Abstract:
A method and system for efficient and eco-friendly shrimp skimmer trawling by a trawling vessel with a trawl net, skimmer booms, net arms, and buoyantly adjustable rollers to maintain trawl net height and net opening without damage to the ocean floor allowing for systematic and frequent retrieval of catch while continuing trawling operations in intervals short enough to prevent death of by-catch and endangered species and where the system is fully storable on trailerable trawling vessels for maintenance of allowable highway heights. The system and method has the upper edge of the trawl net held above the ocean surface while the trawling vessel moves forward.

Description:
BACKGROUND 
       [0001]    This invention relates to improved methods and equipment for trawling, and more particularly to an improved method of shrimp trawling to minimize and eliminate the destructive effects of bottom trawling commonly used to trawl for shrimp in coastal regions, particularly in the Gulf of Mexico. 
         [0002]    Present shrimp trawling methods typically involve two nets with forward booms pushing the net bottoms below the boat with a heavy bullet for each net used to hold the trawl nets on the sea bottom and keep the mouth of the trawls open as they are pushed or pulled by the trawling vessel. These bullets weigh as much as 800 pounds each. At the outboard end of each net boom is a sled weighing approximately 100 pounds. The net booms are fastened to the deck of the trawling vessel approximately one third of the vessel length aft from the bow. Because of this configuration, the nets are actually under the trawling vessel and propellers resulting in longer times for turning to avoid drawing the nets into the propellers. Along with the destruction to the sea bottom caused by these devices, the bottom edge of the trawl nets being dragged along the sea bottom continually breaks up any vegetation or aquatic life forms on the bottom and causes the release of sediment. This destructive effect is particularly severe in relatively shallow coastal areas trawled for shrimp and has led to the accelerated loss of coastal wetlands. 
         [0003]    All around coastal lakes and bays were vast regions of low land inaccessible to trawler boats. When these low lands were made accessible by storms and hurricanes, trawler vessels began using the system described above with increasingly heavier bullets and sleds, churning up sediment causing untold tons of sediment to wash into the ocean with each falling tide. This practice has continued for at least half a century greatly contributing to the loss of coastal lands. In particular, the bottoms of coastal Louisiana bays and lakes are now 8 to 10 feet deeper. 
         [0004]    Another detrimental effect of the use of these heavy devices is the need for increasingly large and more powerful trawling vessels to move larger trawl nets with heavier bullets and sleds. Incidental to this increase in size is the added time necessary to pull the trawl nets to unload catch as well as the death of unwanted species commonly called by-catch due to the extended time between pulling of the trawl nets. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to eliminate the negative aspects of the present method and equipment used in trawling, particularly shrimp trawling in relatively shallow coastal waters such as along the Gulf of Mexico. 
         [0006]    It is an object of the present invention to provide a more efficient and environmentally friendly system and method for trawling with the adaptability to trawl at various levels or water depth ranges suitable to the species being trawled. For example it is well known that “brown” shrimp are trawled during a May spring season near the bottom, whereas “white shrimp” season is later in the year but this species is trawled at all depths or columns of water. 
         [0007]    It is a further object of this invention to eliminate heavy boards, bullets or sleds, thereby reducing the power and size of trawling vessels, and also reducing the amount of labor needed to pull the trawl net on a continuous short cycle, thereby eliminating the need for turtle excluders because the turtles would be removed from the water quickly. Likewise, by-catch or unwanted species would be returned to the sea while still alive. 
         [0008]    It is a further object of this invention to provide a true skimming trawl that would allow the catch to be retrieved and dumped on the deck or fantail of the trawling vessel in intervals of as little as five minutes while continuing to trawl. This frequent retrieval of the trawl would allow faster sorting of the catch and return of by-catch to the sea. This is in contrast to the present practice of trawling literally for hours and then retrieving heavily laden trawl nets and spending an equally long time sorting through hundreds and hundreds of pounds of catch and dealing with the now dead by-catch. In addition, this present practice dictates that trawling ceases while the catch is handled. 
         [0009]    It is an object of this invention to provide a skimming trawl net mounted on a trawling vessel with right and left retractable skimmer booms pivotally mounted at the stern of the trawling vessel, with a net arm mounted to each boom and a buoyantly adjustable roller mounted in a gimbal at the lower end of each net arm, and having a trawl net being pulled behind the trawling vessel so that the net cannot get into the vessel propeller, with a mouth having a top edge and a bottom edge with the ends of the top edge attached to the outboard ends of the skimmer booms and the ends of the bottom edge attached to the bottom of the net arms. It is further intended that the trawl net have a bag end, a bag loop for tying off the bag and a tag line for pulling the bag loop tight and also retrieving the catch in the bag by raising to the fantail of the vessel for dumping. 
         [0010]    It is a further object of this invention that the inventive skimming trawl system be retractable for storage on the trawling vessel without disassembly and the stored system and vessel would not exceed highway height limits for transporting on a trailer on any truck route. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a rear perspective view of a trawling vessel equipped with the inventive skimming trawl system. 
           [0012]      FIG. 2  is a perspective view of a buoyant watertight roller mounted on the bottom end of each net arm attached to a skimmer boom. 
           [0013]      FIG. 3  is an overhead view of a trawling vessel equipped with the inventive skimming trawl system moving forward with a skimming trawl net deployed. 
           [0014]      FIG. 4  shows the bag end of the skimming trawl net being tied off by a tag line to retain the catch before retrieval to the trawling vessel. 
           [0015]      FIG. 5  shows the bag end of the skimming trawl net being retrieved by the tag line after being tied off. 
           [0016]      FIG. 6  is a rear perspective view of a trawling vessel equipped with the inventive skimming trawl system showing the skimmer booms being raised for placement in a storage position for travel. 
           [0017]      FIGS. 7 and 8  show the turning of the booms to set in place for travel. 
           [0018]      FIG. 9A  is a side view of a trawling vessel equipped with the inventive skimming trawl system on a trailer with skimmer booms in place for travel. 
           [0019]      FIG. 9B  is a side view of a trawling vessel equipped with the inventive skimming trawl system on a trailer with skimmer booms in place for travel showing the trawl net rolled and lashed to the skimmer booms. 
           [0020]      FIG. 10  is an overhead view of a trawling vessel equipped with the inventive skimming trawl system with both skimmer booms stored for travel. 
           [0021]      FIG. 11  is an overhead view of a trawling vessel equipped with the inventive skimming trawl system with one skimmer boom stored for travel. 
           [0022]      FIG. 12  is a perspective view of a trawling vessel equipped with the inventive skimming trawl system with both skimmer booms stored for travel. 
           [0023]      FIG. 13  is a rear perspective view of a trawling vessel showing details of the boom mast. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    In  FIG. 1 , a trawling vessel  1  equipped with the inventive skimming trawl system  100  is shown from a rear view with a right skimmer boom  10  and a left skimmer boom  11  each having an inboard end and an outboard end and deployed and supported by boom cables  13  supported on a boom mast  12 . Also shown is a boom support frame  30  with right and left support posts,  31  and  32  respectively along with a boom support frame brace  33 . The boom cables  13  are drawn through right and left boom lifting pads  20  and  21  through right and left cable pulleys  24  and  25  respectively. There is a right and left skimmer boom pivot  22  and  23  respectively on the fantail  29  in proximity of the stern  49  of the trawling vessel  1  to receive the inboard ends of the right and left skimmer booms  10  and  11 . Fixed to the outboard end  10   a  of the right skimmer boom  10  is the upper end  14   b  of a right net arm  14  and fixed to the outboard end  11   a  of the left skimmer boom  11  is the upper end  15   b  of a left net arm  15 . 
         [0025]    At the bottom end  14   a  of the right net arm  14  is a right roller gimbal  16  mounted with a right roller  8 . At the bottom end  15   a  of the left net arm  15  is a left roller gimbal  17  mounted with a left roller  9 . 
         [0026]    As is apparent from  FIG. 1 , the right and left skimmer booms  10  and  11  respectively with their respective attached right and left net arms,  14  and  15 , can be lowered or raised on their respective boom pivots  22  and  23  by boom cables  13  to accommodate different water depths so that the right roller  8  and the left roller  9  would roll on the sea bottom. 
         [0027]    Also shown in  FIG. 1  is the trawl net  3  with a forward net mouth held in a substantially rectangular shape with two upper corners and two lower corners by the right and left net arms. The two upper corners of the net mouth are attached at the upper ends  14   b  and  15   b  of the net anus  14  and  15 . The two lower corners of the net mouth are attached at the lower ends  14   a  and  15   a  of the net arms  14  and  15 . There is a net mouth upper edge  19  with a right and left end. The net mouth upper edge  19  is also commonly called a cork line in that it is fitted with corks or other buoyancy devices to keep the net mouth upper edge  19  at or near the surface of the water. At both the right and left ends of the net mouth upper edge  19  are lines fed through double pulleys  52 , one mounted on the right to the upper end  14   b  of the right net arm  14  and one mounted on the left to the upper end  15   b  of the left net arm  15 . Also shown on the forward net mouth is the net mouth lower edge  18  with a right and left end. The net mouth lower edge is also commonly called a lead line in that it is fitted with lead weights to keep the net mouth lower edge  18  at or near the sea bottom  37 . At both the right and left ends of the net mouth lower edge  18  are lines fed through double pulleys  51 , one mounted on the right to the right roller gimbal  16  and one mounted on the left to the left roller gimbal  17 . These lines from the right and left ends of the net mouth lower edge  18  are then fed the double pulleys  52 . The lines from both the right and left ends of the net mouth upper edge  19  and the right and left ends of the net mouth lower edge  18  are then led from the double pulleys to right and left cleats on the deck of the trawling vessel  1  for lashing of these lines. There will be at least one cleat on the right and left side of the trawling vessel  1  for the lines from the net mouth upper edge  19  and at least one cleat on the right and left side of the trawling vessel  1  for the lines from the net mouth lower edge  18 . These lines from the ends of the net mouth upper edge  19  and the ends of the net mouth lower edge  18  allow the trawl net  3  to be disconnected from the trawling vessel  1  in the event that the trawl net  3  becomes snagged or entangled on an obstruction on the ocean bottom. Once disconnected, the net mouth upper edge  19  will float and the location of the trawl net  3  can be marked with a flotation device for retrieval. 
         [0028]    It is understood that the actual length of the net mouth upper edge  19  is generally less than the distance between the upper double pulleys  52  and likewise the actual length of the net mouth lower edge  18  is generally less than the distance between the lower double pulleys  51 . The actual distances will depend on the angle of deployment of the right and left skimmer booms  10  and  11  as required for the rollers  8  and  9  to roll on the sea bottom  37  at a particular water depth. The lines running from the corners of the net mouth upper edge  19  through the pulleys  52  and the lines running from the corners of the net mouth lower edge  18  through the pulleys  51  can be used to adjust the shape and tautness of the net mouth upper and lower edges  19  and  18  during the trawling operation. 
         [0029]    Also shown in  FIG. 1  is a tickler chain  50  with a right and left end in front of the net mouth lower edge  18 . It is intended that the tickler chain  18  is pulled along the sea bottom ahead of the net mouth bottom edge  18  to cause shrimp to jump up and be swept into the moving trawl net  3 . The right and left ends of the tickler chain  50  are fed through the lower double pulleys  51  mounted on the right and left roller gimbals  16  and  17  respectively. The right end of the tickler chain  50  is then led to a right lashing cleat on the deck of the trawling vessel  1  and the left end of the tickler chain  50  is then led to a left lashing cleat on the deck of the trawling vessel  1 . 
         [0030]    Also shown in  FIG. 1  is a plurality of trawl net lashing lines  40  hanging from the bottom edge  10   b  of the right boom  10  and from the bottom edge  11   b  of the left boom  11 . These lashing lines  40  are used to lash the trawl net  3  when the net  3  is retrieved and bundled for storage and transit. In addition, there are shown two boom restraining lines  38  and  39 , each with a forward end attached to the bow of the trawling vessel  1  and an aft end attached to the bottom end  14   a  of the right net arm  14 , and the bottom end  15   a  of the left net arm  15  respectively. These boom restraining lines  38  and  39  hold the right skimmer boom  10  and the left skimmer boom  11  in position while the trawling vessel  1  is moving forward in deployment of the inventive skimming trawl system  100 . 
         [0031]    At the forward end of the trawling vessel  1  is also shown a forward boom storage frame  41  with a right post  42  and a left post  43 . On the right post  42  is a right boom support hook  44  for storage of the right boom  10  and the right net arm  14 . Likewise, on the left post  43  is a left boom support hook  45  for storage of the left boom  11  and the left net arm  15 . 
         [0032]    As shown in the  FIGS. 1, 3, 4 and 5 , the trawl net  3  has an elongated tapering shape that ends in a bag  36  at the aft end of the net  3 . For purposes of emptying the bag, the aft end of the net is cinched closed by suitable lashing that can be released to empty the bag on the fantail  29  of the trawling vessel  1 . On a larger vessel, the bag  36  may be emptied on the vessel deck. In the inventive trawling system  100 , as the trawling vessel moves forward with the net  3  deployed and configured as shown in  FIG. 1 , the desired catch and by-catch are trapped in the bag  36 . At a distance forward of the aft end of the net  3 , is a bag loop  35  configured to close the bag by use of a tag line  34  pulling from the support mast  12  through a tagline pulley  53 . When the tag line  34  is pulled, the bag loop  35  tightens around the net  3  and secures the desired catch in the bag  36 . Typically a series of rings may be sewn around the net  3  at the location of the bag loop  35  and the tag line  34  threaded through the rings. Once the bag loop  35  is tightened, the tag line  34  continues to be pulled and the bag  36  is drawn up and over the fantail  29  and the catch released or dumped on the fantail  29  by unlashing the aft end of the net  3 . The aft end of the net  3  is then relashed and the tag line loosened to allow the bag  36  back into the water with the bag loop  35  untightened. It is intended that this retrieval and emptying of the catch in the bag  36  and return of the bag  36  to the water be done while the trawling vessel continues to move forward catching shrimp in the forward portion of the net  3 . When the bag  36  is returned to the water any catch in the forward portion of the net  3  will be swept back into the bag for the next retrieval cycle. 
         [0033]      FIG. 2  shows a perspective view of the left roller  9  mounted in the left roller gimbal  17  affixed to the bottom end  15   a  of the left net arm  15 . As shown the roller  9  has a right end  26   a  with a right roller pin  26  inserted into the right arm  17   a  of the left gimbal  17 , and a left end  27   b  with a left roller pin  27  inserted into the left arm  17   b  of the left gimbal  17 . In one or both of the ends  26   a  or  27   b  is an access plug  28 . It is understood that the right roller  8  is mounted in similar fashion in the right roller gimball  6  affixed to the bottom end  14   a  of the right net arm  14 . 
         [0034]    The access plug  28  allows the roller  9  or  8  to be filled fully or partially with water to adjust the buoyant properties of the rollers  9  and  8 . 
         [0035]    In practice the inventive system  100  has been implemented on a relatively small 26 foot trailered vessel with a 40 foot net without boards or bullets and can be designed to handle at least a 50 foot net. Using the trawl net as a skimmer is fast and efficient allowing for frequent pulling of the net bag. 
         [0036]    On a 26′ by 8′ test vessel, when the outboard end of a skimmer boom  10  or  11  with attached net arm  14  or  15  and roller  8  or  9  respectively is placed on a scale, the weight is approximately 90 lbs. A roller 2′ long and 12″ diameter will float approximately 80 lbs of weight, so the net weight rolling on the sea bottom is only 10 lbs. 
         [0037]    An overhead view of a trawling vessel  1  equipped with the inventive skimming trawl system  100  is depicted in  FIG. 3  pulling the trawl net  3  as the vessel  1  moves forward from right to left. As shown the right skimmer boom  10  and the left skimmer boom  11  have been swung outboard on their respective pivots  22  and  23  to a position approximately transverse to the direction of motion of the vessel  1 . The right and left skimmer booms  10  and  11  with their respective net arms  14  and  15  are restrained from swinging further aft by a right boom restraining line  38  and a left boom restraining line  39  respectively with the forward end of each restraining line  38  and  39  attached to the vessel  1  at the bow. The aft end of each restraining line  38  and  39  is attached to the bottom end  14   a  of the right net arm  14 , and the bottom end  15   a  of the left net arm  15  respectively. 
         [0038]    While not shown in  FIG. 3 , it is intended that the net mouth top edge  19  or cork line be above the water line at the trawler stern  49  below the fantail  29  when trawling. As shown in  FIG. 6 , there are two cork line lift lines  58  attached to the net mouth top edge  19  and fed through starboard and port transom loops  54  and  55 . These lift lines  58  are used to lift the net mouth top edge  19  to the trawler stern  49  and the lift lines  58  are then secured to cleats on the deck of the trawling vessel  1 . 
         [0039]    Also depicted in  FIG. 3  is the deployed trawl net  3  with the net mouth top edge  19 , the net mouth bottom edge  18 , the net bag  36  at the end of the net, the bag loop  35 , and the tag line  34 . 
         [0040]      FIGS. 4 and 5  depict the steps involved in tying off the bag  36  at the bag loop  35  with the tag line  34  and then retrieving the bag  36  loaded with catch by continuous pulling of the tag line  34  from the tagline pulley  53 . 
         [0041]      FIG. 6  depicts the raising of the skimmer booms  10  and  11  for placement on a forward boom support frame  41  for storage and travel.  FIGS. 7 and 8  show the inward turning of the left skimmer boom  11  before storage on the boom support frame  41 , in order to have the left net arm  15  as close to the port side of the trawling vessel  1  to minimize width for purposes of transporting the vessel  1  complete with skimmer booms  10  and  11 , net arms  14  and  15 , rollers  8  and  9 , and furled and lashed net  3 , all on a trailer  48  for highway travel as shown in the side view of  FIG. 9B . It is specifically intended that the net  3  be stored with the skimmer booms  10  and  11 . As shown in  FIG. 9A , the left skimmer boom  11  is cradled in a left boom support hook  45  mounted on the left post  43  of the forward boom storage frame  41  at the forward end of the trawling vessel  1  near the bow  46 . Also shown on the bow is a padeye  47  for the boom restraining lines  38  and  39 . The boom support cable  13  is also shown connected to the left boom lifting pad  21  and the left boom cable pulley mounted on the boom mast  12 . 
         [0042]    As shown in  FIG. 6  there is a starboard fantail hook  56  on the starboard aft outboard corner of the fantail  29  and a port fantail hook  57  on the port aft outboard corner of the fantail  29 , along with the two cork line lift lines  58  attached to the net mouth top edge  19  and two lead line lifting lines  59  attached to the net mouth bottom edge  18 . While not shown, similar lift lines would be provided for the tickler chain  50 . 
         [0043]    Upon completion of trawling with the inventive trawl system and method, the tag line  34  would be used to retrieve the bag  36  at the aft end of the net  3  and hoist the bag  36  up the support mast  12  on the tagline pulley  53 . In addition the tapered portion of the net  3  forward of the bag  36  would be bundled, lashed and also lifted up the support mast  12  and draped above the fantail  29 . At this point, the cork line lift lines  58  would be loosened from the transom loops  54  and  55  and the net mouth upper edge  19  hooked in the fantail hooks  56  and  57 . The lead line lift lines  59  would be used to lift the net mouth lower edge  18  and hook it in the fantail hooks  56  and  57 . Similarly the tickler chain  50  would be lifted and hooked in the fantail hooks  56  and  57 . With the net mouth upper edge  19 , the net mouth lower edge  18 , and the tickler chain  50  all hooked in the fantail hooks  56  and  57 , and the aft end of the net  3  and the bag  36  draped from the support mast  12 , the remainder of the net  3  will now float on the surface of the water behind the trawling vessel  1 . The right and left skimmer booms  10  and  11  can then be lifted by the boom cables  13  allowing the net  3  to be gathered and bundled for lashing to the booms with lashing lines  40 . Once lifted the skimmers booms  10  and  11  can then be swung forward with the lashed net  3  and placed in the respective support hooks  44  and  45 . Once the booms  10  and  11  are placed in the respective support hooks  44  and  45 , any net  3  still hanging can be lashed to the booms  10  and  11 . 
         [0044]    When the trawl net  3  has been stowed the right skimmer boom  10  with the attached right net arm  14  and the left skimmer boom  11  with the attached left net arm  15  can be swung forward on their respective boom pivots  22  and  23  and stored on the right and left sides of the trawler  1  and inboard of the trawler sides. This allows the trawler to maintain allowable heights for trailering on the highway. 
         [0045]      FIG. 10  shows an overhead view of the trawling vessel  1  with both skimmer booms  10  and  11  in the stored position and cradled on the forward boom storage frame  41 .  FIG. 11  shows an overhead view of the trawling vessel  1  with only one skimmer boom  10  in the stored position and cradled on the forward boom storage frame  41 , while the other boom  11  is being pulled into storage position with the use of the left boom restraining line  39 . 
         [0046]    In  FIG. 12 , a schematic perspective view shows both skimmer booms  10  and  11  cradled in their respective support hooks  44  and  45 . As shown in  FIG. 9B , it is understood that the trawl net  3  would be rolled up and lashed with the lashing lines  40  and remain attached to the booms  10  and  11  and net arms  14  and  15  for storage and travel. 
         [0047]      FIG. 13  shows a rear perspective view of a trawling vessel  1  showing details of the boom mast  12  with a top mounted tagline pulley  53 .