Port Taranaki's net profit after tax for the first half of the 2018-2019 financial year has dropped a dramatic 35 percent to $4 million.
Revenue for the six months to 31 December, however, was more stable, down only 2.5 percent to $23.7m.
Chief executive Guy Roper said one-off expenditure items had impacted on the result.
"We have made significant investments and changes to our business during the period to grow trade, adapt to changes in the shipping industry, meet our customers' needs, and make us sustainable in the long term," Mr Roper said.
Operating costs increased 14 percent to $17.3m as the port repurposed buildings and cleared land to accommodate changing trade patterns.
"This work has included the removal of the coolstore on Blyde Wharf to allow for increased berth-side storage space for the growing log trade, the repurposing of the Craig Norgate Store to accommodate a customer's requirement for greater on-site animal feed storage, and the removal of other buildings to allow space for future development or storage," Mr Roper said.
Total trade volumes were down 10 percent to 2.6m tonnes through a combination of outages and maintenance shutdowns in the oil and gas sector, and reduced demand for supplementary animal feed.
Mr Roper said bulk liquids trade was down 16 percent to 1.7m tonnes, while dry bulk was down 9 percent to 381,000 tonnes.
"The Pohokura gas pipeline outage and a maintenance shutdown at Methanex resulted in reduced production, while our dry bulk trade was down, but this must be viewed in context of the extraordinary trading conditions for the first half of last year."