Dog Grabs Duck - Appeal

Just before 12 today, I witnessed an unattended white and brown Spaniel taking a duck from the riverside behind the Seaman's hall in Fishertown. I was unable to stop it running away with the bird, but have informed the Police and SSPCA. After spotting the Spaniel accompanied by a Black Labrador as well. I have made some initial local enquiries and believe I now know both dogs names. The Spaniel is called "NIP" and the Labrador is called "MULL". resident in the Fishertown area.
The Trust would appreciate the name and address of the owners, to assist with their enquiries, in confidence.
Most of the birds on the River just now are completely defenceless, they are either Moulting or too young to fly. It is irresponsible to allow gun dogs, or hunting type breeds, to roam the riverside unattended and out of control !  The Trust is duty bound to protect our river wildlife, and spends time, money, and effort in this regard. Having seen the speed and stealth of this spaniel, I have no doubt it will take birds at every opportunity. IT MUST BE STOPPED!