Calculation sequence for determining the construction parameters of a gillnet: a case study

Abstract

Gillnet performance is largely determined by construction and rigging parameters that control gear shape, stability, buoyancy, ballast, and ultimately fishing efficiency. However, the technical calculations needed to define these parameters are frequently dispersed in specialized literature, limiting their standardized application in artisanal fisheries. This study presents a stepwise calculation sequence for estimating the principal design parameters of gillnets, including twine requirements, hanging twine length, netting weight in air and water, buoyancy force, ballast needs, and the number of floats and sinkers. The proposed framework integrates established technical criteria for rope diameter, twine thickness, and hanging coefficients, offering a practical basis for gear design, adjustment, and evaluation. Its applicability was examined using an artisanal fixed surface gillnet operated in San Juan de Urabá, Colombian Caribbean, by contrasting calculated values with the gear configuration used in practice. Results indicated partial agreement with technical recommendations: while the upper selvage rope and main netting twine were within acceptable ranges, the lower selvage rope, hanging twine diameter, and hanging coefficient showed departures from expected values. In addition, the gear displayed a tendency toward excessive buoyancy and insufficient ballast, which may reduce operational stability, affect selectivity patterns, and limit overall fishing effectiveness.