Macquarie Fortress Investments, an ASX-listed investor in senior debt securities of US companies said the value of its loan portfolio fell by four per cent during July from June.While Fortress invests in senior debt only, the rise in credit spreads has reduced the value of the loans in the portfolio (the size of which Fortress did not disclose in a release to the ASX).Fortress said while there were no defaults in the portfolio the average price of the senior loans was now around 96 cents in the dollar, down from 100 cents at the end of June.The fund manager said it may sell some loans but was also looking to buy further loans in the secondary market if prices weaken further.Fortress said it expected to meet its "distribution objective" of a coupon of bills plus 4.5 per cent for the quarter ending August 2007.