Gram Of Fish Research Articles

Effect of An Additional Amount of Fish and Fermentation Time on The Sensory Properties of The Lemea

Lemea, a traditional fermented food of the Rejang people in Bengkulu, is made from young bamboo and fish. The fish commonly used in the making Lemea is Mozambique tilapia or Mujair (Oreochromis mossambicus). The fermentation process typically lasts between 3 to 7 days. This study aimed to assess the sensory characteristics, including taste, color, texture, and aroma, of Lemea, based on the preferences of panelists. The variations examined were fermentation duration, and the amount of Mujair fish added. The research followed a completely randomized design, incorporating three fermentation durations (24, 96, and 144 hours) and three fish quantities (250 grams, 500 grams, and 750 grams). Sensory evaluations were conducted on the fermented samples, encompassing taste, aroma, texture, and color. The data revealed that the most favored taste and texture of Lemea were achieved with 500 grams of fish and a fermentation duration of 144 hours (J2W3). Likewise, the preferred aroma and color were observed in the sample with 750 grams of fish and 24 hours of fermentation (J3W1). The data analysis indicated that the sample with 500 grams of fish and a fermentation duration of 144 hours (J2W3) exhibited the most favorable sensory characteristics (taste, aroma, texture, and color). Thus, the quantity of fish added and the duration of fermentation influenced the sensory attributes of Lemea.

Reproductive parameters of Oreochromis mossambicus in Laguna de Los Patos, Cumaná, Venezuela.

A total of 381 specimens of the tilapia Oreochromis mossambicus collected monthly from May 2017 to May 2018 in the Laguna de Los Patos, Cumaná, Venezuela, to evaluate reproductive parameters of this non-native species. Significant differences were found in relation to average height and weight between males and females, with the highest values in males. The sex ratio was 1:1.5 (males:females), which deviates significantly from the expected 1:1 ratio. The mean length of sexual maturity (Lm50) was 18.0 cm in females and 20.1 cm in males, reflecting that females mature at smaller sizes than males. The monthly variations of the gonadosomatic index (GSI) and the stages of sexual maturity show two reproductive peaks during the study, in October 2017 and April 2018, coinciding with the rainy and dry seasons in the region respectively. The condition factor (CF) showed significant differences between months, but not between sexes, with an average of 1.87 in females and 1.84 in males. The average absolute fecundity was 921 ± 604.6 eggs per fish, with a relative fecundity of 8.36 ± 3.09 eggs per gram of fish. Differences in oocyte size in mature females confirm that the species can spawn repeatedly over a period, which is considered an important factor for the establishment of tilapia in non-native environments.

A multifaceted assessment of the effects of polyethylene microplastics on juvenile gilthead seabreams (Sparus aurata).

Plastic pollution has become a major environmental and societal concern in the last decade. From larger debris to microplastics (MP), this pollution is ubiquitous and particularly affects aquatic ecosystems. MP can be directly or inadvertently ingested by organisms, transferred along the trophic chain, and sometimes translocated into tissues. However, the impacts of such MP exposure on organisms' biological functions are yet to be fully understood. Here, we used a multi-diagnostic approach at multiple levels of biological organization (from atoms to organisms) to determine how MP affect the biology of a marine fish, the gilthead seabream, Sparus aurata. We exposed juvenile seabreams for 35 days to spherical 10-20µm polyethylene primary MP through food (Artemia salina pre-exposed to MP) at a concentration of 5±1µg of MP per gram of fish per day. MP-exposed fish experienced higher mortality, increased abundance of several brain and liver primary metabolites, hepatic and intestinal histological defects, higher assimilation of an essential element (Zn), and lower assimilation of a non-essential element (Ag). In contrast, growth and muscle C/N isotopic profiles were similar between control and MP-exposed fish, while variable patterns were observed for the intestinal microbiome. This comprehensive analysis of biological responses to MP exposure reveals how MP ingestion can cause negligible to profound effects in a fish species and contributes towards a better understanding of the causal mechanisms of its toxicity.

Nitrogen and phosphorus flux in wastewater from three productive stages in a hyperintensive tilapia culture

Abstract In this research, effect of productive stages in nitrogen and phosphorus excretion in wastewater from hyperintensive tilapia (Oreochromis niloticus) culture was evaluated. Fish were cultivated considering three development stages (fingerling of 1.79 g, juvenile of 36.13 g, and adult of 72.96 g). Nitrite, nitrate, ammonium, and phosphorus concentration were determined in order to know the amount of nutrients excreted per productive stage of the fish at a high stocking density. Biometric data were recorded during the experiment with the purpose of determining the growth behavior of fish, as well as the measurement of the aerobic metabolism. Results showed that survival, growth, and health of fish are not affected by hyperdensity of culture; as well, combined catabolism of proteins and lipids was presented as substrates for energy with value for O:N ratio ranging between 20 and 60. In addition, higher concentration in excretion of nitrogen compounds and phosphorus per gram of fish was recorded in wastewater from a hyperintensive culture in fingerlings than in juveniles and adults. These results suggest the use of this wastewater in the early stages of fish growth, aiming to enhance sustainable systems with maximum use of the resources, such as aquaponics systems.

Microplastic and tire wear particle occurrence in fishes from an urban estuary: Influence of feeding characteristics on exposure risk

The influence of feeding behavior and feeding ecology on microplastic occurrence in fishes in an urbanized estuary was studied by surveying microplastics in the digestive tracts (gut) of five fish species: the planktivorous Bay Anchovy and Atlantic Menhaden, the piscivore Spotted Seatrout, the benthivore Spot and the detritivore/benthivore Striped Mullet. Microplastics were found in 99% of fishes collected with an average of 27 microplastics per individual fish, 6 microplastics per gram of fish, and 21 microplastics per gram of gut, although exposure varied among species. Atlantic Menhaden possessed significantly more microplastic per fish weight than other species, which may be attributed to their regular ingestion of marine snow aggregates. Fibers were the most common type of microplastic in all fishes, and suspected tire wear particles were found in 14% of individuals across all five species, constituting the first evidence of tire wear particle consumption in field-collected organisms.

Culturally adapted mobile technology improves environmental health literacy in Laurentian, Great Lakes Native Americans (Anishinaabeg)

The presence of persistent bioaccumulative toxics (PBT) in aquatic food chains complicates decision processes of people with a strong culture of fish consumption. This environmental contamination is especially problematic for Native American populations in the Laurentian Great Lakes region (Anishinaabeg). Pursuing the growing discipline of environmental health literacy (EHL) may help reduce toxic exposures, support healthy decision-making, and combat health deficits. Our goals for this research were first to improve environmental health literacy using novel technologies and second to help define environmental health literacy metrics that can be tracked over time, especially regarding culturally-contextualized health interests. We recently reported that a mobile app (Gigiigoo'inaan App) presenting personalized, culturally-contextualized fish consumption advice may improve EHL for the Anishinaabeg. Gigiigoo'inaan App safely supports desired fish consumption rates by putting local data into the hands of the Anishinaabeg. We conducted a pre-test post-test evaluation with 103 Aninishinaabe adults. Participants estimated their current fish meal consumption over a hypothetical month before exposure to the software and then planned their future consumption of fish meals in a month after using the mobile app. Significantly more monthly traditional fish meals on average (Median: 4 vs 2, p = 0.0005) were selected when using the app versus pre-exposure to the app. Significantly more traditional grams of fish were also selected during use of the app relative to the pretest (Median: 680.39 g vs 453.59 g, p = 0.0007). These increases were accompanied by widespread (97%) adherence to conventional advice that minimizes PBT exposure health effects (ATSDR minimum risk levels).

Formation of individual and group profilaktic programs using automated monitoring and evaluation of risk factors of development of non-infectious diseases

The goal is to develop a system for monitoring and assessing individual risk factors for the development of NCDs by implementing an advanced anamnesis questionnaire into the Unified Medical Information System of the healthcare institution.Materias and methods. The results of the anamnestic survey of 854 patients undergoing a planned prophylactic examination (male patients - 44%, women - 56%, average age of the respondents - 48.0 ± 10.3 rubles) testify to the expediency of introducing into the practice of the primary care physician. The subject of the study was anamnestic questionnaire on advanced questionnaires to determine the necessary diagnostic interventions in order to conduct an annual preventive medical examination, that is, the development of an individual prophylactic program.Results and discussion. Among the respondents, the proportion of those who adhere to the basic principles of a healthy lifestyle - spend on walking at a moderate pace more than 30 minutes a day (69.68% of respondents), daily 4-5 servings of vegetables and fruits (57.4%) or / or 100 grams of fish (62.96%) twice a week and pay attention to the content of fat and / or cholesterol in products when purchased (43.51% respectively) - was quite high - only 4.63% 0.8%, with 19.44% of those polled noted that their habit was to smoke more than one cigarette on the day of the respondents. Among patients, on the basis of anamnestic survey, on average, 13.84% confirmed the presence of illnesses in their close relatives (mother, father, brother, sister) that can provoke the development of NCDs in patients. In particular, 18.29% of the respondents answered the affirmative response to myocardial infarction in mother or sister up to 65 years old and father or brother up to 55 years old. It is the presence of certain risk factors for the development of NCDs, automatic processing of questionnaires and automated analysis of results allowing the formation of an individual prophylactic program of the patient.Conclusion. Thus, an approach to the formation of individual prophylactic programs with the use of monitoring and evaluation of risk factors for the development of NCDs, allows to determine the list of diagnostic examinations for the development of an individual program of passing an annual preventive medical examination, taking into account the results of anamnestic questionnaire, implemented to the Unified Medical Information System of the Health Care Institute.

Distribution of perfluorinated compounds (PFASs) in the aquatic environment of the industrially polluted Vaal River, South Africa

Perfluorinated alkyl substances (PFASs) are highly persistent chemicals, which have a bioaccumulative potential and can be found in wildlife around the world. Although multiple studies have been performed on PFASs pollution of the aquatic environment, little is known on PFASs pollution on the African continent and their possible risks for human health. In the present study, we examined the distribution of 15 PFASs in fish, invertebrates, sediment and water, collected at three sites, representing a gradient of industrial and mining pollution, along the Vaal River, South Africa. Furthermore, possible risks for human health through consumption of contaminated fish were examined.Perfluorooctane sulfonate (PFOS) was the most dominant PFAS measured in biota, whereas perfluoropentanoic acid (PFPeA) was measured in higher concentrations in water. Mean PFAS concentrations in water ranged from <LOQ to 38.5ng/L. PFAS concentrations in water decreased along the gradient and were similar or lower compared to other studies in Europe, Asia and America. PFAS measurements in sediment were <LOQ, with the exception of PFOS at Thabela Thabeng (2.36ng/g dry weight (dw)). Average ∑PFAS concentrations in biota increased along the gradient and ranged from <LOQ to 34.5ng/g wet weight (ww) in invertebrates, <LOQ to 289ng/g ww in liver and <LOQ to 34.0ng/g ww in muscle tissue. Although PFOS concentrations were relatively high compared to literature, concentrations of other PFASs were rather low.A potential risk for humans through consumption of PFAS-contaminated fish was assessed. Tolerable daily intake values (grams of fish that can be eaten daily without risking health effects) were much lower than the average South African fish consumption per day, implying a potential risk for human health through consumption of PFAS contaminated fish. CapsuleConcentrations of perfluorinated compounds in water, sediment, fish and invertebrates from the Vaal River were low or intermediate and posed a potential risk for human health through consumption of contaminated fish.

Catch per unit efforts and impacts of gears on fish abundance in an oxbow lake ecosystem in Eastern India

Background: Oxbow lakes are abundant in indigenous fishes, but they are subject to unsustainable fishing practices, potential overexploitation, and indiscriminate use of fine-meshed fishing gear. To quantify the catch per unit effort (CPUE) and impact of fishing gears on fish abundance, a survey was carried out in an oxbow lake in eastern India. Methods: The gear-wise CPUE for fish caught in per unit hour of operation was calculated by dividing the total sampling gear catch in biomass, which is the observed value of fish caught by a particular gear, by the total sampling effort hours. A value of P < 0.05 was accepted as statistical significance. Results: Average annual values of the CPUE of triangular push nets, gill nets, long lines, seine nets, drag nets, stationary dip nets, cone-framed cast nets, and line and hook were calculated as 328.34, 4.12, 36.71, 572.92, 3928.57, 237.78, 235.80, and 0.44 grams of fish per hour of operation, respectively. All the 8 different gears exhibited lower CPUE during monsoon and post-monsoon seasons than in the premonsoon season. The line and hook was dominant (>71%). Cone-framed cast net hauled the maximum catch in biomass (31.51%), and gill nets contributed the maximum number of fish (64.92%). The lower CPUE values of line and hook, gill net, cone-framed cast net and long lines identified them as the most harmful among all gears. Conclusion: Indiscriminate use of gear, particularly line and hook, gill nets, cone-framed cast nets, and long lines, demands regulations and preventions concerning such gear to obtain higher fish abundance.

Assessment of Fishery Products Consumption Behavior: the Case of Turkey

From the early history of humanity until today, fish and other fishery products have always been involved in human diet. The intake of a sufficient number of proteins has been enabled through high-quality fish meat containing a significant quantity of essential amino acids as well as omega-3 fatty acids. According to the studies, 150 grams of fish, meets the needs of a 50-60% of daily protein intake for an adult. A large part of fishery production in Turkey (86%), is consumed fresh. Turkey, within the scope of Common Fisheries Policy is trying to harmonize fisheries with the EU. A failure to update the 1380 coded Fisheries Law and rapid issuing of EU compatible regulations, safe food for consumers, high quality products along the year for processing industry and marketers, as well as the inability to ensure sustainable price development for the producers, prevent the success of the sector. The aim of this study was to determine the consumption behavior when taking fishery products in terms of food safety, reliability, product quality as well as the level of income and education.

Evaluation of cadmium and lead levels in fillet marine fish (Otolithes ruber and Lutjanus johni)-from Persian Gulf

Background: Pollution of aquatic system with heavy metals is one of the important environmental problems that can make toxic marine organisms and aquatic food chain, so it is a risk factor for human health over time. Objective: The present study aimed to the evaluation of cadmium (Cd) and lead (Pb) Levels in fillet marine fish (Otolithes ruber and Lutjanus johni) from Persian Gulf. Materials and Methods: At the first, 50 fish samples (O. ruber and L. johni) were collected during winter and spring of 2012 at three different sites from Persian Gulf. The Cd and Pb concentrations were determined with an atomic absorption spectrophotometer. The results expressed in micrograms of metal per dry weight gram of fish (μg/g). Results: The results were validated according to the International Standards Organization 17025 accreditation. Statistical analyses were performed using SPSS software at the significant level of 95%. Maximum Cd and Pb concentration were seen in O. ruber (0.47 μg/g and L. johni (3.12 μg/g), respectively. No significance difference between the fish size and the metal levels for Cd was recorded in fish (P > 0.05). The relationship between the fish size and Pb level in the muscles was positive in two fish species (P

Quantification of eDNA shedding rates from invasive bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix

Wildlife managers can more easily mitigate the effects of invasive species if action takes place before a population becomes established. Such early detection requires sensitive survey tools that can detect low numbers of individuals. Due to their high sensitivity, environmental DNA (eDNA) surveys hold promise as an early detection method for aquatic invasive species. Quantification of eDNA amounts may also provide data on species abundance and timing of an organism’s presence, allowing managers to successfully combat the spread of ecologically damaging species. To better understand the link between eDNA and an organism’s presence, it is crucial to know how eDNA is shed into the environment. Our study used quantitative PCR (qPCR) and controlled laboratory experiments to measure the amount of eDNA that two species of invasive bigheaded carps (Hypophthalmichthys nobilis and Hypophthalmichthysmolitrix) shed into the water. We first measured how much eDNA a single fish sheds and the variability of these measurements. Then, in a series of manipulative lab experiments, we studied how temperature, biomass (grams of fish), and diet affect the shedding rate of eDNA by these fish. We found that eDNA amounts exhibit a positive relationship with fish biomass, and that feeding could increase the amount of eDNA shed by ten-fold, whereas water temperature did not have an effect. Our results demonstrate that quantification of eDNA may be useful for predicting carp density, as well as densities of other rare or invasive species.

Detection rate of diarrhoea-causing Kudoa hexapunctata in Pacific bluefin tuna Thunnus orientalis from Japanese waters

Diffuse outbreaks of food poisoning with unknown aetiologies leading to diarrhoea and vomiting within a short time after ingesting flatfish (Paralichthys olivaceus), tuna (Thunnus spp.), or amberjack (Seriola dumerili) have occurred nationwide in Japan, including the Tokyo metropolitan area. In this study, we surveyed the detection rates of kudoid parasites in 12 tuna samples that caused clinical diarrhoea from 2009 to 2012; we assessed 104 samples of whole juvenile Pacific bluefin tuna (PBT, Thunnus orientalis) and 153 block samples of other tuna distributed in the Tokyo Metropolitan Central Wholesale Market. The survey revealed that more than 70% of clinical diarrhoea cases due to tuna ingestion occurred between June and September, and Kudoa hexapunctata were detected in 9 of 12 tuna samples associated with clinical diarrhoea cases. The numbers of spores and 18S ribosomal DNA (rDNA) copies per gram of fish in 8 of 9 samples were more than 1×106 spores and 1×109 copies, respectively. Market research revealed that the K. hexapunctata-positive rate in juvenile PBT from Japanese waters was 64.4% (67/104) but that in adult PBT was 10.4% (7/67). The numbers of K. hexapunctata 18S rDNA copies in 64.5% (20/31) samples and 72.7% (16/22) of <5kg fish samples collected between May and July were more than 1×109copies/g. On the other hand, kudoid parasites were not detected from 73 tuna samples except for a single sample of Thunnus albacares. Cell monolayer permeability assays performed to examine the toxicity of K. hexapunctata against Caco-2 cells revealed that the transepithelial electrical resistance (TER) in 5×107K. hexapunctata spores decreased by 80% within 2–4h. In conclusion, K. hexapunctata was commonly detected in juvenile PBT from Japanese waters and are a likely cause of the diarrhoea outbreaks.

Overall effect of diet and supplementation with omega ‐3 fatty acids on the concentration of IL ‐6 and TNF‐α in obese adults (1034.17)

Adequate dietary intervention in obesity is associated with decrease in proinflammatory factors by decreasing fat mass. The omega‐3 marine origin, have an antithrombotic and vasodilator effect, therefore play a role in cardiovascular disease to reduce the tendency to thrombus formation, platelet aggregation, blood viscosity, the presence of arrhythmias and the levels of inflammatory cytokines such as TNF‐α IL‐6. The American Heart Association recommends the consumption of 1g of omega‐ 3 per day, either through consumption of cold water fish or supplementation with capsules containing EPA and DHA. The objective was identify the effect of supplementation for 3 months with omega‐3 in conjunction with a dietary intervention on the concentration of IL‐6 and TNF‐α in obese adults. This is a quasi experimental clinical trial that included 29 adults with obesity according to BMI which received a diet according to the basal energy expenditure obtained by indirect calorimetry, with 55% carbohydrates, 20% protein and 25% lipids and supplemented by three months with 1.5g of omega ‐3 to 60% concentration per gram of fish. Determined basal and final weight, visceral fat mass and fat mass by bioimpedance and IL‐6 and TNF‐ α by ELISA. The results of the paired t‐ test showed a statistically significant difference in weight, BMI, body fat and visceral fat (P &lt;0.05) as well as in levels of IL‐6 (20.6 ng/mL vs 12.7ng/mL; P &lt;0.05). While the levels of TNF‐α showed no statistically significant difference after 3 months of therapy (10.0 ng/mL vs 7.2 ng/mL; P &gt; 0.05). The significant weight loss at the expense of fat mass and omega‐3 supplementation significantly decreased the level of inflammation from the IL ‐6 in obese adults.

Genotoxic evaluation of different doses of methylmercury (CH3Hg+) in Hoplias malabaricus

The survey of the effects of toxic metals and its organic compounds are of critical importance because these compounds tend to accumulate in aquatic environments. In the present work, the genotoxic potential of methylmercury, an organomercurial compound with high toxicity and present in large amounts in fish of the Amazon due to the mining process, was evaluated using the piscine micronucleus test and comet assay in fish. Specimens of Hoplias malabaricus (popularly known as traira), a neotropical specie, was exposed to methylmercury via food web, over 70 days, in two different concentrations: two groups of fifteen fish were tested with 0.075 μg CH3Hg+/g and 0.75 μg CH3Hg+/g of methylmercury per gram of fish, at 5-day intervals and over 14 successive intervals whereas control group, composed by nine fish, was fed by uncontaminated prey fish (Astyanax sp). One of the aims of this study was to reproduce the contamination found in nature in an attempt to increase our biological knowledge on the neotropical species. Hoplias malabaricus specimens were then anesthetized for removal of blood samples and dissected, for cephalic kidney removal. As a result, it was observed that the piscine micronucleus test showed no significant differences between exposed groups and control group. The comet assay performed on erythrocyte system cells, showed a significant difference between controls and contaminated, but there was no difference between doses. In contrast, the kidney cells comet assay showed no significant difference between groups, probably due to the type of damage caused by xenobiotics to be related to the tissues of most contact with it, as well as its mode of action and the chain of bioaccumulation within bodies.

(CdSe/ZnS QDs)-ionic liquid-based headspace single drop microextraction for the fluorimetric determination of trimethylamine in fish

Here, we propose the use of ionic liquid-modified QDs for the combination of ionic liquid-based headspace single drop microextraction technique (IL-HS-SDME) and QD-based fluorimetric detection. In that way, we exploit the advantages of ILs as extractant solvent and the use of QDs as fluorescence detection probe. After in situ generation of volatile trimethylamine (TMA) from fish samples, the analyte was extracted and preconcentrated directly onto a (QD)IL microdrop by HS-SDME. Then, TMA was quantified through the enhancing effect produced on the initial fluorescence of the (QD)IL dispersion. The working conditions for the (QD)IL-HS-SDME procedure were: 20 μL microdrop of (QD)IL exposed for 2 min to the headspace of a 5 mL aqueous sample (0.2 g of fish in 10 M NaOH) placed in a 10 mL vial with stirring and thermostatted at 50-60 °C. For the detection, the microdrop was transferred to a microcuvette with 300 μL of acetonitrile and the fluorescence was recorded (λ(em) = 570 nm, λ(exc) = 400 nm). Under the selected conditions, the analytical response was linear over the range from 0.05 to 0.25 mg L(-1) (R(2) = 0.997) with a detection limit of 0.014 mg L(-1) (0.35 μg TMA per gram of fish) and the relative standard deviation was 3.5% (n = 5). The proposed method was applied to the determination of TMA in hake fish samples with satisfactory results.

Determination and assessment of total mercury levels in local, frozen and canned fish in Lebanon

Fish is an important constituent of the Lebanese diet. However, very little attention in our area is given to bring awareness regarding the effect of the toxicity of mercury (Hg) mainly through fish consumption. This study aimed to report analytical data on total mercury levels in several fish species for the first time in thirty years and to also made individuals aware of the presence and danger from exposure to mercury through fish consumption. Fish samples were selected from local Lebanese markets and fisheries and included 94 samples of which were fresh, frozen, processed, and canned fish. All values were reported as microgram of mercury per gram of fish based on wet weight. The level of mercury ranged from 0.0190 to 0.5700 μg/g in fresh samples, 0.0059 to 0.0665 μg/g in frozen samples, and 0.0305 to 0.1190 μg/g in canned samples. The data clearly showed that higher levels of mercury were detected in local fresh fish as opposed to other types thus placing consumers at higher risk from mercury exposure. Moreover, the data revealed that Mallifa (yellowstripe barracuda/Sphyraena chrysotaenia), Sargous (white seabream/ Diplodus sargus), Ghobbos (bogue/ Boops hoops), and shrimp ( Penaeus sp.) were among the types containing the highest amounts of mercury. On the other hand, processed fish such as fish fillet, fish burger, small shrimp and crab are found to contain lower levels of mercury and are associated with lower exposure risks to mercury. Lebanese population should therefore, be aware to consume limited amounts of fresh local fish to minimize exposure to mercury.

A study on the optimal hydraulic loading rate and plant ratios in recirculation aquaponic system

The growths of the African catfish ( Clarias gariepinus) and water spinach ( Ipomoea aquatica) were evaluated in recirculation aquaponic system (RAS). Fish production performance, plant growth and nutrient removal were measured and their dependence on hydraulic loading rate (HLR) was assessed. Fish production did not differ significantly between hydraulic loading rates. In contrast to the fish production, the water spinach yield was significantly higher in the lower hydraulic loading rate. Fish production, plant growth and percentage nutrient removal were highest at hydraulic loading rate of 1.28 m/day. The ratio of fish to plant production has been calculated to balance nutrient generation from fish with nutrient removal by plants and the optimum ratio was 15–42 gram of fish feed/m 2 of plant growing area. Each unit in RAS was evaluated in terms of oxygen demand. Using specified feeding regime, mass balance equations were applied to quantify the waste discharges from rearing tanks and treatment units. The waste discharged was found to be strongly dependent on hydraulic loading rate.

Reproductive biology of a Characidiinae (Osteichthyes, Characidae) from the Ubatiba River, Maricá-RJ.

The Ubatiba river is a coastal stream subject to stochastic spates all over the year and, Characidium sp.n. is among the twenty-two species that compose its ichthyofauna. In this study we analyse some traits of its reproductive biology and discuss whether the adopted strategy has causal relationship with the environmental variables. Specimens were collected in the upper Ubatiba river. Samplings, were carried out monthly by electrofishing, between Oct./94 and Sep./95. Some differences between male and female strategies were observed. Females were significantly (p < 0.05) bigger than males; length--weight relationship was different (p < 0.05) between sexes with the onset of sexual maturity occuring at smaller sizes among males. Reproductive investment is high for both males and females but higher for males, maximum Gonadosomatic Index for females and males were 40.97% and 44.90%, respectively. Reproductive specimens were registered all over the year, suggesting continuous reproduction. High values of fecundity were also registered varying from 1342 to 5535 eggs for ripe females of 4.4 and 7.0 cm, respectively and an amount of 1105 oocytes per grams of fish. We suggest that differences in the reproductive strategy, between sexes, determine the observed patterns in the size structure; the absence of males in the higher SL classes could be a consequence of high mortality rates and/or reduction in the growth rates as a precocity consequence in the onset of reproduction and/or high reproductive investment. Relationship between continuous reproduction and environmental condition could be explained as an adaptation to maximise supervivency of the young fishes that is: guarantee the species maintenance in a stochastic environment.

Diet of cormorants and the impact of cormorant predation on juvenile flatfish in the Dutch Wadden Sea

Predation by great cormorants Phalacrocorax carbo on juvenile flatfish in the Dutch Wadden Sea was estimated from otoliths found in 182 regurgitated pellets. Pellets were collected at the main night roosts and in one colony, in late summer when cormorant numbers peak in the area. Otoliths of at least 24 different fish species were found, including both marine and freshwater species. Flatfish on average amounted to 73% of the fish found in numbers and contributed 79% by mass to the birds' diet. Among the flatfish species, 0-group fish were predominantly taken. Plaice Pleuronectes platessa was found most frequently (46% of all 0-group flatfish, n=6318), followed by dab Limanda limanda (34%), flounder Platichthys flesus (19%) and sole Solea solea (1%). Total consumption by cormorants was estimated by multiplying the number of cormorant-days over summer (184 days) by the mean number of flatfish found in the pellets per sampling location, under the assumption that each pellet contained the remains of the fish eaten during 24 hours and that the diet was similar in all summer months. In total about 28.58 million flatfish were consumed over summer, 27.46 million of which were 0-group fish, including 12.55 million 0-group plaice, 9.45 million dab, 5.17 million flounder and 0.29 million sole. These figures are underestimates, because some otoliths were clearly missing, and estimated average daily intake per cormorant on the basis of all otoliths found in the pellets (460 grams of fish) was only 70 to 90% of the theoretical daily food requirement. In 1992 and 1993 0-group flatfish abundance was very low and cormorant predation during the period July to September (92 days) accounted for 49.5% of the total stage mortality in 0-group plaice in 1992 and 27.3% in 1993. However, in normal years the impact of cormorant predation will be much lower.