[OS X TeX] pdfcrop

[pacotomi]

Hi,
I use pstricks via pdftricks (more precisely, H. Schulz version). I have installed MacTeX 2016 and recently Mac OS 10 Sierra.
Now, pdfcrop (called by Schulz's pdftricks) fails to find gs and gives an error.

With the terminal, pdfcrop finds gs in /usr/local/bin/

PDFCROP 1.38, 2012/11/02 - Copyright (c) 2002-2012 by Heiko Oberdiek.
* Restricted mode: disabled
* Option `pdfversion': auto
* Perl executable: perl
* Perl version: v5.18.2
* Pointer size: 8
* Pipe support: yes
* Fork support: yes
* OS name: darwin
* Arch name: darwin-thread-multi-2level
* System: unix
* Not found (gs): /Users/frederic/perl5/perlbrew/bin/gs
* Not found (gs): /Library/TeX/texbin/gs
* Not found (gs): /usr/local/gs
* Found (gs): /usr/local/bin/gs
* Autodetected ghostscript command: gs

But used with pdftricks, pdfcrop doesn’t search gs in /usr/local/bin/

PDFCROP 1.38, 2012/11/02 - Copyright (c) 2002-2012 by Heiko Oberdiek.
* Restricted mode: disabled
* Option `pdfversion': auto
* Perl executable: perl
* Perl version: v5.18.2
* Pointer size: 8
* Pipe support: yes
* Fork support: yes
* OS name: darwin
* Arch name: darwin-thread-multi-2level
* System: unix
* Not found (gs): /usr/bin/gs
* Not found (gs): /bin/gs
* Not found (gs): /usr/sbin/gs
* Not found (gs): /sbin/gs
* Not found (gs): /usr/texbin/gs
* Not found (gs): /Library/TeX/texbin/gs
* Not found (gs): /usr/local/texlive/2016/bin/gs

How cans I tell pdfcrop to look for gs in the right place?
(parenthetically, I have made a symbolic link and all is now OK but I do not understand why pdfcrop looks for gs in so strange directories)

Frédéric