The longline gear consists of a number of branch lines (“gangions”) with baited hooks connected to a strong main-line made from 3-11 mm thick polyester (PES) rope. Number of hooks in a typical Norwegian longline fishery range from a few hundred in small scale operations to 70.000 in mechanized, deep-sea fisheries. With a distance of 1.3-1.4 m between branch lines/hooks, the total length of the gear is 10 km (inshore operations) - 90 km (deep sea operations).
The loss of plastic-based materials contributes to the pollution of our food source! This is an image that does not align with the characterization of "longline fishing as environmentally friendly," and out of respect for a proud industry, measures are therefore desired to make longline fishing even more sustainable.
Fishing with longlines has a long tradition in Norwegian fisheries and this type of fishery is known for landing exceptionally high-quality fish utilized for well-paid products. Longline fishing is characterized as an activity with a relatively low carbon footprint and is considered one of the most environmentally friendly fishing methods used, and it contributes to important activity in small and large ports along our coast. Unlike gear such as gillnets and pots, loss of longlines will not lead to ghost fishing (i.e., continuous capture from lost fishing gears).
However, this fishing method poses challenges by contributing to marine litter. Modern longline fishing has a large consumption of components made of synthetic, petro-based materials like PES and nylon (PA). Both materials sink in seawater. During operation the branch lines (and hooks) are exposed to tensions, abrasion and damage and must be replaced relatively often. In Norwegian longline fisheries the annual consumption of branch lines is estimated to be several hundred kilometres. In mechanized longline operations (autolining), sections of ca. 1.5 km lengths of main lines are connected with single-use twines made from PES or PA.
During hauling of the gear, branch lines may break and in the mechanized fishery the connections between line sections are cut before these sections are stored on a rail system. Branch lines lost during hauling will stay at the seabed. Single-use twine cut-offs and changed branch lines during mending on board may also accidentally end up at the seabed. The loss of plastic-based materials contributes to the pollution of our food source! This is an image that does not align with the characterization of "longline fishing as environmentally friendly," and out of respect for a proud industry, measures are therefore desired to make longline fishing even more sustainable.
In a new research project funded by the Norwegian Seafood Research Fund (FHF), led by UiT the Arctic University of Norway, together with SINTEF Ocean, SINTEF Industry and industry partners in Dsolve, we aim to develop environmentally friendly materials for use in longline fishing. The modified longlines will be operated from one deep sea mechanized vessel (51 m), one inshore (coastal) mechanized vessel (11 m) and one inshore vessel (13 m) with traditional hand-baited hooks. The trials will be carried out during 2025 and 2026 and the results from the various tests will be disseminated in news articles, reports, fisheries fairs, etc. In addition, a substantial part of the data will be published in peer reviewed articles and included in the doctoral education of PhD candidate Anja Alvestad and hopefully several master's degree students.
