Energy and chemical revenues decreased by approximately 4% in the first quarter to €18.2 million from €18.9 million in the same quarter last year, primarily as a result of lower pulp production at our Celgar mill.
Pulp production decreased by approximately 5% to 361,164 ADMTs in the current quarter from 380,342 ADMTs in the same quarter of 2012, primarily due to decreased pulp production at our Celgar and Stendal mills. We have 11 days (approximately 16,000 ADMTs) of maintenance downtime scheduled for our Celgar mill in the second quarter of 2013 in order to perform annual maintenance.
Pulp sales volume decreased by approximately 7% to 356,660 ADMTs in the current quarter from 384,826 ADMTs in the comparative period of 2012, primarily due to lower sales to China and the United States. Average pulp sales realizations decreased by approximately 3% to €499 per ADMT in the first quarter of 2013, compared to €512 per ADMT in the same period last year, due to lower pulp prices and a weaker U.S. dollar.
Costs and expenses in the first quarter of 2013 decreased by 7% to €188.7 million from €202.1 million in the comparative period of 2012, primarily due to lower pulp sales volumes and fiber costs, partially offset by higher natural gas costs at our German mills resulting from higher usage and prices.On average, our overall per unit fiber costs in the current quarter decreased by approximately 2% from the same period in 2012. Selling, general and administrative expenses decreased to €8.9 million in the first quarter of 2013 from €10.1 million in the first quarter of 2012. For the first quarter of 2013, operating income decreased to €9.5 million from €16.2 million in the comparative quarter of 2012, primarily due to the combined effect of lower pulp prices and sales volumes.