The size distributions in the populations of Atya
lanipes and Xiphocaris elongata followed the distribution
observed in previous studies in Puerto Rico (Covich,
Crowl & Scatena, 2003; Cross et al., 2008) where more
than 60% of the shrimp in these populations have a CL
between 12 and 17 mm. The Atya lanipes populations in
these locations can be divided into three main cohorts:
cohort 1 (18 mm CL) comprised mature and older adult
shrimp with low reproductive output, slow growth rate,
and which tended to be permanent residents of the
pools. These size distributions and population structures