Add a note to the manual about the fish shell.

doc/syntastic.txt

@@ -30,6 +30,7 @@ CONTENTS                                                  *syntastic-contents*
     6.Notes........................................|syntastic-notes|
         6.1.Handling of composite filetypes........|syntastic-composite|
         6.2.Interaction with python-mode...........|syntastic-pymode|
+        6.3.Interaction with the fish shell........|syntastic-fish|
     7.About........................................|syntastic-about|
     8.License......................................|syntastic-license|
 
@@ -484,6 +485,18 @@ python-mode, by setting |pymode_lint_write| to 0. E.g.: >
     let g:pymode_lint_write = 0
 <
 
+------------------------------------------------------------------------------
+6.3 Interaction with the fish shell                           *syntastic-fish*
+
+At the time of this writing the 'fish' shell (see http://fishshell.com/)
+doesn't support the standard UNIX syntax for file redirections, and thus it
+can't be used together with syntastic. You don't need to change your login
+shell to address this problem, but you do have to point Vim's 'shell' to a more
+traditional shell, such as 'zsh', 'bash', 'ksh', or even the original Bourne
+'sh': >
+    set shell = 'bash'
+<
+
 ==============================================================================
 7. About                                                     *syntastic-about*