Yacht News

Tuna Purse Seine Vessel Bridge System & Electronic Equipment

May 8th, 2010 molitva leyli

Tuna Purse Seine Vessel Bridge System & Electronic Equipment;  Sonar, Radio buoys, Remote sensing, Communications and navigation, Navigational and Bird RADAR, monitoring Water column.

Integrated bridge system for purse seiner

1. Communications and navigation

Advances in ship to ship and ship to shore communications have been rapidly incorporated intofishing operations, improving basic efficiency and information sharing. Inmarsat systems, email and satellite phones have eliminated the need to code transmissions and provide economical, secure links between vessels and their management. Observers should be aware of the range of possible communication systems now available aside from radios.

GPS chart plotters have also greatly simplified navigation, documenting waypoints, fishing events and keeping track of FADs and other vessels. GPS technology has been integrated into radar and sonar systems to allow real time, relative positioning and movement data to the fishing captain.

2. Navigational and Bird RADAR

The presence of seabirds in the open ocean areas of the WCPO is a sure sign of baitfish and tuna, with dense seabird concentrations often indicating surface concentrations of tuna or the proximity of floating objects. S-Band, or Bird Radar is capable of detecting birds and bird flocks at considerable distances, even through rain and clouds that visually obscure the birds from a vessel. Most modern tuna purse seine vessels have adopted bird radar as a basic component of their searching/fishing strategy and in many cases have eliminated the searching helicopter and some visual searching in favor of radar monitoring. Observers should be aware of the basic difference between S-Band bird radar and X-Band navigational radar.

As an example, Figure 1 shows a high end bird radar, the Furuno5 FR-1760DS. The unit has a ratedrange of 120 nautical miles, 60 kW output on a bright 17” color CRT display. Integration with the vessel GPS allows head up or relative tracking of targets, which greatly assists when pursuing and setting on unassociated schools of tuna. In addition to birds, this unit has been optimized for detection of small ships, buoys and net floats. This is likely in response to the desires of purse seine fishermen to actively search for and utilize drifting FADs belonging to other vessels. Observers should be aware that radar units may resemble a computer more than the traditional CRT radar display. Figure 2 shows the Furuno FR 2165DSBB, 60 kW, 120 nmi range S-Band bird radar. These fully computerized units can utilize sophisticated chart plotting software to monitor multiple targets and the display can easily be distributed over onboard televisions or multiple LCD displays.

Figure 1. CRT display S-Band bird radarunit (Furuno).

Figure 2. Modern S-Band bird radar with LCD display (Furuno).

Navigational radars have also continued to develop and are no longer used only for vessel navigation. Purse seine and supply vessels now utilize highly tuned X-Band navigational radar to actively search and locate drifting FADs belonging to other vessels, which may be set upon and marked with their own radio buoys. The loading coils on the antennae of older style radio direction finding (RDF) buoys can be detected by high-end navigational radars. Many purse seine vessels actively scan for foreign buoys and associated FADs as they transit to their own FADs or during normal searching activities.

Also, the new generation of navigational radars are equipped with sophisticated target acquisition and tracking software. Purse seine vessels now use their navigational radars as a fishing tool, to simultaneously track the position and course of multiple vessels. This is particularly useful when maneuvering in an area of school fish with many seiners engaged in searching and fishing operations. Foreign vessels can also be monitored to detect FAD associated behavior. Figure 3 shows a state of the art navigational radar with 28” color CRT display, 120 nmi range capable of acquiring and tracking 40 targets.

Figure 3. Modern X-Band navigational radar with 28” CRT display (Furuno).

3. Water column monitoring

Most modern tuna purse seine vessels are equipped with Doppler current meters to monitor surface and sub-surface currents prior to and during fishing operations. A typical unit, suc h as the one pictured in Figure 4 will provide a constant readout of the speed and direction of the water column at three programmable depths.

There are a number of sounding units that monitor the actual depth of the net, such as the one pictured in Figure 5. Net depth is displayed from up to three sensors in large digits or simple graphics on the display screen. Transponders are usually attached to the chainline at different areas of the net which allow the vessel to monitor actual net depth during the pursing operation. Pursing depth can be increased if necessary by slowing the purse winch, which is not uncommon on early morning FAD and log sets.

Vertical temperature profiles have not been considered useful for purse seining in the WCPO, hence the lack of bathythermograph recording instruments. Much of this data is now available via remote sensing, monitoring buoys and websites.

Fig 4. Doppler current meter (Furuno).

Fig 5. Purse seine net depth monitoring system (Furuno)

4. Depth sounders

Purse seine vessels and their auxiliary craft utilize depth sounders to enhance their ability to discern the school size, species and depth distribution of tuna schools found in association with drifting objects. Small tow boats or work boats may be equipped with a simple depth sounder and radio to relay information on the location and depth of the school to the main vessel during a set or when investigating a FAD. More sophisticated telesounders transmit the sounding image from an auxiliary craft to the mothership, and are common on Japanese vessels.

New generation scientific sounders, such as the Simrad ES60 pictured in Figure 6 add new dimensions to echo location and are being increasingly used on modern purse seine vessels. These fully configurable units operate in the Windows NT environment and allow storage and

Figure 6. Simrad ES 60 scientific echo sounder (Simrad).

playback of data. Up to four frequencies can be displayed simultaneously with separate gain controls for fish, schools and bottom. With experience, the school size, species and size of fish in a school can be assessed with a high degree of accuracy.

5. Sonar

Modern tuna purse seiners often have two or three sonar units operating at low and high frequency and at different range settings for short and long range detection and school assessment. Bridge personnel often monitor sonar displays when on watch 24 hours a day for the presence of subsurface tuna concentrations. Of course, they are essential for school assessment and setting operations on logs and FADs when sets are made in pre-dawn darkness.

New generation low frequency, long range sonar units like the Simrad SP90 (Figure 7) are appearing on state of the art purse seiners that recognize their value to fishing success. This unit operates at 26 kHz with a maximum rated range of 8000 m and a rated detection

range of 3000 m. It is advertised specifically as a low frequency, long range tuna sonar. EU purse seine captains claim that these sonar units have been responsible for estimated increases in vessel productivity of 10% to 20% and note high success in species discrimination with sonar (Fonteneau, pers. comm..).

Figure 7. Simrad SP 90 low frequency long range tuna sonar (Simrad).

6. Radio buoys

The importance of radio buoy technology to modern purse seining can not be overemphasized. Developments of new types and features on transmitting buoy have allowed the fishery to develop hand in hand with technology, particularly in regard to fishing on drifting FADs.

6.1. Historical development

Early model radio buoys, that are still used in many fisheries, are always activated, transmitting an undisguised signal every few minutes detectable by an onboard radio detection finder (RDF). These devices were commonly used in the development phase of the WCPO purse seine fishery to mark logs and natural drifting objects. The range of detection is limited to less than 100 nmi, and generally less than 75 nmi with limited battery duration. These devices provide the vessel with only a crude bearing and their distance can only be estimated by signal strength. As the fishery developed, vessels began to capitalize on the open nature of the transmissions and actively scanned common RDF frequencies to locate and set upon logs belonging to other vessels. The transmitting frequency of these buoys could be easily changed, so theft of radio buoys was also a problem. However, it was the loss of logs and associated schools that drove the industry to demand more sophisticated technology. Constant transmit radio buoys were commonly used by WCPO purse seine fleets from the beginning of the fishery to around the mid 1980s 6 Select call radio buoys were quickly adopted in the 80s to reduce theft of gear and productive logs and FADs. A single drifting object can (over some time) fill up a purse seine vessel, so this is no small consideration. Select call, or ‘sel call’ buoys remain in a low power ‘sleep’ mode until a coded signal from the vessel activates the buoy for a short series of transmissions. The vessel can lock in on the direction of the buoy during the brief ‘wake up’ period and obtain a general range and bearing. Further developments raised the transmit frequency to improve detection of bearing to approximately 200 nmi (Morón, et al. 2001).

Figure 8 depicts the general characteristics and gear involved with constant transmit, select call and GPS positioning radio buoys.

Drifting FAD fishing increased significantly for the EU Indian Ocean fleets, and radar detection of radio buoys was becoming problematic. As noted in the previous section on navigational radar, the loading coils of RDF buoys can be detected by high grade radar units, thus allowing vessels to actively scan for the logs and FADs belonging to other vessels. In 1995, EU ve ssels began to incline their radio buoy antennas to reduce the detection range by other vessels (Morón, et al. 2001).

Figure 9 shows radio buoys with inclined antennae that are a standard feature of Indian Ocean purse seiners. However, it is not believed that this development has been widely adopted in the WCPO fishery.

In the late 1990s, GPS technology was incorporated into drifting radio buoys. GPS positioning buoys have revolutionized purse seine fishing and were quickly adopted by all modern fleets. These buoys combine a sel call feature with the ability to transmit the exact GPS position, allowing vessels to carefully plan their fishing campaigns. Interestingly, Morón (2001) notes that GPS buoys contributed to an expansion of the

Indian Ocean fishing grounds as vessels ventured further a field to retrieve lost radio buoys that had drifted out of traditional areas.

Figure 8. Early evolution of radio buoy technology (Ryokuseisha Corp.)

Figure 9. Inclined antennae on RDF buoys.

6.2. Recent developments in radio buoy technology

In the late 1990s, more sophisticated radio buoys became available, again revolutionizing modern purse seining. These GPS tracking buoys transmit continuous position data to a computer interface at ranges close to 1000 nmi. A continuous “worm trail” of the buoy is represented on the computer screen at all times. These buoys also transmit sst and battery condition with slim antennae without loading coil making them very difficult to detect by radar (Figure 10).

Figure 10. Serpe type GPS tracking radio buoys and computer interface (Martec).

The next development in transmitting buoys utilized Inmarsat technology to link the vessel to a low profile sonar buoy with no visible antennae (Figure 11). These buoys transmit GPS position, SST, battery life and sonar readings directly to computer displays on the vessel via satellite. With no antennae, the units are extremely difficult to detect by other vessels and have unlimited range. Also, a bright light can be triggered to flash and signal the vessel when it approaches the unit for FAD detection and retrieval.

Figure 11. Satellite linked sonar transmitting GPS buoy (Zunibal).

The latest generation radio buoys (2003) continue to improve in response to the needs and concerns of industry. GPS transmitting buoys have eliminated the need for antennae and taken a low profile shape, making them extremely difficult to detect visually or by radar. Computer transceivers and display units are now marketed in laptop computers to conserve space (Figure 12). Another significant improvement to sonar buoys has been the addition of solar panels, providing them with virtually unlimited autonomy and eliminating the battery concerns of earlier models. The solar

powered unit pictured in Figure 12 transmits via satellite a GPS position, battery state, as well as current speed and direction. Current velocity threshold alarms can be set that can notify the owner of unusual conditions. Excessively high speeds may indicate to the owner that his buoy is no longer in use but travelling at high speed onboard another vessel !

Figure 12. New generation GPS and sonar transmitting buoys (Martec, Zunibal).left solar powered sonar buoy, right low profile GPS buoy

The use of sonar transmitting buoys by purse seiners is a significant development for the industry. Earlier models often represented false hopes to the fishermen and were limited in scope of coverage below the buoy. However, with better technology and experience, sonar transmitting buoys have become very beneficial in maximizing “search” time, or the time spent traveling to and assessing FADs. Aretxe and Mosqueira (2003) examined catch composition and catch parameters for FADs marked by different types of radio buoys. While noting no difference in species compositions, the success rate and percent of larger sets appeared to be significantly higher on FADs equipped with sonar transmitting satellite buoys. This may indicate simply that these devices are efficient in predicting when good concentrations of tuna are present, thus avoiding unnecessary visits that unnecessarily occupy a vessels schedule. The primary manufacturer of satellite linked sonar buoys concluded a business arrangement in 2001 that permitted worldwide, and Pacific -wide coverage for these devices, thus opening up their full use to the WCPO.

REMOTE SENSING AND COMPUTERIZATION

There are a number of commercial services that provide satellite imagery to commercial fisheries. Purse seine fleets have made ample use of this technology to incorporate information in near real time of SST, currents, chlorophyll and other useful parameters to their fishing operations. Integration of satellite derived environmental data is particularly beneficial in conjunction with FAD based purse seining, i.e. planning optimal areas for seeding FAD arrays, monitoring potential FAD movements and locating FADs in areas of beneficial currents and high productivity.

The integration of remote sensing, buoy data and shipboard electronics (sounder, sonar, GPS, etc.) highlights the importance of computers on modern purse seine vessels. Vessels are being equipped or retro-fittted with fully integrated computer networks. The bridge and chartroom of modern purse seiners bear little resemblance to those of twenty or even ten years ago Figure 13).

Figure 13. Fully integrated and computerized bridge and chart room of tuna purse seine vessel.

Source; ”Documentation and classification of fishing gear and technology on board tuna purse seine vessels”. David G.Itano

Posted in FISHING boat ship vessel, FISHING GEAR, PURSE SEINE FISHING Tags: Bird RADAR, bridge monitor, bridge system, buoy, Communications, depth sensor, depth sounder, Doppler current meter, echo sounder, electronic technology, furuno, furuno sonar, GPS, GPS buoy, GPS FAD, GPS tracking buoys, GPS transcieper, integrated bridge system, monitoring, navigation, Navigational, purse seine vessel, radar furuno, radio buoy, radio buoys, RDF buoys, Remote sensing, ship bridge, simrad, simrad echo sounder, Simrad ES 60, simrad sonar, Simrad SP 90, sonar, sonar buoy, tuna sonar, Water column, WCPO

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