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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-01-24</periodOfReport>

    <issuer>
        <issuerCik>0000768408</issuerCik>
        <issuerName>CYANOTECH CORP</issuerName>
        <issuerTradingSymbol>CYAN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001715607</rptOwnerCik>
            <rptOwnerName>Morton Mawae</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>73-4460 QUEEN KAAHUMANU HWY #102</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>KAILUA-KONA</rptOwnerCity>
            <rptOwnerState>HI</rptOwnerState>
            <rptOwnerZipCode>96740</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <officerTitle>CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Cyanotech common stock options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.83</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-01-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>45000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2028-01-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Cyanotech common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>45000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeHolding>
            <securityTitle>
                <value>Cyanotech common stock options</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.3500</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-07-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Cyanotech common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>75000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>75000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The stock options shall vest as to 15,000 shares on January 24, 2019, 15,000 shares on January 24, 2020 and 15,000 shares on January 24, 2021, in each case subject to continued service with Cyanotech on the vesting date.</footnote>
        <footnote id="F2">The stock options shall vest as to 25,000 shares on July 14, 2018, 25,000 shares on July 14, 2019 and 25,000 shares on July 14, 2020, in each case subject to continued service with Cyanotech on the vesting date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Dan Sprague, by Power of Attorney</signatureName>
        <signatureDate>2018-01-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
