Fish Growth Parameters Research Articles

Growth, mortality, and exploitation rate of spadenose shark (Scoliodon laticaudus) landed at PPI Dumai, Riau Province

The IUCN Red List most recently evaluated the spadenose shark (Scoliodon laticaudus) in 2005 and classed it as near threatened. The research was done at fish landing locations at PPI Dumai between May and July 2023. The goal of this study is estimating spadenose shark growth, mortality, and exploitation rates. Total length and total weight were the kind of information that were collected. The frequency distribution formula was used to assess the frequency of fish length. The FISAT II program’s ELEFAN 1 was used to examine fish growth parameters. The result showed that there were 1103 fishes (590 females and 513 males) captured. The total length (TL) of spadenose sharks in May, June, and July respectively obtained the range between 251-470; 218-500, and 279-485 mmTL with a maximum length of 500 mmTL. With an assumed coefficient of determination (R2) of 0,68, the relationship between total weight (in g) and total length (in mm) for the combined sexes is estimated as W = 0,0001TL2,4582. The growth pattern of spadenose shark is negative allometric. Asymptotic length (L∞) = 578,2 TL, growth rate (K) = 0,51 y-1, and theoretical age at length 0 (t0) = -0,86 y were found as estimates of the growth parameters. Total mortality (Z) was 2,24 y-1, with natural mortality (M) at 0,52 y-1 and fishing mortality (F) at 1,72 y-1. The exploitation rate (E) for this fish was 0,77y-1, which indicates high levels of exploitation.

Effect different levels of safflower seed powder to the diets on some histological traits to the diets of common carp Cyprinus carpio L.

The study was conducted at special cages in mud pond, Agricultural Research and Experiment Station, Animal Production Department, Agriculture College, Al-Muthanna University, to study the partial replacement of safflower seed powder by levels of 0, 5, 10 and 15%, in the diets, instead barley and yellow corn, and the effects on the growth and blood parameters of common carp fish. The experiment was designed as four treatments with four replicates for each treatment (five fish/ replicate). The study included the effect of seeds on the histological parameters of carp fish, where the results showed histological examination of the organs of the liver, kidneys and gills, treatments of safflower seed powder fed at 5%, 10%, and 15% improved compared to T1 treatment. We conclude from this study the possibility of adding raw safflower seed powder by 10% to the diets of common carp fish Cyprinus carpio L.

Characterization of ingested MPs and their relation with growth parameters of endemic and invasive fish from a coastal wetland

Microplastic (MP) contamination is a persistent and ubiquitous threat to aquatic ecosystems. This study quantifies MP ingestion by fish inhabiting the Anzali Wetland (Iran), a hotspot of biodiversity. Growth parameters have been monitored in endemic demersal fish (Caspian spined loach, Sabanejewia caspia), and invasive benthopelagic species (Prussian carp, Carassius gibelio) in the wetland and compared with their internal content of MPs. MPs were extracted from the gastrointestinal (GI) tracts following digestion of the samples in alkaline medium and observation of the extracts with microscopy (Scanning Electron Microscopy equipped with an Energy-Dispersive X-ray microanalyzer (SEM-EDS) and confocal Raman microscopy). A total of 84.6 % of the study fish (n = 26) were contaminated with MPs. Fibres were the only type of MPs found in the GI tracts, and these were mainly dark blue and made of polycarbonate and nylon in both investigated species. The mean numbers of MPs in the GI tracts of the carp and the loach were 3.6 and 3.7 respectively. MPs had smooth surfaces in most cases although some presented brittle, fragmented, and uneven surfaces and signs of degradation. The growth rates of Carassius gibelio and Sabanejewia caspia, measured with the b value (growth factor), were 2.91 and 2.15 respectively. Carassius gibelio can play a significant role in the transport of MPs to other aquatic organisms inhabiting the Anzali wetland, and hence can cause potential harm to them. Carassius gibelio MP contamination was more pronounced with increasing gut mass in older specimens. Due to the presence of MPs and in fish that can be consumed, there could be a trophic transfer to humans. Regarding Sabanejewia caspia, although not statistically significant, their uptake of MPs tends to increase in older specimens with smaller size and body weight. This can imply that MP pollution causes inappropriate conditions and results in negative growth. The findings of this work provide new insights into MP contamination in the Anzali wetland, specifically in endemic fish. These results will be important in conservation and management programs.

Dietary effect of Lactobacillus plantarum (TISTR 912) on digestive enzyme activity, growth performance, immune response, and disease resistance of black sharkminnow (Labeo chrysophekadion) against Aeromonas hydrophila infection

This study investigated the influences of dietary supplementation of Lactobacillus plantarum (LP) on the digestive efficiency, growth performance, immunological response, and disease resistance of black sharkminnow (Labeo chrysophekadion) challenged with Aeromonas hydrophila (A. hydrophila). The fish (2.2 ± 0.14 g) were fed different doses of LP supplementation (0, 107, 108, and 109 CFU g−1) for eight weeks. The findings indicated that the digestive efficiency of fish fed various dietary LP levels increased significantly after both four and eight weeks of feeding (P < 0.05). The growth parameters of fish fed the 108 CFU g−1 LP diet were considerably greater (average of 1.3-fold) than those fed the control diet. All dietary treatments of LP supplementation substantially elevated lysozyme and peroxidase activities in both serum and skin mucus of the black sharkminnow compared to the activities of the control fish (P < 0.05). The highest level of digestive efficiency (1.71-fold), growth rate (1.3-fold), and immune response was obtained in fish fed the 108 CFU g−1 LP diet (P < 0.05) after four and eight weeks of the trial. Fish that consumed the non-LP dietary supplementation challenged with A. hydrophila had a survival rate of 30%, compared to a survival rate of 73.33–83.33% for those fed the LP dietary supplementations. Collectively, these findings suggest that dietary supplementation with L. plantarum at a concentration of 108 CFU g−1 in the black sharkminnow significantly improved growth rate, digestive enzyme activity, immunity, and disease resistance against A. hydrophila infection. However, the higher dose of L. plantarum (109 CFU g−1) in this study did not significantly improve the studied parameters. The findings suggested that L. plantarum can be potentially used as a functional feed additive in the black sharkminnow culture.

Performance of sustainable fish feeds in Benin for Clarias gariepinus (Burchell 1822)

Four sustainable feeds were formulated with locally available ingredients of Benin, produced by extrusion, chemically and physically characterized and their performance was explored. Formulated feeds (F1, F2, F3 and F4) and a Control Feed (CF) were fed to Clarias gariepinus juveniles for 16 weeks and fish growth parameters were monitored. Nutritional and sensorial qualities of the fresh and smoked fish were evaluated. Formulated feeds had the same levels of protein and carbohydrate contents and were similar to CF in this concern. The fat content of F2, F3 and F4 feeds was lower than that of the CF except for F1, which had similar fat content. All tested feeds had floatability rates exceeding 80%. The mean weight gain of the fish ranged from 168 g to 401 g. The best Feed Conversion Ratio was recorded with CF (1.01) followed by F2 (1.21). The Protein Efficiency Ratio of F2 (2.14) and CF (2.51) did not differ statistically. Fish fed with F2 had the best nutritional profile (protein: 682 g/kg, and fat: 231 g/kg) compared with fish fed on other feed formulas and the CF (protein: 634 g/kg, and fat: 274 g/kg). Smoked fish fed F2 and CF recorded similar acceptability from consumers.

Bio-active components in medicinal plants: A mechanistic review of their effects on fish growth and physiological parameters – A Review

Abstract World population is increasing at a tremendous rate so is the demand for animal-based protein. Aquaculture is a promising industry that has the potential to supply high quality protein for mankind with minimum environmental impact. In the past decade, aquaculture practices have been shifting from extensive to intensive culture. To achieve maximum production per unit area, high stocking densities are maintained in intensive aquaculture. If not managed properly, this may lead to stress in fish. Fish under stress condition show decreased growth, suppressed appetite, weakened immunity and increased susceptibility to infections. Chemicals, vaccines and antibiotics are used for the treatment of diseased fish. Use of synthetic chemicals, vaccines and antibiotics is not sustainable because pathogens develop resistance against them and they have high residues. Moreover, certain chemicals used for the treatment of fish diseases are not safe for humans therefore are banned in some countries. Plant parts and their extracts are used in traditional medicines to cure many diseases and to improve health of mankind. In aquaculture industry, use of plants and their derivatives in fish feed to improve health status of fish is increasing. Several plants improve growth and overall health status of fish, some provide protection against pathogens by improving the immune system while others increase appetite by direct action on neuro-endocrine axis of fish. This review provides an in depth and up-to-date information about use of medicinal plants and their derivatives to improve growth and physiological status of fish and their possible mechanism of action.

Indicators of Tuna Gigi Anjing (Gymnosarda unicolor) Growth Pattern on the Implementation of Sustainable Development Goals (SDGs)

Tuna is a type of large pelagic fish migrating and spreading in tropical and subtropical waters. In general, Indonesian waters are one of the tuna migration routes. The waters of the western part of Indonesia, especially the Simeulue Waters in the Fisheries Management Area (WPP) 572 Indonesia. One type of tuna was found there, namely Gymnosarda unicolor species, Family: Scombridae with the general name dogtooth tuna while the local name is tuna sisik bergigi, and or tuna karang. The sustainability of tuna fish resources can be threatened if the size of the fish stock is not known, one of which is the suitable size for catching. This study examined and identified the length and growth pattern of tuna gigi anjing that were landed in fish auction area of East Simeulue. The research was conducted in May-July 2021. The data collected was in the form of fork length data. The frequency of fish length to determine the class interval was analyzed using the frequency distribution formula. Fish growth parameters were analyzed using ELEFAN 1 contained in the FISAT II program. The number of tuna gigi anjing (Gymnosarda unicolor (Ruppell)) that was successfully measured was 190 individuals. The size of the fork length ranged in the interval of 44.1 to 101.3 cm. The length of first caught tuna gigi anjing (Lc) was at 59.2 cm, the asymptotic length (L) was 98.7 cm, the growth rate (K) was 0.8/year and the zero fish growth rate (t0) was of 0.09/year.

European seabass show variable responses in their group swimming features after tag implantation

The usefulness of acoustic telemetry on the study of movements, interactions, and behaviors has been revealed by many field and laboratory studies. The process of attaching acoustic tags on fish can, however, impact their physiological, behavioral, and growth performance traits. The potential negative effects are still unknown for several species and behavioral attributes. Previous studies have attempted to shed light on the effects of tag implantation on fish, focusing mainly on fish growth and physiological parameters, and one or two behavioral properties mainly on the individual level. However, the effect of this procedure could also be expressed at the group level. This study investigated the short-term effects of dummy and active body-implanted acoustic tags on the group-level swimming performance of adult European seabass (Dicentrarchus labrax) using optical flow analysis. We studied four main swimming performance properties—group speed, alignment (polarization), cohesion, and exploratory behavior. To help in the interpretation of any detected differences, physiological stress-related parameters were also extracted. The results show that the tag implantation procedure has variable effects on the different swimming performance attributes of fish. Group cohesion, polarization, and the group’s exploratory tendency were significantly impacted initially, and the effect persisted but to a lesser extent two weeks after surgery. In contrast, group speed was not affected initially but showed a significant decrease in comparison with the control group two weeks post-surgery. In addition, the physiological parameters tested did not show any significant difference between the control and the treated group 14 days after the onset of the experiment. The findings suggest that the effect of tagging is non-trivial, leading to responses and response times that could affect behavioral studies carried out using acoustic telemetry.

The Effects of Dietary Thyme Oil (Thymus vulgaris) Essential Oils for Common Carp (Cyprinus carpio): Growth Performance, Digestive Enzyme Activity, Antioxidant Defense, Tissue and Mucus Immune Parameters, and Resistance against Aeromonas hydrophila.

This study evaluated the effects of dietary supplementation of thyme (Thymus vulgaris) essential oil (TVO) on growth performance, digestive enzymes, biochemical parameters, hematological indices, liver enzymes, and pathogen resistance in common carp (Cyprinus carpio). Triplicate groups of fish (15.36 ± 0.10 g) were fed daily with diets supplemented with TVO at 0, 0.5, 1, and 2 percent for 60 days then challenged with Aeromonas hydrophila. The results determined that supplementation of thyme resulted in significantly higher final body weights (FBW) and lower feed conversion ratios (FCR). Furthermore, no mortality was observed in the thyme-supplemented treatments. Regression analysis showed that fish growth parameters were polynomially related to dietary TVO levels. The optimum dietary TVO level, based upon the varied growth parameters, was 1.344 to 1.436%. Digestive enzymes activity, including amylase and protease, significantly increased in fish fed the supplemented diets. The thyme-supplemented diets also significantly increased the biochemical parameters, including total protein, albumin, and acid phosphatase (ACP), compared to the control group. We also observed significant increases in hematological indices, including red blood cells (RBC), white blood cells (WBC), hematocrit (Hct), and hemoglobin (Hb) in common carp fed diets containing thyme oil (P < 0.05). Liver enzymes activity including alanine aminotransferase (ALT), alkaline phosphatase (ALP), and aspartate aminotransferase (AST) was also reduced (P < 0.05). Immune parameters, including total protein and total immunoglobulin (total Ig) levels, alternative complement pathway hemolytic (ACH50), lysozyme, protease, and ALP in the skin mucus, and lysozyme, total Ig, and ACH50 in the intestine were higher (P < 0.05) in TVO-supplemented fish. Catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx) in the liver were also elevated (P < 0.05) in TVO administered groups. Lastly, thyme-supplementation resulted in higher survival rates after the A. hydrophila challenge compared to the control (P < 0.05). In conclusion, dietary inclusion of thyme oil (1 and 2%) effectively improved fish growth, immune systems, and resistance to A. hydrophila.

Comparative analysis of the haemato‐biochemical parameters and growth characteristics of Oreochromis niloticus (Nile tilapia) cultured under different feed and habitats (biofloc technology and earthen pond system)

Assessing fish haemato-biochemical profile and growth performance is essential to monitor the influence of fish feed and habitat on fish physiology. The influence of two regularly used different commercial feeds and varied environments such as pond and biofloc systems on haemato-biochemical and growth parameters of Oreochromis niloticus was studied by the results of 4-month experiment. Fish ponds and biofloc systems where all the fish were supplied either feed A and B were surveyed weekly. The crude protein content of feed A was 30%, while that of feed B was 28%. Physico-chemical characteristics of water in all culturing systems were suitable for Nile Tilapia production throughout the study period. Results revealed a significant difference (p < 0.05) in most haemato-biochemical parameters. Growth performance was better in fish fed on feed A than feed B in both culture systems. In between, the habitat wide range of haemato-biochemical indices and fish growth parameters were significantly higher in biofloc technology than pond culture system. However, no significant difference (p > 0.05) was recorded in fish enzymatic activities in both systems. Furthermore, it was found that both the length and weight gain were positively associated with the crude protein of the feeds. However, in the case of biofloc, crude protein of both feeds works far better than the pond, as indicated by the p-value and regression R square. Current study delivers the basic knowledge to observe fish blood and growth parameters, which could be essential to understanding the fish culture management and environment.

Oleaginous yeast Rhodotorula toruloides biomass effect on the metabolism of Arctic char (Salvelinus alpinus).

Sustainability issues arise when using fish oil and vegetable oils in fish feed production for aquaculture purposes. Microbial production of single cell oil is a potential alternative as a lipid ingredient in the production of fish feed. In this study, we replaced the vegetable oils with the oleaginous yeast R. toruloides biomass in the diet of Arctic char (S. alpinus) and investigated the effects on health and composition. Measurement of fish growth parameters showed a higher liver weight and hepatosomatic index in the experimental group of fish fed partly with yeast biomass compared to a control group fed a diet with vegetable oils. No significant differences in the lipid content of muscle and liver tissues were found. The fatty acid profiles in the muscle of both fish groups were similar while the experimental fish group had a higher amount of monounsaturated fatty acids in the liver. Histology of livers showed no significant difference in the number of lipid droplets. The size of hepatic lipid droplets seemed to be related to liver fat content. Quantification of metabolites in the liver revealed no differences between the fish groups while plasma metabolites involved in energy pathways such as alanine, 3-hydroxybutyrate, creatinine, serine, betaine, and choline were significantly higher in the experimental fish group.

The effect of stocking density on sterlet Acipenser ruthenus (Linnaeus, 1758) larvae in the recirculating aquaculture system

Increasing the number of fish stocked might optimize the efficiency of intensive aquaculture systems however at the same time might have a negative impact on fish welfare and growth parameters. In the current study, three different stocking densities were evaluated in duplicated tanks to investigate the effect of different stocking densities on the survival and growth of sterlet larvae from hatching until the end of weaning, during the 30-day trial. Tested densities were 5, 10, and 20 larvae L−1 in the low (L), medium (M), and high (H) density group, respectively. Freshly hatched larvae (1250, 2500, 5000 larvae per duplicated tanks) were divided into three treatment groups in 250 L raceway larval rearing tanks. The fish biomass gain was significantly higher in each group of higher stocking densities (0.2 ± 0.0 g L−1; 0.4 ± 0.0 g L−1 and 0.8 ± 0.1 g L−1 respectively, r = .990, p < .001). The L group showed a tendency towards better growth during the first 3 weeks, however, at the end of the trial, no significant differences were observed. The highest mortality at the start of exogenous feeding was noticed in group H (12.77% ± 1.3%) and was significantly different from the two lower density groups (5.16% ± 1.3% in L, 7.94% ± 1.3% in M), however, the overall mortality at the end of the trial did not differ among groups. Results on both growth and mortality during the later periods are suggesting the adaptability of sterlet larvae to the more intensive rearing conditions. Thus, it can be stated that the application of a stocking density of 20 larvae L−1 is appropriate in the initial period of larval rearing in the sterlet.

Dietary Fish Meal Replacement with Hermetia illucens and Tenebrio molitor Larval Meals Improves the Growth Performance and Nutriphysiological Status of Ide (Leuciscus idus) Juveniles.

Simple SummaryThe success of wild fish conservation strongly depends on the development of effective methods for restocking material rearing. An essential element in this process is the nutrition of juvenile stages of fish in controlled conditions, requiring the optimization of diet composition to meet specific nutritional and behavioral requirements. This study aimed to evaluate the possibility of using insect-derived meals as an alternative to fish meal in diets for the ide (Leuciscus idus) juveniles. Insects are a significant part of omnivorous fish diets, such as the ide natural diet, so their usage in aquaculture is strongly justified. Insect larval meals of two insect species, namely, black soldier fly and mealworm, improved the growth, feed utilization, and health of ide juveniles. However, superworm larval meal negatively affected the abovementioned parameters and is not recommended for the diet of juvenile cyprinid fish.The ide (Leuciscus idus) is a native European species of rheophilic cyprinid fish whose wild population status is dependent on conservation efforts, particularly regular restocking. This study aimed to evaluate the effects of including insect meals as a component in the diet of ide juveniles on their growth performance, feed utilization, and nutriphysiological status. Four diets were formulated: three with insect meals, HI–with 20% Hermetia illucens meal, TM–with 20% Tenebrio molitor meal, and ZM–with 20% Zophobas morio meal, and the control group diet, CON–fish meal with no insect component. The effects of the various diets on the efficiency of rearing ide juveniles were assessed based on fish growth parameters, feed utilization parameters, somatic indices, and intestinal and hepatopancreatic histomorphology. The highest increase in fish weight gain and the protein efficiency ratio was observed in the HI and TM groups, while the lowest values were observed in the CON and ZM groups. Comparable results were noted for the feed conversion ratio, which was most favorable in the HI and TM groups and increased in the ZM group. The use of black soldier fly and mealworm larval meal in the diets of ide juveniles had a positive effect on rearing results and overall fish health.

Effect of foliar application of potassium with aquaculture wastewater on the growth of okra (Abelmoschus esculentus) and Pangasianodon hypophthalmus in recirculating aquaponic system

A 90-day experimental trial was conducted to evaluate the effect of foliar potassium application with aquaculture wastewater on the growth performance of okra and Pangasianodon hypophthalmus in a media-based recirculating aquaponic system. A completely randomized design (CRD) in triplicates was followed with a fish to plant ratio of 4.7 kg/m3: 6 okra plants per tank. The potassium dosages of 0, 2, 3, 4, and 5 g/L were applied twice a month in control, T1, T2, T3, and T4, respectively. The water quality parameters remained within the favorable limit for aquaponic production. The results showed that the overall growth of okra viz., plant height, leaf number, length, and width was significantly higher in the treatments, particularly in T3 and T4 compared to other treatments and the control. The treatment T4 showed the significantly highest yield (31.26±0.78 g/plant) compared to the control (7.25±1.30 g/plant). The okra yield, pod number per plant, and average weight per pod were significantly influenced by potassium dosage with the highest value observed in T3 (4 g/L) and T4 (5 g/L). The potassium dosage also impacted the branching pattern of okra with the highest number of branches observed in plants sprayed with 4 g/L (T3) and 5 g/L (T4) while control showed no branching. The proximate and mineral composition showed significantly higher crude protein (13.57±0.32%) and potassium content (2306.70±37.76 mg/100 g) in okra pods in T4; while potassium and sulfur content of leaves was found to increase with the increased dosage of potassium application. The fish growth, hematological and antioxidant enzymes parameters showed no significant difference in all the treatments and control. The present study recommends a 5 g/L foliar potassium dosage to enhance okra growth and yield without impairing fish growth performance in okra-P. hypophthalmus aquaponics.

Taurine supplementation in plant-based diets for juvenile rainbow trout (Oncorhynchus mykiss): Effects on growth performance, whole body composition, and histomorphological features

Taurine supplementation in plant protein-based diets has been reported to improve growth performance, feed utilization, whole body composition, and gut integrity in carnivorous fish species, but data in rainbow trout are quite scarce. This study aimed to investigate the effects of plant protein-based diets supplemented with different levels of taurine on rainbow trout growth performance, whole body composition, and histomorphological traits of the intestine and main organs. In a 71-day trial, 340 juvenile rainbow trout were randomly distributed to 5 dietary treatments (4 replicate tanks/diet, 17 fish/tank): two control diets (a fishmeal-based diet [positive control; C+] and a soybean meal-soy protein concentrate-based diet [negative control; C-]), and three experimental diets in which the C-diet was supplemented with 2.5, 5 and 10 g/kg of taurine (T2.5, T5 and T10, respectively). At the end of the trial, growth parameters were assessed, and whole fish (12 pools of 3 fish/diet) and gut, liver and kidney samples (12 fish/diet) were collected for whole body composition and histomorphological analyses, respectively. Liver (8 fish/diet) was also sampled for taurine quantification. The fish fed the T10 diet showed higher weight gain, protein efficiency ratio, and specific growth rate – as well as decreased feed conversion ratio – when compared to the C+ group only (P < 0.05), thus suggesting a main effect of the taurine source on the response. The T2.5 rainbow trout showed lower moisture content and increased ether extract and ash contents than the other dietary treatments (P < 0.001). Higher crude protein content was also observed in fish fed the C- and T10 diets in comparison with the other groups (P < 0.001). Hepatic taurine levels were increased in the C+ group when compared to the C-, T2.5 and T5 diets (P < 0.05), with higher contents being also identified in the T10 group than the C- diet (P < 0.01). Differently, gut morphometric indices and histopathological features of the gut, liver, and kidneys were unaffected by dietary taurine supplementation (P > 0.05). In conclusion, dietary taurine supplementation in juvenile rainbow trout fed vegetable protein-based diet is capable of influencing the growth performance and the whole lipid content of the animals, without affecting the histomorphological traits of the intestine, the liver and the kidneys. In particular, the 2.5 and 10 g/kg supplementation levels seem to be capable of exerting the most pronounced effects in terms of composition of the fish body mass and growth parameters, respectively.

Less impact than suspected: Dietary exposure of three-spined sticklebacks to microplastic fibers does not affect their body condition and immune parameters

Microplastic fibers are frequent anthropogenic contaminants in most aquatic environments and have consequently been detected in the digestive tract of many fish species. Upon ingestion, microplastic fibers pose risks of interference with nutrient uptake, impaired intestinal health, and as a consequence may alter growth performance and fitness. In addition, foreign particles such as fibers might cause tissue irritations and stress, and thus interfere with immune parameters. In nature, fish regularly encounter microplastic fibers as well as fiber debris from natural sources and materials. Thus, we wanted to test the potential impact of microplastic fibers on growth, organosomatic indices, and immune parameters of subadult fish and compare these to possible effects caused by natural fibers. We administered sticklebacks diets, which were supplemented with either polyester or cotton fibers (each at concentrations of 0.2 mg/g and 2 mg/g feed) or a control diet without fiber supplementation for nine weeks. Mortalities did not occur and sticklebacks grew equally well across treatments. Neither organosomatic indices nor immune parameters revealed significant differences between treatments. While natural differences between males and females were observed for some parameters, no treatment-related gender-specific effects were detected. Our results suggest that the dietary uptake of polyester fibers does not affect growth, body condition, gonad development, and immunity of sticklebacks – even at fiber concentrations higher than what can be encountered in the wild. Furthermore, virgin microplastic fibers do not seem to affect fish differently than fibers from natural origin. The present study implies that at least some species are resilient towards pollution with (virgin) microplastic fibers even at high concentrations.

Modeling and Simulation of Aquaculture Systems

In this work, models for aquaculture are developed with regard to their relevance in an automated recirculation system. The three subsystems fish, water, and feed are determined as modular components. A selection of relevant variables is determined. The relationships between feed, water quality, and fish growth are described on the basis of an initially qualitative description (causal network) and quantified using ODEs. The considered water treatment systems and control devices are used to describe the relationships between filtration, fresh water addition, and water quality. The numerical system model allows simulations of the overall system behavior in time domain including the full growth phase offish. As example, the conditions using rainbow trout are simulated in a recirculating system. Influences of different variables like water temperature, pH-value, or protein content in dependency of the fish feed variables are shown, as well as the influence of plant parameters. This allows a recording of water quality and also to monitor the optimal fish growth or well-being parameters. The developed model can be extended modularly and allows further considerations and analyses for the control of the plant volume flow or for carbon dioxide gassing.

Spatiotemporal and bioecological distribution of four commercial Mullid species in an ultraoligotrophic Mediterranean gulf

This study provides baseline data on the mullid fish assemblages based on their morphometries on a shelf of the most oligotrophic water of the Mediterranean Sea, Antalya Gulf. The distribution of fish abundances, biomasses, total length, sex composition, growth parameters, and ecological fish assemblages was studied along three transects (each had a series of bottom depths of 10, 25, 75, 125, and 200 m) between spring 2014 and winter 2015, representing the winter, spring, summer and autumn seasons. Four different species of the Mullidae family: the red mullet (Mullus barbatus), the striped red mullet (M. surmuletus), the golden-banded goatfish (Upeneus moluccensis) and the Por's goatfish (U. pori) were found and subjected to distributional analyses. Excluding M. surmuletus, all of the mullid fish were commonly and abundantly found. There was a definite depth segregation among their distributions, but no seasonal differences occurred. Mediterranean meadows are attractive areas for mullid species, especially for M. surmelatus. The spatial distributional pattern of U. pori was in complete contrast to that of M. surmuletus. Overall, the females (F) outnumbered the males (M) significantly in space (region and depth) and time (season). The morphometric parameters (length-related and growth parameters) were estimated to increase comparatively from east to west in the Mediterranean Sea. Ecologically, the mullid assemblages depended on the seafloor depth, bottom type (habitat and sedimentary characteristics), water productivity and dissolved oxygen content and salinity, and benthic composition.

On-farm participatory evaluation of feeding approaches used by farmers for tilapia (Oreochromis macrochir) production in northern Zambia

This paper reports the first benchmarking of smallholder tilapia farming practices in rural northern Zambia, measuring fish growth, feed utilization and water quality parameters, using a participatory action research approach. The effects of three different feeding regimes that are currently used in smallholder farming systems in northern Zambia on the growth of the native tilapia, Oreochromis macrochir, were tested with 15 farmers (40% female), each having three ponds (one pond per feed treatment per farmer = 45 in total), over eight months in 2016–2017. The three feed treatments included: (1) formulated feed only comprising maize and soybean; (2) goat manure only; and (3) formulated feed and manure together. Three hundred (300) O. macrochir mixed-sex fingerlings, 0.5 ± 0.1 g average weight, were stocked in each pond. Water quality (pH, dissolved oxygen, and water temperature and transparency) was measured monthly, as was fish growth in each pond by randomly sampling thirty (30) fish and taking individual weights and lengths. Results showed that the water quality parameters were broadly similar in the different feed treatments over the eight-month experiment period, except for the water transparency values that were higher in the feed only treatment when compared to the other two treatments at months four through eight. Means for survival rate, weight gain, specific growth rate, total amount of fish harvested, and yield were all higher for the feed and manure together treatment than the other two feed treatments at the end of the experiment. A linear mixed-effects regression analysis that controlled for several fixed effects and included pond as a random effect found that the feed and manure together treatment increased fish growth by 10.8 ± 3.7 g at month eight compared to the manure only treatment. The analysis also found a negative effect on fish growth (−9.4 ± 3.8 g) in ponds that used the feed only treatment. The pond effect accounted for 10.1% of the total variance in the data at month eight. Future research and development efforts in Zambia should examine more closely the factors that influence fish growth and that make up the pond effect to determine which innovations and better management practices could help smallholder farmers increase the productivity of their ponds.

Effects of synthetic androgen (17α-methyltestosterone) and estrogen (17β-estradiol) on growth and skin coloration in emperor red cichlid, Aulonocara nyassae (Actinopterygii: Cichliformes: Cichlidae)

In recent years, the use of anabolic steroids in the coloration and growth of fishes, especially ornamental ones, has attracted great interest. In the ornamental fish industry, it is economically advantageous to produce some species with high commercial value and higher demand, depending on size, color, and sex. Therefore, the most commonly used steroids in this study—i.e., 17α-MT and 17β-Es (E2)—were added to the diet of emperor red cichlid,Aulonocara nyassaeRegan, 1922, which has not been previously hormone-treated and has high economic value amongst ornamental fishes. A 60-day study was conducted in a closed system, where the juveniles of the emperor red cichlid were acclimatized with the control/basal diet for 15 days. After which, 15 fish with a similar shade of color and about 5 months old were weighed individually (0.71 ± 0.01 g). All fish were placed into aquaria (30 L) in five different groups, in triplicate. Five different groups consisted of control (without hormone), 50 mg · kg–117α-MT, 100 mg · kg–117α-MT, 50 mg · kg–1E2, and 100 mg · kg–1E2. The fish were fed a diet twice a day (10:00 h, 17:00 h) for 60 days till satiation. During the entire trial period, a 12 h light–12 h dark photoperiod was maintained. Water temperature was measured daily and recorded. Growth parameters of experimental fish were calculated. The color measurement of fish skin (L*,a*,b*values) from around the dorsal section was performed using a colorimeter (Konica Minolta CR 400). Significant differences were determined in the following parameters: weight gain (WG), specific growth rate (SGR), feed conversion rate (FCR), survival rate (SR), condition factor (CF), and sex reversal. The fish group fed with 17α-MT displayed brighter coloration as compared to other groups. Color analysis (instrumental) in terms ofL*,a*, andb*, values showed that the group fed with 17α-MT displayed brighter coloration compared to other groups (P&amp;lt; 0.05). In terms of sex reversal, the fish in the 17α-MT groups exhibited 100% masculinization, whereas in E2supplemented fish groups (50 and 100 mg · kg–1), the feminization rates were 88.88% and 93.33%, respectively. In conclusion, both hormones were found to have positive and negative effects for this fish species, but the 17α-MT hormone was found to be more effective in reversing skin pigmentation, growth, and sexing, which is the main driver in the ornamental fish trade.