Fish Weight Research Articles

Efektivitas Pencampuran Ekstrak Daun Kelor (Moringa Oleifera) yang Difermentasi Menggunakan Aspergillus Niger pada Pakan Buatan Terhadap Laju Pertumbuhan Ikan Nila (Oreochromis Niloticus)

Tilapia (Oreochromis niloticus) is a freshwater fish that is in great demand by the public because it has a thick meat texture and an affordable price. The problems faced in aquaculture activities are the high cost of feed and the length of cultivation time. Feed is a vital component in aquaculture activities, therefore feed efficiency is needed to minimize production costs. The addition of fermented moringa leaf extract in pellets is expected to accelerate the growth period. This study aims to determine the effect of the addition of fermented moringa leaf extract on tilapia growth rate. This study used a complete randomized design (CRD) method with 4 treatments, namely the addition of moringa leaf extract to pellets with concentrations of 0%, 25%, 30%, 35%. The treatment was carried out for 28 days. Parameters observed in this study were fish growth including fish length, fish weight, survival rate (SR), food conversion rate (FCR) and water quality in the form of temperature, pH and DO. The data were analyzed using anova and SPSS application. The results showed that the addition of fermented moringa leaf extract with concentrations of 0%, 25%, 30% and 35% in tilapia (Oreochromis niloticus) feed for 28 days had a significant effect on tilapia growth.

Predicting weight dispersion in seabass aquaculture using Discrete Event System simulation and Machine Learning modeling

Marine aquaculture, particularly in the Mediterranean region, faces the challenge of minimizing growth dispersion, which has a direct impact on the production cycle, market value and sustainability of the sector. Conventional grading methods are resource intensive and potentially detrimental to fish health. The current study presented an innovative approach in predicting fish weight dispersion in European seabass (Dicentrarchus labrax) aquaculture. Seabass is one of the two major fish species cultivated on the Mediterranean coast, with a fattening cycle of 18–24 months. During this period, several grading operations are carried out to minimize growth dispersion. The intricate feed-fish-water system, characterized by complex interactions among feeding regimes, fish behavior, individual metabolism and environmental factors, is the focus of the study. The comprehensive, five-step methodology addresses this complexity. The process begins with a Discrete Event System (DES) model that simulates the feed-fish-water dynamics, taking into account individual fish metabolism. This is followed by the development of a surrogate machine learning (ML) regressor model, which is trained on DES simulation data to efficiently predict growth distribution. The model is then calibrated and customized for specific fish stocks and production tanks. The preliminary results from 21 tanks in two trials with European seabass (D. labrax) showed the effectiveness of the method. The results from the simulation models achieved a R2 of 99.9 % and a Mean Absolute Percentage Error (MAPE) of 1.1 % for the prediction of mean final weight and a R2 of 90.3 % with a MAPE of 8.1 % for the standard deviation of final weight. In summary, this study represents a significant advance in the planning and management of seabass aquaculture. Given the lack of effective prediction tools in the aquaculture industry, the proposed methodology has the potential to reduce risks and inefficiencies, thus possibly optimizing aquaculture practices by increasing sustainability and profitability.

Pemanfaatan Limbah Ikan Menjadi Pakan Bernutrisi Tinggi Solusi Inovatif Dalam Sektor Perikanan Di Kabupaten Kepulauan Selayar

Fishery waste consists of liquid and solid waste, accounting for 30-40% of the total weight of fish, mollusks, and crustaceans. Unfortunately, fish waste has not been well-managed due to its low economic value. However, with the advancement of technology, the opportunity to process fish waste into high-value products is increasingly open. Modern technology enables fish waste to be converted into high-quality fish feed, reducing the cost of commercial feed. The utilization of fish waste not only generates positive economic impacts but also significant environmental benefits. Processing fish waste into feed can reduce the risk of environmental pollution, decrease greenhouse gas emissions, and reduce pressure on wild fish resources. The use of feed from fish waste helps to promote more sustainable and environmentally friendly aquaculture practices. Research results show that using fish waste as an alternative feed in shrimp farming provides dual benefits for the environment and economy. Therefore, standard quality regulations are needed to ensure effective and safe management of fish waste for the environment and human health.

Effects of buccal cavity parasite Ceratothoa carinata (Isopoda, Cymothoidae) on the condition and reproduction of its host fish Japanese scad Decapterus maruadsi.

All species of the isopod family Cymothoidae are obligate fish parasites, extracting nourishment through hematophagy and tissue consumption. To elucidate the detrimental effects of this parasitic relationship upon the host fish, we examined body length, weight of body, gonad, liver and stomach contents, and condition factor of Japanese scad Decapterus maruadsi infected with the buccal cavity parasite Ceratothoa carinata in different seasons. During the host fish's breeding season in July, the wet weight and condition factor of male and female host fish ages 1 and 2 were conspicuously diminished. No impacts were detected in September, after the breeding season. We found no impact of the parasite on the stomach content weight or signs of prey fish in the stomachs. Thus, parasite infection with C. carinata potentially diminishes the reproductive success of the host fish by negatively impacting the host's physiological condition, particularly during the breeding season.

Comparative Studies of Hematological Profiles of Cultured and Wild Clariid Catfish, Clarias gariepinus (Burchell, 1822) in South-East Nigeria

The study compared the hematological profiles of cultured and wild Clarias gariepinus from selected fish farms and rivers in Southeast Nigeria. Wild fish were collected from Anambra, Imo, Otamiri and Cross Rivers while farmed fish were sampled from Awka, Umuahia, Owerri and Abakaliki farms. 15 C. gariepinus were collected monthly from each of the rivers and farms for 12 months (January – December 2023). The overall mean weight of wild fish and farmed fish examined were 339.14 ± 2.84 and 345.87 ± 3.06g respectively. There were no significant differences (p < 0.05) in packed cell volume between the wild and cultured fish. Hemoglobin, red blood cell count, mean cell hemoglobin, mean cell hemoglobin concentration, white blood cell and monocytes counts in the wild population were significantly higher (p < 0.05) than that in the cultured type. Furthermore, mean cell volume, neutrophils, lymphocytes and platelet count in cultured individuals were significantly lower (p < 0.05) than that in wild catfish. The introduction of regular checks of the blood profiles in wild and farmed fish is highly recommended, since blood collection for analytical objectives need not kill the fish and can be applied repeatedly to the same individuals.

Study on recirculating aquaculture system (RAS) in organic fish production

Abstract The growth of conventional aquaculture has created environmental issues due to excessive feeding, low dissolved oxygen level etc into the water body. Organic aquaculture is a recent development as a solution to these issues. It is a clean alternative to reduce pollution and to produce safer consumable food. In the past few decades, recirculating aquaculture systems (RAS) were introduced to maintain pond water quality through lesser water exchange, by focusing on water reuse after treatment. In this study, the technical viability of RAS was analyzed for introduction in organic aquaculture systems. Indian major carps (IMCs) were cultured through conventional methods in the three tanks of conventional system, while the same species was grown organically in another three tanks in organic system. The stocking density and physical conditions were kept same for both cultured systems. The RAS consisted of fish culture tank with an average volume of each tank was 165 m3, a screen filter, foam fractionator and trickling filter. The various water quality parameters, i.e., solid size distribution in water, and removal efficiencies in biological treatment of both systems were compared. The present study, particle size distribution of solids in water body was measured by filtration, followed by weighing of dry residue solids. Pore sizes of 1000μ, 100μ, 20μ and 3μ were employed for filtration. For organic tanks, a majority of solids are of size between 1 mm and 100 μm. The larger sized particles (> 30 μm) constitute nearly 70 % of the solids and the trait differs from the generalized conclusions of that a major part of sediments will be of sizes less than 20 μm. For the conventional tanks, majority of solids are of size between 3 mm and 20 μm and TAN shows higher removal efficiencies for effluents from organic system rather than conventional system. The results showed that organic aquaculture causes lesser pollution load per weight of fish. The particle size distribution of organic water was better compatible to screening and sedimentation than conventional water. Also the filtration efficiencies in nitrifying trickling filters of both water bodies were comparable, with that of organic water slightly on the higher side. Thus recirculating water treatment systems are introduced in organic aquaculture.

Изучение эффективности использования кормовой добавки «Файбрамакс Плюс» в рационе стербела

A study of the feed additive “Faybramax Plus”, which is a metabiotic for the management of fish autoflora and comprehensive prevention of bacterial infections, was conducted on sterbel yearlings with an initial weight of 130 g. The experience takes place in swimming pools. The water supply in the pools was carried out from a well. The conditions of detention corresponded to the technology of fish farming. The duration of the experiment was 60 days. The number of fish in the group was 150. The control group 1 received a full-fledged combo feed; group 2 was given a full-fledged compound feed + 0.3% of the feed additive “Faybramax Plus”; Group 3 consumed full-fledged compound feed + 0.6% of the feed additive “Faybramax Plus”; group 4 was fed full-fledged compound feed + 1.0% of the feed additive “Faybramax Plus”. It was found that when using the studied feed additive, the live weight of fish in the experimental groups increased by 1.9–6.0% at the end of cultivation. The protein content in the body of sterbel was higher compared to the control by 1.8–7.5%. The cost of the resulting products (increase) compared with the control, it decreased by 4.87–13.78% per group. Profit when using the feed additive “Faybramax Plus” increased by 345.11–1,068.23 rubles per group. The level of profitability increased by 2.71–7.66% per group compared to the control. As a result of the conducted research, it was found that the use of the feed additive “Faybramax Plus” produced by the company SYMBIO is most effective in a percentage ratio of 0.6% by weight of feed, as a result of which the level of profitability increases by 7.66%.

The Effect Of Adding Natural Ingredients To Artificial Feeding On The Level Of Color Brightness Of Carp (Cyprinus carpio Linn)

The Effect of Adding Natural Ingredients to Artificial Feed on the Color Brightness Level of Goldfish (Cyprinus carpio Linn). This research aims to determine the effect of adding natural ingredients to artificial feed on the level of color brightness of goldfish (Cyprinus carpio Linn), and the growth rate and survival rate of the test fish. The method used in this research is an experimental method using a Completely Randomized Design (CRD) consisting of 4 treatments and 3 replications with a feeding frequency of three times per day with a percentage of 5% of the body weight of the test fish, a natural ingredient used in making artificial feed. These are pumpkin flour (Cucurbita moschata), mangosteen rind flour (Garcinia mangostana L), and carrot flour (Daucus carota L) with the same dose in each treatment, namely 25% of 1 kg of feed. Based on the results of variance analysis, the brightness level of goldfish color has a very real influence. The highest increase in the color of the test fish was obtained in treatment A, pumpkin flour, amounting to (1.37) on the Toca color finder scale (from pale orange to dark orange), followed by the second highest in treatment C, carrot flour, amounting to (1.2), treatment B flour. Mangosteen peel was in third position with an increase in color of (0.94) and the lowest increase in color change occurred in treatment D (control = without the addition of natural ingredients) of 0.7. However, absolute weight and length growth did not have a real influence. The overall graduation rate is 87.49%. The average water quality parameters are temperature 26-29oC, pH 7.5-7.9 and ammonia 0.25 ppm.

Stereo matching and 3D reconstruction with NeRF supervision for accurate weight estimation in free-swimming fish

Non-invasive methods of accurate estimation of fish weight are essential for biomass assessment, precision feeding, and effective management in aquaculture. However, the lack of large-scale stereo matching datasets and costly depth sensing equipment in underwater scenarios present significant challenges to accurately measure the size of free-swimming fish. This study introduces a novel NeRF-supervised stereo matching network for precise depth estimation and 3D reconstruction of the fish body. The state-of-the-art neural rendering methods are employed to generate stereo training data from image sequences. In this study, the residual network with deformable convolutions was proposed to extract contextual texture features, significantly enhancing disparity estimation accuracy at the edge of the fish body. Additionally, multiscale spatial features are fused using a feature pyramid network (FPN). To enhance the adaptability of disparity search, we introduce a lightweight Triplet Attention module to capture cross-dimensional dependencies prior to constructing the correlation volume. Experimental results demonstrate the effectiveness of the proposed depth estimation method, achieving an impressive result of 92.35% in the similarity metric, compared to the ground truth. Moreover, we developed a weight estimation model based on bass perimeter using instance segmentation and 3D reconstruction techniques. Notably, a robust correlation (correlation coefficient of 0.98) between fish perimeter and weight is observed, highlighting the potential application of our methods to enhance the accuracy of weight estimation for free-swimming fish.

MERANCANG JARING INSANG PERMUKAAN UNTUK MENANGKAP IKAN DI TELUK AMBON DALAM

The use of gill nets in fishing is a well-established practice among fishermen due to several factors including ease of material acquisition, simple operational techniques, relatively affordable costs, and high selectivity in catching fish of specific sizes. This study aims to describe the design of fishing gill nets in Inner Ambon Bay. The research was conducted at the Ambon Fisheries Training and Extension Center (BP) in April and May of 2024. The design and construction of surface gillnets for mackerel scad consist of mesh size (inches), fish body circumference, net length, hanging ratio, weights, and distance between floats and weights. The design of the surface gill net with a 2-inch mesh size and a 45% hanging ratio has proven to be effective in catching mackerel scad (Decapterus sp) ranging from 17 cm to 26 cm in length. The use of polyamide (PA) material for the net body provides the necessary strength and flexibility, while the float made of polyvinyl chloride (PVC) and lead weights ensures balanced distribution for optimal functioning in the water. A 45% hanging ratio provides an ideal balance between net length and fish trapping ability, avoiding nets that are too curved or stiff, which can reduce fishing effectiveness.

Impact of Nutritional Tea Polyphenols on Growth, Feed Efficiency, Biochemical Traits, Antioxidant Capacity, Haematological Parameters and Immunity in Coho Salmon (Oncorhynchus kisutch).

To evaluate the impact of nutritional tea polyphenols (TPs) on body composition, growth, biochemical markers, antioxidant capacity, and hemato-immunological levels, a ten-week feeding experiment was carried out on coho salmon (Oncorhynchus kisutch, 180.51 ± 0.15 g). The control group was fed a basal diet; the T1, T2, T3, and T4 groups were fed 0.005%, 0.01%, 0.02%, and 0.04% TPs, respectively. These results demonstrate that adding TPs significantly (p < 0.05) increased the coho salmon fish's weight gain (WG), relative growth rate (RGR), condition factor (CF), feed efficacy (FE), daily growth rate (DGR), and specific growth rate (SGR). There was no discernible difference in the body compositions of the treated TPs and the control group (p > 0.05). In addition, the T3 group showed a significant (p < 0.05) decrease in GPT, LDL, HDL, TC, and CAT. Fish given a 0.02% diet containing TPs had significantly lower levels of malondialdehyde (MDA) in their liver; yet, the TP-treated groups had higher levels of SOD and CAT than the control (p < 0.05). The data analysis shows a significant rise in lysozyme, respiratory burst activity, bactericidal activity, and blood hematological parameters in the 0.01-0.04% TP groups. According to these findings, TPs could be a useful dietary supplement for raising the antioxidant status, growth parameters, haemato-immunological response, and whole-body composition of coho salmon fish.

Artificial Neural Networks (ANN) to Model Microplastic Contents in Commercial Fish Species at Jakarta Bay

Jakarta Bay is known as one of the marine ecosystems that have been contaminated by microplastics. Despite massive loads of microplasticcontamination, Jakarta Bay is also habitat to potential commercial fish species, including anchovy Stolephorus commersonnii and mackerel Rastrelliger kanagurta. While information on the microplastic contents and their determining factors is still limited, the goal of this study was touse artificial neural networks (ANN) as a novel and useful tool to model the determinants of microplastic content in fish in Jakarta Bay, using fish weight and length as proxies. Inside the stomachs of S. commersonnii and R. kanagurta, the order of microplastics from the highest to thelowest was fiber &gt; film &gt; fragment &gt; pellet. Based on the RMSE values of 3.199 for S. commersonnii and 2.738 for R. kanagurta, the ANNmodel of fish’s weight + length ~ pellet was found to be the best fitted model to explain the correlation of fish weight and length with microplastic content in the stomach. The results indicate that ANN is suitable for solving large, complex problems in determining and projecting microplastic contents and provides better estimates that can be used to manage R. kanagurta and S. commersonnii along with microplastic contamination threats.

Community Structure Characteristics and Changes in Fish Species at Poyang Lake after the Yangtze River Fishing Ban

To understand the fish community structure characteristics and changes in Poyang Lake after the Yangtze River fishing ban in 2021, seven sampling stations were established, namely in Hukou, Lushan, Duchang, Yongxiu, Nanjishan, Ruihong, and Poyang, for fishery resource surveys between 2020 and 2021. The results showed that 93 fish species were identified, belonging to 11 orders, 20 families, and 61 genera, which was an increase of 4.5% from before the fishing ban. Of these, 52 Cyprinidae species were identified, comprising the highest proportion (55.91%). Four invasive alien species (hybrid sturgeon, Cirrhina mrigala, Piaractus brachypomus, and Mugil cephalus) were identified, and the number of alien species in Poyang Lake was higher than before the fishing ban. Carnivorous and mid-lower-level fish showed a significant increase, accounting for 47.31% and 38.71% of the total species, respectively. Compared with the Yangtze River before the fishing ban, the body length and body weight of the main economic fish in Poyang Lake increased by 6.10–61.26% and by 15.14–291.57%, respectively. In terms of age structure, the proportion of major economically important fish aged 1 or 2 years decreased significantly, while the proportion of older fish increased substantially. There was little difference in the diversity of fish communities at different stations in Poyang Lake. In terms of biodiversity, the Shannon–Wiener index ranged from 2.158 to 2.909, with Poyang having the highest value and Nanjishan the lowest. Margalef’s index ranged from 4.265 to 6.459, with Lushan having the highest value and Nanjishan the lowest. Pielou’s index ranged from 0.617 to 0.822, with Duchang having the highest value and Nanjishan the lowest. Hence, the Yangtze river fishing ban has played an important and positive role in the restoration of fishery resources in Poyang Lake. However, long-term tracking and monitoring are needed to provide information to comprehensively evaluate the ecological impact of the Poyang Lake fishing ban.

Influence of Different Salt Concentrations and Addition of Commercial Enzyme on the Chemical Characteristics of Fish Sauce from Round Scad (Decapterus maruadsi)

The effects of salt concentrations and addition of Flavourzyme on the chemical characteristics of fish sauce were studied. The fermentation mixtures were prepared by mixing fish with salt at one of two levels (25% or 30%) and Flavourzyme supplementation at 0%, 0.1%, 0.3%, and 0.5% based on fish weight, and fermented at the ambient temperature ranging from 25 to 32 °C for three months. The results showed that the fish sauces with 25% salt contained total nitrogen of 17.4 - 25.3 g/L, amino acid nitrogen of 8.1 - 13.5 g/L, and ammonia nitrogen of 1.2 - 1.9 g/L. For fish sauces with 30% salt, these contents were 16.3 - 24.2 g/L, 7.2 - 12.2 g/L and 1.1 - 1.5 g/L, respectively. The fish sauces with 25% salt had amino acid nitrogen contents of 8.1 g/L for sample without Flavourzyme and 10.9 - 13.5 g/L for samples with Flavourzyme. The higher enzyme levels gave higher yield, total nitrogen, and amino acid nitrogen contents but lower ammonia nitrogen and pH values. This study suggested that the fish sauce produced using 25% salt and 0.3% Flavourzyme was appropriate. Flavourzyme could be a potential enzyme applied to improve the chemical properties of fish sauce.

Bioaccumulation of Cadmium in Muscle and Liver Tissues of Juvenile Yellowfin Tuna (Thunnus albacares) from the Indian Ocean.

The present study evaluated the cadmium (Cd) levels and temporal variation of Cd in dark muscle, white muscle, and liver of juvenile Thunnus albacares. 72 individuals (Standard length: 50-67 cm; weight: 0.8-2.5 kg) were collected from Indian Oceanic water around Sri Lanka during the period between April 2021 to May 2022. Total Cd levels were analyzed using an Inductively Coupled Plasma Mass Spectrophotometer. The mean Cd levels (mean ± SD mg kg-1 dry weight) in different tissues varied with significantly higher levels in the liver (13.62 ± 0.98, p < 0.05), compared to dark muscle (0.52 ± 0.05), and white muscle (0.42 ± 0.04). Cd levels in liver tissues were positively correlated (p < 0.05) with the fish weight. The Cd levels reported in dark muscles, white muscles, and liver tissues were significantly higher (p < 0.05) during 2nd inter-monsoon than in the other monsoonal regimes and exceeded the maximum permissible level (0.1 mg kg-1 wet weight) set by the European Union (EU). However, the measured Cd levels in white and dark muscles were below the maximum permissible level (0.2 mg kg-1 wet weight) set by FAO/WHO. The Cd levels in all the liver tissues were above the levels set by the EU and FAO/WHO. Accordingly, people should avoid the consumption of liver tissues of T. albacares from the Indian Ocean. A human with a body weight of 60 kg can consume white muscles up to 4.667 kg per week without exceeding the Provisional Tolerable Weekly Intake.

Evaluation of Acute Toxicity and Lethal Concentration (LC50) of Cypermethrin (25% EC) in Adults of Cyprinus carpio (Linnaeus 1758)

The present study attempted to determine the acute toxicity and medial lethal concentrations of Cypermethrin (25% EC) for common carp Cyprinus carpio using Finney’s static bioassay (1971), probit analysis method. The LC50 values for 24, 48, 72 and 96 hr were found to be 3.962 µl Lit-1, 3.767 µl Lit-1, 3.349 µl Lit-1 and 2.924 µl Lit-1 respectively. Fish (weight 90–100 g, length up to 18±2 cm) were exposed to different concentrations of cypermethrin which were 1.5 µl Lit-1, 2.0 µl Lit-1, 2.5 µl Lit-1, 3.0 µl Lit-1, 3.5 µl Lit-1, 4.0 µl Lit-1 and 4.5 µl Lit-1 up to 96 hr. LC50 value decreases with an increase in exposure time. During this exposure period, abnormal behaviors like restlessness, hyperactivity, erratic movements, increased opercular movements, and loss of equilibrium and response were noticed in carp. Over secretion of mucous all over the body surface along with respiratory stress and mortality was also observed.

The protective effect of dietary extract of Astragalus membranaceus on the high stocking density, copper and trichlorfon in Jian carp (Cyprinus carpio var. Jian)

This study was designed to examine the protective effects of extract of Astragalus membranaceus (EAM) against stress, which induced by high stocking density, Cu and trichlorfon exposure in Jian carp (Cyprinus carpio var. Jian). The husbandry period (23.0 ± 1 °C) for high stocking density (0.97 fish/L) was 60 days with the initial fish weight 7.2 ± 0.2 g, and Cu (0.7 mg/L) and trichlorfon (2.2 mg/L) exposure was 4 days after feeding trial (30 days) with the initial fish weight 10.5 ± 0.3 g. Stress of high stocking density and Cu exposure decrease 48.2 % of fish weight gain and reduced 97.6 % of feed intake. Meanwhile, trichlorfon exposure induced 100 % fish rollover. High stocking densities and Cu exposure decreased activities of amylase, trypsin, as well as Na+/K+-ATPase and alkaline phosphatase and increased malonaldehyde content in fish digestive organs (P < 0.05), indicating an interruption of digestive ability and antioxidant status. Furthermore, trichlorfon exposure decreased activities of lactate dehydrogenase, superoxide dismutase, catalase, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase in fish muscles (P < 0.05), indicating an interruption on bioenergetic homeostasis and antioxidant status. Dietary EAM supplementation relieved these detrimental effect, which induced by high stocking density, Cu and trichlorfon exposure. The optimum dietary EAM supplementation were 5.23, 4.79 and 5.12 g kg/diet for Jian carp under high stocking densities, Cu and trichlorfon exposure, respectively. Our study indicates that dietary EAM supplementation offers a feasible way for relieving the stress which induced by inappropriate high stocking densities, Cu, as well as trichlorfon.

Co-incorporation of Black Soldier Fly (Hermetia illucens) Larvae and Moringa (Moringa oleifera) Leaves in the Diet Increase African Catfish Profitability (Clarias gariepinus)

Aquaculture is a fast-growing activity in Cameroon and required substantial quantities of affordable protein-rich feed. In this study, we co-incorporated Moringa leaves (MOL) and black soldier fly larvae meal (BSFLM) in catfish diet, and the effect was evaluated on feed floatation, fish growth, flesh organoleptic qualities and profitability. 450 juvenile`s catfish weighing averagely 10 g, were subjected to five dietary treatments consisting of: T0 (0% BSFLM and 0% MOL); T1 (6.25% BSFLM and 5% MOL); T2 (12.5% BSFLM and 10% MOL); T3 (18.75% BSFLM and 15% MOL) and T4 (25% BSFLM and 20% MOL) for 119 days. The treatment T3 containing 18.75% BSFLM and 15% MOL recorded the highest floatation duration, fish weight (113.83±17.31 g) and weight gain (103.25±17.8 g), and the lowest feed conversion ratio (1.60±0.37). The flesh tasted good and was acceptable in all treatments. Incorporating BSFLM and MOL in the diets reduced the cost per kg of feed from 18 to 23%, thus increasing the system's profitability from 45.91 to 60.84%. We concluded that BSFLM and MOL can partially substitute fish meal in catfish diet and improve the profitability and offers insights into the development more profitable and sustainable aquaculture in Cameroon and globally.

Diet and trophic structure of fishes in the Barents Sea: Effects of size within (ontogenetic) and between species

A large data set on stomach content (over 27,000 individual fish) – collected in the Barents Sea in 2015 – was used to examine ontogenetic and interspecific changes in diet with size for 35 fish species. The analysis combined the use of hierarchical clustering and random forest. Two different diet metrics were used (% weight of prey types per weight of stomach content or per weight of fish, the latter reflecting also feeding intensity), and data were analysed based on average diet of predator groups (species and size groups) across the entire sample series (from the whole Barents Sea in different seasons), or for data broken down by geographical areas and seasons. Similar trophic groups (clusters) were identified for the various data sets suggesting that the results on trophic structure were robust. The trophic groups including size information were broadly similar to groups found earlier with data averaged at species level. Hierarchical clustering produces a hierarchy of trophic groups (or trophic guilds) at various levels of diet dissimilarity. With 12 clusters identified, one cluster had fish as dominant prey, and 5–6 others had either plankton or benthos as dominant prey. The clusters tended to be distinct and homogenous with one dominant prey category in average diet (often > 60 %). This was especially the case for the plankton clusters, with copepods, euphausiids, hyperiid amphipods, or gelatinous zooplankton as dominant prey in each of 4 trophic groups. The benthos clusters tended to be less dissimilar with more overlap in diet composition, with predominance of either hard-shelled forms (echinoderms and molluscs) or softer prey (polychaetes and crustaceans) for groups of clusters. There were clear patterns of ontogenetic shifts in fish diet. Fish that clustered as piscivores at larger size tended to grow from being planktivores when smaller. Smaller species of planktivores or benthivores shifted position among trophic groups but remained within the categories of planktivores or benthivores, respectively. Taxonomy (species) tended to be more important than size for explaining the diet composition of the different clusters of fish predators.

Study on hormone induction of the male parent and embryonic development, gonad differentiation, and growth of “All-female No.1” Culteralburnus

Female Culter alburnus was faster in growth rate than males. In this study, the gynogenetic G2 and the pseudo-male G2' were used as the female and male parents, respectively, to breed a new national variety “All-female No.1” C. alburnus (AFC). Hormone induction, embryonic development, gonadal differentiation, and growth of AFC were studied. The results showed induction with low concentrations of 17α-methyltestosterone in a indoor-net cage culture was not effective. Under the stimulation of 17α-methyltestosterone, some gonads had a tendency to transform into testis, but not completely. There were three types of gonads in 5-month-old and four types of gonads in 12-month-old fishes, however, they all differentiated into ovaries in 15-month-old fishes. Testosterone propionate and high concentrations of 17α-methyltestosterone in pond culture induction had a good effect resulting in ①a functional pseudo-male with normal testis development that could successfully extrude semen during the breeding period, ②a pseudo-male with normal testis development, but could not extrude semen, and ③the appearance of intersexual glands. The second experiment revealed that with common fish, all-female fish embryo had normal embryonic development. The development time and morphological characteristics of each stage were similar, but the development of the all-female embryo was slightly slower than the common embryos. The gonad differentiation of the all-female embryo were normal and none differentiated into testis, which indicated that all-female could ensure the female sex without affecting the normal gonad differentiation. The correlation between body weight, length, and month-age of all-female and common fish was strong. The all-female had faster growth rate and more uniform growth specification than the common fish. Therefore, the use of testosterone propionate and high concentrations of 17α-methyltestosterone in pond culture induction could avoid complete degeneration of gonads into ovaries. The all-female embryo had the advantages of normal embryonic development and gonadal differentiation, faster growth, and uniform growth specification.