Natural Breeding Ground Research Articles

Importance of Proper Breeding Techniques in Enhancing Magur Seed Production

Fish farmers in eastern India, consider it to be a species of choice for diversifying their cultural practice since it provides them with a considerable return on their investment. The natural seeds of Magur have been sharply declining due to ecological imbalance in their natural breeding ground, which is low lying paddy field. This imbalance is caused by the indiscriminate use of chemical fertilizer and chemical pesticides. However, the availability of Magur seeds in desired hours of stocking in desired quantity stands as a constraint to the propagation of culture of this species. It is consequently the only method that is feasible to reduce the severity of the issue, and that is to induce breeding of the species in captivity. There have only been a few models designed for the purpose of reproducing Magur in captivity, but each of these models involves a significant amount of financial investment. However, a labor-intensive and low-cost farmers'-friendly model for the production of small quantity seeds has not yet been standardized for rural small scale fish farmers. In this paper we found that magur seed production can be done through low cost investing, that’s why farmers or rural people get more economic profit. The study demonstrates how specific breeding techniques and management practices can significantly enhance seed production, contributing to the sustainability of Magur aquaculture in India.

Analysis of Heavy Metal Pollution in the Water of the Halda River: A Distinctive Breeding Habitat for Carp Fish in Bangladesh.

The present study aimed to assess the heavy metal concentrations in water from different sampling sites of the Halda River, the only natural breeding ground of Indian major carps. We have analysed the contamination level and seasonal variations of heavy metals (viz. Fe, Cu, Zn, Cr, Cd and Pb). The favourability of the breeding environment was assessed by different contamination indices. Samples were collected from six sampling sites for four different seasons, and the metal concentrations were determined for water samples using Flame atomic absorption spectrophotometer. The obtained order of mean concentrations of heavy metals for four seasons was winter>spring>monsoon>pre-monsoon, and the assessed mean concentrations (mg/L) of heavy metals follow the trend: Fe (9.129)>Pb (0.033)>Zn (0.024)>Cr (0.017)>Cu (0.012)>Cd (0.002). The concentration of Fe was found above the permissible limit set by the World Health Organization (WHO) (Guidelines for Water Quality) and ECR (1997), and the concentrations for Pb were found above the USEPA (2006) limit in all four seasons. Contamination indices (heavy metal pollution Index [HPI] and metal index [MI]) indicate that during winter and monsoon, the river water metal condition is critical (HPI>100) and the sites are moderately as well as slightly (1<MI<2) affected by the studied heavy metals. Contamination indices, such as contamination factors (Cf), degree of contamination (Cdeg) and the pollution load index (PLI), demonstrate the fact that Fe and Pb remarkably contaminated the studied sampling sites. The Pearson correlation matrix and the principal component analysis (PCA) revealed that the studied metals are connected by their sources, which can be geological or anthropogenic. Urgent initiatives need to be taken, and effective strategies must be implemented to control the different sources responsible for the entry of heavy metals into the Halda River water.

Assessment of heavy metal concentration in the water of major carp breeding River Halda, Bangladesh

Heavy metal contamination in river water is a result of anthropogenic sources like industrial waste, tanneries, used fertiliser, and sewage discharge. Bioaccumulation and toxicity of heavy metals are alarming concerns for the natural carp breeding ground of the one and only river Halda of Bangladesh. Seven heavy metals (Fe, Mn, Cu, Co, Ni, Zn, and Cr (VI)) were assessed in this study following standard methods by gathering data from 36 sampling points that are situated along the area between the origin of Halda and Kalurghat confluence point of Halda and Karnofuli. An atomic absorption spectrophotometer was used for the measurement of the heavy metals, and the correlation between the parameters was determined using principal component analysis (PCA). The concentration of heavy metals ranged from 0.316 to 3.216 mg/L for Fe, 0.023–0.236 mg/L for Mn, 0.022–0.044 mg/L for Cu, 0.022–0.051 mg/L for Co, 0.002–0.008 mg/L for Ni, 0.037–0.282 mg/L for Zn, and 0.013–0.146 mg/L for Cr (VI), respectively. Cu and Mn values in some points were above the permissible limit, but other metal contents were within the permissible limit.

Feeding and reproduction of striped snakehead Channa striata (Bloch, 1793) inhabiting the Gangetic river system

The striped snakehead Channa striata is a valuable food fish and has a high market value. The feeding and natural breeding grounds of this economically important fish species have been reduced due to increasing anthropogenic activities and habitat alterations in the Gangetic River system. The present study was undertaken to assess the feeding and reproductive biology of C. striata, which is widely distributed in India and many other Asian countries (Pakistan, Bangladesh, Thailand, China, etc.). A total of 400 fish specimens were collected from three sites on three different rivers in Uttar Pradesh, India. Feeding habits, feeding intensity, gonadosomatic index, fecundity, maturity stages based on macroscopic studies, and sex ratio were examined. C. striata was found to be a carnivorous species (dominantly piscivorous). The feeding intensity varied according to season and fish size, with a higher intensity being observed during pre-spawning and post-spawning seasons. The reproductive biology of the striped snakehead from the Gangetic River system demonstrated that the gamete maturation occurred during May to July. The fecundity of C. striata ranged from 3652 to 48,450 eggs. Fecundity was linearly correlated with body length, body weight, and ovarian weight. The average ratio of males to females was observed to be 1:3.2.

Modeling the variable transmission rate and various discharges on the spread of Malaria

&lt;abstract&gt;&lt;p&gt;Natural and household discharges are the natural breeding grounds of various mosquito species, including female &lt;italic&gt;Anopheles&lt;/italic&gt; mosquitoes, which transmit the &lt;italic&gt;Plasmodium&lt;/italic&gt; parasite, causing the spread of the life-threatening disease malaria. Apart from that, population migrations also have a substantial impact on malaria transmission, claiming about half a million lives every year around the world. To assess the effects of the cumulative density of households and other natural discharges, and emigration-dependent interaction rates on the dissemination of the vector-borne infectious disease malaria, we propose and analyze a non-linear mathematical model. The model comprises five dependent variables, namely, the density of the susceptible human population, the density of the infective human population, the density of the susceptible female &lt;italic&gt;Anopheles&lt;/italic&gt; mosquito population, the density of the infective mosquito population and cumulative density of household and other natural discharges. In the model, the density of the mosquito population is supposed to follow logistic growth, whose intrinsic growth rate is a linear function of the cumulative density of household and other natural discharges. The nonlinear model is analyzed by using the stability theory of differential equations, numerical simulations and sensitivity analysis. The analysis shows that an increase in non-emigrating population causes increased incidence of malaria. It is also found that an increase in household and other natural discharges accelerates the occurrence of malaria. A basic differential sensitivity analysis is carried out to assess the sensitivity of model solutions with respect to key parameters. The model's numerical simulations demonstrate the analytical findings.&lt;/p&gt;&lt;/abstract&gt;

Consumers' willingness to pay premium under the influence of consumer community culture: From the perspective of the content creator.

With the rise of live streaming commerce, the relationship between consumers and content creators on the short-video platforms has become closer, forming a peculiar culture and language in each consumer community, which promotes the short-video platforms to become a natural breeding ground for forming consumer communities. While such communities give birth to its own language and culture from the interaction between content creators and consumers, this kind of co-creation can not only enhance the consumers’ trust to improve commodity premium space, but also strengthen the ties within the community and spread the information outside the communities, and consequently, expand community scale. Based on the view of the value co-creation from the language and culture among content creators and consumers in the communities, this study starts from the point of product type, employs consumers’ Willingness to pay premium (WoPP) as a proxy variable of brand advocacy in the co-creation of cultural and language values in consumer communities, and conducts three single-factor experiments between two groups. By analyzing the experimental results, this study identified the influence under the potential relationship mechanism, social comparison, and found another variable that can moderate the relationship, consumer trust, portrays the relationship between the product types of the live streaming commerce and the consumers’ WoPP, and explores the mediating effect of social comparison and the moderate effect of consumer trust effect. This paper also analyzes and discusses the WoPP caused by the co-creation of cultural and language values co-created by creators and consumer communities.

Impact of environmental stressors on the phytoplankton communities to assess the River Halda, Bangladesh

Halda is a 98 km-long tidal freshwater river of Bangladesh, which has a unique feature since it is the only natural breeding ground and the sole source of fertilized eggs of Indian Major Carps globally. The present study firstly summarizes the impact of environmental stressors to understand phytoplankton abundance, community, and their diversity in Halda River, Bangladesh. Environmental data as seasons (Winter, Monsoon), water depths, temperature, pH, Salinity, dissolved oxygen, and nutrients were collected and analyzed from the Halda River in January 2019 and August, 2020. Thirty-four phytoplankton genera, comprising five classes, were identified from the Halda River, Bangladesh. A two-way ANOVA was performed to analyze the effect of Monsoon and Winter on the physicochemical and biological parameters. It revealed that there was a statistically significant ((F9, 160)= 34.999, p= 0.0) interaction between Monsoon and Winter on the observed parameters. The water temperature (F 125.31, Fcrit 4.130, p= 0.0) and nutrients (F 11.118, Fcrit 2.322, p= 0.0) revealed significant change in the phytoplankton concentrations in the Halda River. As of the temperature and nutrients, water depths also significantly (F 1.790, Fcrit 1.719, p= 0.0) affect the phytoplankton communities in the Halda River showing the highest and lowest cell density in the surface and bottom water, respectively.

Production Trends, and Challenges for Biodiversity Conservation and Sustainable Fisheries Management of Kaptai Lake, the Largest Reservoir in Bangladesh

Kaptai Lake (KL), the largest artificial lake in Bangladesh, supports an important inland open water fishery. Nevertheless, detailed studies on its fish diversity and environmental threats are still limited. Hence, a study was conducted to evaluate the current fish management scenarios, fish production, relative abundance to improve the production and biodiversity of KL. Data were collected from stakeholders through personal observation, focus group discussions, and cross-check interviews from September 2018 to July 2019. The fish production of KL increased from 1,200 metric tons (MT) in 1965–1966 to 10,577 MT in 2018–2019. The output of the lake was dominated by small fish remarkably, Gudusia chapra (Hamilton, 1822), Gonialosa manmina (Hamilton, 1822), and Corica soborna Hamilton, 1822, accounting for 64 % of the total production in 2018–2019. A total of seventy-six fish species were observed under ten orders, including seven exotic fish species. According to the IUCN Bangladesh, 14 % of total species were identified as vulnerable, 11 % as endangered, 3 % as critically endangered, 11 % as near threatened and 51 % as least concern. The study also identified that climate change and various human-driven causes threaten the fish production and biodiversity of this lake. These findings suggest that community-based fisheries management, protection of natural breeding grounds of carps, control of pollution, amendment of existing fishing laws, and collaborative research would be a necessary approach for mitigating the negative environmental impact of this lake. The overall practical knowledge of this investigation could assist in policymaking and further research.

Contamination levels and ecological risk of heavy metals in sediments from the tidal river Halda, Bangladesh

The study assessed the contamination level of seven heavy metals (Pb, Cd, Cr, Ni, Zn, As, and Cu) along with their potential ecological risks in sediments from the Halda river which is the largest natural carp breeding ground in South Asia. The concentration levels (mg/kg) of seven heavy metals from ten sampling sites were organized in the following descending order: Zn (71.89) > Cr (31.86) > Cu (31.85) > Ni (26.67) > Pb (20.46) > As (2.69) > Cd (0.05). Among the metals, Zn, Cr, Ni, and Cu exceeded some standard limits. Sediment quality guidelines (SQGs) suggested that the concentration of Pb, Cu, and Ni could occasionally cause an adverse effect on the ecosystem. However, the geo-accumulation index (Igeo), contamination factor (CF), and pollution load index (PLI) for heavy metals suggested that the contamination level was low. Moreover, the risk index (RI) and potential ecological risk index ( $$ {E}_r^i $$ ) confirmed the low ecological risk (as RI < 100 and $$ {E}_r^i $$ < 30) from heavy metals for the river ecosystem except for the Pb and Cu. High CF and $$ {E}_r^i $$ values for Pb in one site (S4) are deemed as combining elements of multiple metallic portions used in industrialization. The univariate and multivariate statistical analyses such as correlation matrix, principal component analysis, and cluster analysis of the metals for different sites signified that the metals were originated from similar anthropogenic activities like untreated industrial effluents and wastage disposal to the river system.

Heavy metal contamination and ecological risk assessment in water and sediments of the Halda river, Bangladesh: A natural fish breeding ground

This study reports the mass fractions of Al, Cr, Mn, Fe, Co, Zn, As, Ni, Cu, Cd, Hg, and Pb in water and sediments of the Halda river, Bangladesh, and studies the distribution, contamination, and potential ecological risks of the metals and metalloid. The average mass fractions of As, Cd, and Pb are relatively higher in sediments compared to those in background values, whereas Al, Fe, Mn, and Pb concentration fractions in water are higher than the international guideline values. The results of the different contamination indices indicate that Halda river sediments are minorly contaminated by As and Pb and moderately to considerably contaminated by Cd. The ecological risk assessments indicate considerable to high ecological risk due to Cd. Multivariate statistical analysis reveals the origin of the contaminants in the river, and indicate that Cr, Zn, Pb, and Cd are from anthropogenic activities while the other metals originate from natural lithogenic actions.

KARAKTERISTIK DAN POLA SEBARAN PHYTOTELMATA SEBAGAI TEMPAT PERINDUKAN ALAMI NYAMUK DI KEBUN RAYA LIWA LAMPUNG BARAT

Kebun Raya Liwa (KRL) adalah kawasan konservasi tumbuhan ex-situ yang memiliki banyak koleksi tumbuhan sehingga akan berdampak pada banyaknya jenis tanaman phytotelmata. Phytotelmata adalah tanaman yang pada bagian organnya dapat menampung air dan dimanfaatkan berbagai organisme termasuk nyamuk sebagai tempat perindukan alami. Tujuan penelitian adalah untuk mengetahui karakteristik phytotelmata dan pola sebaran phytotelmata di Kebun Raya Liwa, Lampung Barat. Penelitian ini dilaksanakan pada bulan November 2019 – Januari 2020 di Kebun Raya Liwa dan Laboratorium Botani Universitas Lampung. Metode penelitian dilakukan secara deskriptif dengan pendekatan metode survey. Data yang diperoleh ditampilkan dalam bentuk tabel dan gambar. Hasil penelitian menunjukan terdapat 7 jenis phytotelmata di Kebun Raya Liwa yaitu Nepenthes mirabilis, Cyathea coopei, Bambusa sp. Areca catechu, Musa sp. Colocasia gigantea, dan Crynum asiaticum dengan 2 pola sebaran phytotelmata yaitu berkelompok dengan nilai IP berkisar antara 0,813-1,194 dan pola sebaran secara seragam dengan nilai IP -2,08.Kata Kunci: Phytotelmata, Tempat Perindukan Alami, Kebun Raya Liwa

Linking weir imprints with riverine water chemistry, microhabitat alterations, fish assemblages, chlorophyll-nutrient dynamics, and ecological health assessments

Abstract The weir construction in larger rivers has displayed harmful impacts due to unpredicted modifications in hydrology and microhabitats. This study illustrated the impacts of three massive weirs installed in the mainstream Geum River, South Korea. We used the modified multimetric index of biotic integrity (mmIBI) and water pollution index (mmWPI) to understand the imapcts of weir installations on riverine water chemistry and fish assemblages. The results divulged seasonal and spatial heterogeneities by indicating the gradual degradation of water quality. Phosphorus and sediments displayed an excessive influence of seasonal rainfall patterns. The nutrients (N, P) showed week relationships at weir (GW: R2 = 0.21, SW: R2 = 0.12, BW: R2 = 0.25), but stronger links in the upstream river (R2 = 0.74) sites. The mmWPI revealed the weir sites and riverine zones into ‘fair to very poor’ water quality status, while mmIBI specified the sites in ‘fair to poor’ ecological health. Overall, 60 fish species sampled as 64,637 individuals were observed, indicating 81.24% of individuals at the weir sites. Squalidus japonicus coreanus (18.47% RA) and Hemibarbus labeo (9.25% RA) were relatively the most abundant fish species in this investigation. The total number of fish species and individuals gradually declined along the river gradient. The principal component analysis (PCA) grouped the dominant factors by distinct riverine zones, with a percent cumulative variance of 81.80%. The tolerant and omnivorous fish species were established in aggregations in downstream, with increased insectivorous species. In conclusion, the impacts of weir installation were assiduously manifested and indicted an exceedingly deteriorating water chemistry that could have caused a decline in sensitive species, favored the tolerant species, and overall reduced the habitat quality suitable as natural breeding and feeding grounds. Furthermore, the declining fish assemblages and their distribution, perturbed microhabitat conditions, and inclusively deteriorating ecological health status were linked to the weir imprints.

Effects of the China Coastal Current on the community structure of planktonic copepods in early spring, with notes on Eurytemora pacifica Sato, 1913 in the western Taiwan Strait

Abstract The Taiwan Strait, located between Taiwan Island and the southeast of the mainland of China, is the main passageway connecting the East China Sea and the South China Sea. The particular coastline of the mainland created several semi-enclosed embayments along the west coast of the Taiwan Strait. Runoffs from land bring large amounts of nutrients into the bays, which made these bays important natural spawning and breeding grounds for several economically important marine organisms. In order to reveal the effects of the China Coastal Current (CCC) on the zooplankton communities in Fuqing Bay in northeastern Fujian, zooplankton samples were collected at 12 stations in early March 2014. The average surface seawater temperature was 12.53 ± 0.14°C, and salinity was 28.33 ± 0.21 PSU in the investigation area during the research period. In total, 23 identified copepod species and in addition several unidentified benthic harpacticoid copepods were recorded with an average abundance of 77.44 ± 60.07 ind. m−3. In the present study, the most dominant group consisted of juveniles (copepodites) with an average density of 59.97 ± 51.49 ind. m−3, which was followed by Calanus sinicus Brodsky, 1965 with an average density of 5.04 ± 4.95 ind. m−3. The occurrence rate of Calanus sinicus was 91.67% in our study, which indicates that the research area was controlled by the CCC water mass. So, we concluded that the CCC played an important role in transporting cold water copepod species from the Bohai Sea and the Yellow Sea to the western Taiwan Strait. A noteworthy discovery in our samples was Eurytemora pacifica Sato, 1913, which was recorded for the first time in waters of the western Taiwan Strait with an occurrence rate of 33.33% and an average density of 0.81 ± 1.91 ind. m−3. Eurytemora pacifica was first reported at Yantai harbour and is widely distributed in waters of the northern Pacific Ocean. The co-occurrence of Calanus sinicus and Eurytemora pacifica in our research area possibly indicates that E. pacifica could be used as a bioindicator for the directional movement of the CCC. The high occurrence of this species in our research area indicated that the CCC affects the community structure of copepods in the western Taiwan Strait in early spring.

A sustainability analysis on the trends and frequency of the channel flow of a carp breeding river against human interventions and governing public–private partnership (PPP) as adaptation

This study presents the trends of channel flow against human interventions and proposes an adaptation plan through a public–private Partnership (PPP) model to overcome the existing deteriorating condition of the Halda River. Being the only natural carp breeding ground in Bangladesh, the Halda River is significant for the national economy. However, the river’s destiny is now stricken with infrastructural obstructions, industrial and residual usage exploits, and short-sighted interventions, whereas the impacts of climate change are likely to worsen the scenarios with high salinity intrusion. The unplanned human interventions due to agricultural purposes are continuously obstructing the river flow and demolishing the carp habitats and spawning within the Halda River extremely. Most of the river bends are potential carp breeding grounds along the river stretch, and the low river flow during pre-monsoon is also impacting the sustainability of the aquatic eco-system. To understand the issues behind the endangering Halda River, this study conducted a sustainability analysis through the river planform, stage trend, and frequency analyses. The planform analysis showed the encroachment of the river impacting the river bends, significant for aquaculture over the last three decades, whereas the stage trends showed the low availability water scenario in these four locations of the river stretch. Besides, the frequency analysis reviewed the threshold minimum flow for the survival of the aquatic habitat, showing that the flow during the pre-monsoon is unsuitable and unacceptable for the survival of the fish habitats using Gumbel distribution. Conservation of the Halda River is a national priority due to its unique ecological and commercial importance, and it is expected that the proposed PPP framework will ensure the long-term sustainability of the river ecosystem. This article is analysing the existing situation of the Halda River and proposing a joint effort from government and private organisation through the PPP model for sustainable ecosystem management as well as the economic benefits of the country. Working together, each of the stakeholders will find direct benefits and can be instrumental for the survival of the Halda River.

A baseline taxonomic study of zooplankton in the lower Halda River, Bangladesh

Halda is a unique resourceful tidal river of Bangladesh, where Indian major carps (Catla catla, Labeo rohita, Cirhinnus mrigala, and Labeo calbasu) spawn from April to June. Ecological conditions are auspicious from time immemorial which serves as a natural breeding ground in the world. The present study was conducted over the period of January-June 2017 to identify the main species of Zooplankton fauna and also fi nd out the dominancy of the highest plankton groups in the lower Halda River. A total of 3 major zooplankton groups-Copepoda, Rotifera and Cladocera were identifi ed during the six months period. A total of 35 species under 4 family showing the dominancy for the class Rotifera consisting of 7 genera were recorded from fi ve sampling sites. The lowest group was Cladocera consisting of 5 genera. The composition and dominance of the zooplankton community among fi ve different sites in the lower Halda River showed some close inter-relationships. The present study suggests for conducting further research to know the overall conditions and to make a complete list of available zooplankton fauna that exert impact on the water quality of the Halda River.

Meditations on a Monkey-Face: Monsters, Transgressed Boundaries, and Contested Hierarchies in a Yiddish Eulenspiegel

This paper discusses an early-eighteenth-century Yiddish translation of the famous early modern Schwankroman (jest-novel), Eulenspiegel . The uniqueness of the translation lies in its incorporation of five distinct tales, which do not appear in any other extant Jewish or non-Jewish edition. Four of these original tales feature monstrous creatures, such as cynocephali (dog-headed men), strong, venomous women, and monkey-faced men. The article offers a close reading of these monstrous creatures, revealing how they serve to unpack concerns surrounding problems of transgressed borders and confused hierarchies, which were shared by many of the unnamed Yiddish translator's Jewish and non-Jewish contemporaries. I offer a review of these anxieties, locating them against their wider cultural background, and tracing their unique manifestations within the Jewish—and particularly Yiddish—literary realm. I argue that there was something special about writing monstrosity in Yiddish, and particularly in a Yiddish translation of a German work. A hybrid genre, formed by the unnatural coupling of separate tongues, literature, cultures, classes, and genders—Yiddish literature was a monstrous creation in its own right; an almost natural breeding ground for monsters.

Indirect and Non-use Values of Halda River- A Unique Natural Breeding Ground of Indian Carps in Bangladesh

Bangladesh is a Riverine country; however, Halda River is of special interest among them in recent time for being the only tidal freshwater River in the world that serves as a natural spawning ground for major Indian carps. Besides, this River serves some indirect and non-use values. This study aims at estimating the economic worth of the indirect and non-use value of Halda River. Both indirect and non-use values of this River were calculated by using contingent valuation method. The study found that total indirect use value per year from this River was Tk. 29.50 million. We also estimated that total non-use value was Tk. 31.46 million which comprised of bequest value of Tk. 14.85 million and option value of Tk. 16.61 million. The study suggests that this valid source of information should take into consideration for the decision makers in taking projects and programmes aimed at managing this River more wisely in the future.DOI: http://dx.doi.org/10.3329/jesnr.v6i2.22092 J. Environ. Sci. &amp; Natural Resources, 6(2): 31-36 2013

"How Emotions Shape Team Functioning: Implications for Conformity, Compensation, and Conflict"

People spend a considerable proportion of their lives working in teams. Team work is a natural breeding ground for emotions. These emotions are not only experienced, but often also expressed in the...

Controlled Breeding of Asian Catfish Clarias batrachus using Pituitary Gland Extracts and Ovaprim at different Temperatures, Latency Periods and their Early Development

Present study was conducted on induced breeding of commercially important Clarias batrachus due to the non-availability of its quality seeds from the natural resources for environmental degradation, shrinkage of natural breeding ground and illegal killing of juveniles and brood fishes. The aim of the study was to achieve success in fertilization and hatching using various doses of different inducing agents at different temperatures and latency periods followed by stripping method. In this study the developmental stages of fish (fertilized egg to 45th day old fish) were characterized chronologically. A trial was also made to optimize the survival rate of young developing fish upto 45th day by manipulating their feeding schedule and environmental conditions. The breeding experiments were done with pituitary gland extracts (40 and 120 mg/kg. body weight for female and 25 and 50 mg/kg. body weight for male) and Ovaprim (0.8 and 2.0 ml/kg body weight for female and 0.4 and 1.0 ml/kg body weight for male) at 26o, 28o and 30oC. The highest rates of fertilization (80%) and hatching (71%) of eggs were recorded in Clarias batrachus injected with carp pituitary gland extracts @ 50 mg/kg body weight of male and 120 mg/kg body weight of female at 28oC with a latency period of 15 hours. The fertilization and hatching rates were 77% and 65% respectively at 28°C at the higher doses of Ovaprim. The highest survival rate (82.5%) of developing fish was achieved supplying zooplankton as live feed upto 12th day followed by alternate supply of zooplankton, boiled egg with vitamin C and chopped tubifex from 13th to 45th day of rearing in indoor polyvinyl chloride tray with minimum fluctuation in temperature and dissolved oxygen.

Variability in the trophic position of larval fishes in theupper Paraná floodplain based on δ15N

The upper Paraná River floodplain is composed of several marginal lagoons, making it a natural breeding ground for many fish species at developmental stages. The aim of this study is to estimate the trophic positions of these fishes based on feed intake (measured via diet) and nitrogen assimilation (measured via δ(15)N). The monthly samplings were concentrated during the spawning season in the Ivinheima River, which is located in the upper Paraná River floodplain. The specimens were grouped into preflexion, flexion and postflexion stages. Trophic positions were estimated based on the isotope value of nitrogen and on diet. During the developmental stages of P. squamosissimus, there were significant differences in the isotope values of δ(15)N; for H. edentatus, however, no significant differences were found. During the developmental stages, both species were classified as either at or above the third trophic level. Once this information is obtained for other species and components of the ecosystem, it will not only provide a more precise view of the energy allocation and flow in the ecosystem, but will also make possible for management measures to promote sustainability in this environment.