<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2006-03-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>1</form3HoldingsReported>

    <form4TransactionsReported>1</form4TransactionsReported>

    <issuer>
        <issuerCik>0001198144</issuerCik>
        <issuerName>MERCANTILE ALTERNATIVE STRATEGIES FUND LLC</issuerName>
        <issuerTradingSymbol>N/A</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000064908</rptOwnerCik>
            <rptOwnerName>MERCANTILE BANKSHARES CORP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2 HOPKINS PLAZA</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BALTIMORE</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>21201</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Limited Liability Company Interest</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionCoding>
                <transactionFormType>3</transactionFormType>
                <footnoteId id="F2"/>
            </transactionCoding>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Limited Liability Company Interest</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2004-03-31</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1250000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1250000</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Limited Liability Company Interest</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2004-12-31</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1300000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1300000</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Limited Liability Company Interest</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-06-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4400000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>4400000</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Limited Liability Company Interest</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-12-31</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F4"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1250000</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1250000</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F8"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Mercantile Alternative Strategies Fund LLC (the ?Company?) is a limited liability company organized under the laws of the State of Delaware and registered under the Investment Company Act of 1940, as amended, as a closed-end, non-diversified management investment company.  Each Interest is a percentage of ownership interest in the Company.  The value of each Interest is the corresponding percentage of the net asset value of the Company (as more fully set forth in the Company documents available with the Securities and Exchange Commission (?SEC?)).  The percentage interest in the Company held by Mercantile Bankshares Corporation (?MBC?) at a given time is related to the investments made by other investors have placed into the Company and is subject to change when they buy or sell Interest.</footnote>
        <footnote id="F2">Filer?s Interest has been held directly by MBC since December 30, 2002, which was the effective date of the registration statement filed by the Company with the SEC on December 30, 2002.  Filer?s Interest was in exchange for the seed capital that MBC placed into the Company</footnote>
        <footnote id="F3">The Interest held by MBC represented 100% of the Interests outstanding at the conclusion of the transaction.  This transaction is the last transaction for the fiscal year.</footnote>
        <footnote id="F4">The transaction was a tender offer.</footnote>
        <footnote id="F5">The Interest held by MBC represented 54% of the Interests outstanding at the conclusion of the transaction.  This transaction is the last transaction for the fiscal year.</footnote>
        <footnote id="F6">The Interest held by MBC represented 53% of the Interests outstanding at the conclusion of the transaction.  This transaction is the last transaction for the fiscal year.</footnote>
        <footnote id="F7">The Interest held by MBC represented 46% of the Interests outstanding at the conclusion of the transaction.  The percentage interest for the fiscal year in which this transaction took place is listed by the last transaction that took place for the fiscal year.</footnote>
        <footnote id="F8">The Interest held by MBC represented 45% of the Interests outstanding at the conclusion of the transaction.  This transaction is the last transaction for the fiscal year.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Mercantile Bankshares Corporation By:  /s/ John L. Unger, Secretary</signatureName>
        <signatureDate>2006-08-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
