Development of biodegradable materials to reduce the effect of ghost fishing in the Norwegian deep-sea gillnet fisheries

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2018

Budget

825,084 EUR

Fundings

Abstract

Gillnet is one of the most important fishing gears in Norway. Cod, saithe, Greenland halibut, angelfish, and lumpfish are the most important species for these fisheries. In 2012, the cod quota was distributed as follows: approx. 93,000 tonnes for the gear group fishing with gillnets, approx. 76,000 tonnes for trawl, approx. 58,000 tonnes for Danish seine, approx. 40,000 for autoline, and approx. 25,000 tonnes to others. However, it is estimated that the number of lost gillnets per year is approx. 13.900. Today, Norway and South Korea are the only countries in the world that have a program for systematic clean-up of lost fishing gear from the most intensively fishing areas. The Norwegian Directorate of Fisheries has since 1983 retrieved approx. 20,450 lost gillnets, and a considerable number of other fishing gear. The cleaning operation is very demanding due to the operation depth (500-1000m), strong currents areas, and the uncertainty associated with the accuracy of the positions of the lost nets. Therefore, in parallel with the clean-up program, research in recent years has focused on developing methods and techniques to reduce the number of lost nets, location of lost gears, and assess the possibility of using biodegradable materials. Biodegradable gillnets (that degrades in water and CO2) have been developed in recent years by S-ENPOL (earlier owned by Samsung Fine Chemicals Co. Ltd.) and are now a commercial product used in several gillnet fisheries in South Korea. This project has carried out the following tasks: i) Degradation tests in the sea. In these tests, we put samples of degradable and nylon monofilaments, as well as degradable and nylon nets in the sea, both in Trondheim and in Tromsø. The test was conducted for two years and the samples were analysed for tensile strength and elongation at break every three months. ii) Degradation experiments in lab focusing on studying changes in polymers in the material and quantifying any detached particles to the seawater. iii) Fishing trials. Biodegradable PBSAT gillnets have been tested in the fisheries for Greenland halibut (May-Jun. 2016), saithe (Oct.-Dec. 2016, 2017 and 2018) and cod (Jan.-Mar. 2017 and 2018). The experiments were conducted in commercial fishing grounds and under commercial fishing conditions. iv) UV degradation test. The project has developed degradable gillnets. Fishing experiments on cod, saithe and Greenland halibut show that bio gillnets still have poorer fishing efficiency than traditional nylon gillnets. Lower fishing efficiency can make fishermen prefer traditional nylon gillnets rather than bio gillnets because they have a higher fishing efficiency. Degradation tests in the sea show approx. 26% reduction in breaking strength in PBSAT nets after approx. 25 months in the sea (cold water), while the samples from bio-nets used in one fishing season (max. 3 months) showed approx. the same reduction in breaking strength. Daily use and wear of the gillnets accelerates the degradation process. Controlled laboratory tests at 20 °C also show approx. 20% degradation after 12 months exposure in seawater. No fragmentation has been recorded, i.e. microplastic formation. UV degradation tests where we exposed biodegradable material to UV-radiation showed that PBSAT monofilaments degrade faster than nylon monofilaments, thus demonstrating a stronger reduction in mechanical strength and material integrity. In addition, PBSAT is changing its chemical structure more significantly during degradation compared to nylon. UV degradation tests showed detached particles. This project has focused on developing biodegradable gillnets for Norwegian fishing and has focused on quantifying the catch efficiency, degradation rate and possible formation of microplastic in seawater. Much of the results from these studies have already been published in international journals. Some tests are still running and several publications on the subject are expected in the future. It is recommended further studies of catching modes and this requires new fishing experiments and new analyses of data. It is proposed to continue the project and complete the work where we study the degradation process of the biomaterial. Today this experiment has lasted for 18 months but was designed and planned to last 36 months. A large problem of using gillnet in commercial fishing is that the fishermen lose considerable amounts of gillnets. The Norwegian Environment Agency (2018) has estimated that approx. 13000 gillnets are lost per year. Lost gillnets give the fishermen an alternative loss in the form of lost catches by ghost fishing. It is therefore strongly recommended to carry out a bio-economic analysis of gillnet fishing and estimate the value of lost resources due to ghost fishing mortality. It is recommended to investigate how the use of bio gillnets (and thus the reduction of plastic pollution and ghost fishing) can be implemented in Norway.