Effect of Using Biodegradable Gill Nets on the Catch Efficiency of Greenland Halibut

Abstract

The effect of using biodegradable polybutylene succinate co‐adipate‐co‐terephthalate (PBSAT) gill nets on the relative catch efficiency was assessed in a commercial gill‐net fishery targeting Greenland Halibut Reinhardtius hippoglossoides in northern Norway. Compared with conventional polyamide gill nets, the PBSAT gill nets caught fewer fish, and the relative catch efficiency decreased with increasing fish size. For fish larger than 65 cm, the reduction in catch efficiency was significant, as the PBSAT gill nets caught 30% fewer Greenland Halibut in this size range than the conventional polyamide gill nets. Differences in mesh size, breaking strength, and elasticity could contribute to the difference in size‐dependent catch efficiency between the two types of gill nets.

Effect of mechanical properties of monofilament twines on the catch efficiency of biodegradable gillnets

“…Force-elongation curves of new and used nylon PA and biodegradable gillnets from experiments carried out in 2016-2019 [18][19][20] are presented and used in the discussion section to support the findings of this study. These curves were estimated by following the same tensile testing procedure as described above.…”

“…The monofilament thickness was 0.55 and 0.60 mm in the biodegradable gillnets and 0.55 mm in the nylon PA gillnets. Since biodegradable monofilaments are 11-16% weaker than nylon PA monofilaments of the same diameter [18][19][20]26], we increased the diameter of the biodegradable monofilament from 0.55 to 0.60 mm to compensate for the difference in tensile strength. Assumimg a linear relationship between monofilament thickness and breaking strength an increase from 0.55 to 0.60 mm would be equivalent to a 9% increase in strength.…”

“…The results showed that in some cases the fishing efficiency of these gears is similar to that of gears made of PA, polyethylene, and polypropylene. In Norway, biodegradable PBSAT gillnets have shown a consistently lower catch efficiency than nylon PA gillnets, and this difference has been mainly attributed to the fact that biodegradable gillnets are made with 11-16% weaker monofilaments than nylon PA monofilaments of the same diameter [18][19][20]26]. The aim of the present study is to assess the effect of twine thickness and tensile strength on the catch efficiency of biodegradable PBSAT gillnets.…”

“…Biodegradable plastic is a plastic that maintains similar properties as a conventional plastic during use, but that can be completely degraded by naturally occurring microorganisms such as bacteria, fungi, and algae when disposed of in the environment [11]. The most investigated biodegradable plastics in fishing equipment and other marine applications, i.e., aquaculture, are polybutylene succinate, polybutylene adipate co-terephthalate, and polybutylene succinate co-adipate-co-terephthalate [12][13][14][15][16][17][18][19][20]. Commercial fishing products made of these materials are available in some countries, such as South Korea.…”

Assessment of the physical characteristics and fishing performance of gillnets using biodegradable resin (PBS/PBAT and PBSAT) to reduce ghost fishing

“…In Norway, however, in a test on halibut ( Hippoglossus sp.) and cod ( Gadus morhua ) gillnets fabricated from thick PBSAT monofilaments, the fishing performance of the biodegradable nets showed only slight differences from those of conventional nylon nets (Grimaldo et al, 2018; Grimaldo, Herrmann, Tveit, Vollstad, & Schei, 2018). In addition, although biodegradable gillnets may show differences depending on the target species, there are also reports that they are much more efficient in terms of resource management, because for some species, such as yellow croakers and snow crabs ( Chionoecetes opilio ), the catch of immature individuals is much lower than that for commercial gillnets (Kim et al, 2014; Park, Bae, et al, 2007).…”