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Volume 6, September

Fishes, Volume 6, Issue 4 (December 2021) – 9 articles

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Article
Diets and Stable Isotope Signatures of Native and Nonnative Leucisid Fishes Advances Our Understanding of the Yellowstone Lake Food Web
by , and
Fishes 2021, 6(4), 51; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040051 (registering DOI) - 20 Oct 2021
Abstract
(1) Many forage fishes, such as Leucisids (minnows) have depauperate studies on diet composition or stable isotope signatures, as these fishes are often only viewed as food for higher trophic levels. The need exists to understand and document the diet and stable isotope [...] Read more.
(1) Many forage fishes, such as Leucisids (minnows) have depauperate studies on diet composition or stable isotope signatures, as these fishes are often only viewed as food for higher trophic levels. The need exists to understand and document the diet and stable isotope signatures of Leucisids (redside shiner, longnose dace, lake chub) in relation to the community ecology and food-web dynamics in Yellowstone Lake, especially given an invasive piscivore introduction and potential future effects of climate change on the Yellowstone Lake ecosystem. (2) Diet data collected during summer of 2020 were analyzed by species using proportion by number, frequency of occurrence, and mean proportion by weight, and diet overlap was compared using Schoener’s index (D). Stable isotope (δ15N and δ13C) values were estimated by collecting tissue during the summer of 2020 by species, and isotopic overlap was compared using 40% Bayesian ellipses. (3) Nonnative redside shiners and lake chub had similar diets, and native longnose dace diet differed from the nonnative Leucisids. Diet overlap was also higher between the nonnative Leucisids, and insignificant when comparing native and nonnative Leucisids. No evidence existed to suggest a difference in δ15N signatures among the species. Longnose dace had a mean δ13C signature of −15.65, indicating an decreased reliance on pelagic prey compared to nonnative Leucisids. Nonnative redside shiners and lake chub shared 95% of isotopic niche space, but stable isotope overlap was <25% for comparisons between native longnose dace and the nonnative Leucisids. (4) This study established the diet composition and stable isotope signatures of Leusicids residing in Yellowstone Lake, thus expanding our knowledge of Leucisid feeding patterns and ecology in relation to the native and nonnative species in the ecosystem. We also expand upon our knowledge of Leucisids in North America. Additionally, quantifying minnow diets can provide a baseline for understanding food web response to invasive suppression management actions. Full article
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Article
Nondestructive Monitoring of Soft Bottom Fish and Habitats Using a Standardized, Remote and Unbaited 360° Video Sampling Method
Fishes 2021, 6(4), 50; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040050 (registering DOI) - 15 Oct 2021
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Abstract
Lagoon soft-bottoms are key habitats within coral reef seascapes. Coral reef fish use these habitats as nurseries, feeding grounds and transit areas. At present, most soft-bottom sampling methods are destructive (trawling, longlining, hook and line). We developed a remote, unbaited 360° video sampling [...] Read more.
Lagoon soft-bottoms are key habitats within coral reef seascapes. Coral reef fish use these habitats as nurseries, feeding grounds and transit areas. At present, most soft-bottom sampling methods are destructive (trawling, longlining, hook and line). We developed a remote, unbaited 360° video sampling method (RUV360) to monitor fish species assemblages in soft bottoms. A low-cost, high-definition camera enclosed in a waterproof housing and fixed on a tripod was set on the sea floor in New Caledonia from a boat. Then, 534 videos were recorded to assess the efficiency of the RUV360. The technique was successful in sampling bare soft-bottoms, seagrass beds, macroalgae meadows and mixed soft-bottoms. It is easy to use and particularly efficient, i.e., 88% of the stations were sampled successfully. We observed 10,007 fish belonging to 172 species, including 45 species targeted by fishermen in New Caledonia, as well as many key species. The results are consistent with the known characteristics of the lagoon soft bottom fish assemblages of New Caledonia. We provide future users with general recommendations and reference plots to estimate the proportion of the theoretical total species richness sampled, according to the number of stations or the duration of the footage. Full article
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Article
Acanthocephalan Worms Mitigate the Harmful Impacts of Heavy Metal Pollution on Their Fish Hosts
Fishes 2021, 6(4), 49; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040049 - 14 Oct 2021
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Abstract
Toxic metal pollutants in aquatic environments and infestationwith intestinal helminths adversely affect the fish health, as well as fish consumers. Acanthocephalan worms in fish intestine have a high potential to absorb and bioaccumulate different heavy metals, especially toxic ones, from the intestine via [...] Read more.
Toxic metal pollutants in aquatic environments and infestationwith intestinal helminths adversely affect the fish health, as well as fish consumers. Acanthocephalan worms in fish intestine have a high potential to absorb and bioaccumulate different heavy metals, especially toxic ones, from the intestine via their tegument with greater efficiency than the fish intestinal wall. Herein, 47 specimens of the fish Siganusrivulatus were trapped in the Red Sea, Egypt, from a chronically polluted bay. All were intoxicatedwith Cd and Pb; 20 (42.5%) were uninfected with any intestinal worm, but the other 27 (57.5%) were infected only by the intestinal acanthocephalan Sclerocollum rubrimaris. The number of individual worms in a fish host (infrapopulation size) ranged from 32 to 236. As a reference group, 22 uncontaminated–uninfected specimens of S. rivulatus were trapped from a small unpolluted bay. Our results revealed that infection with acanthocephalans alleviatesthe harmful effectsof toxic metalson their fish hosts by: (1) lowering the elevated concentrations of both Cd and Pb in fish liver; (2) lowering the elevated levels of liver enzymes (ALT, AST, ALP, and GGT), glucose, triglycerides, and urea in fish blood serum; and (3) raising the declined levels of total protein and albumin in fish blood serum. All of these were dependent on S. rubrimaris infrapopulation size in fish intestine. Full article
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Article
Influence of Spatial Scale Selection of Environmental Factors on the Prediction of Distribution of Coilia nasus in Changjiang River Estuary
Fishes 2021, 6(4), 48; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040048 - 12 Oct 2021
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Abstract
An estuary region is a complex environment with a transition from fresh to brackish to salt water, and in which some environmental factors change dramatically over small ranges. Therefore, it is important to understand the impact of the selection of spatial scale on [...] Read more.
An estuary region is a complex environment with a transition from fresh to brackish to salt water, and in which some environmental factors change dramatically over small ranges. Therefore, it is important to understand the impact of the selection of spatial scale on the prediction of the distribution of estuarine species. As the largest estuary in China, the Changjiang River estuary is the spawning ground, feeding ground, and migration channel for many species. Based on Coilia nasus, an important economic fish species in the Changjiang River estuary, this study uses the two-stage generalized additive model (GAM) to investigate the potential differences in the response of species’ spatial distribution when environmental factors are assessed at different spatial scales (1′ × 1′, 2′ × 2′, 3′ × 3′, 4′ × 4′, 5′ × 5′). The results showed the following: (1) according to the analysis of the variance inflation factor (VIF), the values of all environmental factors were less than three and we found no correlation among the environmental variables selected. (2) The first stage GAM retained six variables, including year, month, latitude (Lat), water depth (Depth, m), bottom salinity (Sal, mg/L), and chemical oxygen demand (COD, mg/L). The second stage GAM retained four variables, including Year, Lat, pH, and chlorophyll a (Chl-a, μg/L). (3) The mean value of the Chla for the 3′×3′ spatial scale was significantly lower than that of the other spatial scales, and the mean value of Sal for the 5′×5′ spatial scale was higher than that of the other spatial scales. (4) In terms of the spatial distribution of abundance, the distribution patterns of C. nasus predicted by all scales were not very similar, and the distribution patterns predicted by the 5′ × 5′ scale, in the autumn of 2012, were significantly different from those at other scales. Therefore, the selection of spatiotemporal scales may affect predictions of the spatial distributions of species. We suggest that potential spatiotemporal scale effects should be evaluated in future studies. Full article
Article
Genetic Evaluation of Black Sea Bream (Acanthopagrus schlegelii) Stock Enhancement in the South China Sea Based on Microsatellite DNA Markers
Fishes 2021, 6(4), 47; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040047 - 11 Oct 2021
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Abstract
This is the first genetic evaluation of hatchery-based stock enhancement of black sea bream (Acanthopagrus schlegelii) in the South China Sea after a two-year monitoring period. In this study, microsatellite DNA markers were used to calculate the contribution rate and analyze [...] Read more.
This is the first genetic evaluation of hatchery-based stock enhancement of black sea bream (Acanthopagrus schlegelii) in the South China Sea after a two-year monitoring period. In this study, microsatellite DNA markers were used to calculate the contribution rate and analyze genetic changes before and after stock enhancement. Two out of one hundred and sixty nine individuals from three recaptured populations were assigned to broodstock with a contribution rate of 1.18%, revealing that the hatchery-released juvenile fish could survive in the natural environment and had a positive effect on population replenishment in wild black sea bream abundance. However, we found that the release population had the lowest genetic diversity and significant genetic differentiation from other populations. In addition, genetic diversity detected in the recaptured population was lower than that in the wild population, and their genetic differentiation reached a significant level. Our results suggested that releasing cultured black sea bream juveniles with low genetic quality might be genetically harmful for the maintenance of wild genotypes. Therefore, it is necessary to assess the genetic variation of the hatchery population before implementing a stock enhancement and establish a long-term evaluation for monitoring the genetic effect caused by releasing this fish species. Full article
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Article
Comparison of Metabolic Rates of Young of the Year Beluga (Huso huso), Sterlet (Acipenser ruthenus) and Bester Hybrid Reared in a Recirculating Aquaculture System
Fishes 2021, 6(4), 46; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040046 - 09 Oct 2021
Viewed by 258
Abstract
In the present study, oxygen consumption of two sturgeon species, beluga (Huso huso), sterlet (Acipenser ruthenus), and their hybrid reared in a recirculating aquaculture system were compared over body intervals from 54–107 g to determine the interspecific variation of [...] Read more.
In the present study, oxygen consumption of two sturgeon species, beluga (Huso huso), sterlet (Acipenser ruthenus), and their hybrid reared in a recirculating aquaculture system were compared over body intervals from 54–107 g to determine the interspecific variation of metabolic rate. Metabolic rates were measured using the intermittent-flow respirometry technique. Standard oxygen consumption rates (SMR, mg O2 h−1) of sterlet were 30% higher compared with beluga and 22% higher compared with bester hybrid. The routine metabolic rate (RMR, mg O2 h−1) averaged 1.58 ± 0.13 times the SMR for A. ruthenus, 1.59 ± 0.3 for H. huso, and 1.42 ± 0.15 for the hybrid bester. However, the study revealed no significant differences (p > 0.05) between mean values of SMR and RMR for beluga and bester hybrid. The scaling coefficient reflected a closed isometry for the hybrid (b = 0.97), while for the purebred species the coefficient of 0.8 suggests a reduction in oxygen consumption with increasing body mass. These findings may contribute to understanding the differences in growth performances and oxygen requirements of the studied species reared in intensive aquaculture system. Full article
Article
Aurantiochytrium sp. Meal Improved Body Fatty Acid Profile and Morphophysiology in Nile Tilapia Reared at Low Temperature
Fishes 2021, 6(4), 45; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040045 - 08 Oct 2021
Viewed by 245
Abstract
Aurantiochytrium sp. is a heterotrophic microorganism that produces docosahexaenoic acid (DHA), thus being considered as a possible replacement for fish oil in aquafeeds. We investigated the effect of Aurantiochytrium sp. meal (AM) dietary levels (0, 5, 10, 20, and 40 g kg−1 [...] Read more.
Aurantiochytrium sp. is a heterotrophic microorganism that produces docosahexaenoic acid (DHA), thus being considered as a possible replacement for fish oil in aquafeeds. We investigated the effect of Aurantiochytrium sp. meal (AM) dietary levels (0, 5, 10, 20, and 40 g kg−1) on Nile tilapia body and hepatopancreas fatty acid (FA) profile, body FA retention, somatic indices, and morphophysiological changes in the intestine and hepatopancreas, after feeding Nile tilapia juveniles (average initial weight 8.47 g) for 87 days at 22 °C. The 10AM diet was compared to a control diet containing cod liver oil (CLO), since their DHA concentration was similar. Within fish fed diets containing increasing levels of AM, there was a linear increase in n-3 FA content, especially DHA, which varied in the body (0.02 to 0.41 g 100 g−1) and hepatopancreas (0.15 to 1.05 g 100 g−1). The morphology of the intestines and hepatopancreas was positively affected in AM-fed fish. Fish fed 10AM showed less accumulation of n-3 FAs in the body and hepatopancreas when compared to fish fed CLO. Therefore, AM is an adequate substitute for fish oil in winter diets for Nile tilapia, with the supplementation of 40AM promoting the best results regarding intestine and hepatopancreas morphophysiology. Full article
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Article
Phylogeographic Structure of Freshwater Tor sp. in River Basins of Sabah, Malaysia
Fishes 2021, 6(4), 44; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040044 - 23 Sep 2021
Viewed by 354
Abstract
We characterized the genetic diversity, phylogeography, and demography of Tor sp. (Cyprinidae) from Sabah, Malaysian Borneo, by examining nucleotide variation in the D-loop region of the mtDNA. Sequence analysis of 18 populations (N = 173) yielded 35 unique mtDNA haplotypes with mean [...] Read more.
We characterized the genetic diversity, phylogeography, and demography of Tor sp. (Cyprinidae) from Sabah, Malaysian Borneo, by examining nucleotide variation in the D-loop region of the mtDNA. Sequence analysis of 18 populations (N = 173) yielded 35 unique mtDNA haplotypes with mean haplotype and nucleotide diversity of 0.833 and 0.023, respectively. Phylogenetic reconstructions using Bayesian, neighbor-joining, and maximum parsimony methods, as well as haplotype network, revealed four well-defined clades, namely, the eastern, central, northwestern, and southwestern clades, which corresponded to evolutionarily significant units (ESUs). These ESUs were estimated to have become separated since the late Miocene to Pliocene era (between 5 and 1 million years ago), with the central highlands of Sabah Crocker Trusmadi Range (CTR) constituting the main barrier to genetic exchange between clades. Analysis of molecular variance (AMOVA) and pairwise genetic differentiation showed significant population structuring (Φct = 0.575–1.000, p < 0.05). We further identified eight major groups of river systems harboring reproductively isolated Tor subpopulations. Neutrality statistics and Bayesian skyline plots (BSP) suggested constant population size over time for most Tor populations. Tor sp. in Sabah is comprised of four ESUs (eastern, central, northwestern, and southwestern ESUs), and that each ESU can be compartmentalized into 1–4 MUs. Due to isolation by distance, the highest number of MU occurs in the low-elevation drainages of Eastern Sabah, which is the largest in terms of land area. The evidence provided by this study supports the hypothesis that the four ESU represent genetically distinct subpopulations of Tor and highlight the urgent need for the in situ conservation of these subpopulations. Full article
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Article
The Snakeskin Gourami (Trichopodus pectoralis) Tends to Exhibit XX/XY Sex Determination
Fishes 2021, 6(4), 43; https://0-doi-org.brum.beds.ac.uk/10.3390/fishes6040043 - 23 Sep 2021
Cited by 1 | Viewed by 496
Abstract
The snakeskin gourami (Trichopodus pectoralis) has a high meat yield and is one of the top five aquaculture freshwater fishes in Thailand. The species is not externally sexually dimorphic, and its sex determination system is unknown. Understanding the sex determination system [...] Read more.
The snakeskin gourami (Trichopodus pectoralis) has a high meat yield and is one of the top five aquaculture freshwater fishes in Thailand. The species is not externally sexually dimorphic, and its sex determination system is unknown. Understanding the sex determination system of this species will contribute to its full-scale commercialization. In this study, a cytogenetic analysis did not reveal any between-sex differences in chromosomal patterns. However, we used genotyping-by-sequencing to identify 4 male-linked loci and 1 female-linked locus, indicating that the snakeskin gourami tends to exhibit an XX/XY sex determination system. However, we did not find any male-specific loci after filtering the loci for a ratio of 100:0 ratio of males:females. This suggests that the putative Y chromosome is young and that the sex determination region is cryptic. This approach provides solid information that can help identify the sex determination mechanism and potential sex determination regions in the snakeskin gourami, allowing further investigation of genetic improvements in the species. Full article
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