Geology topics

Jon J. Amberg

Publications and source records attributed to Jon J. Amberg.

16 recordsLinked to original sources

USGS2017

Comparison of American Fisheries Society (AFS) standard fish sampling techniques and environmental DNA for characterizing fish communities in a large reservoir

Recently, methods involving examination of environmental DNA (eDNA) have shown promise for characterizing fish species presence and distribution in waterbodies. We evaluated the use of eDNA for standard fish monitoring surveys in a large reservoir. Specifically, we compared the presence, relative abundance, biomass, and relative percent composition of Largemouth Bass Micropterus salmoides and Gizzard Shad Dorosoma cepedianum measured through eDNA methods and established American Fisheries Society standard sampling methods for Theodore Roosevelt Lake, Arizona. Catches at electrofishing and gillnetting sites were compared with eDNA water samples at sites, within spatial strata, and over the entire reservoir. Gizzard Shad were detected at a higher percentage of sites with eDNA methods than with boat electrofishing in both spring and fall. In contrast, spring and fall gillnetting detected Gizzard Shad at more sites than eDNA. Boat electrofishing and gillnetting detected Largemouth Bass at more sites than eDNA; the exception was fall gillnetting, for which the number of sites of Largemouth Bass detection was equal to that for eDNA. We observed no relationship between relative abundance and biomass of Largemouth Bass and Gizzard Shad measured by established methods and eDNA copies at individual sites or lake sections. Reservoirwide catch composition for Largemouth Bass and Gizzard Shad (numbers and total weight [g] of fish) as determined through a combination of gear types (boat electrofishing plus gillnetting) was similar to the proportion of total eDNA copies from each species in spring and fall field sampling. However, no similarity existed between proportions of fish caught via spring and fall boat electrofishing and the proportion of total eDNA copies from each species. Our study suggests that eDNA field sampling protocols, filtration, DNA extraction, primer design, and DNA sequencing methods need further refinement and testing before incorporation into standard fish sampling surveys.

Arizona↗

USGS2017

Comparing efficiency of American Fisheries Society standard snorkeling techniques to environmental DNA sampling techniques

Analysis of environmental DNA (eDNA) is an emerging technique used to detect aquatic species through water sampling and the extraction of biological material for amplification. Our study compared the efficacy of eDNA methodology to American Fisheries Society (AFS) standard snorkeling surveys with regard to detecting the presence of rare fish species. Knowing which method is more efficient at detecting target species will help managers to determine the best way to sample when both traditional sampling methods and eDNA sampling are available. Our study site included three Navajo Nation streams that contained Navajo Nation Genetic Subunit Bluehead Suckers Catostomus discobolus and Zuni Bluehead Suckers C. discobolus yarrowi . We first divided the entire wetted area of streams into consecutive 100-m reaches and then systematically selected 10 reaches/stream for snorkel and eDNA surveys. Surface water samples were taken in 10-m sections within each 100-m reach, while fish presence was noted via snorkeling in each 10-m section. Quantitative PCR was run on each individual water sample in quadruplicate to test for the presence or absence of the target species. With eDNA sampling techniques, we were able to positively detect both species in two out of the three streams. Snorkeling resulted in positive detection of both species in all three streams. In streams where the target species were detected with eDNA sampling, snorkeling detected fish at 11–29 sites/stream, whereas eDNA detected fish at 3–12 sites/stream. Our results suggest that AFS standard snorkeling is more effective than eDNA for detecting target fish species. To improve our eDNA procedures, the amount of water collected and tested should be increased. Additionally, filtering water on-site may improve eDNA techniques for detecting fish. Future research should focus on standardization of eDNA sampling to provide a widely operational sampling tool.

Arizona, New Mexico↗

USGS2017

Using silver and bighead carp cell lines for the identification of a unique metabolite fingerprint from thiram-specific chemical exposure

Conservation biology often requires the control of invasive species. One method is the development and use of biocides. Identifying new chemicals as part of the biocide registration approval process can require screening millions of compounds. Traditionally, screening new chemicals has been done in vivo using test organisms. Using in vitro (e.g., cell lines) and in silico (e.g., computer models) methods decrease test organism requirements and increase screening speed and efficiency. These methods, however, would be greatly improved by better understanding how individual fish species metabolize selected compounds. We combined cell assays and metabolomics to create a powerful tool to facilitate the identification of new control chemicals. Specifically, we exposed cell lines established from bighead carp and silver carp larvae to thiram (7 concentrations) then completed metabolite profiling to assess the dose-response of the bighead carp and silver carp metabolome to thiram. Forty one of the 700 metabolomic markers identified in bighead carp exhibited a dose-response to thiram exposure compared to silver carp in which 205 of 1590 metabolomic markers exhibited a dose-response. Additionally, we identified 11 statistically significant metabolomic markers based upon volcano plot analysis common between both species. This smaller subset of metabolites formed a thiram-specific metabolomic fingerprint which allowed for the creation of a toxicant specific, rather than a species-specific, metabolomic fingerprint. Metabolomic fingerprints may be used in biocide development and improve our understanding of ecologically significant events, such as mass fish kills.

Chemosphere↗

USGS2017

Acoustic deterrence of bighead carp ( Hypophthalmichthys nobilis ) to a broadband sound stimulus

Recent studies have shown the potential of acoustic deterrents against invasive silver carp ( Hypophthalmichthys molitrix ). This study examined the phonotaxic response of the bighead carp ( H. nobilis ) to pure tones (500–2000 Hz) and playbacks of broadband sound from an underwater recording of a 100 hp outboard motor (0.06–10 kHz) in an outdoor concrete pond (10 × 5 × 1.2 m) at the U.S. Geological Survey Upper Midwest Environmental Science Center in La Crosse, WI. The number of consecutive times the fish reacted to sound from alternating locations at each end of the pond was assessed. Bighead carp were relatively indifferent to the pure tones with median consecutive responses ranging from 0 to 2 reactions away from the sound source. However, fish consistently exhibited significantly (P < 0.001) greater negative phonotaxis to the broadband sound (outboard motor recording) with an overall median response of 20 consecutive reactions during the 10 min trials. In over 50% of broadband sound tests, carp were still reacting to the stimulus at the end of the trial, implying that fish were not habituating to the sound. This study suggests that broadband sound may be an effective deterrent to bighead carp and provides a basis for conducting studies with wild fish.

Journal of Great Lakes Research↗

USGS2015

Preliminary characterization of digestive enzymes in freshwater mussels

Resource managers lack an effective chemical tool to control the invasive zebra mussel Dreissena polymorpha . Zebra mussels clog water intakes for hydroelectric companies, harm unionid mussel species, and are believed to be a reservoir of avian botulism. Little is known about the digestive physiology of zebra mussels and unionid mussels. The enzymatic profile of the digestive glands of zebra mussels and native threeridge ( Amblema plicata ) and plain pocketbook mussels ( Lampsilis cardium ) are characterized using a commercial enzyme kit, api ZYM, and validated the kit with reagent-grade enzymes. A linear correlation was shown for only one of nineteen enzymes, tested between the api ZYM kit and a specific enzyme kit. Thus, the api ZYM kit should only be used to make general comparisons of enzyme presence and to observe trends in enzyme activities. Enzymatic trends were seen in the unionid mussel species, but not in zebra mussels sampled 32 days apart from the same location. Enzymatic classes, based on substrate, showed different trends, with proteolytic and phospholytic enzymes having the most change in relative enzyme activity.

Journal of Shellfish Research↗

USGS2015

Validation of eDNA markers for New Zealand mudsnail surveillance and initial eDNA monitoring at Mississippi River Basin sites

The performance of newly developed New Zealand mudsnail ( Potamopyrgus antipodarum ; NZMS) genetic markers for environmental (eDNA) analysis of water were compared across two laboratories. The genetic markers were tested in four quantitative polymerase chain reaction assays targeting two regions of the NZMS mitochondrial genome, specifically the cytochrome c oxidase subunit 1 (coi) and cytochrome b (cytb) genes. In a blind study, analysts tested each sample eight times with each assay. There were 10 expected-negative samples from the Black River in La Crosse, Wisconsin, 10 expected-positive samples from the Black Earth Creek in Black Earth, Wisconsin, and 10 known-positive samples from the Black River spiked with NZMS DNA. Previously extracted samples, kept at the Upper Midwest Environmental Sciences Center, were pooled by sample location and then equal quantities were distributed between the Upper Midwest Environmental Sciences Center and the Molecular Conservation Genetics Laboratory at the University of Wisconsin-Stevens Point for analysis. The assays tested were (1) the assay targeting cytb with a minor groove binder probe described by Goldberg and others (2013), (2) the cytb assay with a modified double-quenched probe, (3) an assay targeting coi with a double-quenched probe, and (4) a duplex reaction combining the modified cytb assay and the coi assay. Samples were considered positive for the presence of NZMS DNA when quantitative polymerase chain reaction amplification and probe signal was higher than the normalized threshold value above baseline fluorescence. For the duplex assay, samples were considered positive only when both probe signals were higher than the normalized threshold value above baseline fluorescence. Positive results were then confirmed by sequencing the products. All four assays detected the DNA of NZMS in all expected-positive and known-positive samples in both labs. The modified cytb assay, the coi assay, and the duplex assay all failed to detect the DNA of NZMS in all expected-negative samples in both labs. The cytb assay, as described by Goldberg and others (2013), failed to detect the DNA of NZMS in all expected-negative samples for the Molecular Conservation Genetics Laboratory, but some reactions resulted in positive detection in late cycles for 9 of the 10 expected-negative samples at the Upper Midwest Environmental Sciences Center. Amplicons for expected-negative samples with positive reactions were sent for sequencing, and none were confirmed as NZMS. Six amplicons failed to give readable sequences, and three gave sequences without similarity to any known sequence in GenBank. Amplicons from each assay for one representative positive sample were sequenced and identified as NZMS with greater than 99 percent identity. The duplex assay was chosen as the most efficient assay and was used at the Upper Midwest Environmental Sciences Center to analyze triplicate samples from 29 streams in Wisconsin, 8 streams in Illinois, and 8 streams in Iowa. In order to verify results, additional triplicate samples were collected from two of the streams in Iowa and two of the streams in Wisconsin for analysis at the Molecular Conservation Genetics Laboratory. All samples at all sites were negative for NZMS DNA.

Illinois, Iowa, Wisconsin↗

USGS2015

Environmental DNA calibration study interim technical review report December 2014

The Environmental DNA Calibration Study (ECALS) is a multi-year study to improve the understanding and interpretation of the detection of Asian carp DNA in environmental samples (eDNA) used in early detection monitoring. eDNA surveillance programs seek to detect the presence of genetic material (DNA in cells sloughed off in slime, feces, urine, etc.) extracted from water samples; the detection of genetic material is linked to the possible presence of Asian carp. The study involves collaboration between the U.S. Army Corps of Engineers, the U.S. Geological Survey, and the U.S. Fish and Wildlife Service. ECALS addresses three major Action Items from the Asian Carp Regional Coordinating Committee (ACRCC) Asian Carp Control Strategy Framework, of which results to date are presented below. Initial ECALS efforts focused on eDNA vectors whereas marker development and calibration experiments received greater attention in 2013.

Report↗

USGS2014

Persistence of DNA in carcasses, slime and avian feces may affect interpretation of environmental DNA data

The prevention of non-indigenous aquatic invasive species spreading into new areas is a goal of many resource managers. New techniques have been developed to survey for species that are difficult to capture with conventional gears that involve the detection of their DNA in water samples (eDNA). This technique is currently used to track the invasion of bigheaded carps (silver carp and bighead carp; Hypophthalmichthys molitrix and H. nobilis ) in the Chicago Area Waterway System and Upper Mississippi River. In both systems DNA has been detected from silver carp without the capture of a live fish, which has led to some uncertainty about the source of the DNA. The potential contribution to eDNA by vectors and fomites has not been explored. Because barges move from areas with a high abundance of bigheaded carps to areas monitored for the potential presence of silver carp, we used juvenile silver carp to simulate the barge transport of dead bigheaded carp carcasses, slime residue, and predator feces to determine the potential of these sources to supply DNA to uninhabited waters where it could be detected and misinterpreted as indicative of the presence of live bigheaded carp. Our results indicate that all three vectors are feasible sources of detectable eDNA for at least one month after their deposition. This suggests that current monitoring programs must consider alternative vectors of DNA in the environment and consider alternative strategies to minimize the detection of DNA not directly released from live bigheaded carps.

PLoS ONE↗

USGS2014

Confocal microscopy as a useful approach to describe gill rakers of Asian species of carp and native filter-feeding fishes of the upper Mississippi River system

To better understand potential diet overlap among exotic Asian species of carp and native species of filter-feeding fishes of the upper Mississippi River system, microscopy was used to document morphological differences in the gill rakers. Analysing samples first with light microscopy and subsequently with confocal microscopy, the three-dimensional structure of gill rakers in Hypophthalmichthys molitrix , Hypophthalmichthys nobilis and Dorosoma cepedianum was more thoroughly described and illustrated than previous work with traditional microscopy techniques. The three-dimensional structure of gill rakers in Ictiobus cyprinellus was described and illustrated for the first time.

Journal of Fish Biology↗

USGS2014

Spatial and temporal variation of the gill rakers of gizzard shad and silver carp in three Midwestern rivers

Improved management of invasive Silver Carp Hypophthalmichthys molitrix in the upper Mississippi River basin may be possible by better understanding the feeding abilities of this population. Food collection for filter-feeding fishes, such as Silver Carp, is influenced by the species-specific structure of their gill rakers. To investigate structural variation in gill rakers of Silver Carp, the morphology of gill rakers was quantified and compared with that of a native filter-feeding fish species which may compete with Silver Carp for food resources, Gizzard Shad Dorosoma cepedianum . Intra- and interspecies variation of gill rakers was examined in both species collected from three locations among four months. Interspecies analysis indicated the size of pores in gill rakers of Silver Carp were much larger than the interraker spacings of Gizzard Shad (95% CI ranged from 80.69 to 185.75 μm versus 16.72 to 47.36 μm, respectively). Intraspecies variation of gill rakers from Silver Carp was related to the overall size of fish and occurred only among sites where dissimilar sizes of fish were collected. This suggested the size of particles filtered by Silver Carp may be dependent upon ontogenic development rather than phenotypic plasticity in response to spatial or temporal factors. Intraspecies variation of gill rakers from Gizzard Shad occurred among site and monthly sampling data; however, variation was only attributable to overall size of fish for monthly sampling data. This suggested ontogeny may influence the filter-feeding ability of this species within a habitat. However, variation noted among sites, which was not attributable to size of fish, may indicate gill rakers are phenotypically plastic among Gizzard Shad populations of various river systems of the upper Mississippi River basin.

Ilinois, Indiana, South Dakota↗

USGS2014

Environmental DNA calibration study. Interim technical review report

Invasive aquatic nuisance species pose a major threat to aquatic ecosystems worldwide. Invasive Asian carps, including bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) have been steadily dispersing upstream through the Mississippi, Illinois, and Des Plaines Rivers since the 1990s. To prevent further movement up the Illinois River into the Chicago Area Waterway System (CAWS, see Figures 1.1.1 to 1.1.3) and possibly Lake Michigan and the Great Lakes ecosystem, an electrical barrier has been operating near Lockport to deter the advance of Asian carp. Although one adult individual has been detected in Lockport pool of the Illinois Waterway, the leading edge of the invasion of bighead and silver carp is considered to be at RM 281.5 in Dresden Island Pool, 15 miles downstream from the barrier and 55 miles from Lake Michigan, and that front has not progressed upstream since 2006. Although spawning activity has been observed in Marseilles pool in 2012, verified capture of eggs and larvae remain downstream in Peoria pool, over 140 miles from Lake Michigan (Figure 1.1.1). Should a sustainable Asian carp population become established in the Great Lakes, native fish populations, as well as many threatened or endangered plant/animal species populations, could be impacted. In response to this threat, the Asian Carp Regional Control Committee (ACRCC) was formed in part to coordinate efforts to understand and organize against the Asian carp threat. The Asian Carp Control Strategy Framework (2012a) outlined major tasks to be completed for a better understanding of factors related to the advance of Asian carp populations towards the Great Lakes. In addition, the ACRCC formed the Monitoring and Rapid Response Workgroup to address Asian carp monitoring and removal (ACRCC 2012b).

Midwest waterways↗

USGS2013

Fish gut microbiota analysis differentiates physiology and behavior of invasive Asian carp and indigenous American fish

Gut microbiota of invasive Asian silver carp (SVCP) and indigenous planktivorous gizzard shad (GZSD) in Mississippi river basin were compared using 16S rRNA gene pyrosequencing. Analysis of more than 440 000 quality-filtered sequences obtained from the foregut and hindgut of GZSD and SVCP revealed high microbial diversity in these samples. GZSD hindgut (GZSD_H) samples (n=23) with >7000 operational taxonomy units (OTUs) exhibited the highest alpha-diversity indices followed by SVCP foregut (n=15), GZSD foregut (n=9) and SVCP hindgut (SVCP_H) (n=24). UniFrac distance-based non-metric multidimensional scaling (NMDS) analysis showed that the microbiota of GZSD_H and SVCP_H were clearly separated into two clusters: samples in the GZSD cluster were observed to vary by sampling location and samples in the SVCP cluster by sampling date. NMDS further revealed distinct microbial community between foregut to hindgut for individual GZSD and SVCP. Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes were detected as the predominant phyla regardless of fish or gut type. The high abundance of Cyanobacteria observed was possibly supported by their role as the fish’s major food source. Furthermore, unique and shared OTUs and OTUs in each gut type were identified, three OTUs from the order Bacteroidales, the genus Bacillariophyta and the genus Clostridium were found significantly more abundant in GZSD_H (14.9–22.8%) than in SVCP_H (0.13–4.1%) samples. These differences were presumably caused by the differences in the type of food sources including bacteria ingested, the gut morphology and digestion, and the physiological behavior between GZSD and SVCP.

International Society for Microbial Ecology↗

USGS2013

Phenotypic plasticity in the spawning traits of bigheaded carp (Hypophthalmichthys spp.) in novel ecosystems

1. Bigheaded carp, including both silver (Hypophthalmichthys molitrix) and bighead (H. nobilis) carp, are successful invasive fishes that threaten global freshwater biodiversity. High phenotypic plasticity probably contributes to their success in novel ecosystems, although evidence of plasticity in several spawning traits has hitherto been largely anecdotal or speculative. 2. We collected drifting eggs from a Midwestern U.S.A. river from June to September 2011 and from April to June 2012 to investigate the spawning traits of bigheaded carp in novel ecosystems. 3. Unlike reports from the native range, the presence of drifting bigheaded carp eggs was not related to changes in hydrological regime or mean daily water temperature. Bigheaded carp also exhibited protracted spawning, since we found drifting eggs throughout the summer and as late as 1 September 2011. Finally, we detected bigheaded carp eggs in a river reach where the channel is c. 30 m wide with a catchment area of 4579 km 2 , the smallest stream in which spawning has yet been documented. 4. Taken with previous observations of spawning traits that depart from those observed within the native ranges of both bighead and silver carp, our findings provide direct evidence that bigheaded carp exhibit plastic spawning traits in novel ecosystems that may facilitate invasion and establishment in a wider range of river conditions than previously envisaged.

Freshwater Biology↗

USGS2013

Detection of environmental DNA of bigheaded carps in samples collected from selected locations in the St. Croix River and in the Mississippi River

The use of molecular methods, such as the detection of environmental deoxyribonucleic acid (eDNA), have become an increasingly popular tool in surveillance programs that monitor for the presence of invasive species in aquatic systems. One early application of these methods in aquatic systems was surveillance for DNA of Asian carps (specifically bighead carp Hypophthalmichthys nobilis and silver carp H. molitrix) in water samples taken from the Chicago Area Waterway System. The ability to identify DNA of a species in an environmental sample presents a potentially powerful tool because these sensitive analyses can presumably detect the presence of DNA in water even when the species is not abundant or are difficult to catch or monitor with traditional gear. Prior to research presented in this report, an initial eDNA surveillance effort was completed in selected locations in the Upper Mississippi and St. Croix Rivers in 2011 after the capture of a bighead carp in the St. Croix River near Prescott, WI. Data presented in this report were developed to duplicate the 2011 monitoring results from the Upper Mississippi and St. Croix Rivers and to provide critical insight into the technique to inform future work in these locations. We specifically sought to understand the potential confounding effects of other pathways of eDNA movement (e.g., fish-eating birds, watercraft) on the variation in background DNA by collecting water samples from (1) sites within the St. Croix River and the upper Mississippi River where the DNA of silver carp was previously detected, (2) sites considered to be free of Asian carp, and (3) a site known to have a large population of Asian carp. We also sought to establish a baseline Asian carp eDNA signature to which future eDNA sampling efforts could be compared. All samples taken as part of this effort were processed using conventional polymerase chain reaction (PCR) according to procedures outlined in the U.S. Army Corps of Engineers Quality Assurance Project Plan with minor deviations designed to enhance the rigor of our data. Presence of DNA in PCR-positive samples was confirmed by Sanger sequencing (forward and reverse) and sequences were considered positive only if sequences (forward and reverse) of ≥150 base pairs had a match of ≥95% to those of published sequences for bighead carp or silver carp. The DNA of bighead carp and silver carp was not detected in environmental samples collected above and below St. Croix Falls Dam on the St. Croix River, above and below the Coon Rapids Dam and below Lock and Dam 1 on the Upper Mississippi River, and from two negative control lakes, Square Lake and Lake Riley. The DNA of silver carp was detected in environmental samples collected below Lock and Dam 19 at Keokuk, Iowa, a reach of the river with high silver carp abundance. The portion (68%) of environmental samples taken below Lock and Dam 19 that were determined to contain the DNA of silver carp was similar to that reported in the scientific literature for other abundant species. The DNA of bighead carp, however, was not detected in environmental samples collected below Lock and Dam 19, a reach of the river known to have bighead carp. Previous reported detections of the DNA of silver carp in samples collected in 2011 were not replicated in this study. Additional analyses are planned for the DNA extracted from the samples collected in 2012. Those analyses may provide additional information regarding the lack of amplification of bighead carp DNA and the lengths of the sequences of silver carp DNA present in samples taken below Lock and Dam 19. These additional analyses may help inform the use of eDNA monitoring in large, complex systems like the Mississippi River.

Minnesota, Wisconsin↗

USGS2012

Molecular responses differ between sensitive silver carp and tolerant bighead carp and bigmouth buffalo exposed to rotenone

Some species of fish are more tolerant of rotenone, a commonly used non-specific piscicide, than others. This species-specific tolerance to rotenone has been thought to be associated with the uptake and the efficiency at which the chemical is detoxified. However, rotenone stimulates oxidative stress and superoxides, which are also toxic. Understanding the modes in which fish physiologically respond to rotenone is important in developing improved protocols for its application in controlling aquatic nuisance species. Using a molecular approach, we investigated the physiological and molecular mechanisms of rotenone resistance. Species-specific responses were observed when rotenone-sensitive silver, Hypophthalmichthys molitrix, and both rotenone-resistant bighead carp, Hypophthalmichthys nobilis, and bigmouth buffalo, Ictiobus cyprinellus, were exposed to rotenone. Rotenone levels in plasma were highest 90 min after exposure in both silver carp and bigmouth buffalo, but bigmouth buffalo tolerated over twice the burden (ng mL -1 g -1 ) than silver carp. Expression of genes related with detoxification ( cyp1a and gst ) increased in silver carp, but either decreased or remained the same in bighead carp. Genes linked with oxidative stress in the cytosol ( gpx , cat and sod1 ) and hsp70 increased only in silver carp after a 6-h exposure. Expression of genes associated with oxidative stress in the mitochondria ( sod2 and ucp2 ) differed between silver carp and bighead carp. Expression of sod2 changed minimally in bighead carp, but expression of ucp2 linearly increased to nearly 85-fold of the level prior to exposure. Expression of sod2 and ucp2 did not change until 6 h in silver carp. Use of sod1 and sod2 to combat oxidative stress results in hydrogen peroxide production, while use of ucp2 produces nitric oxide, a chemical known to inhibit apoptosis. We conclude that the mechanism at which a fish handles oxidative stress plays an important role in the tolerance to rotenone.

Fish Physiology and Biochemistry↗

USGS2012

Assessing consumption of bioactive micro-particles by filter-feeding Asian carp

Silver carp Hypophthalmichthys molitrix (SVC) and bighead carp H. nobilis (BHC) have impacted waters in the US since their escape. Current chemical controls for aquatic nuisance species are non-selective. Development of a bioactive micro-particle that exploits filter-feeding habits of SVC or BHC could result in a new control tool. It is not fully understood if SVC or BHC will consume bioactive micro-particles. Two discrete trials were performed to: 1) evaluate if SVC and BHC consume the candidate micro-particle formulation; 2) determine what size they consume; 3) establish methods to evaluate consumption of filter-feeders for future experiments. Both SVC and BHC were exposed to small (50-100 μm) and large (150-200 μm) micro-particles in two 24-h trials. Particles in water were counted electronically and manually (microscopy). Particles on gill rakers were counted manually and intestinal tracts inspected for the presence of micro-particles. In Trial 1, both manual and electronic count data confirmed reductions of both size particles; SVC appeared to remove more small particles than large; more BHC consumed particles; SVC had fewer overall particles in their gill rakers than BHC. In Trial 2, electronic counts confirmed reductions of both size particles; both SVC and BHC consumed particles, yet more SVC consumed micro-particles compared to BHC. Of the fish that ate micro-particles, SVC consumed more than BHC. It is recommended to use multiple metrics to assess consumption of candidate micro-particles by filter-feeders when attempting to distinguish differential particle consumption. This study has implications for developing micro-particles for species-specific delivery of bioactive controls to help fisheries, provides some methods for further experiments with bioactive micro-particles, and may also have applications in aquaculture.

Journal of Aquaculture Research & Development↗