Evaluation of new microparticulate diets for early weaning of Atlantic cod (Gadus morhua): Implications on larval performances and tank hygiene

In recent years, interest in the intensive culture of Atlantic cod (Gadus morhua) has increased dramatically due to several factors including a reduced supply of cod from capture fisheries, a high market price for wild cod and the suitability of the species for culture. One of the major problems facing the industry has been the high cost and unreliability of live feeds, specifically the live feed Artemia. The main objective of this project was to determine whether Artemia use could be reduced or replaced completely with two novel microparticulate diets (MPD's), without negatively compromising growth, survival performance and tank hygiene under simulated commercial conditions.The experiment consisted of four treatments, a live feed control treatment (group A), a 50% Artemia replacement treatment with MPD-1 (group B), a 100% Artemia replacement treatment with MPD-1 (group C) and a 100% Artemia replacement treatment with MPD-2 (group D). All treatments were run in triplicate. Growth performances, development (standard length, eye diameter, myotome height and wet weight), water quality (bacteriology and spectrophotometry) and survival were measured throughout the duration of the trial.The results of the experiment indicate that the treatments containing Artemia (groups A and B) both achieved significantly higher growth rates than treatments that did not contain Artemia (groups C and D). The highest survival rates achieved at 70 dph were in treatments A and D (13.8% ± 0.7% and 14.2% ± 2.1% respectively) when compared to treatments B and C (11.8% ± 0.3% and 5.5% ± 1.3% respectively). Survival was also significantly higher in treatment B than in treatment C. This study demonstrates that while the best growth and survival rates are still achieved when cod larvae are fed Artemia, combining live feeds and commercially available MPD's (co-feeding) can produce comparable growth and survival rates thus potentially reducing the reliance on live feeds. However the complete replacement of Artemia with MPD's still significantly reduced growth potential suggesting that the nutritional composition of MPD's, requires further investigation.