During the three months ended December 31, 2012, we recorded $16.5 million, or $0.78 per share, of net unrealized appreciation on portfolio investments, primarily due to the reversal of prior year unrealized depreciation due to realization on our investments in BioEnergy and Bionol of $21.8 million, partially offset by the reversal of prior period unrealized appreciation due to realization on our investments in Tammany overriding royalty interests and warrants of $2.9 million, and a decrease in the estimated fair value of our investments in GMX Resources, Inc. ("GMXR") Subordinated Notes and common stock totaling $2.8 million. Net increases in the estimated fair value of our remaining investments totaled $0.4 million for the three months ended December 31, 2012. During the three months ended December 31, 2011, we recorded net increases in unrealized depreciation on portfolio investments totaling $2.3 million, primarily as a result of a $2.4 million mark-to-market reduction in the fair value of our GMXR Senior Convertible Notes due 2013, with other net changes in fair value offsetting one another.
In November 2012, we repurchased a total of 358,096 shares of our common stock in the open market at an average price of $7.13 per share, totaling $2.6 million, in accordance with the stock repurchase plan approved by the Board of Directors in October 2011. For the year ended December 31, 2012, we purchased a total of 608,125 shares of our common stock at an average price of $6.89 per share, totaling $4.2 million. Under the terms of the stock repurchase plan, we have remaining authorization to repurchase up to an additional $5.8 million of common stock.
Overall, we had a net decrease in net assets resulting from operations of $0.2 million, or $0.01 per share, for the three months ended December 31, 2012. Our common stock repurchases during the quarter had a $0.04 per share positive impact on net asset value and, after declaring dividends during the period of $0.16 per common share, our net asset value decreased from $9.70 per common share as of September 30, 2012 to $9.57 per common share as of December 31, 2012.