Have discovered one other work that might (or might not) shed a bit of light on this obscure matter.,
Coe, Sophie, 1994. _America's First Cuisines_. Austin: University of Texas Press.
This is in the bibliography of
Davidson, Alan, 1999 (2nd edn 2006). _Oxford Companion to Food, The_. Oxford: OUP
and is referred to from the article on 'Maya food', which merely states that 'there is also evidence of trade in conserved fish' and doesn't go into further detail.
RH