Foreign investment in freshwater fishing is forbidden (Marine fishing is not restricted). Since the entering into force of Myanmar Companies Law in August 2018, a foreign company is defined as a company in which an overseas person owns or controls, directly or indirectly, an ownership interest of more than 35%.
"List of Restricted Investment Activities
1. In exercise of the powers conferred under section 42 and section 100(b) of Myanmar Investment Law, with the approval of the Union Government, Myanmar Investment Commission issued the list of  restricted investment activities  as follows: [...]
(B) Investment activities that are not allowed to be carried out by foreign investors: [...] 
Freshwater fishing (Fresh water fisheries and relevant services); [...]" (Myanmar Investment Commission, Notification No. 15/2017, 'List of Restricted Investment Activities')
---------------------------------
"42. The following types of investment businesses shall be stipulated as restricted investment: [...]
(b) investment activities that are not allowed to be carried out by Foreign investors; [...]"(Myanmar Investment Law, The Pyidaungsu Hluttaw Law No. 40/2016 of 18 October 2016, Art. 42)
---------------------------------
"Chapter II Types of Investment: Restricted Investment Activities […] 
21. Myanmar citizen investors may carry out investment activity stipulated under subsection (b) of section 42 of the Law. [...]" (Myanmar Investment Rules, Notification No. 35/2017 of 30 March 2017, Art. 21)
---------------------------------
"PART I - COMMENCEMENT AND DEFINITIONS
Division 1 - Name, commencement and definitions 
1. Citation and commencement of this Law and definitions
(a) This Law shall be called the Myanmar Companies Law.
(b) This Law commences on the date of notification determined by the President of the Union.
(c) In this Law, unless the context otherwise implies: [...]
(xiv) “foreign company” means a company incorporated in the Union in which an overseas corporation or other foreign person (or combination of them) owns or controls, directly or indirectly, an ownership interest of more than thirty-five per cent; [...]" (Myanmar Companies Law (PyidaungsuHluttaw Law No.29, 6th December 2017))
Myanmar Investment Commission, Notification No. 15/2017, 'List of Restricted Investment Activities'
Myanmar Investment Law, The Pyidaungsu Hluttaw Law No. 40/2016 of 18 October 2016, Art. 42.
Myanmar Investment Rules, Notification No. 35/2017 of 30 March 2017, Art. 22.
Myanmar Companies Law (PyidaungsuHluttaw Law No.29, 6th December 2017)
[<a href="http://www.dica.gov.mm/sites/dica.gov.mm/files/document-files/20170419_eng_42_update.pdf">Notification</a>],[<a href="http://www.dica.gov.mm/sites/dica.gov.mm/files/document-files/myanmar_investment_law_official_translation_3-1-2017.pdf">Law</a>],[<a href="http://www.dica.gov.mm/sites/dica.gov.mm/files/document-files/mir_english_0.pdf">Rules</a>],[<a href="https://dica.gov.mm/sites/dica.gov.mm/files/document-files/final_mcl_english_version_6_dec_president_signed_version_cl_0.pdf">Law</a>]