<PAGE>   1
                                                                   EXHIBIT 25.1


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM T-1

                            STATEMENT OF ELIGIBILITY
                      UNDER THE TRUST INDENTURE ACT OF 1939
                  OF A CORPORATION DESIGNATED TO ACT AS TRUSTEE

                CHECK IF AN APPLICATION TO DETERMINE ELIGIBILITY
                 OF A TRUSTEE PURSUANT TO SECTION 305(b)(2)___

                               ------------------


                           BANK ONE TRUST COMPANY, NA
               (EXACT NAME OF TRUSTEE AS SPECIFIED IN ITS CHARTER)

    A NATIONAL BANKING ASSOCIATION                     31-0838515
                                                       (I.R.S. EMPLOYER
                                                       IDENTIFICATION NUMBER)

 100 EAST BROAD STREET, COLUMBUS, OHIO                 43271-0181
(ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)               (ZIP CODE)

                           BANK ONE TRUST COMPANY, NA
                              100 EAST BROAD STREET
                            COLUMBUS, OHIO 43271-0181
       ATTN: LINDA J. PATTERSON, SENIOR MANAGING DIRECTOR, (614) 248-5193
            (NAME, ADDRESS AND TELEPHONE NUMBER OF AGENT FOR SERVICE)


                               ------------------


                               SEMCO ENERGY, INC.
               (EXACT NAME OF OBLIGOR AS SPECIFIED IN ITS CHARTER)


             MICHIGAN                                  38-2144267
   (STATE OR OTHER JURISDICTION OF                     (I.R.S. EMPLOYER
    INCORPORATION OR ORGANIZATION)                     IDENTIFICATION NUMBER)


         405 WATER STREET
         PORT HURON, MICHIGAN                          48060
(ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)               (ZIP CODE)

                                 DEBT SECURITIES
                         (TITLE OF INDENTURE SECURITIES)


<PAGE>   2
ITEM 1.  GENERAL INFORMATION.  FURNISH THE FOLLOWING
         INFORMATION AS TO THE TRUSTEE:

         (A)      NAME AND ADDRESS OF EACH EXAMINING OR
         SUPERVISING AUTHORITY TO WHICH IT IS SUBJECT.

         Comptroller of Currency, Washington, D.C.;
         Federal Deposit Insurance Corporation,
         Washington, D.C.; The Board of Governors of
         the Federal Reserve System, Washington D.C.

         (B)      WHETHER IT IS AUTHORIZED TO EXERCISE
         CORPORATE TRUST POWERS.

         The trustee is authorized to exercise corporate trust powers.

ITEM 2.  AFFILIATIONS WITH THE OBLIGOR.  IF THE OBLIGOR
         IS AN AFFILIATE OF THE TRUSTEE, DESCRIBE EACH
         SUCH AFFILIATION.

         No such affiliation exists with the trustee.


ITEM 16. LIST OF EXHIBITS. LIST BELOW ALL EXHIBITS FILED AS A PART
         OF THIS STATEMENT OF ELIGIBILITY.

         1.  A copy of the articles of association of the
             trustee now in effect.*

         2.  A copy of the certificates of authority of the trustee to
             commence business.*

         3.  A copy of the authorization of the trustee to exercise
             corporate trust powers.*

         4.  A copy of the existing by-laws of the trustee.*

         5.  Not Applicable.

         6.  The consent of the trustee required by Section 321(b) of
             the Act.


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         7.  A copy of the latest report of condition of the trustee
             published pursuant to law or the requirements of its
             supervising or examining authority.

         8.  Not Applicable.

         9.  Not Applicable.


     Pursuant to the requirements of the Trust Indenture Act of 1939, as
     amended, the trustee, Bank One Trust Company, NA, a national banking
     association organized and existing under the laws of the United States of
     America, has duly caused this Statement of Eligibility to be signed on its
     behalf by the undersigned, thereunto duly authorized, all in the City of
     Chicago and State of Illinois on the 24th day of November, 1999.


             BANK ONE TRUST COMPANY, NA
             TRUSTEE

             By   /s/ John R. Prendiville
                -----------------------------
                  John R. Prendiville
                  Vice President


*EXHIBITS 1, 2, 3 AND 4 ARE HEREIN INCORPORATED BY REFERENCE TO EXHIBITS BEARING
IDENTICAL NUMBERS IN ITEM 16 OF THE FORM T-1 OF BANK ONE TRUST COMPANY, NA FILED
AS EXHIBIT 25.1 TO THE REGISTRATION STATEMENT ON FORM S-3 OF THE DOW CHEMICAL
COMPANY, FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON OCTOBER 8, 1999.




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<PAGE>   4
                                    EXHIBIT 6



                       THE CONSENT OF THE TRUSTEE REQUIRED
                          BY SECTION 321(b) OF THE ACT


                                               November 24, 1999



Securities and Exchange Commission
Washington, D.C.  20549

Gentlemen:

In connection with the qualification of an indenture between SEMCO ENERGY, INC.
and BANK ONE TRUST COMPANY, NA, as Trustee, the undersigned, in accordance with
Section 321(b) of the Trust Indenture Act of 1939, as amended, hereby consents
that the reports of examinations of the undersigned, made by Federal or State
authorities authorized to make such examinations, may be furnished by such
authorities to the Securities and Exchange Commission upon its request therefor.


                   Very truly yours,

                   BANK ONE TRUST COMPANY, NA



                   By   /s/ John R. Prendiville
                      --------------------------------
                        John R. Prendiville
                        Vice President


<PAGE>   5
                                    EXHIBIT 7

Legal Title of Bank:     Bank One Trust Company, NA    Call Date:  12/31/98
Address:                 100 Broad Street              ST-BK:  17-1630 FFIEC 032
City, State  Zip:        Columbus, OH 43271            Page RC-1
FDIC Certificate No.:    0/3/6/1/8

CONSOLIDATED REPORT OF CONDITION FOR INSURED COMMERCIAL
AND STATE-CHARTERED SAVINGS BANKS FOR DECEMBER 31, 1998

All schedules are to be reported in thousands of dollars. Unless otherwise
indicated, report the amount outstanding of the last business day of the
quarter.

SCHEDULE RC--BALANCE SHEET

<TABLE>
<CAPTION>

                                                                                                   DOLLAR AMOUNTS IN THOUSANDS C300
                                                                                                     RCON        BIL MIL THOU

ASSETS
<S>                                                                                                 <C>       <C>            <C>
1.  Cash and balances due from depository institutions (from Schedule
    RC-A):                                                                                           RCON
    a. Noninterest-bearing balances and currency and coin(1) ..................                      0081           159,911     1.a
    b. Interest-bearing balances(2)............................................                      0071            16,874     1.b
2.  Securities
    a. Held-to-maturity securities (from Schedule RC-B, column A) .............                      1754                 0     2.a
    b. Available-for-sale securities (from Schedule RC-B, column D)............                      1773             7,403     2.b
3.  Federal funds sold and securities purchased under agreements to
    resell ....................................................................                      1350           576,473     3.
4.  Loans and lease financing receivables:
    a. Loans and leases, net of unearned income (from Schedule                                       RCON
    RC-C)......................................................................                      2122            32,603     4.a
    b. LESS: Allowance for loan and lease losses...............................                      3123                10     4.b
    c. LESS: Allocated transfer risk reserve...................................                      3128                 0     4.c
    d. Loans and leases, net of unearned income, allowance, and                                      RCON
         reserve (item 4.a minus 4.b and 4.c)..................................                      2125            32,593     4.d
5.  Trading assets (from Schedule RD-D)........................................                      3545                 0     5.
6.  Premises and fixed assets (including capitalized leases)                                         2145            18,685     6.
7.  Other real estate owned (from Schedule RC-M)                                                     2150                 0     7.
8.  Investments in unconsolidated subsidiaries and associated
    companies (from Schedule RC-M).............................................                      2130                 0     8.
9.  Customers' liability to this bank on acceptances outstanding                                     2155                 0     9.
10. Intangible assets (from Schedule RC-M).....................................                      2143            31,392     10.
11. Other assets (from Schedule RC-F)..........................................                      2160           127,322     11.
12. Total assets (sum of items 1 through 11)...................................                      2170           970,653     12.

</TABLE>

-------------
(1)  Includes cash items in process of collection and unposted debits.
(2)  Includes time certificates of deposit not held for trading.

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<PAGE>   6
Legal Title of Bank:     Bank One Trust Company, N.A.    Call Date:  12/31/98
Address:                 100 East Broad Street           ST-BK: 171630 FFIEC 032
City, State  Zip:        Columbus, OH 43271              Page RC-2
FDIC Certificate No.:    0/3/6/1/8

SCHEDULE RC-CONTINUED
<TABLE>
<CAPTION>
                                                                                                  DOLLAR AMOUNTS IN
                                                                                                      THOUSANDS
                                                                                                      ---------
LIABILITIES
<S>                                                                                     <C>           <C>            <C>
13. Deposits:
    a. In domestic offices (sum of totals of columns A and C                                  RCON
       from Schedule RC-E, part 1)..........................................                  2200      802,791          13.a
       (1) Noninterest-bearing(1)...........................................                  6631      727,720          13.a1
       (2) Interest-bearing.................................................                  6636       75,071          13.a2

    b. In foreign offices, Edge and Agreement subsidiaries, and
       IBFs (from Schedule RC-E, part II)...
       (1) Noninterest bearing..............................................
       (2) Interest-bearing.................................................
14. Federal funds purchased and securities sold under agreements
    to repurchase: .........................................................             RCFD 2800            0           14
15. a. Demand notes issued to the U.S. Treasury ............................             RCON 2840            0           15.a
    b. Trading Liabilities (from Sechedule RC-D)............................             RCFD 3548            0           15.b

16. Other borrowed money:                                                                     RCON
                                                                                              ----
    a. With original maturity of one year or less...........................                  2332            0           16.a
    b. With original  maturity of more than one year........................                  A547            0           16.b
    c. With original maturity of more than three years .....................                  A548            0           16.c
17. Not applicable
18. Bank's liability on acceptance executed and outstanding.................                  2920            0           18.
19. Subordinated notes and debentures.......................................                  3200            0           19.
20. Other liabilities (from Schedule RC-G)..................................                  2930       64,642           20.
21. Total liabilities (sum of items 13 through 20)..........................                  2948      867,433           21.
22. Not applicable
EQUITY CAPITAL
23. Perpetual preferred stock and related surplus...........................                  3838            0           23.
24. Common stock............................................................                  3230          800           24.
25. Surplus (exclude all surplus related to preferred stock)................                  3839       35,157           25.
26. a. Undivided profits and capital reserves...............................                  3632       67,207           26.a
    b. Net unrealized holding gains (losses) on available-for-sale
       securities...........................................................                  8434           56           26.b
27. Cumulative foreign currency translation adjustments ....................                  3284            0           27.
28. Total equity capital (sum of items 23 through 27) ......................                  3210      103,220           28.
29. Total liabilities, limited-life preferred stock, and equity
    capital (sum of items 21, 22, and 28)...................................                  3300      970,653           29.

</TABLE>

<TABLE>
Memorandum
<S><C>
To be reported only with the March Report of Condition.

1.  Indicate in the box at the right the number of the statement below that best
    describes the most comprehensive level of auditing work performed for the                                   Number
    bank by independent external auditors as of any date during 1996 ..........................RCFD 6724...N/A. M.1.
1 = Independent audit of the bank conducted in accordance         4. =   Directors' examination of the bank
     with generally accepted auditing standards by a certified           performed by other external auditors (may be
     public accounting firm which submits a report on the bank           required by state chartering authority)
2 = Independent audit of the bank's parent holding company        5  =   Review of the bank's financial statements by external
     conducted in accordance with generally accepted auditing            auditors
     standards by a certified public accounting firm which        6 =    Compilation of the bank's financial statements by external
     submits a report on the consolidated holding company                auditors
     (but not on the bank separately)                             7 =    Other audit procedures (excluding tax preparation work)
3 = Directors' examination of the bank conducted in               8 =    No external audit work
     accordance with generally accepted auditing standards by
     a certified public accounting firm (may be required
     by state chartering authority)
</TABLE>

----------------
(1) Includes total demand deposits and noninterest-bearing time and savings
    deposits.


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