46 SEPTEMBER 2012 (Fig. 2). Worms provide a balanced supply of essential amino acids including tyrosine, tryptophan, arginine, histidine, cystine and methionine, as well as calcium, phosphorus, iron, carotene and vitamins A and B2 (Ivelva 1973). They are readily accepted for direct consumption by juvenile sturgeon (Ivelva 1973) and winter flounder (KleinMacPhee 1978, Walsh 2012), indicating that, as a feed, white worms provide adequate palatability, amino acid balance, energy and digestibility, all requirements of an appropriate protein source for aquafeeds. White worms provide distinct advantages over polychaetebased feeds. The small size of white worms allows the option of direct feeding (live) to small or juvenile fishes. White worms can be reared in damp soils or substrates, eliminating the need for a water-based culture system. Terrestrial, air-breathing organisms can congregate at much higher densities than those of aquatic animals (Ivelva 1973). Preliminary work has been conducted to minimize the amount of soil necessary for production by growing white worms on agar plates (Springett 1964). As a live feed, white worms are effective because they tolerate a wide range of temperature and salinity (Ivelva 1973). Although optimal temperature for growth and reproduction peaks at 15-21 °C, white worms will survive in freezing water temperatures and can persist for over 30 min at 33 °C if necessary. Salinity tolerance spans the spectrum of most natural waters. Worms will continue moving in water, eliciting a behavioral feeding response from predaceous juvenile fish in fresh, brackish-estuarine, and full-strength seawater. Individual oligochaetes can be cut into smaller pieces, if needed, and these pieces will continue to move when submerged. Providing white worms as a live feed can slow the deterioration in tank water quality because any excess feed remains alive and thus does not break down in tanks like other feeds, remaining available and moving until the appetite of the target cultured species returns. The use of marine worms as a protein source in formulated fish feeds is not a new concept. Dragonfeeds, a subsidiary of UK-based Blue Marine Feeds Limited, combines the cultured polychaete Nereis virens with plant proteins to produce a feed with no fishmeal that has an amino acid profile similar to fishmeal. With a 70 percent protein and 2 percent lipid composition, the Dragonfeed product is marketed for finfish and shrimp aquaculture. Aquathrive, manufactured by Reed Mariculture/Reef Nutrition, combines fishmeal and oil with Terebellid polychaetes to produce a 46 percent protein, 11 percent lipid feed that is marketed mainly to aquarium hobbyists. To summarize, white worms are an interesting candidate for aquaculture feeds because of the following properties: • Rearing and harvesting ease; that is, worms thrive on neglect. • Nonselective, composting feeding nature; it is cheap to feed worms. • Ability to survive in a wide range of temperatures (0–33 °C) and salinities (0–35 ppt), even when cut into pieces. • Excellent nutritional content (75 percent protein, 15 percent lipid). Potential Benefits of Use The potential economic benefits of white worm production for commercial aquaculture might include incorporation into formulated diets or development of alternative organic diets for carnivorous marine fishes. Use of diets that are reared and harvested easily, thrive with minimal maintenance and survive in salt/brackish water for prolonged periods also may decrease overall costs by reducing feed waste and the need for water quality maintenance. White worms present the potential for mass-scale production, involving mutually beneficial local collaboration with an inexpensive materials cost. In addition, production of white worms as an aquaculture feed or feed ingredient may enable a reduced reliance on fishmeal and the opportunity to culture marine species on a natural, sustainable feed. The development of systems to grow white worms for freshwater, brackish or marine baitfish and/or fee fishing operations is worth serious investigation, inasmuch as sourcing nutritionally balanced diets for small-scale hatchery and nursery operations is a serious hurdle for many producers. The mass culture of invertebrate live feeds as an advanced diet for juveniles used in estuarine/marine stock enhancement programs for species such as salmonids, flatfish or shad may increase stocking effectiveness, survival and recruitment of released fish. This contributes to potentially greater landings for fishermen and an economic boost for fishing communities. Notes 1 Department of Biological Sciences, Spaulding Life Sciences, University of New Hampshire, Durham, New Hampshire, 03824, United States. michelle.walsh@unh.edu References Ivleva, I.V. 1973. Mass Cultivation of Invertebrates: Biology and Methods. Israel Programme for Scientific Translations, Jerusalem, Israel. Klein-MacPhee, G. 1978. Synopsis of biological data for the winter flounder, Pseudopleuronectes americanus (Walbaum), NOAA Techical Report 414. Memis, D., M. S. Celikkale and E. Ercan. 2004. The effect of different diets on the white worm (Enchytraeus albidus Henle, 1837) reproduction. Turkish Journal of Fisheries and Aquatic Sciences 4:57. Springett, J.A. 1964. A method for culturing Enchytraeidae. Oikos 15:175-177. Vedrasco, A., V. Lobchenko, I. Pirtu and R. Billard. 2002. The culture of live food for sturgeon juveniles, a mini review of the Russian literature. International Review of Hydrobiology 87:569-575. Walsh, M.L. 2012. Examining conditioning strategies for flatfish stock enhancement to promote feeding success. Ph.D. dissertation, University of New Hampshire, Durham, NH, USA.
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