Whole Body Of Fish Research Articles

Conducting site‐specific assessments of selenium bioaccumulation in aquatic systems

Selenium (Se) is a chemical of concern at many locations across North America and elsewhere, and site-specific conditions are important when evaluating its bioaccumulation and effects in aquatic ecosystems. Most regulatory criteria and guidelines are based on waterborne Se concentrations. In contrast, the draft water quality chronic criterion of the US Environmental Protection Agency (USEPA) is based on Se concentrations in whole-body fish, and current information suggests the agency will issue a new draft criterion based in part on fish egg and/or ovary Se concentrations. However, implementation guidance is not available from the agency for either of these tissue-based criteria. Therefore, we describe a phased approach for field and laboratory assessments of Se bioaccumulation in fish and aquatic-dependent birds that can be applied in different environmental settings with the goal of developing and interpreting a tissue-based Se value. We recommend here the use of decision trees, conceptual models, and data quality objectives toward defining what should be done during the assessment, plus sampling and monitoring procedures for the assessment. First, available tissue or waterborne Se concentrations should be compared to tissue residue guidelines or adopted water quality criteria and guidelines. When needed, reproductive toxicity testing and assessment of fish populations should also be conducted in the area of interest. In addition, extensive data on the effects of Se on fish and bird species have been developed, and describing the associations between fish or bird egg tissue, aqueous Se, and potential effects is important for sites where Se may be a concern. Selenium bioaccumulation and toxicity also are of concern for amphibians and oviparous reptiles, but interpretive information is very limited for those species. Recent science indicates that effects are more strongly related to tissue concentrations of Se (especially in the eggs or ovaries of oviparous vertebrates) than to waterborne concentrations. Overall, we conclude that the approach for site-specific assessment must be flexible enough to allow what is appropriate for the situation. Furthermore, risk management and remediation decisions should be based on combined biology and chemistry data, using multiple lines of evidence in the assessment.

Effects of dietary cadmium exposure on tissue-specific cadmium accumulation, iron status and expression of iron-handling and stress-inducible genes in rainbow trout: Influence of elevated dietary iron

Recent evidences suggest that dietary cadmium (Cd) uptake likely occurs via the dietary iron (Fe) uptake pathway in freshwater fish, at least in part. The present study investigated the interactive effects of dietary Cd and Fe in juvenile rainbow trout ( Oncorhynchus mykiss). Fish were treated for four weeks with four different diets: normal Fe, high Fe, normal Fe plus Cd, and high Fe plus Cd. Physiological parameters, tissue-specific Fe and Cd level, plasma Fe status, and tissue-specific mRNA expression of transferrin, metallothioneins (MT-A and MT-B) and heat shock proteins 70 (HSP70a and HSP70b) were analyzed. Exposure to dietary Cd increased Cd burden in the following order: intestine > kidney > stomach > liver > gill > carcass. Interestingly, high dietary Fe reduced Cd accumulation in the stomach and intestine as well as in the wholebody of fish. Dietary Cd increased hepatic transferrin mRNA expression and total Fe binding capacity in the plasma, indicating the effect of Cd on Fe handling in fish. The mRNA expression of MTs and HSP70s was also increased in various tissues following dietary Cd exposure, however the response profile of different MT and HSP70 genes was not consistent among different tissues. In general, MT-A was more responsive to Cd exposure in the intestine and liver, whereas MT-B was more responsive in the kidney. Similarly, HSP70a expression was more sensitive to Cd exposure than HSP70b, particularly in the intestine. Interestingly, high Fe diet suppressed Cd-induced induction of transferrin, MT and HSP70 genes in various tissues. Overall, our study suggests that elevated dietary Fe can reduce Cd accumulation and ameliorate Cd-induced stress responses in freshwater fish.

Effect of Natural Antioxidant Sources on Oxidation of Olive Flounder (Paralichthys olivaceus) and Fish Feed during Storage

The effects of various natural antioxidant sources on oxidation of olive flounder (Paralichthys olivaceus) and fish diet during storage was determined. Juvenile fish were distributed among 18 flow-through tanks (40 fish per tank). Six experimental diets were prepared in triplicate: control (CT), antitox (AT), green tea extract (GE), fig extract (FE), Haeroc product (HP) and by-product of green tea (BG). The experimental diets were stored at two temperatures: room temperature (<TEX>$26.8^{\circ}C$</TEX>) for 14 days and frozen (<TEX>$-30^{\circ}C$</TEX>) for 16 weeks. Thirty fish were sampled from each tank at the end of the 8-week feeding trial. Whole bodies of fish were homogenized and stored in a home freezer (<TEX>$-9.6^{\circ}C$</TEX>) for 24 weeks. Acid values (AVs) and peroxide values (POVs) of the diets and frozen fish during storage were monitored. AVs of the experimental diets tended to increase with the storage period except for that of the HP diet at room temperature. POVs from FE, CT, and BG diets peaked at day 7 and then decreased through the remainder of the experiment. AVs of the experimental diets and fish increased with time at <TEX>$-30^{\circ}C$</TEX> and <TEX>$-9.6^{\circ}C$</TEX>. Results of this study show that by-products of green tea and Haeroc product seem to have potential as antioxidants in fish feed to inhibit oxidation of both the feed and fish during storage.

배합사료 공급율 및 공급횟수가 겨울철에 사육된 육성기 넙치의 성장 및 체조성에 미치는 영향

Two 15-week feeding trials were conducted to investigate how the rate and frequency of feeding affected the winter growth of olive flounder (<TEX>$13^{\circ}C$</TEX>). In the first experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.0$</TEX> g) were fed extruded pellets twice a day at feeding rates of 0.1, 0.25, 0.4, 0.55, and 0.57% (satiation) body weight per day (BW/d). The weight gain, specific growth rate, and feed efficiency increased significantly (P<0.05) with the feeding rates from 0.1 to 0.55% BW/d, but no significant differences in these parameters were found for fish fed diets of 0.55% BW/d and satiation. The moisture and ash contents of whole body of fish tended to decrease as the feeding rate increased, but the opposite trend was found for crude lipid content. In the second experiment, triplicate groups of fish (initial mean weight <TEX>$117{\pm}6.3$</TEX> g) were fed extruded pellets to apparent satiation at the three different feeding frequencies: one meal 2 days, one meal a day and two meals a day. The weight gain and specific growth rate of fish fed one meal 2 days were significantly (P<0.05) lower than those of fish fed one or two meals a day, whereas no significant differences in the weight gain and specific growth rate were found between fish fed one and those fed two meals a day. Feed efficiency and condition factor were not significantly affected by feeding frequency. Based on these results, a feeding rate of 0.3% BW/d is recommended as maintenance feeding level, and the optimum feeding frequency is one meal a day with satiation feeding for the growth of olive flounder (117-147 g) during winter (<TEX>$13^{\circ}C$</TEX>).

Effect of altering linoleic acid and linolenic acid dietary levels and ratios on the performance and tissue fatty acid profiles of Nile tilapia Oreochromis niloticus fry

This experiment was conducted to study the effect of altering the linoleic acid (LA) and linolenic acid (LNA) levels and ratios in the diet of Nile tilapia (Oreochromis niloticus) on fry performance. Twelve diets were formulated to be isonitrogenous, isocaloric, and differed only in their main lipid source. An oil rich in n-3 fatty acids [linseed oil (L)] and two oils rich in n-6 fatty acids [soybean oil (S) and corn oil (C)] were added at 6% of the basal diet either separately or in equal combinations (L1:S1 or L1:C1 or S1:C1) or at ratio 2:1 (L2:S1 or L2:C1 or C2:L1 or C2:S1 or S2:L1 or S2:C1). The fish were fed twice daily (09 and 16 h) to apparent satiation throughout the duration of the trial (16 weeks). Survival rates increased in a linear pattern with increasing the LA level in the diets (R2 = 0.764). Final body weight was significantly higher in fish fed S, S2:L1, and L2:C1 diets, being 14.29, 14.14, and 14.09 g/fish, respectively. However, tilapia fed C, S1:C1, and C2:S1 diets exhibited low final body weight (11.41, 11.60, and 11.76 g/fish, respectively). The final body weight was negatively affected by increasing the LA/LNA ratios (R2 = 0.647). Either LA or arachidonic acid (%) in the whole body of fish increased in a linear patterns (R2 = 0.641 and 0.746, respectively) with increasing dietary LA. Besides, LNA, eicosapentaenoic, acid and docosahexaenoic acid (%) in the whole body increased in a linear pattern (R2 = 0.777, 0.501, and 0.8148, respectively) the increasing dietary LNA level. The present study indicated that LA/LNA ratio less than 13 is recommended for nutrition of tilapia fry.

Impacts and Pathways of Mine Contaminants to Bull Trout (Salvelinus confluentus) in an Idaho Watershed

Metals contamination from mining activities is a persistent problem affecting aquatic ecosystems throughout mining districts in the western USA. The Gold Creek drainage in northern Idaho has a history of mining within its headwaters and contains elevated sediment concentrations of As, Cd, Cu, Pb, and Zn. To determine system-wide impacts of increased metals, we measured concentrations of metals in water, sediment, and benthic macroinvertebrate tissues and related them to whole-body fish tissues and histopathological alterations in native salmonids. Water concentrations were higher than those in reference areas, but were below water quality criteria for protection of aquatic biota for most of the study area. Sediment and benthic macroinvertebrate tissue concentrations for all metals were significantly higher at all sites compared with the reference site. Fish tissues were significantly higher for all metals below mine sites compared with the reference site, but only Cd and Pb were higher in fish tissues in the furthest downstream reach in the Gold Creek Delta. Metals concentrations in benthic macroinvertebrate tissues and fish tissues were strongly correlated, suggesting a transfer of metals through a dietary pathway. The concentrations within sediments and biota were similar to those reported in other studies in which adverse effects to salmonids occurred. We observed histopathological changes in livers of bull trout, including inflammation, necrosis, and pleomorphism. Our study is consistent with other work in which sediment-driven exposure can transfer up the food chain and may cause adverse impacts to higher organisms.

Compensatory Growth of Olive Flounder, Paralichthys olivaceus, Fed the Extruded Pellet with Different Feeding Regimes

Abstract This study was performed to determine compensatory growth of juvenile olive flounder fed the extruded pellet (EP) with different feeding regimes. Seven treatments with triplicates of different feeding regimes were prepared; α fish was daily fed for 6 d a week throughout 8 wk (8WF); α fish was starved for 1 wk and then fed for 3 wk twice [(1WS + 3WF) × 2]; β fish was starved for 2 wk and then fed for 6 wk (2WS + 6WF); χ fish was starved for 5 d and then fed for 9 d four times [(5DS + 9DF) × 4]; δ fish was starved for 10 d and then fed for 18 d twice [(10DS + 18DF) × 2]; δ fish was starved for 2 d, fed for 5 d, starved for 3 d, and then fed for 4 d four times [(2DS + 5DF + 3DS + 4DF) × 4]; and φ fish was starved for 4 d, fed for 10 d, starved for 6 d, and then fed for 8 d twice [(4DS + 10DF + 6DS + 8DF) × 2], respectively. Total feeding day was all same, 36 d except for control group (48 d). Weight gain of flounder in the 8WF treatment was higher than that of fish in other treatments. And weight gain of flounder in the 2WS + 6WF treatment was higher than that of fish in the (5DS + 9DF) × 4 and (4DS + 10DF + 6DS + 8DF) × 2 treatments. Feed consumption of flounder in the 8WF treatment was higher than that of fish experienced feed deprivation. Feed efficiency ratio (FER), protein efficiency ratio (PER), and protein retention (PR) were not significantly different among treatments. Chemical composition of the whole body of fish with and without liver, except for moisture content of liver, was not different among treatments. T3 level of fish in the 8WF and 2WS + 6WF treatments was higher than that of fish in the (5DS + 9DF) × 4 treatment. It can be concluded that juvenile olive flounder achieved better compensatory growth at 6‐wk refeeding after 2‐wk feed deprivation compared with that of fish with different feeding regimes. And T3 level of fish seemed to partially play an important role in achieving compensatory growth.

Trace element and stable isotope analyses of deep sea fish from the Sulu sea, Philippines

Thirty-five deep sea fishes belonging to 22 species and one unidentified specimen obtained from the Sulu Sea, located in the southwestern area of the Philippines were analyzed in the late 2002, for 23 trace elements using ICP-MS, HGAAS and CV-AAS. Predominant accumulation of strontium (Sr) was observed in all the samples. This stems from the fact that the whole body of fish was homogenized since Sr is known to accumulate in bones and hard tissues. Mercury concentrations in all the 36 samples were below the detection limit. Cadmium concentrations were generally below 1ìg/g dry weight (dw) except in Pterygotrigla spp. (4.29 ìg/g dw) and Sternoptyx pseudodiaphana (2.89 ìg/g dw). Concentrations of Pb were predominantly low with about 90% of the specimens having less than 1 ìg/g dw. In general, concentrations of Sr, Zn, Cu, Se and Cd appeared to increase with increasing depth of occurrence of the species.Manganese, Tl, Pb, Bi, In, Cs and As showed significant positive correlation (p < 0.05) with d15N, suggesting that these elements were biomagnified. To our knowledge, this is the first study reporting Tl biomagnification in fish. Rubidium and Cs showed significant positive correlation with d13C, implying that Rb and Cs would originate from offshore waters as oceanic plankton has high d13C. Comparing results from this study to the dietary standards and guidelines for Hg, Pb, Cu and Zn in fish and shellfish of the Ministry of Agriculture, Fisheries and Food of the United Kingdom,these levels were not high to warrant concern if they were to be consumed by humans. However, 16.7% of the fish samples had high Cr levels when compared with the Hong Kong’s safe limit of 4 ìg/g dw for Cr in sea food. This constitutes a health risk to humans, as Cr is potentially toxic.

An evaluation of selenium concentrations in water, sediment, invertebrates, and fish from the Solomon River Basin

The Solomon River Basin is located in north-central Kansas in an area underlain by marine geologic shales. Selenium is an indigenous constituent of these shales and is readily leached into the surrounding groundwater. Portions of the Basin are irrigated primarily through the pumping of selenium-contaminated groundwater from wells onto fields in agricultural production. Water, sediment, macroinvertebrates, and fish were collected from various sites in the Basin in 1998 and analyzed for selenium. Selenium concentrations were analyzed spatially and temporally and compared to reported selenium toxic effect thresholds for specific ecosystem components: water, sediments, food-chain organisms, and wholebody fish. A selenium aquatic hazard assessment for the Basin was determined based on protocol established by Lemly. Throughout the Basin, water, macroinvertebrate, and whole fish samples exceeded levels suspected of causing reproductive impairment in fish. Population structures of several fish species implied that successful reproduction was occurring; however, the influence of immigration of fish from low-selenium habitats could not be discounted. Site-specific fish reproduction studies are needed to determine the true impact of selenium on fishery resources in the Basin.

Contaminant concentrations in whole-body fish and shellfish from US estuaries

Persistent bioaccumulative and toxic (PBT) pollutants are chemical contaminants that pose risks to ecosystems and human health. For these reasons, available tissue contaminant data from the US EPA Environmental Monitoring and Assessment Program's National Coastal Assessment were examined to estimate to what areal extent PBTs are found in US estuarine resources. The data document composite, whole-body tissue chemical concentrations for 736 sampling sites across Northeast, Southeast, Gulf of Mexico, and West Coast estuaries. Tissue chemical concentrations were compared to US EPA non-cancer risk guidelines for recreational fishers, because of a lack of ecological guidelines for these chemical concentrations. Samples were analyzed for 23 PAH compounds, 21 PCB congeners, 6 DDT derivatives and metabolites, 14 chlorinated pesticides (other than DDT) and 13 metals, including mercury. Total PCBs were found to exceed recreational fisher guidelines most frequently (31% of samples evaluated), followed by mercury (29%), total PAHs (21%), and DDT and its metabolites, DDD and DDE (11%). Toxaphene, cadmium and dieldrin were found but in fewer than 1% of the samples.

Diet–Feather Stable Isotope (δ15N and δ13C) Fractionation in Common Murres and Other Seabirds

Abstract We measured the fractionation of stable nitrogen (δ15N) and carbon (δ13C) isotopes in the breast and primary feathers of 11 Common Murres (Uria aalge) maintained on a diet of capelin (Mallotus villosus). Diet–feather δ15N fractionation from delipidated capelin muscle to murre feathers was 3.6‰ ± 0.2‰ in breast feathers and 3.7‰ ± 0.2‰ in primary feathers. Fractionation of δ13C was 2.5‰ ± 0.2‰ in breast feathers and 1.9‰ ± 0.3‰ in primary feathers. Prey–feather fractionation (for delipidated, muscle-only prey samples) for nine other species of seabirds ranged from 3.0‰ to 4.6‰ for δ15N and 0.1‰ to 2.5‰ for δ13C. Studies that did not remove lipids from prey samples showed higher δ15N and δ13C fractionation, and those that used whole prey items rather than muscle tissue alone showed higher δ15N fractionation. We suggest that: (1) prey samples be delipidated to facilitate interpretation of δ13C fractionation, (2) high interstudy and interspecific variation in δ13C makes species-specific studies essential, and (3) use of muscle tissue rather than whole bodies of fish will minimize unexplained variation in δ15N fractionation.

A PBTK/TD modeling‐based approach can assess arsenic bioaccumulation in farmed tilapia (Oreochromis mossambicus) and human health risks

A biologically based risk-assessment model of arsenic (As) exposure evaluated farmed tilapia (Orechromis mossambicus) and human health during tilapia consumption in an area of southwestern Taiwan where blackfoot disease (BFD) occurs. The risk assessment addressed exposures to city residents who lived in Taipei, Taichung, and Kaohsiung, as well as subsistence fishers living in the BFD area who consumed tilapia. The models implemented included a physiologically based toxicokinetic and toxicodynamic (PBTK/TD) model to account for As exposure and dose-response profiles in tilapia and a human health exposure/risk model that accounts for target lifetime risk (TR) and hazard quotient (HQ) for humans consuming farmed tilapia. Results demonstrated that 90th percentiles of TR ranged from 1.53 x 10(-8) to 1.62 x 10(-6) for city residents with farmed tilapia consumption rates of 0.41 to 1.37 g/d. The 90th percentiles ranged from 2.07 x 10(-6) to 7.89 x 10(-5) for subsistence fishers in the BFD area with farmed tilapia consumption rates of 16.80 to 59.15 g/d. All predicted 90th percentiles of HQ were less than 1 for city residents and subsistence fishers in the BFD area, indicating small contributions from farmed tilapia consumption. Critical variables included whole-fish body weight, water As content, and As level in tilapia muscle. Although bioaccumulation of As seems unlikely to result in toxicity to farmed tilapia and humans consuming tilapia, the theoretical human health risks in the BFD area are alarming, using a probabilistic risk-assessment model based on conservative assumptions.

Review of residue-based selenium toxicity thresholds for freshwater fish

A variety of guidelines have been proposed in recent years for linking selenium concentrations in the whole body of fish or in diet with adverse effects in fish. Diverging viewpoints seem to be forming separating groups supporting either the low-selenium guidelines proposed by the government and academic researchers or the high-selenium guidelines proposed by other researchers. Recently, an article was published that reviewed selected studies and recommended guidelines for selenium concentrations in the whole body of fish and in diet that were higher than those proposed by other researchers (≈4 μg/g in whole body and 3–4 μg/g in diet). That article also recommended separating guidelines for coldwater fish (6 μg/g in whole body and 11 μg/g in diet) and warmwater fish (9 μg/g in whole body and 10 μg/g in diet). The approaches, information, and guidelines presented in the article are reviewed and problems in their interpretation and conclusions are discussed. The majority of the selenium literature supports a whole-body threshold of 4 μg/g in fish and 3 μg/g in diet.

Effect of Dietary Sargassum Meal on Growth and Body Composition of Ayu (Plecoglossus altivelis) Reared in Seawater

This study was conducted to investigate the utilization of Sargassum meal in the diet on juvenile ayu (Plecoglossus altivelis) reared in seawater. White fish meal and wheat flour were used as the dietary protein and carbohydrate sources in the control diet. Wheat flour in the control diet was replaced with and Sargassum meal. Three replicate groups of fish average weighing 4.0 g were fed one of three isonitrogenous and isocaloric (14.5 MJ /kg diet) diets for 7 weeks. Survival of all groups were above . Weight gain, feed efficiency and protein efficiency ratio were not significantly affected by dietary Sargassum meal levels (P>0.05). There were no significant differences (P>0.05) in moisture, crude protein, crude lipid, crude ash and fatty acid compositions of whole-body fish among groups. It is concluded that Sargassum meal could be used as a dietary additive or alternative low-cost dietary ingredient up to for juvenile ayu reared in seawater.

Exigência Protéica e Relação Energia/Proteína para Alevinos de Piracanjuba (Brycon orbignyanus)

O objetivo do presente estudo foi determinar a exigência protéica e correspondente relação energia/proteína em dietas para alevinos de piracanjuba, Brycon orbignyanus. Seis dietas semi-purificadas isocalóricas foram formuladas para conter 3.000 kcal de energia metabolizável (EM)/kg e concentrações de proteína bruta (PB) de 24, 26, 29, 32, 36 e 42%. Para essas concentrações, as relações E/P das dietas foram de 12,3; 11,6; 10,4; 9,2; 8,5 e 7,1 kcal EM/g PB, respectivamente. As fontes de proteína, lipídios e carboidratos digestíveis foram, respectivamente, caseína/gelatina, óleo de fígado de bacalhau/óleo de soja e dextrina. Após condicionamento de cinco dias, as dietas foram fornecidas, até a saciedade, em duas alimentações diárias, a 162 alevinos (27 peixes/dieta), que apresentaram 8,38 ± 0,09 g de peso médio inicial, distribuídos em 18 tanques de fibra-de-vidro de 100 L, conectados a um sistema de recirculação de água. A temperatura média da água foi de 26,3°C, com extremos de 23,7 e 30,2°C. Após 90 dias, a concentração de proteína na dieta que proporcionou ganho em peso máximo aos peixes foi 29% PB, com relação E/P igual a 10,4 kcal EM/g PB. As dietas com concentrações de PB iguais a 32, 36 e 42% não se mostraram superiores para conversão alimentar, taxa de eficiência protéica, valor produtivo da proteína e retenção de energia bruta. A deposição corporal de proteína e gordura não sofreu influência da concentração de PB da dieta

Effects of variable feed allowance with constant energy and ratio of energy to protein in a diet for constant protein input on the growth of common carp Cyprinus carpio L.

An 11-week feeding trial was conducted to evaluate the effects of dietary protein and/or energy levels on growth, feed efficiency and proximate composition of juvenile (average weight: 21.5 g) common carp (Cyprinus carpio L.) fed various diets based on constant daily protein input. Five experimental diets were prepared. One group of diets (diets 1, 2 and 3) contained three crude protein (P) levels (35%, 40% and 45%) with a constant gross energy (GE) of 3.8 kcal g−1 diet. The second group of diets (diets 4 and 5) were formulated to contain a GE of 4.3 or 4.9 kcal g−1 diet and 40% or 45% protein levels, respectively, where GE/P was constant at 10.8 kcal g−1 protein. Fish receiving diet 1 served as the control; they were hand-fed to visual satiety. Feed allowance for diets 2 and 4 was 87.5% of the control. Feed allowance for fish receiving diets 3 and 5 was 77.8% of the control. Thus, all tanks received the same daily protein input. When gross energy in the diets was constant, 3.8 kcal g−1 diet, weight gain of fish fed diet 2 at 87.5% satiation was significantly higher than that of fish fed diet 3 at 77.8% of satiation. When the GE/P in the diets was constant, 10.8 kcal g−1 protein, weight gain of fish fed diet 1 was significantly higher than that of fish fed diet 5 at 77.8% satiation. The feed efficiency ratio (FER) for diets 2–5 was significantly higher than for diet 1 at constant GE and GE/P, and this improved linearly as dietary protein levels increased. The protein efficiency ratio (PER) for diet 2 was significantly higher than for diet 3 at constant GE. However, PER was not significantly different at constant GE/P. Protein retention of fish fed diet 2 was significantly higher than that of fish fed diet 3 at constant GE. Protein retention of fish linearly decreased at constant GE/P. The energy efficiency ratios (EER) for diets 2 and 3 were significantly higher than for diet 1 at constant GE. Moisture and protein contents of the whole body of fish were not significantly different at constant GE, but they decreased linearly at constant GE/P. The lipid content of fish fed diet 1 was significantly lower than that of fish fed diet 2 at constant GE, and body lipid content linearly increased at constant GE/P. These results indicate that growth and feed efficiency for common carp fed a 40% protein diet with 3.8 kcal g−1 diet GE at 87.5% satiation rate was superior to those for the fish fed either a 35% protein diet with 3.8 kcal g−1 diet GE at 100% satiation rate or a 45% protein diet with either a 3.8 or 4.9 kcal g−1 diet GE at 77.8% satiation rate.

A mechanistic model for the uptake of waterborne strontium in the common carp (Cyprinus carpio L.).

The release of radioactive strontium to the environment is of concern due to the strong accumulation of this calcium resembling element in the bone and other tissues. To predict the effects of changes in environmental conditions on the uptake of Sr2+ and Ca2+ by freshwater fish, a Michaelis-Menten type model is introduced that accounts for the effects of chemical speciation, hydrogen ion activity, and metal ion competition. The uptake kinetics were characterized in vivo from short-term exposure experiments using the common carp (Cyprinus carpio) as the model organism. Fish were exposed to a wide range of waterborne Sr2+ (0.2-10,000 microM) and Ca2+ (10-10,000 microM) concentrations and water pH (5.0-8.5). Strontium uptake by the whole body of fish increased with increasing Sr2+ activity, displaying saturation kinetics, but decreased significantly with increasing Ca2+ and H+ activities in the water. Likewise, calcium uptake by the fish decreased with increasing Sr2+ and H+ activities in the water. The model fitted to the pooled data explains 97.5% of the variation in Sr2+ uptake and 86% in Ca2+ uptake over the wide range of exposure conditions and reveals that Sr2+ and Ca2+ inhibit each other completely competitively, while H+ inhibits the uptake of both metal ions in a partially noncompetitive way. This model can be used as a mechanistic tool to predict the uptake of these metals in carp under variable conditions.

Pond culture of female green sunfish ( Lepomis cyanellus) × male bluegill ( L. macrochirus) hybrids stocked at two sizes and densities

The hybrid produced by crossing the female green sunfish ( Lepomis cyanellus) and male bluegill ( L. macrochirus) was evaluated under production conditions for 1 year. Juveniles were stocked at two initial sizes (38 and 66 g) and two densities (6175 and 12350/ha) into twelve 0.04-ha ponds and fed a diet containing 36% protein for 371 days. Fish stocked at 6175/ha had significantly higher ( P < 0.05) final weights and average total and summer gains than fish stocked at 12350/ha. Although fish stocked at 38 g were significantly smaller ( P < 0.05) at harvest, percentage weight gain and feed conversion efficiencies were significantly higher ( P < 0.05) than for fish stocked at 66 g. There was a significant interaction ( P < 0.05) between stocking density and stocking size on net yield and gross yield which ranged from 838 and 1315 kg/ha, respectively for small fish stocked at low density to 1925 and 3565 kg, respectively for large fish stocked at high density. There were no significant differences ( P > 0.05) in percent protein, fat, and moisture of whole bodies of fish stocked in the different treatments. Stocking of large juveniles at high density produced more harvestable-size fish (> 110 g) per ha. Effects of higher stocking densities on feed utilization and improved feeding regimes should be investigated.

Effect of Dietary .ALPHA.- and .BETA.-Starch on Growth of Juvenile Striped Jack and Yellowtail.

This experiment was conducted to investigate the availability of dietary gelatinized starch (α-) and raw starch (β-) as an energy source in diet for juvenile striped jack and yellowtail. Both fish were fed three kinds of diets containing either 10% α- or β-starch, and a mixture of both starch at 5% each. The gelatinized ratio (GR) of these diets was 100, 16.6, and 50.0%, respectively. The highest daily feed consumption was observed in fish fed the diet containing 10% β-starch in both experiments. This value was decreased when the content of α-starch in diet increased. The fish fed the diet containing 10% β-starch in both experiments showed the lowest percent gain, feed efficiency, and PER. Crude lipid contents in whole body of fish fed diets containing 10% β-starch alone were lowest among the treatments in both experiments. These results indicated that a supplement of β-starch alone as a dietary carbohydrate source is not effectively utilized for growth of striped jack and yellowtail. On the other hand, good performances were observed in fish fed the diet containing 10% α-starch and a mixture of both starch at 5% each. Thus, these results suggested that the GR of diet for both striped jack and yellowtail should be above 50% in order to achieve better growth performances, at least half of dietary carbohydrate must be α-starch at a supplemental level of 10%.

Bioconcentration and excretion of diazinon, IBP, malathion and fenitrothion by willow shiner

Bioconcentration and excretion of diazinon (diethyl 2‐isopropyl‐4‐methyl‐6‐pyrimidinyl phosphorothionate), IBP (S‐benzyl diisopropyl phosphorothiolate), malathion (S‐1,2‐bis(ethoxycarbonyl)ethyl dimethyl phosphorothiolothionate) and fenitrothion (dimethyl 4‐nitro‐m‐tolyl phosphorothionate) was studied for the fresh‐water fish, willow shiner (Gnathopogon caerulescens). The concentrations of these pesticides in whole body of fish reached plateaus in 6–48 h exposure (IBP 6h, fenitrothion and malathion 24 h, diazinon 48 h). The average values of bioconcentration factors (BCF) in whole body of fish were 33.2 for IBP, 398.5 for fenitrothion, 34.4 for malathion and 247.9 for diazinon through the 168 h exposure period. The excretion rate constants from whole body offish were 0.07b‐1 for diazinon, 0.07b‐1 for fenitrothion and 0.49h‐1 for malathion assuming their processes to be first‐order kinetics. For IBP, the rate constant was 0.0017gng‐lh‐1 assuming the process to be second‐order kinetics.