perforated/drilled medium: Changar significa romper, destrozar, quizás se refiere al suelo perforado.
Otra posiblidad: half perforated/drilled

"Noncompliance can be attributed to a multiplicity of
factors, and avoiders of external regulatory enforcement cannot be
considered a homogeneous group of people. To facilitate the
analysis, Puerto Magdalena and Paraje de Uni¢n fishermen have been
classified into five noncompliance categories: Mapacheros engaged
in the infringement of areal and seasonal closures, Pescadores
libres engaged in entry violations, changueros who use illegal
gear, guaterismo or black market activity, and disidencia or open
defiance of new regulations and increased enforcement. These
categories are not exclusive of one another, a fisherman may
belong to several at one time, or switch from one to the other at
different points in time."

A "changuero" is definitely a "monkey board". The "half-sized (half)" is merely a guess. Hopefully some will shed some light on that in the future.