Is the ocean food provision index biased?

How close to maximum sustainable food provision is current seafood
harvest from the world’s oceans? Halpern et al.1 suggest that the
answer is 25% from a global index of food provision, part of their
multifaceted index of ocean health. Rigorous methods used for
management, however, demonstrate that their food provision index
is uncorrelated with actual food provision, and that global ocean food
provision is in the range of 71–95%. Their results stem from an
uncertain method of estimating maximum sustainable yield (MSY),
and we believe that this approach should be avoided as a measure of
food provision. There is a Reply to this Brief Communication Arising
by Halpern, B. S. et al. Nature 495, http://dx.doi.org/10.1038/nature11975
(2013).