Juvenile Fish Research Articles

Supplementing lysolecithin in corn-oil based diet enhanced growth and improved body biochemical composition in juvenile stellate sturgeon (Acipenser stellatus)

A 56-days nutritional trial was conducted to examine the influence of including a corn-oil based diet with lysolecithin (LL) on stellate sturgeon (Acipenser stellatus) juveniles. Fish were fed four experimental diets (44% crude protein, 15% crude lipid) containing graded levels of LL [0 (control), 0.5, 1 and 2%)]. One hundred and eighty juvenile fish (45.3 ± 0.1 g, mean ± standard deviation) were stocked in twelve 300 L-polyethylene tanks containing ground water at 18.9 ± 0.5°C. Feeds were offered to fish at apparent satiation four times daily. Fish fed 1% LL-supplemented diet had higher growth and better feed conversion ratio than the control group (P < 0.05). The amounts of protein and lipid levels in the whole body increased in fish fed LL-supplemented diets compared to control, whereas the levels of n-6 PUFA, particularly linoleic acid, increased in fish fed 0.5 and 1% LL-supplemented diets. Total long chain polyunsaturated fatty acids increased in fish fed 1% LL-supplemented diet. Regarding digestive enzymes, trypsin (alkaline pancreatic proteases) and pepsin (acid gastric protease) activities decreased with increasing LL in the diet. Overall, these results indicated that 1% LL is recommended for better growth performance of stellate sturgeon juveniles.

Use of otolith microchemistry signatures to assess the habitat use of Centropomus undecimalis in lagoon systems of the southwest Atlantic

The common snook, Centropomus undecimalis, is a catadromous species that is economically important for the southwest Atlantic artisanal and recreational fisheries. Their complex movement patterns and habitat use preferences are not fully understood in the Brazilian Atlantic waters, raising some issues regarding the rational and sustainable management of the fisheries. The present study aimed to identify the habitat use by C. undecimalis individuals captured in four coastal lagoon systems in the Eastern Rio de Janeiro state, Brazil. Sixty individuals were collected in the lagoon systems of Itaipu, Maricá, Saquarema and Araruama, between November 2019 and March 2020. A selection of 15 individuals per site from the same age group (3 years old), following age estimation by counting the annual growth increments, were used. Elemental signatures of the otolith’s cores and edges were obtained using laser ablation inductively coupled-plasma mass spectrometry (LA-ICP-MS). Data were analyzed using univariate and multivariate statistics to assess the degree of separation among individuals regarding the natal origin (otolith cores) and moment of capture (otolith edges) from the sampling sites. Elemental signatures exhibited distinct spatial patterns, driven by Ba/Ca, Li/Ca and Sr/Ca in the otolith cores and Ba/Ca, Li/Ca, Mn/Ca and Sr/Ca in the edges. A low reclassification was recorded for the otolith’s core (overall: 45%; by lagoon: 53% Saquarema, 53% Maricá, 47% Itaipu and 27% Araruama). However, a highest overall reclassification was observed for the otolith’s edge (overall: 65%; by lagoon: 73% Itaipu, 73% Saquarema, 60% Maricá, and 53% Araruama). Differences between otolith core and edge signatures within locations were detected for Ba/Ca, Cu/Ca, Li/Ca, Mn/Ca and Sr/Ca ratios. The results obtained indicate an ontogenetic habitat shift, with a similar natal origin of the individuals probably due to marine water influence, and discrimination of heterogeneous juvenile fish groups driven by distinct phenotypic characteristics of the lagoons.

Trace elemental and stable isotopic signatures to reconstruct the large-scale environmental connectivity of fish populations

Animal movements and connectivity across different environments constitute essential components of virtually all ecological and evolutionary processes. In the present study, we measured multiple trace-element profiles and stable isotopes to reconstruct life cycle patterns of Eleutheronema rhadinum, and patterns of connectivity among populations of E. rhadinum across 3 distinct ecoregions in the eastern China Sea. Our results indicated that E. rhadinum larvae from different regions exhibited distinct otolith core levels of trace elements and stable isotopes, serving as discriminative markers of geographical origin. We used the maximum likelihood approach and linear discriminant analysis to trace back the origins of the mixed adult fish stocks. After leaving their nursery areas, juvenile fish from colder northern regions migrated south to overwinter in the South China Sea, where they mixed with the local populations. After overwintering, the adult fish began their long journey north, with the migrating population including individuals of both East China Sea and South China Sea origins. Meanwhile, fish in the Beibu Gulf exhibited a lower degree of interaction with the South China Sea populations and minimal interaction with those in the East China Sea. Trace elements and stable isotopes revealed the spatiotemporal connectivity of E. rhadinum across the 3 different ecoregions. This study provides critical information on how marine connectivity supports temperature-mediated fish community movement patterns within coastal ecosystems.

Estimating enhanced fish production on restored shellfish reefs using automated data collection from underwater videos

Abstract Shellfish reefs across the world have been heavily degraded by mechanical harvesting, disease and declining water quality. In southern Australia, where substantial losses have occurred, government and non‐government efforts to restore functioning reefs are now underway with a strong focus on enhancing fish productivity. However, the capacity of these restored reefs to enhance fish production remains unknown, hampering estimates of return on investment. We quantify the density differences of newly recruited juvenile fish and other nekton on these restored reefs, relative to those on unrestored, unstructured habitat. Fish were surveyed at three paired reef‐unstructured locations using 169 unbaited stereo video deployments during three periods over 12 months (2022–2023). We used automation software, FishID, to automatically identify, size and count fish in videos. We subsequently applied known growth and mortality parameters to model enhancement of fish productivity. Sixteen species occurred as new recruits, with all but two found at higher densities on reefs than unstructured habitat. Enhancement of fish production from subtidal restored shellfish reefs from a single year's cohort is estimated to be, on average, 6186 kg ha−1 year−1 (SD 1802) after enough time has elapsed for all species to have matured. Species harvested commercially or recreationally contributed 98% of that production (6083 kg ha−1 year−1, SD 1797). Enhancement varied greatly among locations, ranging from 12,738 kg ha−1 year−1 (SD 2894), which is the highest yet recorded anywhere, to 1.4 kg ha−1 year−1 (SD 0.9). The lack of juvenile fish at the location with the lowest estimated enhancement might be explained by the impact of overfishing on recruitment of key species or by an abundance of alternative habitat for juvenile fish. Synthesis and applications. The combination of underwater videos with automated data extraction provides a reliable, cost‐effective method for surveying fish on oyster reefs. By quantifying enhanced fish productivity on reefs, we provide estimates that will underpin calculations of ecological, social and financial benefits, supporting the business case for scaling‐up restoration efforts.

Diversity of Fish and Decapod Fry in the Coastal Zone of Amvrakikos Gulf

Amvrakikos Gulf and its surrounding coastal lagoons are of primary importance for the local biodiversity and fishing activities. Fish species inhabited the coastal lagoons based on the seasonal ongoing migration movements of fry and adult fish individuals from the sea towards the lagoons. Information on the early stages of fish and decapod species in the Amvrakikos Gulf is limited only to the planktonic ontogenetic stages and reproduction biology, respectively. The aim of this study was to describe the spatial distribution of fry from commercially important fish and decapod species in the coastal zone of Amvrakikos Gulf. The seasonal appearance of the early stage of the most commercially important fish species caught in the coastal zone of the gulf ranged from one to four seasons, depending on the species. Individuals of all ontogenetic stages (fry, juveniles, and adults) were reported for several species (A. boyeri, A. fasciatus, S. abaster, S. tyfle, and B. ocellaris), indicating that these species may be regarded as residents in the coastal zone, providing habitats for their entire life cycle. The average relative abundance of the species/genera exhibited no differences compared to other Greek brackish waters. The species composition in the Amvrakikos Gulf at 10 cm and above was in agreement with the transitional nature of the area, with permanent and occasional species present. The present study emphasizes the importance of the coastal zone as a nursery habitat for commercially important species.

The length-weight relationship and condition factors of coastal small-sized adult and juvenile fish species following dense mucilage in the Sea of Marmara, Türkiye

The length-weight relationship and condition factors of coastal small-sized adult and juvenile fish species following dense mucilage in the Sea of Marmara, Türkiye

Genetic identification of juvenile pink salmon Oncorhynchus gorbuscha (Walbaum) of the odd-year reproduction line on results of restriction analysis of mitochondrial DNA and analysis of single-nucleotide polymorphism

Data on the regional composition of mixed marine aggregations of juvenile pink salmon during postcatadromous migrations in the basin of the Sea of Okhotsk in 2022 are demonstrated. A high probability of a significant predominance is revealed for pink salmon spawning returns 2023 of the northern stock complex compared to the southern ones. Identification estimates for juvenile fish obtained from RFLP analysis of mtDNA and analysis of allelic variability of SNP loci are compared to the values of actual regional catches and spawning returns. Close correspondence between the calculated estimates and actual data on the results of the 2023 fishing season was noted. Forecast about predominance of pink salmon of the northern stock complex, as well as about atypically low proportion of fish from water bodies of Iturup Island is fully confirmed. The estimates for Sakhalin Island and the southern part of the continental coast of the Sea of Okhotsk are close to the actual catch.

Evaluating the context dependency of large river nursery habitats for fishes in the lower Red River catchment

AbstractBoth fine‐ and coarse‐scale physicochemical conditions affect the quantity and quality of nursery habitats within riverine ecosystems. Nursery habitats in large, braided, and sandbed streams such as the lower Red River of Oklahoma, Texas, and Arkansas are not well described and likely vary among species. Identification of nursery habitats is important for developing proper conservation and management actions. We used an occupancy model framework to determine how hierarchical habitat factors related to the occupancy of 38 juvenile fish species. Our findings indicate that large river nursery habitats can generally be defined by reaches with off‐channel slackwater habitat, having deep pools but shallow thalweg depths, typically located further away from dams, and with low percentages of limestone lithology. Species within the same genera often exhibited variable relationships with river slope, amount of large woody debris, channel shape, discharge, and position of reaches within the stream network. Our results indicate important species‐specific relationships that define nursery habitats, indicating an important context dependency of nursery habitats even within fishes that are taxonomically similar. If the goal is to improve recruitment by native fishes, then consideration of the important species‐specific differences would be beneficial if improvements are made to nursery habitats. Moreover, careful consideration of the effects of dam operations will help maintain proper connectivity to off‐channel habitats important in downriver portions of the river network.

Plant-based carotenoid supplementation: Growth, feed utilization efficiency, and coloration in false clownfish (Amphiprion ocellaris)

The false clownfish (Amphiprion ocellaris) is a prominent species in the marine ornamental trade, valued for its vibrant orange-red coloration. However, aquaculture-bred individuals often exhibit less intense coloration than their wild counterparts, presenting a challenge for both breeders and aquarists. This study evaluates the effects of carotenoid-enriched diets, sourced from natural ingredients such as pumpkin, bell pepper, carrot, and gac, as well as a synthetic source like astaxanthin, on the coloration and growth of false clownfish. In a controlled experiment, juvenile fish with an initial average length of 3.21 ± 0.03 cm and weight of 0.61 ± 0.02 g were allocated to 60-liter tanks and fed the experimental diets over a 75-day trial period. Carotenoid supplementation was standardized at 250 mg/kg across diets, with a control group receiving no added carotenoids. The experimental design was completely randomized, involving three replicates per dietary treatment. The results indicated that diets supplemented with gac and bell pepper significantly enhanced growth and feed efficiency (p &lt; 0.05). Notably, the skin redness intensity (a* value) was increased by 75.73% in the gac-supplemented group, 89.20% in the bell pepper group, and 91.99% in the astaxanthin group, relative to the control (p &lt; 0.05). Additionally, carotenoid deposition in the integument was significantly higher in all supplemented groups, with an increase of 83.74% in the astaxanthin group, 89.59% in the gac group, and 98.43% in the bell pepper group, compared to the control (p &lt; 0.05). These findings suggest that natural carotenoids, particularly from gac and bell pepper, can be effective alternatives to synthetic astaxanthin, potentially improving the attractiveness and commercial value of captive-bred false clownfish and alleviating the exploitation of wild populations.

Larval fish community in the Bay of Whales (eastern Ross sea): Species composition, relative abundance and spatial distribution

Early life stages of fish represent a key component in the food chain of the pelagic ecosystem of the Southern Ocean, connecting producer trophic levels to those of higher predators. Pelagic larvae and early juveniles of notothenioid fishes overwhelmingly dominate the ichthyoplankton community living on the continental shelf. Scientific research surveys targeting early life stages of fish in the pelagic realm have been mainly carried out in the western Ross Sea, whereas the eastern side can be considered unexplored. As source of high primary production, the presence and timing of formation of wide ice-free areas throughout the year in the Ross Sea play a fundamental role in structuring larval fish community. The Ross Ice Shelf Polynya (RISP) is a large coastal polynya, which is driven and maintained by local prevailing winds and oceanic currents. In the present study, we report the first data on species composition, relative abundance and spatial distribution of larval fish community found off the Bay of Whales in the eastern Ross Sea. As reported for other areas of the Ross Sea, the Antarctic silverfish Pleuragramma antarcticum was by far the most abundant species, followed by other nototheniids and channichthyids in smaller amounts. The huge abundance of P. antarcticum early larvae supports the hypothesis of a potential nursery area near the Bay of Whales. Present results strongly advocate for future investigations in these poorly known and remote areas.

EFFECT OF INFORMATION UTILIZATION ON FISH FARMERS’ LEVEL OF PRODUCTION IN ABEOKUTA NORTH LOCAL GOVERNMENT AREA, OGUN STATE, NIGERIA

The use of information on improved fish farming techniques has been seen to be ineffective due to the inability of the farmer to comprehend information passed across to them which is reflected on the continuous reduction in fish production and the reason why it seems like there is no positive effect of the information utilized by fish farmers on their productivity; hence, this study examined the effect of information utilization on fish farmers’ level of production in Abeokuta north local government area, Ogun state, Nigeria. A total of 80 respondents were selected. Primary data were collected with the use of a well-structured questionnaire and interview schedule. Both descriptive and inferential statistics were employed for the study. Mean age of respondents was 46 years. Furthermore, majority were male which had tertiary education and kept Catfish. The mean income earned was #858, 275. Commonly used improved fish farming practices were feed formulation technique and feeding operation. This study found an average increase in output-to-input ratio to be 0.68 kg per fish fingerlings stocked (nearly two-fold increase; 0.29 kg per fish fingerlings) after utilization of information. Profit increase/improved income of fish farmers through information utilization on improved fish farming practices was found to be positively correlated with years spent schooling, stocking rate before information utilization, stocking rate after information utilization at 5% level of significance, and annual income while output before information utilization and output after information utilization at 1% level of significance. The study concluded that information utilization on improved fish farming practices had positively influenced (harvest) output of catfish farmers in the study area. The study recommends that extension agent to farmer ratio needs to be improved on, so that regular and prompt visits could be made to fish farmers to intensify information utilization on improved fish farming practices.

Reef effect of vertical relief on the shelter-seeking and foraging processes of juvenile fat greenling (Hexagrammos otakii) in a mesocosm experiment

Artificial reefs with sufficient vertical relief can support secondary fish production by attracting pelagic fishes and/or providing both shelter and food resources for them. Although vertical relief is a widely investigated factor in reef design, little is known about how the shelter-seeking and foraging processes of benthic fishes respond to relief changes. With a laboratory mesocosm experiment using hollow blocks to construct different combinations of reef volume and relief, we tested the effect of vertical relief of artificial reefs on a benthic juvenile fish (fat greenling, Hexagrammos otakii). The volume of the experimental reef depended on the number of blocks, and the reef relief was changed by the stacking pattern of the blocks at each volume. We measured the aggregation, sheltering, and foraging effects of each reef structure, respectively, based on fish distribution around the reef, their shelter-seeking behavior under disturbance, and their foraging rate. Our results demonstrate that increasing the vertical relief while maintaining the reef volume had a positive effect on the aggregating juvenile fat greenling but decreased the sheltering effect of the reef. The relationship between the foraging effect and relief was nonlinear, and high relief would also limit the foraging rate of juvenile fat greenling. We suggest that a reef needs to have sufficient relief to provide habitat for juvenile fat greenling, as well as sufficient horizontal cover to shelter the fish during a disturbance. Not only limited resources (e.g., food and shelter) but also the shelter-seeking and foraging processes of the benthic fish could have a potential impact on secondary production. Our findings highlight the importance of considering the aggregation, sheltering, and foraging effects of relief on benthic fishes in the field observation and the design of artificial reefs.

Quality evaluation of fried fish sold in Katsina metropolis

Quality evaluation of fried fish sold in Katsina metropolis

THE EFFECT OF ADDITIONAL DOSES OF CURCUMA FLOUR (Curcuma xanthorrhiza Roxb) IN FEED ON THE GROWTH OF GOURAMY (Osphronemus gouramy) FRY

The purpose of this study was to determine the optimum content of the addition of curcuma flour with different doses to the feed on the growth of gourami fry (Osphronemus gouramy). The method used in this study was a completely randomized design (CRD) experimental method, which consisted of 5 treatments with 3 replications. The treatment used was treatment (A) without giving curcuma flour (control), (B) giving curcuma flour at 2.5%/kg feed, (C) giving curcuma flour at 5%/kg feed, (D) giving curcuma flour ginger at 7.5%/kg feed, (E) giving curcuma flour at 10%/kg feed. The results of analysis of variance (Anova) showed that the addition of the flour at different doses had a significant effect (P&lt;0.05) on the growth of gouramy fish fry. The results showed that the addition of curcuma flour at 7.5%/kg of feed gave the best results with the highest absolute weight growth of 15.11 ± 0,42 g, the highest absolute length growth of 3.92 ± 0,42 cm, the feed conversion ratio of 1.95 ± 0.11, and survival of 100%. Keywords: Gouramy fish, curcuma flour, growth, feed.

Four-Eyed Fish (A. anableps) Fingerlings Demonstrated Multiple Birth Defects Suggestive of Nutritional Deficiencies

In a colony of four-eyed fishes (A. anableps) some females produced offspring demonstrating birth-defects. At external inspection, the ventral midline was open over variable lengths. In some cases, it was combined with lordosis, kyphosis, or scoliosis. Affected specimens also suffered from cataracts. Histopathology revealed widely scattered degeneration of myofibers. Sheath cells of the notochord had proliferated, resulting in asymmetric shape distortion of vertebrae and indentations in the spinal cord. The spinal cord revealed an extensive axonal degeneration. The liver appeared mottled due to focal fat infiltration. Cataracts of ocular lenses appeared as vacuolization of lens fibers. The multiple pathologies noted may have been due to nutritional imbalances because the colony received a carnivore-based diet. Feeding ecology of Anableps is one of omnivory with a predominance of herbivory. This may have resulted in lesions comparable to deficiencies in Vitamin E, Vitamin C, and Selenium.

Juvenile salmonid abundance in a diamictic semi‐fluvial stream in Norway—does stream bed shelter beat large woody debris?

AbstractThis study investigates the effect of large woody debris (LWD) on the abundance of juvenile Atlantic salmon (Salmo salar, L.) and anadromous brown trout (Salmo trutta, L.) in semi‐alluvial side channels of the river Aurlandselva (Norway) using point electrofishing and microhabitat mapping. Not the presence of LWD, but stream bed shelter availability and the distance to spawning grounds affected the fish abundance (fish/point), independent of other habitat components. LWD showed only an effect on fish abundance when in interaction with other habitat components. This discrepancy can be explained by the availability of cavities in the shelter‐rich coarse substrate which provide sufficient cover and territory for juvenile fish at the given carrying capacity of river Aurlandselva. Whilst LWD may be most effective to provide shelter in lowland streams (bed slope &lt;0.005), maintaining or restoring shelter‐rich coarse substrates should be considered a key priority in steeper salmonid rivers and associated semi‐fluvial streams.

The Efficacy of Floating Electrode-Dielectric Barrier Discharge Plasma against Staphylococcus aureus and Salmonella Typhimurium on Fried Fish Paste

In this study, we evaluated the antibacterial effect of floating electrode–dielectric barrier discharge (FE-DBD) plasma (1.1 kV, 43 kHz, N2 1.5 m/s, 1–60 min) against Staphylococcus aureus and Salmonella Typhimurium in fried fish paste. In addition, a quality evaluation (pH, VBN) of fried fish paste was conducted after the FE-DBD plasma treatment. When FE-DBD plasma was used for treatment for 1, 5, 10, 20, 30, and 60 min, S. aureus decreased by 0.16–1.13 log10 CFU/g, and S. Typhimurium decreased by 0.25–1.13 log10 CFU/g. Both decreased &gt; log10 CFU/g at 60 min. The D-value was 58.92, and R2 was 0.97 for S. aureus using first-order kinetics, and the D-value was 43.60, and R2 was 0.97 for S. Typhimurium using the Weibull model. There was no significant difference in pH after the FE-DBD plasma treatment (p &gt; 0.05). Additionally, volatile basic nitrogen (VBN) significantly decreased as the treatment time increased (p &lt; 0.05), and it was the lowest 3.46 at 60 min. Therefore, this FE-DBD plasma treatment could be considered a technology for preserving the quality of processed foods.

Sterol Migration during Rotational Frying of Food Products in Modified Rapeseed and Soybean Oils.

This study explores the impact of rotational frying of three different food products on degradation of sterols, as well as their migration between frying oils and food. The research addresses a gap in the existing literature, which primarily focuses on changes in fat during the frying of single food items, providing limited information on the interaction of sterols from the frying medium with those from the food product. The frying was conducted at 185 ± 5 °C for up to 10 days where French fries, battered chicken, and fish sticks were fried in succession. The sterol content was determined by Gas Chromatography. This research is the first to highlight the influence of the type of oil on sterol degradation in both oils and food. Notably, sterols were found to be most stable when food products were fried in high-oleic low-linolenic rapeseed oil (HOLLRO). High-oleic soybean oil (HOSO) exhibited higher sterol degradation than high-oleic rapeseed oil (HORO). It was proven that cholesterol from fried chicken and fish sticks did not transfer to the fried oils or French fries. Despite initially having the highest sterol content in fish, the lowest sterol amount was recorded in fried fish, suggesting rapid degradation, possibly due to prefrying in oil with a high sterol content, regardless of the medium used.

Behavioral and neurophysiological effects of buspirone in healthy and depression-like state juvenile salmon.

A proportion of farmed salmon in seawater show a behaviorally inhibited, growth stunted profile known as a depression-like state (DLS). These DLS fish are characterized by chronically elevated serotonergic signaling and blood plasma cortisol levels and the inability to react further to acute stress, which is suggestive of chronic stress. In this study, we characterize the neuroendocrine profile of growth stunted freshwater parr and confirm that they show a DLS-like neuroendocrine profile with a blunted cortisol response and no serotonergic increase in response to acute stress. Furthermore, we attempted to reverse this DLS-like profile through pharmacological manipulation of the serotonin (5-HT) system with buspirone, an anxiolytic medication that acts as a serotonin receptor agonist (i.e., decreases serotonergic signaling). We found that while buspirone decreases anxiolytic-type behavior in healthy fish, no quantifiable behavioral change was found in DLS-like fish. However, there was a physiological effect of diminished basal serotonergic signaling. This suggests that at the physiological level, buspirone appears to reverse the neuroendocrine DLS profile. With a deeper understanding of what causes DLS profiles and growth stunting in juvenile fish, steps can be taken in terms of husbandry to prevent repeated stressors and the formation of the DLS profile, potentially reducing losses in aquaculture due to chronic stress.

Assessing organophosphate insecticide retention in muscle tissues of juvenile common carp fish under acute toxicity tests

Organophosphate insecticide spray poses potential threat of contamination of environmental components their accumulation in aquatic organisms. Although various physiological deficits associated with their exposure in fishes are documented, yet their retention in their edible muscle tissues has been poorly studied. In this context, the study was undertaken to ascertain the bioaccumulation of two organophosphate insecticide compounds (dimethoate and chlorpyrifos) in the muscles of juvenile Cyprinus carpio. The study could provide insight into the risks to human health associated with consuming contaminated fish flesh. The fishes exposed to various concentrations of dimethoate and chlorpyrifos in-vivo for 96 to ascertain the uptake and retention of these insecticides in the muscle. Results indicated that fish muscles accumulated the residues at all the concentrations with the recovery of 2.99% (0.032 ppm) of dimethoate exposed to LC50 concentrations. In contrast, the chlorpyrifos residues were found Below the Detection Level (BDL) in the fishes exposed to LC50 concentrations. The percentage bioaccumulation of dimethoate in fish muscle was 88.10%, and that of chlorpyrifos was BDL. The bio-concentration factor was dose-dependent and increased with increasing doses of both insecticides. The study invites attention to human health risk assessment in the regions where contaminated fish are consumed without scientific supervision.