Deep sea moorings fishbite handbook

Abstract

The purpose of this handbook is to bring awareness and a degree of expertise to the very real problem of fish attacks on mooring lines and cables deployed in the open seas. Over the years the authors have carefully examined a large sample of damaged, sometimes entirely severed ropes retrieved from the sea. Often direct evidence and/or biological observations showed that the ropes were the victims of fish attacks. In many cases however the cause of rope failure remained difficult to ascertain. Techniques and rationales therefore had to be devised to elucidate the more thorny cases. Understanding a problem, the saying goes, is half of the solution. The other half, as far as this handbook is concerned, is of course to make known the ways which, at the moment, could help prevent fishbite attacks or at least abate its effects. Thus the handbook will follow a natural progression. A short introduction retraces the early suspicions which soon translated into confirmed fish attacks. The next two chapters cover the recognition and the extent of the fishbite problem in great depth. Chapter 2 presents in meticulous details the techniques which can be used to determine how a rope was damaged while in service, either by fishbite or any other plausible cause. The analysis of a data base which spans over twenty years and encompasses close to a thousand moorings is presented in Chapter 3: Dimensions of the fishbite problem. This chapter provides valuable information for use in estimating fishbite hazard. Who are the culprits and why they do it is reviewed in Chapter 4: Biting organisms and predisposing factors. This chapter identifies the marine organisms which have significant biting capabilities and outlines some of the environmental factors and processes which incite and result in fishbite damage. The last chapter: Prevention and control of fishbite damage, reviews the preventive methods used to reduce the incidence or the severity of fish attacks and the curative methods - including up to date techniques for jacketing metallic and non-metallic ropes and cables - which hopefully will protect mooring lines from the mechanical damage inflicted by fish teeth.