Fish Composition Research Articles

Climate Change Affects Multiple Coral Reef Fisheries Ecosystem Services

ABSTRACTCoral reef fisheries support livelihoods and provide an affordable source of essential dietary nutrients to coastal people. However, climate‐driven coral bleaching is dramatically altering reef habitats and changing reef fish composition, diversity, and productivity. We used data from fisheries independent surveys and artisanal trap landings to explore how reefs with different responses to coral bleaching differed in habitat configurations, fisheries catch rates, economic returns, and nutritional content. Coral‐associated fishes supported the highest catch rates, greatest species diversity, highest rates of economic returns for fishers, and a wide price range for consumers. Macroalgae‐associated fishes supported the greatest overall fisheries yields, which indicated higher fishery dependence on these habitats. Nutrient content was high in catches across all habitats, but concentrations varied by nutrient, which suggested that fishing across a range of reef habitats should provide the greatest variety of nutrients to coastal communities.

Associations Between Gut Microbiota Diversity and a Host Fitness Proxy in a Naturalistic Experiment Using Threespine Stickleback Fish.

The vertebrate gut microbiota is a critical determinant of organismal function, yet whether and how gut microbial communities affect host fitness under natural conditions remains largely unclear. We characterised associations between a fitness proxy-individual growth rate-and bacterial gut microbiota diversity and composition in threespine stickleback fish introduced to large semi-natural ponds. We detected a 63% higher richness of bacterial taxa (α-diversity) in the guts of high-fitness fish compared to low-fitness fish, which might be driven by stronger bacterial dispersal among high-fitness fish according to the fit of a neutral community model. Further, microbial communities of high-fitness fish were more similar to one another (i.e., exhibited lower β-diversity) than those of low-fitness fish. The lower β-diversity found to be associated with higher host fitness is consistent with the Anna Karenina principle-that there are fewer ways to have a functional microbiota than a dysfunctional microbiota. Our study links differences in α- and β-diversity to a fitness-related trait in a vertebrate species reared under naturalistic conditions and our findings provide a basis for functional tests of the fitness consequences of host-microbiota interactions.

Seasonal and Spatial Distribution Patterns of Non-Native Fishes in Inland Waters of Guangxi

Fish invasions can damage the ecological environment of invaded areas, causing negative effects such as monotony of ecological types in invaded waters and endangerment of native species. It is important to monitor their presence and spread in invaded areas. This study aims to update the available data on non-native fish species in the inland waters of Guangxi and to determine their seasonal and spatial distribution in this region. Taking the inland waters of Guangxi as the study area, 34 sampling sites were set up in the major river systems, and systematic sampling was conducted in four seasons in 2023. The data showed that a total of 7690 non-native fish were collected from 23 species, belonging to 7 orders, 13 families, and 20 genera. Of the non-native fish species, 19 species were introduced for aquaculture purposes, and three species were introduced for ornamental purposes. The most non-native fish species were found in summer with 21 species, which were followed by 20 species in winter, 18 species in spring, and only 15 species in autumn. However, the distribution composition was similar in each season, with Coptodon zillii being dominant in each season, which was followed by Oreochromis niloticus. The Hongshuihe River had the highest number of non-native fish species with 16 species, followed by the Xunjiang River with 14 species, the Qianjiang River with 13 species, and the Npanjiang River had the lowest number of non-native fish species with 7 species. In addition, the Xunjiang River and the Qianjiang River showed significant separation in the PCoA results, and the overall test showed significant differences in non-native fish composition among the river system. The main reasons for the differences in their spatial distribution are geographical location and temperature. O. niloticus and C. zillii were found in all river systems and have become the main invasive non-native fish species in the inland waters of Guangxi.

Microcystin exposure alters gut microbiota composition in fish: An in-Situ analysis of post-bloom effects in Hulun Lake, China

Cyanobacterial blooms are one of the most common stressors aquatic plants and animals encounter in freshwater ecosystems such as rivers and lakes. Following such outbreaks, some cyanobacteria release toxins, notably microcystins, which are highly toxic. Although numerous studies have explored the effects of microcystins on fish, their in-situ effects on the fish gut microbiome remain unexamined. Our objectives were to examine the fish gut microbiome before (Ju) and after (Au) cyanobacterial blooms and to monitor water quality. We collected Ju and Au fish gut and water samples from Hulun Lake. Using 16S rRNA full-length sequencing, we analyzed the composition, structure, and function of the fish gut microbiome. Results revealed significant disparities in microcystin concentrations between the Ju and Au water samples. In addition, the microcystin concentration in the carp gut was significantly higher than that in its muscle after the cyanobacterial bloom outbreak. Notably, the Au group demonstrated an increase in the microcystin level in water and a marked reduction in fish gut microbiota diversity compared with the Ju group. The cyanobacterial bloom decreased gut microbiome diversity in fish, with the Au group exhibiting a significantly reduced abundance of bacteria related to gut stability and microcystin degradation compared to the Ju group. Furthermore, we observed an upregulation of disease-associated bacterial metabolic functions in the Au group. In conclusion, these findings suggest that microcystins influence the composition and function of fish gut microbiota, improving our understanding of the interaction between fish gut microbiome and their environment. This study offers new perspectives on the adaptive mechanisms of aquatic organisms to cyanobacterial blooms.

Seasonal variations of vitamins A, E and carotenoids in eelpout (Zoarces viviparus) from a Danish fjord, in relation to reproductive cycle

Retinoids (vitamin A) and tocopherols (vitamin E) are essential for key biological functions in vertebrates, including cell growth, cell death and differentiation, embryonic development, reproduction and vision. In fish, however, much less is known about the retinoid functions, although retinoic acid has been shown to be involved in embryonic development. In this study, we quantified the levels of different retinoids, carotenoids and vitamin E in various tissues of both adult and embryos of the viviparous fish eelpout (Zoarces viviparus). Our results demonstrate clear seasonal differences in the levels of these vitamins in the liver of the female fish as well as in its ovarian tissues, eggs and/or embryos. Overall, this study is a baseline assessment and describes the annual variations in the vitamin status by comparing the tissue distribution of retinoids, carotenoids and vitamin E. This baseline study investigates the natural background levels of these compounds and relates their seasonal fluctuations to the reproductive cycle in the viviparous eelpout. The results of this study strengthen the current evidence base necessary to understand retinoid pathways during fish development. This understanding is crucial for utilizing retinoid composition in fish as a biological response to exposure to environmental pollution with hazardous substances in the marine environment.

Age, Growth, Sex Composition, and Diet of the Burbot, Lota lota, the Only Freshwater Species of the Family Lotidae in the Amur (Heilongjiang) River, Northeast China

Information about the population structure, including the age and sex composition, growth characteristics, and diet of fish, is essential for the conservation and sustainable exploitation of fish stock. The burbot, Lota lota, is the only freshwater species of the family Lotidae in the Amur (Heilongjiang) River catchment located in northeastern China. Information on the biological characteristics and data on the population structure of this fish from the Amur River are scarce. To study these factors in burbot, Lota lota, in the Amur River of China, 749 specimens from four sampling areas were taken and analyzed in October 2022, January 2023, and May 2023. The ages of the sampled fish ranged from 1+ to 7+ years. The female/male ratio was 1.04:1, and body length and mass varied from 175 to 595 mm and 73.5 to 1958.7 g, respectively. The length–weight regression parameter b value was estimated as 2.80. The parameters of the von Bertalanffy growth model were L∞ = 596, K = 0.221, and t0 = −0.771 for all sampled fish; L∞ = 625, K = 0.208, and t0 = −0.756 for females; and L∞ = 584, K = 0.219, and t0 = −0.980 for males. The analysis of the stomach contents showed fish to be the major source of nutrition across all areas and sampling periods. In January, the secondary prey of burbots in the Huma reach of the upper Amur River was aquatic insect larvae, while, in the Tongjiang and Fuyuan reaches of the middle Amur River, the secondary prey was shrimp. The mean stomach fullness index and rate of empty stomachs differed with the sampling area, with the greatest proportion of empty stomachs observed in the Luobei reach of the middle Amur River, and the lowest in the Tongjiang and Fuyuan reaches. The mean stomach fullness index showed the opposite trend. In the Huma reach, the contributions of fish to the diet and the mean stomach fullness index were significantly higher in May than in October and January. The study provides the first detailed information on the population age and sex structure, growth patterns, and feeding ecology of burbots from the Amur River, China. The results will aid in formulating management strategies and regulations for local populations of burbots in the Amur River, China.

Bovine bone meal combined with dephenolized cottonseed protein is an effective fishmeal substitution in Trachinotus ovatus feed: A comprehensive evaluation of growth, muscle quality, and intestinal digestion physiology

To investigate the feasibility of substituting fishmeal (FM) with a combination of bovine bone meal (BBM) and dephenolized cottonseed protein (DCSP), a mixture (consisting of 60 % BBM and 40 % DCSP) was used to replace varying FM levels in Golden pompano (Trachinotus ovatus) feed. Five isoproteic (47 %) and isolipidic (12 %) experimental diets were formulated, with FM levels set at 30 %, 24 %, 18 %, 12 %, and 6 % (namely Control, FM24, FM18, FM12, and FM6). To compensate for the reduced FM content, BBM and DCSP were used as substitutes, and DL-methionine and L-lysine were added to maintain the dietary amino acid balance. Following a 63-day trial, results showed that the growth of FM24, FM18 and FM12 groups did not exhibit significant differences compared to the Control group, while those of FM6 group considerably decreased. The biochemical composition of whole fish did not display significant differences among the five groups, while the muscle protein contents of the FM12 group were higher than the Control group. Most of the muscle texture properties were positively modified in the FM 12 and FM 6 groups. With the substitution ratio increase, the contents of serum total protein, albumin, total amino acids, and cholecystokinin were elevated, while serum peptide YY contents decreased. In addition, intestinal trypsin, NaK-ATPase, and alkaline phosphatase activities in FM18, FM12, and FM6 groups decreased, and lipase activities exhibited the opposite trend. The transcription levels of genes related to amino acid-sensing receptors (asct2 and snat2) were down-regulated with increasing dietary FM substitutions, while the expression levels of appetite regulation factors (pept1, cck, and ghrl) were up-regulated. In conclusion, the FM content in the diet of T. ovatus can be reduced to 12 % through the utilization of a combination of BBM and DCSP, with no adverse effects observed on growth performance, biochemical composition, or muscle texture.

Bioresources of lake Mostovoye and ways of their rational use

The ichthyofauna of most water bodies in the Altai Krai is represented by low-value and slow-growing fish. Fish productivity is largely determined by the degree of exploitation of the reservoir and the form of organization of the fishery. Rational fishery in natural reservoirs should ensure the exploitation of the ecosystem of the reservoir as a single whole. Mostovoe Lake is located in the Zavyalovsky and Baevsky districts of the Altai Krai, is one of the largest freshwater lakes in the Altai Territory, belonging to the floodplain of the Kulunda River. The water in the reservoir is of the sulfate-chloride class of the first type, fully meets all fish farming requirements. The collection of ichthyological material was carried out by the method of control catches. The species composition and spatial distribution of fish were studied by setting a set of fixed gill nets in the reservoirs. Information on the size and age structure of populations, catches of the main commercial fish and crayfish in Mostovoe Lake is provided. The magnitude of the fishing effort and the assessment of the state of aquatic bioresources (ichthyofauna) in the reservoir were carried out using one of the expert assessment options — the point systems method. The ichthyofauna of Mostovoe Lake includes six species that are subject to commercial fishing: common pike, roach, silver carp, river perch, common carp (carp), and common pike perch. Of the commercial invertebrates, crayfish is caught. The indicators of the commercial stock and the recommended catch of bioresources in the reservoir were calculated. Recommendations for regulating fisheries based on ichthyological monitoring are proposed. A certain effect for stabilizing the structure of the ichthyocenosis of the reservoir can be made by fishery melioration: the introduction of herbivorous fish — white amur (Ctenopharyngodon idella) and silver carp (Hypophthalmichthys molitrix) for a more complete use of the food base of the lake — phytoplankton and macrophytes. It is necessary to continue monitoring studies of the lake’s winter oxygen regime.

Condition states in anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) revealed by energy and proximate composition relationships.

Energy content has long been proposed as a fundamental, integrated, and reliable indicator of the condition of individuals as it reflects past bioenergetics and influences future life-history traits. There is a direct biochemical link between energy density and body composition described by four main compounds in fish (protein, lipid, ash, and water), with proteins and lipids being the sources of energy. If relationships between water content, or lipid content, and energy density have been well described in relative terms, the absolute mass variations in the proximate composition have been overlooked and thus their interpretation is often equivocal. In our study, based on a large and unique dataset on the proximate composition and energy density of anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) from sampling in the Bay of Biscay and the English Channel, we aimed to better explain the patterns between water content and other proximate components or energy density, based on the dynamics of proteins, lipids, and water absolute masses. For the first time, we defined good, intermediate, and poor condition states in wild fish, based on water content, corresponding to the different dynamics of lipids and proteins in the metabolism of individuals. Anchovy and sardine exhibited remarkably similar patterns of variation in the compounds and in the limits between the condition states with respect to water content. Those patterns revealed that water mass remained constant for a given fish size whatever its condition state, and that variability in water content only resulted from the variation in lipid and protein masses. Furthermore, the differential dynamics of proteins and lipids, with only lipids mobilized in the good condition state, only proteins in the poor condition state, and both proteins and lipids in the intermediate condition state, elucidates the nonlinear pattern observed in the relationship between energy density and water content. Overall, our results highlight the importance of monitoring the intraspecific variations in water content to predict the proximate composition and energy content in small pelagic fish and better assess individual and population conditions in changing ecosystems as well as to better parameterize bioenergetic models.

Proximate and Amino Acid Composition of Freshwater Fish of Nagpur, Maharashtra, India

Background: The study aimed to evaluate proximate and amino acids profile of selected freshwater species from Nagpur, India. Nutritional composition of calbasu (Labeo calbasu), silver carp (Hypophthalmichthys molitrix), tilapia (Oreochromis niloticus) and pangasius (Pangasianodon pangasius) was investigated to make aware the consumer about the present nutrient composition of these fish. Methods: Iced Calbasu, Silver carp, Tilapia and Pangasius fish were procured from Mayo fish market, Nagpur, Maharashtra, India and brought to the laboratory of Fish Processing Technology, College of Fishery Science, Nagpur. The marketable sized (average weight of 0.5-1.3 kg) fish were used for evaluation of proximate composition the methods of AOAC (2005). The amino acids profiling of fish samples were assessed by using High Performance Liquid Chromatography (HPLC, Shimadzu LC-6A). Result: The variation (p less than 0.05) in nutrient composition viz. proximate and amino acids of these fish mainly due the effect of feed composition, feeding habits, geographical condition and availability of feed etc. The major components of proximate composition, moisture (75.75-77.53%), protein (14.52-18.01%), lipids (2.45-6.71%) and ash (1.10-2.09%) were recorded. The protein content was relatively stable in all species. The carbohydrate was found to be lower than 1.5%. The energy value of the fish species was between 94.81-123.51 Kcal. The pangasius had higher energy value due to high amount of fat content. During the study, the concentrations of essential amino acids (EAA) in all fish species ranged from 25.48 g/100 g to 29.41 g/100 g, while amounts of non-essential amino acids (NEAA) ranged between 27.94 g/100 g and 31.27 g/100 g. Lysine (5.14-6.31 g/100 g) and glutamic acid (6.26-8.72 g/100 g) were the most predominant amino acids found in EAA and NEAA respectively in all species. The higher level of essential amino acids was found in tilapia fish followed by silver carp, calbasu and pangasius. The results of the present study revealed that, all species have high nutritional value in terms of proximate and amino acids to offer positive health benefits upon consumption.

Investigating the effects of microplastics on the metabolism of Trematomus bernacchii from the ross sea (Antarctica)

Microplastic pollution is a growing environmental issue, even reaching remote areas like the Arctic and Antarctic, posing threats to biodiversity and food chains. The present research represents a pioneering endeavor aimed at exploring the relationship between lipids and microplastics in 20 wild specimens of Trematomus bernacchii from the Ross Sea (Antarctica). Fish were grouped in MPs-ingested and MPs-free based on whether they had ingested microplastics. Raman spectroscopy revealed that contaminated fish samples contained from one to three different types of polymeric fibers (1.4 items/specimen, ± = 0.7), specifically, polyester (PES), polypropylene (PP), and polyethylene terephthalate (PET). Gas chromatography-mass spectrometry (GC–MS) and gas chromatography-flame ionization detection (GC-FID) techniques were employed for the study of the lipid composition in term of fatty acids methyl esters (FAMEs). Fifty different FAME compounds were identified and quantified in the lipid fraction extracted from the muscle tissues of the selected fish samples. Polyunsaturated fatty acids (PUFAs) are the most abundant family of fatty acids in T. bernacchii species with eicosapentaenoic (C20:5ω3) and docosahexaenoic (C22:6ω3) acids as main components. In detail, PUFA class accounted for 46.78 ± 6.82% and 44.62 ± 4.86% of the total fatty acid composition in MPs-ingested and MPs-free groups, respectively. The contents of the monounsaturated fatty acids (MUFAs) and saturated fatty acids (SFAs) varied from 27.93% to 31.15% and from 24.23% to 25.05% in MPs-ingested and MPs-free fish samples, respectively. Based on Mann-Whitney test results (p < 0.05), there was no significant difference from a statistical point of view between two groups of fishes. Additionally, nutritional quality indices exhibited comparable values between groups. Results showed that no significant differences were found in the fatty acids distribution between the two groups. This indicates that the lipid composition of wild fish that are naturally exposed to plastic pollution remains unchanged and could still have beneficial effects on human health.

Характеристика прибрежной ихтиофауны губ Восточного Мурмана в летний период 2021 года

In the article was considered species composition of fish in the littoral and sublittoral zones of Yarnyshnaya and Zelenetskaya bays (Barents Sea) during summer 2021. Also quantitative characteristics of the distribution for each fish species are represented. The dynamics of abundance and diversity of coastal fish communities were analyzed. At whole was discovered 12 species of fish and most abundent between them is young saithe Pollachius virens. Comparing of perennial data with 2021 indicates that at the present observed average species composition, fish distribution density, abundance of young Gadidae and indicators of biodiversity in coastal communities.

Species Composition, Abundance and Trophic Relationships of Juvenile Fish in the Vorogovskoe Mnogoostrovye (Yenisei River)

Species Composition, Abundance and Trophic Relationships of Juvenile Fish in the Vorogovskoe Mnogoostrovye (Yenisei River)

DNA barcoding and cryptic diversity in fishes from the Ili River Valley in China, Xinjiang.

The Ili River Valley, located in the northwest of China, serves as a vital repository for fish genetic resources. Its extensive water network and diverse climate have given rise to a unique fish composition and endemic species. In this study, we collected the cytochrome c oxidase subunit I (COI) sequences from 660 fish specimens in the Ili River Valley. The effectiveness of DNA barcoding in identifying fish species in the area was assessed by examining genetic distances, constructing phylogenetic trees, and performing ABGD (Automatic Barcode Gap Discovery) analyses, among other methods. In total, 20 species were identified, including one unidentified species (Silurus sp.). Except for Silurus asotus and Hypophthalmichthys molitrix (only one sample), the maximum intraspecific genetic distance among the remaining species was smaller than the minimum interspecific distance, which proves that the species exhibit obvious barcode gaps. In the Neighbor-Joining trees, 20 species formed separate monophyletic branches. According to ABGD analysis, 660 sequences were categorized into 19 Operational Taxonomic Units, with Silurus sp. and S. asotus grouped into a single OTU. The Silurus in this study exhibits shared haplotypes and significant genetic divergence, suggesting the potential presence of cryptic species. Furthermore, the nucleotide diversity across all species fell below the threshold level, indicating that the local fish population is gradually declining. In conclusion, this study has demonstrated the effectiveness of DNA barcoding in identifying fish species in the Ili River Valley, providing valuable data to support the conservation of local fish resources.

Assessing the effects of N-acetyl cysteine on growth, antioxidant and immune response in tilapia (Oreochromis niloticus) under different regimes of stocking densities.

The study investigated the impact of N-acetyl cysteine on growth, immune response, and antioxidant activity in tilapia (Oreochromis niloticus). Fish were reared at three densities (1.50, 3.00, and 4.50 kg/m3) with four levels of N-acetyl cysteine supplementation (0, 2, 4, and 6 mg/kg) over 60 days. Better growth was observed at low density, but at all densities, fish fed the highest N-acetyl cysteine level (6 mg/kg) showed improved growth. Chemical composition of fish and activity of amylase, lipase and protease in all treatments were noted to be insignificant. The levels of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and cortisol in HD treatments were high as compared to LD and MD treatment. However, fish fed with N3 diet in each density treatment showed the lowest level of antioxidant enzymes as well as cortisol. Similarly, the levels of malondialdehyde were noted to be high at HD treatments as compared to that in LD and MD. Its levels were lower in fish fed with N3 diets in all density treatments. Expression of somatostatins-1 did not increase in MD and HD treatments in response to high stocking density when compared with LD treatment. However, pro-opiomelanocortin-α level was reduced after N3 diet in HD treatment and interleukin 1-β expression increased after N3 supplement in HD treatment. In conclusion, N-acetyl cysteine supplementation improved growth and antioxidant response in tilapia. The most optimum dose of N-acetyl cysteine was noted to be 6 mg/kg at high stocking, suggesting the potential role of this nutraceutical in tilapia intensive culture.

Community Structure of Fishes the Association with Seagrasses at Bama Beach, Baluran National Park, Situbondo, East Java

Seagrass bed has an important role for biota in waters. The existence of fish in seagrass is influenced by other ecosystems close to seagrass, such as mangroves and coral reefs. This study focuses on fish associated with seagrass in Bama Beach. The data include seagrass coverage and the number of fish for the Diversity, Uniformity, and Dominance. The study was carried out on March 15 to 20, 2018 using the Underwater Visual Census. Results show that seagrass cover was highest in seagrass stations near mangroves (62,66%), while at stations near coral reefs was 37,66. The composition of fish associated with seagrass near mangroves was 361 individuals, while near reefs was 1.454 individuals. The values of diversity, uniformity, and dominance of fish associated with seagrass near mangroves are 2,62; 0,88; and 0,09 respectively while those associated with coral reefs have values of 2,93; 0,85; and 0,06. Family Aulostomidae was dominant in the morning at the station near mangroves, and in the afternoon was dominated by Apogonidae. At the station near coral reefs, the Family Pomacentridae was dominant both in the morning and afternoon. The seagrass conditions in this study are in the healthy category with quite diverse fishes. The level of fish diversity in seagrass was influenced by habitats associated with seagrasses than seagrass cover levels. The condition of Bama Beach as a conservation area is quite good, but the activity of tourists around the coastline must be monitored to maintain the environment.

Discarded blue mussel (Mytilus edulis): a feed ingredient that maintains growth performance of juvenile gilthead seabream (Sparus aurata) while fishmeal and fish oil are removed

ABSTRACT The total substitution of fishmeal (FM) and fish oil (FO) with sustainable feed ingredients, while maintaining acceptable growth performances and fish composition, is a challenge. Mussels have a high protein content, with essential amino acid and fatty acid (FA) profiles similar to those of FM. This study aimed to assess the potential to rear gilthead seabream (Sparus aurata) on a plant-based feed (without FM and FO) to which mussels were added. Subsequent effects on growth performance, protein content, and FA concentrations were studied. Juvenile gilthead seabream were reared for 46 days in water temperature of 21°C, in a recirculated aquaculture system composed of three fish tanks, each corresponding to one treatment: in the FMFO treatment, 342 fish were fed a commercial feed that contained FM and FO; in the plant-based feed (PBF) treatment, 345 fish were fed an experimental feed that contained only plant-based ingredients; in the mussel feed (MF) treatment, 342 fish were fed the feed from PBF supplemented with fresh mussel flesh from which the shells had been removed. Fish weighed a mean of 6.7 ± 1.3 g at stocking in each treatment. At harvest, the mean weight of fish from FMFO and MF were significantly different (23.1 ± 4.3 and 23.1 ± 5.2 g, respectively) than that from PBF (15.5 ± 3.6 g) (p < .05). Compared to the feed from FMFO, the feed from PBF decreased the percentages of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and saturated FA (14:0, 16:0) in fish, but increased those of 18:1, 18:2 n-6 and 18:3 n-3 FA. Compared to the feed from PBF, the feed from MF increased the EPA+DHA concentration in fish by 21%. Thus, adding fresh mussels to a plant-based feed yielded similar growth performances and survival rate as a commercial feed. It also improved the FA composition of fish compared to that of fish fed a plant-based feed.

Characterization and mechanism of phthalic acid esters bioaccumulation in dominant mangrove fish at different habitats in the mangrove ecosystem of Dongzhai Harbor, China

With the wide application of phthalic acid esters (PAEs) in the manufacturing of plastic products, a large number of PAEs were discharged into marine ecosystem and accumulated in fish, which has posed a serious threat to marine ecological environment and fishery resources. However, the bioaccumulation of PAEs in fish in mangrove ecosystem, the most productive marine ecosystem, has not been well characterized. In this study, dominant fish and their potential food sources (including particulate organic matter (POM), sedimentary organic matter (SOM), Metapenaeus ensis (Shrimp) and Oreochromis (Ore) were collected from Dongzhai Harbor, a typical mangrove ecosystem. The concentrations of nine PAEs in fish and their potential food sources were determined. Then stable nitrogen and carbon isotope analysis, combined with a new Bayesian mixing model (MixSIMMR) was used to quantify the diet compositions of fish and elucidate the effect of dietary habit on PAEs bioaccumulation in fish. The results indicated that the median concentration of ∑9PAEs in fish was 1119 μg/kg ww, positioning it at a moderate to low level in comparison to other regions. di-n-butyl phthalate (DBP) and diisononyl ortho-phthalate (DINP) were the dominant PAEs in fish. The PAEs concentration in demersal fish was significantly higher than that of pelagic fish, which may be attributed to the substantial contributions of shrimp (28.5 %) and POM (25.3 %) to the diet of demersal fish. This study provided new insights on the bioaccumulation of PAEs in dominant mangrove fish and confirmed that habitat preferences and food sources could significantly influence the bioaccumulation of PAEs in fish.

Effect of Body Size and Condition Factor on Proximate Composition of Clarias batrachus Under Different Concentration of Ammonia

This study is focused on examining the proximate body composition (water, fats, proteins, and ash) of Clarias batrachus, exposed to different concentrations of ammonia. Fish were kept in different groups with ammonia concentrations of 0 mg/L (T-0), 0.25mg/L (T-I), 0.5mg/L (T-II), 0.75mg/L (T-III), and 1mg/L (T-IV) for 3 months. At the end of the trial, a total of 50 samples of C. batrachus (10 from each treatment group) were taken to analyze the body composition. Mean (±SE) values of water, ash, fat, and protein contents in % wet body weight of C. batrachus were found 77.07±0.80% to 82.23±0.55%, 2.98±0.03%to 3.34±0.17%, 3.90±0.19% to 4.58±0.30% and 10.53±0.40 to 15.36±0.56 in the different studied treatment groups. Water and protein contents were significantly (P&lt;0.05) affected by the exposure of ammonia to C. batrachus. Significantly highest level of protein content was found in the fish group which was not treated with ammonia exposure (T-0). Whereas ash and fat contents showed no significant (P&gt;0.05) difference between the ammonia-treated groups and the control group. Regression analysis showed a clear effect of fish size on water and protein contents in C. batrachus reared in different treatment groups. While ash was found correlated only in T-0 (p&lt;0.001; r=0.939), and fat in T-0 (p&lt;0.001; r=0.929) and T-III (p&lt;0.05; r=0.636). However, the condition factor remained constant with the proximate composition of C. batrachus. This study would be helpful in the measurement of the body composition of fishes with the size of fishes affected by different concentrations of ammonia to analyze the nutritional value of C. batrachus.

A Study on Total Mercury Content in Surface Water and Backwater Fishes of Periyar

Aquatic systems are extensively contaminated with heavy metals released due to anthropogenic activities. Mercury is one of toxic elements and its toxicity to humans has been established. The concern about mercuric pollution in the environments started with the incident of ‘Minamata’ in Japan in 1950’s. During the study period, flowing mercury electrode was used for the preparation of caustic at Travancore Cochin Chemicals Ltd (TCC), Eloor and effluents of small industries at Edayar were the sources of mercuric pollution. Surface water samples were collected from 1Km apart from TCC, near to Indian Rare Earth Ltd (IRE), Muttinakam and Mannamthuruth and fishes (male and female) were collected from this region with the help of local fishermen. This study implies the amount of mercury in aquatic system and its influence in different body components of three fishes. Total mercury content in both the samples analysed using cold vapour atomic absorption using Mercury Analyser MA-5840 and loss on mercury on heating processes (fishes) was decreased by the use of Bethge Apparatus. Fishes were Oreochromis mossambicus (Thilapia), Mugil cephalus (Mullet) and Arius arius (Cat fish) which were living in surface to near shore, middle of the river and bottom. The proximate composition (AOAC, 2000) of fishes showed that they were low fat (0.57-4.24%) with high protein content (18.4-21.96%). The total mercury content in surface water varied from 1.667- 3.334ng/ml and it was above tolerance level (1ng/ml) while in fishes followed the order A. arius&gt; M. cephalus&gt; O. mossambicus. Relatively higher concentrations of mercury were noticed in gut and liver than muscle, and also male fishes predominated over female. This study shows that mercury cycle in the habitat water did not influence to any hazardous level in these three fishes.