file 1: "body_composition_density_dependence.csv"

The data in the different columns represent:
sampling_station	-	id of sampling station
length_mm			-	length of a cockle in mm
afdmflesh_mg		-	ash-free dry mass of cockle flesh in mg
dmshell_mg			-	dried shell mass of cockles in mg
afdmflesh_rel		-	relative ash-free dry mass of cockle flesh
dmshell_rel			-	relative dried shell mass of cockles 
density_nm2			-	cockle density at the sampling station