Updates on the SCAL assessments of eastern and western Atlantic bluefin tuna

SCAL assessment results presented in Butterworth and Rademeyer, 2015a and 2015b are refined to allow, in particular, for an improved treatment of catch-at-length data to avoid needing to deal with a large number of zero proportions for certain length groups. For both east and west assessments, the primary results is to change results in a direction that brings them into closer agreement with the VPA results.