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International Journal of Aquaculture 2026, Vol.16, No.2 http://www.aquapublisher.com/index.php/ija © 2026 AquaPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Publisher Aqua Publisher Edited by Editorial Team of International Journal of Aquaculture Email: edit@ija.aquapublisher.com Website: http://www.aquapublisher.com/index.php/ija Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada International Journal of Aquaculture (ISSN 1927-5773) is an open access, peer reviewed journal published online by AquaPublisher. The journal publishes all the latest and outstanding research articles, letters and reviews in all working and studying within varied areas of aquaculture, containing the latest developments and techniques for practice in aquaculture; information about the entire area of applied aquaculture, including breeding and genetics, physiology, aquaculture-environment, hatchery design and management, utilization of primary and secondary resources in aquaculture, production and harvest, the biology and culture of aquaculturally important and emerging species. All the articles published in International Journal of Aquaculture are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. AquaPublisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors' copyrights. Aqua Publisher is an international Open Access publisher specializing in the field of marine science and aquaculture registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada.
International Journal of Aquaculture (online), 2026, Vol. 16, No. 2 ISSN 1927-6648 http://aquapublisher.com/index.php/ija © 2026 AquaPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Latest Content Finite Element Strength Assessment of a Crane Foundation Deck in a Multi-Cat Fish Farm Support Vessel Farzad Tahmasebi International Journal of Aquaculture, 2026, Vol. 16, No. 2, 61-73 Phytochemical Characterization and Anaesthetic Efficacy of Citrus Leaf Extracts for Sedation and Handling of Nile tilapia (Oreochromis niloticus) and African Catfish (Clarias gariepinus) Akpomughe E., Awhefeada O.K., Mukoro J.E., Okpu P.N. International Journal of Aquaculture, 2026, Vol. 16, No. 2, 74-89 Evaluate the Future Scenarios of Water Demand in the Middle Nzoia River Catchment Dennis Gikonyo Mwangi, Basil Iro Tito Ongor, Edwin Kimutai Kanda International Journal of Aquaculture, 2026, Vol. 16, No. 2, 90-110 Hydrological Stress, Biodiversity Loss and Livelihood Collapse — Climate Change Challenges in Coastal Fisheries of Ondo State, Nigeria Ojo O.B., Olawusi-Peters O.O., Ajibare A.O. International Journal of Aquaculture, 2026, Vol. 16, No. 2, 111-124 Research Progress on Key Technologies for Disease Prevention and Control in Shrimp Aquaculture Jinfeng Pan International Journal of Aquaculture, 2026, Vol. 16, No. 2, 125-140
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 61 Review Article Open Access Finite Element Strength Assessment of a Crane Foundation Deck in a Multi-Cat Fish Farm Support Vessel Farzad Tahmasebi MSc of mechanical engineering, Port and Maritime Organization (PMO), Tehran, Iran Corresponding email: Farzadtahmasebi52@gmail.com International Journal of Aquaculture, 2026, Vol.16, No.2 doi: 10.5376/ija.2026.16.0006 Received: 20 Jan., 2026 Accepted: 27 Feb., 2026 Published: 15 Mar., 2026 Copyright © 2026 Tahmasebi, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Tahmasebi F., 2026, Finite element strength assessment of a crane foundation deck in a multi-cat fish farm support vessel, International Journal of Aquaculture, 16(2): 61-73 (doi: 10.5376/ija.2026.16.0006) Abstract This study evaluates the structural strength of the forecastle deck in the crane foundation area of a Multi-Cat vessel using the finite element method. A three-dimensional finite element model was established to simulate the deck structure under crane operating loads. The analysis considered the most critical lifting condition and included eight crane rotation angles. Stress results were assessed according to the allowable stress requirements of the ABS Rules for Building and Classing Steel Vessels under 90 Meters. The results show that the maximum Von Mises stress occurs at a rotation angle of 180°, with a value of 160.4 MPa, which is lower than the allowable limit of 165 MPa. Therefore, the deck structure in the crane foundation region satisfies the strength requirement under the examined operating conditions. The study confirms that finite element analysis is an effective tool for verifying the structural safety of crane-supported deck structures. Keywords FEM; Crane; Forecastle; Deck; ABAQUS; Foundation 1 Introduction The structural integrity of ship decks subjected to concentrated loads is a key issue in marine structural design, especially in regions supporting crane foundations. During lifting operations, crane loads generate significant local stresses and deformation in the deck plating, stiffeners, girders, and supporting substructure. If these effects are not properly evaluated at the design stage, they may lead to excessive deformation, local yielding, fatigue damage, or even structural failure in service. Therefore, local strength assessment of deck structures under crane loading is an essential part of structural verification for crane-mounted marine vessels. Recent studies have shown that finite element analysis has become an effective approach for evaluating local reinforcement schemes and structural responses in crane-supported marine structures. For example, Dragatogiannis et al. (2024) analyzed deck reinforcement arrangements for crane installation on a composite yacht and showed that local strengthening has a significant influence on stress distribution and structural safety. Hernández-Ménez et al. (2023) proposed a structural assessment methodology for an FPSO main deck supporting an offshore crane and demonstrated that different crane operating conditions may substantially affect deck behavior. In addition, Abdullah et al. (2023) carried out a finite element strength analysis of a deck crane barge and confirmed that numerical simulation is a practical tool for identifying critical stress locations in crane-bearing deck structures. These studies indicate that finite element-based assessment has become an important method for evaluating the structural adequacy of crane foundation regions in marine applications. With the development of computational mechanics, the finite element method (FEM) has been widely adopted to simulate complex structural responses under localized marine loading conditions with high accuracy. Compared with simplified analytical approaches, FEM can represent the interaction between deck plating, stiffeners, girders, supporting bulkheads, and pillars more realistically, making it particularly suitable for crane foundation regions where load transfer is highly localized and structurally discontinuous. In practical ship design, classification society rules provide the basis for determining whether the calculated stresses are acceptable. Consequently, combining finite element analysis with rule-based acceptance criteria offers a rational and reliable framework for assessing deck strength in crane installation areas.
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 62 This study investigates the structural behavior of the forecastle deck in the crane installation area of a Multi-Cat vessel by means of finite element analysis in accordance with ABS requirements. The analysis focuses on the stress distribution and structural response of the deck and its supporting members under crane loading, with particular attention to the influence of crane slewing position on the critical stress state. The results are intended to support structural verification of the crane foundation region and to provide a practical reference for deck reinforcement design in similar working vessels. The contribution of this work can be summarized as follows. First, a three-dimensional finite element model is established for the forecastle deck together with its surrounding supporting structure, so that the local load transfer mechanism in the crane foundation region can be evaluated in detail. Second, the crane loading is examined under a series of slewing angles, which makes it possible to identify the most unfavorable operating position rather than relying on a single loading direction. Third, the calculated stresses are assessed against an ABS-based allowable stress criterion, allowing the numerical results to be directly linked to practical structural acceptance in ship design. 2 Research Methods 2.1 Vessel particulars The vessel analyzed in this study is a Multi-Cat boat classified by ACS and operating under the Iranian flag, with an overall length of 19 m, a moulded breadth of 7.20 m, a moulded depth of 2.20 m, a displacement of 160 tonnes, and a midship draft of 1.70 m (Table 1). Table 1 Principal particulars of the multi-cat vessel ShipsName MULTI CAT BOAT Classification ACS Flag Iran GROSS/NET Tonnage --- Length overall 19m Length Between Perpendiculars 18m Breadth (moulded) 7.20m Depth @ MID (moulded) 2.20m DISPLACEMENT 160 tonnes Draft (mid) 1.70m Class Notation SPECIAL SERVICE, FISH FARM SUPPORT CRAFT Navigation area INTERNAL & TERRITORIAL WATERS 2.2 Abaqus software The software used in this study is SIMULIA Abaqus FEA, which provides comprehensive capabilities for modeling, analysis, and simulation based on the Finite Element Method (FEM). 2.3 System of units A consistent unit system was adopted throughout the numerical analysis, including millimeters for length, tons for mass, ton/mm³ for density, newtons for force, and MPa (N/mm²) for stress and pressure (Table 2). Table 2 System of units used in the analysis Unit Parameter mm Length Ton Mass ton/mm3 N MPa (N/mm2) Density Force Tension (Pressure)
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 63 2.4 Analysis type The deck structure has been analyzed using the linear static analysis method. The fundamental assumptions for employing linear static analysis are as follows: The material behavior is linear, and stress is directly proportional to strain according to Hooke's law. The applied loads on the structure are static and constant. The relationship between applied loads and structural displacements is linear (Figure 1). Figure 1 Assumptions of linear static analysis 2.5 Coordinate system A right-handed Cartesian coordinate system was adopted for structural modeling and analysis. The longitudinal direction was defined as the X-axis and taken as positive toward the bow, the transverse direction was defined as the Y-axis and taken as positive toward port, and the vertical direction was defined as the Z-axis and taken as positive upward toward the deck (Table 3). The origin of the coordinate system was located at the intersection of the ship centerline (CL) and the baseline (BL) (Figure 2). Table 3 Coordinate system (KR for Steel Ships, Part 3, Annex 3-2, Page 139) Axis Direction Positive orientation X Longitudinal Forward (toward the bow) Y Transverse Port (toward the left) Z Vertical Deck (upwards) Figure 2 Assumptions of linear static analysis 2.6 Geometric properties of the model The structural model extends from aft bulkhead 12 to the forecastle region, covering three compartments. The modeled deck region has dimensions of 6 000 mm in the longitudinal direction, 7 200 mm in the transverse direction over the full ship breadth, and 1 100 mm in the vertical direction below the deck (Figure 3).
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 64 The hull lines and all structural members in the modeled region were represented using shell elements based on the midship section drawing. The arrangement of frames, bulkheads, and other structural components was defined according to the structural drawings, including the sectional configurations from Frame 13 to Frame 18 and the bulkhead layout in the analyzed region (Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10). Figure 3 The model represents a length of three compartments in the Abaqus software Figure 4 Frame 13 structure Figure 5 Frame 14 structure Figure 6 Frame 15 structure
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 65 Figure 7 Frame 16 structure Figure 8 Frame 17 structure Figure 9 Frame 18 structure Figure 10 Layout of bulkheads in the modeled region
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 66 The dimensions of all structural elements have been modeled as shell elements in Abaqus, as specified in Table 4. The thickness of each element has been defined in the Property Section Manager module. Table 4 Geometric properties of structural elements in the model DECK CEN. GIRDER L200×100×10 mm DECK SIDE GIRDERS L200×200×10 mm DECKTR L200×100×10 mm DECKPLATE 10mm DECKBEAMs FB 100×12 mm SIDEPLATE 10mm SIDETR L200×100×10 mm PILLAR PIPE400×16 & PIPE150×8 mm To simplify the finite element model, small local features such as cutouts, lugs, scallops, air holes, and snipes were not included in the analysis (Figure 11). Figure 11 Deck plan showing the layout of longitudinal and transverse reinforcements and columns in Abaqus 2.7 Geometric Properties of the Model The finite element mesh was generated using free meshing with the medial axis algorithm. The mesh consists of both quadrilateral and triangular shell elements, with a global element size of 40 mm. The final model contains 71 996 nodes and 72 259 elements, including 71 822 quadrilateral elements of type S4R and 437 triangular elements of type S3 (Table 5). Table 5 Mesh properties of the finite element model Parameter Specification Element Shape Triangular and Quadrilateral Meshing Algorithm Medial Axis Meshing Technique Free Global Element Size (mm) 40 Number of Nodes 71,996 Number of Elements 72,259 Number of Quadrilateral Elements (S4R) 71,822 Number of Triangular Elements (S3) 437
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 67 2.8 Material mechanical properties Marine steel Grade A was selected as the material for the deck structure. The mechanical and physical properties used in the analysis include a Poisson’s ratio of 0.28, a Young’s modulus of 2.10 × 10⁵ N/mm², a density of 7.8 × 10-⁹ ton/mm³, and a gravitational acceleration of 9.81 × 10³ mm/s² (Table 6). Table 6 Mechanical properties of marine steel grade A Parameter Value Unit Poisson’s Ratio (ν) 0.28 - Young’s Modulus (E) 2.10×10⁵ N/mm² Density (ρ) 7.8×10⁻⁹ ton/mm³ Gravity (g) 9.81×10³ mm/s² 2.9 Boundary conditions A simply supported boundary condition was applied to the modeled deck structure. The displacements at both ends and along the side boundaries of the modeled region were restrained in the X-, Y-, and Z-directions, while rotational degrees of freedom were left unconstrained (Figure 12). In addition, displacement in the Z-direction was constrained along the outer boundary lines at the free ends of the columns and walls in order to represent the structural support conditions more realistically (Figure 13, Figure 14). Figure 12 Representation of the simple support boundary condition in the cross-section view Figure 13 Illustration of Z-direction displacement constraint in 3D view
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 68 3 Results and Discussions 3.1 Loading conditions The deck structure was evaluated under a series of crane loading cases corresponding to different slewing positions. The critical lifting condition considered in this study was defined by a boom length of 2 100 mm and a crane load of 6 300 kg. After applying a safety factor of 1.3, the effective lifting load increased from 61 803 N to 80 344 N. In addition, the boom self-weight of 12 753 N was applied at the boom center of gravity for each slewing position, and a uniformly distributed load of 0.3355 N/mm² representing the crane self-weight was also applied to the deck surface. The crane loading was examined from 0° to 315° at intervals of 45°, with clockwise rotation taken as the positive direction (Figure 14, Figure 15). The loading analysis was conducted under calm sea conditions in order to isolate the local structural response of the crane foundation region from wave-induced global effects. Figure 14 Crane loading cases Figure 15 Application of crane self-weight as a static load 3.2 Control criteria The structural assessment was carried out using the allowable stress criterion specified in the ABS Rules for Building and Classing Steel Vessels under 90 Meters. For conventional steel, the allowable stress is defined as: σallow=0.78 Sm Fy Where Sm=1 for conventional steel and Fy is the stress modification factor, which equals 1 for conventional steel, is the yield strength of the material. Because hull girder strength effects were not included in the present local model, the allowable stress was further reduced by 10% in accordance with the ABS requirement. As a result, the limiting stress adopted for the deck structure was 165 MPa (Figure 16). This criterion was used as the primary basis for evaluating the structural adequacy of the crane foundation region under all investigated loading angles.
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 69 Figure 16 Mesh size and stress limits (American Bureau of Shipping (ABS), 2019) Since the forces due to hull girder strength were not applied in the model, and in accordance with the aforementioned ABS rules, the allowable stress has been reduced by 10%. Consequently, the maximum permissible stress for the deck structure is considered to be 165 MPa. 4 Conclusion 4.1Simulation results The finite element results demonstrate that the forecastle deck structure in the crane foundation region satisfies the ABS allowable stress requirement under all investigated crane loading conditions. Tthe maximum Von Mises stress among the eight slewing cases occurs at a crane rotation angle of 180°, where the stress reaches 160.4 MPa, while the second highest value is obtained at 0° with 154.3 MPa. By contrast, the lowest stress is recorded at 315°, with a value of 105.6 MPa (Table 7). Since all calculated stresses remain below the allowable limit of 165 MPa, the deck structure can be regarded as structurally adequate for the considered static operating conditions. At the same time, the 180° case leaves only a limited safety margin of about 4.6 MPa, indicating that this loading direction governs the strength assessment of the crane foundation region. Table 7 Maximum von mises stress under different crane loading angles No. Angle Relative to Bow (°) Von Mises Stress (MPa) FigureNo. 1 0 154.3 15 2 45 111.0 16 3 90 139.3 17 4 135 112.8 18 5 180 160.4 19 6 225 117.0 20 7 270 137.6 21 8 315 105.6 22 The stress contour plots shown in Figures 17-24 further clarify the structural behavior behind the values listed in Table 7. In particular, the stress cloud corresponding to the 180° slewing condition (Figure 21) identifies the most critical stress concentration in the crane-supporting region, whereas the contours for 0° (Figure 17) and 270° (Figure 23) also show relatively high stress levels compared with the other loading cases. By comparison, the stress distributions for 45°, 135°, 225°, and 315° (Figure 18, Figure 20, Figure 22, Figure 24) are more moderate, indicating that these slewing directions produce a more favorable load-transfer path through the deck structure. Taken together, Table 7 and Figure 17, Figure 18, Figure 19, Figure 20, Figure 21, Figure 22, Figure 23, Figure 24 show that the structural response is strongly dependent on crane orientation and that a single loading direction would not be sufficient to identify the governing condition. Similar orientation-dependent stress redistribution has also been reported in crane-supporting marine structures, where different crane positions lead to different load-transfer paths and local reinforcement demands (Hernández-Ménez et al., 2023; Dragatogiannis et al., 2024). From the engineering point of view, these results indicate that the deck plating, girders, stiffeners, and supporting pillars are able to work together to transfer the crane load effectively into the surrounding structure. The highest stresses appear only in specific orientations,
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 70 which suggests that the local arrangement of supporting members plays a key role in controlling the load path and the resulting stress concentration. Therefore, although the current reinforcement scheme is sufficient for the investigated loading envelope, the regions associated with the 180° and 0° cases should be regarded as critical hot-spot zones for inspection and maintenance (Abdullah et al., 2023; Dragatogiannis et al., 2024). Figure 17 Von mises stress results at 0° crane rotation Figure 18 Von mises stress results at 45° crane rotation Figure 19 Von mises stress results at 90° crane rotation
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 71 Figure 20 Von mises stress results at 135° crane rotation Figure 21 Von mises stress results at 180° crane rotation Figure 22 Von mises stress results at 225° Crane Rotation Repeated crane operation in these unfavorable directions may increase the risk of fatigue damage in welded joints, girder intersections, and pillar-to-deck connections, even if the static stress remains below the allowable limit. This load-sharing mechanism agrees with previous marine structural studies showing that deck plating, longitudinal/transverse stiffeners, and supporting members jointly govern the local stiffness and stress response around crane foundations and similar equipment-support regions. Recent reviews further indicate that repeated loading/unloading, transient operational loading, and welded-detail geometry are among the key factors governing fatigue resistance in ship and offshore structures (Dong et al., 2022).
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 72 Figure 23 Von mises stress results at 270° crane rotation Figure 24 Von mises stress results at 315° crane rotation Several limitations of the present study should also be acknowledged. First, the analysis was based on a simplified geometric model in which local details such as cutouts, scallops, snipes, and other small discontinuities were not included, although such features may affect local stress concentration in practice. Second, the present assessment was limited to linear static analysis under calm sea conditions, and therefore did not consider dynamic effects associated with vessel motions, impact loading, or oscillation of the lifted load. Third, the study focused on rule-based strength verification and did not include a detailed fatigue assessment of the identified hot-spot regions. For these reasons, the present conclusions are suitable for preliminary structural verification, but they do not fully represent the complete long-term service behavior of the crane foundation structure. Future work should therefore extend the present analysis in several directions. A fatigue assessment should be performed for the most highly stressed regions identified in Figure 21 and the other critical contour plots. Dynamic loading conditions caused by vessel motion and crane operation in realistic sea states should also be considered in order to provide a more complete structural evaluation. In addition, local sub-modeling of the hot-spot regions would help capture stress concentration more accurately than the current global shell model. If higher lifting loads or more demanding operating conditions are expected in future service, structural optimization measures such as local plate thickening, bracket addition, or improved stiffener continuity may be investigated to increase the available safety margin and improve fatigue resistance. Moreover, refined local stress assessment methods should be considered for welded joints around the crane foundation, since hot-spot stress prediction can vary with the adopted finite element formulation and extraction technique (Li and Choung, 2021). Overall, by combining the numerical comparison in Table 7 with the stress contour interpretation in Figure 17, Figure 18,
International Journal of Aquaculture, 2026, Vol.16, No.2, 61-73 http://www.aquapublisher.com/index.php/ija 73 Figure 19, Figure 20, Figure 21, Figure 22, Figure 23, Figure 24, this study confirms that the deck structure in the crane foundation area is structurally acceptable under the considered crane loading cases, while also identifying the 180° slewing condition as the governing design case and the most important target for future fatigue assessment, maintenance planning, and possible structural refinement. Acknowledgement Thank to my spouse LIDA who has supported the implementation of this research, and SSCO shipyard for their supports. Conflict of interest The authors declare that they have no conflict of interest. Authors' contributions Farzad Tahmasebi (100% of contributions) including: conceived and designed study, collected and analyzed the data and writing conclusions. References Abdullah K., Sumardiono S., and Soeroso H., 2023, Strength analysis of the deck crane barge using the finite element method, in Proceedings of the 1st International Conference on Sustainable Engineering Development and Technological Innovation (ICSEDTI 2022), EAI, pp. 11-13. American Bureau of Shipping (ABS), 2019, Rules for Building and Classing Steel Vessels under 90 Meters (295 Feet) in Length, Part 3 - Hull Construction and Equipment, July 2019. American Bureau of Shipping (ABS), 2020, Guide for Fatigue Assessment of Offshore Structures. Dong Y., Garbatov Y., and Guedes Soares C., 2022, Recent developments in fatigue assessment of ships and offshore structures, Journal of Marine Science and Application, 21: 3-25. Dragatogiannis D.A., Zaverdinos G., and Galanis A., 2024, Structural analysis of deck reinforcement on composite yacht for crane installation, Journal of Marine Science and Engineering, 12(6): 934. Hernández-Ménez D.F., Félix-González I., Hernández J. H., and Herrera-May A. L., 2023, Methodology for the structural analysis of a main deck of FPSO vessel supporting an offshore crane, Revista UIS Ingenierías, 22(1): 1-16. Li C.B., and Choung J., 2021, A new method of predicting hotspot stresses for longitudinal attachments with reduced element sensitivities, International Journal of Naval Architecture and Ocean Engineering, 13: 379-395.
International Journal of Aquaculture, 2026, Vol.16, No.2, 74-89 http://www.aquapublisher.com/index.php/ija 74 Research Article Open Access Phytochemical Characterization and Anaesthetic Efficacy of Citrus Leaf Extracts for Sedation and Handling of Nile tilapia (Oreochromis niloticus) and African Catfish (Clarias gariepinus) Akpomughe E. 1 , Awhefeada O.K. 1, Mukoro J.E. 2, OkpuP.N. 3 1 Department of Fisheries and Aquaculture, Delta State University, Abraka, Nigeria 2 Department of Animal Production, Southern Delta University, Ozoro, Nigeria 3 Department of Entrepreneurship Development, Southern Delta University, Ozoro, Nigeria Corresponding email: akpomughee@gmail.com International Journal of Aquaculture, 2026, Vol.16, No.2 doi: 10.5376/ija.2026.16.0007 Received: 15 Jan., 2026 Accepted: 13 Mar., 2026 Published: 31 Mar., 2026 Copyright © 2026 Tahmasebi, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Akpomughe E., Awhefeada O.K., Mukoro J.E., and Okpu P.N., 2026, Phytochemical characterization and anaesthetic efficacy of citrus leaf extracts for sedation and handling of Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus), International Journal of Aquaculture, 16(2): 74-89 (doi: 10.5376/ija.2026.16.0007) Abstract This study investigated the anesthetic efficacy and safety of aqueous leaf extracts of Citrus sinensis, Citrus aurantium, and Citrus limon in Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) under controlled immersion conditions. Qualitative phytochemical screening revealed distinct variation in bioactive constituents among the extracts. Experimental exposure was conducted at concentrations ranging from 1 000 to 4 000 mg L⁻¹, and responses were evaluated using induction time, recovery time, survival, behavioural indicators, and flesh quality parameters. Anesthetic effects were concentration dependent in both species. Citrus sinensis produced mild to moderate sedation across all tested concentrations, with no mortality recorded even at 4 000 mg L⁻¹, indicating a wide safety margin, and 3 000 mg L⁻¹ was identified as the highest effective concentration for routine handling. In contrast, Citrus aurantium and Citrus limon induced deeper anesthetic states at lower concentrations but resulted in 100 percent mortality at 4000 mg L⁻¹ in both species. Fish exposed to Citrus sinensis exhibited more favourable post exposure welfare indicators, including faster recovery and earlier resumption of feeding, whereas the other extracts were associated with delayed recovery and behavioural impairment. These findings indicate that Citrus sinensis appears more compatible with short term handling welfare and represents a practical and cost effective botanical anesthetic for freshwater aquaculture. Keywords Fish anesthesia; Citrus leaf extracts; Clarias gariepinus; Oreochromis niloticus; Handling stress; Aquaculture welfare 1 Introduction Aquaculture has become an essential component of global food systems, contributing significantly to animal protein supply and economic development, particularly in developing regions. Species such as Clarias gariepinus and Oreochromis niloticus are widely cultivated due to their adaptability, rapid growth, and high market acceptance (Klimuk et al., 2024; Webster and Lim, 2024). However, routine aquaculture practices such as handling, grading, transport, and sampling expose fish to stress, which can negatively affect physiological stability, immune function, and overall productivity (Martos Sitcha et al., 2020; Dawood et al., 2022). The use of anesthetic agents is therefore essential to reduce stress, improve handling efficiency, and enhance fish welfare during aquaculture operations (Neiffer, 2021; Brønstad, 2022). Conventional fish anesthetics, including synthetic compounds, have been widely used due to their effectiveness in inducing rapid sedation and recovery. However, concerns have been raised regarding their cost, regulatory restrictions, potential toxicity, and residue accumulation in fish tissues (Vergneau Grosset and Benedetti, 2022; Sedyaaw and Bhatkar, 2024). These limitations have prompted increasing interest in the development of alternative anesthetic agents derived from natural sources. In particular, plant based anesthetics have gained attention due to their accessibility, lower environmental impact, and perceived safety in aquaculture systems (Yaşar and Yardımcı, 2022; Haihambo et al., 2023).
International Journal of Aquaculture, 2026, Vol.16, No.2, 74-89 http://www.aquapublisher.com/index.php/ija 75 Recent studies have demonstrated that plant derived compounds, especially those obtained from essential oils, can effectively induce anesthesia in fish. For example, eugenol based extracts and other bioactive plant oils have been shown to produce rapid induction and acceptable recovery profiles in several aquaculture species (Ventura et al., 2020; Zahran et al., 2021). Similarly, essential oil extracts such as chamomile oil and citronellal have been reported to exhibit anesthetic efficacy in fish, influencing behavioural and physiological responses during exposure (Ak et al., 2022; Hoseini et al., 2022). Reviews have further highlighted the growing application of essential oils as sedatives and anesthetics in aquaculture, with evidence supporting their role in improving fish handling and reducing stress (Rodrigues Brandão et al., 2022; Minaz et al., 2025). These findings indicate that plant based anesthetics represent a viable alternative to conventional synthetic agents. Despite these advances, several limitations remain in current knowledge. Most studies have focused on a limited number of plant species, particularly those rich in essential oils, while comparatively less attention has been given to aqueous leaf extracts from widely available tropical plants. In addition, there is limited comparative research evaluating multiple plant species under similar experimental conditions, especially with respect to induction time, recovery dynamics, survival outcomes, and post exposure welfare indicators (Haihambo et al., 2023; Mphande et al., 2023). Furthermore, the relationship between phytochemical composition and anesthetic performance is not consistently established, as many studies do not integrate chemical profiling with functional assessment of anesthetic effects. Citrus species represent a promising but underexplored source of bioactive compounds with potential anesthetic properties. Citrus leaves and by products are known to contain a wide range of phytochemicals, including flavonoids, limonoids, terpenoids, carotenoids, and phenolic compounds, many of which exhibit biological activity (Addi et al., 2021; Saini et al., 2022; Lu et al., 2023). Flavonoids and related compounds have been associated with antioxidant, antimicrobial, and physiological regulatory effects, which may influence stress response and metabolic processes in aquatic organisms (Barreca et al., 2020; Bhowal et al., 2022). In addition, citrus leaf extracts and essential oils have demonstrated bioactive properties, including antimicrobial and antiproliferative activities, indicating their potential for broader biological applications (Asker et al., 2020; Othman et al., 2022). The availability of citrus waste and leaf biomass further enhances their relevance as cost effective and sustainable resources for aquaculture applications (Russo et al., 2021; Maqbool et al., 2023; Šafranko et al., 2023). However, despite the documented phytochemical richness of citrus species, their anesthetic potential in fish has not been systematically evaluated. Existing studies have largely focused on nutritional, antimicrobial, or pharmaceutical properties, with limited attention to their functional role as anesthetic agents in aquaculture systems (Leporini et al., 2020; Zahr et al., 2023). Moreover, comparative assessments of different citrus species under controlled experimental conditions remain scarce, particularly in relation to key performance indicators such as induction efficiency, recovery time, survival rate, and post exposure behavioural responses. In this context, the present study aims to address these gaps by evaluating the anesthetic efficacy of aqueous leaf extracts of Citrus sinensis, Citrus aurantium, and Citrus limon in Clarias gariepinus and Oreochromis niloticus. Specifically, the study integrates phytochemical screening with functional assessment of induction time, recovery patterns, mortality outcomes, and welfare related behavioural responses. By providing a comparative analysis across multiple citrus species and linking phytochemical composition to anesthetic performance, this study contributes new evidence toward the development of plant based anesthetic alternatives for sustainable aquaculture practices. This study represents one of the first comparative evaluations of aqueous citrus leaf extracts as anesthetic agents in tropical aquaculture species. 2 Materials and Methods 2.1 Study location and experimental fish The experiment was conducted at the aquaculture research facilities of the Department of Fisheries and Aquaculture, Delta State University, Abraka, Nigeria. Nile tilapia (Oreochromis niloticus) and African catfish
International Journal of Aquaculture, 2026, Vol.16, No.2, 74-89 http://www.aquapublisher.com/index.php/ija 76 (Clarias gariepinus) were selected because they dominate aquaculture production in sub Saharan Africa and exhibit distinct physiological and behavioural responses to handling stress, making them appropriate models for anesthetic evaluation (Musa et al., 2021; Klimuk et al., 2024). A total of 180 healthy adult fish comprising 90 Nile tilapia and 90 African catfish were obtained from a commercial aquaculture facility in Warri, Delta State. The fish were size matched to ensure experimental consistency, with Nile tilapia having a mean body weight of 130 ± 10 g and total length of 16 ± 2 cm, while African catfish had a mean body weight of 200 ± 20 g and total length of 22 ± 3 cm. Fish were transported in aerated containers and acclimated for three weeks in 1 000 L circular tanks under continuous aeration. Stocking density was regulated to minimise crowding stress, and fish were fed once daily with a commercial extruded diet. Water quality parameters were monitored throughout acclimation and maintained within recommended ranges for tropical freshwater species to ensure that observed responses were attributable to treatment effects rather than environmental variation (Shaw et al., 2022; Zidan et al., 2022). Treatments that resulted in complete mortality were excluded from inferential statistical analysis because their inclusion would have introduced perfect separation of outcomes and artificially inflated variance, thereby violating the assumptions of parametric testing. Under such conditions, descriptive reporting is considered more appropriate and is widely adopted in fish anesthesia research where lethal thresholds produce non-variable outcomes (Neiffer, 2021; Soldatov, 2021) 2.2 Plant material collection and extract preparation Fresh leaves of Citrus sinensis, Citrus aurantium, and Citrus limon were collected from the university botanical garden, washed with distilled water, and air dried under shade at ambient temperature to preserve heat sensitive phytochemicals, as recommended for maintaining the integrity of plant secondary metabolites (Asker et al., 2020; Leporini et al., 2020). For phytochemical screening, dried leaves were milled into powder. Thirty grams of each sample were macerated in 120 mL of solvent for 12 h at 25 °C, followed by filtration, concentration using rotary evaporation, and drying in a water bath. The extraction procedure yielded approximately 8 to 12 percent of dry extract relative to initial plant mass, which is consistent with reported recovery ranges for citrus leaf phytochemicals (Cebadera Miranda et al., 2020). The dried extracts were reconstituted to 1 mg mL⁻¹ for qualitative analysis (Cebadera Miranda et al., 2020; Othman et al., 2022). For anesthetic trials, fresh leaves were homogenized in sterile distilled water and filtered through muslin cloth to obtain crude aqueous extracts. Filtration effectively removed coarse particulate material, although fine suspended particles remained, reflecting the use of minimally processed extracts. The reported concentrations therefore represent the mass of fresh plant material per unit volume of water rather than purified extract mass. Phytochemical screening was conducted using dried extracts to provide general chemical characterization, whereas fresh aqueous homogenates were used in exposure trials to simulate preparation methods applicable under practical aquaculture conditions. This dual approach ensured alignment between laboratory based analysis and field relevant application (Indriyani et al., 2023; Maqbool et al., 2023). 2.3 Phytochemical screening Qualitative screening was conducted to detect flavonoids, limonoids, terpenoids, phenolic acids, carotenoids, coumarins, essential oils, and alkaloids. These compound classes were selected based on documented associations with sedative activity, antioxidant function, and modulation of physiological responses in fish (Barreca et al., 2020; Bhowal et al., 2022; Šafranko et al., 2023). 2.4 Experimental design and anesthetic exposure Fish of each species were randomly assigned to four extract concentrations of 1 000, 2 000, 3 000, and 4 000 mg L⁻¹. Each treatment was replicated three times with ten fish per replicate, resulting in thirty fish per treatment per species.
International Journal of Aquaculture, 2026, Vol.16, No.2, 74-89 http://www.aquapublisher.com/index.php/ija 77 The selected concentration range was informed by preliminary range finding observations, which identified the lower threshold for observable behavioural response and the upper threshold associated with toxicity, and this range is consistent with dose selection strategies used in studies of plant derived anesthetics in fish (Ventura et al., 2020; Hoseini et al., 2022). Fish were fasted for 24 h prior to exposure to reduce metabolic variability and minimise the influence of feeding related physiological processes on anesthetic response (Martos Sitcha et al., 2020; Dawood et al., 2022). During exposure, aeration was suspended to facilitate uptake of anesthetic compounds across the gill surface, a procedure that has been shown to enhance immersion anesthesia efficiency (Brønstad, 2022). Anesthetic induction was assessed using behavioural criteria including reduced responsiveness, loss of equilibrium, and complete immobility. Following exposure, fish were transferred to clean aerated water, and recovery time was recorded as the time required to regain normal swimming behaviour. Mortality was assessed 24 h after exposure to determine safety margins (Neiffer, 2021; Soldatov, 2021). The level of replication employed is consistent with established experimental designs in fish anesthesia research, where the tank is treated as the experimental unit because fish within a tank experience identical exposure conditions and are not statistically independent (Neiffer, 2021; Vergneau Grosset and Benedetti, 2022). 2.5 Statistical analysis and welfare assessment Induction and recovery time data were analysed separately for each fish species. One way analysis of variance was applied within each extract type to evaluate the effect of concentration on induction and recovery time. Only treatments in which recovery occurred were included in the inferential analysis, as the inclusion of treatments with complete mortality can violate the assumptions of normality and homogeneity of variance and may lead to biased statistical outcomes (Neiffer, 2021; Vergneau Grosset and Benedetti, 2022). Prior to inferential analysis, all datasets were assessed for compliance with parametric assumptions. Normality of data distribution was evaluated using the Shapiro-Wilk test, while homogeneity of variance was examined using Levene’s test. These procedures confirmed that the data satisfied the assumptions required for parametric analysis, thereby justifying the application of one way analysis of variance. The use of these diagnostic tests is consistent with established statistical practice in experimental aquaculture research, where verification of distributional properties and variance structure is essential for ensuring the validity of statistical inference (Rodrigues Brandão et al., 2022; Minaz et al., 2025). Where significant differences were detected, mean values were separated using Tukey multiple comparison test, and statistical significance was accepted at p less than 0.05. All statistical analyses were performed using IBM SPSS Statistics software version 26.0. Although the experimental design incorporated multiple extract types and concentration levels, a factorial analysis of variance was not applied due to the occurrence of complete mortality in some treatment combinations. This resulted in an unbalanced dataset and violated the assumptions required for two way analysis of variance. Consequently, statistical analysis was restricted to biologically recoverable treatments, and one way analysis of variance was applied within these subsets to ensure valid estimation of treatment effects and to avoid distortion of variance structure, in line with recommended analytical approaches in fish anesthesia studies. Post exposure welfare was assessed through systematic observation of behavioural recovery after transfer to clean water. Observations were conducted at predetermined intervals during the recovery period, with frequent assessments within the first thirty minutes, followed by additional evaluations at one hour and twenty four hours, in order to capture both immediate and delayed behavioural responses. Behavioural criteria included opercular movement, swimming stability, restoration of equilibrium, and time to resumption of feeding. These indicators are widely recognised as reliable measures of post anaesthetic recovery and physiological status in fish (Martos Sitcha et al., 2020; Vergneau Grosset and Benedetti, 2022). Behavioural responses were documented using standardised descriptive criteria to ensure comparability across treatments (Neiffer, 2021).
International Journal of Aquaculture, 2026, Vol.16, No.2, 74-89 http://www.aquapublisher.com/index.php/ija 78 2.6 Flesh quality assessment Flesh quality evaluation was undertaken on fish exposed to citrus leaf extracts at a concentration of 3 000 mg L⁻¹, which elicited clear anesthetic responses without causing immediate mortality in the treatments considered. After complete behavioural recovery, fish were humanely euthanised in line with established practices for aquaculture research. Dorsal muscle tissues were excised immediately after euthanasia, placed on ice, and analysed within six hours in order to minimise post mortem biochemical changes that could influence flesh quality parameters (Shadieva et al., 2020; Ventura et al., 2020). Muscle pH was determined using a calibrated digital pH meter inserted into homogenised muscle tissue, a method routinely employed to assess post exposure metabolic condition and flesh stability in cultured fish species (Shadieva et al., 2020; Zahran et al., 2021). Crude protein content was analysed using standard wet chemistry procedures widely applied in fish nutrition and flesh composition research, while lipid content was quantified through solvent extraction techniques appropriate for detecting variations in muscle lipid reserves associated with handling stress and anesthetic exposure (Fawole et al., 2020; Shadieva et al., 2020). All biochemical determinations were conducted in triplicate, and results were expressed on a wet weight basis to ensure consistency with established reporting practices in aquaculture studies. Organoleptic assessment was performed to examine potential post anesthetic effects on flesh characteristics relevant to consumer acceptance. Evaluated attributes included flesh odour, texture, colour, and the presence or absence of off flavour characteristics. Sensory evaluation was conducted by a trained panel using established descriptive criteria commonly adopted in studies assessing the influence of handling stress and anesthetic agents on fish flesh quality (Ventura et al., 2020; Russo et al., 2021). These evaluations were qualitative in nature and intended to identify pronounced alterations in sensory attributes rather than to provide detailed quantitative sensory profiling, in line with the applied objectives of fisheries and aquaculture research (Zahran et al., 2021). 2.7 Ethical consideration All experimental procedures involving fish were carried out in compliance with internationally recognised guidelines governing the care and use of aquatic animals in research. Handling time and exposure duration were kept to the minimum necessary to limit stress, and any fish showing signs of severe distress were promptly removed from the experimental tanks. Throughout the study, established institutional best practices for ethical research involving live aquatic organisms were strictly observed. 3Results All tables and figures are explicitly referenced within the text. Phytochemical variation among the citrus extracts is presented (Table 1), behavioural responses are summarised (Table 2 and Tables 3), mortality outcomes are shown (Table 4), and recovery dynamics are quantitatively illustrated (Figure 3), while qualitative behavioural recovery patterns are shown (Figure 1)” (Neiffer, 2021; Mphande et al., 2023).Statistical analyses were conducted using tank means, with the tank treated as the experimental unit (n = 3 per treatment). Although this level of replication is consistent with controlled aquaculture experiments, the relatively small sample size may limit statistical power and should be considered when interpreting the results. 3.1 Phytochemical composition of citrus leaf extracts The qualitative phytochemical composition of the aqueous citrus leaf extracts is presented (Table 1). Distinct variation was observed in the distribution of bioactive compounds among the three citrus species. Citrus sinensis contained flavonoids, limonoids, terpenoids, phenolic acids, carotenoids, and coumarins, but did not show detectable levels of essential oils or alkaloids. Citrus aurantium contained flavonoids, limonoids, carotenoids, coumarins, essential oils, and alkaloids, but lacked terpenoids and phenolic acids. In contrast, Citrus limon contained limonoids, phenolic acids, coumarins, and essential oils, but lacked flavonoids, terpenoids, carotenoids, and alkaloids. These findings are based on qualitative phytochemical screening and were not
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