In principle, only nationals of the Netherlands may be appointed as captain of a Dutch flagged fishing vessel. Exemptions may be granted to EU/EEA nationals.
"Article 29
1 On Dutch ships, only Dutchmen are appointed as captains.
2 Exemption from the requirement referred to in the first paragraph may be granted for fishing vessels by ministerial regulation, subject to conditions or restrictions.
[...]
Article 30
1 Our Minister may, at the request of a ship manager, grant an exemption from the obligation referred to in Article 29 for his ship or for his ships, for a period not exceeding two years. Conditions and restrictions can be attached to an exemption.
2 The ship manager demonstrates with the application:
a.that his ship cannot be manned with a Dutch captain, or that his ships cannot be manned with a sufficient number of Dutch captains, and
b.that if this situation continues, his shipping company will be in serious trouble.
3 An exemption as referred to in the first paragraph is only granted if the master for whom the exemption has been applied for is a national of one of the member states of the European Union or of one of the other states that are parties to the Agreement on the European Economic Area, and if there are no objections to the master in connection with the security of the state. [...]" (Seafarers Act of 11 December 1997; consolidated version in force on 01-02-2002; Articles 29 and 30 [google translation])
Seafarers Act of 11 December 1997; last amended 01-07-2021; Articles 29 and 30
[<a href="https://wetten.overheid.nl/BWBR0009124/2002-02-01">Act</a>]