Building a Floating Net Platform for Lobster 'grow-out' Aquaculture

[jamesmusslewhite]

   Well the additional bamboo lengths have been ordered and are presently being cut. I expect they will start being delivered sometime later this week. The bamboo used to build the frame which were shown in all the previous photos were harvested from a property owned by my business partner. So I could not post a market cost of the bamboo used in the construction of the frame pictured above. These 40 new additional lengths which will be used to construct the walkway around the main net enclosure are being purchased, which will allow me establish an accurate cost assessment for the bamboo material used for this project. Once I have collected all the additional bamboo lengths and have the bamboo walkway thoroughly lashed together then I can accurately calculate the total costs of bamboo, nylon line and labor used to construct the floating bamboo frame as well as a reasonable time assessment to complete such a project. I will later post all this information onto the thread.

   We also purchased a bundle of the netting which will be used to fabricate the main net enclosure and should be able to start cutting the net pattern later this week. The pattern will consist of four net sides and two net bottoms, the reason for two net bottoms pieces is that the net enclosure will have a double-layered floor. This enclosure will eventually house upwards of 800 market size Sub-adult individuals each weighing in access of 500grams, so fabricating this net enclosure to have a duel-layered net flooring is a reasonable precaution. The individual pieces of the net pattern will be sewed together using a heavy nylon fishing line

[jamesmusslewhite]

    Well I apologize for not updating the progress of this project but finding the right size bamboo needed for the platform had been difficult because larger bamboo is in really short supply in this area due to the two earthquakes back in March. The need for scaffolding and temporary housing has pretty much stripped the available supply this year, and the resource needs to to recover and grow, but bamboo grows quickly so next year it will be far more plentiful. But I have been steadily working on the project and so I have plenty to update and share with readers.  

   When I last spoke of the progress on the construction it was at this stage, so here is where I will pick back up and resume updating.

at this stage two things were happening at the same time while we were working on the platform. First of course was really hitting the 'bamboo network' to find the needed bamboo to complete the construction of the frame of the platform. And collecting the netting and associated materials to fabricate the three 'grow-out' nets, which I will show and explain later on in this thread.

   We are now ready to pull it out to deeper water and temporarily anchor it. This is so we can stop chasing all the little kids fixated and determined to climb all over the bamboo frame as if it is a combination 'Jungle-Jim' and dive-platform. We would often look up to see 50 or more children swinging all over the frame and combined their weight and stress could cause damage to the frame. Now once all the remaining bamboo and lashings are added it will of course will be far stronger. I had to wait a couple of weeks before I could pull the platform out to deeper water because owner of that capsized blue fish boat, which was beached in front of our front gate, could coordinate the logistics needed to ready the vessel to be towed to another location. We were only waiting for the weather conditions to be favorable. Once the vessel was removed I could then tow the platform to the space I had chosen and properly anchor it to the seabed.

the following photos show us moving the platform out of the way so the owner of the vessel could bring his crew in to remove his fishing boat.

and now that we are out of their way the boat crew can move in and remove the vessel out of our front yard were is has set for almost a year. And we can tow the bamboo platform into place where it will be anchored. I have interesting 'yard art'...  

[jamesmusslewhite]

   Once our platform was safely out of the work area the boat crew moved in to ready the boat for the tow.

 

the emptied all the water from the two fish holds and several used small fishing boats to pull the hull high enough to lash ropes and plastic drums on the bottom side, This would allow the hull to remain buoyant while preventing the hull to roll under by waves while being towed. It may not be pretty but it was effective as the boat made it safely several island away from and being pulled through the currents of the Surigao Straights. 

then we pulled it back over and lashed the frame to a coconut tree. The early the next day we made some weights and then pulled the platform out into deeper water several meters directly in front of our front-gate.

[jamesmusslewhite]

Now while we were in the process of building the platform there were some foul-weather days as well as down time for various reasons. This was when we worked on the 'grow-out' nets.

The 3-net 'grow-out' system which I designed to use on the platform. The requires a large 'grow-out' net which is designed to easily house 800 Adult (1,000 gram) size individuals.

basically the large 'grow-out' net is lashed to the top sides and bottom of the bamboo frame. The bamboo frame is suspended above the waterline by the buoyancy provided by the 55-gal. plastic drums which are mounted under the walkway.

the larger 'grow-out' net is used to house Latent-juveniles, Sub-adults and Adult size individuals and a net this size can easily house comfortably 800 (1,000 gram) Adult size individuals. This platform was designed to be used for research the developmental stages which range from early-stage Pueruli (clear) through 1,000-gram size individuals. To strictly observe the individuals through each of their many developmental stages and regularly chart weigh, carapace length and total length. To feed a diverse diet to determine fed preferences and monitor growth, weight gain, and exoskeleton luster and color; allowing the formulation of (developmental Stage) tailored diets. 

   I will also be deploying various Pueruli/early stage Juvenile 'live-capture' traps near our farm on Dinagat Island which will be quickly transferred to the platform and placed on one of two Nursery 'grow-out' nets'.

 

The first Nursery net is used to house early stage Pueruli which is a non-feeding stage. They will be housed in the enclosure and when they are close to Instar (moult) they will be isolated until they successfully transition and Instar (moult) to Algal-juveniles.

 

[jamesmusslewhite]

   Algal-juveniles can be quite aggressive and prone to cannibalism which is why they must be removed  from the first Nursery 'grow-out' net' and relocated to the secondary Nursery 'grow-out' net.

   Here inside this enclosure the young Algal-juveniles will remain and continue to develop. These individuals are simply too aggressive and cannibalistic to remain housed with the Pueruli stage individuals, but are simply too underdeveloped to be housed among the latent-juveniles, Sub-adults and Adults. They will remain in this enclosure until they have developed to 70-gram Post-algal size individuals where they will be relocated to the main 'grow-out' net enclosure.

   The large main 'grow-out' enclosure houses latent Post-algal, Late-juvenile, Sub-Adult, and Adult size individuals. As I mentioned earlier this large net can comfortably house 800 (1,000 gram) Adult size individuals, so when the time comes that the net capacity proves insufficient, I will have already built a second floating platform which will be used to house latent Sub-adults and Adult individuals.

       

   This photo shows the frame of the first Nursery 'grow-out' net and the netting being readied so it can be lashed to the PVC frame. If you look closely you will notice there is a divider as this is actually two nets in one. The pueruli are housed in the larger section. The second section is for latent Pigment-pueruli so they can be isolated before they Instar (moult) and transition to young Algal-juveniles. This isolation is for two reasons. 1.) is that after they successfully Instar (moult) their new exoskeleton is so soft that for the first 10 hours it will not the weight enough to stand. The exoskeleton will need 7-10 days to properly harden. During this time that can be adequately feed as they were previously in a non-feeding phase. 2.) if left among the Pueruli they would prey on the Pueruli, but if latent Pigment-pueruli are put in the second 'grow-out' net to moult they will quickly become prey themselves. 

   This photo shows the size of the net Nursery 'grow-out' nets. My wife stands 5 foot so it is easy to gauge the dimensions of the net.

   And this is a photo of the first 'grow-out' net being readied to be towed to the Floating Platform. The two 'grow-out' nets float inside the main 'grow-out' net and held in place using a singe line of nylon cord. When not in use during they are simply removed, thoroughly cleaned  and stored on-land and should provide many years of dependable service. 

 

[jamesmusslewhite]

Well at the point of this posting I had more bamboo delivered, cut and temporarily lashed as decking, unfortunately we have only found enough to complete two sides of the walkway but it is still enough to do the trick. We pulled the platform approximately 12-15 meters out from the shore directly across from our front gate and tied a mooring rope to a coconut tree. We used doubled-rice sacks as anchors, 5 sacks to an anchor line and one anchor line at each corner of the platform. This is to prevent the platform from twisting at low-tide during stormy weather.

Using the mooring line to the tree also helped to maintain a prospective of 'square' when out in the boats trying to plumb the platform to the island. the current flows in opposite directions, determined by the tides, so the platform drifts. So it makes it more difficult using paddle boats to determine exactly where to drop the first two anchor lines. The mooring line is a huge help as the platform could be easily corrected by one boat while the other boat could drop the anchor lines.   

  

   As you can clearly see the anchor line is far from being high-tech. You paddle out and push the rice sack out which is connected directly anchor line. These sacks are filled with rocks and cement chunks and weigh 70-90 (kilograms) each.

   Now it gets suffocated... A piece of rope is tied tightly around the neck of the sack, and tightly tied as to have a strong rope loop. Then a medium size stone is placed inside the neck and above the stone the sack is firmly tied. These typed of anchors then has the anchor line threaded through the loop, and then the sack is dropped into the water where it slides down the anchor line were it rests on the seafloor. Four of the type of anchors are used on all four corners of the platform. 

   The whole process is really simple and new quality rice sacks are sold in most wet-markets. Double or triple the sacks so the will last.

 

[jamesmusslewhite]

   How many rednecks would live to have a piece of yard-art like that just outside their front door?

Well it was time to start lashing down the large 'grow-out' net. For readers who have interest in building their own floating nets there is something you need to know. Currents and wave-action will cause a net to sway from side-to-side and nets will naturally sag in the middle making your square net akin to a limp cock. This opens all kinds of issues you want to avoid. The solution is easy if it is done right, but many sources (drawings) show a pretty picture but are made by people who actually do not have a clue about nets. A prime example is this drawing found in the internet. 

   One is the placement of barrows as they need to be elevated if you notice I use elevated supports to raise the frame much higher. This helps compensate for the (wet) weight of the netting and lifts the frame higher above the wave-action. This helps moderate waves from washing over the top of the walkway  decking which can cause structural damage. The drawing also minimizes the need for strong top-rail to raise the sides of the net. During storms lobster will actually climb up to the edge of the water line, which means if waves are washing over your walkways and slamming into your nets. There is a reasonable possibility the net poles will quickly fail. And if that happens those clever little sea bugs will be surfing those waves to freedom.

   Also and more important they imply attaching sag-weights directly to the bottom of the net edges which increase the chance of rips and tears in the netting. This is because wave action will cause those sag-weights to erratically sway and pop against netting. The next drawing is my own and shows the proper way to attach sag-weights.

    The sag-weights are not connected directly to the bottom edge of the netting. Instead the sag-weight is extended by a line attached to platform frame, slightly wider than the bottom if the netting. This slight tugs the bottom straight and flat. What the drawing does not show is that under the net there are cords are also tied to the saw-weight which is directly across from it. This creates a cris-crossing of support lines adding support to the net floor which helps prevent the net from excessive sagging. If you have several hundred individuals as weight 500-grams each then net-sag can really be an issue.

 

   Here the main 'grow-out' net was being lashed down and the sag-weight lines were being tied to the bottom of the platform frame at the same time. The sag-weights are just a lighter version of the anchor weights, each sag-weight weighing approximately 10-13 kilograms.  

   This Youtube video of mine clearly shows the sag-weighs and anchor lined under the water-line.

 

[jamesmusslewhite]

   The 'Tiger' lobster are tasty little sea-bugs, but at 3,000php they are expensive critters . We have a 600 meter net which gets dropped in the water just offshore here, when the wind and water conditions are right. In the last 4 weeks we caught two mature 'Tiger' lobsters (800 gram) and (900 gram) in that net. This is the (900 gram) critter pictured here.

 

 

but the net has also yielded a few few (eaten size) of another type of tasty lobster.

 

This little jewel is a Thenus orientalis (Brown Slipper Lobster) and I find to be as tasty or even more tasty than the 'Tiger' lobster, and these we get to actually eat. I ate my Tigers when raising them as a mere hobby, but now they are a business and one should never eat their profits.

this is what their underside looks like.

   I am actually thinking of also trying to raise these from eggs. They have a considerably shorter larval period and they can grow to a weight of 2 kilogram and they are tasty. Their diets are similar and can be raised on the same platforms just in separate nets.

   These little bad boys were caught within 200 meters of this island are 'Mantis shrimp'  the Filipinos call them tatampal, hipong-dapa or alupihang-dagat and a whole host of really bad words if the careless when handling these little tasty thumb-spliters can not be held enclosed in 'grow-out' nets because they can literally slice through the netting and escape. So it will be a while before I can build a few tanks on a separate 'closed-circulation system, perhaps in a few years from now. I have yet tried eating one of these sea-bugs, so I can not tell you from personal experience what they actually taste like, but the locals love them and they sell for 1,200php per kilo here locally. But since shrimp and crabs are abundant here I have then in my diet quite often.

I love living in this area of Northern Mindanao...    

Edited September 28, 2018 by jamesmusslewhite

[jamesmusslewhite]

      With floating nets they require sag-weights suspended from the bottom edge of the netting to help prevent the netting to sag in the middle like a big wet sock. The bigger the net, the bigger the problem. This issue is compounded in seawater due to tidal currents. In ponds and lakes there are winds and wave-action but minimum currents. If one uses floating cages in rivers and streams currents are an issue which is drag. Large surfaces no mater now light create drag, and the larger the surface the larger the drag. Any cubed ring around the bottom of a net, despite material type, will create drag forces. A few rope lines and small bags of rocks have a minimum drag. This is a diagram showing the rope and weight configuration.

   As you can see this is an excellent light weight solution with a minimum current drag. It also removes the weight of the sag-weights on the ropes suspended to the under-frame of the platform, removing the weight off the 'grow-out' net. The bottom of the net area sits directly on the support ropes, and the weight placed on the bottom is distributed into 16 smaller surfaces instead of just one large surface area. This is important with a net this size as it will house hundreds of Adult lobster easily weighing a kilo each, which are free-roaming over the bottom of the enclosure.

[Old55]

Thank you for sharing James very informative. Good luck in your endeavors.