The suitability of the free-living nematode panagrellus redivivus as alternative live food for first feeding fish larvae

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Although hobby aquarists have long suggested that free-living nematodes could serve as a food source for first-feeding fish, their practical use has been limited due to the absence of effective mass production technologies. A new method for producing Panagrellus redivivus allows hatchery operators to utilize a cost-effective, standardized live food for fish larvae. This technique involves cultivating nematodes in monoxenic solid culture using Saccharomyces cerevisiae in autoclavable plastic bags. Various culture media have been tested, achieving yields of approximately 400 million nematodes per kg of medium. The mass-produced nematodes have been successfully tested on common carp and whitefish larvae, which vary in size and digestive morphology. Observations of nematode digestion stages in fish larvae reveal that P. redivivus is readily consumed. Using stable isotope methods, researchers have precisely measured nutrient retention and carbon assimilation in first-feeding larvae. Fish fed nematodes exhibited high survival rates and adapted easily to commercial dry diets after just one week. Additionally, enriching the culture medium with essential fatty acids can enhance the nutritional value of the nematodes. Given their small size and resilience in seawater, P. redivivus shows great promise as live food for small-mouthed marine fish larvae. This overview highlights the suitability of P. redivivus as an alternative live food an