2. Materials and methods
2.1. Diet formulations
Red marine seaweed, G. arcuata, was freshly collected from the
near-shore waters of the Red Sea coast at Jeddah, Saudi
Arabia. Algal samples were thoroughly washed with sea water,
tap water and distilled water, sun dried for 48 h and fine-milled
with a laboratory blender. The Gracilaria meal was then passed
through a mesh sieve to produce a raw Gracilaria meal for
proximate analysis (Table 1). Other dietary ingredients were
purchased from a local feed company (Maram Feed Company,
Riyadh, KSA). Proximate analysis of major dietary ingredients
was performed prior to the formulation of experimental diets.
All diets contained approximately 35% protein (Table 2). The
diet without G. arcuata served as a control diet (D1), while
the three other diets were formulated such that G. arcuata
replaced a proportion of standard fish meal, respectively 10%
for D2, 20% (D3) and 30% (D4). Table 2 represents the formulation
of the diets and their proximate chemical composition.
Dietary ingredients were mixed in a food mixer (Legacy,
USA) with water (at around 50 C) to produce a 2 mm pellet.
The moist pellets were then oven dried at 105 C and stored
frozen at 20 C until use.