As I don't have a running linix box at present I'm not up on the capabilities of aircrack-ng
Possibles: iStumbler at http:istumbler.net Of the fairly sparse field,this one is probably the most current.
KisMac is a older port of Kismet last released in 2006, but reported to work on Snow Leopard. Haven't tried it.
Another possible useful tool is WireShark. You will need to install XQuartz to use it, as it's an X11 windows app.
A final possibility is to install windows under VirtualBox, Parallels or VMFusion and give it full access to your ethernet cards.
Based on the clarification in your comment, I think wireshark would do what you want if you want to look at traffic.
If you just want to count packets, you can use netstat. This is a terminal program. (see man netstat)
~/Webwork/sftf
647 ==> netstat -w10
input (Total) output
packets errs bytes packets errs bytes colls
73 0 17551 77 0 11256 0
31 0 4731 41 0 6891 0
-w10 gives you a record every 10 seconds. If you wanted hourly records you'd use -w3600.
Netstat is general purpose. If you have multiple interfaces, you can filter to a given one with the -I flag. You can also do some filtering by protocol, address family.
If you need serious filtering (I want to know how many packets bitorrent sent to the pirate bay last week) then you need either wireshark or tcpdump. (Tcpdump is commandline) Wireshark is basically a GUI on top of tcpdump. Both have their place.