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Effect of diet processing method and ingredient substitution on feed characteristics and survival of larval walleye, Sander vitreus

Two methods were developed for the production of larval fish diets. The first method, microextrusion marumerization (MEM), has been tested in laboratory feeding trials for many years and produces particles that are palatable and water stable. The second method, particle-assisted rotational agglomeration (PARA), produced diets that have lower density than diets produced by MEM. Each method was used to produce diets in the 250- to 400- and 400- to 700-??m range and compared with a reference diet (Fry Feed Kyowa* [FFK]) for feeding larval walleye in two experiments. The effect of substituting 4% of the fish meal with freeze-dried artemia fines was also investigated. In the first experiment, 30-d survival was greater (P < 0.05) for fish fed a diet produced by PARA without Artemia (49.1.0%) than for fish fed the same diet produced by MEM (27.6%). The addition of Artemia to a diet produced by MEM did not increase survival of larval walleye. Fish fed the reference diet had 24.4% survival. In the second experiment, there was an effect of both processing method and Artemia supplementation, and an interaction of these effects, on survival. Fish fed a diet produced by PARA without Artemia supplementation had 48.4% survival, and fish fed the same diet produced by MEM had only 19.6% survival. Inclusion of 4% freeze-dried Artemia improved (P < 0.04) survival of fish fed MEM particles but not those fed PARA particles. Fish fed FFK had greater weight gain than fish fed other diets in both experiments. Data indicate that the PARA method of diet processing produces smaller, lower density particles than the MEM process and that diets produced by the PARA process support higher survival of larval walleye with low capital and operating costs. ?? Copyright by the World Aquaculture Society 2006.

Journal of the World Aquaculture Society

A comparison of black drum, red drum, and their hybrid saltwater pond culture

Hybridization has been used in aquaculture to produce fish that exhibit improved growth and survival over parent species. Previous studies produced an intergeneric hybrid by crossing female black drum Pogonias cromis with male red drum Sciaenops ocellatus . In the present study, the two parent species and their hybrid were simultaneously cultured in ponds for 9 mo. Two- to three-day-old larvae of each type were initially placed into three separate 0.1 ha ponds. After about 41 d, fingerlings of each type were transferred from the larval culture ponds to six 0.2 ha ponds. Two ponds each received 3,000 black drum, red drum or hybrid fingerlings. Fish were fed a commercial feed and harvested after about 230 d. At harvest, mean weight, mean total length, and production for the hybrids was 190 g, 245 mm, and 10.7 kg/ha/d, respectively; red drum averaged 142 g, 236 mm, and 7.0 kg/ha/d; and black drum averaged 144 g, 214 mm, and 10.6 kg/ha/d. Black drum survival was 94%, red drum survival was 63%, and hybrid survival was 72%. Hybrid growth was more rapid than either parent. A taste panel failed to identify differences in flavor between the three fishes. With similar flavor and faster growth, hybrid drum have potential for commercial mariculture.

Journal of the World Aquaculture Society

Design procedure for hooded surface oxygen absorption systems

A design procedure addressing effluent total dissolved gas pressure limits along with standard performance indicators such as oxygen absorption efficiency (kg absorbed/kg applied), and transfer efficiency (kg/kW.h), is presented for surface agitation equipment operating in an oxygen-enriched atmosphere. Application of this contactor type in closed culture systems is attractive given its insensitivity to biological fouling and ability to operate without the need for a significant hydraulic gradient. Performance algorithms were developed through application of chemical reactor theory, Henry's Law and the Ideal Gas Law. In the analysis, gas and liquid phases were treated as being homogeneous. The design steps presented are unique in that required mass transfer coefficients (K L a), operating pressures (CP), and oxygen feed rates (G/L) are calculated for target changes in both dissolved oxygen and nitrogen without the use of iterative numerical procedures. A second calculation sequence establishes the sensitivity of system performance to changes in G/L when CP and K L a are known.

Journal of the World Aquaculture Society

Continuous monitoring of dissolved oxygen and total dissolved gas pressure based on head-space partial pressures

We describe an instrument prototype that measures total dissolved gas pressure (TGP) and dissolved oxygen (DO) without need for standard wetted probe membranes or gas permeable tubing. Measurements were based instead on gas-phase partial pressures that develop within the head-space of a pressure vessel, and on Henry's Law. Performance trials established that differences between standard instrumentation and test instrument OP readings average -1.6-mm Hg (SD = 2.19, range -4.8 to -5.3) within the ΔP range of -72 to 123-mm Hg. Additional trials demonstrated the ability of the instrument to closely follow positive and negative changes in TGP at rates approaching 30-mm Hg/h. Here, the difference between test and standard instrumentation derived TGP averaged 3.4-mm Hg (range 0–41). Differences in ΔP measured by test instrument and gasometer increased with water throughput; mean differences were -3.9, -4.3, and -6.0 for water throughput of 4.6, 6.7, and 7.8 L/min, respectively. However, time to reach 90% of the steady-state instrument reading was highest for low water throughput; equilibrium times averaged 90.9, 44.4, and 44.7 min for water throughput of 4.6, 6.7, 7.8 L/min, respectively. Differences between titration and test-instrumentation based DO measurements were acceptable, averaging -0.11 mg/L (SD = 0.41, range -0.85 to 0.85) over DO from 3.3 to 19.2 mg/L and for 11.1 and 24.2 C. Whereas test instrument DO readings were indistinguishable from Winkler titration at 24.2 C; at 11.1 C there was a tendency for test instrument readings to be lower than Winkler titration at DO < 14 mg/L and higher at DO > 14 mg/L. Trials conducted under biological fouling conditions demonstrated the test instrument's ability to operate with 30% of the maintenance required by standard instrumentation.

Journal of the World Aquaculture Society

Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus (L.)

Induction of triploidy and tetraploidy in Nile tilapia, Oreochromis niloticus , was investigated by heat shock, cold shock, hydrostatic pressure, and/or chemicals (cytochalasin A, B, and D). Additionally, efficacy of combined protocols was determined. Heat shock 10 min after fertilization induced triploidy when incubation temperature was 24 C but not when incubation temperature was 31 C. Heat shock of 40–41 C at 4–6 min after fertilization was effective in inducing up to 100% triploidy with hatchability similar to controls. Cold shock at 13 C for 45 min five min after fertilization induced 85–100% triploids. Heat shock and multiple heat shocking were the most effective treatments for the induction of tetraploidy. Two heat treatments of 41 C applied at 65 and 80 min after fertilization for 5 min each produced approximately 80% tetraploidy in hatched fry. Immersion of fertilized eggs in cytochalasin A, B, or D at concentrations up to 10 μg/L applied at various times and durations was ineffective in inducing triploidy or tetraploidy.

Journal of the World Aquaculture Society

Nitrite toxicity of Litopenaeus vannamei in water containing low concentrations of sea salt or mixed salts

The uptake, depuration and toxicity of environmental nitrite was characterized in Litopenaeus vannamei exposed in water containing low concentrations of artificial sea salt or mixed salts. In 2 g/L artificial sea salts, nitrite was concentrated in the hemolymph in a dose-dependent and rapid manner (steady-state in about 2 d). When exposed to nitrite in 2 g/L artificial sea salts for 4 d and then moved to a similar environment without added nitrite, complete depuration occurred within a day. Increasing salinity up to 10 g/L decreased uptake of environmental nitrite. Nitrite uptake in environments containing 2 g/L mixed salts (combination of sodium, potassium, calcium and magnesium chlorides) was similar to or lower than rates in 2 g/L artificial sea salt. Toxicity was inversely related to total dissolved salt and chloride concentrations and was highest in 2 g/L artificial sea salt (96-h medial lethal concentration = 8.4 mg/L nitrite-N). Animals that molted during the experiments did not appear to be more susceptible to nitrite than animals that did not molt. The shallow slope of the curve describing the relationship between toxicity and salinity suggests that management of nitrite toxicity in low-salinity shrimp ponds by addition of more salts may not be practical.

Journal of the World Aquaculture Society

Effects of carbon dioxide exposure on intensively cultured rainbow trout Oncorhynchus mykiss: Physiological responses and fillet attributes

Rainbow trout Oncorhynchus mykiss (261.6 × 24.7 g initial weight, mean × SEM) at 13.1 × 0.2 C were exposed for 94 d to one of three CO 2 treatments: control (22.1 × 2.8 mg/L), medium (34.5 × 3.8 mg/L), or high (48.7 × 4.4 mg/L). Trout were checked daily for survival, and fish were sampled at 0, 28, 56, and 84 d for physiological responses, growth, and fillet quality assessments. Trout were also challenged to a 15‐min crowding stress at 93 d to assess their ability to initiate a stress response during hypercapnia. Chronically exposed trout showed nearly 100% survival through 84 d exposure (1 of 1,500 fish died). Growth and physiological results showed that increasing elevated CO 2 , concentrations result in corresponding decreased growth rates and CO 2 specific physiological parameters: The medium and high CO 2 treatments had significantly slower growth and subsequently smaller fish by 84 d. Exposed trout also showed significantly ( P < 0.05) decreased plasma chloride for medium and high CO 2 treatments compared to the control from 28 through 84 d. Decreased growth and smaller fish in the medium and high CO 2 treatments resulted in correspondingly smaller fresh and smoked fillet weights. Chronic CO 2 exposure did not result in notable changes in ultimate muscle pH. Exposure to 15‐min crowding stress at 93 d resulted in significant changes in hematocrit, plasma cortisol, glucose, and chloride for all treatment groups. CO 2 ‐specific changes were detected in hematocrit, plasma cortisol, and plasma chloride responses following the 15‐min crowding stress.

Journal of the World Aquaculture Society

Efficacy of an extract from garlic, Allium sativum, against infection with the furunculosis bacterium, Aeromonas salmonicida, in rainbow trout, Oncorhynchus mykiss

Juvenile rainbow trout, Oncorhynchus mykiss , were fed diets containing 0, 0.5, 1.0, and 2.0% of a garlic extract, challenged with a modified 50% lethal dose of Aeromonas salmonicida and monitored for 28 d. There were significant increases in survival of trout fed 0.5 and 1.0% garlic extract as compared to the control and 2.0% garlic extract groups. A target animal safety study was performed at varying increments using the target dose of 0.5% garlic extract at 0&times; (0% garlic extract), 1&times; (0.5% garlic extract), 3&times; (1.5% garlic extract), and 5&times; (2.5% garlic extract) for 3&times; (6&thinsp;wk) the duration of the original study. There was a significant increase in the level of circulating lymphocytes and a significant decrease in the level of circulating monocytes. The latter correlated to an increased level of pigment-containing macrophage centers within the renal tissue as garlic extract dosing increased, denoting a potential deleterious inflammatory effect as macrophage infiltration became severe at the highest dose. These studies suggest that feeding low-dose (0.5% or 1.0%) garlic extract improves survivability in rainbow trout when challenged with A. salmonicida and appears safe; however, higher levels do not appear to be effective and may cause deleterious effects on health.

Journal of the World Aquaculture Society

In memoriam - William Toshio (Tosh) Yasutake, 1922-2016

William Toshio (Tosh) Yasutake, 1922-2016 passed away peacefully at home on December 12, 2016, at the age of 94. He is survived by Fumi, his wife of 66 years, as well as four children and six grandchildren. With his death, the fish health community has lost an outstanding scientist as well as a kind, unassuming, and wonderful human being. Tosh was born on June 10, 1922, in Seattle, Washington, to Jack and Hide Yasutake. He was in his first year of studies at the University of Washington when Pearl Harbor was attacked by Imperial Japan on December 7, 1941. Following the attack, Tosh and his family (father, mother, sister, and two brothers) were among the 110,000–120,000 people of Japanese ancestry who were forced from their homes on the Pacific coast and incarcerated in internment camps in the interior. In June 1942, Tosh enlisted in the U.S. Army, serving as an unarmed combat medic in the famed 442nd Regimental Combat Team, the most decorated unit for its size and length of service in the history of American warfare. Wounded in October 1944 during the Vosges Mountains campaign near Bruyères, France, Tosh was evacuated and missed the ensuing battle to rescue the “Lost Battalion,” at which his replacement was killed. Tosh returned to action in Italy in February 1945 and served until the end of the war in Europe, earning both a Purple Heart and a Bronze Star for bravery. In October 2010, the Congressional Gold Medal was awarded to the 442nd Regimental Combat Team, and in 2012 the surviving members were made chevaliers of the French Légion d’Honneur for actions contributing to the liberation of France in World War II. After the war, Tosh returned to the University of Washington on the GI Bill and received a B.S. degree in zoology in 1951. In 1953 he began his research career at the U.S. Fish and Wildlife Service’s Western Fish Nutrition Laboratory at Cook, Washington, where he conducted pioneering research on nutritional fish diseases with John Halver. Tosh was one of the first to recognize hepatomas in hatchery-reared Rainbow Trout and helped to trace the disease to an aflatoxin produced by the mold Aspergillus flavis , which grew during the storage of ingredients for fish diets. In 1960, he transferred to the Western Fisheries Research Center (WFRC) in Seattle (then called the Western Fish Disease Laboratory) to start a fish pathology diagnostic laboratory. There he described the histopathology of diseases of economically important fishes, identified etiologic agents, and worked with hatchery biologists to improve the health, quality, and survival of salmonids released from federal and state hatcheries. Tosh was instrumental in recognizing that the viruses of Oregon sockeye disease and Chinook Salmon virus disease were one entity and in giving the disease its present name: infectious hematopoietic necrosis. In recognition of his pioneering research, Tosh was awarded a doctorate in fish pathology by the University of Tokyo in 1980, the first American to have been so honored. In 1983, he published his classic textbook The Microscopic Anatomy of Salmonids: An Atlas , which quickly became a standard reference work in fish pathology and is still in wide use today. For his outstanding career achievements, in 1987 Tosh received the S. F. Snieszko Distinguished Service Award, the highest honor bestowed by the American Fisheries Society’s Fish Health Section (AFS–FHS). Tosh retired in 1988 but continued his research at the WFRC as a senior scientist emeritus, providing technical assistance to federal and state agencies and to the aquaculture industry worldwide. His culminating project was to digitize his lifetime collection of photomicrographs and prepare an atlas, “Histopathology of Selected Parasitic Salmonid Diseases: A Color Atlas,” that is now posted on the Web sites of the WFRC and the AFS–FHS. Although his presence will be sorely missed, his research contributions have become part of the foundation of today’s knowledge of fisheries biology and have assured him a place in history.

Journal of Aquatic Animal Health