English abstract
Background. Shrimps are one of the most valuable marine resources of Oman and shrimp fisheries is greatly contributing to the national economy, and sustainability of traditional fisheries villages. However, the shrimp trawl fishery has one of the highest bycatch rate of any fishery and cause negative impacts to marine populations and benthic habitats. This study provides the first data on the c omposition and abundance of the bycatch in the main shrimp fishing grounds distributed along the south-eastern coastline of Oman in the Arabian Sea. Materials and methods. Shrimp trawl survey was conducted monthly from January to December 2013 in seven sites using demersal otter trawl. Overall, 93 trawl catches were used for the analysis of the bycatch composition based on weight, number, and frequency of occurrence. Top ten species and top fish families, cephalopods, and crabs were defined in the bycatch. The bycatch compositions were compared in different regions using biodiversity indices and the cluster analysis. Results. Mean monthly bycatch during the shrimp trawling survey in the coastal waters of Oman in 2013 ranged from 22.2 to 191.5 kg · h–1, in different months with an overall mean (±SE) of 58.7 ± 5.2 kg · h–1 (n = 93). The bycatch to catch ratio was estimated 8.9 : 1 for shrimp fisheries. This ratio fl uctuated significantly over the year with minimum values from April to September. The bycatch composition included 97 bony fish species from 36 families, 12 species from 7 elasmobranchs families and several species of cephalopods and crabs. Catfishes (Ariidae), frogfish (Antennariidae), ponyfishes (Leiognathidae), and rays (Dasyatidae and Gymnuridae), represented a majority of the bycatch. Conclusion. Shrimp fishery in Oman is affecting mainly small-sized and slow-moving fishes, and invertebrates with low economic value. However, the fine-meshed shrimp trawls also capture juveniles of commercial important fishes and cause some ecological problems. The results from the study point out the necessity of management actions to develop a special policy on bycatch reduction in Oman fisheries.
