Squid meal may have also contributed to
the growth rate in fish. Although not widely used in grow-out diets,
squid meal or extracts are known to improve spawning quality in
marine fish broodstock (Fernández-Palacios et al., 1997) and the nutritional value of microdiets for larval fish (Nankervis and Southgate,
2006). Regarding the use of soy protein and the possibility of intestinal
irritation, longfin yellowtail may be more tolerant of high dietary SPC
inclusion than other yellowtails. The FM20 diet contained more than
46% SPC by weight, well above the maximum 20% inclusion rate recommended in diets for yellowtail kingfish (Seriola lalandi) (Bowyer et al.,
2013). In addition, the combined proportion of algal and soy protein
in the diets increased with FM replacement level, reaching more than
half of the total protein in the FM20 diet. This indicates the potential
of using these plant ingredients as protein source in S. rivoliana diets.