  Motivated by the finding that there is some biological universality in the
relationship between school geometry and school biomass of various pelagic
fishes in various conditions, I here establish a scaling law for school
dimensions: the school diameter increases as a power-law function of school
biomass. The power-law exponent is extracted through the data collapse, and is
close to 3/5. This value of the exponent implies that the mean packing density
decreases as the school biomass increases, and the packing structure displays a
mass-fractal dimension of 5/3. By exploiting an analogy between school geometry
and polymer chain statistics, I examine the behavioral algorithm governing the
swollen conformation of large-sized schools of pelagics, and I explain the
value of the exponent.
