments

    When the DaughterBoard Prototype was performing properly the proper schematic of the DaughterBoard was prepared with all the necessary prototyping features such as arduino connection and indicator LEDs

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Jon wrote 09/05/2020 at 17:17 point

Thanks, first and foremost, for bringing attention to the threat presented by blast fishing. Good luck!

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ifthekhar ahammad wrote 10/06/2020 at 02:10 point

Thank you

  Are you sure? yes | no

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