Browsing by Author "Narimbi, J"

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    Isotopic tools for better management of aquatic environment and resources
    (Australasian Environment Isotope Conference, 2015-07-08) Mazumder, D; Saintilan, N; Kobayashi, T; Wen, L; Rogers, K; Hollins, SE; Johansen, MP; Walsh, C; Narimbi, J; Sammut, J
    Water is a vital resource that is under ever-increasing demand from population and industry growth, agricultural development, and environmental allocations that are crucial to sustain the natural ecosystems upon which we all rely. Analysis of naturally-occurring stable isotopes (d13C and d15N) have emerged as powerful techniques for addressing research and management-related questions in ecology and aquaculture. Our work on coastal wetlands has identified carbon and nutrient dynamics, the sequestration potential of saltmarsh and mangrove systems, and anthropogenic impacts on aquatic food chains. We compared trophic position and dietary sources in freshwater wetlands during a severe El Nino drought (2007) and following a subsequent series of wetter than average La Nina years (2013), and identified that food chains expand and contract with oscillations in climate phase in the absence of new sources of carbon. We applied isotopic tools in aquaculture, which is the fastest growing food-producing sector in Australia and around the world and accounts for one-third of global fish production. However, production and profitability from inland and coastal aquaculture are often low due to environmental constraints and the increasing cost of production. Our work to develop low-cost feeding strategies for PNG fish farmers suggests operational costs can be reduced by carefully utilising production inputs or changing the ingredients used in feed formulations. These results provide insights for further applications of stable isotopes in the aquatic ecosystem studies.
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    Stable isotope analysis to quantify contributions of supplementary feed in Nile Tilapia Oreochromis niloticus (GIFT strain) aquaculture
    (John Wiley & Sons, Inc., 2018-03-12) Narimbi, J; Mazumder, D; Sammut, J
    Nile tilapia (Oreochromis niloticus) is currently one of the most farmed freshwater fish and contributes significantly to total global aquaculture production. The genetically improved strain of O. niloticus (GIFT) was introduced to Papua New Guinea (PNG) in 1999 to improve food and income security. The high cost and low availability of commercial fish feed hinder the growth of GIFT farming in PNG. Stable carbon and nitrogen isotopes were used to determine the role of supplementary and natural food sources in the diet of GIFT in pond-based aquaculture. Two treatments were used: treatment 1 was daily feeding, and treatment 2 was weekly feeding, each with three replicates. Isotopic analysis of muscle tissue and all potential food sources showed that pellet feed contributed 7% to the growth of GIFT in daily-fed ponds and 33% in the weekly-fed ponds. Highly enriched δ15N values for chicken manure, compared to depleted values for GIFT and other natural food sources in both treatments, clearly indicate insignificant contributions of this input to production. After 90 days of cultivation, the average final body weight of GIFT receiving daily feed inputs was 134 g (average 19 cm), while for weekly-fed it was 92 g (17 cm). The feed conversion ratio (FCR) was poor (6.4:1) in the daily-fed GIFT ponds compared to a better, and preferable, FCR (1:1) in the weekly-fed ponds. The findings of this study show that pelleted feed was not the major contributor to the growth of GIFT. Genetically improved farmed tilapia aquaculture should focus on enhancing natural food availability for fish production. © 2018 John Wiley & Sons, Inc.