The influence of hydrobionts on net construction

Abstract

Abstract The study investigates the influence of hydrodynamic backwater on trawl cod-end performance. Conventional biomass‑assessment models fall short in open‑water fisheries, leading to the adoption of hydrodynamic backwater as a critical variable affecting catch‑efficiency. A numerical framework grounded in Navier–Stokes equations and the vorticity‑stream function (ω–ψ) formulation is constructed to simulate cod-end flows under varying design parameters—including inlet diameter, mesh spacing, mesh orientation, and trawling speed. Experimental simulations identify optimal geometries that minimize hydrodynamic backwater and maximize catch‑efficiency. Findings reveal that a reduced inlet diameter and mesh spacing combined with a T90 mesh orientation cut hydrodynamic backwater by 15–20 %. Hydrodynamic backwater escalates sharply at higher trawling speeds, diminishing efficiency; the optimal speed window is 1.5–2.5 m/s. The ω–ψ solutions closely match hydro‑channel experimental data, validating the model’s accuracy. These results emphasize the necessity of incorporating hydrodynamic backwater considerations into net design and provide concrete recommendations for structural optimization to improve trawl performance. Future work should explore adaptive mesh configurations that respond to real‑time hydrodynamic conditions, integrating machine‑learning algorithms to predict optimal mesh spacing and orientation, thereby further reducing hydrodynamic backwater and enhancing selectivity while maintaining high catch rates across diverse pelagic species.