Methuen (Mass.) Contributory Retirement System is searching for an active domestic core fixed-income manager to run $21 million for the $60 million plan, said Kevin Leonard, the Segal Advisors consultant who is assisting. The search was prompted by concerns over the performance of the incumbent manager, which he declined to identify. The existing manager will be allowed to rebid. RFPs are available from Segal; the deadline is April 8.