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In European countries, electrofishing by wading is widely applied to sample fish communities in rivers. In deeper rivers, electrofishing even by boat is considered only suitable to sample the shallow, littoral zone. The monitoring sampling methods concerning fish in the Bulgarian sector of the Danube River are electrofishing and drifting gill nets. The scope of this study is to compare different fish sampling approaches in order to identify the most appropriate for this sector, which could be also applicable for the whole lower Danube River stretch. According to the results, concerning Lower Danube River upstream of its delta, fish monitoring by boat electrofishing during day and night altogether with beach seine should be used; drifting gill nets could contribute valuable data in some cases. These sampling methods could also unveil the basic characteristics of alien fish populations. [ABSTRACT FROM AUTHOR] more...

There is growing international concern about declines in populations of anguillid eels, resulting in their inclusion in the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. Monitoring the population dynamics of these species is often challenging, however, owing to their broad distributions and complex, catadromous life histories.Whether environmental DNA (eDNA) analysis could be used to monitor the spatial distribution of anguillid eels in rivers was investigated by conducting basin‐scale surveys of Japanese eels, Anguilla japonica Temminck & Schlegel, 1846, in 10 rivers in Japan, and comparing the results obtained using eDNA analysis with the results obtained using the electrofishing method. Moreover, the relationship between the eDNA concentration and the abundance and biomass of Japanese eels was examined.The eDNA of Japanese eels was detected at 56 (91.8%) of the 61 study sites from which individuals were collected by electrofishing, and at an additional 35 sites where individuals were not directly collected. This indicates that eDNA analysis has a greater sensitivity for detecting the presence of eels, making it a powerful tool for monitoring the spatial distribution of anguillid eels in rivers.A significant, but weak, positive relationship between the eDNA concentration and the abundance and biomass of Japanese eels was also found, suggesting that eDNA analysis may be useful for estimating the abundance and biomass of anguillid eels in rivers.This is the first study to demonstrate the potential usefulness of eDNA analysis for estimating the spatial distribution, abundance, and biomass of Japanese eels in rivers. eDNA analysis will allow anguillid eel populations to be monitored over large spatial and temporal scales using a consistent protocol, with reduced time and effort compared with conventional techniques, providing invaluable information for managing populations of these endangered species. [ABSTRACT FROM AUTHOR] more...

Assessing the conservation status of a species is strongly dependent upon data on species distribution and abundance. With the emergence of novel methods for species monitoring – such as the use of environmental DNA (eDNA) – monitoring success can be improved at reduced expenditure in the field, particularly in remote regions and terrains where access is difficult or dangerous.The highly endangered crocodile lizard (Shinisaurus crocodilurus Ahl, 1930) inhabits fragmented sites of the remaining evergreen forest with running water systems in a narrow distribution range in southern China and north‐east Vietnam. Crocodile lizards spend most of the day within or above water bodies, which are commonly remote and inaccessible.To monitor recent spatial occurrences, and to confirm the persistence or extinction of previously reported populations (especially in heavily altered habitats), the suitability of using eDNA and quantitative polymerase chain reaction (qPCR) was tested as an alternative method for monitoring this semiaquatic lizard.To assess the accuracy and limitations of this method, eDNA results from the field were compared with eDNA data from mesocosms and census data on the actual abundance of this species in the field.Environmental DNA of the crocodile lizard was detected in all of the positive controls, and in four of six natural sites; thus, all data collected using traditional field surveys were confirmed with eDNA results.eDNA monitoring was found to be a reliable method for assessing the viability of populations; we suggest that it should be developed as a tool for efficient wildlife management, particularly under difficult field and funding conditions. [ABSTRACT FROM AUTHOR] more...

Highlights • Citizen science based data enables higher temporal and spatial resolution. • Citizen science using focus groups provides highly useful cost-efficient monitoring. • Fish indicators for system health can be generated from this type of data. • Through capacity building, fishermen became ambassadors for responsible fishing practices and healthy ecosystems. Abstract In response to repeated complaints from recreational and commercial coastal fishermen about declining fishing opportunities in inner Danish waters, focus was directed to inshore fish stocks. However, without data targeting inshore areas, it was not possible to investigate potential changes in fish distribution or abundances, or their causes. As a first step, a voluntary catch registration system was initiated in 2002, in collaboration with locally organized recreational fishermen. Using citizen science as a methodology, scientists and the fishermen developed a protocol for data collection, which the fishermen then implemented. The aim was to establish regular monitoring of fish catches from gill net and fyke net fisheries in coastal waters around Denmark in order to provide data that could inform management. After three years, during which time recreational fishermen could use their own gear and fish where they normally fished, the data was evaluated. As a result, the fishing method was switched in 2005 to fixed gears and fixed positions, to enable comparison between areas, years and season. The project has been very successful in recruiting highly motivated fishermen, who register their entire catch regularly. The time-series of data spans more than a decade and covers over 16,000 instances of fishing. The data from this project are now being used to create coastal fish indicators for managers to assess environmental status at a regional scale. Here we present an analysis of a subset of the data on one species, the European flounder (Platichthys flesus), to illustrate how the spatial and seasonal coverage can be utilized further for investigation of coastal ecosystems and to inform management. [ABSTRACT FROM AUTHOR] more...

Abstract Information is central to the assessment and regulation of fisheries, yet underreporting remains a persistent problem, especially in the small-scale and developing country fisheries. Private actors, using a variety of enumeration approaches and technologies, have started to supplement government enumeration programs to meet a range of reporting obligations. This paper introduces a social practices approach to understand the response of fishers to private enumeration interventions. We base our analysis on the introduction of landing enumeration, fisher logbooks and Spot Trace devices by the Indonesian NGO, Masyarakat dan Perikanan Indonesia (MDPI) in a Fair Trade USA certified handline tuna fishery in Eastern Indonesia. The results show how a social practices approach offers a grounded understanding of responses to monitoring interventions that extends beyond conventional analyses of fishery-dependent data collection. The paper concludes that understanding data collection as a set of socially mediated practices that intervene in established fishing and landing practices can help to improve the design of fisheries data collection. [ABSTRACT FROM AUTHOR] more...

Accuracy in estimating occupancy of a threatened species is important for conservation but false absences bias many monitoring programs. Imperfect detection is especially relevant to surveys of rare wetland fishes which are often small-bodied and cryptic. Many factors influence probability of detection, including fish size and abundance, habitat characteristics and sampling devices. Imperfect detection can be addressed by accounting for probability of detection when estimating occupancy by modelling detection/non-detection data collected in replicate surveys. Three ecological specialists were once common in habitats associated with Lake Alexandrina at the terminus of the Murray-Darling Basin, Australia. The threatened Murray Hardyhead (Craterocephalus fluviatilis), Southern Pygmy Perch (Nannoperca australis) and Yarra Pygmy Perch (N. obscura) are now rare in the region following population collapses during a prolonged drought, and ongoing monitoring aims to assess their statuses for management purposes. This study compares probability of detection of the rare wetland fishes and cohabiting species during 2 years of multi-species monitoring using contrasting sampling devices (fyke and seine). The findings suggest large variations in estimated probability of detection can occur between devices for Murray Hardyhead and Southern Pygmy Perch. Yarra Pygmy Perch was undetected during the study. Overall, the findings show multi-species monitoring programs using a single sampling device may wrongly estimate the occupancy of a target fish. By accounting for imperfect detection, multi-species monitoring programs will improve inferences regarding population status, recovery and habitat quality of fishes to more accurately inform wetland management. [ABSTRACT FROM AUTHOR] more...

Highlights • An oyster reef complex consisting of reef mounds and corridors was constructed. • High oyster densities were observed at the restored reef complex. • Nekton recruited to the restored complex quickly after construction. • Nekton use of between-reef corridors suggest these are important design elements. • The complex reef design likely contributed to the high level of project success. Abstract Oyster reefs are important foundational habitats and provide many ecosystem services. A century of habitat degradation has resulted in substantial reductions in the extent and quality of oyster reefs in many estuaries, thus spurring restoration efforts. In this study, a 1.5 ha oyster reef complex was constructed in Copano Bay, Texas to restore habitat for oysters and associated fauna. Oysters and resident and transient fishes and crustaceans were monitored at the restored reef as well as at nearby natural oyster reef and unrestored bottom (i.e., dense mud with shell hash) habitats for two years following reef construction. The restored reef had substantial oyster recruitment and growth, with oyster abundance and size comparable to nearby habitats within the first year. Resident and transient fauna communities recruited to the restored reef within six months post-construction, and abundance and diversity were comparable to nearby habitats. Significant changes observed in oyster densities between the first and second year post-restoration demonstrate the importance of monitoring over multiple years to capture multiple recruitment cycles and growth to market size. Nekton densities did not change significantly after the first year, but changes in community assemblages were observed through the end of the study. The high densities of oysters and resident nekton relative to other studies indicate that this restoration project was successful in restoring suitable habitat. The design of the reef complex, consisting of relatively high-relief reef mounds and deeper corridors, likely contributed to the relatively high oyster and nekton densities observed in this study. Overall, the restored reef in this study showed tremendous near-term success in providing important ecological functions associated with habitat provision and oyster production. [ABSTRACT FROM AUTHOR] more...

There are three main themes in this self-reflective essay, and I hope they are thought-provoking without being pretentious. The first is the topic of scientific specialization. How do we steer a course between being a dilettante on one hand, dabbling in everything without making major contributions in any field, and on the other hand being a specialist who digs deeply but too narrowly? The second theme is the concept of specialization with respect to place, and the study of natural history. It can be incredibly rewarding, both personally and professionally, to develop a rich ecological understanding of a particular place such as a field station. However, this requires a great commitment of time, and it reduces mobility and experience elsewhere. The third theme is the importance of mentoring and the transfer of encouragement and opportunity from one cohort to the next. I will address these three themes in this order but they are closely linked to each other, making the separation somewhat artificial. [ABSTRACT FROM AUTHOR] more...

Rivers in the arid Western United States face increasing influences from anthropogenic contaminants due to population growth, urbanization, and drought. To better understand and more effectively track the impacts of these contaminants, biologically-based monitoring tools are increasingly being used to complement routine chemical monitoring. This study was initiated to assess the ability of both targeted and untargeted biologically-based monitoring tools to discriminate impacts of two adjacent wastewater treatment plants (WWTPs) on Colorado's South Platte River. A cell-based estrogen assay ( in vitro , targeted) determined that water samples collected downstream of the larger of the two WWTPs displayed considerable estrogenic activity in its two separate effluent streams. Hepatic vitellogenin mRNA expression ( in vivo , targeted) and NMR-based metabolomic analyses ( in vivo , untargeted) from caged male fathead minnows also suggested estrogenic activity downstream of the larger WWTP, but detected significant differences in responses from its two effluent streams. The metabolomic results suggested that these differences were associated with oxidative stress levels. Finally, partial least squares regression was used to explore linkages between the metabolomics responses and the chemical contaminants that were detected at the sites. This analysis, along with univariate statistical approaches, identified significant covariance between the biological endpoints and estrone concentrations, suggesting the importance of this contaminant and recommending increased focus on its presence in the environment. These results underscore the benefits of a combined targeted and untargeted biologically-based monitoring strategy when used alongside contaminant monitoring to more effectively assess ecological impacts of exposures to complex mixtures in surface waters. [ABSTRACT FROM AUTHOR] more...

Abstract: We present a performance evaluation of environmental DNA (eDNA) metabarcoding with MiFish‐U/E primers to investigate local and regional diversities of stream fish species to examine potential effectiveness, limits and future remedies of this technique in large‐scale monitoring. We hypothesised that eDNA inferences are more consistent with fish assemblages observed upstream than downstream due to a directional flow of river water. River water was sampled at 102 sites in 51 rivers around Lake Biwa in the central part of Honshu Island, Japan, within 10 person‐days, and fish species compositions inferred from eDNA and existing observational data were compared. Observation sites were chosen from the observational data that were within a certain distance (buffer range) of a water‐sampling site along a river trajectory. The hypothesis of the detection bias of eDNA towards upstream assemblage was tested by comparing results with all of the observational data, data from a higher elevation and data from a lower elevation. The Jaccard dissimilarity index was plotted between the observational data and the eDNA estimates against the buffer range; the buffer range with minimum dissimilarity was chosen. When using existing observational data from within 6 km upstream of the eDNA sampling sites, the eDNA results were the most consistent with the observational data and inferred 86.4% of the species reported (38/44), as well as two additional species. eDNA results also showed patterns consistent with known upstream–downstream turnover of related species and biogeographical assemblage patterns of certain species. Our 10‐person‐days survey using the metabarcoding technique enabled us to obtain as much regional fish diversity data including the hypothesised pattern of eDNA detection with an upstream bias as the accumulated observational data obtained through greater amounts of time, money and labour. The problems regarding false‐positive/negative detection were suggested in our survey; however, these should be decreased or removed by modifying the sampling methods and experimental procedures in future works. Therefore, we concluded this new tool to enable monitoring that has never been implemented, such as cross‐nation, and even whole‐Earth monitoring with the data at yearly, seasonal or finer temporal scales. [ABSTRACT FROM AUTHOR] more...

Abstract: Many studies stress the usefulness of fish calls as effective indicators of distinct species occurrence. However, most of these studies have been undertaken in a given area and during restricted periods of time. There is a need to show passive acoustic monitoring is a reliable method to study vocal species over space and time. This study aims to use passive acoustic methods to follow the brown meagre Sciaena umbra at relevant temporal and spatial scales. Specimens of S. umbra were recorded in both aquarium and in the field. In situ recordings were made at two regions (Corsica and Sardinia) during four summers (2008–2012–2013–2015). Temporal and frequency parameters of the fish calls were collected by different teams and compared to test the ability to unequivocally identify the fish sound. The comparison between our data and the bibliography highlights the capability to identify S. umbra during a period of 17 years in different Mediterranean regions, clearly supporting the usefulness of acoustic monitoring to discover and protect aggregation sites of this endangered species. The sound producing mechanism in S. umbra consists of high‐speed sonic muscles surrounding dorsally the posterior end of the swim bladder, which can explain the low acoustic variability that helps in the species identification. Similar mechanisms are found in other Sciaenidae, suggesting that a similar conclusion can be drawn for many other adult sciaenids that could be used as sentinel species. This study should be of high interest to policymakers and scientists because it shows passive acoustic can be confidently used in resource management. [ABSTRACT FROM AUTHOR] more...

Understanding trends in the diverse resources provided by large rivers will help balance tradeoffs among stakeholders and inform strategies to mitigate the effects of landscape scale stressors such as climate change and invasive species. Absent a cohesive coordinated effort to assess trends in important large river resources, a logical starting point is to assess our ability to draw inferences from existing efforts. In this paper, we use a common analytical framework to analyze data from five disparate fish monitoring programs to better understand the nature of spatial and temporal trends in large river fish assemblages. We evaluated data from programs that monitor fishes in the Colorado, Columbia, Illinois, Mississippi, and Tallapoosa rivers using non-metric dimensional scaling ordinations and associated tests to evaluate trends in fish assemblage structure and native fish biodiversity. Our results indicate that fish assemblages exhibited significant spatial and temporal trends in all five of the rivers. We also document native species diversity trends that were variable within and between rivers and generally more evident in rivers with higher species richness and programs of longer duration. We discuss shared and basin-specific landscape level stressors. Having a basic understanding of the nature and extent of trends in fish assemblages is a necessary first step towards understanding factors affecting biodiversity and fisheries in large rivers. [ABSTRACT FROM AUTHOR] more...

Accurate taxonomy, population demography, and habitat descriptors inform species threat assessments and the design of effective conservation measures. Here we combine published studies with new genetic, morphological and habitat data that were collected from seahorse populations located along the European and North African coastlines to help inform management decisions for European seahorses. This study confirms the presence of only two native seahorse species ( Hippocampus guttulatus and H. hippocampus) across Europe, with sporadic occurrence of non-native seahorse species in European waters. For the two native species, our findings demonstrate that highly variable morphological characteristics, such as size and presence or number of cirri, are unreliable for distinguishing species. Both species exhibit sex dimorphism with females being significantly larger. Across its range, H. guttulatus were larger and found at higher densities in cooler waters, and individuals in the Black Sea were significantly smaller than in other populations. H. hippocampus were significantly larger in Senegal. Hippocampus guttulatus tends to have higher density populations than H. hippocampus when they occur sympatrically. Although these species are often associated with seagrass beds, data show both species inhabit a wide variety of shallow habitats and use a mixture of holdfasts. We suggest an international mosaic of protected areas focused on multiple habitat types as the first step to successful assessment, monitoring and conservation management of these Data Deficient species. [ABSTRACT FROM AUTHOR] more...

Passive acoustic detectors are widely used for monitoring distribution of cetaceans. Autonomous visual methods are less frequently employed; they are limited to detections during daylight and good weather, but offer potential advantages due to certainty of species' identification and longevity of deployment. To compare performance of acoustic and visual methods, temporal changes in distribution of southern right whales, Eubalaena australis, were monitored in the remote sub-Antarctic Auckland Islands (50°31′S, 166°16′E). A time-lapse camera was deployed for 2 years from August 2010, taking an image every 70 min. The presence of whales was scored for each image taken during daylight ( n = 8295). A passive acoustic recorder was deployed in August 2011, recording for 3.75 min every hour until battery life expired after 10 months. Each recording ( n = 6978) was aurally reviewed. Both methods revealed a similar seasonal distribution; maximum detection rates were in the austral winter and no whales were detected in January or February. However, at the peak of right whale occurrence, the proportion of samples with whales detected was much higher for the acoustic recorder (93.9% in August) than the time-lapse camera (14.8%). A generalised additive model fitted to the visual data revealed significant effects of sea state and visibility. Acoustic detection rates were higher, probably because detection range is greater, and less affected by weather. The solar-powered time-lapse camera system, however, functioned effectively for much longer. We discuss the relative merits of visual and acoustic detectors and attempt to draw conclusions about their efficacy for different focal species and monitoring locations. [ABSTRACT FROM AUTHOR] more...

The reproductive biology of Centropomus pectinatus is described from an artisanal fish landings collaborative monitoring programme between May 2012 and April 2013 in estuarine waters in north-eastern Brazil. The total length ( LT) at which 50% are mature was 24 cm, corresponding to 37·7% of the maximum recorded LT. Gonado-somatic indices were variable, but highest values were in June and August 2012. Length-frequency distributions showed male dominance in smaller length classes (15-30 cm) and females in larger length classes (>30 cm). [ABSTRACT FROM AUTHOR] more...

Fishes display a wide variation in their physiological responses to stress, which is clearly evident in the plasma corticosteroid changes, chiefly cortisol levels in fish. As a well-known indicator of fish stress, a simple and rapid method for detecting cortisol changes especially sudden increases is desired. In this study, we describe an enzyme-functionalized label-free immunosensor system for detecting fish cortisol levels. Detection of cortisol using amperometry was achieved by immobilizing both anti-cortisol antibody (selective detection of cortisol) and glucose oxidase (signal amplification and non-toxic measurement) on an Au electrode surface with a self-assembled monolayer. This system is based on the maximum glucose oxidation output current change induced by the generation of a non-conductive antigen-antibody complex, which depends on the levels of cortisol in the sample. The immunosensor responded to cortisol levels with a linear decrease in the current in the range of 1.25–200 ng ml −1 (R=0.964). Since the dynamic range of the sensor can cover the normal range of plasma cortisol in fish, the samples obtained from the fish did not need to be diluted. Further, electrochemical measurement of one sample required only ~30 min. The sensor system was applied to determine the cortisol levels in plasma sampled from Nile tilapia ( Oreochromis niloticus ), which were then compared with levels of the same samples determined using the conventional method (ELISA). Values determined using both methods were well correlated. These findings suggest that the proposed label-free immunosensor could be useful for rapid and convenient analysis of cortisol levels in fish without sample dilution. We also believe that the proposed system could be integrated in a miniaturized potentiostat for point-of-care cortisol detection and useful as a portable diagnostic in fish farms in the future. [ABSTRACT FROM AUTHOR] more...

Background: Passive integrated transponder (PIT) tags have been used to document and monitor the movement, behavior, or survival of numerous species of fishes. Data on short- and long-term survival and tag retention are needed before initiating studies using PIT tags on a new species or life stage. We evaluated the survival and tag retention of 153 metamorphosing juvenile sea lamprey Petromyzon marinus tagged with 12-mm PIT tags on three occasions using a simple surgical procedure. Results: Tag retention was 100 and 98.6% at 24 h and 28-105 days post-tagging. Of the lamprey that retained their tags, 87.3% had incisions sufficiently healed to prevent further loss. Survival was 100 and 92.7% at 24 h and 41-118 day post-tagging with no significant difference in survival between tagged and untagged control lamprey. Of the 11 lamprey that died, four had symptoms that indicated their death was directly related to tagging. Survival was positively correlated with sea lamprey length. Conclusions: Given the overall high level of survival and tag retention in this study, future studies can utilize 12-mm PIT tags to monitor metamorphosing juvenile sea lamprey movement and migration patterns. [ABSTRACT FROM AUTHOR] more...

Underwater stereo-video systems are widely used for counting and measuring fish in aquaculture, fisheries, and conservation management. Length measurements are generated from stereo-video recordings by a software operator using a mouse to locate the head and tail of a fish in synchronized pairs of images. This data can be used to compare spatial and temporal changes in the mean length and biomass or frequency distributions of populations of fishes. Since the early 1990s stereo-video has also been used for measuring the lengths of fish in aquaculture for quota and farm management. However, the costs of the equipment, software, the time, and salary costs involved in post processing imagery manually and the subsequent delays in the availability of length information inhibit the adoption of this technology. We present a semi-automatic method for capturing stereo-video measurements to estimate the lengths of fish. We compare the time taken to make measurements of the same fish measured manually from stereo-video imagery to that measured semi-automatically. Using imagery recorded during transfers of Southern Bluefin Tuna (SBT) from tow cages to grow out cages, we demonstrate that the semi-automatic algorithm developed can obtain fork length measurements with an error of less than 1% of the true length and with at least a sixfold reduction in operator time in comparison to manual measurements. Of the 22 138 SBT recorded we were able to measure 52.6% (11 647) manually and 11.8% (2614) semi-automatically. For seven of the eight cage transfers recorded there were no statistical differences in the mean length, weight, or length frequency between manual and semi-automatic measurements. When the data were pooled across the eight cage transfers, there was no statistical difference in mean length or weight between the stereo-video-based manual and semi-automated measurements. Hence, the presented semi-automatic system can be deployed to significantly reduce the cost involved in adoption of stereo-video technology. [ABSTRACT FROM AUTHOR] more...

Background. Fish-based indices for evaluation of river ecosystem quality have been used since the 1980s, when the Index of Biotic Integrity (IBI) was first introduced. Assessment of the ecological status of rivers, based on fish assemblages is required by the Water Framework Directive. During last 15 years a number of national assessment methods based on fish fauna were developed. The recently designed tool for fish-based assessment of ecological status (EFI+IBI_PL) applied in river monitoring in Poland is presented in this paper. Material and methods. The new European Fish Index EFI+ is a multimetric tool consisting of two specific indices, each with two metrics developed separately for salmonid- and cyprinid-river zones. Those metrics were used in the European intercalibration process to validate national methods. However, the original EFI+ method is not adequate to some lowland river types (physical-factor classification), so it was complemented by a typespecific modification of the Index of Biotic Integrity (IBI_PL). The method was tested on fish data from 493 sites located in 431 surface water bodies sampled in 2011-2012 according to the CEN standard 14011. Results. The EFI+ index was adapted to the specificity of Polish rivers by eliminating some inconsistences of the ecoregion division and problems related to the lack of the Dniester River in the EFI+ software and presented in this paper as EFI+PL. The index of diadromous fish occurrence (D) was also adapted from an original EFI+ method and used as a supplementary assessment tool. Specific IBI metrics were developed for large lowland rivers (with sandy or gravel bottom substrate), organic rivers (flowing through peat areas), and rivers connecting lakes (with the presence or lack of salmonid fish species). A software tool for indices calculation was also developed. The method combination (EFI+IBI_PL) was than tested on a set of 493 monitoring sites sampled in 2011-2012. Both indices classified the highest percentage of sites into moderate ecological state/potential class, but for IBI_ PL this percentage was much higher than for EFI+. Percentage of sites classified to good ecological status or high ecological potential by IBI_PL index were lower than for EFI+. The analysis indicates the consistence of classification for 77% of sites to high/good and below good ecological status by the EFI+PL/IBI_PL method and pressure index. Conclusion. The results of a two-years monitoring program show that the combination of modified EFI+ and IBI methods can be applied as a tool for river ecological status assessment in Poland, however some further method modifications are needed. [ABSTRACT FROM AUTHOR] more...

Invasive Cichla populations in the São João River basin were genetically analysed and compared with Cichla populations from other neotropical hydrographic basins. Polymorphic sequences within the mitochondrial DNA D-loop region confirmed the introduction of different populations to the regions under analysis. Cichla kelberi was introduced to the Juturnaíba reservoir and a downstream area of the São João River, with Cichla monoculus restricted to downstream river areas. Results from this study will be useful for monitoring invasive Cichla populations in the coastal basin since it elucidated the taxonomic units in the reservoir and an areas downstream. [ABSTRACT FROM AUTHOR] more...

Undetected but underlying biases in model parameterization strongly reduce the reliability and value of assessments of data-poor fisheries. We explore the effects of missing and misunderstood data on single-species stock assessments used to provide management advice. From 2006 to 2014, the Colombian government monitored landings of small-scale fisheries. During the same period, communities implemented a participatory monitoring program in the Central Guajira region. We found that the two data sources gave different results for the population status of the highest-valued fish, lane snapper ( Lutjanus synagris ), and the largest-landed species, white grunt ( Haemulon plumierii ). Recordings of landing points by the government monitoring program led to year-to-year underestimations and therefore misconceptions regarding population status and fishery trends. Overexploited and underexploited population statuses were seen to arise from the same fishing pressure as a result of the interplay between natural mortality and erroneous estimates of fishing mortality. The tested von Bertalanffy growth parameters affected the exploitation level, but not the population status, of the species. When data from the participatory monitoring program were incorporated, higher landings and a more severe overfishing trend emerged for both species. The management scenarios simulated using the best verified data available provided reasonable advice for recovering the lane snapper and white grunt populations. Furthermore, simulation of management measures sustained the employment and incomes of fishers. Our findings indicate that participatory monitoring should be incorporated into the assessment and management of data-poor resources. [ABSTRACT FROM AUTHOR] more...

Length limits have been implemented by fisheries management agencies to achieve population density, size structure, and angler satisfaction objectives. By redirecting harvest towards or away from particular length- or age-groups, length limits rely on harvest by anglers to maintain a population at or near a desired state. The fish population changes that follow the implementation of harvest regulations may take several years to manifest, so long-term monitoring may be needed to adequately evaluate length limits. We used an innovative application of cluster analysis to facilitate evaluation of the effects of three consecutive length limits on a population of Largemouth BassMicropterus salmoidesover a 28-year period in Ross Barnett Reservoir, Mississippi. A 13–16-in protected slot length limit (10 years), followed by a 15-in minimum length limit (MLL; 11 years), followed by a 12-in MLL (7 years) failed to restructure the Largemouth Bass population due to what we suggest was the expansion of a voluntary catch-and-release attitude that started in the first decade of the study period. Various population metrics shifted towards values expected in an unharvested population, and the observed shifts can be attributed to a harvest deficit created by the prevailing catch-and-release attitude. Largemouth Bass harvest regulations may no longer be relevant in many waters. The utility of regulations for restructuring Largemouth Bass populations is largely dependent on harvesting attitudes that vary geographically, depending on cultural characteristics and demographics. Received September 15, 2016; accepted March 15, 2017 Published online May 4, 2017 [ABSTRACT FROM AUTHOR] more...

There is international recognition for greater inclusion of recreational fisheries catch data in species, fisheries and ecosystem assessments. Recreational charter fisheries provide important social services and contribute to total species catches. This study compares and validates industry logbook catch and effort data (1,357 trips) against observer data (154 trips) across six ports in a recreational charter fishery in eastern Australia. The mean numbers of clients and fishing effort (hours) per trip varied inconsistently between data sources and among ports. Logbooks did not adequately report released catches, and the mean number of species retained per trip was consistently underestimated in logbooks compared to observer data. For both data sources, catch rates of total individuals and key species displayed similar trends across different units of effort; catch per hour, client, client/hour and trip. The mean catch rates of total individuals and most key species, except those retained for bait, were similar across data sources, as were estimates of total fleet harvests. The length compositions of retained catches of some key species displayed truncation of larger organisms in the observer data whereas other species did not. Despite the shortcomings of the logbook data, future fishery and species monitoring strategies could include industry and observer data sources. [ABSTRACT FROM AUTHOR] more...

The CEN (2005) methodology for fish monitoring of mesotrophic to eutrophic Mediterranean lakes was evaluated. The contribution of gillnet (benthic and pelagic) and electrofishing catches on species richness was examined. Additionally, the contribution of benthic gillnet sampling effort on species richness and precision of catch-per-unit-effort (CPUE) estimates, considering both number of specimens (ΝPUE) and biomass (BPUE), was assessed. Subsequently, the impact of reduction in sampling effort on the parameters mentioned above was estimated and the effort needed to acquire the desired precision level considering different NPUE values was modelled. The use of different sampling gears was found to contribute to species richness assessment, while sampling effort could be reduced in the deepest zones of the lakes. The resultant model can reliably guide assessment of the sampling effort required in the Mediterranean and central European lakes with high fish densities. [ABSTRACT FROM AUTHOR] more...

Given the scientific consensus that climate change is impacting biodiversity, estimates of future climate change effects on stream communities and assessments of potential biases are necessary. Here, we propose a simple technique to approximate changes in invertebrate and fish biomonitoring results. Taxa lists for 60 (invertebrate) and 52 (fish) sites were each modified by 10 multipliers as stepwise 5% or 10% changes in abundances to simulate potential climate-change severity, reflecting increasing climate change effects. These 10 multipliers were based on the stream zonation preference for invertebrates and the Fish Region Index (FRI) values for fish, both reflecting the longitudinal gradient present in river ecosystems. The original and modified taxa lists were analyzed using the standard assessment software for the particular group, followed by analysis of key biomonitoring metrics. For invertebrates, our simulations affected small good quality streams more often negatively while large poor mountain streams showed a tendency to improve. Forty percent of the invertebrate data sites showed a change in the final ecological assessment class when using the multipliers, with the poor quality sites changing more often. For fish, metric changes were variable, but the FRI ratio showed mostly positive responses, i.e., a shift in FRI towards downstream communities. The results are discussed as an example that facilitates the interpretation of potential climate-change effects with varying severity. Further, we discuss the simplified approach and implications for assessment from climate change induced range shifts. [ABSTRACT FROM AUTHOR] more...

Bait is an integral part of coastal life, but is perceived as a low-value resource as fisheries are data-limited, locally focussed and largely unregulated even though the ecological impacts of collection are considerable. An empirical assessment of three UK-based ragworm fisheries combined with an analysis of published literature has produced the first global assessment of polychaete bait fisheries. The five most expensive (retail price per kg) marine species sold on the global fisheries market are polychaetes ( Glycera dibranchiata, Diopatra aciculata, Nereis ( Alitta) virens, Arenicola defodiens and Marphysa sanguinea). We estimate that 1600 t of N. virens per annum (worth £52 million) are landed in the UK with approximately 121 000 tonnes of polychaetes collected globally valued at £5.9 billion. Using remote closed circuit television (CCTV) cameras to monitor collectors, activity at local sites is considerable with a mean of 3.14 collectors per tide (day and night) at one site and individuals digging for up to 3 h per tide, although intensity differed seasonally and between sites. Collectors removed on average 1.4 kg of N. virens per person per hour, walking a considerable distance across the intertidal sediment to reach areas that were usually already dug. The implications of these human activity and biomass removal levels are explored in the context of fisheries and conservation management. At local, regional and national scales, polychaete bait fisheries are highly valuable, extract significant biomass and have considerable impacts; therefore, they urgently require governance equivalent to other fisheries. [ABSTRACT FROM AUTHOR] more...

For many imperiled fishes in the Laurentian Great Lakes basin, detection protocols and population monitoring programs are lacking. In this study, we used a repeat-sampling approach to compare the effectiveness of two seines (bag and beach) to detect and characterize the abundance of lake-dwelling populations of Eastern Sand Darter (Ammocrypta pellucida); a threatened species in Canada. Compared to the bag seine, the larger beach seine collected a greater number of Eastern Sand Darter and detected the species at more sampling sites. Model-averaged estimates of detection probability were also greater for the beach seine (p= 0.72) than bag seine (p= 0.48). A decline in catch over repeated seine hauls occurred at less than a third of the sample units. Mean capture probabilities were 0.41 in units sampled by beach seine, and 0.37 in units sampled by bag seine, when depletion occurred. Sizes of Eastern Sand Darter collected by each seine were significantly different, with fewer small (<40 mm total length) individuals found in bag seine hauls. Power analyses indicate that data collected with either seine are expected to detect changes in local distribution of 50% or greater. Power to detect future changes in Eastern Sand Darter abundance of 50% or greater is predicted to be higher for the beach seine, and to increase with the number of seine hauls at a site. Catch differences between seines are interpreted to reflect the greater area sampled by the larger beach seine. [ABSTRACT FROM AUTHOR] more...

Information and understanding of fishing activities at sea are fundamental components of marine knowledge and maritime situational awareness. Such information is important to fisheries science, public authorities and policy-makers. In this paper we introduce a first map at European scale of EU fishing activities extracted using Automatic Identification System ship tracking data. The resulting map is a density of points that identify fishing activities. A measure of the reliability of such information is also presented as a map of coverage reception capabilities. [ABSTRACT FROM AUTHOR] more...

The harlequin fish (Othos dentex) is the largest serranid found in the temperate waters of southern Australia. Acoustic telemetry was used to continuously track the movements and activity patterns of 10 harlequin fish (330-620 mm total length; 0.5-3 kg weight) for a 16-month period at a coastal reef site. Data showed that the harlequin fish is a site-attached, diurnal predator, with a relatively small home range in comparison with other temperate reef fishes from Australia and New Zealand. These characteristics indicate that the harlequin fish is susceptible to localised depletions from fishing, but that it can be protected within no-take marine protected areas and can be detected with appropriate daytime monitoring techniques. Individuals also displayed discrete depth preferences on the reef slope, evidence of a nocturnal home base, and homing ability following disturbance from an extreme storm event. [ABSTRACT FROM AUTHOR] more...

Integral projection models ( IPMs) have a number of advantages over matrix-model approaches for analyzing size-structured population dynamics, because the latter require parameter estimates for each age or stage transition. However, IPMs still require appropriate data. Typically they are parameterized using individual-scale relationships between body size and demographic rates, but these are not always available. We present an alternative approach for estimating demographic parameters from time series of size-structured survey data using a Bayesian state-space IPM ( SSIPM). By fitting an IPM in a state-space framework, we estimate unknown parameters and explicitly account for process and measurement error in a dataset to estimate the underlying process model dynamics. We tested our method by fitting SSIPMs to simulated data; the model fit the simulated size distributions well and estimated unknown demographic parameters accurately. We then illustrated our method using nine years of annual surveys of the density and size distribution of two fish species (blue rockfish, Sebastes mystinus, and gopher rockfish, S. carnatus) at seven kelp forest sites in California. The SSIPM produced reasonable fits to the data, and estimated fishing rates for both species that were higher than our Bayesian prior estimates based on coast-wide stock assessment estimates of harvest. That improvement reinforces the value of being able to estimate demographic parameters from local-scale monitoring data. We highlight a number of key decision points in SSIPM development (e.g., open vs. closed demography, number of particles in the state-space filter) so that users can apply the method to their own datasets. [ABSTRACT FROM AUTHOR] more...

Detailed re-examination of the datasets that were used for a meta-analysis of fishway attraction and passage revealed a number of errors that we addressed and corrected. We subsequently re-analysed the revised dataset, and results showed no significant changes in the primary conclusions of the original study; for most species, effective performance cannot be assured for any fishway type. [ABSTRACT FROM AUTHOR] more...

We compare the results of different monitoring programs regarding spatial and temporal trends of priority hazardous substances of the European Water Framework Directive (WFD). Fish monitoring data for hexachlorobenzene (HCB), mercury (Hg), and perfluorooctane sulfonic acid (PFOS) sampled in German freshwaters between the mid-1990s and 2014 were evaluated according to the recommendations of the 2014 adopted WFD guidance document on biota monitoring, i.e., normalization to 5 % lipid content (HCB) or 26 % dry mass (Hg, PFOS) and adjustment to trophic level (TL) 4. Data of the German Environmental Specimen Bank (ESB) (annual pooled samples of bream) were compared to monitoring data of the German federal states (FS), which refer to individual fish of different species. Significant decreasing trends ( p < 0.01) were detected for Hg in bream ( Abramis brama) sampled by both, the ESB and the FS between 1993 and 2013 but not for FS samples comprising different fish species. Data for HCB and PFOS were more heterogeneous due to a smaller database and gave no consistent results. Obviously, normalization could not compensate differences in sampling strategies. The results suggest that the data treatment procedure proposed in the guidance document has shortcomings and emphasize the importance of highly standardized sampling programs in trend monitoring or whenever results between sites have to be compared. [ABSTRACT FROM AUTHOR] more...

Background: Recreational scuba diving is a popular activity of the coral reef tourism industry. In practice, local diving centers recommend interesting sites to help visiting divers make their plans. Fish are among the major attractions, but they need to be listed with care because the temporal occurrence of a fish species is difficult to predict. To address this issue, we propose methods to categorize each fish species based on its long-term occurrence and likelihood of being seen. Methods: We assume that there are K categories of occurrence of a fish assemblage and propose two methods [an arithmetic-mean method (AM) and a geometric-mean method (GM)] to define the range of species in each category. Results: Experiments based on long term datasets collected at three underwater stations (each having 51-53 surveys and totals of 262-284 fish species) on coral reefs in southern Taiwan showed that when K = 4 (rare, occasional, frequent and common categories), 11-14 species were concurrently assigned to the common category by AM for data sets based on surveys 10, 15, 20, 25, 30, 35, 40, 45, or 51-53 in contrast to the 18-26 species assigned as common by GM. If a similarity index of 0.7 (compared to the total pool of fish species) was the minimum threshold for diver satisfaction, then 20-25 surveys provide sufficient data for listing the common species at a given dive spot. Conclusions: Common fish species, are the most temporally stable, and thus are more appropriate for attracting divers. These can be effectively differentiated by either AM or GM with at least 25 surveys. We suggest regular updating of each fish's category through periodic surveys to assure the accuracy of information at a particular dive spot. [ABSTRACT FROM AUTHOR] more...

In partial protection management areas such as Recreational Fishing Havens ( RFHs) where commercial fishing is prohibited there are fewer sampling methods available for quantifying the relative abundance of species. Consequently, a framework is needed in such areas to decide whether sampling should be based on: (1) fishery-independent techniques; (2) fishery-dependent methods that rely on recreational fishery harvests; or (3) a combination of the two. This study compared fishery-independent data derived from baited remote underwater video stations ( BRUVS) and independent fishing surveys ( IFS) with fishery-dependent data based on recreational angler surveys ( AS) to identify the fish species that were best enumerated by each method in two Australian RFHs. Each method captured/detected disparate species and each consistently showed correlations with the relative abundance of particular suites of species. The species that were correlated with and best enumerated by BRUVS were Microcanthus strigatus (Cuvier) and Pelates sexlineatus (Qouy & Gaimard); those correlated with IFS were Gerres subfasciatus Cuvier, Girella tricuspidata (Qouy & Gaimard), Mugil cephalus L. and Pomatomus saltatrix (L.); and those correlated with AS were Platycephalus fuscus Cuvier and Acanthopagrus australis (Owen). By identifying the species that were best quantified by each method, this study facilitates accurate monitoring of key species within RFHs. [ABSTRACT FROM AUTHOR] more...

Effective decision making to protect coastally associated dolphins relies on monitoring the presence of animals in areas that are critical to their survival. Hawaiian spinner dolphins forage at night and rest during the day in shallow bays. Due to their predictable presence, they are targeted by dolphintourism. In this study, comparisons of presence were made between passive acoustic monitoring (PAM) and vessel-based visual surveys in Hawaiian spinner dolphin resting bays. DSG-Ocean passive acoustic recording devices were deployed in four bays along the Kona Coast of Hawai'i Island between January 8, 2011 and August 30, 2012. The devices sampled at 80 kHz, making 30-s recordings every four minutes. Overall, dolphins were acoustically detected on 37.1% to 89.6% of recording days depending on the bay. Vessel-based visual surveys overlapped with the PAM surveys on 202 days across the four bays. No significant differences were found between visual and acoustic detections suggesting acoustic surveys can be used as a proxy for visual surveys. Given the need to monitor dolphin presence across sites, PAM is the most suitable and efficient tool for monitoring long-term presence/absence. Concomitant photo-identification surveys are necessary to address changes in abundance over time. [ABSTRACT FROM AUTHOR] more...

Many marine fishes mate in massive and spectacular gatherings at predictable times and places. These spawning aggregations are often attractive targets of fisheries. Many commercially important fish species exhibit aggregation spawning, and many have undergone serious declines from overfishing. It is timely to explore whether the exploitation of spawning aggregations makes species particularly susceptible to overfishing; if so, why and how we can better manage these species. I present evidence that aggregate fish spawners are especially vulnerable because of both increased catchability (lethal effects) and biological factors (nonlethal effects). For these species to continue contributing to food security and livelihoods while retaining their ecosystem function, a truly precautionary approach is essential to reduce the risk of declines, particularly in the case of small-scale commercial fisheries of low-productivity species and where management and monitoring are lacking. There is a pressing need to mainstream spawning aggregations into marine resource management. [ABSTRACT FROM AUTHOR] more...

Endosulfan has been listed as a persistent organic pollutant, and is frequently found in agricultural environments during monitoring processes owing to its heavy use and persistent characteristics. This study was conducted to understand the effects of endosulfan on the development of zebrafish (Danio rerio) embryos by exposing them to a specific range of endosulfan concentrations. Exposing zebrafish embryos to endosulfan for 96 h yielded no acute toxicity until the concentration reached 1500 µg L-1, whereas malformed zebrafish larvae developed severely curved spines and shortened tails. About 50% of zebrafish larvae were malformed when exposed to 600 µg L-1 of endosulfan. Comparative gene expression using realtime quantitative polymerase chain reaction was assessed using endosulfan-exposed zebrafish embryos. CYP1A and CYP3A were significantly enhanced in response to endosulfan treatment. Two genes, acacb and fasn, encoding acetyl-CoA carboxylase b and fatty acid synthase proteins, respectively, were also up-regulated after treating zebrafish embryos with endosulfan. These genes are also involved in fatty acid biosynthesis. The genes encoding vitellogenin and Hsp70 increased in a concentration-dependent manner in embryos. Finally, biochemical studies showed that acetylcholinesterase activity was reduced, whereas glutathione S-transferase and carboxylesterase activities were enhanced in zebrafish embryos after endosulfan treatment. These biochemical and molecular biological differences might be used for tools to determine contamination of endosulfan in the aquatic environment. [ABSTRACT FROM AUTHOR] more...

Natural biotoxins (phycotoxins) are planktonic algae products which they produce to defence against predators. Bivalve shellfish can acummulate large quantities of biotoxins by water filtration. In humans these toxins can cause six syndromes: ASP, AZP, DSP, NSP, PSP and VSP. Detection of biotoxins is carried on HPLC (High- Performance Liquid Chromatography) with different detectors. In the coastal waters of Montenegro biotoxins monitoring started in 2014, but IMB working team performs regular monthly monitoring of toxic and potentially toxic algae species for years. In neighboring countries, primary Croatia, permanent marine biotoxins monitoring is performed per years as well as toxic algae species. [ABSTRACT FROM AUTHOR] more...

The article discusses multiuse trails have been a prominent feature of park lands for many years. Now, multiuse rain gardens may become a prominent feature of many parks. Rain gardens have traditionally been used for catchment, retention, and filtration of impervious surface storm water runoff. County park districts and other agencies across Ohio (and elsewhere) are being pushed more and more toward finding inexpensive creative multi-solutions to issues as a result of limited budgets. more...

Quantifying and classifying ichthyoplankton is one of the most effective ways of monitoring the recruitment process in fishes. However, correctly identifying the fish based on morphological characters is extremely difficult, especially in the early stages of development. We examined ichthyoplankton from tributaries and reservoirs along the middle stretch of the Paranapanema River, one of the areas most impacted by hydroelectric projects in the Neotropics. Matching DNA sequences of the COI gene (628-648 bp) allowed us to identify 99.25% of 536 samples of eggs (293) and larvae (243) subjected to BOLD- IDS similarity analysis with a species-level threshold of 1.3%. The results revealed 37 species in 27 genera, 15 families and four orders, some 23.8% of documented fish species in the Paranapanema River. Molecular identification meant that we could include data from egg samples that accounted for about 30% of the species richness observed. The results in this study confirm the efficacy of DNA barcoding in identifying Neotropical ichthyoplankton and show how the data produced provide valuable information for preparing plans for conserving and managing inland waters. [ABSTRACT FROM AUTHOR] more...

To fulfil the temperature requirements of the cold chain, the fresh fish are usually packed, stored and transported to fish markets with ice in open styrofoam boxes. Some companies offer a more flexible service and they deliver the fish directly to private consumers. In these cases the fish are packed with artificial ice – hydrated and frozen gel pads in specially designed completely closed styrofoam boxes. This study presents the results of the comparison of seven packing methods with the aim to potentially improve them. The temperature outside and inside of the closed box and temperatures in the abdominal cavity of gutted sea bass ( Dicentrarchus labrax ) were measured during the logistics process using Radio Frequency Identification (RFID) technology. The aim of the presented study is to define the optimal cooling materials and methods for different handling options. As an important result, a new efficient, time and energy saving method of packing the fish with the combination of dry non-hydrated gel pads and wet ice instead of the use of frozen gel pads alone is proposed. This method ensures recommended storage temperatures between 0 °C and 4 °C and stable conditions inside the box at room temperatures (or higher) for a longer period of time under the same time-ambient conditions after delivery to the consumer. Furthermore it was established that the part of the ice that melted inside the box, due to higher ambient temperatures, was absorbed by the dry gel pad and only a small quantity of water remained on the bottom of the box. [ABSTRACT FROM AUTHOR] more...

Monitoring is essential for effective conservation and management but the ability of monitoring to deliver accurate and precise measures of changes in abundance is often not evaluated, particularly in marine studies. Here we use long-term datasets from three New Zealand marine reserves to evaluate the capacity of underwater visual census monitoring to quantify trends in abundance for four reef-fish species. Simulations parameterized by the observed data were used to evaluate multiple monitoring configurations based on statistical power and trend-estimate precision and accuracy. These results were then used to identify optimal monitoring designs that maximized power, precision or accuracy within budgetary constraints. Power and trend-estimate accuracy and precision were highest for abundant species and lowest for species exhibiting low and/or highly variable abundances. For the least abundant species, trend estimates were less accurate and precise for negative compared to positive trends, highlighting a reduced ability to identify ongoing declines in depleted populations. Optimal monitoring configurations varied amongst species, locations and whether assessments were based on power, precision or accuracy. In general, higher within-site replication was required for the least abundant species, whereas greater site replication was required for more spatially heterogeneous species/locations. In addition, we found that for some species the optimal monitoring approach changes through time, highlighting the need for an adaptive approach to monitoring. Finally, we recommend that future monitoring evaluations focus on assessing precision and accuracy, rather than power, as this places greater emphasis on the assessment of biological rather than statistical significance. [ABSTRACT FROM AUTHOR] more...

Surveys based on nonrandom site selection, or convenience samples, are often a necessary part of large-scale monitoring programs to help minimize costs. The reliability of convenience samples to inform managers about distributions or population status of imperiled species is questionable, however, because the samples may not be representative of the whole population. We compared fish community data from 20 nonrandom, long-term monitoring sites for Rio Grande Silvery MinnowHybognathus amaruswith those from 20 randomly chosen samples collected during two surveys (one in summer, one in autumn) in the Rio Grande, New Mexico. We compared the species richness, community composition, and the catch per unit effort (CPUE). Fish species compositions, which were similar between both sets of summer and autumn surveys, were nearly identical in the autumn surveys. Similarly, we found consistent Rio Grande Silvery Minnow CPUE between surveys; summer random surveys estimated 0.32 fish/100 m2sampled, whereas summer nonrandom surveys estimated 0.37 fish/100 m2sampled. In autumn, both surveys showed a marked decline in Rio Grande Silvery Minnow; random surveys found 0.08 fish/100 m2sampled (95% confidence interval 0.04–0.18), whereas the nonrandom surveys failed to collect any Rio Grande Silvery Minnow. Both surveys showed a reduction in species richness between summer and autumn with a corresponding increase in dominance by Red ShinerCyprinella lutrensisand a decline in Rio Grande Silvery Minnow. We failed to find any meaningful differences in either fish community or Rio Grande Silvery Minnow CPUE between random and nonrandom sites, suggesting that the long-term, nonrandom locations currently used to monitor the Rio Grande Silvery Minnow population are representative of the middle Rio Grande. We believe our results are applicable to many monitoring programs in systems with a homogeneous distribution of mesohabitats; nonetheless, we recommend that managers assess potential bias in monitoring programs based on convenience samples. [ABSTRACT FROM PUBLISHER] more...

To determine the total number of Green SturgeonAcipenser medirostrispresent in the Rogue River, Oregon, we compared plot sampling using a dual-frequency identification sonar (DIDSON), a density-based estimation technique combining the number of individuals detected and the area sampled, to a concurrent mark–recapture estimate. Using the DIDSON-based method, we estimated the total abundance of Green Sturgeon to be 223 (95% confidence interval = 180–266). The mark–recapture method resulted in an estimate of 236 individuals (150–424). The noninvasive DIDSON transect estimates resulted in tighter confidence intervals and required fewer technician hours to collect the data than did the mark–recapture method (37 h versus 232 h, respectively). Precise estimates of the abundance and distribution of Green Sturgeon are important components to species recovery and management. Thus, this new technique has the potential to greatly improve population monitoring and is an excellent tool to identify occupied habitats. Received June 9, 2014; accepted January 28, 2015 [ABSTRACT FROM PUBLISHER] more...

We evaluated the efficacy of portable PIT detectors for tracking long-term fish movement in an open stream environment. In June and October of 2012, we PIT-tagged a total of 190 Colorado River Cutthroat TroutOncorhynchus clarkii pleuriticus(CRCT) in a 1.7-km segment of a small, montane stream. In the summers of 2012–2013 (15 total occasions), we relocated PIT-tagged trout using portable PIT detectors. The maximum detection distance of 23-mm PIT tags ranged from 6 to 56 cm and varied with detector, detection plane, and tag orientation. Of the CRCT tagged, 38% were never detected and 43% were detected on two or more occasions. Mean detection efficiencies of PIT-tagged trout were 34% and 45% in 2012 and 2013, respectively, and were generally lower than in evaluations of closed systems and less mobile fishes. We observed a smaller range of CRCT than has been observed by others using radiotelemetry, a difference that could be explained by the spatial and temporal limitations of portable PIT detection we encountered. We conclude that portable PIT detector surveys have value but also drawbacks for tracking the movement of relatively mobile fishes in montane streams. Received September 27, 2014; accepted January 21, 2015 [ABSTRACT FROM PUBLISHER] more...

Determining the value of restocking wild fisheries with hatchery-reared fish requires the ability to identify and quantify the survival of hatchery fish after release. However, to obtain accurate estimates of survival rates, multiple fish identification techniques are often used, making the monitoring of restocking inefficient and costly. Here we test a new immersion marking method to determine its efficiency and cost effectiveness for marking millions of hatchery-reared Atlantic salmon ( Salmo salar). Salmon eggs were marked during the egg swelling stage by immersing eggs in a solution containing seven enriched stable isotopes (134Ba, 135Ba, 136Ba, 137Ba, 86Sr, 87Sr, and 26Mg) for 2 h immediately after fertilisation. One hundred percent successful marks were detected in the otoliths of resulting larvae at a concentration of 1000 μg·L−1 for 136Ba and 100 μg·L−1 for 135Ba and 137Ba, with no detrimental effects on survival or health of egg and yolk sac larvae. We estimate that seven unique mark combinations can be made at a cost of $0.0001 to $0.0017 (US) per egg and conclude that marking via egg immersion is suitable for low cost, accurate marking of hatchery-reared salmonids destined for restocking purposes. [ABSTRACT FROM AUTHOR] more...

Intrinsic rebound potential, the demographic measure of a fish population's productivity that sustains a given mortality, relates to a species' resiliency and can be useful for understanding and evaluating the status of exploited populations, especially those poorly monitored and of low productivity, like many shark populations. The rebound potential is derived from the Euler-Lotka equation and, with the dynamics kept simple, is easily calculated for a given total mortality, needing only a species' age at maturity and its natural mortality ( M). Its value can be quickly read from an isopleth diagram, whose contour pattern shows the interdependence of these two key parameters among different life histories. How the rebound potentials change as a function of age at maturity and the full range of possible M values also shows a way to estimate a species' natural mortality bounds. Importance of the age at maturity parameter is stressed. [ABSTRACT FROM AUTHOR] more...