Catch per unit effort and bycatch composition of shrimp trawler boats in Bushehr province (Mond and Dayyer-Nakhiloo)

Abstract

Introduction: This study aimed to investigate the catch per unit effort of target and non-target
species and to determine the bycatch composition in boat trawlers used in Mond and Dayyer-
Nakhiloo coastal waters in Bushehr province.
Materials & Methods: Field operations were carried out during the years 2020 (13 August to
15 February) and 2021 (11 April to 9 September). During the research, a 27-foot fishing boat
with a 200 hp engine was used. The trawl net used was made of polyamide (PA). The sampling
operation was performed in 32 steps. During this study, the amount of catch per unit effort, the
ratio of by-catch to the target species, and the amount of by-catch were calculated.
Results: The highest frequency of Penaeus semisulcatus in July 2021 (96.67%), the highest
frequency of Metapenaeus affinis in August 2021 (21.74%), and the highest frequency of
Parapenaeopsis stylifera in July 2021 (63.75%) were recorded in Mond. 37 aquatic species
were observed as a bycatch composition during fishing operations. Species including Saurida
tumbil, Cynoglossus arel, Portunus segnis, Gerres filamentosus, Drepane punctata, Solea
elongata, and Epinephelus coioides were permanently present in the catch composition. The
highest rate of shrimp fishing effort was observed in the Mond region (58 kg/h) and the lowest
rate was observed in the Dayyer-Nakhiloo (1 kg/h). Also, the ratio of by-catch to target (r) was
2.32 and the weight of by-catch during the fishing season was 1478.96 kg.
Discussion: The results indicate high fishing pressure on commercial and non-commercial
species in this area and can be used to assess the damage caused by shrimp trawl nets on fish
stocks in ecological risk assessment models. In addition, the findings showed that the deletion
of some species can make the food chain longer due to their role in the food chain and reduce
the resistance of the ecosystem food web, and ecological and habitat efficiency.