Polymer producer Victrex topped the the risers on the FTSE 250 after it reported a six per cent rise in sales in the first quarter of 679 tonnes, in line with expectations. The company said the second quarter had 'started well' with January sales in excess of 330 tonnes.Premier Oil surged following its announcement Chief Executive Simon Lockett is stepping down from the company after nine years in the role.Meanwhile, electronics and maintenance products distributor Electrocomponents sank despite meeting estimates with underlying sales growth of 2% in the four months through January.African Barrick Gold tracked the price of gold lower. The company said this morning that it has completed the transfer of the Tulawaka mine to Stamico, the Tanzanian state mining company. Hit by the news that annual losses had widened significantly last year, Ocado also took its place in the top 10 fallers. The online grocery group said that despite decent top-line growth, earnings suffered as both costs and expenses soared. Shares were also down after the company said that the group's co-founder and current Commercial Director, Jason Gissing, is to retire.FTSE 250 - RisersVictrex (VCT) 1,952.00p +10.66%Premier Oil (PMO) 295.20p +10.11%Jupiter Fund Management (JUP) 379.90p +4.80%Riverstone Energy Limited (RSE) 901.00p +2.39%Rotork (ROR) 2,440.00p +1.96%Synthomer (SYNT) 275.50p +1.89%BH Global Ltd. USD Shares (BHGU) 11.71 +1.74%IP Group (IPO) 177.50p +1.72%Cairn Energy (CNE) 213.70p +1.71%Ophir Energy (OPHR) 285.00p +1.71%FTSE 250 - FallersHomeserve (HSV) 300.40p -5.42%Electrocomponents (ECM) 253.10p -4.60%African Barrick Gold (ABG) 220.70p -4.33%RPS Group (RPS) 327.70p -3.73%Evraz (EVR) 79.90p -3.44%Premier Farnell (PFL) 209.00p -3.29%Interserve (IRV) 586.00p -2.98%Imagination Technologies Group (IMG) 165.30p -2.94%Berkeley Group Holdings (The) (BKG) 2,486.00p -2.40%Ocado Group (OCDO) 511.00p -2.39%NR