English Sole Research Articles

Physiological sensitivities to hypoxia differ between co-occurring juvenile flatfishes

Coastal hypoxia threatens estuarine nursery habitat for juvenile demersal fishes worldwide, and is expected to intensify with climate change. This study examines the physiological tolerances of hypoxia in two ecologically and economically important flatfish species that co-occur in a highly eutrophic estuary and biodiversity hotspot on California's central coast, the Elkhorn Slough. Juveniles of English sole (Parophrys vetulus) occur less frequently in areas of the slough where dissolved oxygen (DO) ≤ 4.0 mg/L O2 compared to speckled sanddabs (Citharichthys stigmaeus), suggesting that English sole may be more sensitive to hypoxia. We exposed both species to an ecologically relevant, acute six-hour exposure to six DO levels ranging from ambient to severely hypoxic: 8.0, 6.0, 4.0, 3.0, 2.0, and 1.5 mg/L O2 and measured known physiological and biochemical indicators of hypoxia stress. As DO declined, metabolic rate and aerobic scope decreased for English sole, while anaerobic activity (measured by L-lactate) and ventilation rate increased for both species. Biochemical responses to hypoxia were observed only at very low DO levels (≤ 4.0 mg/L O2), indicating that both species appear to have a higher tolerance for relatively short-term hypoxia than other teleost fishes. Speckled sanddabs increased ventilation rate and anaerobic activity at higher DO levels than English sole, suggesting that earlier onset of compensatory mechanisms may contribute to the greater relative hypoxia tolerance in sanddabs. Examining the link between physiological and ecological thresholds for hypoxia tolerance will help determine suitable nursery habitat areas and management targets for estuarine restoration, and aid in predictions of fishery success under eutrophication and climate change.

Using Hepatic Gene Expression Assays in English Sole (Parophrys vetulus) to Investigate the Effects of Metro Vancouver Wastewater Effluents.

The present study has investigated the effects of Metro Vancouver's wastewater treatment plant (WWTP) effluents on English sole (Parophrys vetulus) hepatic gene expression using novel targeted gene expression assays to complement the 2017 Burrard Inlet Ambient Monitoring Program conducted by Metro Vancouver. Seven locations of varying distance to the WWTPs were included. Twelve genes involved in xenobiotic defense (CYP1A, HSP70), thyroid function (DIO1), lipid and glucose metabolism (FABP1, FASN, GLUT2, PPARδ, PPARγ), protein synthesis (18S rRNA, RPS4X), and reproduction (ERα, VTG) revealed several differences between these impacted sites. A key finding of the present study was that males exhibited VTG transcript levels either equivalent or exceeding female levels of this gene at all sites investigated, indicating widespread exposure of estrogenic contaminants throughout Burrard Inlet. Furthermore, the induction of hepatic CYP1A was observed due to possible downstream sites being subjected to a larger influx of certain planar halogenated and non-halogenated hydrocarbons from multiple industrial contributors. This study also revealed significant differences between the sites examined and in genes involved in transcriptional regulation and synthesis of proteins, lipids and glucose metabolism, and thyroid hormone metabolism. Collectively, this study demonstrates the potential of molecular biomarkers of urban contaminant exposure in wild caught English sole for use in diagnosing a broader range of adverse health effects when combined with conventional whole organism health indicators.

A comparative analysis of sampling methodologies for assessing abundance and distribution of young-of-the-year groundfishes in nearshore soft-sediment habitats

Groundfishes are important species for commercial, recreational, and tribal fisheries along the Pacific Coast of the United States. Understanding the abundance and distribution of these fishes is necessary for successful fisheries management. Many groundfish species spend at least part of their life cycle in nearshore habitats. However, assessing groundfish species assemblages in nearshore habitats can be limited by the relatively small size of young-of-the-year and subadult life history stages, which may not be quantitatively retained with traditional survey gears. In addition, portions of the innermost nearshore (<55 m water depth) can be inaccessible to vessels employed in trawl surveys. To help improve the fishery-independent data informing the current understanding of nearshore assemblages, we compared catches resulting from two different but spatially overlapping surveys. One is the National Oceanic and Atmospheric Administration’s (NOAA) West Coast Groundfish Bottom Trawl Survey (WCGBTS), which is representative of a typical groundfish survey in USA and EU continental shelf habitats. The other is an ad-hoc beam trawl survey along the Newport Hydrographic (NH) Line – an oceanographically well-monitored sampling line off the Pacific Coast. Our objectives were to evaluate the representativeness of nearshore fish communities in the WCGBTS and to assess if additional nearshore sampling would enhance the WCGBTS. For the purposes of this study, “nearshore” is defined as the continental shelf shoreward of 200 m depth. Examining fish catches and environmental variables from both surveys, we found significant differences in fish assemblages, oxygen, temperature, and salinity based on depth, season, year, and survey type. The WCGBTS is designed and well-suited for sampling subadult and adult groundfishes in trawlable habitat. However, year-round sampling of the beam trawl survey allows it to capture ephemeral environmental conditions better than the WCGBTS. The gear type and sampling location make the beam trawl survey better suited than the WCGBTS for sampling smaller individuals and species that live at shallower depths. The beam trawl survey caught 69 unique species or taxa groups within the comparative data subset, whereas the WCGBTS caught 83. The three most commonly occurring species in the beam trawl survey were Pacific sanddab (Citharichthys sordidus), English sole (Parophrys vetulus), and speckled sanddab (Citharichthys stigmaeus), while the WCGBTS most commonly caught rex sole (Glyptocephalus zachirus), Dover sole (Microstomus pacificus), and spotted ratfish (Hydrolagus colliei). Of the fish with measured lengths, the catch from the beam trawl survey had a mode standard length of 2 cm, contrasted with the mode length (total length, fork length, anal length, and natural length combined) of 22 cm for the WCGBTS. We found that there is a transition in species assemblages right where the WCGBTS ends (about 55 m). Thus, while the surveys overlap in some capabilities, this analysis shows that the beam trawl survey or a similar nearshore survey would complement the WCGBTS, providing an enhanced characterization of groundfish assemblages.

Reconstructing trophic position over the past century for five Puget Sound fish species

The comparison of historical and modern food web dynamics allows ecologists to test whether the trophic connectivity we observe today is ‘normal’ in its historical context. Fish densities and abundances have changed across time, making it likely that fish trophic interactions and their trophic positions have also changed. Historical trophic data of marine fishes can now be extracted from the tissues of fluid-preserved specimens held in natural history collections via compound-specific stable isotope analysis of amino acids (CSIA-AA) of nitrogen. We conducted CSIA-AA to quantify trophic position change over the past century in 5 ecologically important fishes of Puget Sound, Washington, USA: Pacific hake Merluccius productus, walleye pollock Gadus chalcogrammus, copper rockfish Sebastes caurinus, English sole Parophrys vetulus, and Pacific herring Clupea pallasii, and examined the canonical trophic (glutamic acid) and source (phenylalanine) amino acids. For all fishes except copper rockfish, trophic position, glutamic acid, and phenylalanine values remained similar across time. For copper rockfish, glutamic acid but not phenylalanine values increased over time, indicating an increase in this species’ trophic position. The observed increase in copper rockfish trophic position may be a function of diet switching and declining prey quality rather than a consequence of rockfish consuming higher trophic level prey. This study leverages more than 100 yr of trophic data of fishes representing various feeding guilds and demonstrates that some fish species may be more trophically resilient to major environmental change than expected. Efforts should be made to identify and conserve the trophic interactions of species experiencing change.

Assessing hydroxylated polycyclic aromatic hydrocarbon (OHPAH) metabolites in bile of English sole (Parophrys vetulus) from Puget Sound, WA, USA by liquid chromatography/tandem mass spectrometry (LC-MS/MS)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are widely monitored in marine biota from urbanized areas, due to their toxicity to aquatic organisms. Teleost fish can quickly metabolize PAHs into hydroxylated forms (OHPAHs) that, in some cases, are more toxic than the parent (unmetabolized) PAHs. But due to this fast metabolism, monitoring traditional parent PAHs in fish can cause underestimation on assessing PAH exposure. In addition, environmental levels of individual OHPAH metabolites are lacking in the literature worldwide. Therefore, we developed a rapid and accurate analytical method in which a number of individual OHPAHs metabolites are measured simultaneously in fish bile, via liquid chromatography coupled with tandem mass spectrometry, including low and high molecular weight mono- and diol-OHPAHs. We analyzed bile samples of 119 English sole (Parophrys vetulus) collected from 14 Puget Sound, WA, USA, sites, which has multiple sources of PAHs, including urban stormwater runoff, wastewater effluents, as well as an inactive creosote facility. The mean (± SD) biliary summed OHPAH (∑OHPAH) concentrations determined in English sole from urban, near-urban, and non-urban sites were 790 ± 1400 (n = 46), 310 ± 330 (n = 44) and 130 ± 200 (n = 29) ng/mL, respectively, with a maximum reaching 9400 ng/mL in a sample from an urban site. We compared these novel biliary OHPAH metabolite data with parent PAHs measured in stomach content of the same individual sole. Biliary ∑OHPAH concentrations were significantly correlated with the levels of ∑PAH in stomach content, however, with major differences in their distribution. We also demonstrated that biliary OHPAH metabolite data in English sole can potentially be used to distinguish different sampling sites due to a specific variety and intensity of PAH sources in the aquatic environment, which makes this a very important analytical approach for assessing PAH exposure in the environment.

Isolation by Distance and Proximity to Urban Areas Affect Genetic Differentiation among Collections of English Sole (Parophrys vetulus, Family Pleuronectidae) in the Northeastern Pacific Ocean and Salish Sea

The English sole (Parophrys vetulus, family Pleuronectidae) is an abundant ground fish used as a sentinel of marine pollution in the inland marine waters of Washington and Oregon. We used 15 microsatellite loci to evaluate patterns of genetic variability within and among 17 collections of sole from coastal sites and within the southern Salish Sea. Over 470 alleles were identified in 15 loci, and high levels of genetic richness, as estimated by expected heterozygosity (HE) and allele richness (AR), were detected. Fish sampled from coastal areas at the northern end of our study area had the lowest values of genetic richness, in contrast to collections at the southern end. The level of differentiation among all collections was low: mean FST value was 0.0006. Nineteen comparisons had statistically significant FST values (mean FST of 0.0029) and involved comparisons involving three locations associated with urban areas (Port Gardner [Everett, WA], Sinclair Inlet [Bremerton, WA], and Commencement Bay [Tacoma, WA]). A statistically significant, but weak, isolation-by-distance pattern was seen in the five coastal collections over 1,100 km of coastline. In the Salish Sea collections, the pattern of differentiation was patchy and marked by several distinctive collections in close proximity to urban areas. The pattern of differentiation in the Salish Sea parallels differences seen in ecotoxicological characteristics of the English sole that inhabit separate urban embayments differing in pollution characteristics. Future work can focus on evaluating the stability and meaningfulness of this subtle variability in a time of local and global environmental changes.

Interplay of temperature and hypoxia in habitat quality for a juvenile demersal fish in a coastal upwelling system

Coastal hypoxia around the world has raised concerns about its sublethal effects on juvenile demersal fishes. We examined the growth rate of juvenile English sole ( Parophrys vetulus) under 15 combinations of temperature and dissolved oxygen levels. We found interactive effects of temperature and hypoxia on fish growth. Fish exposed to moderate hypoxia and normoxia exhibited similar growth responses to increasing temperature; however, a threshold effect was evident under severe hypoxia, which caused a significant reduction in growth. Further, a generalized additive mixed model was applied to simulate fish growth off the Oregon coast during a climate transition from the 2009 El Niño to the 2010–2011 La Niña. Model simulations indicated that habitat quality varied significantly between estuarine (high quality) and coastal (low quality) nurseries. Coastal habitats may remain moderately suitable during El Niño years, while estuarine refuges are more preferred during La Niña years. This study contributes to the assessment of climate change and hypoxic disturbance on demersal fisheries by providing an analytical framework to evaluate synergistic temperature–hypoxia interactions on juveniles in their nursery habitats.

The osmorespiratory compromise in marine flatfish: differential effects of temperature, salinity, and hypoxia on diffusive water flux and oxygen consumption of English sole (Parophrys vetulus) and Pacific sanddab (Citharichthys sordidus)

The osmorespiratory compromise in marine flatfish: differential effects of temperature, salinity, and hypoxia on diffusive water flux and oxygen consumption of English sole (Parophrys vetulus) and Pacific sanddab (Citharichthys sordidus)

Parasite communities in English Sole (Parophrys vetulus) have changed in composition but not richness in the Salish Sea, Washington, USA since 1930.

AbstractEarth is rapidly losing free-living species. Is the same true for parasitic species? To reveal temporal trends in biodiversity, historical data are needed, but often such data do not exist for parasites. Here, parasite communities of the past were reconstructed by identifying parasites in fluid-preserved specimens held in natural history collections. Approximately 2500 macroparasites were counted from 109 English Sole (Parophrys vetulus) collected between 1930 and 2019 in the Salish Sea, Washington, USA. Alpha and beta diversity were measured to determine if and how diversity changed over time. Species richness of parasite infracommunities and community dispersion did not vary over time, but community composition of decadal component communities varied significantly over the study period. Community dissimilarity also varied: prior to the mid-20th century, parasites shifted in abundance in a seemingly stochastic manner and, after this time period, a canalization of community change was observed, where species' abundances began to shift in consistent directions. Further work is needed to elucidate potential drivers of these changes and to determine if these patterns are present in the parasite communities of other fishes of the Salish Sea.

Assessing Hydroxylated Polycyclic Aromatic Hydrocarbon (Ohpah) Metabolites in Bile of English Sole (Parophrys Vetulus) from Puget Sound, Wa, USA by Liquid Chromatography/Tandem Mass Spectrometry (Lc-Ms/Ms)

Assessing Hydroxylated Polycyclic Aromatic Hydrocarbon (Ohpah) Metabolites in Bile of English Sole (Parophrys Vetulus) from Puget Sound, Wa, USA by Liquid Chromatography/Tandem Mass Spectrometry (Lc-Ms/Ms)

Surveillance for Antibiotic-Resistant E. coli in the Salish Sea Ecosystem.

E. coli was isolated from the Salish Sea (Puget Sound) ecosystem, including samples of marine and fresh water, and wildlife dependent on this environment. E. coli isolates were assessed for phenotypic and genotypic resistance to antibiotics. A total of 305 E. coli isolates was characterized from samples collected from: marine water obtained in four quadrants of the Salish Sea; select locations near beaches; fresh water from streams near marine beaches; and fecal samples from harbor porpoises (Phocoena phocoena), harbor seals (Phoca vitulina), river otters (Lontra canadensis), and English sole (Parophrys vetulus). Isolates were evaluated using antimicrobial susceptibility typing, whole-genome sequencing, fumC, and multilocus sequence typing. Resistance and virulence genes were identified from sequence data. Of the 305 isolates from Salish Sea samples, 20 (6.6%) of the E. coli were intermediate, and 31 (10.2%) were resistant to ≥1 class of antibiotics, with 26.9% of nonsusceptible (resistant and intermediate resistant) E. coli isolates from marine mammals and 70% from river otters. The proportion of nonsusceptible isolates from animals was significantly higher than samples taken from marine water (p < 0.0001). A total of 196 unique STs was identified including 37 extraintestinal pathogenic E. coli (ExPEC)-associated STs [ST10, ST38, ST58, ST69, ST73, ST117, ST131, and ST405]. The study suggests that animals may be potential sentinels for antibiotic-resistant and ExPEC E. coli in the Salish Sea ecosystem.

Parasites of the past: 90 years of change in parasitism for English sole

Historical data are extremely rare but essential for ascertaining whether contemporary infectious disease burdens are unusual. Natural history collections are a valuable source of such data, especially for reconstructing long timelines of parasite abundance. We quantified the parasites of 109 museum specimens of English sole (Parophrys vetulus), an economically important flatfish, collected from Puget Sound, Washington, over a 90‐year period (1930–2019). We counted nearly 2,500 individual parasites representing 23 distinct species/morphotypes and four broad taxonomic groupings. Of the 12 taxa that were prevalent enough to include in the analysis, nine did not change in abundance over time, two (an acanthocephalan and a trematode) decreased, and one (another trematode) increased. By broad taxonomic grouping, nematodes, trematodes, and leeches exhibited no change over time, whereas acanthocephalans declined significantly. The diverging patterns among parasite taxa suggest a double‐edged sword of responses to long‐term ocean change: some parasites might be on the rise, while others are declining.

Spatio-temporal patterns in juvenile habitat for 13 groundfishes in the California Current Ecosystem.

Identifying juvenile habitats is critical for understanding a species’ ecology and for focusing spatial fishery management by defining references like essential fish habitat (EFH). Here, we used vector autoregressive spatio-temporal models (VAST) to delineate spatial and temporal patterns in juvenile density for 13 commercially important species of groundfishes off the US west coast. In particular, we identified hotspots with high juvenile density. Three qualitative patterns of distribution and abundance emerged. First, Dover sole Microstomus pacificus, Pacific grenadier Coryphaenoides acrolepis, shortspine thornyhead Sebastolobus alascanus, and splitnose rockfish Sebastes diploproa had distinct, spatially-limited hotspots that were spatially consistent through time. Next, Pacific hake Merluccius productus and darkblotched rockfish Sebastes crameri had distinct, spatially limited hotspots, but the location of these hotspots varied through time. Finally, arrowtooth flounder Atheresthes stomias, English sole Parophrys vetulus, sablefish Anoplopoma fimbria, Pacific grenadier Coryphaenoides acrolepis, lingcod Ophiodon elongatus, longspine thornyhead Sebastolobus altivelis, petrale sole Eopsetta jordani, and Pacific sanddab Citharichthys sordidus had large hotspots that spanned a broad latitudinal range. These habitats represent potential, if not likely, nursery areas, the location of which will inform spatial management.

Fluid preservation causes minimal reduction of parasite detectability in fish specimens: A new approach for reconstructing parasite communities of the past?

Long‐term datasets are needed to evaluate temporal patterns in wildlife disease burdens, but historical data on parasite abundance are extremely rare. For more than a century, natural history collections have been accumulating fluid‐preserved specimens, which should contain the parasites infecting the host at the time of its preservation. However, before this unique data source can be exploited, we must identify the artifacts that are introduced by the preservation process. Here, we experimentally address whether the preservation process alters the degree to which metazoan parasites are detectable in fluid‐preserved fish specimens when using visual parasite detection techniques. We randomly assigned fish of three species (Gadus chalcogrammus, Thaleichthys pacificus, and Parophrys vetulus) to two treatments. In the first treatment, fish were preserved according to the standard procedures used in ichthyological collections. Immediately after the fluid‐preservation process was complete, we performed parasitological dissection on those specimens. The second treatment was a control, in which fish were dissected without being subjected to the fluid‐preservation process. We compared parasite abundance between the two treatments. Across 298 fish individuals and 59 host–parasite pairs, we found few differences between treatments, with 24 of 27 host–parasite pairs equally abundant between the two treatments. Of these, one pair was significantly more abundant in the preservation treatment than in the control group, and two pairs were significantly less abundant in the preservation treatment than in the control group. Our data suggest that the fluid‐preservation process does not have a substantial effect on the detectability of metazoan parasites. This study addresses only the effects of the fixation and preservation process; long‐term experiments are needed to address whether parasite detectability remains unchanged in the months, years, and decades of storage following preservation. If so, ecologists will be able to reconstruct novel, long‐term datasets on parasite diversity and abundance over the past century or more using fluid‐preserved specimens from natural history collections.

The gaseous gastrointestinal tract of a seawater teleost, the English sole (Parophrys vetulus)

There has been considerable recent progress in understanding the respiratory physiology of the gastrointestinal tract (GIT) in teleosts, but the respiratory conditions inside the GIT remain largely unknown, particularly the luminal PCO2 and PO2 levels. The GIT of seawater teleosts is of special interest due to its additional function of water absorption linked to HCO3− secretion, a process that may raise luminal PCO2 levels. Direct measurements of GIT PCO2 and PO2 using micro-optodes in the English sole (Parophrys vetulus; anaesthetized, artificially ventilated, 10–12 °C) revealed extreme luminal gas levels. Luminal PCO2 was 14–17 mmHg in the stomach and intestinal segments of fasted sole, considerably higher than arterial blood levels of 5 mmHg. Moreover, feeding, which raised intestinal HCO3− concentration, also raised luminal PCO2 to 34–50 mmHg. All these values were higher than comparable measurements in freshwater teleosts, and also greater than environmental CO2 levels of concern in aquaculture or global change scenarios. The PCO2 values in subintestinal vein blood draining the GIT of fed fish (28 mmHg) suggested some degree of equilibration with high luminal PCO2, whereas subintestinal vein PO2 levels were relatively low (9 mmHg). All luminal sections of the GIT were virtually anoxic (PO2 ≤ 0.3 mmHg), in both fasted and fed animals, a novel finding in teleosts.

110 - Emerging adults – a challenge for an integrated psychosomatic approach

There has been considerable recent progress in understanding the respiratory physiology of the gastrointestinal tract (GIT) in teleosts, but the respiratory conditions inside the GIT remain largely unknown, particularly the luminal PCO2 and PO2 levels. The GIT of seawater teleosts is of special interest due to its additional function of water absorption linked to HCO3− secretion, a process that may raise luminal PCO2 levels. Direct measurements of GIT PCO2 and PO2 using micro-optodes in the English sole (Parophrys vetulus; anaesthetized, artificially ventilated, 10–12 °C) revealed extreme luminal gas levels. Luminal PCO2 was 14–17 mmHg in the stomach and intestinal segments of fasted sole, considerably higher than arterial blood levels of 5 mmHg. Moreover, feeding, which raised intestinal HCO3− concentration, also raised luminal PCO2 to 34–50 mmHg. All these values were higher than comparable measurements in freshwater teleosts, and also greater than environmental CO2 levels of concern in aquaculture or global change scenarios. The PCO2 values in subintestinal vein blood draining the GIT of fed fish (28 mmHg) suggested some degree of equilibration with high luminal PCO2, whereas subintestinal vein PO2 levels were relatively low (9 mmHg). All luminal sections of the GIT were virtually anoxic (PO2 ≤ 0.3 mmHg), in both fasted and fed animals, a novel finding in teleosts.

The residency, movement patterns and habitat association of several demersal fish species to the Orange County Sanitation District wastewater outfall

Abstract Wastewater outfall pipes are structures that may attract marine fishes, yet previous studies that address the risks of exposure to wastewater effluent rarely account for the movements of the species studied. This study used acoustic telemetry to quantify the movement patterns and habitat association of demersal species (Citharichthys sordidus, Pleuronichthys verticalis, Parophrys vetulus, Sebastes miniatus) at two sites (near a wastewater outfall and at a reference site) in southern California over one year. Residencies to both sites were low for pleuronectiform fishes (C. sordidus, P. verticalis, P. vetulus, less than 10% of the study duration was spent in either site), which indicates that tissue samples from these species likely reflect the accumulation of contaminants across individuals’ ranges, not just the outfall site. Alternatively, S. miniatus showed higher degrees of residency to the outfall site (nearly 40% of the study duration) and may be the most susceptible to wastewater effluent effects.

Variability in Juvenile English Sole Condition Relative to Temperature and Trophic Dynamics Along an Oregon Estuarine Gradient

Many benthic fish and invertebrates, including the flatfish English sole (Parophrys vetulus), utilize estuaries as nursery habitat during their juvenile life stage. Regions within an estuary differ with respect to salinity, temperature, oxygen, and organic inputs, highlighting the complexity of nursery habitat and the need to assess multiple habitats within a single estuary. To determine the effect of variable estuarine habitat on juvenile English sole, we examined morphometric and energetic (lipid) condition, fatty acids, and stable isotopes (13C and 15N) of wild-caught juveniles from upriver and downriver habitats within the Yaquina Bay, Oregon estuary. Downriver-caught fish exhibited higher energetic condition, which may be attributed to cooler temperatures and the marine-sourced carbon that typified that region’s food web. Conversely, individuals from the upriver habitat exhibited higher morphometric condition. This may be due in part to the warmer temperatures upriver that have been observed to promote growth and suppress lipid storage in other marine species. Our findings highlight the important but variable contribution of both upriver and downriver habitats to English sole early life history.

Scale Thickness Predicts Skin Puncture-Force Resistance in Three Pleuronectiform Fishes.

SynopsisIn fishes, the skin and scales provide a physical barrier to the external environment and must withstand direct physical insult from biotic and abiotic features of the habitat. Flatfishes likely rely heavily on their scales for physical defense because they rest directly on the substrate. Using a flatfish model, we asked: what are the effects of scale type and scale morphology on puncture force resistance? We also asked: are there morphological and functional differences between the eyed and blind sides in flatfishes and do the morphological and functional properties of scales vary with organism size? Using a large size range of three species of Pleuronectid flatfish (Isopsetta isolepis, n = 10; Parophrys vetulus, n = 10; and Platichthys stellatus, n = 12), we measured the force required to puncture the integument using a sample of skin+scales taken from the eyed and blind side of each individual. We also measured the diameter, area, and thickness of the scales of each individual. Scaling relationships (body length vs. variable of interest) were derived for each species and compared with a priori expectations of geometric similarity. We found no relationship between scale type and puncture resistance and no differences in morphological parameters or puncture resistance between the eyed and blind side within a given species. These flatfish species do vary in their ability to withstand puncture forces; however, once scale thickness is taken into account, species differences disappear. Thus, the ability of a flatfish to withstand mechanical insult from puncture-forces varies depending on the thickness of the scale.

Abundance of an economically important nematode parasite increased in Puget Sound between 1930 and 2016: Evidence from museum specimens confirms historical data

Abstract Does disturbance increase or decrease parasite transmission among wildlife hosts? Ecologists cannot answer this controversial question, in part because few historical datasets rigorously document parasite abundance. Without such a baseline, it is difficult to determine whether contemporary ecosystems are experiencing elevated parasite burdens. Here, we investigate change over time in the abundance of a parasite that affects the economic value of a fish species. Clavinema mariae is a nematode parasite of benthic fishes that is common in English sole (Parophrys vetulus) of Puget Sound, WA. We obtained historical records of its abundance from the literature and from unpublished government agency data, and resampled the same locations using the same methods in 2017. We also used a new approach by estimating the C. mariae burden for museum specimens of English sole collected between 1930 and 2016. Both the historical data and museum specimen data suggested increases over time in C. mariae abundance, with robust agreement between the two approaches. In addition to documenting a previously unrecognised ~eightfold increase in the burden of an economically important parasite, our work demonstrates—for the first time—that parasitological examination of liquid‐preserved museum specimens can produce reliable data on long‐term trends in parasite abundance, at a much greater temporal resolution than is possible to obtain from historical records. Synthesis and applications. Defining a baseline state of infection is vital for natural resource management and policy, which must respond to the threat of disease; without such a baseline, managers attempting to maintain or recover the health of ecosystems under their stewardship are shooting in the dark. The method we present here—using museum specimens to reconstruct detailed chronologies of parasite abundance change—offers a solution. Our approach would allow managers to accurately characterise past disease states, informing the development of appropriate disease management targets. Given the broad representation and availability of liquid‐preserved specimens across ecosystems, geographic regions and host taxa, this solution may be feasible for the management of biological resources not only in marine ecosystems, but in freshwater and terrestrial ecosystems as well.