Thank you Capt Ted and Kyle for your explanation re the connection of the barge and tug.Best regards to all.

I thank you Captain Ted and Kyle for your indeed expert explanation (description + appropriate photograph) re: connection/connecting together the Tug and Barge.
Much obliged,
Jadran

For the most part, the connecting system is two sockets, one on either side of the barge's notch, and corresponding pushrods on either side of the tug's bow that couple into the sockets. A view of the connectors may be seen on this view of the tug FREEPORT.
Kind Regards, Kyle

@ Emanuelle
look here : http://www.shipspotting.com/gallery/photo.php?lid=1996424
They moving in position and are then "jacked up" into a recess and then interlocked by that bolt like hydraulic device. These types are also designed to stay together at sea. Others going into the gap on the aft of the barge and tied in via cables which is done often with older tugs and smaller units. They usually disconnect at sea and go in front of a barge and towing the barge.
Look up my site under tugs, tugs and tow and you will find all types.

Incidentally how is the tug and barge combination coupled, I don't think it is a simple tie up with hawsers and the tug just pushing, it must be some sort of mechanical coupling.Anyne has more info?

ITBs are common in the United States because, being technically a tug and a barge, they are less costly to operate than a ship. That is because tug boats require a smaller number of crew members, and their pay-scales are lower, than crew members on corresponding full-sized ships.

@Jadran
not really, here in the Americas and there special between Caribbean Islands/Central America and the US they are quite numerous. Between US ports they are virtually the only "over"seas transport (beside the intracoastal waterway) beside OSG who has a few tankers. But generally there are plenty of them, but going rather rarely world wide.
Just look up my tug pages and you will find a bunch of them for examples these
http://www.shipspotting.com/gallery/photo.php?lid=2051187

http://www.shipspotting.com/gallery/photo.php?lid=2041956

@ Emmanuel
This kind/type of dry-cargo vessels like ITB STRONG-MARINER including also the ITB product tankers are trading world-wide,, unfortunately they are nowadays in less-and-less number present on the seas :-)
With very best regards
Jadran

@ davidships
You are completely right in your statements;
1) The Ro/Ro cargo barge MARINER indeed has its own IMO number being 8646537,, this fact I didn't know before !!!
2) For the sake of the "literature" title of this photo, I propose, that we let it remain as it is.
ITB is a prefix used for Integrated Tug Barge units like it is M/V used for motor vessels (e.g. when you write: Drydocking Specifications for ITB GROTON and Drydocking Specifications for M/V MATZ MAERSK)

@ REG, Clyde and Captain Ted
Thank you very much for your kind & interesting comments !

With very best regards
Jadran

A rare catch Jadran, can anyone tell us where these vessels operate, and are they that rare as I think they are ?(I maybe mistaken mind you)

@ davidships,, you are correct a "ITB" preceding a tugs name is to my knowledge never done. and yes,,tug and barge have usually both a IMO number,,also when usually they stay together for life.

Just to make it a bit more complicated, the barge MARINER has its own IMO 8646537.
The tug is just plain STRONG, without "ITB"

Well done jadran. All very interesting and educational. And a good angle to show of her features

The only reason vessels such as this exist is to enable the shipowners can take advantage of a loophole in the law. Technically, these vessel are a tug pushing a barge. Consequently, they only have to employ a tugboat-sized crew, with tugboat certification, and paid tugboat-scale wages.

No problem Jim it's OK, I was just clarifying.
Regards
Ken

Thank you Jim and Ken,, for your comments and clarification of this *interesting configuration* i.e. Integrated Tug Barge (ITB).
Kind regards
Jadran

Integrated Tug Barge (ITB) Jim, a pusher Tug with Barge Mariner, so in correct category.
Regards
Ken