Native Fish Populations Research Articles

Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish.

Climate change affects populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the Moran effect. However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We combined multiple datasets for a retrospective analysis of time-series count data (5-28 annual samples per segment) at 144 stream segments dispersed over nearly 1,000 linear kilometers of range to characterize the population structure and scale of spatial synchrony across the southern native range of a coldwater stream fish (brook trout, Salvelinus fontinalis), which is sensitive to stream temperature and flow variations. Spatial synchrony differed by life stage and geographic region: it was stronger in the juvenile life stage than in the adult life stage and in the northern sub-region than in the southern sub-region. Spatial synchrony of trout populations extended to 100-200 km but was much weaker than that of climate variables such as temperature, precipitation, and stream flow. Early life stage abundance changed over time due to annual variation in summer temperature and winter and spring stream flow conditions. Climate effects on abundance differed between sub-regions and among local populations within sub-regions, indicating multiple cross-scale interactions where climate interacted with local habitat to generate only a modest pattern of population synchrony over space. Overall, our analysis showed higher degrees of response heterogeneity of local populations to climate variation and consequently population asynchrony than previously shown based on analysis of individual, geographically restricted datasets. This response heterogeneity indicates that certain local segments characterized by population asynchrony and resistance to climate variation could represent unique populations of this iconic native coldwater fish that warrant targeted conservation. Advancing the conservation of this species can include actions that identify such priority populations and incorporate them into landscape-level conservation planning. Our approach is applicable to other widespread aquatic species sensitive to climate change.

A labeled data set of underwater images of fish and crab species from five mesohabitats in Puget Sound WA USA

The sustainable management of fisheries and aquaculture requires an understanding of how these activities interact with natural fish populations. GoPro cameras were used to collect an underwater video data set on and around shellfish aquaculture farms in an estuary in the NE Pacific from June to August 2017 and June to August 2018 to better understand habitat use by the local fish and crab communities. Images extracted from these videos were labeled to produce a data set that is suitable for use in training computer vision models. The labeled data set contains 77,739 images sampled from the collected video; 67,990 objects (fishes and crustaceans) have been annotated in 30,384 images (the remainder have been annotated as “empty”). The metadata of the data set also indicates whether a physical magenta filter was used during video collection to counteract reduced visibility. These data have the potential to help researchers address system-level and in-depth regional shellfish aquaculture questions related to ecosystem services and shellfish aquaculture interactions.

Economic valuation of ecosystem services trade-offs of tilapia cage culture farm and native capture fisheries in Lake Maninjau, Indonesia

Research on the effects of cage aquaculture on native fish populations has revealed its negative and positive impacts. However, a separate analysis of its ecological and economic effects creates incomplete information for the decision-makers. Moreover, the inadequacy of time series data has caused challenges to knowledge-based decision-making in establishing new cage aquaculture sites, especially in low-middle income countries. We use the ecosystem services (ES) framework to analyse the synergy and trade-off of cage aquaculture to a native fish species, Gobiopterus sp. in Lake Maninjau, Indonesia, as an effort to provide comprehensive information to support local decision-makers and to fill the information gap. We engaged some modelling techniques such as the Maximum Entropy Model (MaxEnt) validated with field survey data, Bayesian Networks (BN), and Monte Carlo Simulation (MCS) in this research. The results show that cage aquaculture provides habitat services for the species and temporary forgone fish production due to the accelerated sulfur upwelling. The economic value of habitat provision reached 74,500 IDR per year per cage or 1,128 million IDR per year in 2017. Further, the average value of the forgone benefit of fish production in the current cage aquaculture business extends from more than 550 million IDR per year in the dry season to almost 600 million IDR per year in the rainy season. The results indicate that the negative impacts of cage aquaculture on the native fish population outweigh its benefit. The recommendation for management actions includes applying alternative aquaculture techniques and other technological interventions.

A Review of Suckermouth Armoured Catfish (Siluriformes: Loricariidae) Invasion, Impacts and Management: Is Its Invasion a Threat to Bangladesh’s Fisheries Sector?

Suckermouth armoured catfish of the genus Pterygoplichthys (Siluriformes: Loricariidae) are significant threats to aquatic biodiversity, ecosystems, habitats, and fishery production in different countries. Their unique characteristics and adaptive features help their successful invasion. These fish harm fish habitats, compete for food and space, prey on fish eggs, and displace the native fish populations. They erode river banks, alter benthic ecology, make holes in the river bank, and remove aquatic plants. Elimination, control, and intrusion prevention are possible management strategies. Utilising them as food and preparing value-added products and byproducts using them are viable ways to reduce their number. Management is challenging, owing to their tolerance and excellent adaptability. With severe dangers to Bangladesh's fisheries industry and aquatic environment, suckermouth armoured catfish have invaded natural waterbodies and aquaculture ponds. There is a lack of accurate information on invasion status, types of invading species, and potential dangers of invasion to create a management framework in Bangladesh. Therefore, this review introduces the key characteristics, habitats, invasion impacts, and management and utilisation aspects of suckermouth armoured catfish in different countries. The review may help in understanding how they affect native fish, aquatic organisms, habitats, and the aquatic environment globally. Finally, what kind of threats they may pose and how they can be managed sustainably in Bangladesh.

Efficacy of one‐time rotenone application for Westslope Cutthroat Trout restoration in Boulder Creek, Montana

AbstractObjectiveAlthough piscicides are an important tool for native fish management, our understanding of native fish population dynamics posttreatment (i.e., in putatively vacant habitat) is limited.MethodsHere, we describe long‐term trends in size and abundance of Cutthroat Trout Oncorhynchus clarkii in Lower Boulder Lake and Boulder Creek (Montana).ResultNo significant differences were found before and after treatment with rotenone in mean length and population density in Boulder Creek. Posttreatment genetic samples from Boulder Lake and upper Boulder Creek consisted entirely of the Westslope Cutthroat Trout Oncorhynchus clarkii lewisi used to refound the population. Middle and lower Boulder Creek genetic samples contained 99.4% and 98.4% Westslope Cutthroat Trout, indicating that some nonnative (Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri hybrid) fish survived the treatment. Population demographics showed robust recovery posttreatment; however, genetic results revealed the limitations of a one‐time treatment—that is, an incomplete fish kill.ConclusionWe demonstrate that Cutthroat Trout populations achieve recovery after rotenone treatment in the long term, but one‐time rotenone treatments on large drainages often fail to totally eradicate populations. Therefore, managers should plan on multiple treatments and utilize environmental DNA to help achieve total removal of target species.

Dietary overlap and selectivity among mountain steppe river fish in the United States and Mongolia.

Lotic systems in mountain regions have historically provided secure habitat for native fish populations because of their relative isolation from human settlement and lack of upstream disturbances. However, rivers of mountain ecoregions are currently experiencing heightened levels of disturbance due to the introduction of nonnative species impacting endemic fishes in these areas. We compared the fish assemblages and diets of mountain steppe fishes of the stocked rivers in Wyoming with rivers in northern Mongolia where stocking is absent. Using gut content analysis, we quantified the selectivity and diets of fishes collected in these systems. Nonnative species had more generalist diets with lower levels of selectivity than most native species and native species had high levels of dietary specificity and selectivity. High abundances of nonnative species and high levels of dietary overlaps in our Wyoming sites is a cause of concern for native Cutthroat Trout and overall system stability. In contrast, fish assemblages characterizing Mongolia mountain steppe rivers were composed of only native species with diverse diets and higher selectivity values, suggesting low probability for interspecific competition.

Megadroughts Pose Mega‐Risk to Native Fishes of the American Southwest

Climate change and a host of other human stressors on aquatic systems in the American Southwest are rapidly exceeding our ability to conserve native fish diversity. The most severe megadrought in over a millennium has compromised current management plans by exacerbating the impacts of altered hydrology, poor water quality, invasive species, and habitat fragmentation. Drought legacies are of particular concern, and existing conservation actions may not be sufficient to maintain resilient native fish populations, particularly if this drought persists. We draw examples from current literature and empirical research to support our contention that more resources and novel approaches to prioritizing environmental flows, improving ecological connectivity of populations, preventing and controlling invasive species, and establishing refuge populations are necessary to stave off extinctions. Moreover, shifts in socio‐political attitudes that better recognize environmental concerns must be integrated into water resource policy and management to achieve native fish conservation goals.

Single Nucleotide Polymorphism Markers with Applications in Conservation and Exploitation of Aquatic Natural Populations.

An increasing number of aquatic species have been studied for genetic polymorphism, which extends the knowledge on their natural populations. One type of high-resolution molecular marker suitable for studying the genetic diversity of large numbers of individuals is single nucleotide polymorphism (SNP). This review is an attempt to show the range of applications of SNPs in studies of natural populations of aquatic animals. In recent years, SNPs have been used in the genetic analysis of wild and enhanced fish and invertebrate populations in natural habitats, exploited migratory species in the oceans, migratory anadromous and freshwater fish and demersal species. SNPs have been used for the identification of species and their hybrids in natural environments, to study the genetic consequences of restocking for conservation purposes and the negative effects on natural populations of fish accidentally escaping from culture. SNPs are very useful for identifying genomic regions correlated with phenotypic variants relevant for wildlife protection, management and aquaculture. Experimental size-selective catches of populations created in tanks have caused evolutionary changes in life cycles of fishes. The research results have been discussed to clarify whether the fish populations in natural conditions can undergo changes due to selective harvesting targeting the fastest-growing fishes.

Invasive Brook Stickleback Culaea inconstans minimally alters the trophic ecology of four native fishes in Wyoming, USA

Invasive species introductions are a primary threat facing populations of native freshwater fishes. There are multiple mechanisms by which an invader can affect native species, with competition for food resources being one mechanism that can lead to declines in the distribution and abundance of native species. Invaders that are trophic generalists may cause shifts in the trophic ecology of native species and may be better suited for long-term persistence amid environmental stochasticity. Therefore, trophic studies can provide valuable information on the risk an invader poses to native species. Brook Stickleback Culaea inconstans is an invasive fish species in Wyoming whose effect on native fish assemblages is poorly understood. Our goal was to understand the potential for competitive interactions between Brook Stickleback and native fishes. We used stable isotopes of carbon (ẟ13C) and nitrogen (ẟ15N) to evaluate the feeding ecology of Brook Stickleback relative to four native fishes, and to explore whether native fish isotopic niches changed in sympatry with Brook Stickleback. We hypothesized that the isotopic niche of Brook Stickleback would be larger than that of native fishes, suggesting broader resource use. Additionally, we hypothesized that the isotopic niche of native fish populations sympatric with Brook Stickleback would contract. We did not find support for our hypotheses as the isotopic niche of Brook Stickleback was not substantially different from that of native fishes. Further, the isotopic niche of native fishes was not substantially affected by Brook Stickleback presence. As a result, we do not currently see evidence of Brook Stickleback altering the trophic ecology of native fish species. Our results provide insight to the effects of a small-bodied invasive fish species on native fishes in a previously unstudied region, and can help managers prioritize management actions to conserve native fishes.

Impact of Household Chemicals on the Ornamental Fish Poecilia sphenops (Valenciennes)

This study examined the impact of various household chemicals, such as Surf excel, hair dye, popular soap, fabric softener, shampoo, and coconut oil, on the ornamental fish Poecilia sphenops (Valenciennes in Cuvier and Valenciennes, 1846). Length-weight relationships, gonadosomatic and hepatosomatic indexes, oxygen consumption, and opercular beat rate were measured to assess the effects of the chemicals (10, 20, and 30 ppm) on the fish. Results showed that at higher concentrations of the chemicals, the fish exhibited increased breathing and signs of distress. The temperature of 28°C was found to be optimum for the growth of P. sphenops, while the lowest growth performance was shown at temperature 30°C. Fish ranged from 37 to 67 mm in total length and 1.10 to 3.10 g in body weight. The female to male sex ratio (4.9:1) deviated significantly from the unity (?²= 214.2, p<0.05). These findings indicate that the presence of such noxious chemicals are deleterious to natural populations of fish, and that the irresponsible discharge of sewage water into water bodies should be avoided.

The need for constructing endangered fish habitats that conform to climate‐driven flow changes in a western U.S. river

AbstractWarmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold‐water dam releases combined with drought‐related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life‐stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change.

The Ichthyofauna of the Bednja River, Ichthyological ‘Hot Spot’ in the Danube Basin—Exceptional Diversity under Strong Threats

The Bednja River is the longest river flowing with its full course exclusively through Croatia and one of the largest right tributaries of the Drava River, which belongs to the Danube River basin. Due to the variety of habitats present within the course of the Bednja River, as well as older literature reports, it can be expected that this river harbors a high number of freshwater fish species and would likely benefit from conservation and preservation efforts. We compiled and analyzed the existing literature data on the Bednja River fish communities and performed field investigations at various localities on this river in order to describe the current structure of its freshwater fish fauna and monitor changes induced by human activities. Our results corroborate the presence of a rich and diverse fish community. Moreover, with 36 native species, the Bednja River harbors one of the richest fish communities in Croatia as well as in the Danube basin. Unfortunately, modifications of the native fish community were evident in the form of local extinctions, reductions in the population abundance of several native species and the presence of non-native species. Habitat degradation and fragmentation were identified as the most serious threats provoking negative effects on the native fish populations, followed by predatory and competitive effects of invasive species.

Hydrology-mediated ecological function of a large wetland threatened by an invasive predator.

Invasive species are one of the greatest threats to ecosystems, disrupting ecosystem function and leading to the collapse and extinction of native species. While populations of native fishes in the Everglades are tied to the system's natural hydrological dynamics, Asian Swamp Eels (Monopterus albus/javanensis) are drought-resistant fish first reported from Florida in 1997 and the Everglades in 2007. Using a 26-year dataset that included a 13-year baseline period prior to swamp eel arrival in Taylor Slough, we assessed population changes of common small fishes and decapods that are important prey for larger vertebrate predators. After invasion, populations of two crayfishes collapsed by >95 %, two fishes declined by >80 %, two fishes had intermediate declines of 44-66 %, and three species remained unchanged. Species most strongly reduced were those dependent on predator-free habitats at the onset of the wet season, indicating drought-resistant swamp eels have introduced novel predator effects and disrupted the hydrology-mediated production of aquatic animals that are prey for many larger predators. Ongoing Everglades restoration is designed to restore hydrological conditions that support production of crayfishes and fishes, and nesting wading birds reliant on them. Water management may have facilitated the invasion of swamp eels. Our results suggest that the continued spread of swamp eels may result in adverse consequences for Everglades trophic dynamics and potentially diminish benefits expected from the $20B+ restoration.

Multi-decadal trends in large-bodied fish populations in the New South Wales Murray–Darling Basin, Australia

Context Native fish populations in Australia’s Murray–Darling Basin (MDB) have experienced severe declines since European settlement. Information on their status is needed to guide management and recovery. Aims To quantify trends in MDB fish populations in New South Wales (NSW) from 1994 to 2022. Methods Relative abundance, biomass, and size structure were examined using generalised additive mixed models at NSW MDB and river catchment (valley) scales for five native species (Murray cod, Maccullochella peelii; golden perch, Macquaria ambigua; silver perch, Bidyanus bidyanus; Macquarie perch, Macquaria australasica; freshwater catfish, Tandanus tandanus) and one alien species (common carp, Cyprinus carpio). Key results There was strong inter-annual variation in relative abundance, biomass and population structure for all species. At the Basin scale, relative abundance of Murray cod, golden perch and common carp increased across the time series, with no clear trends for silver perch, Macquarie perch or freshwater catfish. Patterns in relative abundance, biomass, and population structure were variable among valleys for most species. Conclusions and implications Although native fish populations in the MDB remain degraded and face escalating threats, recent increases in the abundance of some native species are an encouraging sign that integrated restoration efforts can improve the outlook for native fish.

Food and feeding habits of Tor tambra (Valenciennes, 1842) in Cibareno River, West Java, Indonesia

The Cibareno River in Sukabumi, West Java, is the habitat of Tor tambra, one of Indonesia's most highly valuable native freshwater fish species. The native fish population in this river may be threatened by the planned weir construction. The study aims to examine the food and feeding habits of Tor tambra in the Cibareno River. This study was carried out for four months (May, June, July, and September 2022) at six locations in the Cibareno River. A total of 61 individuals of T. tambra displayed an isometric growth pattern with good condition factor. Aquatic insects were the primary food, with nematodes and phytoplankton acting as supplements. Plant seeds were often eaten as an extra source of food. These results were supported by fish morphometric data such as relative mouthwidth and relative gut length, which showed that they are omnivorous and tend to be carnivorous. In addition, the relative eye diameter of the fish indicates that Tor tambra is a diurnal forager. The findings suggest that both in-situ and ex-situ conservation methods are viable options for the preservation of Tor tambra in the Cibareno River.

Мониторинг естественного воспроизводства популяций рыб озера Едильсор

The article presents the results of monitoring the commercial fish populations of Edilsor Lake. Edilsor is one of the large lakes of the West Kazakhstan region of fishery importance, in connection with which the monitoring of the natural numbers of populations of aboriginal commercial fish species of the studied reservoir is relevant. Control catches were used to analyze the state of natural fish populations. As tools for catching biological objects, commercial fish, lake plug-in nets with mesh sizes of 30–70 mm were used. Control catches of aboriginal commercial fish were carried out during the period of field studies. The captured biological objects were subjected to the analysis of such biological indicators as species, age composition, ratio of females and males in the catch, weight, length of the whole body of fish, according to the results obtained, the average values were determined. As a result of control catches, the species composition of the ichthyofauna of Lake Edilsor included the following species of aboriginal commercial fish: carp — 7.1 %, bream — 16.7 %, blue bream — 7.1 %, crucian carp — 4.8 %, perch — 64.3 %. The largest population was characterized by the perch population, which amounted to 27 individuals, the bream was less common — 7 individuals, the carp and blue bream — 3 individuals, the smallest number was observed in the population of crucian carp, which amounted to 2 individuals. According to the weight ratio, fish species are located as follows: perch — 40 %, carp — 32.5 %, bream — 15.8 %, crucian carp — 8.5 %, blue bream — 3.2 %. The largest mass falls on representatives of perch — 6.94 kg, followed by carp — 5.63 kg, bream — 2.73 kg, crucian carp — 1.47 kg, blue bream — 0.56 kg.

Midgut Bacterial Microbiota of 12 Fish Species from a Marine Protected Area in the Aegean Sea (Greece)

Fish microbiome science is progressing fast, but it is biased toward farmed or laboratory fish species against natural fish populations, which remain considerably underinvestigated. We analyzed the midgut bacterial microbiota of 45 specimens of 12 fish species collected from the Gyaros Island marine protected area (Aegean Sea, Greece). The species belong to seven taxonomic families and are either herbivores or omnivores. Mucosa midgut bacterial diversity was assessed by amplicon metabarcoding of the 16S rRNA V3–V4 gene region. A total of 854 operational taxonomic units (OTUs) were identified. In each fish species, between 2 and 18 OTUs dominated with cumulative relative abundance ≥ 70%. Most of the dominating bacterial taxa have been reported to occur both in wild and farmed fish populations. The midgut bacterial communities were different among the 12 fish species, except for Pagrus pagrus and Pagellus erythrinus, which belong to the Sparidae family. No differentiation of the midgut bacterial microbiota was found based on feeding habits, i.e., omnivorous vs. carnivorous. Comparing wild and farmed P. pagrus midgut bacterial microbiota revealed considerable variation between them. Our results expand the gut microbiota of wild fish and support the host species effect as the more likely factor shaping intestinal bacterial microbiota.

Steelhead trout (Oncorhynchus mykiss) fed probiotic during the earliest developmental stages have enhanced growth rates and intestinal microbiome bacterial diversity

Sustainable aquaculture practices can help meet the increasing human demand for seafood, while easing pressures on natural fish populations. Studies aimed at increasing fish production in aquaculture have included supplementary dietary probiotics that often promote general health and enhanced growth rates by altering the microbiome of the host. Steelhead trout (Oncorhynchus mykiss) is anadromous, like salmon, and it is a subspecies of rainbow trout capable of rapid growth, making it an attractive fish to the aquaculture industry. In this study, the impact of feeding a Bacillus subtilis probiotic on the bacterial microbiome of steelhead trout was examined temporally across several stages of animal development, from eggs (day -19) through 184 days after hatching, in relation to physiological measures. Diets included: commercial feed only as a control (A), continually-fed probiotic top-coated on commercial feed (B), commercial then switch to probiotic feed (C), or probiotic then switch to commercial feed (D). Validation of probiotic concentrations on feed and in fish tissues was performed using CFU/g and qPCR, respectively. Fish growth was measured and samples for intestinal microbiome analyses were collected at multiple timepoints during fish development. Fish fed diet D yielded higher weights than the other three diets, with little impact on other biometric parameters. However, bacterial microbiome analysis indicated an increasing trend of overall alpha diversity from the egg stage to day 29 for fish fed the various diets with diet D having the highest diversity. Fish fed diets A and D maintained a high alpha diversity beyond day 29 in contrast to a decreased trend for fish still being fed probiotics in diets B and C. The fish fed diets B and C harbored a significantly higher relative abundance of Bacillus sp. in their total microbiomes (feces + mucosa). Interestingly, the mucosal-only microbiome indicated little variation between the four groups of fish. Feeding the probiotic earlier in development, during the hatchery phase, to influence bacterial microbiome composition in the intestine (rather than later after the microbiome has been established) appears to be a more effective aquaculture practice by enhancing microbiome diversity while enabling higher fish yields.

Assessing the specificity of the Rosette agent DNA amplification: An optimized protocol for the detection of standard DNA among studies.

Assessing the specificity of the Rosette agent DNA amplification: An optimized protocol for the detection of standard DNA among studies.

Molecular Diversity of Diplostomum spathaceum (Digenea: Diplostomidae) on the Capoeta umbla and Cyprinus carpio (Cypriniformes) Using Mitochondrial DNA Barcode

Diplostomid trematodes (Digenea) include a wide and diverse group of common digeneans. Diplostomid larval stages are significant pathogens that may exert grave effects on both natural fish and aquaculture populations. Diplostomum species, which use fish as a second intermediate host, is one of the most common trematode species, which affects the fish welfare negatively with the formation of cataracts by settling in the eye. This study is determined the molecular characterization of Diplostomum parasite in Cyprinus carpio and Capoeta umbla for the first time from Turkey, based on the mitochondrial COX1 sequence data. Diplostomum samples were determined as Diplostomum spathaceum according to the phylogenetic trees created in the light of the morphological and COX1 sequence data. Sequence results matched ~98-100% with D. spathaceum as a result of blast analysis. It was defined that this parasite was represented by three different haplotypes in Turkey. As a result of haplotype analysis performed on a total of 162 isolates in GenBank and obtained in this study, 40 polymorphic regions and 58 haplotypes were determined. This haplotype network had arranged within a star-like configuration with a main central haplotype. This shows that the variation within D. spathaceum species is quite high. The mean abundance, mean intensity, and prevalence of the parasite in C. carpio were 8.29 (5.80-11.24), 10.91±9.37 (1-39), and 76%, respectively. In the C umbla, mean abundance, mean intensity, and prevalence were calculated as 11.54 (10.16-12.92), 14.07±16.59 (1-67), and 82%, respectively.