New Zealand King Salmon says the "extraordinarily hot summer" has cut survival rates at its fish farms in the Marlborough Sounds and it expects weaker second-half earnings after profit in the first half soared 81 per cent.
Profit rose to $15.7 million in the six months ended December 31 from $8.7m a year earlier, the company said today.
Sales climbed to $87.7m from $63.6m.
Chairman John Ryder says King Salmon remains positive about the longer-term prospects having experienced strong demand for its fish in the first half.
It would give an update on the impact of the hot summer once it had done a full assessment.
Favourable growing conditions during the 2017 financial year allowed it to deliver additional volume to satisfy demand.
"However, the situation has now become more challenging.
"The extraordinarily hot summer has impacted the survival rates of our King Salmon, and this will be a principal factor behind an anticipated reduction in profits for the second half."
King Salmon is also working through the process of relocating its farms to areas of the Marlborough Sounds with higher flow rates and further from where people live.
Rule changes mean some farms will be marginal on existing sites.
King Salmon will pay a fully imputed dividend of 2 cents a share.
It sold 4392 tonnes of gilled and gutted salmon in the first half, up 17 per cent on the year earlier, and average selling prices rose, led by its premium Ora King brand.
King Salmon shares last traded at $1.99 and have gained 47 per cent in the past 12 months.