Fishes

19 pages, 1601 KiB

Open AccessArticle

Potential of Otolith Microchemistry to Distinguish Nursery Areas of Salmon within River Simojoki

by Viktor Finnäs, Erkki Jokikokko, Jan-Olof Lill, Yann Lahaye, Henry Hägerstrand and Kai Lindström

Fishes 2023, 8(6), 332; https://doi.org/10.3390/fishes8060332 - 20 Jun 2023

Viewed by 980

Abstract

Draining into the northern Baltic Sea, River Simojoki is an important spawning river for Atlantic salmon. The present study aimed to preliminary explore the potential of analysing the elemental composition of otoliths to distinguish the within-river nursery area of origin for salmon. Parr [...] Read more.

Draining into the northern Baltic Sea, River Simojoki is an important spawning river for Atlantic salmon. The present study aimed to preliminary explore the potential of analysing the elemental composition of otoliths to distinguish the within-river nursery area of origin for salmon. Parr were sampled at three nursery areas in the river and smolts of unknown origin were sampled near the river mouth during the migration to the sea. The concentrations of multiple elements and the strontium ⁸⁷Sr/⁸⁶Sr isotopic ratio in the otoliths were analysed using single- and multi-collector laser ablation inductively coupled plasma mass spectrometry, respectively. Based on the otolith elemental variables, parr could be reclassified to the sampled nursery areas using discriminant function analysis and random forest with a success rate of 53.3% and 63.3%, respectively. However, for parr sampled at the uppermost nursery area in the river, the success rates were 90% and 100%, respectively. Applying the classification models trained on the parr samples to determine which nursery area sampled smolt originated from was constrained by the limited sampling of parr, both in sample sizes and the coverage of the nursery areas found in the river. Full article

(This article belongs to the Section Biology and Ecology)

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13 pages, 1976 KiB

Open AccessFeature PaperArticle

The Second Record of Gymnesigobius medits Kovačić, Ordines, Ramirez-Amaro & Schliewen, 2019, the Deepest Benthic Gobiiform Species, and the Additional Records of Gobius xoriguer Iglésias, Vukić & Šanda, 2021 (Actinopterygii: Gobiiformes: Gobiidae)

by Marcelo Kovačić, Sergio Ramírez-Amaro, Maria Teresa Farriols and Francesc Ordines

Fishes 2023, 8(6), 331; https://doi.org/10.3390/fishes8060331 - 20 Jun 2023

Cited by 1 | Viewed by 919

Abstract

Gymnesigobius medits is reported for the first time after a recent description recorded from the Balearic Islands and from the slope of the Gulf of Vera on the Iberian Peninsula coast. The record from the Emile Baudot seamount on the Balearic Islands represents [...] Read more.

Gymnesigobius medits is reported for the first time after a recent description recorded from the Balearic Islands and from the slope of the Gulf of Vera on the Iberian Peninsula coast. The record from the Emile Baudot seamount on the Balearic Islands represents the deepest positive benthic gobiiform species record in general. The presence of the membrane connection between the pelvic fins in Gymnesigobius medits, presumed on the damaged fin in the original description, was confirmed. The recently described Gobius xoriguer is the first record from the Pitiusas and Columbretes islands and from the Iberian Peninsula coast. It appears to be widely distributed in the circalittoral bottoms, preferentially in red algae beds. Morphological identification of both species was confirmed using molecular analyses based on the sequencing of the mitochondrial cytochrome c oxidase subunit I (DNA barcode) gene. The deepest records of gobiiform fishes in oceans and seas are reviewed. The European seas, a well-studied area with eight gobiid species recorded deeper than 200 m, show high bathyal gobiid species richness compared to other areas. The real worldwide diversity of bathyal gobies, although only a fraction of the shallow water species richness of this taxon, is probably much larger than presently known. Full article

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16 pages, 1864 KiB

Open AccessFeature PaperArticle

New Organic Raw Materials for Gilthead Seabream (Sparus aurata) Feeding and the Effects on Growth, Nutritive Parameters, Digestibility, and Histology

by Eslam Tefal, Ignacio Jauralde, Ana Tomás-Vidal, Silvia Martínez-Llorens, David S. Peñaranda and Miguel Jover-Cerdá

Fishes 2023, 8(6), 330; https://doi.org/10.3390/fishes8060330 - 20 Jun 2023

Cited by 3 | Viewed by 4779

Abstract

A 120-day experiment investigated the new organic raw materials for Gilthead seabream (Sparus aurata) feeding on growth, nutritional parameters, digestibility, and histology. An organic control diet (CON) and three diets with 100% organic raw materials—the rest of rainbow trout, visceral Iberian [...] Read more.

A 120-day experiment investigated the new organic raw materials for Gilthead seabream (Sparus aurata) feeding on growth, nutritional parameters, digestibility, and histology. An organic control diet (CON) and three diets with 100% organic raw materials—the rest of rainbow trout, visceral Iberian pig, and insects as a protein source (TRO, IBE, and INS)—were tested. After the experiment, growth, nutritional parameters, digestibility, and histology were measured. The CON diet-fed seabream obtained the highest weight; there was no difference between the experimental diets. The crude protein content was the highest in seabream fed the TRO and INS diets. Crude fat was the highest value observed in the CON diet. High digestibility was observed in seabream-fed IBE and INS diets. Except for EAA methionine (Met), there were no static differences in retention efficiency. The diet with the highest hydrolysis rate was IBE. Diet differences were significant but had the typical healthy liver morphology of seabream. Seabream fed on the TRO and INS diets had shorter distal gut measurements. In conclusion, the full substitution of fishmeal with organic raw materials, including rainbow trout remains, Iberian pig viscera, and insects, offers several benefits in terms of digestibility, histology, and growth performance and may help improve sustainable and healthy aquaculture practices. Full article

(This article belongs to the Special Issue Selected Papers from the “XVIII Spanish National Aquaculture Congress Cádiz 2022—Aquaculture: Seas and Rivers of Opportunities”)

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20 pages, 6021 KiB

Open AccessArticle

Effects of Dietary Lentinus edodes Fermentation Supplementation on Digestive Enzyme Activity, Antioxidant Capacity and Morphology of the Liver and Intestine in Largemouth Bass (Micropterus salmoides) Fed High Plant Protein Diets

by Jiaming Xu, Zhoulin Yu, Guangye Liu, Sijie Li, Guoyong Zhou, Hanhua Wang, Yewei Dong, Cuihong You, Weidong Bai, Meng Zhou, Yanhua Huang and Xiaohong Tan

Fishes 2023, 8(6), 329; https://doi.org/10.3390/fishes8060329 - 20 Jun 2023

Cited by 1 | Viewed by 1224

Abstract

This study evaluated the effect of Lentinus edodes fermentation (LEF) on digestive enzyme activity, antioxidant capacity and morphology of the liver and intestine in largemouth bass (Micropterus salmoides) fed high plant protein diets (HPPD). LEF was supplemented in HPPD with 0 [...] Read more.

This study evaluated the effect of Lentinus edodes fermentation (LEF) on digestive enzyme activity, antioxidant capacity and morphology of the liver and intestine in largemouth bass (Micropterus salmoides) fed high plant protein diets (HPPD). LEF was supplemented in HPPD with 0 g kg⁻¹ (LEF0), 10 g kg⁻¹ (LEF1), 20 g kg⁻¹ (LEF2), 30 g kg⁻¹ (LEF3), 40 g kg⁻¹ (LEF4), 50 g kg⁻¹ (LEF5), respectively, and then the six diets were fed to largemouth bass with a body weight of 28.8 ± 0.05 g for eight weeks. Juvenile fish were randomized into 6 groups and each group had 4 replicates with 40 fish. Dietary LEF supplementation alleviated the liver inflammatory reaction of largemouth bass caused by HPPD and improved liver morphology. Goblet cells multiplied and the gut muscle layer thickened after LEF supplementation. The LEF significantly increased amylase activity in the liver and intestine of largemouth bass in individual experimental groups. The LEF could increase the activity of catalase in the liver and intestine of largemouth bass (p < 0.05). The content of malondialdehyde was significantly lower than that in the control group (p < 0.05). Dietary LEF supplementation had no significant effect on the intestinal flora of largemouth bass. These findings imply that LEF supplementation can reduce liver inflammation, enhance intestinal tissue morphology, and eventually benefit largemouth bass health. Full article

(This article belongs to the Special Issue Effect of Dietary Supplementation on the Growth and Immunity of Fish and Shellfish)

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16 pages, 3198 KiB

Open AccessFeature PaperArticle

Spatial Ecology of the Population of Reef Manta Rays, Mobula alfredi (Krefft, 1868), in New Caledonia Using Satellite Telemetry 1–Horizontal Behaviour

by Hugo Lassauce, Olivier Chateau and Laurent Wantiez

Fishes 2023, 8(6), 328; https://doi.org/10.3390/fishes8060328 - 19 Jun 2023

Cited by 1 | Viewed by 2417

Abstract

The reef manta ray, Mobula alfredi (Krefft, 1868), is a highly mobile and plankton-feeding species, classified vulnerable to extinction on the IUCN Red List for Threatened Species. Knowledge on their spatial ecology and the extent of their dispersal remain incomplete, especially within island-fragmented [...] Read more.

The reef manta ray, Mobula alfredi (Krefft, 1868), is a highly mobile and plankton-feeding species, classified vulnerable to extinction on the IUCN Red List for Threatened Species. Knowledge on their spatial ecology and the extent of their dispersal remain incomplete, especially within island-fragmented habitats as found in New Caledonia. Satellite telemetry was used to investigate the horizontal movement ecology of reef manta rays in New Caledonia. A total of 21 reef manta rays were tagged with pop-up satellite archival transmitting tags (21 Fastloc and 2 MiniPAT) that remained deployed for a duration ranging from 3 to 180 days (mean ± SE = 76.7 ± 50.3). Rays presented a strong site fidelity and an important affinity for coastal waters. Long-distance migrations (>300 km) were also observed, mainly through coastal and shallow water paths. Horizontal movements were compared to a home range area and classified into four distinct patterns: Fidelity, Excursion, Fidelity + Relocation and Relocation. The most dominant pattern was Fidelity, where manta rays remained within their home range for the whole duration of the tag deployment. Our findings may assist in the design of more appropriate management strategies for the species in New Caledonia and other regions worldwide. Full article

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14 pages, 1499 KiB

Open AccessArticle

Development of an Accurate Polymerase Chain Reaction (PCR) Assay for Genetic Sex Identification in Lumpfish (Cyclopterus lumpus) Based on Male-Specific Anti-Mullerian Hormone (amh) Gene

by Kasidis Chaiyasut, Paul Merviel, Peter Palma, Johanna Perschthaler, Eduardo Jimenez-Fernandez, Andrew Davie and Alejandro P. Gutierrez

Fishes 2023, 8(6), 327; https://doi.org/10.3390/fishes8060327 - 19 Jun 2023

Cited by 1 | Viewed by 1159

Abstract

The production of lumpfish (Cyclopterus lumpus) has become crucial in controlling sea lice levels in salmonid aquaculture. To improve their breeding, there is a need for early sex identification. The genomic region containing the anti-Müllerian hormone (amh) gene was [...] Read more.

The production of lumpfish (Cyclopterus lumpus) has become crucial in controlling sea lice levels in salmonid aquaculture. To improve their breeding, there is a need for early sex identification. The genomic region containing the anti-Müllerian hormone (amh) gene was suggested as the candidate master sex-determining gene in lumpfish. However, the genome of lumpfish contains three copies of amh with ambiguous sex specificity, designated amh1, amh2, and amh3. The study aims to analyse the male-specific region between these amh paralogues for its application as a sex marker. In this study, we utilised polymerase chain reaction (PCR)-based assays to identify the male-specific amh markers in lumpfish and estimate the length of the male-specific region in the lumpfish genome. Our results indicate that a specific genomic region of approximately 27 kilobases (kb), encompassing amh1 and amh2 genes, exhibits male specificity, whereas amh3 is present in both sexes. The developed PCR-based genetic sex identification assays targeting amh1 and amh2 exhibited over 97% concordance with phenotypic records. Further experiments in other members of the Cyclopteridae: Aptocyclus ventricosus, Eumicrotremus taranetzi, and E. asperrimus revealed male-specific amh genome region only in A. ventricosus. Phylogenetic analyses using the available Cyclopteridae amh sequences suggest that male-specific amh arose early in the Cyclopteridae lineage. Our findings, along with the development of the PCR test, hold great promise for the field of lumpfish aquaculture and will also contribute significantly to future investigations aiming to enhance our understanding of the sex-determination system and the evolution of sex chromosomes in teleostean fish. Full article

(This article belongs to the Section Genetics and Biotechnology)

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12 pages, 881 KiB

Open AccessArticle

The Effects of Grapevine (Vitis vinifera L.) Leaf Extract on Growth Performance, Antioxidant Status, and Immunity of Zebrafish (Danio rerio)

by Seyed Hossein Hoseinifar, Zohreh Fazelan, Ehab El-Haroun, Morteza Yousefi, Metin Yazici, Hien Van Doan and Marina Paolucci

Fishes 2023, 8(6), 326; https://doi.org/10.3390/fishes8060326 - 19 Jun 2023

Cited by 2 | Viewed by 1545

Abstract

An 8-week feeding trial was carried out to evaluate the effects of grapevine (Vitis vinifera) leaf extract (GLE) on the growth, oxidative enzymatic activities, immunity, and expression of antioxidant genes in zebrafish (Danio rerio). Three hundred and sixty zebrafish [...] Read more.

An 8-week feeding trial was carried out to evaluate the effects of grapevine (Vitis vinifera) leaf extract (GLE) on the growth, oxidative enzymatic activities, immunity, and expression of antioxidant genes in zebrafish (Danio rerio). Three hundred and sixty zebrafish were supplied and fed with different levels of GLE: 0, 0.5, 1, and 2 g kg⁻¹. The dietary administration of 1 g kg⁻¹ of GLE significantly increased growth parameters in fish. Fish fed diets with GLE showed increased total protein. The total Ig and lysozyme activity significantly changed in the whole-body serum, but not in skin mucus. GLE significantly increased Catalase (CAT), Superoxide Dismutase (SOD), and Glutathione Peroxidase (GPx) activities compared to the control diet. GLE treatments caused a significant decrease in the malondialdehyde (MDA) content. In the skin mucus, only CAT and SOD activities significantly increased. The highest expression of Toll-like receptor-1 (TLR-1) and Tumor Necrosis Factor-α (TNFα) genes was achieved in fish fed 2 g kg⁻¹ of GLE. CAT and SOD gene expressions were significantly higher in fish fed 1 and 2 g kg⁻¹ of GLE. GPx gene expression was significantly higher in fish fed 1 g kg⁻¹ of GLE. In conclusion, the results of the present study revealed that GLE affects growth performance and regulates antioxidant and immune gene expression. The determination of the optimum dosage merits further research. Full article

(This article belongs to the Special Issue Fish Nutrition and Feed Technology II)

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15 pages, 1677 KiB

Open AccessArticle

Quality Improvement and Shelf-Life Extension of Iced Nile Tilapia Fillets Using Natural Garlic Extract

by Edgar Iván Jiménez-Ruíz, Víctor Manuel Ocaño-Higuera, Santiago Valdez-Hurtado, José Alberto Cruz-Guzmán, Cesar Benjamín Otero-León, Saúl Ruíz-Cruz, Alba Mery Garzón-García, Hebert Jair Barrales-Cureño, Dalila Fernanda Canizales-Rodríguez, Cinthia Jhovanna Pérez-Martínez and María Teresa Sumaya-Martínez

Fishes 2023, 8(6), 325; https://doi.org/10.3390/fishes8060325 - 19 Jun 2023

Cited by 1 | Viewed by 1436

Abstract

Fish represent one of the most perishable food groups. Therefore, it is important to find viable alternatives that contribute to the preservation of quality and increase the shelf life of fishery products, and one alternative is to use natural extracts with antimicrobial activity. [...] Read more.

Fish represent one of the most perishable food groups. Therefore, it is important to find viable alternatives that contribute to the preservation of quality and increase the shelf life of fishery products, and one alternative is to use natural extracts with antimicrobial activity. The objective of this study was to determine the effect of a natural extract prepared with garlic (NGE) on the quality and shelf life of tilapia fillets stored on ice for 18 days. For this purpose, NGE was prepared by homogenizing peeled garlic cloves with distilled water, which were then centrifuged to obtain the extract (NGE); then, the fish fillets were immersed in the extract and were coated in NGE. The fillets with NGE were packed in high-density polyethylene bags and stored in crushed ice for 18 days. The adenosine 5′-triphosphate (ATP) and degradation products, K-value, color, texture, water holding capacity, pH, total mesophilic count, and total volatile bases (TVB-N) were monitored during storage. The ATP content, K-value, pH, total microbial count, and TVB-N changed with respect to ice storage time, and the results between fillets with NGE and control fillets differed. In conclusion, the application of NGE increased the shelf life of fillets stored on ice by 6 days, obtaining a shelf life of 18 days on ice, which shows its potential to improve the utilization of the species. Full article

(This article belongs to the Special Issue Trends and Advances in Seafood Quality: Processing, Preservation and Safety Processes to Guarantee Food Value)

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12 pages, 1161 KiB

Open AccessFeature PaperArticle

(Un)wanted Fish: Potential Consumers’ Acceptability of Landings in the Portuguese Case

by Jorge Ramos, Pedro G. Lino, Jaime Aníbal and Eduardo Esteves

Fishes 2023, 8(6), 324; https://doi.org/10.3390/fishes8060324 - 18 Jun 2023

Viewed by 1221

Abstract

The Landing Obligation (LO), introduced in 2015 by the Common Fisheries Policy of the European Union (EU-CFP), has been subject to a transitional period until recently. The rationale behind the measure is that all fish species subject to a total allowable catch (TAC) [...] Read more.

The Landing Obligation (LO), introduced in 2015 by the Common Fisheries Policy of the European Union (EU-CFP), has been subject to a transitional period until recently. The rationale behind the measure is that all fish species subject to a total allowable catch (TAC) must be landed to increase the sustainability of fishing activities. Through the analysis of official statistical data, it is possible to find out which species of fish were landed and their relative importance, including their monetary value, and verify the potential for consumer acceptance. Some insights are drawn from the interconnection between these three factors (i.e., social acceptability, landings of main fish species, and their market value) with empirical results and the scientific literature using data from Portugal. Full article

(This article belongs to the Special Issue Fisheries and Blue Economy)

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11 pages, 1630 KiB

Open AccessArticle

Increased Temperature and Discharge Influence Overwinter Growth and Survival of Juvenile Salmonids in a Hydropeaking River: Simulating Effects of Climate Change Using Individual-Based Modelling

by Johan Watz, Joel Schill, Louis Addo, John J. Piccolo and Mahboobeh Hajiesmaeili

Fishes 2023, 8(6), 323; https://doi.org/10.3390/fishes8060323 - 18 Jun 2023

Cited by 3 | Viewed by 1161

Abstract

Climate change causes warming of rivers and may increase discharge, particularly during winter. Downstream of hydropower plants, fluctuating water temperature and flow create dynamic overwintering conditions for juvenile salmonids. We used inSTREAM 7.2-SD to simulate the effects of increased temperature (+2 °C) and [...] Read more.

Climate change causes warming of rivers and may increase discharge, particularly during winter. Downstream of hydropower plants, fluctuating water temperature and flow create dynamic overwintering conditions for juvenile salmonids. We used inSTREAM 7.2-SD to simulate the effects of increased temperature (+2 °C) and discharge (+10%) on the overwinter growth and mortality of one-summer- and two-summer-old Atlantic salmon and brown trout in a river with a hydropeaking flow regime in a 2 × 2 design with replicated simulations. Water temperature had a major positive relationship with growth for both species and year classes, whereas increased flow alone had no major general effect on overwinter growth. For one-summer-old trout experiencing the high temperature regime, however, increased flow resulted in reduced growth. There were no major effects from temperature and flow on the survival rate of the two-summer-old fishes. On the other hand, there were significant interaction effects for the one-summer-olds, indicating that the effect of flow depended on temperature. For one-summer-old salmon, high flow resulted in increased survival in the low temperature regime, whereas it resulted in reduced survival in high temperature. In contrast, for one-summer-old trout, high flow resulted in reduced survival in the low temperature regime and increased survival in the high temperature. Different hydropower operation alternatives may interact with warming, affecting the relative competitive abilities of stream salmonids. Ecological models that predict the effects of different environmental conditions, such as temperature and flow regimes, may offer insight into such effects when in situ experiments are not feasible. Full article

(This article belongs to the Special Issue Effect of Climate Change on Salmonid Fishes in Rivers)

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17 pages, 1091 KiB

Open AccessArticle

Potential Influence of Shading in Freshwater Ponds on the Water Quality Parameters and the Hematological and Biochemical Profiles of Nile tilapia (Oreochromis niloticus Linnaeus, 1758)

by Geraldine B. Dayrit, Emmanuel M. Vera Cruz, Channarong Rodkhum, Mahmoud Mabrok, Pattareeya Ponza and Mudjekeewis D. Santos

Fishes 2023, 8(6), 322; https://doi.org/10.3390/fishes8060322 - 17 Jun 2023

Cited by 2 | Viewed by 2267

Abstract

Nile tilapia is a high-demand commodity in most developing countries including the Philippines, but its production is hampered by fluctuating water temperature (WT) and dissolved oxygen (DO) concentrations, which are mostly influenced by temperature warming. Net shading has been demonstrated to reduce pond [...] Read more.

Nile tilapia is a high-demand commodity in most developing countries including the Philippines, but its production is hampered by fluctuating water temperature (WT) and dissolved oxygen (DO) concentrations, which are mostly influenced by temperature warming. Net shading has been demonstrated to reduce pond temperature and increase the rate of spawning in cultured tilapia. The current study aimed to investigate the potential effects of shading on the water quality parameters, blood indices, and serum biochemical profiles of cultured Nile tilapia. Fish were collected from unshaded (control) and shaded (experimental) ponds in three breeding cycles. WT and DO concentrations were measured, while hematological and biochemical analyses were performed. The results showed that the average WT was considerably decreased in the shaded pond with no significant difference in the DO concentrations. Red blood cells, hemoglobin, and lymphocyte counts were significantly lower in fish raised in shaded ponds, although mean corpuscular volume and neutrophil counts were significantly higher. Likewise, Chole, TP, and Alb values were significantly affected by the interaction of cycle and shading setup. Cortisol, Glb, K⁺, Cl⁻, Mg²⁺, and TCa values showed significant differences and were only affected by the cycle. Similarly, AST and ALT values showed significant differences and were affected by both cycle and shading setup. Water quality parameters (WT and DO), hematological blood indices, and serum biochemical variables were correlated positively with each other. In brief, prior data imply that net shading can reduce WT in aquaculture ponds, reduce stress in Nile tilapia, and lessen the consequences of temperature warming on species production. Full article

(This article belongs to the Special Issue Response of Aquatic Animals to Environmental Changes)

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21 pages, 2276 KiB

Open AccessFeature PaperArticle

A Benchmark for Atlantic Salmon Conservation: Genetic Diversity and Structure in a Southern European Glacial Refuge before the Climate Changed

by Ana Almodóvar, Graciela G. Nicola, Daniel Ayllón, Sheila Leal, Daniel F. Marchán and Benigno Elvira

Fishes 2023, 8(6), 321; https://doi.org/10.3390/fishes8060321 - 16 Jun 2023

Cited by 2 | Viewed by 1376

Abstract

Atlantic salmon Salmo salar supports highly valuable commercial and recreational fisheries in Europe, but its stocks are currently overexploited and threatened by climate change. Its southernmost populations (in northern Spain) play a key role in conserving the species’ original genetic diversity, which is [...] Read more.

Atlantic salmon Salmo salar supports highly valuable commercial and recreational fisheries in Europe, but its stocks are currently overexploited and threatened by climate change. Its southernmost populations (in northern Spain) play a key role in conserving the species’ original genetic diversity, which is endangered due to decades-long (1970s to 1990s) massive stocking with non-native stocks. Their decline is well documented, but the effect of stock transfer and conservation efforts is unclear. Nine microsatellite loci were amplified from archival samples (scales from 1958–1959) from eight Spanish rivers to analyse the species’ natural genetic dynamics before its decline started. Allelic richness was high in the historical populations (the 1950s) and above most contemporary estimates. Private alleles were found in most rivers, indicating high local uniqueness and relative isolation among river basins. Some alleles are regional markers since they are rare or absent from contemporary northern European populations. Effective population size suggested good conservation status, with higher values than those estimated for contemporary populations. Strong population structure and genetic differentiation between rivers were found, with limited gene flow, restricted to geographically close populations. Our estimates of historical genetic diversity and structure from southernmost salmon populations are a powerful benchmark to guide conservation programs. Full article

(This article belongs to the Special Issue Effect of Climate Change on Salmonid Fishes in Rivers)

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14 pages, 1158 KiB

Open AccessArticle

Body Tactile Stimulation Reduces the Effects of High Stocking Density on the Welfare of Nile Tilapia (Oreochromis niloticus)

by Ana Carolina dos Santos Gauy, Marcela Cesar Bolognesi and Eliane Gonçalves-de-Freitas

Fishes 2023, 8(6), 320; https://doi.org/10.3390/fishes8060320 - 16 Jun 2023

Viewed by 1397

Abstract

High stocking density is used in aquaculture to optimize farming. However, such strategies can stress territorial fish by increasing aggression, thus harming the fish welfare and productive performance. Here, we tested the effect of long-term tactile body stimulation (TS) on alleviating the impact [...] Read more.

High stocking density is used in aquaculture to optimize farming. However, such strategies can stress territorial fish by increasing aggression, thus harming the fish welfare and productive performance. Here, we tested the effect of long-term tactile body stimulation (TS) on alleviating the impact of high stocking density in Nile tilapia (Oreochromis niloticus). Ten males were grouped for 21 days into four treatments (10 replicates each one) combining TS with high (1.2 kg·m³) or low (0.6 kg·m³) densities: (1) without TS and high density; (2) without TS and low density; (3) with TS and high density; and (4) with TS and low density. A rectangular PVC frame fitted with vertical plastic sticks sided with silicone bristles was placed in the center of aquarium. The fish receive TS when passing through the bristles. An apparatus without bristles was used as control. We found higher cortisol levels under TS conditions. All parameters of productive performance (growth, food efficiency, and condition factor) were higher in the treatment with TS and low density, lower in the treatment without TS and high density, and similar between treatments high density with TS and low density without TS. The results suggest that TS improves productive performance of Nile tilapia, counteracting the negative effects of high stocking density. Full article

(This article belongs to the Special Issue Advances in Tilapia Welfare—from Labs to Ponds)

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50 pages, 2487 KiB

Open AccessReview

A Comprehensive Review of the Impacts of Climate Change on Salmon: Strengths and Weaknesses of the Literature by Life Stage

by Lisa G. Crozier and Jared E. Siegel

Fishes 2023, 8(6), 319; https://doi.org/10.3390/fishes8060319 - 16 Jun 2023

Cited by 2 | Viewed by 5525

Abstract

As we confront novel environmental challenges, a full understanding of the physical and biological processes that govern species responses to climate change will help maintain biodiversity and support conservation measures that are more robust to irreducible uncertainty. However, climate impacts are so complex, [...] Read more.

As we confront novel environmental challenges, a full understanding of the physical and biological processes that govern species responses to climate change will help maintain biodiversity and support conservation measures that are more robust to irreducible uncertainty. However, climate impacts are so complex, and the literature on salmon and trout is so vast that researchers and decision makers scramble to make sense of it all. Therefore, we conducted a systematic literature review of climate impacts on salmon and anadromous trout as a resource for stakeholders, managers, and researchers. We reviewed studies published from 2010 to 2021 that address climate impacts on these fish and organized them in a database of 1169 physical and 1853 biological papers. Papers are labeled with keywords across eight categories related to subject matter and study methods. We compared the literature by biological process and life stage and used these comparisons to assess strengths and weaknesses. We then summarized expected phenotypic and genetic responses and management actions by life stage. Overall, we found the largest research gaps related to species interactions, behavioral responses, and effects that carry over across life stages. With this collection of the literature, we can better apply scarce conservation resources, fill knowledge gaps, and make informed decisions that do not ignore uncertainty. Full article

(This article belongs to the Special Issue Effect of Climate Change on Salmonid Fishes in Rivers)

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8 pages, 1723 KiB

Open AccessCommunication

West African Goliath Grouper: Where Are They between Senegal and Angola?

by João Pedro Barreiros and Felicia C. Coleman

Fishes 2023, 8(6), 318; https://doi.org/10.3390/fishes8060318 - 16 Jun 2023

Cited by 3 | Viewed by 2953

Abstract

The Atlantic Goliath Grouper Epinephelus itajara (Lichtenstein, 1822) occurs on both sides of the Atlantic, from the Carolinas (USA) to Brazil in the western Atlantic and historically from North Senegal to North Angola off of West Africa in the eastern Atlantic. While there [...] Read more.

The Atlantic Goliath Grouper Epinephelus itajara (Lichtenstein, 1822) occurs on both sides of the Atlantic, from the Carolinas (USA) to Brazil in the western Atlantic and historically from North Senegal to North Angola off of West Africa in the eastern Atlantic. While there are relatively good data on their distribution in the western Atlantic, confirmed occurrences, population status, fishing reports, and trade data are almost non-existent for West Africa. Part of the problem is that tropical West African countries largely lack the wherewithal to fund the research needed to evaluate this species, nor do they have laws, management plans, or viable enforcement measures that might lead to effective population recovery or protection for essential juvenile mangrove habitats. Given the lack of published studies on this species in West Africa, the primary objectives of this paper are (1) to describe all known historical and current anecdotal information available on this species and (2) to encourage the increased monitoring of habitats where viable populations might still occur (i.e., mangroves, oil rigs, and oil platforms). Full article

(This article belongs to the Special Issue Advances in Atlantic Goliath Grouper Research)

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15 pages, 2404 KiB

Open AccessArticle

Differentiation of Spatial Units of Genus Euthynnus from the Eastern Atlantic and the Mediterranean Using Otolith Shape Analysis

by Rubén Muñoz-Lechuga, Fambaye Ngom Sow, Diaha N’Guessan Constance, Davy Angueko, David Macías, Alexia Massa-Gallucci, Guelson Batista da Silva, Jorge M. S. Gonçalves and Pedro G. Lino

Fishes 2023, 8(6), 317; https://doi.org/10.3390/fishes8060317 - 15 Jun 2023

Cited by 1 | Viewed by 1179

Abstract

The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover [...] Read more.

The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected. Full article

(This article belongs to the Special Issue Otoliths and Their Applications in Fishery Science II)

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18 pages, 2067 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Selected Review of Impacts of Ocean Deoxygenation on Fish and Fisheries

by Hongsik Kim, Ana C. Franco and U. Rashid Sumaila

Fishes 2023, 8(6), 316; https://doi.org/10.3390/fishes8060316 - 14 Jun 2023

Cited by 3 | Viewed by 2894

Abstract

Oxygen is crucial for the survival of marine species. Yet, the ocean has experienced a loss of approximately 2% of its oxygen inventory since the last century, resulting in adverse impacts on marine life and ecosystems. In particular, changes in the gap between [...] Read more.

Oxygen is crucial for the survival of marine species. Yet, the ocean has experienced a loss of approximately 2% of its oxygen inventory since the last century, resulting in adverse impacts on marine life and ecosystems. In particular, changes in the gap between the supply and demand for dissolved oxygen lead to physiological and ecological variations, which cause alterations in habitats and food webs for fish and ecosystem services. These changes vary over time and by region, and the heterogeneous characteristics of marine species bring about non-linear consequences to human society. Despite this, identifying the potential ripple effects of deoxygenation on human society is challenging due to the integrated impacts of other stressors, such as global warming and ocean acidification, and their varying changes depending on environmental conditions and regions, such as upwelling and eutrophication. Therefore, we conducted a literature review on ocean deoxygenation and its effects on fish dynamics and the ecosystem, with a focus on the environmental and societal impact, to present crucial considerations and pathways for future research on ocean deoxygenation. We found that quantitative approaches are necessary to assess the dynamic changes under deoxygenation, and the consequent effects on marine ecosystems should be verified to exploit the natural resources from the ocean. One of the most reliable approaches to quantifying the ripple impacts of deoxygenation is to model spatial and temporal changes with other climate stressors, forming a global network encompassing socio-economic and regional effects of this global change to facilitate and improve capabilities to address the impacts of ocean deoxygenation. Full article

(This article belongs to the Special Issue Fisheries Policies and Management)

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10 pages, 2669 KiB

Open AccessFeature PaperArticle

Consistent Antipredator Behavioral Responses among Populations of Red River Pupfish with Disparate Predator Communities

by Cody M. Anderson, Brian D. Wisenden, Cody A. Craig and Craig A. Stockwell

Fishes 2023, 8(6), 315; https://doi.org/10.3390/fishes8060315 - 13 Jun 2023

Cited by 1 | Viewed by 928

Abstract

Many desert fishes, which evolved in isolated aquatic “islands” with limited predation pressure, have been severely impacted by non-native predators. These impacts have been attributed to the evolutionary loss of antipredator competence, known as the predator naiveté hypothesis. Recent work provided support for [...] Read more.

Many desert fishes, which evolved in isolated aquatic “islands” with limited predation pressure, have been severely impacted by non-native predators. These impacts have been attributed to the evolutionary loss of antipredator competence, known as the predator naiveté hypothesis. Recent work provided support for this hypothesis for one desert fish species. We sought to examine the generality of the predator naiveté hypothesis by evaluating antipredator competence in five populations of Red River pupfish (Cyprinodon rubrofluviatilis), a species that occupies habitats that vary in the degree of isolation and levels of fish species richness. Fish were exposed to a conspecific chemical alarm cue released from damaged epidermal tissue as a general assay of antipredator response. We found that pupfish from all five populations exhibited antipredator behavior in response to the alarm cue, regardless of the exposure to predation risk. These data provide evidence that antipredator responses to alarm cues are conserved in Red River pupfish, even in populations isolated from piscivorous species. Full article

(This article belongs to the Section Biology and Ecology)

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15 pages, 2558 KiB

Open AccessEditor’s ChoiceArticle

Lionfish Diet Composition at Three Study Sites in the Aegean Sea: An Invasive Generalist?

by Ioannis E. Batjakas, Athanasios Evangelopoulos, Maria Giannou, Sofia Pappou, Eleftheria Papanikola, Maria Atsikvasi, Dimitris Poursanidis and Chrysoula Gubili

Fishes 2023, 8(6), 314; https://doi.org/10.3390/fishes8060314 - 13 Jun 2023

Cited by 3 | Viewed by 1409

Abstract

The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in [...] Read more.

The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in terms of numerical abundance and frequency of occurrence was used to compare lionfish’s diet between these sites. Lionfish largely preyed upon teleosts (4% to 83% numerical abundance and 16% to 58% frequency of occurrence, depending on the site) and decapods (12% to 95% numerical abundance and 11% to 81% frequency of occurrence). The most important teleost families in lionfish’s diet were Gobiidae, Labridae, and Scorpaenidae, while decapods and especially the family Scyllaridae and the genus Plesionika were the dominant decapod prey items. The lionfish was found to be an especially successful generalist across the study sites, an opportunistic, predatory species overall, and at the same time, at a local level, it seems to be an equally successful specialist that could increase the predation mortality of already stressed prey populations and can be a serious threat to endemic, critically endangered, and/or commercially important species. Full article

(This article belongs to the Special Issue Advances in Ecology and Management of Aquatic Invasive Species)

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14 pages, 2792 KiB

Open AccessArticle

Hierarchical Interaction between Food Diversity and Competition in Brackish Fish Species in South Korea

by Tae-Sik Yu, Chang Woo Ji and Ihn-Sil Kwak

Fishes 2023, 8(6), 313; https://doi.org/10.3390/fishes8060313 - 13 Jun 2023

Viewed by 1034

Abstract

Information about the food sources for fish is important not only for predation and food competition, but also for the direct impact on organism interactions, relationships, and biodiversity within aquatic ecosystems. We analyzed the food sources of 21 fish species in 9 families [...] Read more.

Information about the food sources for fish is important not only for predation and food competition, but also for the direct impact on organism interactions, relationships, and biodiversity within aquatic ecosystems. We analyzed the food sources of 21 fish species in 9 families of 6 orders based on the literature data from brackish ecosystems in South Korea to improve the understanding of the estuarine ecosystem. The food sources of the 21 fish species contained 173 families, 86 orders, 39 classes, and 22 phyla. The 21 fish species were classified into 4 groups using hierarchical analysis based on their food sources: Group 1 fishes mainly consumed Amphipoda; Group 2 fishes were zooplanktivores; Group 3 were omnivorous; and Group 4 consumed small food sources, such as Nematoda, Corophiidae, and Harpacticidae. The feeding competition index was relatively high within each group, but the competition index for Group 3, the omnivorous fishes, was low. Network analysis and hub scores represented the importance of food sources consumed by each fish species by showing the connections between the fish and their prey. Polychaeta, Actinopterygii, and Decapoda were the most commonly consumed food sources. Food source diversity was high for zooplanktivores (group 2). Additionally, the food contents of each fish species were classified into freshwater and marine sources for identifying the habitats of the food sources. Trophic level measuring values using the data were similar to the reported literature data. This study can be utilized for understanding estuarine ecosystems and identifying food relationships. Full article

(This article belongs to the Section Nutrition and Feeding)

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14 pages, 1180 KiB

Open AccessFeature PaperArticle

Short and Long-Term Effects of Early and Late Weaning on Atlantic Cod, Gadus morhua

by Velmurugu Puvanendran and Øyvind J. Hansen

Fishes 2023, 8(6), 312; https://doi.org/10.3390/fishes8060312 - 13 Jun 2023

Viewed by 1231

Abstract

Studies have shown negative short-term effects of early weaning (EW) in finfish larvae but information on long-term effects of EW on growth and subsequent economic loss is lacking. We evaluated the short- and long-term effects of EW and late weaning (LW) on Atlantic [...] Read more.

Studies have shown negative short-term effects of early weaning (EW) in finfish larvae but information on long-term effects of EW on growth and subsequent economic loss is lacking. We evaluated the short- and long-term effects of EW and late weaning (LW) on Atlantic cod. Cod larvae were fed with enriched rotifers from 2 to 35 days post-hatch (dph) and weaning carried out from 21 to 35 dph (EW) or with enriched rotifers from 2 to 29 dph followed by enriched Artemia nauplii from 25 to 56 dph and weaning carried out from 45 to 56 dph (LW). At 190 dph, 50 fish from each tank were tagged with an electronic tag and were transferred to sea cages at 10 months old. At the end of 30 months post-hatch, the weight of the fish was recorded. Our results showed a significant short-term effect of the weaning method on the growth of Atlantic cod at 65 dph, but no significant difference at 90 and 190 dph. However, fish from LW showed a significantly higher body weight compared to fish from EW at 30 months post-hatch. A cost analysis indicated substantial benefit for commercial cod farming by using LW and we recommend using LW to gain sizable financial benefit. Full article

(This article belongs to the Section Sustainable Aquaculture)

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25 pages, 1301 KiB

Open AccessEditor’s ChoiceReview

Non-Linear Analyses of Fish Behaviours in Response to Aquatic Environmental Pollutants—A Review

by Harkaitz Eguiraun and Iciar Martinez

Fishes 2023, 8(6), 311; https://doi.org/10.3390/fishes8060311 - 12 Jun 2023

Viewed by 1286

Abstract

Analysis of fish behaviour is an effective way to indirectly identify the presence of environmental pollutants that negatively affect fish life, its production and quality. Monitoring individual and collective behaviours produces large amounts of non-linear data that require tailor-suited computational methods to interpret [...] Read more.

Analysis of fish behaviour is an effective way to indirectly identify the presence of environmental pollutants that negatively affect fish life, its production and quality. Monitoring individual and collective behaviours produces large amounts of non-linear data that require tailor-suited computational methods to interpret and manage the information. Fractal dimension (FD) and entropy are two groups of such non-linear analysing methods that serve as indicators of the complexity (FD) and predictability (entropy) of the behaviours. Since behavioural complexity and predictability may be modulated by contaminants, the changes in its FD and entropy values have a clear potential to be embedded in a biological early warning system (BEWS), which may be particularly useful in Precision Fish Farming settings and to monitor wild populations. This work presents a review of the effects of a wide range of environmental contaminants, including toxic compounds, cleaning and disinfecting agents, stimulant (caffeine), anaesthetics and antibiotics, heavy metals (lead, cupper, and mercury), selenium, pesticides and persistent environmental pollutants, on the FD and entropy values of collective and individual behavioural responses of different fish species. All the revised studies demonstrate the usefulness of both FD and entropy to indicate the presence of pollutants and underline the need to consider early changes in the trend of the evolution of their values prior to them becoming significantly different from the control values, i.e., while it is still possible to identify the contaminant and preserve the health and integrity of the fish. Full article

(This article belongs to the Special Issue Trace Elements, Drugs, Small Compounds and Antioxidants in Fish)

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16 pages, 4684 KiB

Open AccessArticle

DUSP2 Deletion Inhibits Macrophage Migration by Inhibiting ERK Activation in Zebrafish

by Yu-Jiao Li, Xin-Liang Wang, Ling-Yu Shi, Zong-Yi Wang, Zi-Ang Zhao, Shu-Chao Ge and Bing Hu

Fishes 2023, 8(6), 310; https://doi.org/10.3390/fishes8060310 - 12 Jun 2023

Viewed by 1023

Abstract

Dual-specificity phosphatase 2 (DUSP2) regulates the activation of members of the mitogen-activated protein kinase (MAPK) family, which is involved in a variety of cellular processes including cell proliferation, differentiation, apoptosis, and migration. DUSP2 also regulates the expression of inflammatory mediators in macrophages; however, [...] Read more.

Dual-specificity phosphatase 2 (DUSP2) regulates the activation of members of the mitogen-activated protein kinase (MAPK) family, which is involved in a variety of cellular processes including cell proliferation, differentiation, apoptosis, and migration. DUSP2 also regulates the expression of inflammatory mediators in macrophages; however, it remains unknown whether DUSP2 participates in macrophage migration. Here, using the tail fin injury model in zebrafish larvae, we found that the deletion of DUSP2 inhibited the expression of pro-inflammatory cytokines and macrophage chemokines. Moreover, live imaging results showed that the migration of macrophages to the injury site was inhibited after DUSP2 deletion. This inhibitory effect was mediated through the reduced activation of extracellular regulated protein kinases (ERK) in DUSP2 knockout zebrafish. Full article

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13 pages, 2170 KiB

Open AccessArticle

Transcriptome Analysis Reveals Differences in Gene Expression in the Muscle of the Brown-Marbled Grouper (Epinephelus fuscoguttatus) with Different Growth Rates

by Tong Wang, Yang Yang, Shirui Gong, Xi Wu, Leilei Zeng, Yuhao Tao, Chaoyue Zhong, Leling Song and Xiaochun Liu

Fishes 2023, 8(6), 309; https://doi.org/10.3390/fishes8060309 - 08 Jun 2023

Viewed by 1302

Abstract

Brown-marbled grouper is one of the most important mariculture species in China and is widely used as a crossbreeding parent in the grouper industry. Enhancing growth rates is a key target in fish breeding, and gaining insight into the underlying mechanisms responsible for [...] Read more.

Brown-marbled grouper is one of the most important mariculture species in China and is widely used as a crossbreeding parent in the grouper industry. Enhancing growth rates is a key target in fish breeding, and gaining insight into the underlying mechanisms responsible for growth differences between individuals can aid in the improvement of grouper growth rates. However, the mechanism behind growth differences in this fish remains unclear. We analyzed the transcriptome profiles of muscle tissues between fast- and slow-growing brown-marbled grouper using RNA-seq and identified 77 significantly up-regulated genes and 92 significantly down-regulated genes in the extreme growth groups. Our findings suggest that up-regulated genes such as ghr and tnni2, as well as down-regulated genes such as stc2 and pdp1, are associated with growth advantages in brown-marbled grouper. We used differentially expressed genes (DEGs) for GO and KEGG enrichment analyses. The results of the GO enrichments showed that the significantly up-regulated genes in the fast-growing group were involved in protein folding, the actin cytoskeleton, the myosin complex, and other processes. The results of the KEGG enrichments showed that the significantly up-regulated genes in the fast-growing group were involved in various pathways such as glycolysis/gluconeogenesis, adipocytokine signaling, MAPK signaling, carbon metabolism, and PI3K-Akt signaling. Additionally, gene set enrichment analysis (GSEA) showed that the PI3K/AKT/mTOR pathway was up-regulated in the fast-growing group, which may be responsible for the higher nutrient absorption efficiency and muscle growth in these fish. Our results contribute to a better understanding of the molecular mechanisms and regulatory pathways underlying fast growth in brown-marbled grouper. However, further studies are necessary to fully elucidate the mechanisms behind growth differences between individuals. Full article

(This article belongs to the Special Issue Application of Transcriptomics in Fish)

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12 pages, 2161 KiB

Open AccessArticle

Immunoregulation and Resistance to Aquatic Pathogens with Dietary Nucleotides in Pacific White Shrimp, Litopenaeus vannamei

by Sergi Segarra, Thanh Chau, Phuc Hoang and Loc Tran

Fishes 2023, 8(6), 308; https://doi.org/10.3390/fishes8060308 - 08 Jun 2023

Viewed by 1448

Abstract

Using vegetable protein sources as a replacement for fish meal (FM) in the diet of Pacific white shrimp (PWS) has a negative impact on their health. Acute hepatopancreatic necrosis disease (AHPND), caused by Vibrio parahaemolyticus, affects PWS and causes financial losses. Nucleotides [...] Read more.

Using vegetable protein sources as a replacement for fish meal (FM) in the diet of Pacific white shrimp (PWS) has a negative impact on their health. Acute hepatopancreatic necrosis disease (AHPND), caused by Vibrio parahaemolyticus, affects PWS and causes financial losses. Nucleotides modulate the immune response and could contribute to counteracting these issues. Our objective was to evaluate the effects of nucleotide supplementation on performance, immune response, and survival when challenged with V. parahaemolyticus, in PWS receiving a diet with FM partially replaced with vegetable protein sources. A feeding trial (1000 PWS; 56 days) and a challenge trial (600 PWS; 10 days) were performed using diets with different FM inclusion levels (26%, 23.4%, 22.1%, and 20.8%), with or without 0.1% nucleotides. A non-challenged, non-supplemented group was also used in the challenge trial. Adding nucleotides to diets with reduced FM allowed significantly better results in growth performance parameters and total hemocyte count (THC). In the challenge trial, compared to control, nucleotide supplementation led to significantly higher THC and survival rate 15 h post-challenge. In conclusion, adding nucleotides to PWS diets improves their immune response and resistance to aquatic pathogens, allowing FM to be replaced by vegetable protein sources without negatively affecting performance. Full article

(This article belongs to the Special Issue Disease Control in Fish and Shrimp Aquaculture)

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12 pages, 3231 KiB

Open AccessArticle

Elevated Carbon Dioxide and Its Impact on Growth, Blood Properties, and Vertebral Column of Freshwater Fish Mahseer, Tor tambroides Juveniles

by Nur Syuhada Iskandar, Noorashikin Md Noor, Zaidi Che Cob and Simon Kumar Das

Fishes 2023, 8(6), 307; https://doi.org/10.3390/fishes8060307 - 07 Jun 2023

Cited by 1 | Viewed by 1132

Abstract

The level of carbon dioxide, which resembles water acidification, is critical to the success of juvenile fish production. The growth, skeletal deformities, and blood parameters of the economically important freshwater fish mahseer, Tor tambroides, were assessed in different concentrations of pCO₂ [...] Read more.

The level of carbon dioxide, which resembles water acidification, is critical to the success of juvenile fish production. The growth, skeletal deformities, and blood parameters of the economically important freshwater fish mahseer, Tor tambroides, were assessed in different concentrations of pCO₂ (400, 700, and 1000 µatm pCO₂). The highest growth properties (survival rate, body weight gain (BWG), specific growth rate (SGR)) in mahseer were observed at 400 µatm, whereas the lowest growth indices were found in the treatment of 1000 µatm pCO₂. The lowest pCO₂ concentration was found to be within the optimum healthy blood parameter range. The fish exposed to acidic conditions (700 and 1000 µatm) exhibited considerably higher levels of haemoglobin and haematocrit compared to the control fish. Glucose levels were significantly lower in the acidic conditions, while total cholesterol levels in mahseer fish exposed to acidic conditions were higher. The fish displayed skeleton malformations as the concentration of pCO₂ was elevated. The findings from this research could be set as a standard technique in the juvenile rearing of mahseer fish under acidified conditions. Full article

(This article belongs to the Special Issue Interactive Effects of Climate Change, Invasive Species, and Native Fish in Freshwater Ecosystems)

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18 pages, 1386 KiB

Open AccessReview

A Synthesis of the Ecology and Conservation of Pseudoplatystoma Catfishes in the Neotropics

by Luciana A. Pereira, Leandro Castello, Donald J. Orth, Fabrice Duponchelle and Eric M. Hallerman

Fishes 2023, 8(6), 306; https://doi.org/10.3390/fishes8060306 - 07 Jun 2023

Cited by 1 | Viewed by 3243

Abstract

Species of the genus Pseudoplatystoma, the long-whiskered catfishes, are important in commercial and recreational fisheries in South America, and some species have become key to regional aquaculture. Some species of the genus are under pressure due to overfishing and the negative impacts [...] Read more.

Species of the genus Pseudoplatystoma, the long-whiskered catfishes, are important in commercial and recreational fisheries in South America, and some species have become key to regional aquaculture. Some species of the genus are under pressure due to overfishing and the negative impacts of dams. Six questions are asked in this review: (i) What species are in the genus, and where are they distributed? (ii) What are the life histories and ecologies of Pseudoplatystoma species? (iii) What are the patterns of somatic growth for these species? (iv) What is known about the biomass, production, and population dynamics of Pseudoplatystoma? (v) What is the geographic distribution of genetic variation within Pseudoplatystoma species? (vi) What are the threats to the conservation of these species? The taxonomy of the genus currently includes eight species, respectively, distributed over the Orinoco, Amazon, Paraná, and São Francisco basins. Pseudoplatystoma catfishes typically exhibit longitudinal migrations for reproduction and lateral migration for feeding, but these patterns may vary among populations. The size of the first maturation of these catfishes varies between 57 cm to 82 cm in total length. Five of the eight species spawn during the rising water season. Pseudoplatystoma species can grow to about 130 cm in total length and 100 Kg in weight and live until 30 years of age, depending upon the species. Biomass production and population dynamics of these catfishes have not yet been fully described. Their life-history characteristics indicate that they are periodic strategists with associated population recruitment dynamics. Population genetic patterning varies among Pseudoplatystoma species, with some degree of homing behavior and genetic differentiation among populations, indicating the need for management by applying the Management Unit and perhaps Evolutionary Significant Unit concepts. The main threats to the persistence of these catfishes are overfishing and alterations in and obstruction of river flow due to the construction of hydropower dams. After synthesizing existing information on species of the genus Pseudoplatystoma, we offer suggestions for future research to fill critical gaps in the knowledge of this group. Full article

(This article belongs to the Section Biology and Ecology)

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19 pages, 5419 KiB

Open AccessFeature PaperArticle

The Population Development of the Invasive Round Goby Neogobius melanostomus in Latvian Waters of the Baltic Sea

by Eriks Kruze, Andris Avotins, Loreta Rozenfelde, Ivars Putnis, Ivo Sics, Laura Briekmane and Jens Olsson

Fishes 2023, 8(6), 305; https://doi.org/10.3390/fishes8060305 - 07 Jun 2023

Cited by 1 | Viewed by 1935

Abstract

The invasive round goby (Neogobius melanostomus) was established in the coastal waters of the Baltic Sea in the early 1990s. The first observation of the species in Latvian waters was in 2004. In the intervening period, the population grew, the species [...] Read more.

The invasive round goby (Neogobius melanostomus) was established in the coastal waters of the Baltic Sea in the early 1990s. The first observation of the species in Latvian waters was in 2004. In the intervening period, the population grew, the species became of significance for local fisheries, and it likely impacted the local ecosystem in the Baltic Sea. In this study, we characterize the spatial–temporal population development of round goby in Latvian coastal waters using data from three different scientific and fisheries-independent surveys. We also include data from commercial fisheries landings to describe the fisheries targeting the species. Our results suggest an exponential increase in population numbers of round goby in Latvian waters, peaking in 2018, followed by a sharp decline. This observation is also supported by data from commercial fisheries landings. We suggest that intensive commercial fishing had a considerable impact on the rapid decline of the species, but that the decline was potentially amplified through a wider scale decline, as observed in many areas of the Baltic Sea. The results of this study contribute to the knowledge base on the species and how fisheries can aid in limiting the development of invasive fish populations. Based on the results of the study, we also provide recommendations for better future monitoring of the species in the coastal waters of the Baltic Sea. Full article

(This article belongs to the Special Issue Advances in Ecology and Management of Aquatic Invasive Species)

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12 pages, 611 KiB

Open AccessArticle

Profiling a New Postbiotic Product for Its Application in Fish Aquaculture

by Mario Quintanilla-Pineda, Jesús Díaz, Ana Gutiérrez-Falcon, Francisco C. Ibañez and Florencio Marzo

Fishes 2023, 8(6), 304; https://doi.org/10.3390/fishes8060304 - 06 Jun 2023

Cited by 1 | Viewed by 1332

Abstract

Weissella cibaria is a lactic acid bacteria that has been receiving great interest in the last decade; however, its research into aquaculture remains insufficient. In this context, the resistance to pH 3–5, bile salts (10–20%), hydrophobicity, and carbohydrate metabolisms of two W. cibaria [...] Read more.

Weissella cibaria is a lactic acid bacteria that has been receiving great interest in the last decade; however, its research into aquaculture remains insufficient. In this context, the resistance to pH 3–5, bile salts (10–20%), hydrophobicity, and carbohydrate metabolisms of two W. cibaria strains isolated from rainbow trout were evaluated. At the same time, the postbiotic products of both W. cibaria were produced under different conditions, and their stability to heat (95–130 °C) and proteolytic enzymes were determined. The low pH sensitivity of two pathogens (Aeromonas salmonicida subsp. salmonicida and Yersinia ruckeri) was also recorded. Both strains of W. cibaria survived pH and bile salt treatments. Neither expressed enzymatic activity or hydrophobic characteristics with the executed methods. Treatment with heat, enzymes, and transfer to vegetal broth significantly reduced (p < 0.05) the postbiotic product’s antibacterial activity. On the other hand, no significant difference (p < 0.05) was reported in antibacterial characteristics when postbiotics were produced by coculturing both strains. Low pH does not significantly influence pathogen growth (p < 0.05). Our findings suggest that the studied strains do not adjust as probiotics, but the postbiotic product obtained from them could become a promising tool as a supplement food for fish aquaculture applications. Full article

(This article belongs to the Special Issue Feed Additives in Aquaculture)

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12 pages, 1151 KiB

Open AccessArticle

High-Temperature Stress Induces Autophagy in Rainbow Trout Skeletal Muscle

by Alfredo Molina, Phillip Dettleff, Valentina Valenzuela-Muñoz, Cristian Gallardo-Escarate and Juan Antonio Valdés

Fishes 2023, 8(6), 303; https://doi.org/10.3390/fishes8060303 - 06 Jun 2023

Cited by 6 | Viewed by 1888

Abstract

Ectothermic animals, such as teleosts, have increasingly been exposed to stressful high-temperature events due to global warming. Currently, the effects of thermal stress on skeletal muscle, a key tissue for fish growth, are unknown. This study examined the impact of high-temperature stress on [...] Read more.

Ectothermic animals, such as teleosts, have increasingly been exposed to stressful high-temperature events due to global warming. Currently, the effects of thermal stress on skeletal muscle, a key tissue for fish growth, are unknown. This study examined the impact of high-temperature stress on the skeletal muscle transcriptome of rainbow trout (Oncorhynchus mykiss) in control (15 °C) and high-temperature (20 °C) conditions. Additionally, we examined the plasmatic levels of cortisol, glucose, and creatine kinase activity, and examined oxidative damage and autophagy activation in skeletal muscle. High-temperature stress induced significant increases in cortisol and glucose plasmatic levels. Nevertheless, no changes were observed in creatine kinase activity in plasma and skeletal muscle oxidation. Skeletal muscle RNA was isolated and sequenced using the HiSeq Illumina platform. A total of 383,796,290 reads were mapped onto the reference rainbow trout genome. The transcriptomic analysis showed that 293 genes were upregulated in the high-temperature group, mainly associated with autophagosome assembly, amino acid transport, and the glutamine metabolic process. On the other hand, 119 genes were downregulated in the high-temperature group, mainly associated with digestion, proteolysis, and the muscle contraction process. In addition, RT-qPCR of differentially expressed representative genes and Western blot analysis of LC3-II/LC3-I levels confirmed skeletal muscle autophagy induced by high temperature. This study sheds light on intriguing facets of the adaptive response of rainbow trout skeletal muscle to high-temperature stress and provides significant insights into the physiology of autophagy in teleosts. Full article

(This article belongs to the Special Issue Effect of Climate Change on Salmonid Fishes in Rivers)

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