Assessment Of Fish Communities Research Articles

Refinement of the NISECI ecological index reference conditions for Italian freshwater fish communities in the eastern Emilia-Romagna region

Following the Water Framework Directive 2000/60/CE (WFD), each member state of the European Union must monitor compliance of its rivers with ecological quality standards through biological quality indicators. The New Italian Index of the Ecological State of Fish Communities (NISECI) was developed in 2017 for the assessment of fish communities, as directed by the WFD in Italian freshwater habitats. According to the WFD, the general reference conditions (GRCs) of NISECI must be refined on a regional scale through new calculation of its metrics and sub-metrics. In the present study we used environmental and ichthyological data from 457 fish samplings distributed among 299 sampling sites within 84 different water bodies collected from 1995 to 2012 to develop: 1) new lists of expected species for six homogeneous zones identified in the Reno basin (Italy) and in the eastern regional basins of the Emilia-Romagna region; and 2) the threshold values for their species-specific abundance. Results were set as refined reference conditions (RRCs) for two of the metrics used in the application of the NISECI index in the study area (i.e. X1, relating to indigenous species and X2,b, for the abundance of expected species). The RRCs were tested by applying NISECI to 24 monitoring sites of the regional surface water monitoring network (i.e., ARPAE) and comparing the results with the application of NISECI using the GRCs. Furthermore, the analytical power of the refined NISECI was evaluated by relating the findings to three expert-based blind assessments of fish community ecological status. The results confirmed an increase in refined NISECI values and its higher consistency with expert-based assessment, supporting the validity of the presented method for RRC development and its potential for application in other regions.

Alleviating the loss: A conical fish screen installation reduces native fish entrainment at a gravity‐fed water diversion

Abstract Each year, millions of fish are extracted from Australian waterways by the pumping and diversion of water into irrigation systems. Fish protection screens can help reduce these losses but are largely untested in Australian rivers. In this study, a large, gravity‐fed irrigation offtake on Gunbower Creek, Victoria, Australia, was investigated for fish and debris entrainment. Experiments were performed under screened and unscreened conditions across various river flows. Mark–release–recapture experiments were undertaken with fingerlings of two recreationally significant fish species, Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua), together with wild fish community assessments, to determine how effective the screen was at reducing fish entrainment into the irrigation channel. The mean percentage of recaptured fingerlings was significantly lower when the irrigation channel offtake was screened compared with unscreened. Entrainment of released fish into the irrigation channel was reduced by >98%. Similarly, wild fish entrainment was significantly lower when the irrigation channel was screened. When screened, fewer wild species dominated the sampled fish community, and entrained fish were generally <40 mm in length. Debris loads decreased significantly in the irrigation channel owing to the screen, indicating the economic benefits of fish screens. Implementing screens could aid in native fish conservation efforts in riverine environments.

How eDNA data filtration, sequence coverage, and primer selection influence assessment of fish communities in northern temperate lakes

AbstractFor nearly 15 years now, environmental DNA has demonstrated its effectiveness in monitoring biodiversity. Methodological and technical improvements have significantly enhanced the field. However, the effect of factors such as sequence coverage, bioinformatic filtration, and primer choice have been less explored or need to be optimized according to specific survey objectives and study site characteristics. We evaluated these factors to help optimize monitoring fish biodiversity in North American temperate lakes. We sampled water for fish community eDNA analysis in 12 lakes from southwestern Québec, Canada. The lakes were selected to encompass a wide range of surface areas and species richness. We sampled water from a total of 520 sites (25–50 per lake) and analyzed three mitochondrial DNA regions (12S rRNA; 16S rRNA; and cytb) using NovaSeq sequencing. Our results, based on rarefied count matrices (from a sequencing depth of 100,000 to a minimum depth of 1000 reads per sample), showed that keeping only species in each sample if they represented at least one thousandth (species minimum read proportion threshold = 0.001) of the sample's reads was adequate to remove false positives and had a limited negative impact on true positives with low read counts. The sequencing depth was found to have a negligible impact on the accuracy of fish community assessment in a given lake. With the same sequencing depth and a complete local reference database for each primer set, a single primer set produced similar species richness medians than the combination of two or three primer sets. Overall, 12S and 16S detected more species and provided more consistent community profiles than cytb. Based on our observations, we suggest using the 12S MiFish‐U primer set and applying a minimum proportion of 0.001 reads per species and site to monitor north‐temperate lentic freshwater fish communities.

Observing the Arctic: A comparison of environmental DNA (eDNA) and electrofishing for monitoring Arctic char and Atlantic salmon

AbstractThe current knowledge about fish biodiversity and species distributions in Arctic freshwater systems is generally limited. This contrasts the clear urgency for more accurate biodiversity data to assess the effects of future ecosystem challenges such as climate change and other anthropogenic effects. Here we compare traditional electrofishing surveys with environmental DNA (eDNA) for monitoring species distribution of Atlantic salmon (Salmo salar) and Arctic char (Salvelinus alpinus) in the West Greenlandic sub‐Arctic river system of Kapisillit, which contains the only known population of Atlantic salmon in Greenland. Overall, electrofishing and eDNA surveys show high compatibility in regard to species detection and quantification, with Arctic char confirming a significant relationship between eDNA concentration and observed fish abundance. Both methods confirm a shift in species occurrence and relative species abundance through the river system. Specifically, salmon is restricted to the lower warmer sections of the river system while Arctic char is found throughout the system but dominates the upper parts. In total, the study supports eDNA as a promising tool for fish community assessment, which may serve a wide array of applications for Arctic freshwater monitoring. These applications include analyzing species occurrence and distribution of native and invasive species, as well as documenting potential shifts in relative species abundance as shown here. Given the ease of sampling and high sensitivity of the method, eDNA provides a powerful cost‐effective approach capable of detecting species in remote areas as well as corroborating fish community monitoring programs. This may especially be valuable for monitoring in the Arctic where logistic complications with sampling and high operational costs so far constrains routine monitoring.

Fish community assessment of shelf-edge artificial reefs along east-central Florida

Artificial reef development is a popular management tool used to enhance fish stocks, mitigate degradation or loss of natural habitats, and provide additional recreational opportunities. In Florida, artificial reef development is a top priority of the Florida Fish and Wildlife Division of Marine Fisheries Management’s Artificial Reef program; however, despite their popularity and support, our scientific understanding of how artificial reefs ecologically facilitate marine fisheries is limited in certain habitats. This is especially true of the many artificial reefs along Florida’s central east coast, which has received sporadic assessment over the past few decades. The objective of this study was to conduct a fishery-independent assessment of the reef fish communities inhabiting the artificial reef sites off central east coast Florida using a combination of vertical longline sampling (VLL) and baited remote underwater videos (BRUV). Red snapper (Lutjanus campechanus) and vermilion snapper (Rhomboplites aurorubens) had the largest catch-per-unit-effort (CPUE) during VLL sampling, with red snapper CPUE significantly greater on rubble artificial reefs deeper than 40 m and vermilion snapper CPUE significantly greater on artificial reefs shallower than 30 m. A total of 62 fish species were observed on BRUVs, and community analysis indicated that red snapper, vermilion snapper, and tomtate (Haemulon aurolineatum) contributed the most to differences in community composition. Red snapper had the greatest abundance on sites deeper than 40 m, while vermilion snapper and tomtates had greater abundance on sites shallower than 30 m; all three species were more abundant during summer. This study provides the first quantitative assessment of reef fish communities on artificial reefs along central east coast Florida. Further monitoring is encouraged to unravel possible interactive effects of reef type and other environmental factors on fish assemblages, although it is evident that the reefs sampled support multiple managed fisheries species.

Assessment of fish communities from biotic type 6 in Black Sea Basin in Bosnia and Herzegovina

Fish are very sensitive to changes in damming of rivers, fragmentation and destruction of habitats, and changes in physical and chemical parameters. Changes in species diversity are a signal indicating that a significant and, as a rule, long-term change in one or more factors has occurred in the aquatic ecosystem. This in long term could lead to reduction of diversity and significant changes in the structure and dynamics of aquatic ecosystems. Biomonitoring of ichthyofauna is a very important element in the ecological assessment of water quality since changes in the structure of the fish community reflect changes in the quality of water in freshwater systems. The grouping of fish into ecological guilds has greatly improved our understanding of the impact of anthropogenic activities on fish and their communities. Therefore, the fish guilds represent the basis for ecological assessment based on the preferences of each recorded species in relation to tolerance, habitats, nutrition, reproduction and migrations. The results of the analyses of the structure of fish communities at 166 sites in biotic type 6 in the waters from the Black Sea Basin in Bosnia and Herzegovina have shown that the greatest influence on the distribution of different fish species has water temperature, flow, dissolved oxygen, and pH value. Obtained results clearly indicate an inverse relationship between altitude and the level of fish biodiversity. Values of applied diversity indices stress that fish communities in a river system usually follow a pattern of increasing species richness and diversity from upstream to downstream.

A comparison of passive and active gear in fish community assessments in summer versus winter

Fish populations and communities are monitored using a variety of sampling gears, each with their own inherent biases. Gear biases can arise from a number of factors, such as fish species characteristics (e.g., body shape/size, physiology, and behaviour), species habitat requirements, as well as the abiotic characteristics of sites sampled. Such factors and their effects on gear selectivity are also heavily influenced by seasonality. Consequently, understanding the effects of seasonal changes on gear selectivity is of vital importance, especially during the winter—a season seldom studied in freshwater systems. Here, we compared the selectivity, efficiency, and degree of biodiversity in fish communities sampled using three gear types: minnow traps, Windermere traps, and electrofishing during summer and winter in Hamilton Harbour, ON, Canada. Catch per unit effort was similar among gear types in the summer, whereas in the winter, minnow traps captured the most fish. Electrofishing samples were the most species rich and species diverse, but only during the summer. Additionally, sampling efficiency and the number of different species encountered was highest when all gear types were used in combination, followed by electrofishing alone, Windermere traps alone, and minnow traps alone in both seasons. Each gear type differed in its selectivity for certain species, which was further influenced by seasonality. This resulted in the fish communities caught within each gear type being dissimilar from one another. Our study highlights the importance of understanding gear type selectivity, particularly under different climatic conditions, and outlines the importance of incorporating multiple gear types in ecological assessments of fish populations and communities.

Less is more – Basic quantitative indices for fish can be achieved with reduced gillnet sampling

Obtaining a representative sample is fundamental to the assessment of fish communities. In this study we used data from 99 different surveys of 29 artificial lakes in the Czech Republic to evaluate the precision of fish community indicator estimates based on reduced gillnet scenarios derived from triplet gillnets installed in each particular locality, depth strata and habitat. Forty-four indicators (based particularly on numbers and biomass per unit of effort – NPUE and BPUE, respectively) were compared between the full sampling design (three gillnets at every sampling location) and six reduced scenarios which were combinations removing one or two gillnets from the triplets. The whole community comparison found the accuracy (R2) between the full sampling design and reduced scenarios usually to be above 0.9. Strong accuracy was also found for species richness and mean fish weight. In individual species comparisons, accuracy above 0.75 was found for common species in a given habitat, whereas accuracy for less common species sometimes dropped below 0.5. Setting one gillnet in an appropriate depth strata and lake locality appears to be sufficient for unbiased overall NPUE, BPUE, and species composition estimates, and at the same time, reduces sampling effort and minimizes unwanted fish mortality. Capturing less common species in a given habitat is more or less accidental and additional sampling effort increased the probability of catching these species. On the other hand, methods targeting rare species of interest may be considered instead of increasing gillnet effort above the CEN standard.

Sucked in by eDNA – a promising tool for complementing riverine assessment of freshwater fish communities in Aotearoa New Zealand

ABSTRACT There is increasing interest in the health of waterways in Aotearoa New Zealand. The National Policy Statement for Freshwater Management 2020 (NPS-FM) places a greater onus on resource managers to report on the state of freshwater ecosystem health, including fish. Routine fish monitoring is time intensive and is principally conducted in ‘wadeable’ stream reaches. In comparison, environmental DNA (eDNA) sampling is a relatively recent and rapid technique that likely detects fish and other vertebrate and invertebrate taxa over a broader spatial scale. In this study, we present data for five wadeable streams comparing diversity derived from multi-year standardised electrofishing with eDNA samples collected from the same reaches. Further, we explore whether the number of eDNA monitoring ‘reads’ for species at a site may provide an approximate (semi-quantitative) indication of their ‘near field’ relative abundance based on one-pass electrofishing captures. Results indicated that while some aspects of the methodology require fine-tuning, eDNA sampling shows substantial promise for complimenting state of the environment (SOE) reporting for describing fish diversity in wadeable streams. The use of aquatic eDNA monitoring to provide a cost-effective indication of broader catchment scale biodiversity (e.g. birds and exotic pests) in wadeable and non-wadeable streams is also discussed.

Challenges in assessing the Neotropical fishes using DNA metabarcoding

Species richness is a metric of biodiversity usually used in fish community assessment for monitoring programs. This metric is often obtained using traditional fisheries methods that rely on capture of target organisms, resulting in underestimation of fish species. DNA metabarcoding has been recognized as a powerful noninvasive alternative tool for fish biomonitoring and management. Despite the increasing popularity of this method for the assessment of aquatic megadiverse ecosystems, its implementation for studying the highly diverse Neotropical ichthyofauna still presents some challenges. One of them is to devise what primer set could reliably amplify the DNA of all fish species from a megadiverse river basin and have enough resolution to identify them. In order to identify and overcome these drawbacks, we have investigated the efficiency of the metabarcoding approach on Neotropical fishes using a mock sample containing genomic DNA of 18 fish species from the Jequitinhonha River basin, Eastern Brazil. We compared three primer sets targeting the 12S rRNA gene: two universal and widely used markers for fish metabarcoding [MiFish (~170bp) and Teleo_1 (~60bp)], and NeoFish (~190bp), recently developed by our research group specifically for the identification of Neotropical fishes (Milan et al., 2020). Two samples amplified using three primers were sequenced in a single multiplexed Illumina MiniSeq run, using normalized and non-normalized pools. Bioinformatic analyses were performed using a DADA2/Phyloseq based pipeline to perform filtering steps and to assign Amplicon Sequence Variants (ASVs). We used a custom 12S reference sequence database that included 190 specimens representing 101 species and 70 genera from the Jequitinhonha and São Francisco river basins. A total of 187 ASVs were recovered: 79, 66 and 42 for NeoFish, MiFish and Teleo_1, respectively. ASVs of unexpected species were identified for both pools (Fig. 1), though each of these ASVs had an abundance of less than 50 copies. In addition, species of the Hoplias and Prochilodus genera could not be identified at the species level, due to identical sequences within each genus, possibly because of the insufficient variation within the 12S region recovered by these primers’ amplicons. Unexpectedly, although a single individual of each species was placed in the pools, more than one ASV was identified for some species, likely caused by PCR biases. Overall, all primer sets displayed similar taxonomic resolution for the DNA pools and recovered all species, except for NeoFish, which could not detect Steindachneridion amblyurum due to an incompatibility in the 3’ of the NeoFish forward primer and Teleo_1, which could not identify Steindachnerina elegans. These results highlight the need of reliable databases in order to enable the full assignment of ASVs and OTUs to species level, and the importance of calibrating the DNA metabarcoding approach with mock samples to identify weaknesses and pivotal steps prior to the application on large scale DNA based biodiversity evaluation, that can help with the complex task of conserving the megadiverse Neotropical ichthyofauna.

Highly diverse mesophotic reef fish communities in Raja Ampat, West Papua

Mesophotic coral ecosystems (MCEs; reefs 30–150 m depth) are poorly studied, with existing research heavily geographically biased away from the most species-rich reef regions. Yet, MCEs are of high interest because of their unique species and potential to act as refuges from the impacts of fishing. Using baited remote underwater video systems, we surveyed reef fish communities from 2 to 85 m depths throughout the Raja Ampat archipelago in West Papua, Indonesia—an area considered the heart of the Coral Triangle where coral reef biodiversity is greatest. We sought to provide the first assessment of fish communities across this depth gradient in the region and identify whether human population density and market access differently affected fish abundance based on depth. Here we show that—similar to shallow reefs—Raja Ampat MCEs are exceptionally diverse, with 152 fish species recorded at depths greater than 40 m. We found that fish community structures were highly depth driven, with declines in fish abundance at increased depth. In contrast to previous studies elsewhere in the world, we found that the proportion of planktivores declined across the shallow reef to MCE depth gradient. While greater human population density correlated with lower Epinephelidae and Lutjanidae abundance (two key fisheries families), we did not find evidence that MCEs provide a depth refuge from fishing. Surprisingly, we also found that fish abundance declined at greater distances from the major regional market—likely caused by historical fisheries pressure in more remote areas. These results both expand upon and contrast some previously established MCE-depth patterns and human impact patterns on fish communities, suggesting that regional context and historical pressures matters. Our findings highlight the need for future MCE studies within the Coral Triangle region.

The MacKinnon Lists Technique: An efficient new method for rapidly assessing biodiversity and species abundance ranks in the marine environment.

Widespread and ever-increasing anthropogenic impacts in the marine environment are driving a need to develop more efficient survey methods for monitoring changes in marine biodiversity. There is a particular urgent need for survey methods that could more rapidly and effectively detect change in species richness, abundance and community composition. Here, test the suitability of the Mackinnon Lists Technique for use in the marine environment by testing its effectiveness for rapid assessment of fish communities. The MacKinnon Lists Technique is a time-efficient and cost-effective sampling method developed for studying avian tropical biodiversity, in which several list samples of species can be collected from a single survey. Using the well-established MaxN approach on data from deployments of a Baited Remote Underwater Video Systems for comparison, we tested the suitability of the MacKinnon Lists Technique for use in marine environments by analysing tropical reef fish communities. Using both methods for each data set, differences in community composition between depths and levels of protection were assessed. Both methods were comparable for diversity and evenness indices with similar ranks for species. Multivariate analysis showed that the MacKinnon Lists Technique and MaxN detected similar differences in community composition at different depths and protection status. However, the MacKinnon Lists Technique detected significant differences between factors when fewer videos (representing reduced survey effort) were used. We conclude that the MacKinnon Lists Technique is at least as effective as the widely used MaxN method for detecting differences between communities in the marine environment and suggest can do so with lower survey effort. The MacKinnon Lists Technique has the potential to be widely used as an effective new tool for rapid conservation monitoring in marine ecosystems.

Fish communities and environmental variables during dry season in Pampanga estuary (Philippines)

Baseline assessment of fish communities and selected environmental variables (salinity, water temperature, water transparency, current speed, total suspended solid, chlorophyll a) was conducted in Pampanga estuary (Philippines) during a specific dry season (April 2010). The aims were: (a) to examine the variations of fish diversity and community structure, in relation to neap and spring tides and estuary zones and; (b) to examine the influence of environmental variables on fish communities. Reconnaissance showed that salinity was measurable at 6.8 kilometers from the rivermouth, for the surface and mid-water layers, and at 15.9 kilometers for the bottom layers, indicating the occurrence of a salt wedge. Bottom salinity was used to establish the sampling stations, grouped into 3 zones (lower 1–3, middle 4–6, upper 7–9). Sampling of fish, using otter trawl, and measurement of environmental variables were done under four tidal conditions at each station (neap low and high tide; spring low and high tide). Neap tide showed low and homogenous horizontal salinity, higher temperature, slower current speed, high TSS and chlorophyll a, whereas, spring tide showed higher salinity, horizontal saline stratification, lower temperature, faster current speed, low TSS and chlorophyll a. A total of 330 fish were captured from 32 trawl samples, encompassing 20 families and 27 species. Number of species generally did not vary between neap (20) and spring tide (18), but showed a decreasing pattern from lower to the upper estuary. Only 36% of total species were shared between neap and spring tides. Fish abundance was significantly affected by neap and spring tide, and zonation, whereas fish biomass was solely affected by zonation. Arius manillensis was the most typifying species, suggesting high probability of encounter. Chlorophyll a, TSS, salinity and current speed have a significant influence on the variations of abundance, biomass and frequency of occurrence of particular fish species.

Fitting methods and seasonality effects on the assessment of pelagic fish communities in Daya Bay, China

Abstract The general relationship indicating that biomass decreases with individual body size is referred to as size spectra. This is consistent with the power law that characterizes size frequency distributions. While many previous studies have used the estimated exponent in size spectra as a metric to assess external perturbations, limited empirical studies have focused on the fitting methods. Here, we compared the effects caused by fitting methods and distribution models based on one-year pelagic fish data from Daya Bay, China. Our empirical results showed that maximum likelihood estimation (MLE) is more suitable than traditional normalized biomass spectra (NBS), and that a power law is not always the best model when using MLE. Moreover, we found significant size structure variation in different seasons. Principal component analysis (PCA) and linear mixed effects model (LMM) results showed that temperature was the major factor in seasonal environmental variation, and fish migration might be the essential response strategy causing size structure changes. The estimated exponents and nonlinear structure indicated that the Daya Bay is under intensive human impact. Our results suggest that MLE methods are recommended in future size-based studies, and that environmental variation and migration patterns are crucial in understanding seasonal community structure changes.

Assessment of fish communities in a Mediterranean MPA: Can a seasonal no-take zone provide effective protection?

The efficacy of a Mediterranean Marine Protected Area (National Marine Park of Zakynthos – NMPZ, Ionian Sea, Greece) that implements a seasonal no-take zone as part of its management scheme was assessed using fish data collected in situ with underwater visual census. Sampling was conducted at two habitat types (Posidonia oceanica meadows and rocky reefs) that occur at sites of different protection level with respect to fisheries (high protection: seasonal no-take zone within the MPA; intermediate: zones within the MPA where small-scale fishing is allowed; none: areas outside the MPA, where all types of fishing are allowed, including trawlers, purse seiners, and recreational fishing). The data were used to examine the effects of protection level and habitat type on community parameters, trophic structure and functional diversity of fish populations that occupy the upper sublittoral zone. Overall, habitat type had a more pronounced effect than protection level on all investigated parameters. Biomass, density and number of fish species with low commercial value were higher in sites of intermediate protection, but no substantial fisheries-related ecological benefits were detected for targeted fish in the seasonal no-take zone. Conducted 8 years after the initial implementation of the seasonal no-take management scheme, our study suggests that existing fishing regulations in the NMPZ provide some measurable effects, but fall short of maintaining sufficient protection for the recovery of apex predators or other commercially important fish species. A revision of the existing zoning system to include permanent no-take zones, alongside the regulation of professional fishing and all extractive activities in the rest of the MPA, are strongly encouraged in order to enhance the effectiveness of fisheries management.

Moving from multiple pass depletion to single pass timed electrofishing for fish community assessment in wadeable streams

Area-delineated multiple-pass depletion electrofishing (ADEF) can be resource-intensive. It may not capture fish community state when resource limitations mean that the number of sites sampled in a system is insufficient to account for ecological heterogeneity. Rapid assessment techniques such as single-pass timed electrofishing could be more efficient and support increased sample size, but it is important to understand how resulting catches will relate to existing ADEF data/time series. Paired ADEF (3-pass) and single-pass timed (10-min) electrofishing (TEF) samples were collected for sites in the River Barrow catchment (Ireland) in 2015. Paired samples were used to derive species-specific size-based conversion factors (CF) for extrapolating TEF catch up to a predicted ADEF Pass 1 catch. Applying these CF to a set of independent ‘validation’ TEF samples (2008–2013) produced fish catch estimates similar to observed ADEF Pass 1 catches (2008–2015). Species size-distributions in extrapolated TEF data were also similar to those in paired ADEF Pass 1 samples. Pass 2 and Pass 3 catches by species were then predicted from extrapolated validation TEF catches using a regression model. Cumulative catch curves fitted to these predicted catches were similar to those fitted to observed ADEF catch data for most species. TEF samples provide estimates of fish species catch and size-distribution that can be extrapolated following a simple protocol and compared with ADEF data for small streams measuring up to 10 m in width.

Fish community assessment with eDNA metabarcoding: effects of sampling design and bioinformatic filtering

Species richness is a metric of biodiversity that represents the number of species present in a community. Traditional fisheries assessments that rely on capture of organisms often underestimate true species richness. Environmental DNA (eDNA) metabarcoding is an alternative tool that infers species richness by collecting and sequencing DNA present in the ecosystem. Our objective was to determine how spatial distribution of samples and “bioinformatic stringency” affected eDNA-metabarcoding estimates of species richness compared with capture-based estimates in a 2.2 ha reservoir. When bioinformatic criteria required species to be detected only in a single sample, eDNA metabarcoding detected all species captured with traditional methods plus an additional 11 noncaptured species. However, when we required species to be detected with multiple markers and in multiple samples, eDNA metabarcoding detected only seven of the captured species. Our analysis of the spatial patterns of species detection indicated that eDNA was distributed relatively homogeneously throughout the reservoir, except near the inflowing stream. We suggest that interpretation of eDNA metabarcoding data must consider the potential effects of water body type, spatial resolution, and bioinformatic stringency.

Comparison of nine different methods to assess fish communities in lentic flood-plain habitats.

This study compares the effectiveness and representativeness of electrofishing, snorkelling, seining, baited lift netting, multi-mesh gillnetting, baited fish traps, fyke netting, angling and longline fishing, considering three typical lentic flood-plain habitats at different times of day. Electrofishing was by far the most effective method yielding highest species richness, species trait representation and catch per unit of effort (CPUE), followed by seining. For single species like dace Leuciscus leuciscus, European ruffe Gymnocephalus cernua, common bream Abramis brama and silver bream Blicca bjoerkna, seining was more effective than electrofishing. With both methods, some species were more consistently caught during night, dusk or dawn than during daylight. All other methods tested cannot be generally recommended for fish community assessments in shallow backwaters due to their low representativeness of species inventory and generally low CPUE. Based on these results, electrofishing of 30 m transect replicates at different times of day for monitoring the fish community in shallow backwaters, can be recommended, enabling the maximum possible comparability to adjacent river habitats. Seining should be considered as an alternative if accessibility of habitats is restricted or electrofishing is prohibited. The 25 species detected in the backwaters also suggest that these habitats contribute a large proportion of fish diversity and should be included in standard assessments of river ecological status.

Submerged oceanic shoals of north Western Australia are a major reservoir of marine biodiversity

This paper provides a first assessment of fish communities associated with the submerged oceanic banks and shoals in north-west Australia. Until recently, little was known about these deeper and more inaccessible reefs. The mesophotic coral-reef habitats (20–80 m) were a major reservoir of marine biodiversity, with unique and exceptionally high fish diversity and abundance. Species richness in the study region was 1.4 times, and abundance almost twice, that recorded for similar mesophotic habitats on the Great Barrier Reef in north-east Australia. A review of the published literature revealed that Australia’s NW oceanic shoals support the highest fish species richness reported for mesophotic reefs to date. We made regional comparisons of fish community structure (species composition, richness and abundance) and assessed the influence of depth, substrate and location. The presence of consolidated calcareous reef, depth and aspect (a surrogate for exposure) had the greatest influence on species richness. In contrast, aspect and the presence of benthic biota had the greatest influence on fish abundance. Sites most exposed to the prevailing currents (facing north-east) had lowest fish abundance, while highest abundances were recorded on moderately exposed sites (along the north-west and south-east edges). The most abundant species were small (Pomacentrus coelestis) and large (Naso hexacanthus) planktivorous fish. Currently, 29.3% of NE Australia mesophotic reefs are within no-take management zones of the Great Barrier Reef. In contrast, just 1.3% of the NW oceanic shoals are designated as no-take areas. The location and extent of mesophotic reefs remain poorly quantified globally. Because these habitats support significant biodiversity and have the potential to act as important refugia, understanding their extent is critical to maintaining coral-reef biodiversity and resilience and supporting sustainable management.

Struktutr Komunitas Ikan dan Tutupan Karang di Area Biorock Desa Pemuteran, Buleleng, Bali

Biorock is new method of coral reef rehabilitation. Today, the structure Biorock been made in various shapes and sizes. Therefore, assessment of reef fish communities and coral cover on the artificial reef Biorock of different sizes are needed as a as the basic information and the utilization of the results of the conservation area. From this research, it is known that the six Biorock structure obtained reef fish composition consisting of 18 Family and 45 fish species and abundance of total 2065 individuals. In accordance with the classification of diversity index Shannon - wiener all sizes Biorock the research object falls into the range of values diversity moderately 1.57 - 2.95. The results of the uniformity index show that in every size Biorock has equal distribution of species. From the results of the dominance of index calculation (C) is included in the low category. Where in any size Biorock not happen domination by a single species. In all sizes Biorock have value mengindikasinkan that coral is in good shape. The highest coral cover in sequence contained in the structure of Small-sized Biorock 1, 1 medium, 2 Large, 2 Small, 2 Medium, and 1 Large. From analysis using Bray-Curtis similarity index gained 2 groups Biorock structures that have similar types of fish encountered. The first group is the first Large-sized Biorock structure, Large 2, and the medium 1. The second group is the structure of Small-sized Biorock 1, 2 medium and 2 Small.