New Delhi, 23 December (NNS): Here, the prices of black pepper remained firm at Rs 720 per kg due to the sluggish prices even after the improvement in the prices. Recently, the prices have improved by Rs 5 per kg. The trading activities reported to be sluggish due to the Christmas and the prices held stable at the same level of the previous day in Kochi. The prices will likely to remain sluggish during the coming days.