Common moist diet replacement to promote sustainable Cobia Rachycentron canadum (Linnaeus) near- shore farming in Brazil

Felipe Schwahofer Landuci,Giselle Eler,Bruno Cavalheiro Araujo,Luis Henrique Da Silva Poersch,Marcelo Pereira Maia,Marcelo Duarte Pontes,Artur Nishioka Rombenso

doi:10.1590/1678-992x-2017-0320

Abstract

ABSTRACT: Cobia is one of the most promising warm water aquaculture species. In Brazil, cobia farming began in 2008 in the state of Rio de Janeiro from experimental scale facilities to regular near-shore farms based on fresh/frozen fish diets composed mostly of Sardinella sp. Despite the encouraging results achieved in the promotion of sustainable cobia farming, we advocate the replacement of fresh/frozen fish by a practical formulated feed. This experiment evaluated the zootechnical performance and environmental efficiency of moist and practical formulated feeds in early grow-out phases in the cycle of cobia nearshore cage culture. Four hundred and twenty juvenile cobia (151 ± 7 g) were fed with moist feed and practical formulated feed for 56 days. Biometrics were taken every two weeks and diets were analyzed for proximate composition, fatty acid composition and pellet quality. Although growth performance was equivalent between treatments, feed consumption and feed conversion ratios (FCR) were different (p < 0.05) and varied according to water temperature. Cobia fed moist feed exhibited an FCR two times higher than those fed formulated feed. Elevated settling speed and low floatability contributed to higher heterogeneity and lower efficiency of fish fed moist diet. Nitrogen excretion rate was reduced (64 %) and protein efficiency ratio elevated (27 %) within formulated diet groups in comparison to those fed moist diet (79 % and 15 %, respectively). The fatty acid profile of cobia muscle was similar across the groups. With no negative effects of diet substitution on production performance and improvement of environmental efficiency, this approach can be applied and advocated globally and contribute to the responsible intensification of sustainable marine fish culture.

Highlights

Cobia aquaculture started in Taiwan in the 90’s, and underwent expansion after the development of massive fingerling production technology in 1997, spreading in the following years to other Asian countries and the western hemisphere (Benetti et al, 2010; Liao et al, 2004; Nhu et al, 2011)
A recent survey conducted in central Vietnam stressed that fish farmers choose to use trash fish for aquaculture due to the low cost, production performance, lack of alternative feeds and purchase convenience (Huntington and Hasan, 2009)
Their survival ratio was elevated, higher than 94 % for both treatments, which is consistent with other studies (Benetti et al, 2010; Liao et al, 2004; Sampaio et al, 2011; Weirich et al, 2010)

Summary

Introduction

Cobia aquaculture started in Taiwan in the 90’s, and underwent expansion after the development of massive fingerling production technology in 1997, spreading in the following years to other Asian countries and the western hemisphere (Benetti et al, 2010; Liao et al, 2004; Nhu et al, 2011). Cobia cultured in offshore net cage systems generally rely on formulated feeds (Liao et al, 2004), most traditional near-shore cobia production is still based on rough fish, commonly referred to as trash fish (Petersen et al, 2015). In Brazil, cobia farming started in offshore net cages in the northeastern region, but prospered in the southern region in near-shore systems, encouraged by experimental ongrowing results (Sampaio et al, 2011). Despite the positive results achieved so far, the availability of a high quality cost-effective formulated aquafeed is paramount to guaranteeing a sustainable development allied to the economic feasibility of a near-shore cobia cage culture, but the issue is how to achieve a successful transition especially in view of the operational comprehension by producers of the benefits of practical formulated diets Substitution of formulated feeds has been encouraged, by virtue of its significant implication for the environment and the culture system, which includes the increasing of nutrient input, risk of contamination, rise of pathogen incidence, variations in nutritional quality and higher related feed conversion ratio (Kim et al, 2007; Liao et al, 2004; New, 1996; Nhu et al, 2011)

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Conclusion