J.P. Morgan Chase Co. (JPM) may cut pay for some of its investment-bank employees amid relatively slow trading conditions, the firm's chief financial officer said Wednesday.

Speaking at an investor conference in New York, J.P. Morgan CFO Marianne Lake said the bank could cut compensation if it continues to post lower revenue as J.P. Morgan and other banks did during the first quarter.

While she didn't give a time frame, Ms. Lake described the revenue pressures as "cyclical."

The comments from Ms. Lake as well as earlier remarks from Morgan Stanley Chairman and CEO James Gorman indicate that the slow trading conditions could lead to both layoffs and reduced pay for some of Wall Street's highest paid employees if activity doesn't pick up over the next six months.

While compensation dollars may fall later this year when bonus decisions start getting made, J.P. Morgan's compensation as a percent of revenue might actually grow, since revenue may fall faster than compensation does.

Ms. Lake estimated Wednesday that the closely watched pay ratio could rise to around 35% of revenue from the low 30s as revenue shrinks in the investment bank.

J.P. Morgan's investment bank hasn't yet given an overall revenue estimate for the year. It had net revenue of $34 billion in 2013, around a third of J.P. Morgan's overall revenue, according to the company.

The largest U.S. bank by assets, J.P. Morgan determines compensation using a number of factors, including risk-adjusted returns, performance and competition, she added.

While the year isn't yet half over, some are already bracing for a tough compensation year. Morgan Stanley Chairman and CEO James Gorman disclosed new targets Tuesday on expenses for employee pay and noted that the bank has trimmed staff due to slow markets in currencies and interest-rate trading.

Specifically, Mr. Gorman said expenses from pay and benefits at the firm's securities and investment-management divisions should comprise less than 40% of each unit's revenue. The so-called compensation ratio should fall below 55% at Morgan Stanley's wealth-management arm, Mr. Gorman said.

Since the financial crisis, Morgan Stanley's institutional securities business, which includes both investment bankers and traders, has tallied compensation costs anywhere between 42% and 63% of net revenue. The compensation ratio last year stood at 40% within investment management, and 58% at the wealth-management unit.

Separately, J.P. Morgan's Ms. Lake also said longer term there could be "too much capacity" in the fixed-income area, where bonds and other contracts tied to rates and currencies trade. That could lead to cuts in J.P. Morgan's business over time, depending on market conditions. J.P. Morgan's market share in fixed-income, currencies and commodities, or FICC, dropped to 15.4% in the first quarter of this year compared with 18.6% for the full year 2013, according to Ms. Lake's investor presentation.

Bankers and recruiters have been warning of job cuts on trading desks as revenue slides. At Morgan Stanley, the recent job cuts have affected fewer than 100 employees, a person familiar with the matter has said, and some were offered other jobs inside the firm.

For the 10 largest global investment banks, trading revenue for FICC units in the first quarter plunged 15.7% from the same period a year earlier, according to data from research consultant Coalition. The number of FICC traders, researchers and salespeople, meanwhile, fell just 4.8% over that period.

(Justin Baer contributed to this article.)