Final Report Summary - ESCAPEPROOFNET (Escapees in European Aquaculture Development of an Escape proof Net Especially for Cod Bass and Bream Fish Farming) Technology which was initially developed for salmon farming purposes is currently used for intensive farming of species such as seabass, seabream and cod. However, these fish are more aggressive towards catching nets, causing damages and holes that result in escapees and loss of fish stock. Apart from decrease in competitiveness for small and medium enterprises (SMEs) operating in aquaculture sector, escapees represent a threat to ecology and biodiversity due to potential disease transfer and genetic impacts to wild fish population. In order to overcome this threat, the ESCAPEPROOFNET project aimed to develop a sea cage net system suitable for farming of typical net aggressive fish species which were exploited by the European fish farming industry. As a result, a cost-effective polyolefin net filament was designed with adequate physical characteristics, anti-bite and antifouling properties. In addition, existing net manufacturing techniques were modified for optimal exploitation of materials and employed to produce a net with improved configuration, strength and durability and low operational costs. Extensive examination of target species behaviour and weaving technology was necessary towards achieving the project objectives. Moreover, a methodology for successful implementation of the innovations was developed, in order to optimise a single net system which reduced escapees to less than 0.50 % compared to conventional cages. The project experienced delays due to the need to incorporate remarks on the utilised materials and applied methods, as well as due to imponderables which delayed production. The required improvements were related to the development of biocide-free solutions, as well as to the material surface properties so as to minimise fouling on the new filaments for cage nets. The changes addressed sufficiently the environmental and regulatory issues that arose through the project elaboration; however they rendered impossible the construction and evaluation of a full-scale prototype within the available time frame. Validation was thus performed using framed net samples. Nevertheless, ESCAPEPROOFNET was successfully completed and all the initial objectives were achieved. Firstly, a study on fish species behaviour and biofouling was made based on literature and experience in order to define specific net requirements. The diversity and intensity of biofouling was site specific, depending on season, geographic location and local environmental conditions. It greatly reduced the efficiency of materials and equipment, while commercialisation of biofouled produce, such as shellfish, was greatly affected due to aesthetic and toxic impacts. The associated costs were potentially significant. Thus, conventional and innovative antifouling strategies were examined, like mechanical cleaning, biocidal or silicon coatings, alternative cage designs and biological control using grazers. Moreover, the project evaluated alternative materials for net construction, using nylon as a reference. The examined options included high density polyethylene (HDPE) along with polyethylene teraphthalate (PET) and HDPE blends. It occurred that the blends combined the stiffness of PET with the good impact strength of HDPE; however, good quality fibre could not be produced using recycled PET. In addition, impregnating and repulsive agents were assessed for possible integration into the filament yarn. Integration of chemicals was avoided and natural antifoulants were evaluated instead. Potential developments in net design were also investigated so as to increase strength and reduce biting. The dynamic loads on the nets were expressed in relation to wave height. In addition, the ocean currents varied with depth and were described as a function of the climatic conditions of each location. The precise description of local conditions remained though site specific. The minimum requirements for cage design, dimensioning and materials were in accordance to the Norwegian legislative standards. Aquaculture cages were categorised as rigid, semi-rigid and flexible structures, with the latter dominating the sector. Knotted flexible net cages reduced filament strength and were potentially harmful to fish due to increased chance of removing their protective slime. Knotless nets were developed by the market, mostly through warp knitting and twisting in square, diamond or hexagonal forms. Twisted net was favourable compared to knotted meshes, while it also had reduced weight and improved hydrodynamic properties compared to other knotless cage nets. Even though a cage net prototype was not developed as part of ESCAPEPROOFNET a handmade knotted HDPE and PET net, without integrated antifouling additives, was produced. The sample was subsequently mounted on frames, applied on existing cages and evaluated for biting and fouling resistance. The analyses were performed both in the sea and in a laboratory scale. A patent search was carried out and possibly competitive patents were continuously observed. Knowledge was transferred to SMEs through their involvement in the project and the defined best practice for net maintenance was estimated as particularly useful to end users. In addition, participation in exhibitions and press releases allowed for broad knowledge dissemination. Potential market areas were also defined and relevant feasibility studies were performed. Finally, a project website was developed and updated, facilitating information transfer. Powiązane dokumenty Final Report - ESCAPEPROOFNET (Escapees in European Aquaculture Development of an Escape proof Net Especially for Cod Bass and Bream Fish Farming)
