The investment banking business has depleted by at least 25,430 job cuts this year, with many more on the horizon, says a recent Financial Times survey. That estimate is probably low, says FT, because many firms have been cutting quietly, rather than announce sweeping layoffs.

FT says that the biggest cuts have come at banks that are dealing with mergers, such as JP Morgan Chase and Credit Suisse First Boston. And there have also been restructuring cuts at Deutsche Bank and ABN Amro. But most of the cuts are related to the market downturn. It reports that merger and acquisition activity remains down substantially, coupled with falloffs in equity volumes, global equity underwriting, bond issuance.

“Equity markets, both primary and secondary, were broadly weaker in July. More disturbingly, fixed income issuance, previously one area of support, also showed substantial declines,” Morgan Stanley said in a recent research note.

FT reports that bankers have been careful not to cut too deeply, too quickly, but they also say they will be forced to get much more aggressive if there is no improvement in business in the autumn.