Variable energy storage and growth in the sea star Pisaster ochraceus

The complete data set describes environmentally based variation in
size-specific energy storage (dry mass pyloric caeca/dry body mass) and
growth of live mass of the intertidal sea star Pisaster ochraceus in
British Columbia, Canada. Variation in energy storage and live
mass correspond to (1) naturally occurring
or (2) experimentally induced changes in the zonation of their
prey, the sea mussel Mytilus californianus and associated
species. The relevant features of mussel zonation are
the depth (vertical distance from a fixed tidal datum) of the lower
boundary and the species/size composition of the lower boundary. Downward
extensions of the boundaries comprised of masses of relatively young
mussels incurred the greatest increases in energy storage and live mass.
Data are presented in 4 files: (1) Energy storage
- Observational study. Variation in energy storage at three sites
sampled at irregular intervals from 2008 to 2014. Variables
include live mass, dry mass of viscera, and dry mass of the
remainder of the body of individual Pisaster ochraceus. Sample
dates were chosen to represent
natural inter-annual variation in mussel zonation,
rather than tracking continuous time courses.  (2)
Storage-boundary depth relationships. Variables derived from observational
study and include summary measures of energy storage (slope of
the linear regression of dry viscera mass to dry body mass, for dry body
masses< 120 g);  boundary depth (vertical
distance from tidal datum); and the qualitative composition of the lower
boundary. (3) Energy storage and live mass - Experimental study.
Records were made after 1-3 years of
experimental manipulation of the mussel boundaries
on experimental sites. Variables include initial live mass, final
live mass, dry mass of viscera, and dry mass of the remainder of the
body of individual Pisaster ochraceus recaptured
in the three large-scale replicates of the
translocation experiment.  (4) Boundary depth -
Experimental study.  Variables include the type of boundary
manipulation, the change in boundary shore levels with respect to
conventional tidal data, the resulting composition of the lower boundary,
and years of manipulation.  Further information on-site
locations, methods of data acquisition, and definitions of the variables
appear in Methods and Usage Notes below.