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"Fish populations."
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Multidecadal changes in fish composition and traits diversity in a marine park in the Gulf of California
No-take marine reserves allow overexploited fish populations to rebound. However, whether the resilience level of the community may recover is an open question. A community’s resilience to disturbances depends on the diversity of the species’ traits. We analyzed reef fish assemblages over 30 years in a no-take marine reserve to determine whether the fish composition and its ecological traits structure recovered after protection. We selected the National Park of Cabo Pulmo in the Gulf of California (Mexico), which is a model marine protected area because of its good management. From 1987 to 2017, fish assemblages were monitored to quantify species richness, density, and evenness. The ecological traits structure of the assemblages was computed using the traits richness, dispersion, and redundancy. We observed three distinct phases: (i) a decline period from 1987 to 1998 during which the species richness and fish density severely decreased due to resources exploitation and coral reef damage; (ii) a fish density recovery period following the creation of the reserve from 1998 to 2011; and (iii) a mature period where fish assemblages appear to be stable. However, during the fish recovery period, the fish composition changed. Some species became highly dominant while other species that were abundant during the pre-disturbance period did not recuperate. Thus, the fish assemblages’ evenness, traits dispersion, and traits redundancy decreased during the recovery period before stabilizing, probably decreasing the resilience ability of the community. Although Cabo Pulmo marine park is a success story since the fish density recovered, the prohibition of resource extraction alone did not restore the past resilience level of the fish assemblages, which may make them more vulnerable to future environmental disturbances.
Journal Article
Long-Term Monitoring of Fish Abundance Dynamics in the Middle Stretch of the Mesha River (Tatarstan)
The study area is located in the middle reaches of the Mesha River on the territory of the Republic of Tatarstan and is characterized by strong temporal variability in environmental factors and fish populations. The impact of environmental factors on fish species and communities was analyzed with regression and ordination methods. The dominant species were bleak, dace, chub, and roach, which together accounted for 60.7% of the total fish species. Over 15 years of research, there have been significant decreasing trends in overall density, species richness and density of individual fish species. The main factors determining the size of both the fish population and individual species were fishing effort and temperature during different months. The index of long-term similarity of fish populations was only 7.5%.
Journal Article
Droplet digital PCR applied to environmental DNA, a promising method to estimate fish population abundance from humic‐rich aquatic ecosystems
Measures of environmental DNA (eDNA) concentrations in water samples have the potential to be both a cost‐efficient and a nondestructive method to estimate fish population abundance. However, the inherent temporal and spatial variability in abiotic and biotic conditions in aquatic systems have been suggested to be a major obstacle to determine relationships between fish eDNA concentrations and fish population abundance. Moreover, once water samples are collected, methodological biases are common, which introduces additional sources of variation to potential relationships between eDNA concentrations and fish population abundance. Here, we evaluate the performance of applying the droplet digital PCR (ddPCR) method to estimate fish population abundance in experimental enclosures. Using large‐scale enclosure ecosystems that contain populations of nine‐spined stickleback (Pungitius pungitius), we compared the concentrations of fish eDNA (COI mitochondrial region, 134 bp) obtained with the ddPCR method with high precision estimates of fish population abundance (i.e., number of individuals) and biomass. To evaluate the effects of contrasted concentrations of humic substances (potential PCR inhibitors) on the performance of ddPCR assays, we manipulated natural dissolved organic carbon (DOC) concentrations (range 4–11 mg/L) in the enclosures. Additionally, water temperature (+2°C) was manipulated in half of the enclosures. Results showed positive relationships between eDNA concentration and fish abundance and biomass estimates although unexplained variation remained. Still and importantly, fish eDNA estimates from high DOC enclosures were not lowered by potential inhibitory effects with our procedure. Finally, water temperature (although only 2°C difference) was neither detected as a significant factor influencing fish eDNA estimates. Altogether, our work highlights that ddPCR‐based eDNA is a promising method for future quantification of fish population abundance in natural systems.
We evaluated the performance of applying the droplet digital PCR (ddPCR) method to estimate fish abundance in experimental enclosures. Significant positive relationships between eDNA concentration and fish abundance and biomass were found. Additionally, fish eDNA estimates from high DOC enclosures were not lowered by potential inhibitory effects.
Journal Article
Implications for Habitat Suitability Using Length–Weight Relationships and Condition Factors in the Chirchik River, Syr Darya Basin
Accurate fish growth and condition assessment is central to understanding the ecological health of freshwater ecosystems. Despite severe anthropogenic pressures, ecological and biometric studies of fish populations from heterogeneous habitats of the Chirchik River, a key tributary of the Syr Darya, remain poorly studied. Here, we demonstrate the length–weight relationships (LWRs) and condition factors of five freshwater fish species from the upper and middle parts of the Chirchik River, including two native and three invasive species. Observed positive ( Gymnodiptychus dybowskii , Rhodeus ocellatus , and Micropercops cinctus ) and isometric growth ( Pseudorasbora parva and Cottus jaxartensis ) patterns indicate good habitat and resource conditions in both reaches of the river. Relative condition factor ( K n ) values were consistently near 1.0 and did not differ significantly among species, indicating a stable physiological status. In contrast, Fulton’s condition factor ( K ) varied significantly, reflecting marked interspecific differences in body robustness and energy allocation strategies. Taken together, our findings provide vital biometric data for poorly studied and heavily human‐impacted rivers of Central Asia, and demonstrate the utility of combined growth and condition metrics as indicators of environmental suitability.
Journal Article
Evaluation of water quality and dam for sustaining the fish population dynamics
Bhagirathi is a Himalayan River, which flows in Uttrakashi district in Uttarakhand state. It is one of the most important streams of the Ganga River. This river is famous for dam construction and fisheries development. The fishes of commercial importance in cold water are Mahaseer, Snow Trout. The fish production depends on the physical, chemical as well as biological qualities of water. In the present paper, water quality evaluation and dam in the sustaining fish population dynamics have been reviewed to make aware the fish culturist and environmentalist about the water quality factors which influence health of a pond and to increase the fish yields to meet the growing demands of present time scenario of the our country. The construction of dams causes many problems. Water quality and discharge of water from the dam wall systems also indirectly affect the fish populations. In this study, we also review some of the important impacts associated with dams and their recommended mitigation measures. There is a negative impact on fish population dynamics, especially for downstream habits due to dams. Water quality is measured like temperature, turbidity, carbon dioxide, pH, alkalinity, hardness, BOD, TDS, Turbidity. The maximum oxygen content of water was recorded in January 13.02 ± 0.166 mg l−1 and minimum 9.4 ± 0.05 mg l−1 in July in site I phase I (before the reservoir dam wall). While in site II and phase I (After the dam), the maximum DO was observed in the month of January of 12.1 mg l−1 and minimum in July of 8.93 mg l−1. This is because water level is minimized in site II almost dried in winter. The CO2 of the Maneri Bhali phase I -Site I (before dam) was recorded maximum in April 3.10 ± 0.012 mg l−1. In Maneri Bhali phase I -Site II (After dam), the CO2 was recorded maximum 3.01 ± 0.003 mg l−1 in the month July. The river of Garhwal Himalaya harbors a rich aquatic diversity, the most common endemic fish species that inhabit this fresh water is the Schizothorax species. The maximum no. of fish were observed in winter and minimum in monsoon. At present, the production of these fishes from the streams is very poor and is not well managed from recreational and conservation point of view. If such is developed properly, it can have revenue potential for our state government. Sports, fisheries, tourism should be promoted.
Journal Article
HaCeD-Seq: a Novel Method for Reliable and Easy Estimation About the Fish Population Using Haplotype Count from eDNA
It is common to count the numbers of specified fish in the field after speciation of captured fish according to their morphology and to subject these counts to appropriate statistical analyses. In recent years, a non-invasive method to estimate the abundance of a particular fish species using environmental DNA (eDNA) has been developed. However, it is still difficult to determine accurate numbers of fish species using such method. We predict that the estimation of individuals of certain fish species in the field is more accurate and easier by using haplotypes of DNA in the fast evolutionary region. Therefore, we focused on the regulatory region (D-loop) in mitochondrial DNA, which is known to have a high genetic variation at the intraspecific level of the targeting eel. We investigated haplotype diversity in eel at first and then determined the number of D-loop haplotypes contained in their exfoliated cells in breeding water. Finally, we developed a novel analytical method, HaCeD-Seq, to estimate the number of individuals based on the abovementioned data.
Journal Article
Optimal Automatic Wide-Area Discrimination of Fish Shoals from Seafloor Geology with Multi-Spectral Ocean Acoustic Waveguide Remote Sensing in the Gulf of Maine
Ocean Acoustic Waveguide Remote Sensing (OAWRS) enables fish population density distributions to be instantaneously quantified and continuously monitored over wide areas. Returns from seafloor geology can also be received as background or clutter by OAWRS when insufficient fish populations are present in any region. Given the large spatial regions that fish inhabit and roam over, it is important to develop automatic methods for determining whether fish are present at any pixel in an OAWRS image so that their population distributions, migrations and behaviour can be efficiently analyzed and monitored in large data sets. Here, a statistically optimal automated approach for distinguishing fish from seafloor geology in OAWRS imagery is demonstrated with Neyman–Pearson hypothesis testing which provides the highest true-positive classification rate for a given false-positive rate. Multispectral OAWRS images of large herring shoals during spawning migration to Georges Bank are analyzed. Automated Neyman-Pearson hypothesis testing is shown to accurately distinguish fish from seafloor geology through their differing spectral responses at any space and time pixel in OAWRS imagery. These spectral differences are most dramatic in the vicinity of swimbladder resonances of the fish probed by OAWRS. When such significantly different spectral dependencies exist between fish and geologic scattering, the approach presented provides an instantaneous, reliable and statistically optimal means of automatically distinguishing fish from seafloor geology at any spatial pixel in wide-area OAWRS images. Employing Kullback–Leibler divergence or the relative entropy in bits from Information Theory is shown to also enable automatic discrimination of fish from seafloor by their distinct statistical scattering properties across sensing frequency, but without the statistical optimal properties of the Neyman–Pearson approach.
Journal Article
Fish Distribution in Lacustrine and Riverine Biotopes of Bratsk Reservoir Based on the Results of Hydroacoustic Surveys
Fish distribution in different areas of Bratsk Reservoir has been studied using hydroacoustic equipment. The average abundance of fish decreases (
r
= –0.70;
p
< 0.05;
R
2
= 0.49) from the near-dam reach (214 ± 34 ind./ha) to the water area in the upper reaches of the reservoir (113 ± 43 ind./ha). A similar relationship is observed in the dynamics of the abundance of early juveniles and the immature fish population. However, such relationship has not been found in fish with a size of more than >100 mm, which with a low abundance are relatively evenly distributed along the longitudinal axis of the reservoir (10.5 ± 6.6 ind./ha). The common perch (
Perca fluviatilis
Linnaeus, 1758) is the most abundant species in the reservoir, its highest concentrations are recorded in the lower lacustrine part of the reservoir (139 ± 22 ind./ha). Less abundant cyprinids (Cyprinidae) (41 ± 15 ind./ha) and whitefishes (Salmonidae, Coregoninae) (12 ± 4 ind./ha) are more evenly distributed along the longitudinal axis of the reservoir. Temperature stratification of the water column is an important factor in the ecological differentiation of the fish population in the reservoir. The major part of the ichthyomass consisting of relatively warm-water fish species from the families Percidae and Cyprinidae (common roach (
Rutilus rutilus
(Linnaeus, 1758) and common bream (
Abramis brama
(Linnaeus, 1758)) is concentrated in the warming up epilimnion. The fish population in the cold hypolimnion consists of single individuals of the Baikal omul (
Coregonus autumnalis
(Georgi, 1775)) and peled (
C. peled
(Gmelin, 1789)). Transverse distribution of fish depends on the presence of a runoff flow. At relatively high flow rates, fish begin to avoid the midstream part in the studied sites of the reservoir and concentrate in the floodplain areas (
R
2
= 0.54;
p
< 0.0001).
Journal Article