Fishmeal is being trusted as the most reliable protein source due to its nutritional quality in terms of attractability, palatability, digestibility, excellent nutrient profiles to fulfil the dietary requirement of aquatic species. The aquaculture sector consumes >70% of global fishmeal, though aqua feeds constitute only 4% in total industrial feed production (900-1,000 Mt in 2018). The global fishmeal production has shown a downward trend of 26.50% during 2000 to 2018 due to the occurrences of El Niño-Southern Oscillationsand other climatic events, which in turn increased the fishmeal price from 452 USD/t (2000) to 1596.54 USD/t (2018). The increasing trend of aquaculture production along with reduced fish-in/fish-out ratios (0.63 in 2000 to 0.33, 0.22 in 2010 and 2015 respectively) indicates the resilience of the aquafeed sector for fishmeal replacement. The wide availability, reasonable price and reliable nutrient content made an interest in plant protein sources, but their utilization was limited due to poor digestibility, imbalanced profiles of essential nutrients and the presence of anti-nutrients. Numerous methodologies are invented in recent times to enrich the nutritional qualities for maximizing the utilization of plant proteins in aquafeed formulations. The present review concludes that the aquafeed sector should use climate economics and technological innovations for substituting fishmeal to formulate the cost-effective feeds. K E Y W O R D Sclimate change, fermentation, fishmeal, input, output ratio, plant protein sources, shrimp feed

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Four commercial solvent‐extracted oilseed meals/cakes, viz. soybean meal (SBM), groundnut oil cake (GNC), rapeseed meal (RSM) and sunflower oil cake (SFC), were fermented with fungus Aspergillus niger, and its effect on apparent digestibility coefficient (ADC) was studied in Penaeus vannamei. Reference diet and eight experimental diets containing 700 g/kg reference diet and 300 g/kg test ingredient with 5 g/kg chromic oxide were formulated. Each diet was randomly allotted to three tanks containing ten shrimps. Shrimps were adapted to the experimental diets for a week, and faeces were collected using Falcon tube from second week onwards. The ADC of all the ingredients significantly (p < .05) increased with fermentation and the increase being higher in SBM (78.46%–91.71%) for dry matter and in SFC (71.51%–87.02%) for protein. Analysis of variance showed that the ADC of both dry matter and protein significantly (p < .05) differed in treatments (p = <.001) and ingredients (p = <.001). The average ADC of ingredients was ranked as SBM > GNC > RSM > SFC. The most digestible essential amino acid (EAA) in fermented ingredients was methionine in SBM, arginine in GNC, valine in RSM and histidine in SFC. A better improvement in amino acid digestibility was observed in fermented SFC. Results indicated that P. vannamei efficiently digests fermented ingredients compared to unfermented ones.

The incorporation of plant protein sources in shrimp feed is limited due to unbalanced amino acids and higher anti-nutrients. In the present study, soybean meal (SBM), groundnut oil cake (GNC), rapeseed meal (RSM), sunflower oil cake (SFC) and guar meal (GRM) were subjected to natural, bacterial, fungal and yeast fermentation methods. The essential amino acid contents were increased by 4-28% in SBM, 7-26% in GNC, 3-27% in RSM, 8-18% in SFC and 4-14% in GRM. The increase was better for lysine with fungal fermentation (2.31-4.01%). The improvement in other limiting amino acids viz., methionine and tryptophan also showed positive response to fermentation. The analytical results showed improved essential amino acid index (EAAI) in the fermented ingredients and the increase was better with RSM (0.82 to 0.92) using Aspergillus niger. Fiber fractions were reduced (p<0.05) in fungal and yeast treated samples but not due to natural or bacterial fermentation. The reduction of cellulose and hemicellulose was not only influenced by the inoculum but also on the ingredient used. The reduction of anti-nutrients (p<0.05) such as trypsin inhibitor, phytic acid, saponin, tannin, glucosinolate and guar gum were found to be lower in natural fermentation than other methods. The results indicated that fungal fermentation is more suitable for improving the nutritional quality of plant protein sources and this data will pave way for higher fishmeal replacement in shrimp feed formulations.