Why using nets? Most of Kappaphycus and Eucheuma cultivation, throughout the world, is made on long lines, with lines fixed at the bottom or floating lines. Is that to avoid fish graziong? Then, it is a compromise between grazing and fouling. Which one has less impact(s) of your harvest (biomass and time for harvesting)?

By the way, Happy New Year to you and all on this discussion!

1-galvanized chain link mesh for the main fish netting to reduce marine fouling and subsequent maintenance and cleaning

2-rigid plastic, galvanized or plastic coated steel

3- In the marine environment, the antimicrobial/algaecidal properties of copper alloys prevent biofouling, which can briefly be described as the undesirable accumulation, adhesion, and growth of microorganisms, plants, algae, tube worms, barnacles, mollusks, and other organisms on man-made marine structures. By inhibiting microbial growth, copper alloy aquaculture pens avoid the need for costly net changes that are necessary with other materials. The resistance of organism growth on copper alloy nets also provides a cleaner and healthier environment for farmed fish to grow and thrive. In addition to their antifouling benefits, copper alloys have strong structural and corrosion-resistant properties in marine environments.

Well thanks for the ideas!

I have attached photo of the tube net (full grown) for understanding. The method is devised not for avoiding fish grazing, but for making it more flexible in the open sea. The waters along the west coast of India are rough and any other method like long line, rafts - which are in practice elsewhere - hinders expansion to commercial level.

My question is rather to material chemists which can suggest some addition to the formulation of polypropylene base material which is being used by net manufacturers. The other treatments would increase the cost.  

I too extend the new year wishes to all the members. 

I would say stay away from copper-based materials/paints. In many jurisdictions/countries, copper-based materials/paints are now banned because of copper toxicity to the target species but also to non-targeted species. I am sure you will have, then, to do copper analyses to show that your seaweeds are still safe, and that will be expensive.

What fish aquaculturists are doing now is rotating their nets, designing robots to clean their nets, etc. but these strategies are very expensive, with a lot of infrastructure investments, and are still justifiable when the species harvested yield a much higher price per kg or tonne (western world approach, I would say). Then, it becomes an economics calculation to be made.

The picture you included does not show much fouling. Then, would it not be a strategy of compromise? When (number of weeks) do I get the most harvestable biomass before fouling become a large issue? Should I harvest more often good quality Kappaphycus, even in lower quantity, and reset/clean the system before fouling "contamination" become too much of an issue? These are practices to test with farmers to check which ones are the most productive and financially interesting.

I have had good productivity in a circular "drum-like" design which could be up to 1 meter in diameter,  with a spoke up the middle and some medium size net as the base material, held by a wheel at each end, which allowed rotation of the drum. The spike attached to two fixed ends, driven down into the sediment on pipes and attached by ropes, This allowed the entire cage to circulate with tidal flow and with currents or winds. Thus , the fouling algae would be constantly moved and not get an attachment, and also sometimes not have adequate light .

This also  tended to clean the interior plants I was growing. Also try to put them into a current or tide situation in general to derive maximum nutrients and oxygenation and taking excess nutrients away from the growing plants.

It is the same experience with us in culturing seaweeds in a lagoon.  We also cover the seaweeds by fishing nets to avoid fish grazing, especially from rabbit fish.  So we visit our seaweeds culture areas 2-3 times a week, shaking the long line rope to clean the fouling materials.  This needs an extra job, but give a good harvest. 

It is the same experience with us in culturing seaweeds in a lagoon.  We also cover the seaweeds by fishing nets to avoid fish grazing, especially from rabbit fish.  So we visit our seaweeds culture areas 2-3 times a week, shaking the long line rope to clean the fouling materials.  This needs an extra job, but give a good harvest. 

Theirry was right that seaweeds are usually succesfully grown on hanging/flouting lines. We experience here in the Philippines that if the volume of your cultured seaweed seedlings is relatively few, it would be vulnerable to grazing. Site selection is also a factor, wherein you choose your  growing areas far from the downstream effect of the upland activities. Where nutrients would likely increase and thus also increase the possibility of enhancing the growth of fouling organisms.

Another technique that we used to respond to fouling net problems was to design the net in such a way that one side of the net wall would be above the water surface allowing it to sun dry through time. After this surface have dried, turn another side of the net for subsequent drying. Another solution was to have extra cages, where you periodically change the cage for sun drying.

Hope this is of some help. Good Luck!!!

I am currently testing Hypnea charoides on longlines and it has become clear that while growth is good, in rough conditions biomass is lost as parts of the plant break away. Vaibhav your tube net presents an interesting alternative that should minimise loss - I may try this technique too. 

At our IMTA location we have the flexibility to make use of fish pen areas and so it is possible to  culture seaweeds of similar morphology free-floating in polyethylene surface cages. The cages can be rotated frequently to reduce biofouling and will also substantially limit loss due to bad weather. I'm looking forward to testing this method in the coming weeks. Some pictures are attached and if you have any thoughts on this idea some feedback would be much appreciated.

Its being interesting discussion so far.

I do agree with Prof. Chopin, any chemical that is toxic in nature should be avoided. I am tying up with one of my chemistry colleagues in India for developing new polymer material. I have provided the picture above of fully developed biomass and the tube is periodically cleaned.

There is yet another interesting fact, the tubes fouled (more) in initial phase of seedling growth - lets say 10 to15 days - of typical 45 to 50 days growth cycle. The algal fronds once protrude out from tube hinder the attachment substantially.

I am looking at solution at commercial level where high manpower cost is required for cleaning. We have tried several methods of farming and tube net seems to be best in high energy waters of Gujarat. 

Reece, tube net is also being used by Prof. Renata and her group in Brazil, please read the relevant literature, should you have specific queries, please do not hesitate to contact me.      

It is indeed an interesting discussion. Do you all plan to attend the next International Seaweed Symposium (ISS), in Copenhagen, Denmark, this coming June 2016? I encourage you to attend and send your abstract. We could also find some time to have an interesting discussion face to face during that week.

I am also the Secretary General of the International Seaweed Association (ISA), which is the association organizing the ISSs every 3 years.

Hi Thierry, Can you send us details of the conference? My colleagues may be of iterest also. my email add. is [email protected]

Hi all,

All the information about the next International Seaweed Symposium (ISS) can be found on the site of the International Seaweed Association (ISA) at http://www.isaseaweed.org/

Hi Sir,

https://thefishsite.com/articles/innovators-bring-anti-fouling-nets-to-chiles-aquaculture-industry