Southland has the worst record for oil spills nationally, Maritime New Zealand data shows.
From 2012 to 2014, 14,709 litres of oil was spilled in Southland, ahead of Canterbury with the second highest total of 9466 litres. The Canterbury total excluded a spill by Mobil in March involving 1.2 million litres.
Environment Canterbury (ECan) harbour master Jim Dilley said its research showed fishing boats were the biggest culprits, with spills occurring when vessels were refuelling or doing transfer operations.
Spills in Canterbury from fishing boats include seven from New Zealand, five from Korea and two from Britain.
"We've probably got the largest number of fishing fleets, but also we have two harbours which come under the ECan banner at Lyttelton and Timaru," Dilley said.
It was well-known among the "harbour master community" that Canterbury had the worst reputation for oil spills because of the large quantities of litres spilled each incident, he said.
"But we are turning that [reputation] around. ECan are taking a proactive approach to enforcement hoping to drive home to people that if you spill oil it will hurt you financially.
"I understand that accidents do happen but any oil spill in water is a bad spill."
Since 2012, ECan has issued eight fines for $500 each. In February 2012, a 2500-litre diesel spill in Timaru by Sanford's San Enterprise fishing vessel resulted in a $30,000 fine and $38,000 in costs.
ECan has also issued three warning letters and charged offenders with cleanup costs.
NZ OIL SPILLS
Southland: 5001 litres (three incidents)
Canterbury: 1540 (five incidents) - does not include Mobil's March spill involving 1.2 million litres
Taranaki: 201 (13 incidents)
Wellington: 100 (one incident)
Auckland: 84 (nine incidents)
- The Southland Times
Should April Miller be allowed to play in the presidents grade rugby competition?Related story: Southland woman banned from men's rugby side
Subscribe to a digital replica of The Southland Times.
Southland Times subscriber news and information.
Click here for information about advertising with The Southland Times.