Commercial Fixed Wing
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (mon) 6
Distraction; Fatigue; Situational Awareness; Workload
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance
Environment - Non Weather Related; Human Factors; Procedure; Staffing
Aircraft Y departed ZZZ1 airport IFR to the southeast out of the airspace; and Aircraft X was inbound landing ZZZ.  Aircraft X was cleared to the IAF for Runway X at ZZZ and descended to 060.  Aircraft Y was cleared to destination and climbed to 070.  2 additional aircraft departed ZZZ1 after Aircraft Y; and required more direct handling than Aircraft Y.  Aircraft X mentioned that they were picking up traffic to their Northwest; and by the time I looked; Aircraft Y was leaving 061; and Aircraft X was at 072.  They were separated by 2.62 miles and 900 feet vertically.  During with dealing with the other departure's climbing out behind Aircraft Y; I lost the Aircraft Y's rate of climb reference the descending jet traffic.  I immediately stopped Aircraft X 's descent; and stopped Aircraft Y's climb and descended Aircraft Y.  Due to COVID protocol; this occurred while staffed with 4 CPCs and 1 Supervisor to work the facility until XA:00 local time.Better staffing to alleviate Controller fatigue.  Our staffing has been tight; and time on position has been increased at the facility for a while; resulting in long work sessions and short breaks sometimes to produce coverage to work the traffic; which has resumed close to 90% of Pre-COVID numbers.
TRACON Controller reported a loss of separation between an air carrier and a small aircraft and cited staffing issues as a contributing factor.