Juvenile Fish Research Articles

Nutrient Composition of Nine Festival Dishes Obtained from A Recipe Survey Among Lower to Middle-Income Households in Selected Urban Areas

Background and Objectives: Estimation of nutrient content of a recipe by a recipe calculation method may be cost‐effective and alternative to the chemical analysis for a range of applications, laboratory analysis of standardized recipes is considered a more authentic and accurate source of recipe nutrient data. Food composition data (FCD) regarding festival foods and dishes is very scanty in local and global food composition tables (FCT). The present study, thus, conducted a recipe survey on the ingredient profile of festival recipes consumed by lower to middle-income households in Bangladesh followed by proximate analysis of standard recipes obtained by collapsing similar recipes. Unanalyzed nutrients were obtained by data compilation from local and global food composition databanks (FCDB). Methodology: A cross-sectional recipe survey was conducted sequentially on festival foods and dishes among purposefully selected housewives residing at different areas of Dinajpur district and Dhaka city. The study instrument was a structured pre-tested questionnaire. Nine homemade festival recipes out of 40 recipes cited viz., plain polao, beef bhuna, fish fry, chicken bhuna, payesh, beef biriyani, chinese vegetable, chicken roast and baked fish were selected and standardized according to the method established in our laboratory. The selected recipes were prepared and analyzed for proximate composition along with an estimation of the cooking yield factor. Content of moisture, ash, protein, total fat, total dietary fiber (TDF), available carbohydrates, and calorie values of nine selected dishes were determined using standard operating procedures (SOP) established on the basis of AOAC methods. Precision and accuracy of analytical values were checked as part of Quality Assurance Program (QAP). Data compilation of missing values for vitamins and minerals was conducted according to FAO data compilation toolkit. Result: Moisture content ranges from 30.42-70.75%, protein content ranges from 2.60-35.70%, fat content ranges from 2.61-22.53%, ash content ranges from 0.6241-8.8%, TDF ranges from 0.58-8.49%, carbohydrates ranges from 0.65-45.7% and energy content ranges 101.5-368.4 kcal/100g fresh sample. The cooking yield ranges from 40.96-96.82%, which is highest in plain polao and lowest in fish fry. Conclusion: The data generated from this study can be used as reliable data which will enrich the national food composition table. Bioresearch Commu. 10(2): 1516-1523, 2024 (July)

REALISM AND COMPOSITIONAL REPRESENTATION OF REALITY : AN ANALYSIS OF THE MANIPURI DOCUMENTARY FILM “FRIED FISH CHICKEN SOUP AND A PREMIERE SHOW”

The debate around realism in documentary cinema has evolved significantly over the years reflecting broader shift in filmmaking techniques, compositional forms, audience expectation, cultural and political contexts. The realms of realism and compositional documentary have been in a constant state of flux, each genre pushing the boundaries of what is considered truth, authenticity, and artistic expression thereby blurring the lines between reality and fiction, and challenging the traditional notions of documentary filmmaking. Several Manipuri documentary films have made endeavors of recreating the reality through their representation on cinematic canvas. Depicting Manipur’s cinematic journey and its socio-political context in a compositional form, the documentary film “Fried Fish, Chicken Soup, and a Premier Show” (2012) relies heavily on editing with found footage and presents an even greater challenge with the inclusion of historical narratives. It intricately combines observational account of a film crew at work during the filming of the Manaobi MM’s Manipuri feature film “21st Century Gee Kunti” (2010) with intertitles, archival footage etc. to depict the history of Manipur. This paper explores the realism and compositional representation of reality in the film which skillfully blends diverse elements to document the trend of change and transformation within the cinematic landscape and the lived reality of Manipuri society in transition.

AFLATOXIN CONTAMINATION AND NUTRITIONAL EVALUATION OF DRIED JUVENILE FISH (Clarias gariepinus) SOLD IN IBADAN METROPOLITAN MARKETS

The contamination of food due to the occurrence of mycotoxigenic fungi is a public health concern. Therefore, fungi and aflatoxin contamination of smoked-dried juvenile fish (SDJF) (Clarias gariepinus) were investigated. The samples were purchased from three major markets in Ibadan. The total fungal count ranged from 1.0 x 103 to 12.0 x 103 CFU/g. Thirty-two fungi were isolated, including Penicillium sp., Rhizopus sp., Alternaria sp., Aspergillus flavus, Aspergillus niger, and Aspergillus ochraceus. A. niger had the highest frequency of occurrence (38%), while A. ochraceus (3%) had the lowest. All the samples were contaminated with aflatoxin. The total aflatoxin content ranged from 0.237 to 1.995 ppb. Of the 11 Aspergillus strains obtained from the samples, 5 were aflatoxigenic, while 6 were not. 85 and 94% of the mycobiota were xerophilic and halophilic. The percentage moisture content, crude protein, crude fat, and ash content in the samples ranged from 12.99–17.82%, 68.72–77.62%, 0.49–6.00%, and 6.97–12.24%. Phosphorus and potassium concentrations of the SDJF samples ranged from 388.2–509.6 mg/100g and 1113.8–1517.0 mg/100g, while lead and cadmium were not detected in the samples. Though the level of aflatoxin contamination in this study was within the maximum limit permitted (20 ppb), proper attention is needed for adequate preservation before sales and consumption.

A Case Study on Economic Analysis of Sea Cage Farms in the Black Sea, Türkiye

The main aim of this research is to understand the value chains of enterprises engaged in aquaculture in sea cages in the Black Sea region of Türkiye, to determine production costs and to make a general analysis of the aquaculture sector. Random sampling method was used to ensure that farmers were equally represented in the survey. Data for the survey were randomly selected from 16 separate farms spread throughout 4 different marine cage locations. Furthermore, fish traders and sector stakeholders were interviewed. The businesses examined within the scope of the study are divided into 3 groups: small (250 -500 tons/year), medium (501-999 tons/year) and large (>1000 tons/year), according to their capacities. The most important expense items of enterprises consist of variable costs. Among the variable costs, the purchase of fry fish, feed purchase, and labor costs constitute the most important expenditure items. Among the fixed costs, the most important expense is depreciation costs. The unit cost of one kg of fish varies between 2.7 and 3.0 euros. Considering that the trout (Oncorhynchus mykiss) and seabass (Dicentrarchus labrax) in the Black Sea are at the level of 3.5 Euro, the profit rate of the enterprises is between these levels. Recently, since trout from the Black Sea has been exported to the Far East Country (particularly Japan), its price has also increased. In 2018, the average retail price (including VAT) and medium selling price of seabass and trout were at a level of 5.24 and 5.34 Euros respectively. Despite all these positive developments, climate change continues to pose a threat in terms of disease outbreak and marketing problems.

Mangrove ecosystems as fundamental habitats for fish from the Mexican Caribbean: An evaluation between a conserved and restoration zone

Mangrove ecosystems can function as a habitat for many juvenile marine fish species, with provisions of food and refuge. Seemingly, these ecosystems have been extensively reduced due to anthropogenic activity, as is widespread land use and road construction along the coastline. Nonetheless, much needed restoration efforts have increased tremendously over time. This study analyzes fish community, and the manner in which habitats in the mangrove ecosystem are used, comparing two mangrove zones, a conserved zone (healthier state) and one undergoing restoration. Hydrologically, no significant differences were registered (KW p>0.05). Of the 24 species registered, marine species were dominant in the conserved zone and estuarine species dominant in the restoration zone. Juvenile fishes were more abundant in the conserved mangrove zone, with a higher proportion of adults found in the restoration zone. According to Hutcheson’s t test, fish diversity showed significant statistical differences between sites combined with distinct climatic seasons. The Canonical Correspondence Analysis (CCA) indicated a relationship between secondary freshwater species Floridichthys polyommus and Cyprinodon artifrons and greater salinity and temperature, whereas marine species had a higher relationship with well oxygenated sites. A high number of marine fish species in juvenile stage in the conserved area may relate to mangroves functioning as nurseries. This can serve as a useful indicator by managers taking an integral approach to evaluate and monitor present and future mangrove restoration programs and pathways.

Community structure of whole pelagic copepods along the Kuroshio: Increase in the abundance and size in the north frontal area of the Kuroshio axis near the Japanese archipelago

The Kuroshio ecosystem is an important nursery ground for various fish species. Because the prey biomass and composition influence the recruitment of larval and juvenile fish, we investigated the variation in the abundance, carbon biomass, and community structure of copepods, which are the main prey for larval and juvenile fish, along the Kuroshio from the eastern coast of Taiwan to the Boso Peninsula, Japan from 8–November 24, 2015, using 100 μm-meshed plankton net samples. We identified two groups of stations (A and B) by the cluster analysis based on the composition and abundance for adult copepods (Q-mode). The total copepod abundance and carbon biomass were higher in Group A than in Group B. Of the dominant species assemblages classified by cluster analysis (R-mode), the abundance of species assemblages S2b and S3, which were composed of small-sized species (e.g., Oithona and Oncaea species), did not differ between Groups A and B, indicating that they were distributed abundantly throughout the Kuroshio region. On the other hand, the species assemblages (S1 and S2a) including the medium-sized calanoid copepods of coastal species and subtropical species (e.g., Paracalanus aculeatus and Clausocalanus furcatus) contributed to the high abundance and biomass of Group A. Group A occurred in the north-frontal area of the Kuroshio axis near the Japanese archipelago where chlorophyll a was high. This indicates that the community was changed by the bottom-up processes driven by nutrient supply from the subsurface layer in the north-frontal area. These results show that although the small-sized copepods were usually dominant in numerical abundance in the Kuroshio region as well as other oligotrophic oceans, the medium-sized copepods were an important component in the copepod community in water with high primary production. We concluded that the ecosystem in the north-frontal area downstream of the Kuroshio might provide optimal prey environments for diverse fish larvae and juveniles.

Transcriptome-Based Analysis of the Mechanism of Action of Metabolic Disorders Induced by Waterborne Copper Stress in Coilia nasus.

To reveal the effects of waterborne copper stress on gene expression changes, molecular pathways, and physiological functions in Coilia nasus, juvenile fish were equally divided into two experimental groups, and the copper levels were 1.61 ± 0.03 mg/L (copper-exposed group) and 0 mg/L (control group), respectively. After 4 h, gill tissue samples were collected for transcript sequencing analysis, and two libraries were constructed from the copper treatment group (Cu) and the control group (C) and sequenced using Illumina sequencing technology. The results showed that approximately 40.2-46.0 M clean reads were obtained from each library, and the percentage of uniquely mapped transcripts ranged from 80.57 to 84.93%. A total of 3915 differentially expressed genes (DEGs) were identified under waterborne copper stress, among which 1300 genes were up-regulated, and 2615 genes were down-regulated. Twelve DEGs were randomly selected for quantitative RT-PCR (qRT-PCR) analysis, and the results confirmed that the transcriptome analysis was reliable. Furthermore, the DEGs were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and the results showed that most of the DEGs were involved in metabolic pathways, including steroid biosynthesis, glutathione metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Furthermore, due to the waterborne copper levels, gsk-3β was significantly up-regulated, while other metabolism-related genes (tor, pi3k, lpl, aqp7, fabp3) were significantly down-regulated. In addition, the copper-exposed group significantly reduced the expression of some immunity genes (ifn-γ, stat1, cxcl10, and tgf-β), and enhanced the expression of il-1β and tnf-α. In summary, these results indicated that copper causes metabolic disorders and insufficient energy supply in the body, and induces oxidative stress, which results in reduced immune functions.

When to Go Against the Flow: Examining Patterns of Performance Over Multiday Migration Events in the Hawaiian Stream Fish, 'O'opu Nōpili (Sicyopterus stimpsoni).

Many animals migrate across regions of their geographic range as part of extended events, with groups of individuals proceeding through areas of travel on several successive days. Early migrating individuals may have an advantage over late migrating individuals by gaining early access to the resources at the eventual destination. For situations where early access to resources would provide an advantage, specific sets of locomotor traits might be found among individuals that are earlier migrators. We tested for associations between migration timing and traits related to escape responses, climbing, and morphology in the amphidromous Hawaiian stream goby, 'o'opu nōpili (Sicyopterus stimpsoni). In this species, juvenile fish migrate in pulses over several days immediately following flash floods. We collected daily measurements of escape responses and waterfall climbing from juvenile fish arriving at streams from the ocean. We found that escape performance showed mainly stochastic variation across migrating individuals tested on successive days. In contrast, some metrics of climbing performance decrease over successive pulses during a migration event. We also found more variation in body shape among fish from early pulses during migration events compared to later in pulses. These results could have implications for guiding conservation efforts, identifying critical time windows for protection as periods with the greatest likelihood of successful migrants.

Physiological sensitivities to hypoxia differ between co-occurring juvenile flatfishes

Coastal hypoxia threatens estuarine nursery habitat for juvenile demersal fishes worldwide, and is expected to intensify with climate change. This study examines the physiological tolerances of hypoxia in two ecologically and economically important flatfish species that co-occur in a highly eutrophic estuary and biodiversity hotspot on California's central coast, the Elkhorn Slough. Juveniles of English sole (Parophrys vetulus) occur less frequently in areas of the slough where dissolved oxygen (DO) ≤ 4.0 mg/L O2 compared to speckled sanddabs (Citharichthys stigmaeus), suggesting that English sole may be more sensitive to hypoxia. We exposed both species to an ecologically relevant, acute six-hour exposure to six DO levels ranging from ambient to severely hypoxic: 8.0, 6.0, 4.0, 3.0, 2.0, and 1.5 mg/L O2 and measured known physiological and biochemical indicators of hypoxia stress. As DO declined, metabolic rate and aerobic scope decreased for English sole, while anaerobic activity (measured by L-lactate) and ventilation rate increased for both species. Biochemical responses to hypoxia were observed only at very low DO levels (≤ 4.0 mg/L O2), indicating that both species appear to have a higher tolerance for relatively short-term hypoxia than other teleost fishes. Speckled sanddabs increased ventilation rate and anaerobic activity at higher DO levels than English sole, suggesting that earlier onset of compensatory mechanisms may contribute to the greater relative hypoxia tolerance in sanddabs. Examining the link between physiological and ecological thresholds for hypoxia tolerance will help determine suitable nursery habitat areas and management targets for estuarine restoration, and aid in predictions of fishery success under eutrophication and climate change.

Integrating Iso-seq and RNA-seq data for the reannotation of the greater amberjack genome

The greater amberjack is a very important fishery species with high commercial value, and it is distributed worldwide. Transcriptome-based studies on S. dumerili have been limited by an inadequate reference genome and a lack of well-annotated full-length transcripts. In this study, a total of 12 tissues from juvenile and adult fish both sexes were collected for next-generation RNA sequencing (RNA-seq) and full-length isoform sequencing (Iso-seq). For Iso-seq, a total of 163,218, 149,716, and 189,169 high-quality unique transcript sequences were obtained, with an N50 of 5,441, 5,255, and 5,939, from juvenile, adult male and adult female S. dumerili, respectively. We integrated the Iso-seq and RNA-seq data to construct a comprehensive gene annotation and systematically profiled the dynamics of gene expression across the 12 tissues. Our gene models had greater detail and accuracy than those from NCBI and Ensembl, with more precise polyA locations. These resources serve as a foundation for functional genomic studies and provide valuable insights into the molecular mechanisms underlying the development, reproduction and commercial traits of amberjack.

Seasonal dynamics and habitat preferences of juvenile fish assemblages in the Wanquan Estuary, South China: Implications for conservation and management

Tropical estuaries encompass diverse habitats, which are crucial for supporting juvenile fish by providing nurseries, refuges, and migration routes. In the present study, we investigated the seasonal and spatial dynamics of juvenile fish assemblages in the Wanquan Estuary, Hainan Island, China, examining variations during the wet and dry seasons across four types of habitats. Our research aimed to test the hypotheses: (1) the wet season supports a greater abundance and species richness of juvenile fish compared to the dry season, and (2) juvenile fish showed varying habitat preferences across seasons. We recorded a total of 3617 individuals belonging to 33 families, 50 genera, and 78 taxa. Our findings revealed significant seasonal fluctuations in the assemblage structure, with peak abundance during the wet season in August, primarily consisting of diadromous species. A notable shift towards marine species was observed in March. Spatially, juvenile fish exhibited significant habitat preferences, with a strong preference for sand substrates for most species. Contrary to common expectations, mangrove fringe habitats were not identified as the primary nursery grounds for juvenile fish. Instead, our study highlights the importance of habitat diversity and connectivity in enhancing nursery functions. Water temperature and salinity were the key drivers influencing the seasonal and temporal patterns of juvenile fish assemblages in the Wanquan River estuary The pronounced temporal dynamics of these assemblages, driven by seasonal environmental alterations affecting water variations and habitat connectivity, were more significant than spatial differences. The findings emphasize the need for focused connectivity of various habitats to support the conservation of diverse fish communities in tropical estuarine ecosystems.

Capture–translocation restores spawning migration connectivity of Razorback Suckers in the fragmented San Juan River

AbstractObjectiveBarriers to movement negatively affect population vital rates of riverine fishes that rely on connected migratory routes to complete components of their life cycle, such as reproduction and recruitment. In the southwestern United States, decades of water diversion, construction of large impoundments, and loss of floodplain habitats have all contributed to highly fragmented riverscapes. A capture–translocation strategy was implemented for Razorback Suckers Xyrauchen texanus in the San Juan River to mitigate the negative effects of two barriers while precluding the upstream movement of nonnative species. We hypothesized that translocated individuals would remain upstream of barriers during the spawning season and that aggregations of translocated Razorback Suckers would be identified upstream in spawning habitats.MethodsWe used radiotelemetry to assess movement of Razorback Suckers after translocation above the two barriers. We deployed fixed remote radio receivers to determine residency time above each barrier and conducted mobile telemetry surveys to monitor upstream destinations after translocation.ResultAlthough most Razorback Suckers returned downstream of barriers within 2 months of translocation, we provide evidence that most individuals remained upstream long enough to successfully spawn. After translocation above the Piute Farms Waterfall, 80% of individuals remained upstream for 26 days in 2020 and for 23 days in 2021. Further upstream (307 km), at a weir operated by the Public Service Company of New Mexico, 80% of translocated individuals remained above the barrier for 37 days in 2021 and for 25 days in 2022. After fish translocation above both barriers, we observed upstream movements ranging from 2 to 262 km and we detected distinct aggregations within the expected spawning season.ConclusionAlthough translocation efforts seasonally reconnect migratory routes for a proportion of the population and may increase spawning potential, other conservation actions are likely still needed to improve recruitment conditions for juvenile fish.

Shallow estuarine reef as nursery habitat for Australasian snapper (Chrysophrys auratus)

ABSTRACT Estuaries are important recruitment sites for many fish species, with structurally-complex habitats such as subtidal seagrass beds on soft sediments particularly valuable due to their provision of food and shelter. Soft sediments dominate most estuaries, but where hard-bottom reefs are present they have the potential to act as nursery habitats for juvenile fish. We document recruitment of juvenile Australasian snapper (Chrysophrys auratus) to a shallow linear sandstone reef in Whangateau Harbour, a small estuary in north-eastern New Zealand. Up to several hundred 0 + juveniles (∼20–70 mm fork length) were present on the reef during early summer to mid-late autumn each year from 2018 to 2021. Numbers were consistently highest at the seaward end of the reef, facing into incoming tidal currents, and lowest in the deeper central part of the reef, where larger, potentially cannibalistic, snapper were common. Juveniles disappeared from the reef fairly abruptly at the end of each season, with departure in at least two of the years appearing to follow a sudden decrease in water temperature rather than being associated with body size or absolute temperature. Although relatively small in area, estuarine reefs may be increasingly important nursery habitats in the future given the widespread loss of subtidal seagrass beds.

Unravelling spermatogenesis in spotted wolffish: Insights from the ultrastructure of juvenile male testes to the cryopreservation of broodstock sperm

The aim of this study was to deepen our understanding of the reproductive biology of male spotted wolffish (Anarhichas minor) using two different experimental approaches involving juvenile and mature broodstock fish. The first approach consisted of a detailed histological examination of the testes to identify the onset of gonadal maturation and characterise the spermatogenic stages in two- and three-year-old juvenile specimens. Light microscopy analysis revealed clear differences between the age groups. Two-year-old fish displayed well-defined interstitial tissue, Sertoli cells and cysts housing spermatogonia stem cells in which meiosis had not yet begun. In contrast, three-year-old fish exhibited cysts containing spermatocytes, spermatids and abundant spermatozoa, indicating the initiation of the spermatogenic cycle, albeit with asynchronous puberty. Histochemical staining revealed a significant presence of smooth myoid cells in the interstitial tissue of sexually mature fish, while electron microscopy further revealed synaptonemal complexes indicating the onset of meiosis and centriolar structures that gave rise to flagella. The second approach focused on optimising semen freezing and cryopreservation procedures in mature broodstock individuals over the age of 10 years. Seven freezing extenders (KT, TS-2, OP, MT, MH, HBSS, or SR), with seawater (SW) as a control, were assessed along with two cryoprotectants dimethylsulfoxide (DMSO) or methanol to evaluate their impact on pre- and post-thaw semen quality. Results showed that the MT and HBSS extenders were superior in total sperm kinetics at 1:3 dilution, and that DMSO showed optimal results in sperm motility and velocity variants. Moreover, the MT and HBSS groups demonstrated consistent sperm viability after cryopreservation, with values similar to fresh samples. Based on the viability results of the SYBR-green-14/PI assay comparing fresh and cryopreserved sperm using MT and HBSS, the MT extender emerged as the most effective freezing medium for cryopreservation of spotted wolffish broodstock sperm. In conclusion, this study provides a comprehensive understanding of the reproductive dynamics of male spotted wolffish, offering valuable insights for both scientific research and aquaculture management.

Dietary inclusion of insect oil: Impact on growth, nutrient utilisation, lipid metabolism, antioxidant and immune-related responses in European catfish (Silurus glanis L)

In this study, we investigated the black soldier fly (Hermetia illucens) larvae oil (IO) as replacement of fish oil and vegetable oil in the diets of European catfish. The formulated diets included a control diet (CTR) containing fish oil (FO) and rapeseed oil (RO), and two experimental diets replacing FO and RO, with 50% and 100% IO, respectively. The nutritional trial comprising 630 European catfish juveniles (average initial body weight: 28.1 ± 0.17 g) randomly distributed into triplicated dietary groups (CTR, IO50, and IO100) was conducted for 8 weeks in a recirculation aquaculture system. The study was focused to evaluate the impact of IO on fish growth and nutrient utilisation, lipid metabolism, antioxidant, and immune-related responses in juvenile fish. Results obtained indicated that all the diets promoted adequate fish growth and feed utilisation, with no significant differences in these parameters between the dietary fish groups. It appears that the diets did not impact the activity of digestive enzymes, but a decrease in the apparent digestibility coefficients was observed. Significant differences were observed in tissue fatty acid (FA) composition. The significantly higher levels of whole-body total saturated fatty acids and arachidonic acid in fish fed IO-based diets relative to those fed CTR diet were accompanied by significantly lower levels of whole-body monounsaturated fatty acids and n-3 polyunsaturated fatty acids (n-3 PUFA). However, some deviations in this trend were observed in the liver highlighting the sparing effect for long chain polyunsaturated fatty acids (LC-PUFAs). Gene expression analysis showed a significant upregulation of genes encoding lipoprotein lipase (lpl), carnitine palmitoyl transferase (cpt1a), and hepatocyte nuclear factor 4 alpha (hnf4α) in the livers of fish fed the IO100 diet. Among the five immune-related genes examined in the spleen, only interferon regulatory factor 1 was significantly upregulated in fish fed IO50 relative to the CTR. These results indicated upregulated metabolic activities in fish fed the IO100 diet probably due to a higher level of dietary medium chain saturated fatty acids (MCSFA) and a lower level of LC-PUFA, creating the need for fish to oxidise more MCSFA and to deposit more LC-PUFA in the tissues in order to maintain fatty acid balance.

Zinc nutrition at first feeding imprints a programming effect on growth and hepatic lipid metabolism in juvenile rainbow trout

The objective of this study was to determine whether supplementation with deficient zinc (Zn) or/and excess copper (Cu) in the first-feeding diet of rainbow trout fry influenced the growth and physiological regulation of juvenile fish subjected to similar challenge feeds again. The feeding trial lasted for 24 weeks and had three phases. In phase I, rainbow trout fry was treated with one of four different plant-based feeds containing or exempting Zn or Cu supplementation (coded Zn-Cu-, Zn+Cu-, Zn-Cu+, Zn+Cu+) for 6 weeks. Thereafter, all groups were fed a common commercial feed for the next 12 weeks (phase II). In phase III, all groups were fed with the “challenge diet” for another 6 weeks which was the basal diet (Zn-Cu-) except that the vegetable oils were replaced by fish oil. The results demonstrated that fish fed a Zn+ diet at first feeding increased larval growth (phase-I), but it had no effect on growth at the end of phase II when fed commercial feeds. In phase III, when re-introduced to a Zn- challenge diet, the feed intake and growth of juveniles with Zn+ history significantly increased, with reduced feed efficiency. Fish growth was neither influenced by dietary Cu levels or by the dietary Cu history in any of the growth phases, but dietary Cu excess (Cu+) reduced body lipid and energy content in fry. In phase I, lower whole-body Zn concentration was observed in the fry of Zn- group compared to Zn+, while the contrary was observed in the juvenile fish as affected by dietary Zn history (phase III). In addition, Zn- dietary history showed increased levels of PUFA and higher mRNA expression of fatty acid biosynthesis genes in the liver. To conclude, early-stage dietary Zn+ history improved growth of juvenile rainbow trout, while dietary Zn- history exhibited signs of improved fatty acid biosynthesis capacity in the liver.

Integration of socio-ecological data to prioritize biodiversity hot-spots for Marine Protected Area (MPA) delineation in the coastal zone of Bangladesh

Marine Protected Areas (MPAs) are widely used tools for conserving coastal and marine biodiversity and ecosystem health. However, the goal of declaring and managing at least 10 % of coastal and marine waters as MPAs has not been achieved in Bangladesh and many other countries. This study aimed at prioritizing the potential areas for MPA delineation in the south-west coastal zone of Bangladesh. The study also examined the socio-economic status, environmental and ecological characteristics of the study areas. Data on socio-economic, environmental, ecological, and management variables were collected through intensive field surveys from August 2023 to December 2023. The data were integrated using a multi-criteria analytical technique. Fishing was identified as the primary occupation for all fishermen surveyed, with secondary occupations including fish selling, marketing, and drying activities. The fishing areas for fishermen from the three survey sites were mainly concentrated in the offshore area. All three areas were identified as biodiversity hotspots, with Kuakata coast showing the highest species diversity, followed by Salimpur and Sandwip coasts. The study revealed that the Kuakata coast has the highest conservation importance, especially for IUCN red-listed species, juvenile fisheries species, and megafauna species. Salimpur coast is important for the conservation of saltmarshes, mangroves, and their dependent communities, while Sandwip is crucial for juvenile fish species conservation. Based on socio-ecological criteria, Kuakata was recommended as the most potential site for MPA delineation, followed by Salimpur and Sandwip. Implementing these recommendations can improve the management and execution of existing MPAs by focusing conservation efforts on areas with the highest biodiversity and ecological importance, ensuring better protection for vulnerable species, and enhancing the sustainability of local fishing communities. This, in turn, will ultimately enhance biodiversity conservation and ecosystem health in the southwest coastal area of Bangladesh.

Dynamic impacts of short-term bath administration of enrofloxacin on juvenile black seabream Acanthopagrus schlegelii

Dynamic impacts of short-term enrofloxacin (ENR) exposure on juvenile marine fish are not well understood, and the underlying mechanisms remain unclear. We therefore investigated the accumulation and elimination of ENR in the liver of juvenile black seabream Acanthopagrus schlegelii. Meanwhile, the dynamic alterations of biochemical parameters and liver transcriptomes after short-term bath immersion and withdrawal treatment were explored. The results indicated that the contents of ENR in the liver were significantly increased after bath administration for 24 h, and then quickly declined to very low concentrations along with the decontamination time increasing. Judging from the changes in biochemical indicators and liver transcriptomic alterations, 0.5 and 1 mg/L ENR exposure for 24 h triggered oxidative stress, impairment of immune system, as well as aberrant lipid metabolism via differential molecular pathways. Interestingly, biochemical and transcriptome analysis as well as integrated biomarker response (IBR) values showed that more significant changes appeared in 1 mg/L ENR group at decontamination periods, which indicated that the impact of high dose ENR on juvenile A. schlegelii may persist even after depuration for 7 days. These results revealed that the risk of short-term bath of 1 mg/L ENR should not be overlooked even after depuration period. Therefore, attention should be paid to the dosage control when administering the drug to juvenile A. schlegelii, and the restoration of physiological disturbance may be an important factor in formulating a reasonable treatment plan.

Empirical verification of feeding selectivity of larval and juvenile pelagic fishes using in-situ zooplankton assemblages

Most studies on the feeding ecology of larvae and juveniles of commercially important pelagic fishes have used field-based approaches. However, due to possible biases related to net sampling, it is uncertain whether the results obtained from those studies truly represent the situation of live fish in the sea. Here we investigated the feeding ecology of pelagic fishes through a laboratory experiment minimizing the biases inherent in field net sampling. In the experiment, hatchery-reared juvenile chub mackerel (Scomber japonicus) and larval/juvenile Japanese anchovy (Engraulis japonicus) were fed with wild-caught zooplankton assemblages collected from around Hakatajima Island in the Seto Inland Sea, Japan. The relationships between fish size and prey number in the gut, and the selectivity on each prey organism were determined. As a result, in both species, prey number and size increased with body size, and the fish showed strong selectivity for crustaceans including copepodites and adults of copepods. Our data has also clearly indicated that both species can selectively prey on preferred foods that are rare while avoiding non-preferred foods that are abundant. These results, which substantially accord with reports from previous field studies, will not only help field scientists make a convincing interpretation of their data, but also open the possibility of further laboratory studies on detailed mechanisms of the feeding selectivity of larval/juvenile pelagic fishes.

Effects of Β-sitosterol oleogel on fat uptake reduction, physicochemical properties, oxidative stability, and sensory characteristics of fried surimi fish balls

Surimi, a minced fish meat, is available in various forms, including deep-fried surimi. However, deep-fried surimi tends to absorb high amounts of oil during frying, potentially contributing to obesity and cardiovascular diseases. Additionally, its high fat content renders it susceptible to lipid oxidation during storage, which can degrade its quality over time. Therefore, reducing oil absorption and subsequent oxidation is crucial for enhancing the quality of deep-fried surimi. In this study, we prepared oleogels with varying concentrations of β-sitosterol and investigated their effects on fat uptake, physicochemical attributes, oxidative stability, and sensory properties of frozen (−18 °C) fried surimi fish balls over a period of 30 days. Images that were obtained by scanning electron microscope demonstrated that surimi fish balls with 0.2 % β-sitosterol oleogel had a more compact and smoother crust-core interface than other groups. The addition of 0.2 % β-sitosterol oleogel led to the lowest fat absorption (8.63 %), decreased lipid oxidation (3.65 mg MDA/kg), reduced porosity, higher moisture content (57.72 %), elevated pH and color values, as well as increased bulk density compared to the control (p ≤ 0.05). Although atherogenicity and thrombogenesis indices increased, they remained below recommended levels. Importantly, this treatment did not adversely affect the product's texture and sensory properties. Given the increasing demand for healthier food products, it is recommended that the food industry incorporate 0.2 % β-sitosterol oleogel into the production of low-fat fried surimi. This approach can effectively mitigate lipid oxidation while maintaining product quality and sensory attributes. The study offers a valuable contribution to the food industry by addressing the challenges associated with deep-fried surimi and aligns with the growing consumer preference for healthier food choices.