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Development of an oceanographic towing vehicle adapted for fishing craft: Prototype and protocol for use
Methods in Oceanography 9 (2014) 61–74
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Development of an oceanographic towing vehicle adapted for fishing craft: Prototype and protocol for use José Faccin ∗ , Dyegho M.C. Gama Cunha, Roberto Barddal, Charrid Resgalla Jr. Universidade do Vale do Itajaí (Univali), Centro de Ciências Tecnológicas, da Terra e do Mar (CTTMar), Rua Uruguai, 458, CEP 88302-202, Cetro - Itajaí - Santa Catarina, Brazil
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Article history: Received 28 January 2014 Received in revised form 27 September 2014 Accepted 24 October 2014
Keywords: Oceanographic sampler High-speed vehicle Ships of opportunity Autonomy
∗
abstract Since the 1930s, the use of the Continuous Plankton Recorder (CPR) sampler has been considered one of the most important plankton collection methods using ships of opportunity, which make samples available on a wider spatial and temporal scale. With this advantage in mind, the objective of this work was to develop a device that uses a similar collection method as the CPR, but with lower construction costs, and to carry out changes in functioning that facilitate its use in fishing craft in the Southeast and South regions of Brazil, for use as a tool for generating oceanographic data applied to fisheries management. The new equipment, called the Oceanographic Towed Vehicle (Veículo Oceanográfico de Reboque — VOR), has mechanical improvements and construction alterations for combined use with a multiparameter probe. For the new design of the vehicle, the aim was to create the hydrodynamic shape of an Undulating Towed Vehicle (U-tow), but without the characteristic of undulating in the water column. Based on a prototype, three experimental trawls were carried out, to calibrate the mechanism and analyze the material collected, in a laboratory, through a stereoscopic microscope. © 2014 Elsevier B.V. All rights reserved.
Corresponding author. E-mail address: [email protected] (J. Faccin).
http://dx.doi.org/10.1016/j.mio.2014.10.003 2211-1220/© 2014 Elsevier B.V. All rights reserved.
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1. Introduction One of the means used to monitor the marine ecosystems is, without doubt, the use of planktonic indicators, as according to Batten and Burkill (2010), these can rapidly and directly reflect the state of the ecosystem. Plankton analysis can also detect oceanographic phenomena resulting from physical and chemical anomalies in the water, such as variations in the diversity of copepods, as occurred in the 1990s in the North Sea (Beaugrand, 2004). Alongside this, through monitoring programs using continuous methods, evidence of possible time variations can be obtained in the recruitment of some species of fish, as reported by Beaugrand (2004, 2005) for cod in the North Atlantic. Sir Alister Hardy, in the 1920s, developed an innovative collection method for sampling plankton. This equipment, unlike conventional devices, was designed to solve a very common problem in sampling by the traditional method, which is the lack of precision due to irregular distribution of plankton during a tow (Hosie, 2004). The Continuous Plankton Recorder (CPR) is a sampler developed by Hardy (1936, 1939). It was originally designed for quantitative samplings of mesozooplankton, as well as giving an indication of phytoplankton ‘‘blooms’’ through the analysis of mesh color (Phytoplankton Colour Index—PCI) (Hardy, 1939; Batten et al., 2003; Head and Pepin, 2010). The equipment enables detailed study of various changes in abundance of different planktonic organisms (phyto- and zooplankton) along a continuous line of observation at sea. With this new equipment, it was possible to supplement conventional collection techniques such as towed nets (Hardy, 1936, 1939), with the use of ‘‘ships of opportunity’’, and it became possible to establish monitoring programs in oceanographic regions (Warner and Hays, 1994). Over time, new devices have emerged to replace Hardy’s model, such as the Video Plankton Recorder (VPR) (Davis et al., 1992). However, the complexity of their operation, associated with the need for specialized vessels and the cost of acquisition and maintenance, have limited their use on ships of opportunity (in this context, industrial fishing boats). A lower cost model of the equipment would therefore be useful, built using alternative materials such as fiberglass composite, and with fully mechanical functioning. This work therefore aims to develop an optimized model of the CPR for use on fishing vessels operating on the Brazilian coast, with the possibility of generating data that can be used in the management of this important economic sector. 2. Materials and methods 2.1. Setting up the prototype Based on the works of Hardy (1926, 1936, 1939) and John and Reid (2009), adaptations and changes were made to the layout of the CPR aimed at making its operation more practical in ships of opportunity of the fishing fleet. The graphic project of the prototype was set up using the software CAD R Solidworks⃝ , after which it was separated into two working fronts; (1) defining the metal pieces, and milling these pieces at a local machine shop and (2) constructing the vehicle and other components, which was done on the premises of Universidade do Vale do Itajaí (Univali), at the Center for Technological Sea and Earth Sciences (CTTMar—Course in Naval Construction). The new equipment was named the Oceanographic Towing Vehicle (Veículo Oceanográfico de Reboque—VOR). The adaptation of the new model in relation to the traditional CPR involved the proposal of a more modern concept, with a facilitated manufacturing process and lower cost due to the use of alternative materials (fiberglass composite). The final cost of the VOR was estimated at approximately U$8,000.00 (Fiberglass vehicle, cassette, roll of silk). Also, a 25% reduction in the size of the original cassette was proposed, and the cog system was modified in relation to the traction of the collection components and adjustment of mesh tension, facilitating its operation during use on board ships of opportunity. Based on the same mechanical principles as the CPR, the layout of the vehicle was based on the Undulating towed vehicle described by Hays et al. (1998), Reid et al. (2003) and Mair and Fernandes (2004), but with changes to its structure and compartmentalization (multiparameter cassette and probe). Produced completely in fiberglass composite, the resulting equipment is resistant, lightweight, easy to handle, and low-cost, making it ideal for various types of ship of opportunity (Fig. 1).
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Fig. 1. Comparison between the CPR (SAHFOS—Sir Alister Hardy of the foundation for ocean science) and VOR (Univali). Photos CPR Luciano Fischer, VOR José Faccin.
To reduce the amount of work on board, the new cassette (plankton collector) does not use the fusee wire traction mechanism used in the traditional CPR, which is a device consisting of a steel wire that directly pulls a cone-shaped spool, which gathers in the silk containing the collected organisms, and compensates for the increase in diameter, due to the accumulation of mesh with each turn of the collection spool. A torque meter system was designed (Fig. 2), which is responsible for gathering the mesh and compensating for the increased diameter of this latter spool due to the accumulation of the mesh over time. It acts by exerting sufficient and limited traction to turn the spool, which collects the silk through an internal plastic resistance spring. If there is excessive tension, the spring of the torque meter jumps to the next tooth of the internal crown, causing the spool to stop winding until the traction cylinders of the mesh have once again freed the expected amount of silk, resolving the problem of tension on the silk. The use of the torque meter was aimed to minimize the work needed to deploy the VOR, as it does away with the need to rewind the steel wire on the spool. The most that needs to be done is to replace the plastic rod if it shows signs of wear. 2.2. Body For the construction of the vehicle, a manual lamination process was used on a wooden mold. The lamination process was carried out according to Nasseh (2008), using a layer of 450 g/m2 fiberglass and orthophthalic polyester (pre-accelerated) with the addition of catalyst to complete the chemical reaction at a proportion of 4 ml–400 g of resin, with the uniform application of 3–4 layers, depending on the area worked with. Immediately after the lamination process, the parts that comprise the vehicle were assembled, to make it more rigid and give structure to all the parts. 2.3. The propeller and gearbox For the choice of propeller and pitch angle, some principles described by Geer (1989) were described, such as the number, area, thickness and shape of the blades, among other factors. The model of the propeller used was based on the need to obtain a larger surface area in contact with the water,
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Fig. 2. Torque meter: (A) Mounted view, (B) Exploded view: 1—Connecting gears with the spiked cylinder mesh traction; 2—Hollow traction gears; 3—Washer; 4–PVC tension-generating tape, 5—Torque meter cover and 6–Cover fixing screws, (C) Torque meter without cover. (Link Dropbox: https://www.dropbox.com/s/wund2z57jj1ak70/Torque%20meter.PDF?dl=0.)
and also to maintain continuous rotation of the blades. For this reason, a propeller with three straight blades was chosen, to ensure that the water would reach at least one of the blades, maintaining the rotation in the assembly and exposing the subsequent blade to the flow of water. The propeller used in the VOR, produced entirely in AISI 316 stainless steel, is configured with easy adjustment of pitch, by 8 mm screws. This propeller was developed due to the need for pitch adjustments to synchronize the number of revolutions with the collection of the plankton filtering mesh. For the calculation of pitch (Ph), were used the ratios between the available measurements of a right triangle (Fig. 3) and the tangent trigonometric ratio according to Scaramboni and Novaes (1997): tan β =
co
(1)
ca
where: tan β = tangent of angle β co = opposite cathetus, which is equivalent to the propeller pitch (Ph); ca = adjacent cathetus, which corresponds to the perimeter of the cylinder around which the helicoidal line is located (d × π ); d = diameter of the cylinder formed by the propeller pitch. Altering the respective values, we obtain the following equation: Ph =
d·π tan β
.
(2)
Thus, the propeller with a diameter of 208 mm and a pitch of 63° generates a theoretical rotation of up to 1444 revolutions per mile, with dislocation of approximately 1282 mm with each complete turn of the propeller. The total value of rotations per mile was divided by the number of teeth on each of the cogs that make up the gearbox, resulting in approximately 1000:1 revolutions, such that with the due compensation of the propeller, for each nautical mile traveled, 10 mm of the silk would be pulled through the system (Beaugrand, 2004). For this, a set of auger screws and crown gears was
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Fig. 3. Representation of the propeller pitch.
designed, forming an ‘‘auger screw—crown system’’. Although the movement of the silk in the VOR is approximately to that of the CPR. 2.4. Towing depth Even without an active depth controller, the shape of the vehicle and the presence of a rear fin cause the whole set to act like a depressor, which together with its weight, the length of the cable and the towing speed, will maintain a constant depth, as suggested by Helmond (2001). The calculation of the length of the towing cable is designed to submerge to a depth of 10 m, which according to PintoCoelho (2004) and Calazans et al. (2011) may be obtained through the trigonometric relations based on wire angle and towing point. 2.5. Sea trials After the construction of the prototype, the VOR sea trials were carried out on March 21, 2012 on board the IBAMA fishing vessel the Soloncy Moura, which is equipped with a hydraulic winch in the stern. The trawling area was the coastal region of the towns of Itajaí and Balneário Camboriú (−26° 57′ 34.404′′ S and −48° 34′ 34.834′′ W) (Fig. 4). Made completely from fiberglass composite, the resulting equipment is light and robust for its proposed application in fishing operations on the Brazilian coast, where the fishing craft travels at a maximum speed of 10 knots, without having to reduce speed to deploy and remove the equipment. Three trawls of 5 nm (nautical miles) were carried out, each with a speed of approximately 7.6 knots, for calibration of the propeller pitch, and the hydrodynamic behavior of the VOR was checked. After each trawl, the equipment was taken back on board. The mesh was taken out of the cassette and measured with a pachymeter, and the propeller pitch angle was adjusted to obtain movement of 5 cm of mesh, which is equivalent to 5 miles (1 cm/1 NM).
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Fig. 4. Map showing the course of the tows performed in the trial with the VOR.
2.6. Mesh used A model XX 6 (Tegape) multifilament silk mesh was acquired, with mesh size of 212 µm, supplied on a roll 1 m in width by 6 m in length, used in the experimental trawls. To load into the cassette, the mesh was cut into strips 11.5 cm in width and 6 m in length (maximum capacity of the spool). A characteristic present in the silk used in the CPR is the fact that it is folded over at the edges in the portion that covers the organisms collected, to prevent it from tearing when the spool is pulled. This fold was not used in our equipment, as the two halves of the cassette have grooves without significant spaces that would allow loss of organisms. Also, the cylinders pull the silk by the side edges only (areas free of filtering), not affecting the filtered organisms. Furthermore, the spool that stores the organisms is not subject to strong traction due to the use of the torque meter. 2.7. Analysis of the zooplankton collected For analysis of the samples, the standard methodology presented by Hosie et al. (2003), Warner and Hays (1994) and Richardson et al. (2006) was used. In the laboratory, the roll of mesh in 4% formalin was unrolled and cut into sections, corresponding to the trawls carried out, of 3.3 cm, 6.1 cm and a final section of 4.8 cm (equivalent to 5 nautical miles traveled each). The organisms (Zooplankton) were removed from the surface of the silk by washing, identified using a stereoscopic microscope, and fully quantified. The phytoplankton was not analyzed in this work. 3. Results 3.1. General description of the equipment The VOR is a submersible oceanographic vehicle that can be towed either by research vessels or by those of the fishing fleet (ships of opportunity). It is operated while the vessel is navigating to
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the fishing area. When the boat is engaged in fishing operations, the equipment may, or may not be removed from the water, depending on the type of fishing carried out. The equipment (Fig. 5) is designed so that its external surface functions as a depressor. It is equipped with a horizontal stabilizing rudder, fitted onto the rear part, which gives it a hydrodynamic shape, exposing its entire surface to the flow of water and forcing it to dive. Its depth of operation is controlled only by the length of the tow cable to which it is fixed, on the rear part, by the tow bar, which is fixed onto the sides of the vehicle. The VOR has a hydrodynamic shape, is 500 mm in width, 860 mm in length, and weighs approximately 30 kg compared with 90 kg for the traditional CPR. On the front section, it has an opening of 1.62 cm2 to direct the flow of water inside the cassette. Also, on the front and rear sections, it has rectangular openings to promote flooding of the equipment and circulation of water in the internal compartments. On the rear part there are two vertical fins and a horizontal rudder, which give the vehicle greater stability and submersion ability, respectively. Both the rounded front and the horizontal rudder force the equipment to dive. The form of the horizontal rudder is isometric, i.e. it has two equal sides (upper and lower) with the possibility of regulating the angle of attack. It has a pre-established tilt of 10° to maintain the wake of the upright vehicle, which helps to expose the surface of the equipment to the laminar flow of water, forcing it to dive continually. Inside the vehicle, there are two compartments, one for the cassette and the other for the installation of a probe and other oceanographic data collection instruments, which can be coupled as needed, for the sample collections. Also in the interior is a gearbox to which the initial axle (input) is coupled to the propeller and the final axle (output) is linked to the cassette. The operation of the internal mechanisms (propeller, gear and cassette) is done through the flow of water during the tow, which drives a propeller, transferring the energy through an axle, to the reduction system, reaching the set of cogs of the cassette, which in turn, drives the spools holding the filtering mesh, so that approximately 1 cm of mesh is dislocated for each nautical mile navigated. The submersion of the equipment is limited only by the length of the towing cable to which it is fixed on the tow bar. The upper part of the VOR has a cover that gives access to the interior of the vehicle, separated in the middle by a divider separating the compartments for the plankton collection cassette and for the installation of probe for the acquisition of oceanographic data. The equipment can be towed by ships of opportunity (fishing or research), by means of a cable, preferably in steel, fixed to the front tow bar, made from AISI 316 stainless steel, 20 mm in diameter, fixed to the body of the equipment with screws, also in stainless steel, 18 mm in diameter. At the tow bar fixing site, steel plates of 2 mm thickness were laminated in fiberglass, together with the walls of the vehicle, giving greater resistance against shearing during towing. 3.2. Internal metal components The vehicle has a number of metal components, such as the tow bar, lateral reinforcements, cassette mounting rod, collector cassette, gear box, propeller/bearing assembly and axle (Fig. 6). The reduction of the rotation of the propeller, at a ratio of 1000:1, is accomplished by a gearbox. The auger screws of the gearbox connect to the pinion, which connects to the vulcanized cylinder that pulls the fabric of the cassette. This auger shaft transfers the driving force by a system of cogs, to the larger spool, which gathers the mesh storing the organisms collected in the rear compartment comprised of a tank with formaldehyde. The cassette was designed to hold up to 6 m (multifilament silk) fabric, which is equivalent to independent operation of 600 nautical miles. Fig. 7(A) and (B) shows their parts and the functioning of the cassette, where the mesh, demarcated every 5 cm (filter mesh), is loaded into one of the spools in the front portion below the tunnel; it passes through the opening (7) and rises by sliding along the walls (11) and (2) limited at the sides by devices (6) and (9), passing through the tunnel. The mesh then immediately joins another mesh which exits from the upper spool (14), which crosses another top slot (10). The water that passes through the tunnel is prevented from overflowing at the sides or bottom through devices (1) and (8) which ‘‘seal’’ the two halves of the cassette. Both the filter mesh and the mesh that covers it, forming a ‘‘sandwich’’ that holds the collected plankton, are wound by rollers (12) and (3), passing through the comb (4) which prevents possible accidental winding on the cylinder (3) being wrapped by the spool (5), and
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Fig. 5. (A) Isometric view of the VOR. 1—Tow bar; 2—Entry of water to the probe compartment; 3—Hydrodynamic front end of the VOR; 4—Entry of water to the cassette; 5—Mounting bolt of the tow bar; 6—Propeller axis; 7—Propeller; 8 and 9—Rudder mounting screws; 10—Sustaining rudder, 11—Stabilizing fin, and 12—Access cover to the cassette and probe compartments. (B) View of the open VOR: 1—Instrument compartment; 2—Support for attaching equipment; 3—Dividing wall between the compartments; 4—Gearbox; 5—Cassette compartment; 6—Rod for locking and mounting the cassette, 7—Water inlet duct to the cassette and 8—Hole for entry of water. (Animation) (Link Dropbox: https://www.dropbox.com/s/36n9y3ybbhjyb4f/VOR. PDF?dl=0).
stored inside the fixation tank for the mesh containing organisms. It should be noted that the mesh is pulled through the cylinder (12) by its edges (13), in order to preserve the integrity of organisms
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Fig. 6. Internal metal components of the VOR 1—Propeller and bearing; 2—Gearbox; 3—Cassette; 4—Cassette mounting rod; 5—Tow bar mounting reinforcement; 6—Tow bar, 7—Adaptor for entry of water to the cassette and 8—Fixing clamps for probe and equipment.
collected through a gap built into the device. Fig. 7(C) shows the cassette already mounted with the two parts fitted in. Fig. 7(D) shows the passage of the water through the tunnel, and the silk feed operating system, as follows: (1) entry of water containing plankton; (2) covering layer of silk that joins with the filtering silk just above the tunnel; (3) filtering mesh; (4) storage spool and (5) filtered water outlet. 3.3. Sea trials with the VOR With the completion of the test at sea, it was possible to determine the best propeller pitch angle to ensure synchronicity between the displacement of the filter mesh and the distance navigated. With the constant speed in all the trawls at 7.6 knots, the first adjustment of regulation of the propeller blades at 45° resulted in displacement of the silk of 33 mm for the 5 nautical miles navigation, with the capture of thirty-eight zooplanktonic specimens. In the second trawl, the propeller pitch was changed to approximately 30°, resulting in displacement of 61 mm of silk and the capture of 99 specimens. Finally, in the third trawl, by adjusting the propeller pitch by 35°, displacement of 48 mm of silk was obtained at 5 NM navigated, with retention of 126 zooplanktonic specimens. The VOR also presents stable hydrodynamic behavior to the trawls carried out, due to the absence of both horizontal and vertical movements, observed through visual observation and with video records from on board the vessel. This is due to the fact that operation of the equipment in the initial phase of the trawls is very close to the surface, and also the rapid diving capacity as soon as the horizontal rudder is submersed (Fig. 8). 3.4. Collection protocol Batten and Burkill (2009) report discussions on the standardization and calibration of the methods used for the collection and analysis of data for continuous plankton samplings, but it should take into consideration that each research study or region has its own objectives, which must be met when using a method.
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Fig. 7. Open cassette. (A) 1—Entry of cassette; 2—Water tunnel protection grill; 3—Spiked cylinder mesh traction; 4—Mesh protection comb; 5—Filtered mesh collection spool; (B) 6—Lateral holding runner for the mesh; 7—Opening for passage of the mesh; 8—Sealing box for the cassette; 9—Lateral holding runner for the mesh; 10—Opening for passage of the filtering cover mesh; 11—Wall of the cassette; 12—Vulcanized cylinder to pull the mesh; 13—Traction edges of the vulcanized cylinder and 14—Upper spool for storage of the mesh; (C) Cassette mounted and (D) Functioning of the cassette system. 1—Entry of water containing plankton; 2—Covering mesh; 3—Filtering mesh; 4—Storage spool and 5—Filtered water outlet. (Link Dropbox: https://www.dropbox.com/s/7244ri76viyiseo/Cassete.PDF?dl=0).
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Fig. 8. VOR sea trials, with launch (1 and 2) and collection (3 and 4). (Link Video: https://www.dropbox.com/s/35ofhagcnp7u3bx/Lance%20do%20VOR.mp4?dl=0).
The creation of a protocol of procedures to be adopted aims to standardize and give conditions of reproducibility in collections with the VOR. For this, the use of a mesh with larger pore size of between (270 and 300 µm) will be considered, adapting it to the organism collection, the characteristics of the local biota, and the typical conditions of warm waters of the Brazilian coast.
• Before the start of the cruise, the cassette should be prepared with the mesh filter; • During the voyage, with the cassette prepared, the mesh should be demarcated at the place where the filtering will begin, with the words ‘‘INÍCIO’’ (start), the date and the number of trawls, and the bottom mesh should be positioned so that the line marking 5 nautical miles is positioned at the bottom of the water flow tunnel input; • When the VOR is launched into the sea, the record sheet should be used, noting down the VOR tow number, the vessel name, the name of the master of the vessel, the route of the vessel, and the person responsible for making the record. The date, times (launch and recovery of the VOR), operation of the VOR (launch or recovery), geographical coordinates, including longitude and latitude (specifying the abovementioned data), distance of trawling (nautical miles), speed of the vessel during the trawling (knots) and the weather conditions during the period of the trawl. These observations provide important additional information for interpretation of the data; • Soon after the equipment is removed from the water, the mesh is marked with a line on the traction cylinders, and the words ‘‘FIM’’ (end), to indicate the end of each tow and then the silk is removed from the storage tank; • The mesh should then be unwound from the final spool and spread out on a white surface, for a comparative reading of the color standard to estimate the phytoplanktonic density (color index for phytoplankton) (John and Reid, 2009). After reading the phytoplanktonic index, the mesh should be wrapped and tied with rubber bands, and stowed in a container containing correctly-buffered 4%
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J. Faccin et al. / Methods in Oceanography 9 (2014) 61–74 Table 1 Comparative table between VOR and CPR. Characteristics of the cassettes
VOR
CPRa
Area of water tunnel in mesh region (mm2 ) Width of spools (mm) Width of cassette (mm) Length of cassette (mm) Displacement of silk/mile (mm) Capacity of spool (m) Mesh compensation mechanism
2220
5100
115 136 270 10 6 Torque meter
155 200 300 10 5.7 Fusee wire
30 1.62 50 86 Fiberglass <10 Yes
90 1.62 40 100 Metal <20 Yes
Characteristics of the bodies Weight (kg) Opening (cm2 ) Width (cm) Length (cm) Construction material Operating speed (knots) Space for additional sensors a
Approximate values.
formalin solution to maintain the integrity of the sample. It is then sent to the laboratory, together with its respective records. In the laboratory, using the data in the record sheet, and assuming a constant towing speed, the mesh is unrolled, the number of records made is checked, and the samples are prepared for analysis. 4. Discussion A device was developed that is lightweight, easy to transport, and hydrodynamically stable under tow, with some characteristics that differ from the traditional CPR. The main innovations of the VOR are its fiberglass composite construction, its shape, and its interior divided into two compartments, one housing a probe to collect oceanographic data and the other for a plankton collector. The choice of U-Tow as a model for the layout of the VOR was due to its good hydrodynamic conformation and its ability to stow additional equipment, owing to the internal space. Hays et al. (1998) affirm that the U-Tow consists of a small sampling vehicle (<1 m in length), and may be towed at high speed (>10 knots), with a mechanism that enables undulatory function, but which has limited use in mesh plankton collectors, due to imprecision in the spatial identification of the occurrence of organisms. For the cassette of the VOR, the same principles as Hardy (1939) were adopted, i.e. a 1.62 cm2 opening followed by widening of the start of the water tunnel to give a cross-section diameter of (17 mm × 74 mm) 1258 mm2 , and in the region of the mesh, widening to (30 mm × 74 mm) 2220 mm2 , narrowing at the output to 1258 mm2 . With this configuration, the speed of the water passing through the mesh is reduced, minimizing damage to the morphology of the organisms collected. Table 1 shows some comparative values between the VOR and the CPR. The main characteristics of the new cassette include: its smaller size, making it lighter, smaller spools, but with the same or greater sampling distance and its innovative torque meter system, which replaces the fusee wire used in the traditional CPR. This replacement by a torque meter system facilitates its operation, as it does away with the need to rewind the fusee wire on board, with a steel wire. For the capture of organisms observed in the experimental trawls, it is suggested that the speed with which the silk passes through the rollers may influence the filtration efficiency and the counting process. However, the number of trawls carried out does not enable this trend to be confirmed, since variations in the abundance of plankton and towing speed, as well as the porosity of the silk, can also influence the counting (Batten et al., 2003). It would be expected that the counting in the VOR would be more pronounced, due to the more coastal area of operation and the smaller filtering area. However,
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this effect can be mitigated by the low operating speed (fishing boats) as well as the replacement, in the future, with a more porous mesh (270 µm). 5. Conclusions This paper presents a prototype of an oceanographic towing vehicle. This device has an innovative design feature, which is its hydrodynamic shape, giving it greater stability. Made from composite fiberglass, it is relatively lightweight yet robust, with reinforced internal structure, which makes it capable of withstanding rough handling on regional fishing fleet or research vessels as well as making it easy to deploy and recover. Due to its construction characteristics, it was possible to reduce the weight of the equipment from 90 kg (CPR) to just 30 kg (VOR), including the multiparameter probe and cassette, thereby reducing difficulties associated with its operation in smaller boats. Besides the reduced weight, it also has other improvements, such as the practicality of the innovative Torque Meter mechanism, providing a mechanical alternative to the fusee wire method used in the traditional CPR, making the system easier for the equipment operator to use, and facilitating its use on board. Whenever scientific equipment is placed on board fishing vessels, it is essential to clarify, for the owner and crew of the vessel, the importance and need for the implementation of the equipment, and that the data generated through this logistical support will be fed back, in the form of information and knowledge, for the benefit of the fishing industry. Among the various types of vessels in the region, trawlers, including tuna trawlers, or those with hydraulic winches, are recommended for the use of the VOR sampler, as these fishing methods generally have highest number of boats, with longer periods at sea, enabling a wider spatial sweep. With the use of the VOR in these vessels, it is also possible to carry out long-term studies for early detection of environmental anomalies in coastal and oceanic regions, as well as assisting in the interpretation of physical–chemical variables collected by other instruments currently used in oceanography (e.g. CTD). By coupling a multiparameter probe to the loading compartment of the VOR, it is possible to gather data on salinity, turbidity, pH, BOD, temperature, and chlorophyll-α , among other data, allowing for cross-referencing of the physical/chemical data and correlating them with the biological data obtained by the VOR. Our intention is to promote permanent use of this equipment by the Universidade do Vale do Itajaí (UNIVALI), particularly in fishing activities in their different modalities that operate from Santa Catarina (Brazil). The use of the equipment is also aimed at obtaining data, supporting projects for the formation of human resources at graduate, master’s and doctorate levels. The possibilities of making the equipment commercially available are not ruled out either, if there is demand. Acknowledgments We thank CAPES, in the scope of the IGEPESCA Project, Sea Sciences Notice of March 9, 2009 is the financial support and the CNPq for the productivity grant, Process 305910/2011-6. We are also grateful to the team of the Centro de Pesquisa e Gestão de Recursos Pesqueiros do Litoral Sudeste e Sul (CEPSUL) (Center for Research and Management of Fishery Resources in the South East Coast and South Coasts) for providing the Research vessel Soloncy Moura (Soloncy Moura Research Vessel) for use in the sea trials. References Batten, S.D., Burkill, P.H., 2009. Continuous plankton recorder surveys of the global oceans. PICES Press 17 (2), 20–21. Batten, S.D., Burkill, P.H., 2010. The continuous plankton recorder: towards a global perspective. J. Plankton Res. 32 (12), 1619–1621. http://dx.doi.org/10.1093/plankt/fbq140. Batten, S.D., Walne, A.W., Edwards, M., Groom, S.B., 2003. Phytoplankton biomass from continuous plankton recorder data: an assessment of the phytoplankton colour index. J. Plankton Res. 25 (7), 697. http://dx.doi.org/10.1093/plankt/25.7.697. Beaugrand, G., 2004. Monitoring marine plankton ecosystems. I: description of an ecosystem approach based on plankton indicators. Mar. Ecol. Prog. Ser. 269, 69–81. http://dx.doi.org/10.3354/meps269069. Beaugrand, G., 2005. Monitoring pelagic ecosystems using plankton indicators. ICES J. Mar. Sci. 62 (3), 333–338. http://dx.doi.org/10.1016/j.icesjms.2005.01.002.
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Calazans, D.K., Muelbert, J.H., Muxagata, E., 2011. Organismos Planctônicos. In: Calazans, D. (Ed.), Estudos Oceanográficos: Do Instrumental ao Prático. Editora Textos, Pelotas, RS, pp. 200–274. (Org.). Davis, C., Gallager, S., Berman, M., Haury, L., Strickler, J., 1992. The Video Plankton Recorder (VPR): design and initial results. Arch. Hydrobiol. Beih 36, 67–81. Geer, D., 1989. Propeller Handbook, The Complete Reference for Choosing, Installing, and Understanding Boat Propellers. International Marine, Maine, USA, p. 166. Hardy, A.C., 1926. A new method of plankton research. Nature 118, 630–632. Hardy, A.C., 1936. The continuous recorder plankton. Discov. Rep. 11, 457–510. Hardy, A.C., 1939. Ecological investigations with the continuous plankton recorder: object, plan & methods. Hull Bull. Mar. Ecol. 1, 1–57. Hays, G.C., Walne, A.W., Quartley, C.P., 1998. The U-Tow: a system for sampling mesozooplankton over extended spatial scales. J. Plankton Res. 20, 135–144. Head, E.J.H., Pepin, P., 2010. Monitoring changes in phytoplankton abundance and composition in the Northwest Atlantic: a comparison of results obtained by continuous plankton recorder sampling and colour satellite imagery. J. Plankton Res. 32 (12), 1649–1660. http://dx.doi.org/10.1093/plankt/fbq120. Helmond, I., 2001. Towed vehicles. In: Steele, J.H., Thorpe, S.A., Turekian, K.K. (Eds.), Measurement Techniques, Platforms & Sensors: A Derivative of the Encyclopedia of Ocean Sciences. Encyclopedia of Ocean Sciences. Academic Press, p. 635. Hosie, G., 2004. Plankton survey uses old technology to monitor the future. In: Australian Antartic Magazine, Vol. 6. pp. 15–17. Hosie, G., Fukuchi, M., Kawaguchi, S., 2003. Development of the southern ocean continuous plankton recorder survey. Prog. Oceanogr. 58 (2–4), 263–283. http://dx.doi.org/10.1016/j.pocean.2003.08.007. John, A.W.G., Reid, P.C., 2009. Continuous plankton recorders. In: Steele, J.H., Thorpe, S.A., Turekian, K.K. (Eds.), Measurement Techniques, Platforms & Sensors: A Derivative of the Encyclopedia of Ocean Sciences, Encyclopedia of Ocean Sciences. Academic Press, p. 635. Mair, A., Fernandes, P., 2004. Examination of North Sea plankton samples in relation to multifrequency echograms. In: ICES CM, 10. Nasseh, J., 2008. Técnica e Prática de Laminação de Compósitos. Rio de Janeiro: s.n. Pinto-Coelho, R.M., 2004. Métodos de coleta, preservação, contagem e determinação de biomassa em zooplâncton de Águas epicontinentais. In: Bicudo, C.E.M., Bicudo, D.C. (Eds.), Amostragem em Limnologia. RiMa, pp. 149–166. Reid, P., Colebrook, J.M., Matthews, J.B.L., Aiken, J., 2003. The continuous plankton recorder: concepts and history, from plankton indicator to undulating recorders. Prog. Oceanogr. 58 (2–4), 117–173. http://dx.doi.org/10.1016/j.pocean.2003.08.002. Richardson, A.J., Walne, A.W., John, A.W.G., Jonas, T.D., Lindley, J.A., Sims, D.W., Stevens, D., Witt, M., 2006. Using continuous plankton recorder data. Prog. Oceanogr. 68 (1), 27–74. http://dx.doi.org/10.1016/j.pocean.2005.09.011. Scaramboni, A., Novaes, R.C.R., 1997. Realizando Cálculos Para o Aparelho Divisor (III) Aula 15. Curso Profissionalizante Mecânica, 1, 3–7. Warner, A.J., Hays, G., 1994. Sampling by the continuous plankton recorder survey. Prog. Oceanography 34, 237–256. http://dx.doi.org/10.1016/0079-6611(94)90009-4.
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Full length article
Development of an oceanographic towing vehicle adapted for fishing craft: Prototype and protocol for use José Faccin ∗ , Dyegho M.C. Gama Cunha, Roberto Barddal, Charrid Resgalla Jr. Universidade do Vale do Itajaí (Univali), Centro de Ciências Tecnológicas, da Terra e do Mar (CTTMar), Rua Uruguai, 458, CEP 88302-202, Cetro - Itajaí - Santa Catarina, Brazil
article
info
Article history: Received 28 January 2014 Received in revised form 27 September 2014 Accepted 24 October 2014
Keywords: Oceanographic sampler High-speed vehicle Ships of opportunity Autonomy
∗
abstract Since the 1930s, the use of the Continuous Plankton Recorder (CPR) sampler has been considered one of the most important plankton collection methods using ships of opportunity, which make samples available on a wider spatial and temporal scale. With this advantage in mind, the objective of this work was to develop a device that uses a similar collection method as the CPR, but with lower construction costs, and to carry out changes in functioning that facilitate its use in fishing craft in the Southeast and South regions of Brazil, for use as a tool for generating oceanographic data applied to fisheries management. The new equipment, called the Oceanographic Towed Vehicle (Veículo Oceanográfico de Reboque — VOR), has mechanical improvements and construction alterations for combined use with a multiparameter probe. For the new design of the vehicle, the aim was to create the hydrodynamic shape of an Undulating Towed Vehicle (U-tow), but without the characteristic of undulating in the water column. Based on a prototype, three experimental trawls were carried out, to calibrate the mechanism and analyze the material collected, in a laboratory, through a stereoscopic microscope. © 2014 Elsevier B.V. All rights reserved.
Corresponding author. E-mail address: [email protected] (J. Faccin).
http://dx.doi.org/10.1016/j.mio.2014.10.003 2211-1220/© 2014 Elsevier B.V. All rights reserved.
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1. Introduction One of the means used to monitor the marine ecosystems is, without doubt, the use of planktonic indicators, as according to Batten and Burkill (2010), these can rapidly and directly reflect the state of the ecosystem. Plankton analysis can also detect oceanographic phenomena resulting from physical and chemical anomalies in the water, such as variations in the diversity of copepods, as occurred in the 1990s in the North Sea (Beaugrand, 2004). Alongside this, through monitoring programs using continuous methods, evidence of possible time variations can be obtained in the recruitment of some species of fish, as reported by Beaugrand (2004, 2005) for cod in the North Atlantic. Sir Alister Hardy, in the 1920s, developed an innovative collection method for sampling plankton. This equipment, unlike conventional devices, was designed to solve a very common problem in sampling by the traditional method, which is the lack of precision due to irregular distribution of plankton during a tow (Hosie, 2004). The Continuous Plankton Recorder (CPR) is a sampler developed by Hardy (1936, 1939). It was originally designed for quantitative samplings of mesozooplankton, as well as giving an indication of phytoplankton ‘‘blooms’’ through the analysis of mesh color (Phytoplankton Colour Index—PCI) (Hardy, 1939; Batten et al., 2003; Head and Pepin, 2010). The equipment enables detailed study of various changes in abundance of different planktonic organisms (phyto- and zooplankton) along a continuous line of observation at sea. With this new equipment, it was possible to supplement conventional collection techniques such as towed nets (Hardy, 1936, 1939), with the use of ‘‘ships of opportunity’’, and it became possible to establish monitoring programs in oceanographic regions (Warner and Hays, 1994). Over time, new devices have emerged to replace Hardy’s model, such as the Video Plankton Recorder (VPR) (Davis et al., 1992). However, the complexity of their operation, associated with the need for specialized vessels and the cost of acquisition and maintenance, have limited their use on ships of opportunity (in this context, industrial fishing boats). A lower cost model of the equipment would therefore be useful, built using alternative materials such as fiberglass composite, and with fully mechanical functioning. This work therefore aims to develop an optimized model of the CPR for use on fishing vessels operating on the Brazilian coast, with the possibility of generating data that can be used in the management of this important economic sector. 2. Materials and methods 2.1. Setting up the prototype Based on the works of Hardy (1926, 1936, 1939) and John and Reid (2009), adaptations and changes were made to the layout of the CPR aimed at making its operation more practical in ships of opportunity of the fishing fleet. The graphic project of the prototype was set up using the software CAD R Solidworks⃝ , after which it was separated into two working fronts; (1) defining the metal pieces, and milling these pieces at a local machine shop and (2) constructing the vehicle and other components, which was done on the premises of Universidade do Vale do Itajaí (Univali), at the Center for Technological Sea and Earth Sciences (CTTMar—Course in Naval Construction). The new equipment was named the Oceanographic Towing Vehicle (Veículo Oceanográfico de Reboque—VOR). The adaptation of the new model in relation to the traditional CPR involved the proposal of a more modern concept, with a facilitated manufacturing process and lower cost due to the use of alternative materials (fiberglass composite). The final cost of the VOR was estimated at approximately U$8,000.00 (Fiberglass vehicle, cassette, roll of silk). Also, a 25% reduction in the size of the original cassette was proposed, and the cog system was modified in relation to the traction of the collection components and adjustment of mesh tension, facilitating its operation during use on board ships of opportunity. Based on the same mechanical principles as the CPR, the layout of the vehicle was based on the Undulating towed vehicle described by Hays et al. (1998), Reid et al. (2003) and Mair and Fernandes (2004), but with changes to its structure and compartmentalization (multiparameter cassette and probe). Produced completely in fiberglass composite, the resulting equipment is resistant, lightweight, easy to handle, and low-cost, making it ideal for various types of ship of opportunity (Fig. 1).
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Fig. 1. Comparison between the CPR (SAHFOS—Sir Alister Hardy of the foundation for ocean science) and VOR (Univali). Photos CPR Luciano Fischer, VOR José Faccin.
To reduce the amount of work on board, the new cassette (plankton collector) does not use the fusee wire traction mechanism used in the traditional CPR, which is a device consisting of a steel wire that directly pulls a cone-shaped spool, which gathers in the silk containing the collected organisms, and compensates for the increase in diameter, due to the accumulation of mesh with each turn of the collection spool. A torque meter system was designed (Fig. 2), which is responsible for gathering the mesh and compensating for the increased diameter of this latter spool due to the accumulation of the mesh over time. It acts by exerting sufficient and limited traction to turn the spool, which collects the silk through an internal plastic resistance spring. If there is excessive tension, the spring of the torque meter jumps to the next tooth of the internal crown, causing the spool to stop winding until the traction cylinders of the mesh have once again freed the expected amount of silk, resolving the problem of tension on the silk. The use of the torque meter was aimed to minimize the work needed to deploy the VOR, as it does away with the need to rewind the steel wire on the spool. The most that needs to be done is to replace the plastic rod if it shows signs of wear. 2.2. Body For the construction of the vehicle, a manual lamination process was used on a wooden mold. The lamination process was carried out according to Nasseh (2008), using a layer of 450 g/m2 fiberglass and orthophthalic polyester (pre-accelerated) with the addition of catalyst to complete the chemical reaction at a proportion of 4 ml–400 g of resin, with the uniform application of 3–4 layers, depending on the area worked with. Immediately after the lamination process, the parts that comprise the vehicle were assembled, to make it more rigid and give structure to all the parts. 2.3. The propeller and gearbox For the choice of propeller and pitch angle, some principles described by Geer (1989) were described, such as the number, area, thickness and shape of the blades, among other factors. The model of the propeller used was based on the need to obtain a larger surface area in contact with the water,
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Fig. 2. Torque meter: (A) Mounted view, (B) Exploded view: 1—Connecting gears with the spiked cylinder mesh traction; 2—Hollow traction gears; 3—Washer; 4–PVC tension-generating tape, 5—Torque meter cover and 6–Cover fixing screws, (C) Torque meter without cover. (Link Dropbox: https://www.dropbox.com/s/wund2z57jj1ak70/Torque%20meter.PDF?dl=0.)
and also to maintain continuous rotation of the blades. For this reason, a propeller with three straight blades was chosen, to ensure that the water would reach at least one of the blades, maintaining the rotation in the assembly and exposing the subsequent blade to the flow of water. The propeller used in the VOR, produced entirely in AISI 316 stainless steel, is configured with easy adjustment of pitch, by 8 mm screws. This propeller was developed due to the need for pitch adjustments to synchronize the number of revolutions with the collection of the plankton filtering mesh. For the calculation of pitch (Ph), were used the ratios between the available measurements of a right triangle (Fig. 3) and the tangent trigonometric ratio according to Scaramboni and Novaes (1997): tan β =
co
(1)
ca
where: tan β = tangent of angle β co = opposite cathetus, which is equivalent to the propeller pitch (Ph); ca = adjacent cathetus, which corresponds to the perimeter of the cylinder around which the helicoidal line is located (d × π ); d = diameter of the cylinder formed by the propeller pitch. Altering the respective values, we obtain the following equation: Ph =
d·π tan β
.
(2)
Thus, the propeller with a diameter of 208 mm and a pitch of 63° generates a theoretical rotation of up to 1444 revolutions per mile, with dislocation of approximately 1282 mm with each complete turn of the propeller. The total value of rotations per mile was divided by the number of teeth on each of the cogs that make up the gearbox, resulting in approximately 1000:1 revolutions, such that with the due compensation of the propeller, for each nautical mile traveled, 10 mm of the silk would be pulled through the system (Beaugrand, 2004). For this, a set of auger screws and crown gears was
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Fig. 3. Representation of the propeller pitch.
designed, forming an ‘‘auger screw—crown system’’. Although the movement of the silk in the VOR is approximately to that of the CPR. 2.4. Towing depth Even without an active depth controller, the shape of the vehicle and the presence of a rear fin cause the whole set to act like a depressor, which together with its weight, the length of the cable and the towing speed, will maintain a constant depth, as suggested by Helmond (2001). The calculation of the length of the towing cable is designed to submerge to a depth of 10 m, which according to PintoCoelho (2004) and Calazans et al. (2011) may be obtained through the trigonometric relations based on wire angle and towing point. 2.5. Sea trials After the construction of the prototype, the VOR sea trials were carried out on March 21, 2012 on board the IBAMA fishing vessel the Soloncy Moura, which is equipped with a hydraulic winch in the stern. The trawling area was the coastal region of the towns of Itajaí and Balneário Camboriú (−26° 57′ 34.404′′ S and −48° 34′ 34.834′′ W) (Fig. 4). Made completely from fiberglass composite, the resulting equipment is light and robust for its proposed application in fishing operations on the Brazilian coast, where the fishing craft travels at a maximum speed of 10 knots, without having to reduce speed to deploy and remove the equipment. Three trawls of 5 nm (nautical miles) were carried out, each with a speed of approximately 7.6 knots, for calibration of the propeller pitch, and the hydrodynamic behavior of the VOR was checked. After each trawl, the equipment was taken back on board. The mesh was taken out of the cassette and measured with a pachymeter, and the propeller pitch angle was adjusted to obtain movement of 5 cm of mesh, which is equivalent to 5 miles (1 cm/1 NM).
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Fig. 4. Map showing the course of the tows performed in the trial with the VOR.
2.6. Mesh used A model XX 6 (Tegape) multifilament silk mesh was acquired, with mesh size of 212 µm, supplied on a roll 1 m in width by 6 m in length, used in the experimental trawls. To load into the cassette, the mesh was cut into strips 11.5 cm in width and 6 m in length (maximum capacity of the spool). A characteristic present in the silk used in the CPR is the fact that it is folded over at the edges in the portion that covers the organisms collected, to prevent it from tearing when the spool is pulled. This fold was not used in our equipment, as the two halves of the cassette have grooves without significant spaces that would allow loss of organisms. Also, the cylinders pull the silk by the side edges only (areas free of filtering), not affecting the filtered organisms. Furthermore, the spool that stores the organisms is not subject to strong traction due to the use of the torque meter. 2.7. Analysis of the zooplankton collected For analysis of the samples, the standard methodology presented by Hosie et al. (2003), Warner and Hays (1994) and Richardson et al. (2006) was used. In the laboratory, the roll of mesh in 4% formalin was unrolled and cut into sections, corresponding to the trawls carried out, of 3.3 cm, 6.1 cm and a final section of 4.8 cm (equivalent to 5 nautical miles traveled each). The organisms (Zooplankton) were removed from the surface of the silk by washing, identified using a stereoscopic microscope, and fully quantified. The phytoplankton was not analyzed in this work. 3. Results 3.1. General description of the equipment The VOR is a submersible oceanographic vehicle that can be towed either by research vessels or by those of the fishing fleet (ships of opportunity). It is operated while the vessel is navigating to
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the fishing area. When the boat is engaged in fishing operations, the equipment may, or may not be removed from the water, depending on the type of fishing carried out. The equipment (Fig. 5) is designed so that its external surface functions as a depressor. It is equipped with a horizontal stabilizing rudder, fitted onto the rear part, which gives it a hydrodynamic shape, exposing its entire surface to the flow of water and forcing it to dive. Its depth of operation is controlled only by the length of the tow cable to which it is fixed, on the rear part, by the tow bar, which is fixed onto the sides of the vehicle. The VOR has a hydrodynamic shape, is 500 mm in width, 860 mm in length, and weighs approximately 30 kg compared with 90 kg for the traditional CPR. On the front section, it has an opening of 1.62 cm2 to direct the flow of water inside the cassette. Also, on the front and rear sections, it has rectangular openings to promote flooding of the equipment and circulation of water in the internal compartments. On the rear part there are two vertical fins and a horizontal rudder, which give the vehicle greater stability and submersion ability, respectively. Both the rounded front and the horizontal rudder force the equipment to dive. The form of the horizontal rudder is isometric, i.e. it has two equal sides (upper and lower) with the possibility of regulating the angle of attack. It has a pre-established tilt of 10° to maintain the wake of the upright vehicle, which helps to expose the surface of the equipment to the laminar flow of water, forcing it to dive continually. Inside the vehicle, there are two compartments, one for the cassette and the other for the installation of a probe and other oceanographic data collection instruments, which can be coupled as needed, for the sample collections. Also in the interior is a gearbox to which the initial axle (input) is coupled to the propeller and the final axle (output) is linked to the cassette. The operation of the internal mechanisms (propeller, gear and cassette) is done through the flow of water during the tow, which drives a propeller, transferring the energy through an axle, to the reduction system, reaching the set of cogs of the cassette, which in turn, drives the spools holding the filtering mesh, so that approximately 1 cm of mesh is dislocated for each nautical mile navigated. The submersion of the equipment is limited only by the length of the towing cable to which it is fixed on the tow bar. The upper part of the VOR has a cover that gives access to the interior of the vehicle, separated in the middle by a divider separating the compartments for the plankton collection cassette and for the installation of probe for the acquisition of oceanographic data. The equipment can be towed by ships of opportunity (fishing or research), by means of a cable, preferably in steel, fixed to the front tow bar, made from AISI 316 stainless steel, 20 mm in diameter, fixed to the body of the equipment with screws, also in stainless steel, 18 mm in diameter. At the tow bar fixing site, steel plates of 2 mm thickness were laminated in fiberglass, together with the walls of the vehicle, giving greater resistance against shearing during towing. 3.2. Internal metal components The vehicle has a number of metal components, such as the tow bar, lateral reinforcements, cassette mounting rod, collector cassette, gear box, propeller/bearing assembly and axle (Fig. 6). The reduction of the rotation of the propeller, at a ratio of 1000:1, is accomplished by a gearbox. The auger screws of the gearbox connect to the pinion, which connects to the vulcanized cylinder that pulls the fabric of the cassette. This auger shaft transfers the driving force by a system of cogs, to the larger spool, which gathers the mesh storing the organisms collected in the rear compartment comprised of a tank with formaldehyde. The cassette was designed to hold up to 6 m (multifilament silk) fabric, which is equivalent to independent operation of 600 nautical miles. Fig. 7(A) and (B) shows their parts and the functioning of the cassette, where the mesh, demarcated every 5 cm (filter mesh), is loaded into one of the spools in the front portion below the tunnel; it passes through the opening (7) and rises by sliding along the walls (11) and (2) limited at the sides by devices (6) and (9), passing through the tunnel. The mesh then immediately joins another mesh which exits from the upper spool (14), which crosses another top slot (10). The water that passes through the tunnel is prevented from overflowing at the sides or bottom through devices (1) and (8) which ‘‘seal’’ the two halves of the cassette. Both the filter mesh and the mesh that covers it, forming a ‘‘sandwich’’ that holds the collected plankton, are wound by rollers (12) and (3), passing through the comb (4) which prevents possible accidental winding on the cylinder (3) being wrapped by the spool (5), and
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Fig. 5. (A) Isometric view of the VOR. 1—Tow bar; 2—Entry of water to the probe compartment; 3—Hydrodynamic front end of the VOR; 4—Entry of water to the cassette; 5—Mounting bolt of the tow bar; 6—Propeller axis; 7—Propeller; 8 and 9—Rudder mounting screws; 10—Sustaining rudder, 11—Stabilizing fin, and 12—Access cover to the cassette and probe compartments. (B) View of the open VOR: 1—Instrument compartment; 2—Support for attaching equipment; 3—Dividing wall between the compartments; 4—Gearbox; 5—Cassette compartment; 6—Rod for locking and mounting the cassette, 7—Water inlet duct to the cassette and 8—Hole for entry of water. (Animation) (Link Dropbox: https://www.dropbox.com/s/36n9y3ybbhjyb4f/VOR. PDF?dl=0).
stored inside the fixation tank for the mesh containing organisms. It should be noted that the mesh is pulled through the cylinder (12) by its edges (13), in order to preserve the integrity of organisms
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Fig. 6. Internal metal components of the VOR 1—Propeller and bearing; 2—Gearbox; 3—Cassette; 4—Cassette mounting rod; 5—Tow bar mounting reinforcement; 6—Tow bar, 7—Adaptor for entry of water to the cassette and 8—Fixing clamps for probe and equipment.
collected through a gap built into the device. Fig. 7(C) shows the cassette already mounted with the two parts fitted in. Fig. 7(D) shows the passage of the water through the tunnel, and the silk feed operating system, as follows: (1) entry of water containing plankton; (2) covering layer of silk that joins with the filtering silk just above the tunnel; (3) filtering mesh; (4) storage spool and (5) filtered water outlet. 3.3. Sea trials with the VOR With the completion of the test at sea, it was possible to determine the best propeller pitch angle to ensure synchronicity between the displacement of the filter mesh and the distance navigated. With the constant speed in all the trawls at 7.6 knots, the first adjustment of regulation of the propeller blades at 45° resulted in displacement of the silk of 33 mm for the 5 nautical miles navigation, with the capture of thirty-eight zooplanktonic specimens. In the second trawl, the propeller pitch was changed to approximately 30°, resulting in displacement of 61 mm of silk and the capture of 99 specimens. Finally, in the third trawl, by adjusting the propeller pitch by 35°, displacement of 48 mm of silk was obtained at 5 NM navigated, with retention of 126 zooplanktonic specimens. The VOR also presents stable hydrodynamic behavior to the trawls carried out, due to the absence of both horizontal and vertical movements, observed through visual observation and with video records from on board the vessel. This is due to the fact that operation of the equipment in the initial phase of the trawls is very close to the surface, and also the rapid diving capacity as soon as the horizontal rudder is submersed (Fig. 8). 3.4. Collection protocol Batten and Burkill (2009) report discussions on the standardization and calibration of the methods used for the collection and analysis of data for continuous plankton samplings, but it should take into consideration that each research study or region has its own objectives, which must be met when using a method.
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Fig. 7. Open cassette. (A) 1—Entry of cassette; 2—Water tunnel protection grill; 3—Spiked cylinder mesh traction; 4—Mesh protection comb; 5—Filtered mesh collection spool; (B) 6—Lateral holding runner for the mesh; 7—Opening for passage of the mesh; 8—Sealing box for the cassette; 9—Lateral holding runner for the mesh; 10—Opening for passage of the filtering cover mesh; 11—Wall of the cassette; 12—Vulcanized cylinder to pull the mesh; 13—Traction edges of the vulcanized cylinder and 14—Upper spool for storage of the mesh; (C) Cassette mounted and (D) Functioning of the cassette system. 1—Entry of water containing plankton; 2—Covering mesh; 3—Filtering mesh; 4—Storage spool and 5—Filtered water outlet. (Link Dropbox: https://www.dropbox.com/s/7244ri76viyiseo/Cassete.PDF?dl=0).
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Fig. 8. VOR sea trials, with launch (1 and 2) and collection (3 and 4). (Link Video: https://www.dropbox.com/s/35ofhagcnp7u3bx/Lance%20do%20VOR.mp4?dl=0).
The creation of a protocol of procedures to be adopted aims to standardize and give conditions of reproducibility in collections with the VOR. For this, the use of a mesh with larger pore size of between (270 and 300 µm) will be considered, adapting it to the organism collection, the characteristics of the local biota, and the typical conditions of warm waters of the Brazilian coast.
• Before the start of the cruise, the cassette should be prepared with the mesh filter; • During the voyage, with the cassette prepared, the mesh should be demarcated at the place where the filtering will begin, with the words ‘‘INÍCIO’’ (start), the date and the number of trawls, and the bottom mesh should be positioned so that the line marking 5 nautical miles is positioned at the bottom of the water flow tunnel input; • When the VOR is launched into the sea, the record sheet should be used, noting down the VOR tow number, the vessel name, the name of the master of the vessel, the route of the vessel, and the person responsible for making the record. The date, times (launch and recovery of the VOR), operation of the VOR (launch or recovery), geographical coordinates, including longitude and latitude (specifying the abovementioned data), distance of trawling (nautical miles), speed of the vessel during the trawling (knots) and the weather conditions during the period of the trawl. These observations provide important additional information for interpretation of the data; • Soon after the equipment is removed from the water, the mesh is marked with a line on the traction cylinders, and the words ‘‘FIM’’ (end), to indicate the end of each tow and then the silk is removed from the storage tank; • The mesh should then be unwound from the final spool and spread out on a white surface, for a comparative reading of the color standard to estimate the phytoplanktonic density (color index for phytoplankton) (John and Reid, 2009). After reading the phytoplanktonic index, the mesh should be wrapped and tied with rubber bands, and stowed in a container containing correctly-buffered 4%
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J. Faccin et al. / Methods in Oceanography 9 (2014) 61–74 Table 1 Comparative table between VOR and CPR. Characteristics of the cassettes
VOR
CPRa
Area of water tunnel in mesh region (mm2 ) Width of spools (mm) Width of cassette (mm) Length of cassette (mm) Displacement of silk/mile (mm) Capacity of spool (m) Mesh compensation mechanism
2220
5100
115 136 270 10 6 Torque meter
155 200 300 10 5.7 Fusee wire
30 1.62 50 86 Fiberglass <10 Yes
90 1.62 40 100 Metal <20 Yes
Characteristics of the bodies Weight (kg) Opening (cm2 ) Width (cm) Length (cm) Construction material Operating speed (knots) Space for additional sensors a
Approximate values.
formalin solution to maintain the integrity of the sample. It is then sent to the laboratory, together with its respective records. In the laboratory, using the data in the record sheet, and assuming a constant towing speed, the mesh is unrolled, the number of records made is checked, and the samples are prepared for analysis. 4. Discussion A device was developed that is lightweight, easy to transport, and hydrodynamically stable under tow, with some characteristics that differ from the traditional CPR. The main innovations of the VOR are its fiberglass composite construction, its shape, and its interior divided into two compartments, one housing a probe to collect oceanographic data and the other for a plankton collector. The choice of U-Tow as a model for the layout of the VOR was due to its good hydrodynamic conformation and its ability to stow additional equipment, owing to the internal space. Hays et al. (1998) affirm that the U-Tow consists of a small sampling vehicle (<1 m in length), and may be towed at high speed (>10 knots), with a mechanism that enables undulatory function, but which has limited use in mesh plankton collectors, due to imprecision in the spatial identification of the occurrence of organisms. For the cassette of the VOR, the same principles as Hardy (1939) were adopted, i.e. a 1.62 cm2 opening followed by widening of the start of the water tunnel to give a cross-section diameter of (17 mm × 74 mm) 1258 mm2 , and in the region of the mesh, widening to (30 mm × 74 mm) 2220 mm2 , narrowing at the output to 1258 mm2 . With this configuration, the speed of the water passing through the mesh is reduced, minimizing damage to the morphology of the organisms collected. Table 1 shows some comparative values between the VOR and the CPR. The main characteristics of the new cassette include: its smaller size, making it lighter, smaller spools, but with the same or greater sampling distance and its innovative torque meter system, which replaces the fusee wire used in the traditional CPR. This replacement by a torque meter system facilitates its operation, as it does away with the need to rewind the fusee wire on board, with a steel wire. For the capture of organisms observed in the experimental trawls, it is suggested that the speed with which the silk passes through the rollers may influence the filtration efficiency and the counting process. However, the number of trawls carried out does not enable this trend to be confirmed, since variations in the abundance of plankton and towing speed, as well as the porosity of the silk, can also influence the counting (Batten et al., 2003). It would be expected that the counting in the VOR would be more pronounced, due to the more coastal area of operation and the smaller filtering area. However,
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this effect can be mitigated by the low operating speed (fishing boats) as well as the replacement, in the future, with a more porous mesh (270 µm). 5. Conclusions This paper presents a prototype of an oceanographic towing vehicle. This device has an innovative design feature, which is its hydrodynamic shape, giving it greater stability. Made from composite fiberglass, it is relatively lightweight yet robust, with reinforced internal structure, which makes it capable of withstanding rough handling on regional fishing fleet or research vessels as well as making it easy to deploy and recover. Due to its construction characteristics, it was possible to reduce the weight of the equipment from 90 kg (CPR) to just 30 kg (VOR), including the multiparameter probe and cassette, thereby reducing difficulties associated with its operation in smaller boats. Besides the reduced weight, it also has other improvements, such as the practicality of the innovative Torque Meter mechanism, providing a mechanical alternative to the fusee wire method used in the traditional CPR, making the system easier for the equipment operator to use, and facilitating its use on board. Whenever scientific equipment is placed on board fishing vessels, it is essential to clarify, for the owner and crew of the vessel, the importance and need for the implementation of the equipment, and that the data generated through this logistical support will be fed back, in the form of information and knowledge, for the benefit of the fishing industry. Among the various types of vessels in the region, trawlers, including tuna trawlers, or those with hydraulic winches, are recommended for the use of the VOR sampler, as these fishing methods generally have highest number of boats, with longer periods at sea, enabling a wider spatial sweep. With the use of the VOR in these vessels, it is also possible to carry out long-term studies for early detection of environmental anomalies in coastal and oceanic regions, as well as assisting in the interpretation of physical–chemical variables collected by other instruments currently used in oceanography (e.g. CTD). By coupling a multiparameter probe to the loading compartment of the VOR, it is possible to gather data on salinity, turbidity, pH, BOD, temperature, and chlorophyll-α , among other data, allowing for cross-referencing of the physical/chemical data and correlating them with the biological data obtained by the VOR. Our intention is to promote permanent use of this equipment by the Universidade do Vale do Itajaí (UNIVALI), particularly in fishing activities in their different modalities that operate from Santa Catarina (Brazil). The use of the equipment is also aimed at obtaining data, supporting projects for the formation of human resources at graduate, master’s and doctorate levels. The possibilities of making the equipment commercially available are not ruled out either, if there is demand. Acknowledgments We thank CAPES, in the scope of the IGEPESCA Project, Sea Sciences Notice of March 9, 2009 is the financial support and the CNPq for the productivity grant, Process 305910/2011-6. We are also grateful to the team of the Centro de Pesquisa e Gestão de Recursos Pesqueiros do Litoral Sudeste e Sul (CEPSUL) (Center for Research and Management of Fishery Resources in the South East Coast and South Coasts) for providing the Research vessel Soloncy Moura (Soloncy Moura Research Vessel) for use in the sea trials. References Batten, S.D., Burkill, P.H., 2009. Continuous plankton recorder surveys of the global oceans. PICES Press 17 (2), 20–21. Batten, S.D., Burkill, P.H., 2010. The continuous plankton recorder: towards a global perspective. J. Plankton Res. 32 (12), 1619–1621. http://dx.doi.org/10.1093/plankt/fbq140. Batten, S.D., Walne, A.W., Edwards, M., Groom, S.B., 2003. Phytoplankton biomass from continuous plankton recorder data: an assessment of the phytoplankton colour index. J. Plankton Res. 25 (7), 697. http://dx.doi.org/10.1093/plankt/25.7.697. Beaugrand, G., 2004. Monitoring marine plankton ecosystems. I: description of an ecosystem approach based on plankton indicators. Mar. Ecol. Prog. Ser. 269, 69–81. http://dx.doi.org/10.3354/meps269069. Beaugrand, G., 2005. Monitoring pelagic ecosystems using plankton indicators. ICES J. Mar. Sci. 62 (3), 333–338. http://dx.doi.org/10.1016/j.icesjms.2005.01.002.
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