Investigation of the relative abundance of cephalopods in the neritic zone of Northeast Gulf of Oman using field data

Document Type : Research Paper

Authors

1 Fishing and Exploitation Department, Faculty of Fisheries and Environment, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

2 Capture and Fishery Office, Iranian Fisheries Organization, Tehran, Iran.

Abstract

Previous studies of the relative abundance of cephalopods in the Gulf of Oman are limited, and they focused on the commercial species Sepia pharaonis. Therefore, the relative abundance of some cephalopods in the Northeast Gulf of Oman (neritic zone) was studied based on the Catch Per Unit of Effort index. Commercial fisheries data were collected using field sampling by a stern trawler with a bottom trawl gear (cod-end mesh size: 85 mm) from the Ferdows fishing fleet. The possible effects of five variables depth, distance from the shoreline, fishing time of day, the velocity of the vessel, and type of haul on Catch Per Unit of Effort were measured with Generalized Linear Models, Zero-Inflated Models, and Redundancy Analysis (both regression and ordination analyses). Sepia pharaonis and Uroteuthis (Photololigo) duvaucelii had the highest relative abundance based on weight and number, respectively. Weight-based relative abundance of Sepia pharaonis was 5251.126 gr/hour (S.E. ± 1156.672), while the number-based relative abundance of Uroteuthis (Photololigo) duvaucelii was 56.201 individual/hour (S.E. ± 8.560). Overall, Sepia pharaonis, Uroteuthis (Photololigo) duvaucelii, and Sepia stellifera had the highest relative abundance values based on weight. Also, Uroteuthis (Photololigo) duvaucelii, Sepia stellifera, and Sepia omani had the highest relative abundance values based on the number. According to the uneven topography of the study area, both in regression and ordination analyses, the depth variable had the greatest effect on the relative abundance of cephalopods. The effect of depth was more noticeable in ordination analyses (often p < 0.001).

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Environmental Resources Research
Volume 12, Issue 1
July 2024
Pages 1-18

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