Fish Wet Weight Research Articles

Assessment of zootechnical parameters, intestinal digestive enzymes, haemato-immune responses, and hepatic antioxidant status of Pangasianodon hypophthalmus fingerlings reared under different stocking densities

A 3-month experiment was designed to investigate the effects of different stocking densities on growth, stress markers, intestinal digestive enzymes, hepatic antioxidant biomarkers, serum immunity, and survivability of striped catfish, Pangasianodon hypophthalmus. The relationship between fish stocking densities and water quality parameters was also assessed. Healthy fish (n = 1260 individuals, 17.52 ± 0.20 g) were raised in twelve fiberglass tanks. Triplicate fish groups with stocking densities of 60, 90, 120, or 150 fish per 1 m3 were designed, further referred to as SD60, SD90, SD120, and SD150 groups. Fish feeding was done using a commercially purchased well-balanced diet three times per day with a feeding rate of 3% of the wet fish weight. Results revealed that un-ionized ammonia, nitrite, and pH were significantly elevated, and dissolved oxygen levels were decreased significantly with increasing the stocking densities. The survival rates and growth significantly decreased with increasing fish stocking densities. The intestinal lipase, protease, trypsin, and amylase enzymes decreased significantly (P < 0.05) along with increased stocking densities. Moreover, significant decreases were noticed in total protein, lysozyme activity, and globulin levels when the stocking density was higher than 60 fish/m3. Conversely, serum stress biomarkers (such as blood glucose and cortisol), transaminases, alkaline phosphatase, and blood urea nitrogen were significantly elevated with increasing stocking densities. Hepatic CAT, SOD, and T-AOC were decreased; meanwhile, hepatic MDA levels were significantly increased, together with the stocking rates. In the end, we found that the SD150 group recorded the lowest growth rates, immune responses, and antioxidant capacity and the highest stress markers as blood glucose and cortisol. In this context, we can conclude that the stocking 60 fish/m3 resulted in better growth, survival, immunity, antioxidant status, and overall performances of striped catfish.Graphical

Occurrence, behavior and the associated health risk of organochlorine pesticides in sediments and fish from Bahía Blanca Estuary, Argentina.

Organochlorine pesticides (OCPs) were assessed for their occurrence, behavior and the associated human health and ecological risks in four fish species (Micropogonias furnieri, Cynoscion guatucupa, Mustelus schmitti, and Ramnogaster arcuata) and sediments from the Bahía Blanca estuary, Argentina, an important coastal environment of South America. Total OCPs values ranged from 0.86 to 6.23ng/g dry weight in sediments and from <LOD (method detection limits) to 0.74ng/g wet weight in fish. While lindane and α-endosulfan were the dominant congeners in sediments, β-endosulfan and p,p'-DDE were dominant in fish. OCP levels and residues patterns varied within the fish species and life stage. Finally, after cancer and non-cancer risk analysis, results concluded that the consumption of fish from the estuary would pose no health threats associated with these pollutants.

Impact of feed with varying crude protein (CP) levels on growth performance of different fish species cultured under similar regimes

Fish polyculture has resulted in high fish production per unit area, mainly due to the best utilization of all kinds of nutrients. In this nine month’s experimental study, five different fish species were stocked in five earthen ponds designated as control (one pond), treatment-T1 (two ponds) and treatment-T2 (two ponds). Fish stocked in T1 and T2 ponds were fed with a commercial feed containing 20% and 25% crude protein, respectively, whereas fish stocked in the control pond was fed with a conventional mixture of feed ingredients (fish meal, gluten, sunflower, and rice polish) having 20% CP. The fish was fed @ 3% of the fish wet body weight twice a day. The fish was sampled every fortnight. Physicochemical parameters of the ponds were measured daily. The results showed that the maximum weight gain (255 g) was recorded in Pangasius pangasius in treatment T2 and minimum (52.5 g) in Cirrhinus mrigala in the control pond. Overall, maximum fish production was recorded after harvest in treatment T2 followed by that in treatment T1 and control ponds, respectively. Overall, the commercial fish feed enriched with crude protein was very effective in promoting growth and development of pond fish.

Effects of Frozen Storage on Fish Wet Weight, Percent Dry Weight, and Length Revisited

AbstractFrozen storage can affect the physical characteristics of biological samples, and the effects can vary based on the frozen storage method that is used. We compared four frozen storage treatments: (1) flash frozen in liquid nitrogen (LN2) and stored at −20°C, (2) flash frozen in LN2 and stored at −65°C, (3) frozen in a saline solution (0.9% NaCl) and stored at −20°C, and (4) glazed with deionized (DI) water and stored at −20°C, to investigate the effects of frozen storage on wet weight, percent dry weight, and length of Mummichogs Fundulus heteroclitus. Mummichog wet weights differed from Prestorage wet weights for all treatments. Postthaw wet weight increased from the Prestorage wet weight for Mummichogs that were frozen in a saline solution (3–5% for 4–12 g fish). Conversely, Postthaw wet weight decreased from Prestorage wet weight (1–4% for 4–12 g fish) for Mummichogs that were frozen with LN2 and stored at −20°C or −65°C and Mummichogs that were glazed with deionized water and stored at −20°C. Subsequently, percent dry weight was underestimated by 0.77% for the Mummichogs that were frozen in a saline solution and overestimated for those that were frozen with LN2 and stored at −20°C (0.94%) or −65°C (0.60%) and those that were glazed with deionized water and stored at −20°C (0.71%). Fish total length decreased 2–3% after the samples had been frozen, and they did not differ among the four treatments. When possible, fish that are stored frozen should be measured and weighed alive or immediately after being euthanized, and if this is not possible, we suggest glazing the fish with water and developing correction factors for water loss and shrinkage.

Use of occupancy modelling to identify sample sizes and waterbodies with fish exceeding mercury consumption advisory thresholds.

Identifying waterbodies where fish methylmercury concentrations are elevated is critical for development of consumption guidelines. However, mercury concentrations vary among waterbodies and fishes due to a suite of environmental conditions and detection of elevated mercury concentrations is imperfect, resulting in inaccurate consumption guidelines. Occupancy models may be a useful approach for addressing these issues but have not been used for these purposes. Our objectives were to use occupancy modeling to (1) estimate number of samples needed to detect mercury levels surpassing >0.30 mg/kg wet weight in fish at a waterbody (2) identify individual fish-level factors associated with detection probability, and (3) identify environmental-level factors linked to elevated mercury levels in fish at a waterbody. Mercury concentrations were estimated from >500 largemouth bass Micropterus salmoides and walleye Sander vitreus from 30 waterbodies throughout Iowa, USA to identify individuals with concentrations > or <0.30 mg/kg. Probability of detecting mercury concentrations >0.30 mg/kg varied between species and increased with fish length; consequently, more samples were needed to detect elevated mercury concentrations in small versus large fish. The probability of a waterbody having fish with elevated mercury levels increased with the percent grassland and declined with percent agriculture in the watershed, providing prioritization metrics for mercury surveillance programs. Our results demonstrate that occupancy models can be a valuable tool for mercury surveillance due to their ability to estimate necessary sample sizes and identify fish sizes and waterbodies with elevated mercury concentrations while accounting for imperfect detection probabilities.

Flow field-induced drag forces and swimming behavior of three benthic fish species

Modern ethohydraulics is the study of the behavioral responses of swimming fish to flow fields. However, the exact drag forces experienced by fish remain poorly studied; this information is required to obtain a better understanding of the behavioral responses of fish and their current resistance strategies. We measured near-ground frontal drag forces on preserved individuals of three benthic fish species, round goby (Neogobius melanstomus), gudgeon (Gobio gobio) and bullhead (Cottus gobio), in a flow channel. The forces were compared to acoustic Doppler velocity (ADV) measurements and fish tracking data based on video observations of live fish in the flow channel. Overall, we observed drag coefficients (CD) of ∼10−3 at Reynolds numbers ∼105. The frontal drag forces acting on preserved fish with non-spread fins ranged from -1.96 mN*g-1 (force per fish wet weight, velocity 0.55 m*s-1) to 11.01 mN*g-1 (velocity 0.85 m*s-1). Spreading the fins strongly increased the drag forces for bullhead and round goby. In contrast, the drag forces were similar for gudgeon with spread fins and all fish with non-spread fins. Video tracking revealed no clear relationship between the position of the fish in the flow field and the forces experienced by the preserved fish at these positions. Collectively, these results suggest that i) the differences in frontal drag forces between species are small in homogenous flow, ii) individuals chose their position in the flow field based on factors other than the drag forces experienced, and iii) whether fins are spread or non-spread is an essential quality that modulates species-specific differences. The methodology and results of this study will enable integration of flow measurements, fish behavior and force measurements and inform ethohydraulics research. More advanced force measurements will lead to a detailed understanding of the current resistance strategies of benthic fish and improve the design of fish passes.

Microplastic content of Kutum fish, Rutilus frisii kutum in the southern Caspian Sea

The occurrence of microplastics (MPs) in the digestive tract of commercial Kutum fish, Rutilus frisii kutum was investigated. Fish samples, ranging from 33 to 48.5 cm fork length which sold for human consumption, were collected from local fish markets in Bandar-e Torkaman (the south-eastern of Caspian Sea) on November 2017, and March 2018. The MPs were characterized using optical microscopy, NR staining, and SEM-EDS for number, shape, color, surface morphology, and elemental composition. On average, 11.4 MP items per fish (0.015 items per 1 g fish wet weight) were found in Kutum's stomach at an individual detection rate of 80%. Around 66% of all identified MP items were < 500 μm, and 53% possessed light colors. Morphological researches indicated that fish ingested the degradation fragments from larger plastic pieces, fibers, and manufactured microbeads. Microfibers are the most dominant items accounting for over 75% of all MPs. The SEM images indicated the various degrees of erosions upon environmental exposure. Some MPs had surface cracks, broken margins, scaly appearances, and obvious pores. Considering the commercial importance which the Kutum plays for Iran's fishery, the potential effect of MPs on the trophic food web, particularly for human consumption and health, should be urgently investigated.

Multi-box mass balance model of PFOA and PFOS in different regions of San Francisco Bay

We present a model to predict the long-term distribution and concentrations of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in estuaries comprising multiple intercommunicated sub-embayments. To that end, a mass balance model including rate constants and time-varying water inputs was designed to calculate levels of these compounds in water and sediment for every sub-embayment. Subsequently, outflows and tidal water exchanges were used to interconnect the different regions of the estuary. To calculate plausible risks to population, outputs of the model were used as inputs in a previously designed model to simulate concentrations of PFOA and PFOS in a sport fish species (Cymatogaster aggregata). The performance of the model was evaluated by applying it to the specific case of San Francisco Bay, (California, USA), using 2009 sediment and water sampled concentrations of PFOA and PFOS in North, Central and South regions. Concentrations of these compounds in the Bay displayed exponential decreasing trends, but with different shapes depending on region, compound, and compartment assessed. Nearly stable PFOA concentrations were reached after 50 years, while PFOS needed close to 500 years to stabilize in sediment and fish. Afterwards, concentrations stabilize between 4 and 23 pg/g in sediment, between 0.02 and 44 pg/L in water, and between 7 and 104 pg/g wet weight in fish, depending on compound and region. South Bay had the greatest final concentrations of pollutants, regardless of compartment. Fish consumption is safe for most scenarios, but due to model uncertainty, limitations in monthly intake could be established for North and South Bay catches.

Indirect effect of different dietary protein to energy ratio of bait fish mori diets on growth performance, body composition, nitrogen metabolism and relative AMPK & mTOR pathway gene expression of Chinese perch

Chinese perch (Siniperca chuatsi) is an important economic freshwater carnivorous fish. Commonly feeds on other live fish or bait fish, and accept an artificial diet only after standard training. The feeding habit of Chinese perch caused high aquaculture costs and consumer prices. However, only a few studies are conducted on Chinese perch live feed (bait fish) or live feed (mori) feeds. Therefore, the present study was conducted to investigate the effect of live feed (mori) and live feed (mori) feeds protein to energy ratio on Chinese perch. Three Iso-energetic diets (16 kJ/g) with graded levels of P/E ratios (19.79, 22.19 and 24.46 mg protein/kJ) each with a protein level of 28.18 %, 31.36 %, and 33.91 % (named A, B, and C) were formulated. Two separate experimental tanks systems were used. In one tanks system, a total of 90 kg live bait fish C. mrigala were distributed into three groups (triplicate tanks (1000 L) for each group) and fed with respective P/E ratio diets. In another tanks system, a total of 270 Chinese perch (30 fish/tank) were divided into three groups (triplicate tanks for each group), distributed into 9 (1000-L) fiberglass tanks and fed with assigned live bait fish at 4 % fish wet body weight, twice a day for 8 weeks. The results showed that P/E ratio in bait fish diets significantly affected bait fish and Chinese perch growth performance, feed utilization, body composition, nitrogen metabolism, protein synthesis, and energy homeostasis. Bait fish in Group A showed significantly lower weight gain (WG), specific growth rate (SGR), and higher Viscerosomatic index (VSI) and Hepatosomatic index (HSI) as compared to other groups. Correspondingly, bait fish in Group A showed significantly low whole-body crude protein and high lipid contents as compared to other groups. Similarly, Chinese perch in Group A, showed significantly lower WG, SGR, protein efficiency ratio (PER) and highest feed intake (FI), feed conversion ratio (FCR), VSI, HSI, and Intraperitoneal fat (IPF), as compared to other groups. Furthermore, Chinese perch in Group A, showed significantly lower whole body and muscle crude protein, and higher lipid contents as compared to other groups. Similarly, the nitrogen metabolism enzyme activities (ALT, AST, GDH, AMPD) and gene expression of GDH and AMPD in Group A of Chinese perch, were significantly lower than other groups. Moreover, the AMPK and mTOR pathways gene expression showed a low energy status and protein catabolism in Group A of Chinese perch as compared to other groups. From our results, we conclude that the P/E ratio in bait fish diet significantly affected bait fish and Chinese perch growth performance and nutrients metabolism.

Effects of meal and body sizes on gastric evacuation of the endangered Siberian sturgeon ( Acipenser baerii ) fed on either live or artificial diets: Using radiography technique

The effects of body and meals sizes on gastric evacuation (GE) of the endangered Siberian sturgeon (Acipenser baerii) were parameterized (at temperatures ranging from 16.8 to 17.6°C) using radiography technique. GE experiments were performed using different body sizes A. baerii ranged from 1.5 kg to 5 kg fed on meal sizes of 4.6 g to 47.6 g composed of either commercial pellets or live food (fish prey, whiting). The commercial pellets used in these experiments had barium sulphate at concentrations of 20%, while the same amount was injected into the body of live food for radiography technique monitoring. The course of GE in A. baerii was best described by the square root model independently of meal size. The effects of body mass and temperature on GE rates were described by power model and simple exponential model respectively. GE rates of A. baerii fed on live food could be summarized by (g/hr), while for commercial pellets, where St is the stomach contents mass (g), W is fish wet weight (cm), T is temperature (°C), and t is time (hr). These summarized models could estimate the time required for a meal to be evacuated from the stomach of A. baerii or determine the stomach fullness at postprandial time t. These results will assess the planning of feeding regime for A. baerii to avoid their overfeeding and underfeeding.

Growth and Metabolic Response of Chinese Perch to Different Dietary Protein-to-Energy Ratios in Artificial Diets

The effect of dietary nutrients on novel farm species has always garnered wide research and economic interest. Chinese perch, an economically important carnivorous fish, accepts an artificial diet after taming, so it is essential to evaluate and optimize the nutritional and metabolic demands of this species. However, little is known about the effect of an artificial diet on the growth and metabolism of Chinese perch. Therefore, the present study evaluated the growth and metabolic responses of Chinese perch to experimental diets with different dietary protein/energy (P/E) ratios. Five isoenergetic diets (18 kJ/g) with graded levels of P/E ratios of 30.58, 33.22, 35.90, 38.6, and 41.35 mg/kJ (named A, B, C, D, and E) were formulated. A total of 225 Chinese perch (64.89 ± 0.28 g) were divided into five groups (triplicate tanks for each group), distributed into 15 (350 L) fiberglass tanks, and fed twice a day at 4% of fish wet body weight with the respective P/E ratio diets for 10 weeks. Compared with the other groups, Chinese perch in Group C showed significantly improved growth performance, weight gain (WG), specific growth rate (SGR), viscerosomatic index (VSI), hepatosomatic index (HSI), intraperitoneal fat (IPF), feed utilization, feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE), energy retention efficiency (ERE), and feed efficiency (FE) as well as whole-body, muscle, and liver composition. Chinese perch in Group A, on the other hand, had the lowest growth performance, feed utilization, and body composition compared with the other groups. The activities of nitrogen metabolism-related enzymes (alanine aminotransferase (ALT), aspartate aminotransferase (AST) glutamate dehydrogenase (GDH), and adenosine 5′-monophosphate deaminase (AMPD)) as well as the mRNA expression of the GDH and AMPD genes were significantly lower than those in the other groups. Similarly, the expression of NPY and AgRp were significantly higher in Group C compared with the other groups. However, the gene expression of CART and POMC was not affected by the dietary P/E ratios. In Group A, the expression of mTOR, S6K, and 4EBP1 was significantly lower and that of AMPK, LKB1, and eEF2 was significantly higher when compared with the other groups. Biochemical analysis of blood showed that ALT, AST, total protein (TP), alkaline phosphatase (ALP), glucose (GLU), blood urea nitrogen (BUN), and triglyceride (TG) levels were also affected by the dietary P/E ratio. From our results, we concluded that Chinese perch growth performance and nutrient metabolism were significantly affected by the P/E ratio of the artificial diet. Second-order polynomial regression analysis revealed that Chinese perch growth performance was optimal at a P/E ratio of 37.98 in the artificial diet.

Biomass compensation: Behind the diversity gradients of tidepool fishes

AbstractSpecies richness is unevenly distributed on the Earth, with biodiversity gradients of various spatial scales supposedly being affected by abiotic as well as biotic factors including community traits such as body size spectra and relative abundance patterns. To explore large‐scale spatial variation in species diversity and their processes, tidepool fish communities were investigated through an intensive field work conducted on 55 shore sites in south‐western Japan. Multiple ecological measures were taken into account to assess changes in local community structures with changes in the number of species. Biomass (total fish wet weight) per unit area showed no systematic change with latitude, while taxa richness and number of individuals tended to increase toward lower latitudes. In addition, median fish body weight scaled positively with latitude, which was more conspicuous in Blenniidae than in Gobiidae. The latitudinal gradient of diversity in tidepool fish assemblages appears to be characterized by partitioning of total biomass that tends to stay constant across latitudes, suggesting the phenomenon of “biomass compensation” whereby body size and abundance/diversity change in opposite directions with latitude. Our study highlights that biomass compensation can be part of processes involved in generating gradients of species richness even without an apparent energy/resource gradient.

Toxicological responses following short-term exposure through gavage feeding or water-borne exposure to Dechlorane Plus in zebrafish (Danio rerio).

Dechlorane Plus (DP) is a chlorinated flame retardant widely used worldwide, and has been reported in environment and humans. However, only limited information is currently available on its toxicity on aquatic organisms. In this study, we employed zebrafish to evaluate possible toxicological responses including oxidative stress and endocrine disruption following exposure to DP. DP was dissolved in corn oil and was delivered to adult male zebrafish via gavage feeding. Delivery of DP was carried out twice on days 0 and 2, at up to 3 μg/g fish wet weight. Body residue level of DP in the fish at day 6 was within a range that has been reported in hot spot areas of China. On day 6, blood, liver, testis, and brain were collected and were evaluated for oxidative damage and endocrine disruption. Following DP exposure, hepatic catalase activity significantly increased, implying its oxidative damage potential. In addition, plasma thyroxine (T4) concentrations increased along with up-regulation of corticotropin releasing hormone and thyroid stimulating hormone β genes in brain. Following DP exposure, transcriptional responses of sex hormone related genes in brain were observed, suggesting possible sex hormone disrupting potentials of DP. However, water-borne exposure to DP up to 267 μg/L among the embryo and larval fish did not show any adverse effects on hatching time and transcription of thyroid hormone related genes. Our observations indicate for the first time that DP disrupts thyroid hormone balance of zebrafish by altering regulatory pathways in the brain. Handling editor: David Volz.

Effects of three frozen storage methods on wet weight of fish

Wet weight is one of the most common biological descriptors collected for fisheries research. Freezing is frequently used to preserve fish prior to processing in a lab, and wet weights are often collected for thawed fish. Freezing may affect the wet weight of fish and result in biased values for weight based metrics. Our objectives were to determine the effects of three frozen storage methods, size class of fish, and duration of storage on the changes in wet weight of emerald shiner (Notropis atherinoides) and rudd (Scardinius erythrophthalmus), and how failure to account for changes in wet weight affects percent dry weight estimates. Two size classes of emerald shiner and three size classes of rudd were collected from the upper Niagara River, New York. Fish were weighed immediately after being euthanized and then glazed with water, frozen in water, or vacuum-sealed and stored at −25°C for 3 or 6 months. After measuring post-thaw wet weight, fish were dried to a constant weight and percent dry weight was calculated based on prestorage wet weight and post-thaw wet weight. Then, we compared species specific prestorage wet weights to post-thaw wet weights for each storage method. Analysis of variance was used to investigate the effects of storage method, size class, and duration stored on wet weights of each species. Prestorage and post-thaw percent dry weights were compared to illustrate the effects of frozen storage on a commonly used weight-based metric. Emerald shiner and rudd wet weights differed from initial weights for all storage methods. Percent change in wet weight of emerald shiner was affected by interactions among storage method, size class, and duration stored, while percent change in wet weight of rudd was affected by the interaction between fish size class and storage method. Overall, storage method and size class had the greatest effects on changes in wet weight following frozen storage. Post-thaw wet weight increased from initial wet weight for fish frozen in water and decreased for vacuum-sealed and glazed fish, and smaller fish generally experienced greater changes than larger fish of the same species. Percent dry weight estimates based on post-thaw wet weights differed proportionally by −10.6–29.8% from estimates based on prestorage wet weights. Frozen storage can substantially affect weight based metrics such as percent dry weight and should be accounted for if weight is not measured prior to freezing.

Growth performance and nutrient digestibility of Cirrhinus mrigala fingerlings fed on soybean meal-based diet supplemented by phytase

The present study was carried out to evaluate the effects of phytase supplemented soybean meal based diet on growth performance and nutrient digestibility in Cirrhinus mrigala fingerlings. Presence of phytic acid in plant ingredients reduces the bioavailability of nutrient to fish as a result reduced fish growth. Reference diet and five test diets were prepared at 30% soybean meal based diet contents to examine the effects of phytase supplementation (0, 500, 1000, 1500 and 2000 FTU kg-1) on plant meal-based diet (soybean meal) and nutrient availability for Cirrhinus mrigala fingerlings. Chromic oxide was added as indigestible marker. Triplicate tanks were used for all treatments. Fingerlings were fed at the rate of 5 % of live wet weight of fish. Water quality parameters such as DO, temperature and pH in every tank were monitored using standard methods. The results from the current work showed that 1000 FTU kg -1 level in soybean meal based test diets increased the nutrient digestibility in C. mrigala as compared to reference diet which resulted in significant (P<0.05) increase in growth performance parameters. It is concluded and suggested that the phytase supplemented soybean meal based diet at 1000 FTU kg -1 level is optimum to release sufficient chelated nutrients for C. mrigala fingerlings.

Diet and feeding ecology of invasive icefish Neosalanx taihuensis in Erhai Lake, a Chinese plateau mesoeutrophicated lake

A comprehensive study of the invasive icefish Neosalanx taihuensis feeding ecology in Erhai Lake was conducted from November 2009 to October 2010. Prey items in the guts of the icefish sampled varied significantly according to season. This finding suggests a relationship between fluctuations in available prey in the environment and selective feeding by icefish. N. taihuensis preferred large-sized zooplankton, such as Daphnia and calanoids. Additionally, the gut fullness values differed significantly (P<0.001) among sampling times. To compare the values at different times, samples were taken over a 24 h period every 2 months for the entire year. The feeding activities of the fish were concentrated either in the morning (8:00) and/or at dusk (20:00), except in September 2010. This finding can be explained primarily by the variation in optimum light intensity. Daily N. taihuensis zooplankton consumption varied significantly, both diurnally and among seasons. The daily consumption values ranged from 0.089 to 0.237 g (wet weight) per 100 g wet fish weight in temperatures between 11.50°C and 24.68°C. This is the first report of diel feeding periodicity and daily food consumption of icefish in their invaded ecosystems.

Accumulation and distribution of multiwalled carbon nanotubes in zebrafish (Danio rerio).

No data on the bioaccumulation and distribution of multiwalled carbon nanotubes (MWCNTs) in aquatic vertebrates is available until now. We quantified uptake and elimination of dispersed radiolabeled MWCNTs ((14)C-MWCNT; 1 mg/L) by zebrafish (Danio rerio) over time. The influences of the feeding regime and presence of dissolved organic carbon (DOC) on accumulation of the nanomaterial were determined. The partitioning of radioactivity to different organs and tissues was measured in all experiments. A bioaccumulation factor of 16 L/kg fish wet weight was derived. MWCNTs quickly associated with the fish, and steady state was reached within 1 day. After transfer to clear medium, MWCNTs were quickly released to the water phase, but on average 5 mg of MWCNTs/kg fish dry weight remained associated with the fish. The nanomaterial mainly accumulated in the gut of all fish. Feeding led to lower internal concentrations due to facilitated elimination via the digestive tract. In the presence of DOC, 10-fold less was taken up by the fish after 48 h of exposure compared to without DOC. Quick adhesion to and detachment from superficial tissues were observed. Remarkably, little fractions of the internalized radioactivity were detected in the blood and muscle tissue of exposed fish. The part accumulated in these fish compartments remained constant during the elimination phase. Hence, biomagnification of MWCNTs in the food chain is possible and should be a subject of further research.

Analysis and Occurrences of Methoxylated Polybrominated Diphenyl Ethers and Polybrominated Diphenyl Ethers in Channel Catfish, Crayfish, Fish Feeds and Fishmeal from China

PBDEs are widely used brominated flame retardant, which are increasingly reported in the environment. MeO-PBDEs are structural analogs to PBDEs, and reported as natural products and novel pollutants present in the environment. Concentrations of thirteen PBDEs and eight MeO-PBDEs in a large number of channel catfish, crayfish, fish feeds and fishmeal collected from Hubei province of China were investigated in this study. A fast isotopic dilution GC-MS method was firstly developed to simultaneously determine thirteen PBDEs and eight MeO-PBDEs in channel catfish, crayfish, fish feeds and fishmeal in this study, and especially for the first time MeO-PBDEs and PBDEs in crayfish, fish feeds and fishmeal. Pressurized liquid extraction and multi-layer silica gel column chromatography cleanup were used, and some important steps and crucial parameters were modified and intensified compared with other literatures. Besides, the conditions of GC and MS were also optimized. The limits of quantitation values of 0.25-5, 1-5 μg kg-1 wet weight in channel catfish and crayfish were calculated for PBDEs and MeO-PBDEs, respectively; so did 1-20, 4-20 μg kg-1 wet weight in fish feeds and fishmeal. In addition, good repeatability and accuracy of the whole method were achieved. The established methods were therefore suitable for the simultaneous determinations of thirteen PBDEs and eight MeO-PBDEs in these samples at trace contamination levels. Using the established methods, PBDEs or MeO-PBDEs emerged in 2 of 80 channel catfish, 1 of 80 crayfish, 6 of 60 fish feeds and 4 of 40 fishmeal, and in low-μg kg-1 wet weight for these samples.

Bioaccumulative Characteristics of Polybrominated Diphenyl Ethers in Channel Catfish and Fish Feeds from China

PBDEs are widely used brominated flame retardant, which are increasingly reported in the environment. Concentrations of thirteen PBDEs in a large number of channel catfish and fish feeds collected from Hubei province of China were investigated in this study. A fast isotopic dilution GC-MS method was firstly developed to simultaneously determine thirteen PBDEs in channel catfish and fish feeds in this study, and especially for the first time PBDEs in fish feeds. Pressurized liquid extraction and multi-layer silica gel column chromatography cleanup were used, some important steps and crucial parameters were modified and intensified compared with other literatures, and GC and MS conditions were optimized. The limits of quantitation values of 0.25 - 5 μg·kg-1 wet weight in channel catfish were calculated for PBDEs; so did 1 - 20 μg·kg-1 wet weight in fish feeds. In addition, good repeatability and accuracy of the whole method were achieved. The established methods were therefore suitable for the simultaneous determinations of thirteen PBDEs in these samples at trace contamination levels. Using the established methods, PBDEs emerged in 10 of 180 channel catfish and 13 of 115 fish feeds, and the dominant PBDEs homologues were PBDE-28, PBDE-47, PBDE-100, PBDE-99, PBDE-154, PBDE-153 and PBDE-183. The detection rates of seven PBDEs congeners were in turn respectively 1.74%, 7.83%, 4.35%, 5.22%, 3.48%, 2.61% and 2.61% in fish feeds, and detection rates of seven PBDEs congeners were in turn respectively 1.11%, 3.89%, 2.22%, 1.67%, 1.11%, 1.11% and 1.11% in channel catfish. There was significant correlation in PBDEs between matching channel catfish and fish feeds (R2 = 0.742, P

Comments on proper (and improper) solutions of bioenergetic equations for modeling fish growth

This paper demonstrates that conventional bioenergetic models, that are commonly used to simulate fish growth or consumption, violate basic requirements of energy conservation when improperly applied for cases where the energy density of the fish is either a function of fish wet weight or an independent function of time. It appears that many previously published modeling results suffer from this deficiency unless the authors have made perspicuous provisions to avoid implicit imbalances that occur in the equations under these conditions. The incorrect solutions tend to overestimate fish growth and net energy consumption. The magnitude of these errors is a function of how rapidly the fish energy density changes as the fish increases in size. The errors can be as much as 30% for small fish in the range of 1 to 5g per individual where the energy density changes rapidly. Although this mathematical error does not occur if fish energy density is modeled as a constant, this assumption is probably inadequate for most applications and results in a substantial “biological error.” It is recommended that published results for these various cases be critically reviewed and corrected where warranted. The errors can be readily eliminated when the bioenergetic model equations are handled properly as demonstrated in this paper.