摘要:

AbstractThe presence and effects of di‐n‐butylphthalate (DBP) in aquatic environments are reviewed. Particular attention is paid to the use of DBP as a solvent in the pesticide formulation, Aquagard®, used to treat salmonids against external parasites at aquaculture sites in Europe. DBP is sparingly soluble in water, is readily metabolized by fish, and has a high lethal threshold for aquatic organisms. It is, however, lipophilic, persistent in aquatic sediments, and is listed as a priority pollutant by the governments of Canada and United States. The dissemination of this compound directly to water raises several concerns which should be addressed by further research and increased monito

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00203.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWire‐mesh enclosures were used in production ponds to conduct growth trials in which population density and feeding rate were evaluated in a 2 × 2 factorial arrangement for their effects on crawfish growth. JuvenileProcambarus clarkiiof uniform size (0.5 g) were stocked at 2 or 20 animals/m2in experiment 1 and weighed biweekly for 12 wk. Rice forage served as the detrital base, and supplemental feed (25% crude protein) was provided at either a low (26–52 kg/ha per week) or high (104–418 kg/ha per week) rate. In experiment 2, mixed sizes of crawfish were stocked at 10/m2or 20/m2and fed the formulated feed at either 52 or 312 kg/ha per week. Feed consumption was estimated for each treatment combination. Only population density significantly affected crawfish growth. Mean weight gain and final weights were inversely proportional to density but only when total crawfish biomass exceeded 1,235 kg/ha. Growth was not significantly influenced by feeding rate, but the high feeding rate resulted in a significantly greater ratio of hepatopancreas weight to body weight and tended to decrease hepatopancreas moisture levels, indicating improved condition. Population density, feeding rate, and their interaction had significant effects on estimated feed consumption. From the simple linear regression of mean feed consumption on crawfish standing crop, it was estimated that crawfish consume about 0.1 kg of dry feed per ha per week per kg of crawfish biomass on a 5 d per week feeding schedule at mean water temperatures, ranging from 14 t

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00204.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study utilized enclosures (cylindrical, 5‐mm wire mesh, O.5 m2bottom surface area) placed over rice‐forage substrates in experimental crawfish ponds to contain crawfish under typical pond culture conditions. JuvenileProcambarus clarkiiwere stocked at six densities (2, 4, 6, 10, 14, and 18 crawfish/m2) for 12‐wk growth trials in October and again in February. Crawfish relied solely on the detrital food system for their nutritional needs. Supplemental feed was supplied to crawfish in additional enclosures at two of the test densities (2 and 10 crawfish/m2). The commercially formulated feed (25% crude protein) was fed (2.02 g dry feed/m2) 3 d/wk (Monday, Wednesday, Friday). All treatments were replicated with six enclosures. Crawfish growth was inversely correlated to culture density. Mean final weights for crawfish feeding from the detrital‐system only were 15.3, 13.8, 11.2, 7.9, 7.2, and 5.8 g for crawfish densities of 2, 4, 6, 8, 10, 14, and 18/m2, respectively. Mean final weights for crawfish receiving supplemental feed were 20.7 and 12.4 g for densities of 2 and 10 crawfish/m2. When compared with density as a factor influencing growth, feed influenced growth less than density abatement. Supplemental feeding improved crawfish growth in detrital systems an average of 46%, while decreasing initial density improved growth an average o

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00205.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDensity reduction, supplemental feeding, and a combination of two treatments were evaluated as means to alleviate stunting of red swamp crayfishProcambarus clarkiiin earthen ponds. Mean total yield of crayfish in low density control ponds averaged 1,218 kg/ha and was 1.5 to 2 times higher (P≤ 0.05) than either the high density control or treatment ponds. Mean individual harvest weight of crayfish averaged 15.1 g and did not differ among treatments. Mean total yield of crayfish in ponds receiving supplemental feed was 32% higher than non‐fed ponds (P≤ 0.05). Mean total yield and size of crayfish at harvest from reduced and non‐reduced treatments did not differ. Density reduction and supplemental feeding implemented in early April did not increase individual crayfish weight to the commercially desirable size

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00206.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA nursery‐reared population of juvenile freshwater prawns (Macrobrachium rosenbergii) averaging 0.11 ± 0.058 g was size graded through a 4‐mm bar grader producing a numerically 53% upper size population (0.25 ± 0.086 g). These were stocked into triplicate earthen ponds (0.04–0.07 ha each) at densities of 39,540, 59,300 and 79,100/ha, grown for 131 to 134 d, and fed a specially formulated diet. An additional three ponds were stocked at 39,540/ha and fed a commercial sinking catfish feed. Density had a significant effect on average whole body wet weight at harvest but no significant effect on either total yield, survival, or feed conversion. Mean wet weight was significantly higher for prawns stocked at 39,540/ha (34.3 g) than that for those stocked at either 59,300/ha (26.7 g) or 79,100/ha (263 g). The direct relationship between the percentage of small males and increasing density usually seen with ungraded populations was not evidenced in the size‐graded populations. Average total yield ranged from 1,041 to 1,662 kg/ha for stocking densities from 39,540 to 79,100/ha. Differences in overall mean wet weight resulted from differences in mean wet weights for orange claw and no claw males and berried and open females, not from differences in morphotype distributions. These differences resulted in significantly higher percentages of tails within the larger count categories and higher revenues for prawns stocked at 39,540/ha. Feed type had no significant effect. Projected net revenues suggest that prawns need to be marketed and sold as a whol

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00207.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of growth trials was conducted to evaluate the use of soy protein as a replacement for fish protein in isonitrogenous practical diets for juvenile red drumSciacnops ocellatus. Feeds were offered at or in excess of satiation to juvenile red drum maintained at 26–28 C and a salinity of 25–35 ppt. In the first growth trial, red drum were offered one of four diets containing graded levels of menhaden fish meal, replacing solvent‐extracted soybean meal and soy‐protein isolates. Differences in weight gain, survival and feed efficiency ratios of the fish corresponded to increases in fish meal content of the diets. Due to poor performance of the fish maintained on the low (15%) fish meal diet, a methionine supplement was introduced into this diet at the midpoint of the growth trial. A positive increase in growth indicated a dietary deficiency of methionine and/or total sulfur amino acids in the unsupplemented diet. A positive response to dietary fish meal also occurred in the second growth trial despite the supplementation of L‐methionine in the test diets. In low fish meal diets the utilization of solvent extracted soybean meal or a soy‐protein isolate resulted in similar growth responses. Hence, the presence of an antinutrient did not likely cause reduced growth rates. In the third feeding trial, weight gain also increased with increasing fish meal content of the diet despite the equalization of digestible protein and selected amino acids. There were no significant differences in whole‐body compositions which indicated similar biological value of the diets (protein digestibility, amino acid balance and energy availability). The singular deletion of fish‐solubles, glycine, lysine and methionine from the diet containing the lowest level of fish meal (10 g/100 g diet) did not result in significant changes in weight gain. This indicated that these components did not add to the nutritive value and/or palatability of this formulation. The final experiment was designed to evaluate the response of red drum to a control diet (high fish meal) as compared to a low fish meal diet with and without potential attractants/palatability enhancers. Weight gain and feed efficiency ratios of fish offered the low fish meal diet supplemented with seafood flavor or fish flavor #2 were not significantly different from the control (high fish meal diet). Based on the results of this study, with suitable formulation restrictions, soy protein is acceptable for inclusion in practical diet formulations for red drum. However, soy protein itself does not appear replete in sulfur‐containing amino acids and does not have acceptable palatability properties. Consequently, feeds containing reduced levels of marine proteins could require suitable attractants and/or amino

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00208.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractStudies on larval settlement and growth of the commercial scallopAequipecten tehuelchuswere carried out over a 2‐yr period in San Matias Gulf, Argentina. Gonadal index was used to indicate spawning and spat collectors were deployed when spawning began. Artificial spat collectors (mono‐filament bags filled with thin shrub branches) were placed at a depth of 25 m in two areas of the Gulf during two seasons (1989–1990 and 1991–1992). Maximum settlement occurred by mid‐February during the first season and by mid‐January in the second season. Larger numbers of spat were found in collectors placed near the sea bottom. After settlement, spat were removed and placed in cages for growout. Scallops reached the average commercial size (60 mm shell height) 16 mo later. Mortality rate during the entire per

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00209.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractFormalin tolerances of a fluidized‐bed sand biofilter and rainbow troutOncorhynchus mykisswere tested in a semi‐closed freshwater recirculating culture system. Progressively higher formalin levels were tested until fish mortality (±1.9%) occurred. A 1‐h exposure to 167 ppm formalin, followed by flushing, was safe for trout (no mortality) at 15.0 C but not at 16.5 C. A 110‐ppm indefinite treatment (no flushing) was safe at 17.3 C, but 120 ppm at 17.3 C and 100 ppm at 17.8 C were not. Biofilter nitrification was not impaired by 1‐h formdin treatments up to 167 ppm at 16.5 C, and not, usually, by indefinite treatments up to 120 ppm at 17.3 C. However, a find indefinite treatment of 70 ppm was followed by abnormally high nitrite levels for 9 d. Formaldehyde remained detectable in the system for 11 h during indefinite treatment at 120 ppm formalin. Tests on the system's Co2stripper did not indicate that it removed fo

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00210.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractShrimp were grown under ideal management conditions during two distinct seasons of the year at stocking densities used most often in Honduras with the objective of evaluating the usefulness of high protein diets. A randomized design in 2 × 2 factorial arrangement was used to test a diet composed of either 20 or 40% crude protein in earthen ponds that were stocked with juvenilePenaeus vannameiat 5 to 11/m2. The study was repeated during wet and dry seasons. Dietary protein level had no significant effect (P>O.05) on survival, yield, or average weight of shrimp at either density during either season. Higher stocking rates yielded significantly greater shrimp production during both seasons. Mean shrimp weight in high density ponds was significantly lower than mean shrimp weight in low density ponds during the wet season, but there was no significant weight difference because of stocking density during the dry season. Mean survival was significantly lower at the higher stocking rate during the dry season. Net income was negative during the dry season, particularly at the high stocking density. Mean production was 240% greater in the wet season than in the dry season. Diets offeredP. vannameistocked at 5 to 11/m2should contain no more than 20% protein, regardless of season. Higher dietary protein levels increase costs and waste nitrogen without resulting in greater shrimp yields. The high stocking density might increase profitability in the wet season, but long term sustainable production may be more feasible at lower stocking rates because of reduced nutrient wastes

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00211.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0893-8849    

DOI:10.1111/j.1749-7345.1995.tb00212.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY