Thirteen environmental variables were used to describe habitat conditions at each sampling
site. Measurements of all variables were made in situ between 7 h and 12 h before shrimp
sampling. Conductivity (µS·cm−1), water temperature (◦C), dissolved oxygen (mg·L−1) and pH
were measured using a multiparameter apparatus (WTW 840i). Turbidity (NTU) was measured
using a turbidimeter (AQUA LYTIC CD 24). The habitat variables included current velocity
(m·S−1), which was taken in mid-channel on five occasions by timing a floating object
(polystyrene cube) over a five-metre stretch of the river. The value of current velocity was the
average of the five trials. Water depth (m) and width (m) were measured (average of five trials)
to the nearest centimetre using a decametre. Canopy cover (%), substrate type (mud, sand,
gravel), and woody debris (%) were estimated visually at each sampling site as described by