Wednesday, June 28, 2017

28/06/2017: Biofouling-free, low maintenance and mortality-rate-reducing – why we need recyclable brass nets in offshore aquaculture

by Martin Heidenreich, Wieland-Werke AG, Germany

Whereas the demand for fish is increasing worldwide from year to year, fish stocks are overfished

For this reason, marine aquaculture today is becoming more important and is facing tremendous challenges. This implies, in particular, that the requirements for cage systems are growing significantly. The main reasons include environmental compatibility, low contaminant levels in fish and better growth, recyclability of materials, service life of systems, algal growth/biofouling, control of parasites (sea lice) as well as increasing cost pressure in the fish production.
Wieland Bluesea net installed for customer InnovaSea in Panama
Image credit: ©InnovaSea Systems Inc

So, how can such complex problems be tackled?
The use of brass nets in marine aquaculture is an innovative and “green” solution to many problems. The brass nets provide considerable improvement over traditional cages. Bluesea is a brass wire produced by Wieland that has been especially developed for the needs of maritime fish farming.

In addition to its excellent corrosion resistance also in seawater environments, the copper content of this alloy is sufficient to inhibit biofouling in a natural way. Especially for large cages, high mechanical strength and good abrasion resistance are of decisive advantage. Lower susceptibility to biofouling due to the copper content improves the water exchange and the oxygen level inside the cages.

As a result, growth of parasites (sea lice) and other pathogens is inhibited and the infection risk in fish is significantly reduced. Thus it is not necessary to use antibiotics and antifouling coatings. The nets are practically free from biofouling and therefore the cleaning and inspection intervals of the nets are much longer than those of synthetic netting materials.

This will dramatically reduce maintenance costs. Due to the high stability of the copper alloy nets, the cages retain their form even with strong currents and high waves. In addition, brass is completely recyclable and thus it is a sustainable material in aquaculture.

Naturally clean: Release of copper ions prevents biofouling
Biofouling presents an enormous challenge for fish farmers. Conventional methods to prevent biofouling are expensive and harmful to the environment. The antimicrobial properties of the Bluesea nets have a positive effect on the growth: no biofouling, no time-consuming cleaning of the nets and, therefore, significantly lower maintenance costs.

Since fish farming is sited more and more away from the coast under open sea conditions, preventing biofouling is an essential factor for the stability of the nets, for avoiding fish escapes and also for the safety of the workers. The resistance of copper is achieved by the gradual release of copper ions so Bluesea does not release increased copper concentrations into the environment.

The Wieland Bluesea net is naturally free from biofouling, which reduces sea lice levels and prevents sea lice larvae from settling on cages. Settlement of mussels and small crustaceans is also limited because they cannot find food (algae). Bluesea nets meet the essential requirements of “Green Licenses” for aquaculture and provide, therefore, a sustainable solution for the development of aquaculture.

Fish health
Improving the habitat of fishes will have positive effects on their growth. This contributes to increasing the profits of fish farmers, since infections of fish caused by biofouling organisms can be avoided. In Australia fish farmers can abstain from antibiotics or chemical treatments in salmon farming by using Bluesea nets. Numerous tests show a decrease in the mortality rate of fish when using brass nets.

Read the full article, HERE.

The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
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