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Early weaning of larval giant Galaxias argenteus in New Zealand

Weaning period of larval giant larval giant kōkopu, Galaxias argenteus, was shortened in a study conducted in New Zealand, providing an option in significantly decreasing the expensive live prey feeding period.

From the usual 28 days, weaning can be moved back by three days after hatching (DAH). This early weaning protocol saved 13 percent on live feed cost.

“This is an indication that the larvae could be weaned onto formulated diet at least three days earlier, which if confirmed by further research to be the case, would provide a significant cost saving for commercial production. It is critical to note that the two feeds (Otohime and Artemia) were never in the water column at the same time because of settlement rate, time between each provision of feed, and the water turnover rate within the tank,” authors William J. G. McKay and Andrew G. Jeffs said in the research published on Journal of the World Aquaculture Society.

Otohime is a dry formulated feed.

Giant kōkopu is an emerging aquaculture species in New Zealand. It has a high market value and also used to supplement the wild fishery. At this stage, financial viability is compromised by a number of challenges, the most serious being the high cost of hatchery cost of live feeds. “Larval fish require a live feed as a first diet because the movement of live feed triggers predatory behavior and the initiation of exogenous feeding,” they said.

Marked increase in the consumption of formulated diets by larval giant kōkopu was observed over the ten-day period from 18 to 28 DAH. “Of particular importance is the ability of larvae aged 25 DAH to achieve the same level of gut fullness when fed a formulated diet as larvae at 28 DAH. This is an indication that the larvae could be weaned onto formulated diet at least three days earlier, which if confirmed by further research to be the case, would provide a significant cost saving for commercial production,” they explained.

Other challenges on culture of the species stem from high cost of raw materials, labor, capital investment and water quality requirements of live food production and also the variable nutritional quality.