GROWTH OF JUVENILE RED ABALONE (Haliotis rufescens) FED WITH GIANT KELP (Macrocystis pyrifera) ENRICHED WITH NUTRIENTS

On the abalone farms in México the main species of macroalgae used to feed juvenile abalone is Macrocystis pyrifera, because is abundant and easy to harvest. However, the proximate composition of M. pyrifera is low in proteins and lipids. The aim of this work was improve the growth of juvenile red abalone (Haliotis rufescens) by enhancing the proximate composition of M. pyrifera by enriching with different nitrogen sources.

The enrichment of M. pyrifera were realized with different nitrogen sources: 1) Industrial liquid fertilizer (7.8% nitrate, 7.8% ammonia and 16.4% urea) added at 44 mM (MPEF), 2) Ammonium chloride added at 1

mM (MPEA), 3) Added seawater as control of the nitrogen enrichment (MPUE). The treatments were maintained by 24 h at 15 °C and continuous light. The blades were sun dried. The proximate composition of algae blades was measure by spectrophotometric methods. The M. pyrifera blades enriched and unenriched were used to feed juvenile red abalone. The abalones were maintained on 18 L plastic buckets and fed at libitum.

The enrichment treatments cause important differences on blade composition (Table 1).

The protein and NFE increased significantly on the two enrichment treatments. Lipids were unchanged by effect of treatments. Ash content had an inverse trend respect proteins on the blades (Table 1).

Were obtained significant differences on the feeding rate, the higher values were with MPEF (Table 2).

The SGR was not significantly different by effect of algae treatments (Table 2).  The SGR decrease at day 30 respect the values obtained on day 15. The mean values of SGR measured at day 30 were higher with MPEA and MPEA treatments; however, high deviations produce not significantly differences. The higher abalone survival was with the MPEA treatment.

The results showed that an increase of the nitrogen available on the media induce protein synthesis in M. pyrifera, and when it was used to feed juvenile abalone at least at the time of this experiment not modify the specific growth rate.