Fishes

15 pages, 8048 KiB

Open AccessArticle

Effects of High Dietary Starch Levels on the Growth Performance, Liver Function, and Metabolome of Largemouth Bass (Micropterus salmoides)

by Lihui Sun, Jianlin Guo, Qian Li, Jianhu Jiang, Jianming Chen, Lingmei Gao, Bicheng Yang and Jun Peng

Fishes 2024, 9(7), 256; https://doi.org/10.3390/fishes9070256 - 2 Jul 2024

Abstract

In this study, we conducted a 16-week feeding trial to investigate the effects of a high-cassava starch diet on growth performance, liver function, and metabolism in largemouth bass (Micropterus salmoides). We formulated five diets containing varying levels of cassava starch: 12%, [...] Read more.

In this study, we conducted a 16-week feeding trial to investigate the effects of a high-cassava starch diet on growth performance, liver function, and metabolism in largemouth bass (Micropterus salmoides). We formulated five diets containing varying levels of cassava starch: 12%, 9%, 6%, 3%, and 0% (termed M12, M9, M6, M3, and M0, respectively). We distributed these diets among largemouth bass with the initial body weight of 83.33 ± 0.55 g via an in-pond “raceway” aquaculture system. Our findings suggest that high level (12%) of cassava starch dietary inclusion adversely affected growth performance metrics such as weight gain rate and specific growth rate, along with feed utilization efficiency indicators, including protein efficiency, protein deposition rate, and the apparent digestibility of dry matter and protein. This negative impact was accompanied by a decrease in intestinal amylase activity. Through further transcriptomic analysis, we identified several key genes associated with carbohydrate metabolism, which underwent changes influencing liver function. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed the involvement of these differentially expressed genes (DEGs) in the tricarboxylic acid cycle (TCA cycle). Comparative metabolomics analysis further indicated that the M9 group showed significant enrichment in pathways related to amino acid metabolism and alterations in the levels of metabolites involved in carbohydrate metabolism. In conclusion, our study demonstrates that incorporating up to 9% cassava starch in the diet can enhance growth performance in largemouth bass by stimulating digestive enzyme activities and promoting glucose utilization. Full article

(This article belongs to the Special Issue Physiological Response Mechanism of Aquatic Animals to Stress)

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10 pages, 1614 KiB

Open AccessCommunication

Population Dynamics Parameters and Exploitation Status of 55 Commercial Species in Egyptian Red Sea Fisheries: A Key to Sustainable Fisheries

by Sahar F. Mehanna and Mohamed Samy-Kamal

Fishes 2024, 9(7), 255; https://doi.org/10.3390/fishes9070255 - 2 Jul 2024

Abstract

Egyptian Red Sea fisheries face the same challenges as most of the world’s fisheries, including overexploitation, habitat loss, IUU fishing, pollution, and climate change. These fisheries are highly diverse with multiple species targeted by multiple fleets, using different fishing gears. Much work has [...] Read more.

Egyptian Red Sea fisheries face the same challenges as most of the world’s fisheries, including overexploitation, habitat loss, IUU fishing, pollution, and climate change. These fisheries are highly diverse with multiple species targeted by multiple fleets, using different fishing gears. Much work has been performed in recent years to assess Red Sea fish stocks. However, not all fish stocks in the Egyptian Red Sea are assessed, and those that are assessed only cover 30% of landings. The assessments are unbalanced by area, with the Gulf of Suez being much better covered than the southern Red Sea and Gulf of Aqaba. The results show that most of the analyzed stocks are overexploited. There is an urgent need to take action to protect, conserve, and restore the different fish stocks in different fishing grounds. These actions will ensure the sustainability of the fisheries, making them ecologically friendly and economically and socially efficient. Full article

(This article belongs to the Special Issue Diagnosis and Management of Small-Scale and Data-Limited Fisheries)

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15 pages, 9111 KiB

Open AccessArticle

Integrated Rice–Fish Culture Alters the Bacterioplankton Community and Its Assembly Processes

by Weixu Diao, Julin Yuan, Rui Jia, Yiran Hou, Liqiang Zhang, Bing Li and Jian Zhu

Fishes 2024, 9(7), 254; https://doi.org/10.3390/fishes9070254 - 2 Jul 2024

Abstract

The rice–fish co-culture is an important model of carp farming in China; however, research on the dynamics and assembly of water bacterial communities in this system remains limited. Therefore, this study aimed to explore the dynamics and assembly of bacterial communities, as well [...] Read more.

The rice–fish co-culture is an important model of carp farming in China; however, research on the dynamics and assembly of water bacterial communities in this system remains limited. Therefore, this study aimed to explore the dynamics and assembly of bacterial communities, as well as their correlation with environmental factors in paddy water. For these purposes, this study was divided into two groups: a rice–carp co-culture (WRC) group and a rice monoculture (WRM) group, with 20 rice fields in each group. After 60 days of farming, the concentrations of NH₄⁺-N, NO₂⁻-N, TN, and PO₄³⁻ were significantly higher in the WRC group than those in the WRM group. Alpha diversity analysis showed that the Shannon index in the WRC group was significantly decreased compared with the WRM group. At the phylum level, the relative abundance of Actinobacteria significantly increased, while the relative abundance of Proteobacteria and Bacteroidetes significantly decreased in the paddy water of the WRC group. The neutral community model (NCM) indicated that a random process played a dominant role in the construction of bacterial communities in the two groups, and common carp cultivation increased migration rates, thereby affecting community assembly. The co-occurrence network displayed that common carp cultivation led to looser interactions between bacterial communities. In addition, the contents of nutrients significantly affected the abundance of bacteria in paddy water. In summary, carp cultivation decreased the diversity of bacteria and changed the relative abundance of dominant bacteria, thereby affecting the stability and assembly of bacterial communities. Full article

(This article belongs to the Special Issue Aquaculture Ecology and the Environmental Microbiome)

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16 pages, 6965 KiB

Open AccessArticle

Spatiotemporal Variation and Predictors of the Purpleback Flying Squid (Sthenoteuthis oualaniensis) Distribution Surrounding the **sha and Zhongsha Islands during a Fishing Moratorium

by Liangming Wang, Chang** Yang, Binbin Shan, Yan Liu, Jianwei Zou, Dianrong Sun and Tao Guo

Fishes 2024, 9(7), 253; https://doi.org/10.3390/fishes9070253 - 1 Jul 2024

Abstract

As an economic species widely distributed in the South China Sea (SCS), the purpleback flying squid (Sthenoteuthis oualaniensis) still has a large potential for exploitation, and the variations in its use as a resource are highly correlated with environmental and other [...] Read more.

As an economic species widely distributed in the South China Sea (SCS), the purpleback flying squid (Sthenoteuthis oualaniensis) still has a large potential for exploitation, and the variations in its use as a resource are highly correlated with environmental and other factors. In this study, using a generalized additive model (GAM) and gradient forest analysis (GFA), in conjunction with environmental factors, the distribution of purpleback flying squid surrounding the **sha and Zhongsha islands during the fishing moratorium period was investigated. The results indicated that catch per unit effort (CPUE) had a gradual increase from May to July 2023 in the primary fishing area surrounded the **sha Islands during May to June, then moved southward towards 13–15° N after July. CPUE is used as an important indicator to reflect the abundance of the fishery, while the GFA results show that CPUE has a better fit than catch in this study. Therefore, the subsequent analysis focused on CPUE. Longitude and sea surface temperature (SST) were of relative higher importance, followed by sea surface salinity (SSS), latitude, chlorophyll a concentration (Chla), sea surface height (SSH), and mixed layer depth (MLD). Longitude and CPUE had a significant, positive correlation. The CPUE gradually increased with latitude within 14–16° N. The CPUE increased slowly as SST increased from 29.5 to 30.5 °C in the primary fishing area. The Chla in this fishing zone was 0–0.2 mg/m³ and displayed a significant positive association with CPUE. Conversely, SSS, SSH, and MLD had negative correlations with CPUE. These findings will promote the sustainable utilization of purpleback flying squid in the SCS. Full article

(This article belongs to the Special Issue Assessment and Management of Fishery Resources)

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15 pages, 334 KiB

Open AccessArticle

Possible Metal Burden of Potentially Toxic Elements in Rainbow Trout (Oncorhynchus mykiss) on Aquaculture Farm

by József Lehel, Melinda Plachy, Péter Palotás, András Bartha and Péter Budai

Fishes 2024, 9(7), 252; https://doi.org/10.3390/fishes9070252 - 1 Jul 2024

Abstract

Aquaculture products are important parts of human nutrition due to their healthy components; however, they may contain elements that are potentially toxic to consumers. The aim of the study was to detect the concentration of As, Cd, Hg, and Pb by inductively coupled [...] Read more.

Aquaculture products are important parts of human nutrition due to their healthy components; however, they may contain elements that are potentially toxic to consumers. The aim of the study was to detect the concentration of As, Cd, Hg, and Pb by inductively coupled plasma optical emission spectroscopy in rainbow trout (Oncorhynchus mykiss) originated from an aquaculture farm in Italy. The amount of As was 1.65 ± 0.49 mg/kg; however, the total As cannot be evaluated due to the absence of official regulation. The calculated EDI and THQ for the inorganic As content were below the reference values. The level of Cd was higher than the regulated limit in 30% of the samples; however, its EDI and THQ were below the recommended limit. The concentration of Hg was below the regulated maximum limit in all the samples. The detected amount of Pb was above the maximum limit in 10% of the samples; however, EDI and THQ were below the reference dose and recommended value. Despite higher concentrations of Cd and Pb than the official regulated limit, HI was below 1 for adults; thus, the consumption of the investigated rainbow trout is safe, but it was above the official regulated limit for children, resulting in a slight risk, particularly during long-term intake. Full article

(This article belongs to the Special Issue Risk Assessment of Pollutant Residues in Aquatic Products and Aquaculture Environments)

8 pages, 1704 KiB

Open AccessArticle

Acoustic Characteristics of Spawning Biological Sounds of Brown Croaker (Miichthys miiuy)

by Hansoo Kim, Young Geul Yoon, Sungho Cho, Sunhyo Kim, Mira Kim and Donhyug Kang

Fishes 2024, 9(7), 251; https://doi.org/10.3390/fishes9070251 - 29 Jun 2024

Abstract

Marine organisms make sounds for various reasons, including spawning and avoidance, which are species-specific. Traditionally, Korean fishermen in the northwest Pacific Ocean have listened for spawning sounds to locate spawning grounds of Brown croaker (Miichthys miiuy), one of the important commercial [...] Read more.

Marine organisms make sounds for various reasons, including spawning and avoidance, which are species-specific. Traditionally, Korean fishermen in the northwest Pacific Ocean have listened for spawning sounds to locate spawning grounds of Brown croaker (Miichthys miiuy), one of the important commercial fish species. We measured the spawning sounds recorded in October, the croakers’ spawning season (August to October). The mean signal duration with standard deviation was 0.184 ± 0.027 s, and the mean pulse interval was 0.022 ± 0.001 s. The zero-to-peak mean sound pressure level was 165.2 ± 0.7 dB. The peak frequency was 459.2 ± 93.8 Hz, with maximum and minimum frequencies observed at 863.0 ± 225.9 Hz and 231.2 ± 67.9 Hz. The spawning sounds occurred around sunset (16:00–21:00, local time) and only when the water temperature was above 22 °C. These findings help interpret the environmental ecology and manage the fishery resources of the Brown croaker spawning grounds. Full article

(This article belongs to the Special Issue Applications of Passive Acoustics to Fisheries)

18 pages, 1199 KiB

Open AccessArticle

Exploring Growth Patterns of Maurolicus muelleri across Three Northeast Atlantic Regions

by Paula Alvarez, Naroa Aldanondo, Alina M. Wieczorek, Thibault Cariou, Guillermo Boyra, Eduardo Grimaldo, Webjørn Melle and Thor Klevjer

Fishes 2024, 9(7), 250; https://doi.org/10.3390/fishes9070250 - 26 Jun 2024

Abstract

Abstract: Maurolicus muelleri is an important component of mesopelagic ecosystems; nevertheless, we possess only limited knowledge about its biological features. We collected samples of M. muelleri from six scientific surveys between 2019 and 2021 in three geographical areas in the Northeast Atlantic [...] Read more.

Abstract: Maurolicus muelleri is an important component of mesopelagic ecosystems; nevertheless, we possess only limited knowledge about its biological features. We collected samples of M. muelleri from six scientific surveys between 2019 and 2021 in three geographical areas in the Northeast Atlantic waters (from South to North): the Bay of Biscay, the Celtic Sea, and the Norwegian Sea. Geographical variations in otolith growth, fish age, length, weight, and condition, as well as length–weight relationships and von Bertalanffy growth models (VBGMs), were investigated. Length-weight relationships revealed differences associated with the fish’s origin, paralleling the annual and daily otolith growth. VBGM parameters increased progressively northwards, in accordance with Bergmann’s rules. Fish length was positively related to the otolith radio, and Lee’s phenomenon was undetected. The impact of environmental variables, such as temperature and food availability, is debated, with these considered potential drivers of this variability. Populations may belong to separated units, either genetically or morphologically, representing differences in biological parameters as a signal of geographical divergence. Full article

(This article belongs to the Section Biology and Ecology)

12 pages, 1771 KiB

Open AccessArticle

Effect of Replacing Fishmeal with Algal Meal on Growth Parameters and Meat Composition in Rainbow Trout (Oncorhynchus mykiss W.)

by Katya Velichkova, Ivaylo Sirakov, Stefka Stoyanova, Apostol Simitchiev, David Yovchev and Kamelia Stamatova-Yovcheva

Fishes 2024, 9(7), 249; https://doi.org/10.3390/fishes9070249 - 26 Jun 2024

Abstract

Aquafarms should reduce the use of fishmeal and fish oil in nutritional feed. One such accessible and relatively inexpensive food component that could successfully meet the challenge posed by aquaculture is algae. The objective of the present study was to evaluate the algae [...] Read more.

Aquafarms should reduce the use of fishmeal and fish oil in nutritional feed. One such accessible and relatively inexpensive food component that could successfully meet the challenge posed by aquaculture is algae. The objective of the present study was to evaluate the algae meal inclusion of Chlorella and Spirulina sp. in a diet for rainbow trout, evaluating its effects on fish growth, histological parameters and fillet quality. Experiments were carried out to replace 50% and 100% of fishmeal with Spirulina sp. and Chlorella vulgaris in feed for rainbow trout (Oncorhynchus mykiss W.) cultured in a recirculation system. At the end of the experimental period, the highest mean live weight was measured in rainbow trout fed a feed containing 50% algal meal in the feed. The absorptive vacuolization of cells was increased the most and lamina propria was average thickened when fed 50% algae diets. Fat droplets in the hepatocytes were larger in the 50% algae meal fed group, and their nuclei were replaced in the peripheral zone of the cells. Substitution of fishmeal with 50% algal meal in fish feed resulted in a 36.44% reduction in the lipid content of rainbow trout fillets compared to control fish. Full article

(This article belongs to the Special Issue Algae as Aquafeed Ingredients and Additives for Sustainable Aquaculture)

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12 pages, 1330 KiB

Open AccessArticle

Effects of Acute Temperature Stress on the Expression of Related Genes in the Brain of Opsariichthys bidens

by Qianhui Li, Luomei **ong, Yechen Zhu, Anrui Zheng and Shanjian Zheng

Fishes 2024, 9(7), 248; https://doi.org/10.3390/fishes9070248 - 25 Jun 2024

Abstract

Opsariichthys bidens (O. bidens) is a fish species native to China and sensitive to temperature changes. In this study, the effects of acute temperature stress on brain gene expression in O. bidens were investigated by sampling brain tissues from specimens [...] Read more.

Opsariichthys bidens (O. bidens) is a fish species native to China and sensitive to temperature changes. In this study, the effects of acute temperature stress on brain gene expression in O. bidens were investigated by sampling brain tissues from specimens exposed to three different temperatures (15 °C, 25 °C, and 35 °C) for varying durations of 2 h, 4 h, 6 h, and 8 h. The study focused on analyzing the expression patterns of key genes implicated in neural function and stress response, including brain-derived neurotrophic factor (BDNF), c-FOS, heat shock proteins (HSP70, HSP90), endoplasmic reticulum stress markers (IRE1, GRP78), oxidative stress enzymes (CAT, SOD), and apoptotic regulators (caspase3, Bax). The findings revealed that upon exposure to acute heat stress, the expression levels of the aforementioned genes in the brain of O. bidens were up-regulated within 2 h, peaking at the 4-h mark. Conversely, following acute cold stress, the expression of c-FOS, BDNF, HSP70, HSP90, SOD, and CAT genes increased significantly after 4 h, while caspase3 expression was notably elevated at the 6-h mark, with no significant impact observed on Bax, IRE1, or GRP78 gene expression levels. The study suggested that the brain of O. bidens responds to high temperatures through mechanisms involving neural activation, heat shock proteins, endoplasmic reticulum stress, oxidative stress, and apoptosis. Similarly, adaptation to low temperatures by O. bidens’ brain was associated with neural activation, regulation of heat shock proteins, oxidative stress responses, and apoptotic processes. Overall, this research aimed to elucidate the impact of temperature stress on brain physiology and the adaptive mechanisms of O. bidens at the genetic level, providing a foundational understanding of its temperature adaptation strategies. Full article

(This article belongs to the Section Biology and Ecology)

14 pages, 964 KiB

Open AccessArticle

Feeding Behaviour of Seven Icefish Species (Channichthyidae) in the Ross Sea, Antarctica

by Erica Carlig, Davide Di Blasi, Laura Ghigliotti, Andreas Scalas, Andrew L. Stewart and Michela Mortara

Fishes 2024, 9(7), 247; https://doi.org/10.3390/fishes9070247 - 25 Jun 2024

Abstract

The Channichthyidae, a monophyletic fish group belonging to the suborder Notothenioidei, are uniquely adapted to the polar environment. However, while their physiology has been extensively studied, studies on their ecology are relatively rare. Here, we investigated the trophic ecology of seven icefish species [...] Read more.

The Channichthyidae, a monophyletic fish group belonging to the suborder Notothenioidei, are uniquely adapted to the polar environment. However, while their physiology has been extensively studied, studies on their ecology are relatively rare. Here, we investigated the trophic ecology of seven icefish species (Chaenodraco wilsoni, Chionobathyscus dewitti, Chionodraco hamatus, Dacodraco hunteri, Neopagetopis ionah, Pagetodes antarcticus and Pagetopsis macropterus) by using the traditional morphometric approach to assess the relationship between form and feeding function. The suction index (SI), the mechanical advantage in jaw closing (MA) and nine morphological traits related to feeding structures have been analysed. Icefish species are characterised by non-protractible, elongate jaws and a wide gape; such morphological features influence the low values of both MA and SI, supporting their ram-feeding habit. The ecomorphological differences among species resulted mainly determined by the anatomical structures related to SI. Such differences do not seem to be determined primarily by the type of prey, as is the case in other taxonomic groups of Notothenioidei, but rather by phylogenetic proximity. A 3D animation was developed to visualise the different feeding modes of two icefish species (C. hamatus and P. macropterus) which are characterised by different approaches to prey. Full article

(This article belongs to the Special Issue Recent Advances in Foraging Behavior of Fish)

14 pages, 1617 KiB

Open AccessArticle

Trends and Environmental Drivers of Marine Fish Landings in Cuba’s Most Productive Shelf Area

by Yunier Olivera-Espinosa, Yandy Rodríguez-Cueto, Fabián Pina-Amargós, Francisco Arreguín-Sánchez, Manuel J. Zetina-Rejón, Kendra Karr and Pablo del Monte-Luna

Fishes 2024, 9(7), 246; https://doi.org/10.3390/fishes9070246 - 23 Jun 2024

Abstract

Marine finfish landings in Cuba have decreased during the last 30 years. However, in Cuba’s most productive fishing region, certain species, including rays, herrings, and snappers, have had increased landings over the past decade. Despite these anomalies, no comprehensive analysis of the interactions [...] Read more.

Marine finfish landings in Cuba have decreased during the last 30 years. However, in Cuba’s most productive fishing region, certain species, including rays, herrings, and snappers, have had increased landings over the past decade. Despite these anomalies, no comprehensive analysis of the interactions among multispecies landing dynamics, environmental factors, and fishing efforts has been carried out. This study estimates the dynamics of multispecies finfish landings between 1981 and 2017 on the southeastern coast of Cuba. A log-normal generalized additive model (GAM) was fit to evaluate the effects of various environmental and effort-related variables on the total landings. During the period analyzed, the finfish landings and fishing effort decreased by 46% and over 80%, respectively. Despite concerns about overfishing, landings per unit of effort (LPUE) increased by 2.8 times. The total fish landings were significantly related to changes in the fishing effort, coastal vegetation, rainfall, chlorophyll-a, and the Southern Oscillation Index (SOI). This study highlights the changing relationship between the landings and fishing effort, suggesting that LPUE may not accurately reflect true stock abundance. The findings of this study will assist in integrating the dynamics of finfish species, ecosystem status, and management actions for Cuba’s most productive fishing zone. Full article

(This article belongs to the Special Issue Assessment and Management of Fishery Resources)

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13 pages, 482 KiB

Open AccessArticle

Effects of Yacon (Smallanthus sonchifolius) Juice Byproduct Administered Using Different Feeding Methods on the Growth Performance, Digestive Enzyme Activity, Antioxidant Status, and Disease Resistance against Streptococcus iniae of Juvenile Black Rockfish (Sebastes schlegelii)

by Hwa Yong Oh, Tae Hoon Lee, Gyu ** Lee, Seo Young Park, Ki-Tae Kim and Hee Sung Kim

Fishes 2024, 9(7), 245; https://doi.org/10.3390/fishes9070245 - 22 Jun 2024

Abstract

This study was designed to evaluate the effects of yacon (Smallanthus sonchifolius) juice byproduct (YJB) on the growth performance, digestive and antioxidant enzyme activities, and disease resistance against Streptococcus iniae of juvenile black rockfish (Sebastes schlegelii) based on different [...] Read more.

This study was designed to evaluate the effects of yacon (Smallanthus sonchifolius) juice byproduct (YJB) on the growth performance, digestive and antioxidant enzyme activities, and disease resistance against Streptococcus iniae of juvenile black rockfish (Sebastes schlegelii) based on different feeding schedules. Four different YJB feeding strategies were evaluated: feeding the fish a basal diet continuously (control, T0), feeding them YJB (2.5 g/kg) continuously (T1), feeding them YJB for 1 day and the basal diet the next day (T2), and feeding them YJB for 1 day and the basal diet for the following 2 days (T3). No difference in survival among the treatments was found after the 8-week feeding trial (p > 0.05). However, the T1 and T2 groups exhibited significant enhancements in final body weight, weight gain, and specific growth rate compared with the T0 and T3 groups. Furthermore, the T1 and T2 groups showed a significant improvement in feed consumption, feed efficiency, and protein efficiency ratio compared with the T0 and T3 groups. No significant differences in the condition factor or viscerosomatic and hepatosomatic indices were observed among all the groups. Intestinal amylase, trypsin, and lipase activity was significantly (p < 0.05) higher in the T1 and T2 groups than in the T0 and T3 groups. Lysozyme, superoxide dismutase, and catalase activity along with glutathione peroxidase content were significantly (p < 0.05) higher under all YJB feeding regimens than those under the control treatment. The survival rates in all the YJB treatment groups after the S. iniae challenge were significantly (p < 0.05) enhanced. In conclusion, we recommend offering YJB at day-to-day intervals to improve growth performance, digestive enzyme activity, antioxidant status, and disease resistance against S. iniae. Full article

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

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12 pages, 2242 KiB

Open AccessArticle

Effects of Different Stocking Densities on the Growth, Antioxidant Status, and Intestinal Bacterial Communities of Carp in the Rice–Fish Co-Culture System

by Weixu Diao, Rui Jia, Yiran Hou, Jianyou Gong, Liqiang Zhang, Bing Li and Jian Zhu

Fishes 2024, 9(7), 244; https://doi.org/10.3390/fishes9070244 - 21 Jun 2024

Abstract

Common carp (Cyprinus carpio) is a freshwater fish commonly farmed in rice fields, yet there were few studies on the intestinal functions and microbial community structure of common carp in the rice–carp co-culture system. Therefore, this study aimed to explore the [...] Read more.

Common carp (Cyprinus carpio) is a freshwater fish commonly farmed in rice fields, yet there were few studies on the intestinal functions and microbial community structure of common carp in the rice–carp co-culture system. Therefore, this study aimed to explore the effects of different stocking densities on the growth, antioxidant status, and intestinal bacterial composition of common carp in this system. This study was divided into three different stocking densities, including low density (LD, 10 fish, 52.9 g/m²), medium density (MD, 20 fish, 105.8 g/m²), and high density (HD, 30 fish, 158.7 g/m²), with a culturing period of 60 days. The results indicated that HD treatment inhibited the growth of common carp, as evidenced by the reduced final weight, WG, and SGR. In serum, the TG content in the HD group and the Cor content in the MD group were significantly increased. Meanwhile, HD treatment induced oxidative stress, manifesting specifically as increased SOD and CAT activities in the intestine or serum while reducing Gpx, GSH, and T-AOC in the serum. The 16S rDNA analysis indicated that the Simpson and Shannon indices of intestinal microbiota in the HD group were significantly higher than those in the LD group. At the phylum level, Proteobacteria, Cyanobacteria, and Firmicutes were dominant microbial communities in two groups. In addition, there was a significant difference between the two groups in the abundances of Actinobacterota and Bifidobacterium. Based on growth performances, biochemical indicators, and microbial diversity in rice–carp co-culture, low density (52.9 g/m²) may be more suitable in the rice–carp co-culture systems. In summary, this study contributes to a better understanding of common carp response to different stocking densities in the rice–carp co-culture system. Full article

(This article belongs to the Special Issue Fish Diseases Diagnostics and Prevention in Aquaculture)

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34 pages, 27775 KiB

Open AccessReview

Fishes in Marine Caves

by Marcelo Kovačić, Vasilis Gerovasileiou and Robert A. Patzner

Fishes 2024, 9(6), 243; https://doi.org/10.3390/fishes9060243 - 20 Jun 2024

Abstract

Fishes in marine caves have attracted limited attention by the scientific community in comparison to subterranean fishes which have lost eyes and pigmentation. They constitute a largely unexplored component of marine fish diversity, except for the relatively well-studied marine caves of the Mediterranean [...] Read more.

Fishes in marine caves have attracted limited attention by the scientific community in comparison to subterranean fishes which have lost eyes and pigmentation. They constitute a largely unexplored component of marine fish diversity, except for the relatively well-studied marine caves of the Mediterranean Sea. These habitats are characterized by steep environmental gradients of decreasing light and decreasing water exchange. The fishes recorded so far in marine caves are not exclusive residents of this habitat and they are also present at least in the other mesolithial habitats. In the Mediterranean marine caves, 132 fishes have been recorded to date, representing about 17% of the total Mediterranean fish species richness. Most of these species are reported from the anterior cave zones where some light still exists, while a smaller number of species are known from the totally dark zones. Among them, 27.3% are accidental visitors, 53.8% are the regular mesolithial visitors and switchers between mesolithion and open water, 5.3% are permanent residents of the mesolithion, but also occur in other habitats, and 13.6% are exclusive permanent residents of mesolithion. Some mesolithial exclusive permanent residents recorded in marine caves share similar morphology, probably as adaptations to these habitats. Full article

(This article belongs to the Special Issue Behavior, Ecology and Evolution of Subterranean Fish)

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21 pages, 5041 KiB

Open AccessArticle

DDEYOLOv9: Network for Detecting and Counting Abnormal Fish Behaviors in Complex Water Environments

by Yinjia Li, Zeyuan Hu, Yixi Zhang, Jihang Liu, Wan Tu and Hong Yu

Fishes 2024, 9(6), 242; https://doi.org/10.3390/fishes9060242 - 20 Jun 2024

Abstract

Accurately detecting and counting abnormal fish behaviors in aquaculture is essential. Timely detection allows farmers to take swift action to protect fish health and prevent economic losses. This paper proposes an enhanced high-precision detection algorithm based on YOLOv9, named DDEYOLOv9, to facilitate the [...] Read more.

Accurately detecting and counting abnormal fish behaviors in aquaculture is essential. Timely detection allows farmers to take swift action to protect fish health and prevent economic losses. This paper proposes an enhanced high-precision detection algorithm based on YOLOv9, named DDEYOLOv9, to facilitate the detection and counting of abnormal fish behavior in industrial aquaculture environments. To address the lack of publicly available datasets on abnormal behavior in fish, we created the “Abnormal Behavior Dataset of Takifugu rubripes”, which includes five categories of fish behaviors. The detection algorithm was further enhanced in several key aspects. Firstly, the DRNELAN4 feature extraction module was introduced to replace the original RepNCSPELAN4 module. This change improves the model’s detection accuracy for high-density and occluded fish in complex water environments while reducing the computational cost. Secondly, the proposed DCNv4-Dyhead detection head enhances the model’s multi-scale feature learning capability, effectively recognizes various abnormal fish behaviors, and improves the computational speed. Lastly, to address the issue of sample imbalance in the abnormal fish behavior dataset, we propose EMA-SlideLoss, which enhances the model’s focus on hard samples, thereby improving the model’s robustness. The experimental results demonstrate that the DDEYOLOv9 model achieves high

P r e c i s i o n

,

R e c a l l

, and

m e a n A v e r a g e P r e c i s i o n

(

m A P

) on the “Abnormal Behavior Dataset of Takifugu rubripes”, with values of 91.7%, 90.4%, and 94.1%, respectively. Compared to the YOLOv9 model, these metrics are improved by 5.4%, 5.5%, and 5.4%, respectively. The model also achieves a running speed of 119 frames per second (

F P S

), which is 45

F P S

faster than YOLOv9. Experimental results show that the DDEYOLOv9 algorithm can accurately and efficiently identify and quantify abnormal fish behaviors in specific complex environments. Full article

(This article belongs to the Special Issue AI and Fisheries)

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15 pages, 4887 KiB

Open AccessArticle

Exploring the Internal Defense System of Cerastoderma glaucum (Bruguière, 1789) Exposed to Pristine Microplastics: The Sentinel Role of Haemocytes as Biomarkers

by Alessio Alesci, Davide Di Paola, Sebastian Marino, Federica De Gaetano, Marco Albano, Silvana Morgante, Gabriele Rigano, Letterio Giuffrè, Magdalena Kotanska, Nunziacarla Spanò and Eugenia Rita Lauriano

Fishes 2024, 9(6), 241; https://doi.org/10.3390/fishes9060241 - 20 Jun 2024

Abstract

The ubiquitous presence of microplastics (MPs) in the environment is a major concern for the conservation of biodiversity. Numerous studies show the detrimental effects of MPs on marine species, especially because of their small size and their capacity to absorb organic contaminants from [...] Read more.

The ubiquitous presence of microplastics (MPs) in the environment is a major concern for the conservation of biodiversity. Numerous studies show the detrimental effects of MPs on marine species, especially because of their small size and their capacity to absorb organic contaminants from their surroundings. The bivalve mollusk Cerastoderma glaucum (Bruguière, 1789), because of its wide geographic distribution and immobile feeding habits, can be used as a sentinel and bioindicator species. By examining the presence, localization, and co-localization of Toll-like receptor 2 (TLR2) and inducible nitric oxide synthetase (iNOS), this study aims to evaluate the response of the internal defense system of C. glaucum to pristine MPs through the employment of confocal microscopy and bioinformatics techniques. The results show haemocytes immunoreactive to the antibodies tested; in particular, a higher number of TLR2-positive haemocytes can be observed in the group exposed to pristine MPs. These findings suggest that haemocytes can play a key biomarker role as sentinels to environmental pollutants. Furthermore, bioinformatics analyses on the antibodies tested confirmed an evolutionary conservation of these molecules. These data highlight the critical role of phagocytosis in identifying ecosystem damage and are helpful in develo** biosensors with less negative effects on the environments in which they are applied. Full article

(This article belongs to the Section Aquatic Invertebrates)

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12 pages, 896 KiB

Open AccessArticle

Growth, Metabolic, Hepatic and Redox Parameters, Digestive Enzymes and Innate Immunity in Mugil liza Fed a Citral-Supplemented Diet

by Natacha C. Mori, Bruna T. Michelotti, Caio C. F. Magnotti, Caroline A. Bressan, Letícia B. Bianchin, Fernando J. Sutili, Ana Paula G. Almeida, Luiz C. Kreutz, Maria A. Pavanato, Vinicius R. Cerqueira, Silvio T. da Costa, Bernardo Baldisserotto and Berta M. Heinzmann

Fishes 2024, 9(6), 240; https://doi.org/10.3390/fishes9060240 - 20 Jun 2024

Abstract

Mugil liza juveniles (6.69 ± 0.06 g) were subjected to dietary citral (0-control, 0.5, 1.0 and 2.0 mL per kg feed) for 45 days, and its possible effects on zootechnical and metabolic parameters, digestive enzymes, innate immunity, oxidative status and liver damage were [...] Read more.

Mugil liza juveniles (6.69 ± 0.06 g) were subjected to dietary citral (0-control, 0.5, 1.0 and 2.0 mL per kg feed) for 45 days, and its possible effects on zootechnical and metabolic parameters, digestive enzymes, innate immunity, oxidative status and liver damage were evaluated. At the end of the experiment, fish fed 2.0 mL citral per kg feed showed a greater weight gain and protein retention efficiency, as well as enhanced activities of pepsin (stomach) and amylase (intestine) compared with control fish. Citral supplementation decreased liver lipoperoxidation and increased the activities of glutathione peroxidase, glutathione-S-transferase and superoxide dismutase in the gills, liver and brain. The highest level of citral inclusion augmented non-protein thiol content in the brain and gills. Myeloperoxidase activity was lower in fish offered 1.0 and 2.0 mL citral per kg feed. Dietary citral did not influence the plasma levels of aspartate aminotransferase and alanine aminotransferase or the hepatic histology. As it improved growth, the activity of digestive enzymes and general health, dietary citral may be recommended for M. liza at 2.0 mL per kg feed. Full article

(This article belongs to the Special Issue Advances in Sustainable Aquaculture Production Systems)

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16 pages, 3410 KiB

Open AccessArticle

Transcriptome Analysis of Juvenile Black Rockfish Sebastes schlegelii under Air Exposure Stress

by Changlin Liu, Zheng Zhang, Shouyong Wei, Wenjie **ao, Chao Zhao, Yue Wang and Liguo Yang

Fishes 2024, 9(6), 239; https://doi.org/10.3390/fishes9060239 - 19 Jun 2024

Abstract

The study aimed to uncover the molecular response of juvenile Sebastes schlegelii to air exposure stress by identifying differentially expressed genes (DEGs) that may underlie their anti-stress mechanisms. Juvenile Sebastes schlegelii were subjected to varying durations of air exposure stress. The total RNA [...] Read more.

The study aimed to uncover the molecular response of juvenile Sebastes schlegelii to air exposure stress by identifying differentially expressed genes (DEGs) that may underlie their anti-stress mechanisms. Juvenile Sebastes schlegelii were subjected to varying durations of air exposure stress. The total RNA was extracted from whole tissues and sequenced using the Illumina NovaSeq 6000 platform. The transcriptome data were analyzed to identify DEGs through pairwise comparisons across a control group and two experimental groups exposed to air for 40 s and 2 min 30 s, respectively. The comparative DEG analysis revealed a significant number of transcripts responding to air exposure stress. Specifically, 5173 DEGs were identified in the 40 s exposure group (BS) compared to the control (BC), 6742 DEGs in the 2 min 30 s exposure group (BD) compared to the control (BC), and 2653 DEGs when comparing the BD to the BS group. Notably, Gene Ontology (GO) analysis showed an enrichment of DEGs associated with peptidase activity and extracellular regions, suggesting a role in the organism’s stress response. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis pointed to the involvement of metabolic pathways, which are crucial for energy management under stress. The upregulation of protein digestion and absorption pathways may indicate a physiological adaptation to nutrient scarcity during stress. Additionally, the identification of antibiotic biosynthesis pathways implies a potential role in combating stress-induced infections or damage. The identified DEGs and enriched pathways provide insights into the complex anti-stress response mechanisms in juvenile Sebastes schlegelii. The enrichment of peptidase activity and extracellular region-related genes may reflect the initiation of tissue repair and immune response following air exposure. The connection between protein digestion and absorption pathways and anti-stress capabilities could be interpreted as a metabolic readjustment to prioritize energy-efficient processes and nutrient assimilation during stress. The role of antibiotic biosynthesis pathways suggests a defensive mechanism against oxidative stress or microbial invasion that might occur with air exposure. Full article

(This article belongs to the Special Issue Physiological Response Mechanism of Aquatic Animals to Stress)

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20 pages, 3562 KiB

Open AccessArticle

Preliminary Insights on the Habitat Use and Vertical Movements of the Pelagic Stingray (Pteroplatytrygon violacea) in the Western Mediterranean Sea

by François Poisson, Jim R. Ellis and Sophy R. McCully Phillips

Fishes 2024, 9(6), 238; https://doi.org/10.3390/fishes9060238 - 18 Jun 2024

Abstract

Pelagic stingray (Pteroplatytrygon violacea) is the only species of stingray (Dasyatidae) that utilizes both pelagic and demersal habitats. It is the main bycatch species in pelagic longline fisheries targeting bluefin tuna (Thunnus thynnus) in the Gulf of Lions. In [...] Read more.

Pelagic stingray (Pteroplatytrygon violacea) is the only species of stingray (Dasyatidae) that utilizes both pelagic and demersal habitats. It is the main bycatch species in pelagic longline fisheries targeting bluefin tuna (Thunnus thynnus) in the Gulf of Lions. In the Mediterranean Sea, their stock structure, behavioural ecology and movements are unknown. For the first time in the Mediterranean, 17 individuals (39–60 cm disc width) were tagged with pop-up satellite archival transmitting tags using a novel method of tag attachment to investigate horizontal and vertical movements. The tags were attached for between two and 60 days. Between the months of July and October, pelagic stingray occupied a temperature range of 12.5–26.6 °C, and a depth range extending from the surface to 480 m. Monthly trends in catch-per-unit-effort (CPUE) of pelagic stingray peaked in August and decreased by late autumn. Pelagic stingray may aggregate on the continental shelf during summer and move southwards in early autumn, and this movement pattern is considered in relation to the reproductive cycle and overwintering. At-vessel mortality was low, but there was varying evidence of post-release mortality, indicating the need for further work. Future work and options for bycatch mitigation are also discussed. Full article

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