Since X11 is no more included, you need XQuartz to run Wireshark on Yosemite. Wireshark is expecting XQuartz (X11) to be inside the folder “/usr” but it is now under “/opt”. With a symbolic link you can solve it easily.

# create symbolic link
$ sudo ln -s /opt/X11 /usr/X11

After install and create symbolic link you download can install Wireshark. Now you can start Wireshark.

# start wireshark
$ sudo wireshark

Note: The start may take some time.