Growth Rate Of Fish Research Articles

Haematological, biochemical, enzymological changes and mitochondrial dysfunction of liver in freshwater climbing perch Anabas testudineus during their acute and chronic exposure to sodium fluoride

Anthropogenic activities are increasing fluoride concentration in watercourses. The present study focuses on the sublethal toxicity of sodium fluoride during sub-chronic and chronic time periods in the freshwater fish Anabas testudineus. The 96-hour LC50 value for fluoride was found to be 616.50 mg/L. Excessive mucous production and hyper excitability, followed by loss of balance, were seen in fish under acute fluoride exposure. Significant reduction in yield and specific growth rate of fish were assessed at 15, 30 and 45-days exposure intervals. Different bio-indicators like Hepatosomatic-index, Gonadosomatic-index and fecundity were reduced significantly in fish exposed to 10% (61.6 mg/L) and 20% (123.2 mg/L) of 96 h of LC50 values of fluoride in comparison to control. Toxicant concentrations directly correlated with parameter lowering. Fluoride exposure increased plasma glucose, creatinine, AST, and ALT and reduced total RBC, haemoglobin content, Hct (%), plasma protein, and cholesterol. Moreover, fluoride exposure significantly reduces the mitochondrial membrane potential in liver. This may result in metabolic depression, haematological, biochemical, and enzymological stress. The in-silico structural analysis predicts that fluoride may impede cytochrome c oxidase of the electron transport system, hence inhibiting mitochondrial functionality. These findings collectively highlight the urgent need for stringent regulation and monitoring of fluoride levels in freshwater ecosystems, as the subchronic and chronic effects observed in A. testudineus may have broader implications for aquatic ecosystems.

Effect of fatty acid-enriched black soldier fly larvae meal combined with chitinase on the metabolic processes of Nile tilapia.

The aim of this study is to determine to what extent the addition of chitinase to black soldier fly (BSF) larval meal enriched or not with long-chain PUFA (LC-PUFA) could improve growth, protein digestion processes and gut microbial composition in Nile tilapia. Two different types of BSF meal were produced, in which larvae were reared on substrates formulated with vegetable culture substrate (VGS) or marine fish offal substrate (FOS). The BSF raised on VGS was enriched in α-linolenic acid (ALA), while that raised on FOS was enriched in ALA + EPA + DHA. Six BSF-based diets, enriched or not with chitinase, were formulated and compared with a control diet based on fishmeal and fish oil (FMFO). Two doses (D) of chitinase from Aspergillus niger (2 g and 5 g/kg feed) were added to the BSF larval diets (VGD0 and FOD0) to obtain four additional diets: VGD2, VGD5, FOD2 and FOD5. After 53 d of feeding, results showed that the BSF/FOS-based diets induced feed utilisation, protein efficiency and digestibility, as well as growth comparable to the FMFO control diet, but better than the BSF/VGS-based diets. The supplementation of chitinase to BSF/FOS increased in fish intestine the relative abundance of beneficial microbiota such as those of the Bacillaceae family. The results showed that LC-PUFA-enriched BSF meal associated with chitinase could be used as an effective alternative to fishmeal in order to improve protein digestion processes, beneficial microbiota and ultimately fish growth rate.

Effect of biofloc technology at varies biological factors on the growth performance and water quality in cultivation of red hybrid tilapia

Aquaculture is one of the important food-producing sectors. However, the effluent of the aquaculture system consists of pollutants such as nitrogenous compounds and the ample usage of water for traditional aquaculture systems. Therefore, biofloc technology was developed in the aquaculture industry in the 1980s to improve the water quality of the system and increase the fish production. The purpose of this experimental work is to investigate the effect of biological factors on the growth performance of fish and the water quality of the biofloc technology (BFT) aquaculture system for red hybrid tilapia cultivation. In this study, 3 biological factors such as the carbon-to-nitrogen ratio, stocking density and the feeding rate were studied under BFT. Parallel experiments in thirteen suspended growth tanks were carried out within (10:1-20:1) C/N ratio, (1%-5%) feeding rate and (20-80 fish m-3) stocking density for 10 weeks. Growth rate of fish and water quality data such as ammonia, nitrite and nitrate concentrations were collected weekly during the study. The results revealed that the 20:1 C/N ratio gave the best water quality. Feeding rate at 4% of body weight produced good growth performance of the tilapia species and the higher stocking densities lead to lower water quality and survival rate.

Peciliarities of Hormonal Regulation of Growth Rate and Generative Functions of Fishes under Increased Anthropogenic Influence

The hydrochemical parameters, the production and destruction of organic substances in different areas on the Ros and Protoka rivers were studied. Nearby the Horodyshche vil. (Ros River) and Pishchana vil. (Protoka River), concentration of ammonium nitrogen exceeded control values 2-5 times, nitrites - 1.5-2.5 times, nitrates - almost 3.0-5.8 times (as control the Ros River in the Olexandria dendrological park was used). Water of the considered sections was significantly contaminated by pesticides (chlorpyriphos) from the adjacent territories. Elevated content of nutrients in water conditioned intensive production processes (Pishchana vil.), whereas high chlorpyriphos content (Gorodyshche vil.) along with significant concentration of chlorpyriphos (Gorodyshche vil.) suppressed organic matters' production. The water quality deterioration and presence of the toxic contamination caused decrease of the size-mass parameters of common ruff, river perch and common rudd, mainly owing to decrease of somatotropin content in blood. The gonadosomatic index of perch and rudd females from contaminated water bodies increased, whereas in males it decreased as compared with the control. The relative and absolute fertility of rudd increased along with increase of the contamination degree. The females' fertility growth under the unfavorable conditions was associated with increase of the estradiol content in blood. The perch and rudd males were characterized by decrease of the gonadosomatic index along with decrease of the testosterone content in blood. Decrease of size and mass parameters and increase of the females' fertility is an adaptive response aimed at the population maintaining and higher vitality under toxic environment. These processes are provided by hormonal regulation of metabolic processes.

Effects of antibiotics and microplastics on the growth of Sebastes schlegelii

The pollution of antibiotics and microplastics in mariculture environments has elicited widespread concern due to their potential threats to health of aquatic organisms and stability and function of marine ecosystems. However, the toxicological outcomes of the combined exposure of antibiotics and microplastics on fish are still unclear. In this work, two kinds of veterinary antibiotics commonly used in marine culture environment were selected to explore the effects of their combined exposure with polyamide microplastics on the growth performance and nutritional quality of Sebastes schlegelii. The results showed that, compared with the unexposed group, the individual exposure of antibiotic and microplastic significantly reduced the weight gain rate (194.3–200.4%) and specific growth rate (211.4–218.1%) of the juvenile fish. Compared with the unexposed group, the weight gain rate and specific growth rate of juveniles were significantly reduced by 272.8–347.5% in the combined exposure, indicated that the combined exposure had a synergistic effect on the growth inhibition of juvenile fish. This study provided basic theoretical data for the risk assessment of antibiotics and microplastics in the marine culture environment.

Combining genome-wide association study and transcriptome analysis to identify molecular markers and genetic basis of population-asynchronous ovarian development in Coilia nasus.

Coilia nasus, a migratory fish species found in the middle and lower reaches of the Yangtze River and along offshore areas of China, possesses considerable aquacultural and economic potential. However, the species faces challenges due to significant variation in the gonadal development rate among females, resulting in inconsistent ovarian maturation times at the population level, an extended reproductive period, and limitations on fish growth rate due to ovarian prematurity. In the present study, we combined genome-wide association study (GWAS) and comparative transcriptome analysis to investigate the potential single nucleotide polymorphisms (SNPs) and candidate genes associated with population-asynchronous ovarian development in C. nasus. Genotyping of the female population based on whole-genome resequencing yielded 2 120 695 high-quality SNPs, 39 of which were suggestively associated with ovarian development. Of note, a significant SNP peak on LG21 containing 30 suggestively associated SNPs was identified, with cpne5a determined as the causal gene of the peak. Therefore, single-marker and haplotype association analyses were performed on cpne5a, revealing four genetic markers ( P<0.05) and seven haplotypes (r 2>0.9) significantly associated with the phenotype. Comparative transcriptome analysis of precociously and normally maturing individuals screened out 29 and 426 overlapping differentially expressed genes in the brain and ovary, respectively, between individuals of different body sizes. Integrating the GWAS and transcriptome analysis results, this study identified genes and pathways related to hypothalamic-pituitary-gonadal axis hormone secretion, extracellular matrix, angiogenesis, and gap junctions involved in population-asynchronous ovarian development. The insights gained from this study provide a basis for a deeper understanding of the molecular mechanisms underlying ovarian development in fish and may facilitate the genetic breeding of C. nasus strains exhibiting population-synchronous ovarian development in the future.

Histological examination of the young Oncorhynchus mykiss intestines using the feed with chelated and probiotic supplements.

Macronutrient and micronutrient deficiencies in the fish diet can affect fish growth rate, ability to resist disease, and fillet quality. Determination of effective dose of developed feed additives consisting of chelate compounds of biogenic elements and probiotic preparation based on Bacillus subtilis. Young rainbow trout were divided into four groups consisting of 100 fish each. The control group received standard food; the experimental groups received food with chelates and probiotics in different concentrations. At the end of the experiment (30 days), the middle intestine histology and morphometric parameters were studied. The use of chelated compounds alone affected the state of the intestinal villi and the infiltration of the epithelium by lymphocytes. The addition of a probiotic had a positive effect on the migration of immune cells in the intestinal villi; however, the probiotic in high concentrations contributed to a decrease in the number and area of goblet cells. Synergistic effects of chelated compounds and probiotic preparations on the morphometric parameters of the medium intestine were observed. In the proper doses, the studied feed additives might be recommended for rainbow trout farming under industrial aquaculture conditions.

Effect of Maggot‒Tofu Dreg Mixed Flours with Addition of Lysine on Formulation of Fish Feed to Accelerate the Growth of Tilapia (Oreochromis niloticus)

Maggot flour, which contains high protein has potential in the development of fish feed. The focus of this study was to investigate the formulation of fish feed based on mixed flours (maggot and tofu dregs flours) with the addition of lysine to improve feed quality and feeding efficiency. The Pearson Square Method (PSM) was used in the formulation process of fish feed with a total protein target of 35%. The formulated fish feed was applied on tilapia fish (Oreochromis niloticus). The fish weight and ammonia levels in the water were also measured to determine the effect of fish feed on water quality. The highest protein content (33%) was obtained from ratio of mixed flours of 3:1 (%(w/w)). The highest floatability value of fish feed was 194±2 sec. The optimum results for fish growth were obtained from mixed ratio of maggot flour and tofu dregs of 3:1 % (w/w). with the addition of 2 % (w/w) of lysine. The optimal growth rate of fish was 0.041 g·day-1 after 30 days of the experiment. While the level of ammonia in the water was not affected by the fish feed formulation or the addition of lysine in the fish feed. Thus, the amino acid lysine greatly influences the feed conversion ratio and specific growth rate so that it has the potential to accelerate the growth of tilapia.

Effects of Dietary Bile Acids on Growth Performance, Lipid Deposition, and Intestinal Health of Rice Field Eel (Monopterus albus) Fed with High-Lipid Diets.

The purpose of this trial was to study the positive effects of bile acids (BAs) on growth performance and intestinal health of rice field eel fed with high-lipid diets (HLDs). Rice field eels (initial weight 17.00 ± 0.10 g) were divided into four groups, each group containing four repetitions and feeding with different isonitrogenous diet: control diet containing 7% lipid content, HLDs containing the lipid content increased to 13%, HLDs supplementing with 0.025% BAs and 0.05% BAs, respectively. After 8 weeks, compared control group, the fish fed HLDs had no significant effect on weight gain rate and specific growth rate (P > 0.05), but increased the lipid deposition in tissues and intestinal lipase activity, and damaged to intestinal oxidative stress, inflammatory response, physical barrier, and structural integrity (P < 0.05). Dietary BAs significantly increased weight gain rate and specific growth rate in fish fed with HL diets (P < 0.05) and reduced feed conversation rate (P < 0.05). Further, the eels fed with BAs reduced the total lipid content in liver, muscle, and whole body (P < 0.05). Dietary BAs decreased the activity of intestinal lipase (P < 0.05). Meanwhile, BAs supplemented in HLDs improved intestinal antioxidant capacity through increasing the activities of T-SOD (total superoxide dismutase), GSH-PX (glutathione peroxidase), CAT (catalase), T-AOC (total antioxidant capacity), whereas reducing MDA (malondialdehyde) content (P < 0.05). Moreover, dietary BAs regulated the mRNA expression related to inflammatory response, oxidative stress, and physical barrier in intestine, such as tnf-α, il-8, tlr-8, il-10, nrf2, keap1, claudin12, and claudin15 (P < 0.05). Dietary BAs supplementation also enhanced the intestinal structural integrity characterized by increased fold height and lamina propria width (P < 0.05). This study showed that dietary BAs supplemented in HLDs (13% lipid) could increase the growth performance of rice field eel, reduce lipid deposition in tissues and whole body, and enhance intestinal health.

Impact of Various Natural Feed Types on Water Quality on Silver Arowana (Osteo-glossum Bicirrhosum)

The research was conducted to determine the relationship between water quality and body length of arowana fish by measuring several water parameters including temperature, pH, dissolved oxygen and ammonia. In relation to length growth, calculations on SR, SGR are also carried out using ANNOVA. Direct laboratory scale observations were carried out by providing different feeds, including bloodworms, maggot, crickets and live fish with the water source for cultivation activities being well water. The results of observations in the field show that the growth rate of fish in length is influenced by the type of feed given. Giving bloodworms has the most effective value, next to live fish, maggots and crickets. This type of feed also affects the quality of the water used. To maintain success in ornamental fish cultivation, it is recommended to use water efficiently through integrated fish cultivation. Checking the water regularly as well as training of farmers on good management practices and integration is needed to ensure good water quality.

Growth performance, gut microbiota composition, health and welfare of European sea bass (Dicentrarchus labrax) fed an environmentally and economically sustainable low marine protein diet in sea cages

The large use of fish meal/fish oil in carnivorous fish feeds is the main concern regarding environmental sustainability of aquaculture. Here, we evaluated the effects of an innovative diet, designed to be (1) environmentally sustainable by lowering the marine protein content while being (2) cost effective by using sustainable alternative raw materials with acceptable cost and produced on an industrial scale, on growth performance, gut microbiota composition, health and welfare of European sea bass (Dicentrarchus labrax), a key species of the Mediterranean marine aquaculture, reared in sea cages. Results show that the specific growth rate of fish fed the low marine protein diet was significantly lower than those fed conventional diet (0.67% vs 0.69%). Fatty acid profile of fillets from fish fed a low marine protein diet presented significant lower n-6 and higher n-3 content when compared to conventional ones. Then, a significant increase in the abundance of Vibrio and reduction of Photobacterium were found in the gut of fish fed with the low marine protein diet but effects on sea bass health needs further investigation. Finally, no major health and welfare alterations for fish fed the low marine protein diet were observed, combined with a potential slight benefit related to humoral immunity. Overall, these results suggest that despite the low marine protein diet moderately affects growth performance, it nevertheless may enhance environmental and economic sustainability of the sea bass aquaculture.

The Effect of Different Ratios of Internal Organs, Dried Artemia and Frozen Artemia on the Growth Rates of Common Carp Fish

A total of 140 fish with an average weight of 35±2 grams were used and reared for a period of 70 days. The fish were randomly distributed into seven treatments, which included the addition of dried Artemia to the second, third, and fourth treatments at a ratio of 50% of fishmeal. The internal organs powder of the fish was added to the third and fourth treatments at a ratio of 25% and 50% of fishmeal respectively. Frozen Artemia was added to the fifth, sixth, and seventh treatments at a ratio of 50% of fishmeal, and the internal organs powder of the fish was added to the sixth and seventh treatments at a ratio of 25% and 50% of fishmeal respectively. The results showed that the arithmetic mean of the sixth treatment was superior to all other treatments, reaching 82.80 grams/fish. This treatment included the addition of 50% frozen Artemia, 25% fish powder, and 25% internal organs powder. Furthermore, the results showed that the lowest weight gain rate for the fish was in the fourth treatment (51.40 grams/fish), which included the addition of 50% dried Artemia and 50% internal organs powder to the common carp fish feed. In conclusion, the addition of frozen Artemia at a ratio of 50% of fishmeal, enhanced with 25% internal organs powder, was found to be the best among the treatments in terms of growth criteria.

Effect of Different Natural Feeding (Blood Worm, Silk Worm, and Water Fleas) on The Growth of Betta Fish (Betta sp.)

One type of freshwater ornamental fish that is in great demand by the public is Betta fish (Betta sp.). The problem faced by Betta fish cultivation activity is inappropriate feed, for example feed with low protein content. Low protein causes slow growth in fish. This study aims to determine the effect of different natural feeds (silk worms, blood worms, water fleas, and controls) on the growth of Betta fish. The results showed that there was a significant effect (p<0.05) on the growth and specific growth rate of betta fish. However, there was no significant effect (p>0.05) of different natural feeding on the survival rate parameter. The highest result showed in treatment B (silk worm) with a weight value of 1.09 g, a length of 4.48 cm, and specific growth rate value of 1.77 ± 1.768. It can be concluded that silk worm is the best natural feeding for betta fish.

Effects of Dietary Fishmeal Replacement with Soybean Meal on Growth Performance, Digestion, Hepatic Metabolism, Antioxidant Capacity, and Innate Immunity of Juvenile Large Yellow Croaker (Larimichthys crocea)

A 70-day feeding trial was conducted to determine the effects of the replacement of fishmeal (FM) by soybean meal (SM) in diets on growth performance, digestion, hepatic metabolism, antioxidant capacity, and innate immunity of juvenile large yellow croaker (Larimichthys crocea). Four iso-lipidic and iso-nitrogenous diets replacing 0, 15, 30, and 45 FM protein by SM protein were formulated, named FM, SM15, SM30, and SM45, respectively. Results indicated that the specific growth rate (FM = 1.55, SM15 = 1.50, SM30 = 1.48, and SM45 = 1.34%) of fish showed a significant linear trend ( P &lt; 0.05 ). With increasing dietary SM, the activity of trypsin (262.02, 179.34, 144.41, and 123.92 U/mg·prot) significantly decreased (linear trend, P &lt; 0.05 ). The content of high-density lipoprotein cholesterol showed a significant linear trend and quadratic trend, and the maximum was observed in fish fed the diet with 45% protein from SM ( P &lt; 0.05 ). The mRNA expression of the mechanistic target of rapamycin (m-tor) and ribosomal protein S6 (rps6) showed a significant linear trend ( P &lt; 0.05 ). The content of malondialdehyde (81.82, 92.91, 79.64, and 126.45 nmol/mg·prot) showed a significant linear trend and quadratic trend; the minimum was observed in fish fed the diet with 30% protein from SM ( P &lt; 0.05 ). The activity of acid phosphatase (328.45, 300.08, 254.03, and 223.51 U/mg·prot) significantly decreased with increasing dietary SM substitution levels (linear trend, P &lt; 0.05 ). A significant quadratic trend was observed in the mRNA expression of interferon-γ and interleukin-1β, while the maximum was observed in fish fed the diet with 45% protein from SM ( P &lt; 0.05 ). In conclusion, this study demonstrated that the replacement of FM by SM in diets can decrease the growth performance, digestion, antioxidant capacity, and innate immunity and affect the hepatic metabolism of juvenile large yellow croaker. The minimum negative effect was obtained when 30% of FM was replaced by SM.

Effect of substituting fish meal with various by-product meals of swine-origin in diet on olive flounder (Paralichthys olivaceus)

The increased global market value of fish meal (FM) and the overfishing of wild fishery resources have boosted efforts to identify protein sources that can be cheaply and reliably supplied as an alternative to FM, which is commonly used as a main protein source in fish diets. Numerous studies over the years have demonstrated that animal by-product meals are the effective alternatives for FM in fish diets. This study aimed to elucidate the effect of substituting FM with various by-product meals of swine-origin in diet on growth, feed utilization, chemical composition, plasma biochemical parameters, and superoxide dismutase (SOD) and lysozyme activity of juvenile olive flounder (P. olivaceus). All experimental diets were formulated with five isonitrogenous (56.5%) and isolipidic (10.0%) diets. The control (Con) diet included 65% FM and 12% dehulled soybean meal as the protein sources and 4.2% fish oil as a lipid source. Thirty percent of FM was replaced with plasma powder, heme powder, globin powder, and pork greaves meal, named as the PP, HP, GP, and PM diets, respectively. Three hundred and seventy-five juvenile (9.2 ± 0.01 g; mean ± SD) fish were placed into 15 flow-through tanks with three replicates. Fish were carefully hand-fed to apparent satiation twice a day for 56 days. At the end of the feeding period, weight gain and specific growth rate of fish fed the GP and PM diets were comparable to fish fed the Con diet. Feed consumption of fish fed the PP, GP, and PM diets was comparable to fish fed the Con diet. Feed utilization and condition factor of fish fed the HP diet were the lowest. Plasma biochemical parameters, chemical composition, amino acid profiles, and SOD and lysozyme activity of fish were unaffected by dietary treatments. Thus, GP and PM are the appropriate replacers for FM in the olive flounder diets, wherein 30% FM is substituted by diverse by-product meals of swine-origin.

Identification of lncRNA-based regulatory mechanisms of Takifugu rubripes growth traits in fast and slow-growing family lines

Family selection is an important method in fish aquaculture because growth is the most important economic trait. Fast-and slow-growing families of tiger puffer fish (Takifugu rubripes) have been established through family selection. The development of teleost fish is primarily controlled by the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis that includes the hypothalamus-pituitary-liver. In this study, the molecular mechanisms underlying T. rubripes growth were analyzed by comparing transcriptomes from fast- and slow-growing families. The expressions of 214 lncRNAs were upregulated, and those of 226 were downregulated in the brain tissues of the fast-growing T. rubripes family compared to those of the slow-growing family. Differentially expressed lncRNAs centrally regulate mitogen-activated protein kinase (MAPK) and forkhead box O (FoxO) signaling pathways. Based on the results of lncRNA-gene network construction, we found that lncRNA3133.13, lncRNA23169.1, lncRNA23145.1, and lncRNA23141.3 regulated all four genes (igf1, mdm2, flt3, and cwf19l1). In addition, lncRNA7184.10 may be a negative regulator of rasgrp2 and a positive regulator of gadd45ga, foxo3b, and dusp5. These target genes are associated with the growth and development of organisms through the PI3K/AKT and MAPK/ERK pathways. Overall, transcriptomic analyses of fast- and slow-growing families of T. rubripes provided insights into the molecular mechanisms of teleost fish growth rates. Further, these analyses provide evidence for key genes related to growth regulation and the lncRNA expression regulatory network that will provide a framework for improving puffer fish germplasm resources.

Growth of Pacific staghorn sculpin (Leptocottus armatus) is reduced at contaminated sites in the Lower Duwamish River, Washington

The Lower Duwamish River is a highly industrialized waterway flowing into the densely urbanized Puget Sound waterfront of Seattle, Washington, USA. The river has been profoundly altered from its natural state following more than a century of channelization, recurrent dredging, shoreline armoring, and pollution discharges. As part of a Natural Resource Damage Assessment addressing historical pollution at three designated Superfund sites (i.e., the assessment area), juvenile Pacific staghorn sculpin (Leptocottus armatus) were sampled throughout the lower river in order to evaluate injury from exposure to polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), and butyltins (BTs). Sculpin live in close association with the river sediments within and upriver of the assessment area. Fish were collected for analysis of contaminant concentrations in composited whole bodies and stomach contents, as well as individual fish health metrics including daily somatic growth rates measured from otoliths. Sediment contaminant concentrations were also measured at sites near to fishing locations. Fish growth rates varied from 0.65 to 1.05 mm/day, and were significantly lower at unremediated downriver sites compared to upriver and remediated locations. Sculpin growth rates were negatively correlated with concentrations of PCBs in fish bodies, PAHs in stomach contents, as well as PCBs, DDTs and PAHs in sediment. Mixed effects models for whole-body and stomach content contaminants showed positive correlations between growth rate and water temperature. Temperature was not a significant confounding variable for the relationship between growth rate and sediment contaminants. Overall, these results show that juvenile sculpin are harmed by contaminant exposure in the Lower Duwamish River. Furthermore, this study demonstrates the utility of using paired biological and chemical indicators of pollutant-induced injury in a resident fish to inform a complex Natural Resource Damage Assessment and associated restoration efforts.

Tracing growth patterns in cod (Gadus morhua L.) using bioenergetic modelling.

Understanding individual growth in commercially exploited fish populations is key to successful stock assessment and informed ecosystem-based fisheries management. Traditionally, growth rates in marine fish are estimated using otolith age-readings in combination with age-length relationships from field samples, or tag-recapture field experiments. However, for some species, otolith-based approaches have been proven unreliable and tag-recapture experiments suffer from high working effort and costs as well as low recapture rates. An important alternative approach for estimating fish growth is represented by bioenergetic modelling which in addition to pure growth estimation can provide valuable insights into the processes leading to temporal growth changes resulting from environmental and related behavioural changes. We here developed an individual-based bioenergetic model for Western Baltic cod (Gadus morhua), traditionally a commercially important fish species that however collapsed recently and likely suffers from climate change effects. Western Baltic cod is an ideal case study for bioenergetic modelling because of recently gained in-situ process knowledge on spatial distribution and feeding behaviour based on highly resolved data on stomachs and fish distribution. Additionally, physiological processes such as gastric evacuation, consumption, net-conversion efficiency and metabolic rates have been well studied for cod in laboratory experiments. Our model reliably reproduced seasonal growth patterns observed in the field. Importantly, our bioenergetic modelling approach implementing depth-use patterns and food intake allowed us to explain the potentially detrimental effect summer heat periods have on the growth of Western Baltic cod that likely will increasingly occur in the future. Hence, our model simulations highlighted a potential mechanism on how warming due to climate change affects the growth of a key species that may apply for similar environments elsewhere.

Influence of Diet Changes on the Condition and Physiological State of Juvenile Sea Trout (Salmo trutta)

Abstract The aim of the study was to determine the influence of diets (factor D) and the time period (factor T) during which they were applied on the growth performance and physiological condition (blood plasma hematological and biochemical indicators of stress and immunity) in juvenile sea trout (Salmo trutta; initial body weight approximately 73 g). The diet of the fish that was used prior to the experiment (formulated feed; initial fish sample) was modified as follows: a different formulated feed (group B), mixed feed (feed B + prey fish; group B/N), prey fish exclusively (group N). The fish from group A were given the feed that was used prior to the beginning of the experiment. During the 28-day trial neither factors D nor T influenced absolute or relative fish growth rates. Factor D significantly influenced hematological indicators and leukograms, while the phagocytic index and cidal ability were determined by the time test (factor T). Myeloperoxidase (AMPO) was related significantly with the influence of factors D and T and also with the interaction of D×T. A significant decrease in AMPO was noted after two weeks of the test in groups B, N, and B/N, but after four weeks this indicator did not differ from that confirmed in the initial fish sample. The factors tested influenced stress indicators, i.e., cortisol (D and T) and glucose (D). Significant increases in cortisol (group B) and glucose (groups A, B, and B/N) concentrations were noted after two weeks of the test. After the subsequent two weeks (four weeks of the test) these indicators also stabilized. Sea trout from aquaculture readily accept prey fish; however, changes in diet cause stress reactions such as temporarily reduced immunity. Thus, the procedure for preparing sea trout stocking material for release, which is to change the feed from formulated to natural (live fish), should last approximately four weeks.

Effects of Nutritional and Culture Medium-based Approaches for Aquaponics System with Bio-floc Technology on Pak Choi and Catfish Growth Rates

Aquaponics with bio-floc can potentially offer sustainable food production with zero waste as it allows farming plants and fish simultaneously, whereby the former use fish waste as their nutrient sources, while the latter receives cleaner water from the plants in a closed-loop system. In the aquaponics system, additional nutrients are usually added to support optimal plant growth, but it is suggested that the amount of such chemical nutrients should be controlled to prevent any harm to the fish. Furthermore, the plant and fish growth rates are influenced by the nutrients and the culture media used. This study aims to examine the effect of nutrition (full-nutrient and half-nutrient treatments) and different types of culture mediums (rockwool, rockwool-perlite, and rockwool-husk) on the growth rates of pak choi (Brassica rapa) and catfish (Clarias gariepinus) using split-plot design. Findings show that the half-nutrient treatment yielded a 17.12% higher plant growth rate and 23.87% heavier catfish weight than the full-nutrient treatment, but these treatments did not affect the fish survival rate. It was also observed that using different culture mediums did not result in any significant difference.