Trawl Fishery Bycatch in Marine Protected Areas of the Northern Persian Gulf: A Case Study of Dayyer-Nakhiloo and Mond

Abstract

Abstract This study investigates the composition of bycatch and the maturity status of some commercial fish caught by fishing boats equipped with shrimp trawls in the Dayyer-Nakhiloo and Mond marine protected areas in Bushehr, located in the north of the Persian Gulf. Cruises were conducted by fishing boats equipped with 27-foot length and 115-horsepower engines between August 18th and September 20th in 2020 and 2021. The trawl nets were made of polyamide (PA) and had mesh sizes of 50 mm in the body and 40 mm in the bag (STR). After 32 haulings, a total of 37 aquatic species were caught as bycatch. Greater lizardfish (Saurida tumbil), largescale tonguesole (Cynoglossus arel), blue swimming crab (Portunus segnis), whipfin silver-biddy (Gerres filamentosus), spotted sicklefish (Drepane punctata), elongate sole (Solea elongata), and orange-spotted grouper (Epinephelus coioides) were the most frequently caught species in all seasons. The results of the bycatch weight showed that the highest and lowest amounts of bycatch weight were observed in the 18th and 3rd fishing operations in the Mond region, respectively, with 234 kg and 4 kg. Similarly, the highest and lowest amounts of catch per unit effort (CPUE) were observed in the 18th and 9th fishing operations in the Mond region, respectively, with 234 kg h-1 and 3.25 kg h-1. The bycatch to shrimp ratio (r) was computed as 2.32:1. The results of species dominance showed that Acanthopagrus arabicus (9.4%), Scomberomorus commerson (7.75%), and Saurida tumbil (6.05%) had the highest percentage of abundance during the study period. Length frequency data of commercial fish caught showed that Parastromateus niger (44.19%) and Acanthopagrus arabicus (33.81%) had the highest percentage of mature fish in the specimens, while Scomberomorus commerson and Epinephelus coioides had the highest percentage of immature fish (100%). Overall, the present study indicates that bottom trawling by fishing boats in Dayyer-Nakhiloo and Mond marine protected areas poses a threat to the biodiversity of the Persian Gulf. An efficient management approach is therefore essential to promote responsible fisheries in the region.