Effects of two commercial microdiets on growth and survival of barramundi (Lates calcarifer Bloch) larvae within various early weaning protocols

Abstract

Because of high costs and labour requirements along with the highly variable nutritional value of live feeds, we investigated the possibility of early weaning for barramundi (Lates calcarifer Bloch) larvae aimed at reducing the use of Artemia. Two commercial microdiets, Gemma Micro (Skretting, Australia) and Proton (INVE, Belgium) were compared for growth and survival of larvae using three weaning protocols, until 33 days posthatch (dph). Enriched rotifers were fed to larvae in all protocols through mouth opening until 21, 18 and 30 dph (protocols 1, 2 and 3, respectively). At 13 dph, enriched Artemia metanauplii were introduced to weaning protocols 1 and 2, and continued until 29 and 24 dph, respectively, whereas protocol 3 did not receive Artemia. Microdiet was initiated at 20, 16 and 13 dph in protocols 1, 2 and 3, respectively. Barramundi larvae grew successfully to 33 dph when co‐fed rotifers and microdiet, and significantly larger larvae resulted from feeding Gemma Micro rather than Proton, when Artemia were not used. However, larvae weaned onto Proton using a longer period of Artemia provision were significantly larger than larvae reared according to all other protocols. Survival was significantly higher in all Gemma Micro protocols when compared with Proton protocols. This was in part due to higher cannibalism when using Proton compared with Gemma Micro (22.8 ± 0.9% and 9.2 ± 0.6%, respectively). Cannibalism became more noticeable in all protocols when the larvae reached 7–8 mm standard length and further increased after the cessation of live feed. Tank biomass production was the highest when larvae were weaned onto Gemma Micro including a short period of Artemia provision as a result of a combination of high growth and survival. However, similar biomass production resulted when larvae were weaned directly from rotifers onto Gemma Micro and/or from a prolonged Artemia period onto proton. The success of weaning barramundi larvae directly to microdiet from rotifers, thus eliminating the need for Artemia, was influenced by the microdiet. Relatively higher levels of free amino acids and lipids were believed to contribute to increasing larval growth and survival. Larvae that were fed Gemma Micro showed higher growth when Artemia were utilized for a shorter period, while Proton‐fed larvae benefited from an extended Artemia feeding period.

Assessment of Nutrient Allocation and Metabolic Turnover Rate in Pacific White ShrimpLitopenaeus vannameiCo-Fed Live MacroalgaeUlva clathrataand Inert Feed: Dual Stable Isotope Analysis

“…This fact is highlighted by the poor growth and survival observed in shrimp fed on macroalgal biomass only. The positive effect of supplying both live feed and an inert diet has been observed recurrently in larval and juvenile crustaceans (Teshima et al 2000, Thompson et al 2002, Gamboa-Delgado & Le Vay 2009a and fish (Kolkovski et al 1993, Rosenlund et al 1997, Curnow et al 2006.…”

Influence of Live and Dry Diets on Growth and Survival of Chub (Leuciscus cephalus) Larvae

“…Further factors that may have increased larval growth and survival when using live feed is that they usually have a much better contrast than artificial feeds and so produce a feeding trigger effect by their continuous movement [24], and that as Artemia actively swim, this ensures a good spatial distribution of food items resulting in more frequent encounters for all larvae [24]. Nevertheless, there have been some successes for larval production from feeding micro-diets after feeding live diets [25]. For example, a range of marine species that were commercial feed two live and dry foods demonstrated excellent larval growth and survival [26] although until now this had not yet been shown in any cyprinidae fish species.…”

Co-feeding of live feed and inert diet from first-feeding affects Artemia lipid digestibility and retention in Senegalese sole (Solea senegalensis) larvae

“…Similar results were found for other species (Kolkovski et al, 1997;Rosenlund et al, 1997), when an early co-feeding was attempted. Curnow et al (2006) co-fed Asian sea bass Lates calcarifer on two different inert diets, and verified lower or higher survivals depending on fish size and diet type. It has also been suggested that co-feeding larval sole from 1 mg of larval weight may even improve survival rates at weaning, since it might enhance digestive maturation and/or stimulate digestive secretion (Engrola et al, 2007), even though a higher size dispersion could be observed.…”