Summary
This doctoral thesis investigated methods to improve aquaculture sustainability by identifying and selectively breeding for improved feed efficiency in two major farmed fish species. The work compared two practical phenotyping approaches (individual rearing versus external tagging within small groups) and explored whether juvenile feed efficiency measurements and metabolic rate could serve as indirect selection criteria. Findings indicate that phenotyping method choice significantly affects FE estimates, and that feeding regime (restricted vs ad libitum) influences which individuals rank as most efficient.
Regional applicability
Although conducted on Mediterranean and tropical farmed species rather than United Kingdom-relevant stocks, the methodological framework for assessing and breeding for feed efficiency is directly transferable to UK aquaculture operations and policy objectives around sustainable intensification. The identification of feeding-regime-dependent efficiency rankings has implications for UK farm management protocols and breeding programme design.
Key measures
Individual feed efficiency (feed conversion ratio), oxygen consumption (metabolic rate), feed intake at different feeding regimes (restricted vs satiation), phenotyping method comparison (individual rearing vs visual tag identification in groups)
Outcomes reported
The study evaluated direct measurement methods for individual feed efficiency (FE) in European sea bass and Nile tilapia, and tested indirect predictor variables for selective breeding programmes. Key findings include that juvenile FE estimates in tilapia predicted whole-cycle production FE, the two phenotyping methods (individual rearing vs external tagging) yielded non-equivalent estimates, and fish efficient at restricted feeding were not necessarily efficient at satiation.
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