Estimating the Physical Behaviour of Seine Ropes for Evaluating Demersal Seine Fishing Reporting on experiments in the flume tank

Abstract

Demersal Seining is an active fishing method which is based on seine ropes and a seine net. The seine ropes and net are laid out on the fishing ground in a way that they encircle an aggregation of fish. Because the area the seine ropes encircle is much larger than area swept by the seine net during the hauling process, the catching efficiency of a demersal seine depends to a large extent on the herding efficiency of the seine ropes. During the fishing operation, the fish is gradually herded by the seine ropes into the path of the net. Knowledge about how the size and shape of the area encircled by the seine ropes gradually change during the fishing process is important for an efficient fishery. The purpose of the project ”Danish Seine: Computer based Development and Operation” (MAROFF-2 project no. 225193 / FHF 900861), funded by Research Council of Norway (RCN) and Norwegian Seafood Research Fund (FHF), is to develop software tools to investigate Danish Seine fishing. An important aspect of the research is to be able to simulate the physical behaviour of the seine ropes during the fishing process. This report describes flume tank experiments carried out with the purpose of later being able to validate a numerical simulation model for seine rope behaviour. The flume tank experiments were conducted by using two rope with varying physical properties and by varying the initial shape of ropes. The seine ropes were hauled back from the tank floor at different speeds. We applied a motion tracking system based on stereo vision with six underwater cameras to record the gradual change in the geometry of the area defined by the ropes. Information about the kinematic behaviour of the seine ropes and its dependency on its physical properties, initial layout pattern and hauling speed were acquired.