The activity of serum lysozyme (LSZ) was determined
following the turbidimetric method (Boman et al., 1974; Hultmark
et al., 1980), which involved the lysis of lysozyme-sensitive Gram-
positive bacteria by LSZ. The serum total protein concentration of fish,
whichwas determined using the biuret protein assay kit,was calculated
using bovine serum albumin as the protein standard and expressed as
mg mL−1
of fish serum.