Larger water piping critical to the survival of one of the oldest fish farms in the British Isles can be installed on land in Co Antrim, the High Court ruled on Tuesday.
A judge held that plaintiffs Lee Beverland and Naomi Liston are legally permitted to replace an existing structure near the banks of the River Maine in Randalstown.
His verdict gives the green light for hydro-electric power enabling the facilities to operate more intensely.
Mr Beverland and Ms Liston own the land on Otterburn Fish Farm has been located since the mid 1970s.
Built on the site of an old paper mill once owned by the grandfather of Henry Joy McCracken, its history can be traced back to 1737.
The area is bordered by fields owned and farmed by the late John Hughes.
Under a deed dating back to 1976 Otterburn's previous owners had the right to install and maintain water pipes from adjoining lands, the court heard.
Proceedings against the deceased's personal representative centred on whether this grant of easement permitted the plaintiffs to replace 1.8 metre diameter piping with a rectangular construction measuring 2.2 metres by 5 metres in dimension.
Mr Justice Horner was told the fish farm will be unable to operate commercially in future unless the bigger pipe is installed to carry additional water.
He accepted that without the benefit of the hydro-electric power capital investment for modernising the facilities would not be available.
"The replacement piping, bringing with it the benefits of cheaper power and more intensive farming methods, is critical to the long-term survival of Otterburn as a fish farm and its continuing operation as a viable enterprise," the judge said.
The court also heard how a study in 2009 concluded that a 200kw hydro-electrical system eligible for grant funding up to a maximum of £20,000 was viable for the location.
Rejecting any suggestion that the plaintiff's primary intention had been operating a fish farm, Mr Justice Horner held the aim of the original scheme was to produce electricity for sale to the grid.
The deceased, he concluded, could not have understood the plaintiffs' precise intentions following meetings to discuss the plans in 2010.
He pointed to subsequent correspondence from Mr Hughes' solicitors which insisted the deed didn't permit enhancement or enlargement of the pipe.
However, further declarations that electricity would not be supplied to the grid were described as a major change in the plaintiffs' strategy.
The case they made was that a hydro-electric power plant on their land would be for purposes related to the fish farm, although surplus power generated may at times be sold at the appropriate tariff.
Delivering judgment, Mr Justice Horner held that the installation of a larger pipe over the defendant's field - provided it is to be used on the fish farm.
"The diversion of water through the pipe, whether old or new, is only lawful insofar as it is for the primary purposes of a fish farm," he said.
The judge added: "This will permit it to function as a viable economic enterprise. Without the larger pipe, no commercial fish farm can operate on this site."