Background and Objectives: This study aimed to assess the recorded CPUE (Catch Per Unit Effort) and standardized CPUE of five fish species: Croaker (Otolithes ruber), Grounter(Pomadasys kaakan), Grouper (Epinephelus coioides), Black Pomfret(Parastromateus niger) and Sea Bream(Acanthopagrus latus) along the southern coasts of Iran. CPUE is used as an index of relative abundance in stock assessments. However, this index can be influenced by factors such as fishing gear, fishing structure, hanging ratio, mesh size, ecological conditions of the study area, and the target species’ abundance in active fishing. To mitigate these effects on catchability, standardized CPUE is utilized.
Methods: Data was gathered from field studies conducted by the Iranian Fisheries Organization from 2016 to 2020 along the southern coasts of Iran (Khuzestan, Bushehr, Hormozgan, and Sistan and Baluchestan). The fishing method used was gillnetting, one of the most substantial fishing methods in the Persian Gulf and the Oman Sea. Generalized Linear Models (GLMs) were used to standardize and predict CPUE values based on variables such as fishing region, year, and month. For analyzing CPUE across different provinces and years, Analysis of Variance (ANOVA) and Duncan’s multiple range test were employed for mean comparisons.
Findings:The greatest discrepancy between recorded CPUE (kg/roll/day) and standardized CPUE (kg/roll/day) for Otolithes ruber was found in Sistan and Baluchestan province with values of 12.7 and 21.1 (kg/roll/day) in 2020, respectively, while the smallest discrepancy was in Hormozgan province with values of 3.1 and 3.1 (kg/roll/day) in 2018. For Pomadasys kaakan, the largest discrepancy was in Khuzestan province with values of 8.6 and 3.7 (kg/roll/day)in 2016, and the smallest was in Hormozgan with values of 0.3 and 2.8 (kg/roll/day) in 2017, and in Khuzestan with values of 2.3 and 2.5 (kg/roll/day) in 2020. For Parastromateus niger, the greatest discrepancy was in Sistan and Baluchestan with values of 34.4 and 27.2 (kg/roll/day) in 2016, and the smallest in Khuzestan with values of 2.1 and 2.5 (kg/roll/day) in 2018. For Epinephelus coioides, the greatest discrepancy in Hormozgan was with values of 4.0 and 2.4 (kg/roll/day) in 2017, and the smallest in Hormozgan with values of 2.2 and 2.3 (kg/roll/day) in 2019. For Acanthopagrus latus, the greatest discrepancy in Khuzestan with values of 7.4 and 5.2 in 2020, and the smallest in Hormozgan with values of 1.3 and 1.3 (kg/roll/day) in 2018.
Conclusion: Fluctuations in CPUE can be influenced by factors such as the design of fishing gear, captain’s experience, technological advancements, environmental conditions, fish distribution and the factors affecting it, fishing pressure, efficiency of fishing fleets, and the manner of stock exploitation. Since CPUE serves as a hypothetical representative for the fish stock abundance index and holds significant importance in stock assessments and the examination of fishery stock statuses, and in light of the global decline in fishing trends both from the sea and inland waters, the investigation of these factors in fishery studies appears necessary and essential. |
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