151/37000 = only 0.4% of flights have an ASR-F. Wow. That's an impressive number!
If this were a truly safe operation with a genuine concern for safety, then the rostering practices would reflect a desire to minimise fatigue and there would be "Zero" reports.
Also, just because only 151 reports were filed does not mean that only 151 pilots felt fatigued. The true number will never be known because many pilots will feel too intimidated to file reports, and a substantially higher number won't file reports because they realise it is a pointless exercise because nobody in management is ever going to do anything about the situation until there is a hull loss.