* Topix trading volume lowest since mid-January * U.S. jobs report, BOJ meeting in focus * Astellas Pharma up after U.S. panel backs drug * Shimamura higher after earnings, target price hike By Mari Saito TOKYO, April 6 (Reuters) - Japan's Nikkei average fell in thin volume on Friday ahead of a key U.S. jobs report and marked its worst weekly performance in eight months on fading hopes of further U.S. stimulus and fresh concerns over the euro zone. "The very optimistic view of the U.S. economy has already been priced in. We can't expect further monetary easing from the Fed," said Ryota Sakagami, chief equity research strategist at SMBC Nikko Securities. "On the other hand, we see uncertainty in the European debt crisis and the general elections in Greece and the presidential election in France will only create further uncertainty." The benchmark Nikkei dropped 0.8 percent to 9,688.45, falling for a fourth consecutive session. The index was off 3.9 percent on the week, its worst weekly performance since the week of Aug. 1-5 when it shed 5.4 percent. Despite this week's sharp losses, the Nikkei is still up 14.6 percent this year, buoyed by a run of strong U.S. economic data and liquidity boosting programmes by central banks. Strategists expected the market correction to last until late April or mid-May, when Japanese companies will announce earnings guidance for the current fiscal year, though they said the Nikkei should hold above 9,000. "The earnings growth scenario for Japanese companies remains intact so this is just a speed adjustment after the big gains we've seen recently," said Shun Maruyama, chief Japan equity strategist at BNP Paribas. Data from Thomson Reuters I/B/E/S pointed to an improved earnings outlook for the Topix, with its earnings momentum - analysts' upgrades minus downgrades as a total percentage - rising to 3.5 percent in March from minus 6.6 percent in February. Maruyama said investors should pick up blue chips during the correction that are expected to make a robust earnings recovery like semiconductor makers, autos and machinery. He also said domestic and foreign long-only funds were picking up defensive shares at the dip. Among heavily traded stocks, Toyota Motor Corp sagged 2 percent on Friday, falling for a seventh session as investors continued to lock in sharp gains made since January.