Universal City-based MCA reported a 12.6% decline in first-quarter net income despite record revenue. The firm's filmed entertainment division posted increased revenue from its television, home video, pay television, studio tour and amphitheater markets, Chairman Lew R. Wasserman said. However, those gains were offset by decreased merchandising revenue. MCA's retail and mail-order businesses reported lower revenue and substantially increased operating losses for this quarter, compared to 1984, while recreation services showed increased operating losses. Wasserman said the firm earned lower investment income this year than last because of a lower average level of investments.