Small-sized Fish Research Articles

Swimming and hiding regardless of the habitat: prey fish do not choose between a native and a non-native macrophyte species as a refuge

The ability to respond to a predation threat may be the key factor influencing prey survival. Thus, small-sized fish may adapt to use macrophyte patches as refugia in ecosystems where they face predators. We evaluated the habitat choices of a small fish species (Serrapinnus notomelas) to determine whether these fish prefer native versus recently introduced submerged macrophyte stands in the context of predator avoidance. Specifically, we applied three predator cue treatments: no cue, chemical cue from a hungry predator and presence of a satiated predator. First, we empirically tested the theoretical assumption that the prey fish use vegetated habitats and that the presence of an actual predator has a stronger effect on the choice of habitat than simply a chemical cue. Then we tested the hypothesis that prey do not choose a habitat according to macrophyte species and whether this pattern changed as a result of increasing predation risk. We found that the prey fish preferred vegetated habitats; however, they did not appear to distinguish native from invasive macrophytes. Our results support the hypothesis that the physical structure of macrophytes is more important in determining habitat choice than the evolutionary relationship between the fish and the native macrophyte species.

The complete mitochondrial genome of Parabotia banarescui (Cypriniformes: Cobitidae)

Parabotia banarescui is a small-sized fish species of the family Cobitidae. In this study, we determined the complete mitochondrial genome of P. banarescui. The complete mitochondrial genome of P. banarescui was 16,590 bp in length with the overall nucleotide base composition of A (31.00%), T (25.35%), G (16.02%) and C (27.63%), as well as an AT content of 56.35%. Besides, it contained 2 rRNA genes, 13 protein-coding genes, 22 tRNA genes, a control region and an L-strand replication origin (OL).

The complete mitochondrial genome of Parabotia fasciata (Cypriniformes: Cobitidae)

Parabotia fasciata is a small-sized benthopelagic fish species in the family Cobitidae. In the present study, we reported the complete mitochondrial genome of P fasciata. The complete mitochondrial genome of P. fasciata was 16,590 bp in length, which contained 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, a control region, and an L-strand replication origin (OL). Besides, its overall nucleotide base composition of mitogenome was 31.28% for A, 25.83% for T, 15.72% for G and 27.17% for C, as well as an AT content of 57.11%.

The complete mitochondrial genome of Leptobotia taeniaps (Cypriniformes: Cobitidae)

Leptobotia taeniaps is a small-sized benthopelagic fish species in the famally Cobitidae. In the present study, the complete mitochondrial genome of L. taeniaps was determined. The complete mitochondrial genome of L. taeniaps was 16,592 bp in length, containing 2 rRNA genes, 22 tRNA genes, 13 protein-coding genes, a control region, and an L-strand replication origin (OL). Its overall nucleotide base composition of mitogenome was 31.08% for A, 15.95% for G, 24.98% for T and 27.99% for C, as well as an AT content of 56.06%.

Effects of mangrove structure on fish distribution patterns and predation risks

This study examined the effects of mangrove structure on fish distribution patterns and predation risks in southern Japan, utilizing field experiments in which artificial units mimicked mangrove root structure and canopy shade in a mangrove estuary. Fishes responded strongly to the different levels of root structure complexity but not to canopy shade, fish species richness and abundance being consistently higher in the units with roots than in those without roots, regardless of shade presence/absence. With increasing root density, fish abundance increased considerably, although with decreasing fish body size. A tethering experiment, employing the above units and the most abundant local fish Apogon amboinensis as representative of small fishes, revealed that the predation mortality rates of small fishes decrease with increasing root density. The results suggested that the sheltering effects provided by root structure against predators may be one of the most important factors determining the distribution patterns of mangrove-associated fishes, and at least partly explain the greater abundance of small-sized fishes in microhabitats with greater root densities.

Assessing the potential of a protected area for fish conservation in a neotropical wetland

Freshwater habitats are among the most impacted ecosystem on Earth. Consequently, reserves have been implemented in an attempt to reduce the threat to freshwater biodiversity. However, few studies have evaluated how effective these protected areas (PA) are for the conservation of freshwater organisms. In the present study, we compared species richness, community composition and density of small-bodied fishes between lagoons within an eight-year-old reserve (i.e. protected lagoons) with those outside the reserve (i.e. unprotected lagoons) in a river-floodplain system that is exposed to seasonal flooding. The unprotected lagoons have been submitted to a light fishing pressure mainly targeting small-sized fishes for sale as baits. Our results showed no differences between the lagoons inside the reserve with those outside in any of the community properties measured. However, we registered an overall tendency of abundance reduction among the species used as baits in unprotected lagoons. Considering the high degree of oversight in the PA and the low fishing pressure among unprotected lagoons, it is possible that the positive effects promoted by the reserve on fish assemblages are being exported towards unprotected lagoons and thus offsetting a portion of the anthropogenic impacts. We conclude that the protection provided by the reserve is very efficient in river-floodplain systems, because not only it protects the biota inside the reserve but also act as a source of propagules to unprotected areas during the rainy season when all the aquatic subsystems are connected by the flood.

Responses of epibenthic and nektonic macroinvertebrate communities to a gradient of fish size in ponds

Size relationships between fish and organisms from adjacent trophic levels are crucial for predicting the structure and dynamics of aquatic ecosystems. We compared macroinvertebrate communities along a fish-size gradient created by separate stocking of three age cohorts of common carp Cyprinus carpio in semi-natural ponds. The specific size range of fish (small, medium and large) corresponding to fish age in ponds was the factor most strongly associated with macroinvertebrate composition. The other significant habitat variables were dissolved oxygen concentration in the water and submerged vegetation abundance in the open-water zone. Among the most numerous taxa in the ponds, relative abundances of Hirudinea, Gastropoda, Odonata and Coleoptera were larger in the presence of small-sized than of larger-sized carp. However, fish size effect was not linear, in that macroinvertebrate assemblages were less similar between ponds containing medium- vs large-sized fish than between ponds with small- vs large-sized fish. The dissimilarity patterns were mainly determined by disparities in abundance of Corixidae, which unlike other taxa common in the ponds occurred in the greatest numbers in the presence of large-sized carp. Macroinvertebrate diversity was greatest in ponds with small-sized fish and was positively related to emergent macrophyte cover. Enhancement of emergent vegetation is recommended as the most effective management strategy to buffer adverse impacts of fish on macroinvertebrates. If fish are present in the system, assessment of the size structure of fish populations can be advantageous in unravelling the essential processes driving the variation in pond communities.

Melt-curve-multiplex-haplotype-specific-PCR, a valuable tool for biological studies: Application in congeneric species discrimination assay

The aim of the present study was the development of a genetic discrimination method named Melt-Curve-MHS-PCR (MC-MHS-PCR). In order to explore the advantages, limitations and designing aspects of this method, we have used the conventional (electrophoretic) MHS-PCR as a reference, and designed species-discrimination assays for three fishes of the genus Spicara: Spicara smaris, Spicara maena and Spicara flexuosa. These small-size fishes exhibit marked phenotypic diversity that hinders their discrimination. Partial 16S rRNA gene sequences were obtained from twelve Mediterranean Spicara individuals and were used for the designing of two primer-sets that were subsequently tested on Spicara specimens from six sampling locations of Eastern Mediterranean. All examined samples were correctly assigned by both conventional and melt-curve MHS-PCR, proving that the MC-MHS-PCR is as reliable and discriminatory as the MHS-PCR. Moreover, the MC-MHS-PCR is very rapid, easily implemented, straightforward, and minimizes the risk of sample mix-up and laboratory contamination. These features render the method suitable for large-scale discrimination tests, particularly for studies that include small number of species.

RESULTS TAXONOMIC DESIGNATION FISH REMAINS FROM EXCAVATIONS OF ARCHAEOLOGICAL BAIBEK SITE 2013

Iichthyological materials, represented in the article, had been received from field investigations in Neolithic Baibek settlement in 2013 year. In total we investigated 310 fragments of fish, 8 species identified representatives: stellate sturgeon ( Acipenser stellatus ), sterlet ( Acipenser ruthenus ), common carp ( Cyprinus carpio ), bream ( Abramis brama ), zander ( Sander lucioperca ), perch ( Perca fluviatilis ), pike ( Esox lucius ) and catfish ( Silurus glanis ). The results of reconstruction of size, weight and age of the fish is represented in the article. A significant percentage of small-sized fish (70.5%) may indicate lack of food resources in the settlement during the studied period, and species composition suggests year-round fishing , the most actively carried out in the spring and spring-summer period.

The complete mitochondrial genome sequence of Predatory carp Chanodichthys erythropterus (Cypriniformes: Cyprinidae)

Predatory carp Chanodichthys erythropterus is a small-sized economic cyprinid fish distributed in East Asia. We sequenced its complete mitochondrial genome by PCR-based method. The mitochondrial DNA is packaged in a compact 16,629 base pair (bp) circular molecule with A + T content of 56.1%. It contains 22 transfer RNA genes, 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and the non-coding control region (D-loop). All PCGs are initiated by ATG codons, except for COI, which uses GTG as its start codon. Of the 13 PCGs, 12 stop with TAA and TAG, while Cyt b uses incomplete termination codon T. All tRNAs possess the classic cloverleaf secondary structure except for tRNASer(AGN), which lacks the ‘‘DHU’’ stem.

The invasive submerged macrophyte Hydrilla verticillata as a foraging habitat for small-sized fish

Several species of aquatic macrophytes have invaded ecosystems outside their ranges, producing a variety of impacts on native biota. In this study, we tested the role of the invasive macrophyte Hydrilla verticillata as a foraging habitat for small fish species. To achieve this goal, we assessed the feeding activity and diet composition of fish captured in patches of the invasive H. verticillata and of a similar native macrophyte (Egeria najas). Feeding activity did not differ significantly between H. verticillata and E. najas, indicating that foraging activity was not affected. However, differences in diet composition were significant in three out of five fish species and marginally significant in one species, suggesting that the invasive and native macrophytes provide different types of food resources for fish. Thus, although H. verticillata does not affect the foraging activity, it has the potential to affect the assemblages of small-sized fish through changes in the proportions of food resources.

Population correlates of circulating mercury levels in Korean adults: the Korea National Health and Nutrition Examination Survey IV.

BackgroundPrior studies focused on bioaccumulation of mercury (Hg) and on large, long-lived fish species as the major environmental source of Hg, but little is known about consumption of small-sized fish or about non-dietary determinants of circulating Hg levels. The purpose of this study was to evaluate whole blood mercury concentration (WBHg) and its major dietary and non-dietary correlates in Korean adults.MethodsWe analyzed cross-sectional data from 3,972 (male = 1,994; female = 1,978) participants who completed the Korean National Health and Nutrition Examination Survey IV, 2008 to 2009. Relevant factors included diet, geographic location of residence, demographics, and lifestyle. WBHg concentration was measured using cold-vapor atomic absorption spectrometry. Multivariable linear models assessed independent correlates of dietary and non-dietary factors for WBHg levels.ResultsMedian levels of WBHg were 5.1 μg/L in men and 3.7 μg/L in women. Higher levels of fish/shellfish intake were associated with higher levels of WBHg. Higher consumption of small-sized fish was linked to higher levels of WBHg. Non-dietary predictors of higher WBHg were being male, greater alcohol consumption, higher income and education, overweight/obesity, increasing age, and living in the southeast region.ConclusionsBoth dietary and non-dietary factors were associated with WBHg levels in the Korean population. There is significant geographic variation in WBHg levels; residents living in the mid-south have higher WBHg levels. We speculate that uncontrolled geographic characteristics, such as local soil/water content and specific dietary habits are involved.

The complete mitochondrial genome of Glyptothorax sinense (Siluriformes, Sisoridae)

Glyptothorax sinense (Siluriformes, Sisoridae), is a kind of small-sized freshwater fish which mainly distributes in the middle and upper reaches of the Yangtze River in China. In this study, the complete mitochondrial genome of G. sinense was first determined using a PCR-based method. The complete mtDNA sequence is 16,531 bp in length, including 22 transfer RNA genes, 2 ribosomal RNA genes, 13 protein-coding genes, and a non-coding control region (D-loop). The overall-based composition was 31.61% A, 26.66% T, 15.38% G and 26.34% C, with a relatively high A + T content (58.27%). This will provide a useful tool for evolutionary and population genetic studies of G. sinense.

Economic assessment of ecosystem services: Monetary value of seagrass meadows for coastal fisheries

Estimation of the economic value of ecosystem services is particularly incipient in the marine realm, where numerous services still need to be evaluated. Seagrasses deliver essential services to humans. In this paper, we determined the economic value of Cymodocea nodosa seagrass meadows for local fisheries at the oceanic island of Gran Canaria (eastern Atlantic). Large-sized fishes, which constitute the fishable fraction, were seasonally sampled through 2011 by means of visual censuses at 12 seagrass-dominated sites. The total fish biomass was 907.6 kg (894.55 kg of commercially-targeted fishes). By using standard market prices, we estimated that the monetary value of this biomass averaged 866 € ha−1; at the island-scale, this value adds up to 606 239 €, when considering the area covered by C. nodosa. Small-sized fishes (mostly juveniles that replenish fisheries) were also seasonally sampled, through a seine net, at the same 12 seagrass-dominated sites. Eight nearshore fish species with commercial interest used seagrass meadows as ‘nursery grounds’. Estimates of secondary production revealed that this fish production monetarily averaged 95.75 € ha−1 y−1 when considering standard market prices; this value adds up to 67 030.30 € y−1 at the island-scale, when considering the area covered by C. nodosa. This study provides complementary assessments of the key economic contribution of seagrass meadows for coastal fisheries as both ‘fishing’ and ‘nursery’ grounds. This is a way to promote the social perception of the key role that seagrasses play on the coast and, therefore, the necessity of incorporating seagrasses into conservation legislative frameworks.

Influence of artificial headlands on fish assemblage structure in the surf zone of a sandy beach, Kashimanada Coast, Ibaraki Prefecture, central Japan

To determine the effects of artificial headlands (groins with an anchor-shaped head portion) on the surf-zone fish assemblage structure of a sandy beach with strong wave action, three study sites (headland site sheltered behind the head portion, pocket-beach site between two adjacent headlands and exposed reference site without headlands) were sampled on the Kashimanada Coast, central Japan, in summer and autumn in 2012 and 2013. Distinct differences in physical conditions were recognized between the headland site and the other two sites throughout the study period, the former being characterized by lower wave height and turbidity, finer sediment particles and richer detritus. The fish assemblage structures also differed among the sites, the headland site supporting greater species and individual numbers. Cluster analysis showed clear differences in species composition of fish assemblages between the headland site and the other two sites. In addition, small-sized fishes tended to be more abundant at the headland site compared with the other two sites, although no differences were apparent in fish assemblage structure between the pocket-beach and reference sites. These results suggested that the presence of headlands had marked effects on the surf-zone fish assemblage structure in the study area.

Feeding of adult sea bream <i>Brama japonica</i> in the Pacific Ocean and the Bering Sea

Feeding habits of adult sea bream are considered on the samples collected in the North Pacific and Bering Sea in the last several years. This species is a predator with the diet highly dependent on its habitat and composition of prey (small-sized fish and squids). It has two or three peaks of consumption daily, which change seasonally and year-to-year; anyway, the morning (3-6 a.m.) is usually the time of the lowest consumption, at least in summer and autumn, and the daytime is the normal time for feeding. The sea bream does not eat zooplankton usually, but Euphausia pacifica was a significant portion of its diet (34 %) in the southern part of surveyed area in the summer of 2009, possibly because of high concentrations of euphausiids in that area. Daily ration of adult sea bream is 2.5-3.5 % of its body weight.

Ecological structure and function differs between habitats dominated by seagrasses and green seaweeds

Marine vegetated habitats, e.g. seagrass meadows, deliver essential functions and services to coastal ecosystems and human welfare. Impacts induced by humans, however, have facilitated the replacement of seagrasses by alternative vegetation, e.g. green rhizophytic seaweeds. The implications of habitat shifts for ecosystem attributes and processes and the services they deliver remain poorly known. In this study, we compared ecosystem structure and function between Cymodocea nodosa seagrass meadows and bottoms dominated by Caulerpa prolifera, a green, native, rhizophytic seaweed, through 5 ecological proxies: (i) primary production (via community metabolism), (ii) composition and abundance of epifauna (a proxy for provision of habitat for epifauna), composition and abundance of (iii) small-sized (juvenile) and (iv) large-sized (adult) fishes (proxies for provision of habitat for fishes), and (v) sediment retention (a proxy for sediment stabilization). Four of these proxies were greater in C. nodosa seagrass meadows than in C. prolifera beds: gross primary productivity (∼1.4 times), the total abundance, species density and biomass of small-sized fishes (∼2.1, 1.3 and 1.3 times, respectively), the total abundance and species density of large-sized fishes (∼3.6 and 1.5 times, respectively), and sediment stabilization (∼1.4 times). In contrast, the total abundance and species density of epifauna was larger (∼3.1 and 1.7 times, respectively) in C. prolifera than in C. nodosa seagrass beds. These results suggest that ecosystem structure and function may differ if seagrasses are replaced by green rhizophytic seaweeds. Importantly, ecosystem functions may not be appropriate surrogates for one another. As a result, assessments of ecosystem services associated with ecosystem functions cannot be based on exclusively one service that is expected to benefit other services.

Japanese Medaka: A Non-Mammalian Vertebrate Model for Studying Sex and Age-Related Bone Metabolism In Vivo

BackgroundIn human, a reduction in estrogen has been proposed as one of the key contributing factors for postmenopausal osteoporosis. Rodents are conventional models for studying postmenopausal osteoporosis, but the major limitation is that ovariectomy is needed to mimic the estrogen decline after menopause. Interestingly, in medaka fish (Oryzias latipes), we observed a natural drop in plasma estrogen profile in females during aging and abnormal spinal curvature was apparent in old fish, which are similar to postmenopausal women. It is hypothesized that estrogen associated disorders in bone metabolism might be predicted and prevented by estrogen supplement in aging O. latipes, which could be corresponding to postmenopausal osteoporosis in women.Principal findingsIn O. latipes, plasma estrogen was peaked at 8 months old and significantly declined after 10, 11 and 22 months in females. Spinal bone mineral density (BMD) and micro-architecture by microCT measurement progressively decreased and deteriorated from 8 to 10, 12 and 14 months old, which was more apparent in females than the male counterparts. After 10 months old, O. latipes were supplemented with 17α-ethinylestradiol (EE2, a potent estrogen mimic) at 6 and 60 ng/mg fish weight/day for 4 weeks, both reduction in spinal BMD and deterioration in bone micro-architecture were significantly prevented. The estrogenic effect of EE2 in O. latipes was confirmed by significant up-regulation of four key estrogen responsive genes in the liver. In general, bone histomorphometric analyses indicated significantly lowered osteoblasts and osteoclasts numbers and surfaces on vertebrae of EE2-fed medaka.SignificanceWe demonstrate osteoporosis development associated with natural drop in estrogen level during aging in female medaka, which could be attenuated by estrogen treatment. This small size fish is a unique alternative non-mammalian vertebrate model for studying estrogen-related molecular regulation in postmenopausal skeletal disorders in vivo without ovariectomy.

Assessing Fishing and Marine Biodiversity Changes Using Fishers' Perceptions: The Spanish Mediterranean and Gulf of Cadiz Case Study

BackgroundThe expansion of fishing activities has intensively transformed marine ecosystems worldwide. However, available time series do not frequently cover historical periods.MethodologyFishers' perceptions were used to complement data and characterise changes in fishing activity and exploited ecosystems in the Spanish Mediterranean Sea and Gulf of Cadiz. Fishers' interviews were conducted in 27 fishing harbours of the area, and included 64 fishers from ages between 20 to >70 years old to capture the experiences and memories of various generations. Results are discussed in comparison with available independent information using stock assessments and international convention lists.Principal FindingsAccording to fishers, fishing activity substantially evolved in the area with time, expanding towards deeper grounds and towards areas more distant from the coast. The maximum amount of catch ever caught and the weight of the largest species ever captured inversely declined with time. Fishers (70%) cited specific fishing grounds where depletion occurred. They documented ecological changes of marine biodiversity during the last half of the century: 94% reported the decline of commercially important fish and invertebrates and 61% listed species that could have been extirpated, with frequent mentions to cartilaginous fish. Declines and extirpations were in line with available quantitative evaluations from stock assessments and international conventions, and were likely linked to fishing impacts. Conversely, half of interviewed fishers claimed that several species had proliferated, such as cephalopods, jellyfish, and small-sized fish. These changes were likely related to trophic cascades due to fishing and due to climate change effects. The species composition of depletions, local extinctions and proliferations showed differences by region suggesting that regional dynamics are important when analysing biodiversity changes.Conclusions/SignificanceUsing fishers' perceptions, fishing and ecological changes in the study area were documented. The recovery of local ecological knowledge provides valuable information complementing quantitative monitoring and evaluation surveys.

The complete mitochondrial genome of Chinese lizard gudgeon, Saurogobio dabryi (Cypriniformes: Cyprinidae)

Saurogobio dabryi is a small-sized benthopelagic fish species in the famally Cyprinidae. In the present study, the complete mitochondrial genome of S. dabryi was determined. The complete mitochondrial genome of S. dabryi was 16,601 bp in length with the overall nucleotide base composition of A (29.66%), T (26.50%), G (16.80%) and C (27.04%), as well as an AT content of 56.16%. It contained 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, a control region and an L-strand replication origin (OL).