Comparative Analysis of Catch Efficiency and Discard Ratio in Monofilament versus Multifilament Bottom Trammel Nets: A Case Study from Çanakkale, Türkiye

This study aimed to evaluate the catch efficiency and chondrichthyan bycatch of monofilament and multifilament bottom trammel nets which are extensively used in small-scale commercial fishing in the Çanakkale region. The field trials of the study were carried out between September 2024 and March 2026. Within the scope of the study, a total of 8 units (800 m) of trammel nets were used. The inner panels of the trammel nets were rigged with a 84 mm stretch mesh size, and all other technical characteristics of the monofilament and multifilament net were identical. A total of 65 fishing trials were carried out with these nets. The nets were deployed for 36 hours during each trial. As a result of the fishing experiments, a total of 981 individuals weighing 622.3 kg, representing 20 species, were captured. Species with commercial value were classified as target species, while those without commercial value were classified as discard. When the economic species caught in the nets were compared on a numerical basis, multifilament trammel nets caught 1.22 times more individuals than monofilament trammel nets. In contrast, for discarded catch, monofilament trammel nets caught 1.62 times more individuals than those caught by multifilament trammel nets, and these differences were statistically significant (P < 0.05). In addition, the ratio of priority conservation species within the total catch in terms of the number of individuals was calculated as 23.2% in monofilament trammel nets and 12.5% in multifilament trammel nets. In the comparison made using repeated measures analysis of variance, the difference between the nets was found to be statistically significant. The study determined that the preference for monofilament material is considered unnecessary for the nets used in the fishing of species such as cuttlefish, lobster, and scorpionfish in the region, as multifilament trammel nets are more efficient than monofilament trammel nets in catching target species. Additionally, considering that a large part of the discard consists of conservation-priority chondrichthyan fish species, it was determined that the use of monofilament material in trammel nets is not suitable in terms of sustainable fisheries. It was established that the preference for multifilament trammel nets would enhance bycatch mitigation.