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Codend selectivity

In 2009 we compared the selectivity of four codends on the F/V Lauren Dorothy over a 13-day period. The codends tested were constructed from: 

  • 6.5" diamond mesh 
  • 6.5" square mesh 
  • 7.0" square mesh 
  • 6.5" composite codend 

A 2" diamond mesh cover net was placed around each codend to retain fish that escaped through codend meshes. We completed 79 tows in total (19 or 20 one-hour tows for each codend) and sampled the codend and cover net catch from each tow. 

We found that: 

  • Between 69% - 89% of non-commercial species and 37% - 52% of commercial species escaped through the codend meshes and were retained in the cover net 
  • The commercial catch was dominated by American plaice (dabs), grey sole, skate, and monkfish 
  • The 6.5" square mesh codend retained the highest proportion of legal and sub-legal dabs and grey sole (Fig. below) 
  • The 7.0" square mesh codend retained more legal dabs and grey sole than the 6.5˝ diamond mesh codend, but similarly low proportions of sub-legal sized dabs and grey sole 
  • At least 94% of legal sized monkfish were retained in each codend, and at least 83% of sub-legal monkfish 

 
Figure: Catch weight and proportions (in brackets) of dabs (top) and grey sole (bottom).