Perpetual's trust and fund services' business continued its gradual decline in the six months to December, as it reflected ongoing weakness in the securitisation market.Perpetual is Australia's leading securitisation trustee. Its trust and fund services' income fell from A$27.9 million, in the six months to December 2009, to A$26.9 million in the latest half.According to the latest Australian Bureau of Statistics' data, the value of securitisedassets in the Australian market has fallen from a peak of A$274 billion, in June 2007, to the current level of A$138 billion.The value of Perpetual's securitised assets under administration fell from A$222.4 billion to A$209.4 billion over the past 12 month (the ABS' figures do not include balance-sheet assets securitised for Reserve Bank repurchase arrangements).The push by Perpetual's corporate trust division into mortgage servicing has helped fill the gap. Mortgage servicing income rose from A$13.7 million in the six months toDecember 2009 to $25.4 million in the latest half.Perpetual said, in a statement yesterday, that it acquired a major bank client - which is ANZ -  in the 2009/10 financial year, and revenue was starting to flow from that business.Perpetual tracks the progress of its mortgage servicing business by measuring mortgage services' contracts. These rose from 81,000 in the six months to December 2009 to 131,000 in the latest half.Mortgage servicing is a low margin business, however, so the impact of this growth on the bottom line was muted. The division's profit before tax rose from A$17.8 million to A$18.9 million period-on-period.