Manu rere could alternatively be imagined as responsible for the bottom end of the 'sun fish':

 

 

 

However, there is a sequence of glyphs in Large St Petersburg Tablet (P) from which we can read an affinity between 'sun fish' and vaha mea:

 

Pa8-31	Pa8-32	Pa8-33	Pa8-34	Pa8-35
		-
Ba10-1	Ba10-2		Ba10-3	B10-4	Ba10-5	Ba10-6

The parallel glyphs in Aruku Kurenga (B) confirms that the 'sun fish' glyph type probably indeed is hetuu + vaha mea.