|Lellis, William - USDOI, USGS, WELLSBORO,PA|
Submitted to: World Aquaculture Society Meeting
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2006
Publication Date: June 1, 2006
Citation: Barrows, F., Lellis, W.A. 2006. Effect of diet processing method and ingredient substitution on feed characteristics and survival of larval walleye, stizostedion vitreum. World Aquaculture Society Meeting. Interpretive Summary: Fish production is dependant upon a reliable supply of fingerlings. The larval stage of production is often limiting due to low survival and poor feed consumption for many species such as striped bass, walleye, and many other small-egged species. Development of feeds that are readily consumed, contain all essential nutrient, and can be economically produced is critical for expansion of aquaculture with these species. Two methods of larval feed production were developed and compared using walleye as a surrogate for small-egged species. Two feed formulations and two methods of feed production were tested, in two different experiments. The two processing methods produced particles of the same size, but with different physical characteristics such as sink rate and apparent water stability. The feed formulations tested in these studies supported survival rates equivalent to or greater than survival for fish fed a commercial specialty feed (Fry Feed Kyowa). Growth rate, however, was much greater for the fish fed the specialty feed. This paper reports an open-formula feed that can support survival equivalent to specialty larval feeds. There have been very few nutrient requirement trials with larval fish due to an inability to easily package the nutrients in a form that the fish will consume. Also, the production of experimental feeds in the laboratory has been inadequate. The development of the PARA process and practical type formulations provide the tools necessary to further develop larval fish feeds and to begin nutrient requirement determinations for larval fish.
Technical Abstract: Two methods were developed for the production of feeds in the sizes needed to replace live Artemia nauplii (250-400 um) and rotifers (<250 um) in larval fish culture. The first method, micro-extrusion marumerization (MEM), has been tested in the laboratory and with feeding trials for approximately 7 years and produces particles that are palatable and water stable. A wet mash of ingredients is first extruded through a 500 um screen in a radial discharge extruder to produce long noodles. The noodles are then fractured, shaped, smoothed, and densified in a marumerizer. The second method, particle-assisted rotational agglomeration (PARA), does not require an extruder and is capable of producing high yields of particles less than 250 um in diameter. A wet mash is placed directly in the marumerizer and rotated with inert beads to form, shape, and densify the particles. Feeds produced with the PARA method have lower density than feeds produced by MEM. Both methods are sensitive to diet formulation and the binding characteristics of the ingredients. Each method was used to produce feeds in the 250-400 um and 400-700 um range and compared with a commercial diet (Fry Feed Kyowa*) for feeding larval walleye in two experiments. In the first experiment, 30-d survival was greater (P < 0.05) for fish fed a diet produced by PARA (49.1.0%) than by MEM (27.6%) or the commercial formulation (24.4%). In the second experiment, 23-d survival was equal among fish fed either a PARA (48.4%) or commercial diet (46.5%), but lower (P < 0.01) for fish fed an MEM diet (19.6%). Inclusion of 4% freeze-dried Artemia improved (P < 0.04) survival of fish fed MEM particles, but not those fed PARA particles. Fish fed Fry Feed Kyowa had greater (P < 0.05) weight gain than fish fed other diets in both experiments. Data indicate that the PARA method of feed processing produces smaller, lower-density particles than the MEM process, and that feeds produced by the PARA process support higher survival of larval walleye with low capital and operating costs.