
575 N.W.2d 823 (1998)
227 Mich. App. 520
JACKSON FIRE FIGHTERS ASSOCIATION, LOCAL 1306, IAFF, AFL-CIO, Plaintiff-Appellee,
v.
CITY OF JACKSON, Defendant-Appellant.
JACKSON FIRE FIGHTERS ASSOCIATION, Local 1306, IAFF, AFL-CIO, Plaintiff-Appellant,
v.
CITY OF JACKSON, Defendant-Appellee.
CITY OF JACKSON, Plaintiff-Appellant,
v.
JACKSON FIRE FIGHTERS ASSOCIATION, LOCAL 1306, IAFF, AFL-CIO, Defendant-Appellee.
Docket Nos. 192470, 193765, 197794, 197795.
Court of Appeals of Michigan.
Submitted November 5, 1997, at Detroit.
Decided January 23, 1998, at 9:20 a.m.
Released for Publication April 13, 1998.
*824 Sachs, Waldman, O'Hare, Helveston, Bogas & McIntosh, P.C. by Ronald R. Helveston, Detroit, for Jackson Fire Fighters Association, Local 1306, IAFF, AFL-CIO.
Keller, Thoma, Schwarze, Schwarze, DuBay & Katz, P.C. by Dennis B. DuBay and Bruce M. Bagdady, Detroit, for City of Jackson.
Before GRIFFIN, P.J., and SAWYER and O'CONNELL, JJ.


*825 ON REMAND
PER CURIAM.
These appeals are before this Court pursuant to our Supreme Court's order vacating our orders in Docket Nos. 187236 and 187801 (currently Docket Nos. 197795 and 197794, respectively), remanding those cases for consideration as on leave granted, ordering them consolidated with Docket Nos. 192470 and 193765, and directing the parties "to brief and argue the effect of conflicting orders from [the Michigan Employment Relations Commission (MERC) ] and the Act 312 arbitration panel." City of Jackson v. Jackson Fire Fighters Ass'n, Local 1306, 453 Mich. 872, 554 N.W.2d 1 (1996). For reasons that will be stated, we hold that despite an arbitration panel's prior contrary ruling, the MERC properly decided that § 8.1 of the parties' July 1, 1988, to June 30, 1991, collective bargaining agreement did not constitute a mandatory bargaining subject. We therefore affirm the MERC's March 20, 1996, decision and order, vacate the arbitration panel's December 6, 1994, award, and vacate the Jackson Circuit Court's June 12, 1995, order affirming the arbitration award and its February 2, 1996, injunction requiring the City of Jackson to comply with that award.

I
Strikes by public employees are forbidden by § 2 of the public employment relations act (PERA), M.C.L. § 423.202; M.S.A. § 17.455(2). Section 15 of the PERA, M.C.L. § 423.215; M.S.A. § 17.455(15), requires a public employer to bargain collectively with the representatives of its employees "with respect to wages, hours, and other terms and conditions of employment...." Issues falling into those categories are deemed to be mandatory subjects of bargaining, while all other matters are considered to be permissive bargaining subjects. Metropolitan Council No. 23 and Local 1277, (AFSCME) AFL-CIO v. Center Line, 414 Mich. 642, 652, 327 N.W.2d 822 (1982). Because "[c]ompulsory arbitration in police and fire disputes was seen as a necessary tradeoff for the prohibition against striking," the Legislature enacted the compulsory arbitration statute, 1969 P.A. 312, M.C.L. § 423.231 et seq.; M.S.A. § 17.455(31) et seq. Local 1277, supra at 650-651, 327 N.W.2d 822. Act 312 "is separate and distinct from PERA, dealing with the particular problems of labor disputes with policemen and firemen." Metropolitan Council No. 23 and Local 1277, (AFSCME) AFL-CIO v. Center Line, 78 Mich.App. 281, 284, 259 N.W.2d 460 (1977). "Given the fact that Act 312 complements PERA and that under § 15 of PERA the duty to bargain only extends to mandatory subjects," it follows that an Act 312 arbitration panel "can only compel agreement as to mandatory subjects." Local 1277, supra at 414 Mich. at 654, 327 N.W.2d 822. When the question whether a matter is mandatorily bargainable arises in an Act 312 arbitration proceeding, the MERC, noting the availability of ultimate judicial review, has recognized that, in the absence of or concurrent with MERC rulings, the arbitration panel has jurisdiction to resolve that question before or as part of the panel's consideration of disputed contract issues. Detroit v. Detroit Fire Fighters Ass'n, Local 344, IAFF, 1990 MERC Lab. Op. 859, 862; Detroit v. Detroit Fire Fighters Ass'n, Local 344, IAFF, 1990 MERC Lab. Op. 561, 565.
Applying these principles to the present facts, we note that the crux of these appeals is art. 8, § 8.1 of the July 1, 1988, to June 30, 1991, collective bargaining agreement between the city and the Jackson Fire Fighters Association, Local 1306, IAFF, AFL-CIO (the union), which states, in pertinent part, "The City shall at all times maintain a minimum complement of fifteen (15) 24-hour fire fighters on duty on each shift." The union demanded the retention of § 8.1 in the parties' proposed 1991-94 labor contract, contending that it was a mandatory subject of collective bargaining. The city, wishing to reduce per-shift staffing, objected, maintaining that § 8.1 was a permissive bargaining subject. When the parties reached an impasse, the issue was submitted to arbitration pursuant to Act 312. The arbitration panel ruled that § 8.1 constituted a mandatory subject of bargaining within the panel's jurisdiction, concluded that the city's proposed reduction in per-shift manning would adversely affect fire fighter safety, and ordered that § 8.1 be retained unchanged in any 1991-94 agreement.
*826 Pursuant to the city's petition for review and the union's complaints, the Jackson Circuit Court affirmed the arbitration panel's award and entered a permanent injunction ordering the city to comply with § 8.1. This Court denied the city's applications for leave to appeal these rulings, Docket Nos. 187236 and 187801.
Meanwhile, the city filed an unfair labor practice charge with the MERC, accusing the union of unlawfully demanding that the city bargain with respect to § 8.1. The hearing referee rejected the union's argument that because the Act 312 arbitration panel had already held § 8.1 to be mandatorily bargainable, the MERC was preempted from addressing that issue. The referee stated, "It is clear ... that the [MERC] is not bound by the panel's decision regarding whether the daily staffing provision is a mandatory subject of bargaining; just the reverse is true: the arbitration panel is bound by the [MERC's] determinations." The referee also found "the daily minimum manning provision to be a permissive subject of bargaining only," and ruled that the union had violated its bargaining duty under the PERA by "submitting this proposal to an Act 312 arbitration."
On March 20, 1996, the MERC issued a unanimous decision and order affirming the decision of the hearing referee, holding that the arbitration panel did not have concurrent jurisdiction with the MERC to decide the § 8.1 issue, that "collateral estoppel is not appropriate where, as here, primary jurisdiction has been given by the [L]egislature to an administrative agency," that any conflict between the panel's and the MERC's rulings could be resolved by judicial review, and that the evidence failed to establish that § 8.1 adversely affected fire fighter safety. We agree.
The MERCand not an Act 312 arbitration panelhas authority to implement the PERA, AFSCME, Council 25 v. Wayne Co., 152 Mich.App. 87, 99, 393 N.W.2d 889 (1986), and possesses exclusive jurisdiction over unfair labor practice charges, Lamphere Schools v. Lamphere Federation of Teachers, 400 Mich. 104, 118, 252 N.W.2d 818 (1977); Rockwell v. Board of Education of School Dist. of Crestwood, 393 Mich. 616, 630, 227 N.W.2d 736 (1975). Furthermore, Act 312 was intended to supplement the PERA, not control it. M.C.L. § 423.244; M.S.A. § 17.455(44); Local 1277, supra at 414 Mich. at 652, 327 N.W.2d 822. The panel itself recognized this when it noted that "we are not free agents," but "[function] under MERC's auspices," and its chairman indicated his agreement with "the basic and incontrovertible premise that an Act 312 panel functions under MERC's auspices and is obliged to follow applicable MERC decisions." Therefore, the union's argument that the doctrine of collateral estoppel precludes the MERC from adjudicating § 8.1 is inappropriate because the Legislature has vested primary jurisdiction in the MERC. The fact that under the unusual circumstances of this case the MERC's ruling followed and conflicted with the panel's does not warrant the conclusion that the MERC was thereby estopped from proceeding as it did.

II
The union also contends that the MERC's decision is not supported by the evidence. M.C.L. § 423.216(e); M.S.A. § 17.455(16)(e) provides that the "findings of the [MERC] with respect to questions of fact if supported by competent, material, and substantial evidence on the record considered as a whole shall be conclusive." See also Const. 1963, art. 6, § 28. In Detroit Police Officers Ass'n v. Detroit, 212 Mich.App. 383, 388, 538 N.W.2d 37 (1995), this Court stated, "Substantial evidence is more than a scintilla but substantially less than a preponderance of the evidence."
It is important to note that § 8.1 governs the number of fire fighters on duty per shift, not the number actually assembled at a fire scene. The number at the scene determines what action may safely be undertaken to combat a blaze and may include not only on-duty personnel but also off-duty fire fighters called in, volunteers, and those responding pursuant to mutual assistance pacts with other fire departments. Consequently, the evidence in this case fails to demonstrate a causal nexus between the city's proposed reduction in daily staffing and fire fighter safety, and the union's contention that reducing the number of fire fighters on duty would adversely affect safety is without merit.
*827 Even if a reduction in the daily staff would delay response to a fire, that affects the level of fire protection offered the citizens of Jackson and does not raise a safety issue with respect to fire fighters. Sufficient evidence therefore exists to support the MERC's decision and order.[1]
We affirm the MERC's March 20, 1996, decision and order, vacate the arbitration panel's December 6, 1994, award, and vacate the Jackson Circuit Court's June 12, 1995, order affirming the arbitration award and its February 2, 1996, injunction requiring the city to comply with that award. No costs, a public question being involved.
NOTES
[1]  We need not discuss the distinction, if any, between issues "related to" safety and those "inextricably intertwined" with it, Detroit v. Detroit Fire Fighters Ass'n, Local 344, IAFF, 204 Mich. App. 541, 553, 517 N.W.2d 240 (1994), because sufficient evidence exists to affirm the MERC's decision and order under either statement of the criterion.
