Before April 1, boats could empty their waste while in the harbour, but new council rules now prohibit vessels from doing so.
Scarborough Council portfolio holder for harbours, Cllr Mike Cockerill, said: “We have no evidence that anybody is doing it, but because of the bathing water quality at Scarborough South Bay, we want to take proactive measures.
“It’s a case of doing anything that we can to improve the bathing water quality.
“Most boat owners are very environmentally inclined.”
A spokesman for Scarborough Council added: “This measure is designed to help protect the water quality within our areas and make our seas cleaner for both humans and wildlife.” Dye tablets could also be introduced to make identifying offenders easier.
It is believed that Yorkshire harbours will be the first in the United Kingdom to use this innovative approach to identify polluters and these measures have been welcomed by the harbour community and the Yorkshire Bathing Water Partnership.
The council spokesman added: “You can do your bit as a harbour user by sticking to these rules and reporting anybody who you suspect is not doing so.”
The Whitby harbour area is designated as everywhere that the sea flows up to the mean high water spring mark from Ruswarp Weir, to the end of the piers and then the open sea extending to two nautical miles north, 1.5 nautical miles westward and one nautical mile eastward. The harbour jurisdiction and rules may extend up to two miles offshore.
Holding tanks can only be emptied more than three miles offshore, in the open sea, where waste will be quickly diluted and dispersed by wave action and currents. Where possible, tanks should be discharged even further offshore so that waste is not carried back towards the coast and beaches.
For more information on the new harbour rules, visit: www.scarborough.gov.uk.