Gillnet Weak Link & Buoy Line Marking Techniques 

Gear Research Team
Protected Resources Division
NMFS, Northeast Region 

  
Plante’s Lobster Vents, Inc.  is currently developing a swivel that incorporates a weak link.  It can be manufactured for different strengths (500, 600, 1100 etc.) as required.  They are expected to be available around the first of the year.   [Click here for picture plante.jpg] 

 
A weak link technique suitable for higher loads is a spliced jumper.  The jumper is selected based on breaking strength data from the manufacturer. [Click here for picture jumper.jpg] 

 
Shown below are 2 methods of incorporating weak links into a gill net float rope.  The top one shows a weak link jumper spliced into the float rope.  The overhand knot in the jumper reduces its strength to about 60% of its original strength.  For example, putting an overhand knot in a piece of 5/16" polypropylene that has an original tensile strength of 1710 pounds will make the rope fail with a load of about 1025 pounds.  The bottom picture shows a weak link tied into the float rope with fisherman’s knots.  These knots also reduce the strength of the rope to about 60% of its original strength. [Click here for picture g1.jpg  -  Click here for picture g2.jpg] 

 
Buoy lines can be marked in a variety of ways.  Shown below are three simple methods that were tested and found to work satisfactorily under normal conditions.  At the top, colored twine is seized around the line and woven between the strands.  In the center the line was spray painted.  This method requires that the rope be dry.  At the bottom,  colored electrical tape was wrapped in one direction and then back over itself to form two layers.   [Click here for picture marking.jpg]