Profits in the nation's ailing securities industry were an anemic $200 million in the first six months of 1990 and have deteriorated since then, Wall Street's leading trade group said.

The Securities Industry Association said Wall Street is starting to slash expenses beyond the nearly 50,000 job cuts since the 1987 stock market crash. The outlook remains gloomy.Trading and underwriting of stocks and bonds has been depressed by drastically fewer mergers, concern over the economy, the year-old collapse of the junk bond market and reduced activity by individual investors.

The SIA report said first-half 1990 profits "barely reached $200 million, a sum not equivalent to a single decent bond issue a few years ago, and indications are third-quarter results will deteriorate further."

The industry made $1.8 billion last year, $2.5 billion in 1988, $1.1 billion in 1987 and a record of more than $5 billion in 1986. Annual profits haven't been below $1 billion since the 1970s.

The SIA said industry revenue will not increase this year for the first time since the 1970s. It said profit margins are below 1 percent, return on equity is under 2 percent and brokerage commissions are off 11 percent with no prospect for improvement by the end of the year.

George R. Monahan, the group's director of industry studies, said with the exception of the top 10 firms, the industry "has been doing an excellent job of cost reduction."

Broker compensation is off about 6 percent from 1989, while commission revenue is down about 7 percent. But at the 10 largest firms, broker compensation is down 8 percent while commission revenue has slumped 16 percent.

Wall Street is notorious for its high compensation levels, particularly during boom cycles such as the mid-1980s when young investment bankers and other professionals quickly commanded six-figure salaries. Stockbrokers, on the other hand, tend to receive less pay.

The SIA said that when expenses are adjusted to exclude gross interest expenses, compensation in the first six months of 1990 accounted for 57 percent of total costs. Overall, pay was down to a third of all expenses from 41 percent in 1987, the group said.

Further compensation cuts are occurring. Year-end bonuses this year for highly paid investment bankers - an important indicator of compensation trends - are expected to be slashed 30 percent to 50 percent at top firms.

That would bring compensation for investment bankers down to 1985 levels, Wall Street executives say, still considered high. Many firms in recent weeks have laid off investment bankers, including senior-level professionals, because of declining business.

Despite several rounds of cutting since the 1987 crash, Wall Street pay last year still averaged more than $82,700 per employee, including clerks and secretaries, the SIA reported, almost double the level a decade ago.

Nearly 50,000 jobs have been eliminated from the securities industry's peak employment of more than 260,000 nationwide in 1987.

Apart from compensation, other cost-cutting appears to be more successful, the SIA said, as expenses in all other areas are below 1989 levels. But Monahan said even that may not be enough.

"Although longstanding practices are now being changed, some firms still make payments to both profitable and unprofitable departments on the premise that business cycles will even this out in the end, which may not happen," he said.

Separately, the SIA announced that Thomas A. James, president and chief executive of Raymond James & Associates Inc., a St. Petersburg, Fla., brokerage, was nominated as chairman-elect. He is to serve as an SIA officer and director in 1991 and become chairman in 1992.

The SIA represents about 600 brokerage and investment banking firms in the United States and Canada that account for about 90 percent of securities activity in North America.