Staghorn Sculpin Research Articles

Распределение рыб семейства Cottidae в юго-восточной части Баренцева моря (к западу от о. Долгий)

The distribution of Cottidae species in the southwestern part of the Barents Sea (Pechora Sea) based on materials from ichthyological surveys carried out in the summer of 2010–2023 is shown. Cottidae species were maximum 1.7 % of the total catch. A total of 7 species have been noted. The most abundant Cottidae species in Pechora Sea is arctic staghorn sculpin G. tricuspis (85 % frequency of occurrence), shorthorn sculpin M. scorpius (62 %) and ribbed sculpin T. pingelii (46 %). Values of the total abundance of the Cottidae was diverse: 1.2 to 757.6 ind/km2 and 0.002 to 21.906 kg/km2.

Stable isotopes reveal intertidal fish and crabs use bivalve farms as foraging habitat in Puget Sound, Washington

Bivalves such as oysters and clams have been farmed in intertidal zones across the Puget Sound region of the Salish Sea for thousands of years. The variety of gear types used on bivalve farms creates complex vertical structure and attachment points for aquatic epiphytes and invertebrates which increases habitat structural complexity, but may alter eelgrass cover in areas where bivalve farms and eelgrass meadows overlap. Eelgrass meadows are highly productive and ecologically foundational nearshore habitats that provide valuable ecosystem services including the provision of nursery, refuge, and foraging habitat. Aquaculture has been a key feature of the environment in the Puget Sound for millennia, however, little is known about how well aquaculture practices are integrated into the system, and what services they provide to mobile species assemblages relative to unfarmed eelgrass meadows. We used stable isotope mixing models to estimate, for several species of nearshore fish and crab in two areas of North Puget Sound, Washington, the percent diet originating from either a natural bottom habitat (eelgrass meadows), farm habitat (oyster farms), or pelagic planktonic sources. Our results indicate that several species of nearshore fish such as surf perch and staghorn sculpin derive a significant proportion of their diets from farm areas, while crabs derive most of their diets from eelgrass habitat, and stickleback derive a significant proportion of their diets from planktonic sources. The results indicate that foraging habitat uses are species specific, and that several species that spatially overlap bivalve farms obtained a large percentage of their diets from adjacent bivalve farm habitat.

Invasive European green crab (Carcinus maenas) predation in a Washington State estuary revealed with DNA metabarcoding.

Predation by invasive species can threaten local ecosystems and economies. The European green crab (Carcinus maenas), one of the most widespread marine invasive species, is an effective predator associated with clam and crab population declines outside of its native range. In the U.S. Pacific Northwest, green crab has recently increased in abundance and expanded its distribution, generating concern for estuarine ecosystems and associated aquaculture production. However, regionally-specific information on the trophic impacts of invasive green crab is very limited. We compared the stomach contents of green crabs collected on clam aquaculture beds versus intertidal sloughs in Willapa Bay, Washington, to provide the first in-depth description of European green crab diet at a particularly crucial time for regional management. We first identified putative prey items using DNA metabarcoding of stomach content samples. We compared diet composition across sites using prey presence/absence and an index of species-specific relative abundance. For eight prey species, we also calibrated metabarcoding data to quantitatively compare DNA abundance between prey taxa, and to describe an 'average' green crab diet at an intertidal slough versus a clam aquaculture bed. From the stomach contents of 61 green crabs, we identified 54 unique taxa belonging to nine phyla. The stomach contents of crabs collected from clam aquaculture beds were significantly different from the stomach contents of crabs collected at intertidal sloughs. Across all sites, arthropods were the most frequently detected prey, with the native hairy shore crab (Hemigrapsus oregonensis) the single most common prey item. Of the eight species calibrated with a quantitative model, two ecologically-important native species-the sand shrimp (Crangon franciscorum) and the Pacific staghorn sculpin (Leptocottus armatus)-had the highest average DNA abundance when detected in a stomach content sample. In addition to providing timely information on green crab diet, our research demonstrates the novel application of a recently developed model for more quantitative DNA metabarcoding. This represents another step in the ongoing evolution of DNA-based diet analysis towards producing the quantitative data necessary for modeling invasive species impacts.

Growth of Pacific staghorn sculpin (Leptocottus armatus) is reduced at contaminated sites in the Lower Duwamish River, Washington

The Lower Duwamish River is a highly industrialized waterway flowing into the densely urbanized Puget Sound waterfront of Seattle, Washington, USA. The river has been profoundly altered from its natural state following more than a century of channelization, recurrent dredging, shoreline armoring, and pollution discharges. As part of a Natural Resource Damage Assessment addressing historical pollution at three designated Superfund sites (i.e., the assessment area), juvenile Pacific staghorn sculpin (Leptocottus armatus) were sampled throughout the lower river in order to evaluate injury from exposure to polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), and butyltins (BTs). Sculpin live in close association with the river sediments within and upriver of the assessment area. Fish were collected for analysis of contaminant concentrations in composited whole bodies and stomach contents, as well as individual fish health metrics including daily somatic growth rates measured from otoliths. Sediment contaminant concentrations were also measured at sites near to fishing locations. Fish growth rates varied from 0.65 to 1.05 mm/day, and were significantly lower at unremediated downriver sites compared to upriver and remediated locations. Sculpin growth rates were negatively correlated with concentrations of PCBs in fish bodies, PAHs in stomach contents, as well as PCBs, DDTs and PAHs in sediment. Mixed effects models for whole-body and stomach content contaminants showed positive correlations between growth rate and water temperature. Temperature was not a significant confounding variable for the relationship between growth rate and sediment contaminants. Overall, these results show that juvenile sculpin are harmed by contaminant exposure in the Lower Duwamish River. Furthermore, this study demonstrates the utility of using paired biological and chemical indicators of pollutant-induced injury in a resident fish to inform a complex Natural Resource Damage Assessment and associated restoration efforts.

The physiological consequences of a very large natural meal in a voracious marine fish, the staghorn sculpin (Leptocottus armatus).

Little information exists on physiological consequences when wild fish eat natural food. Staghorn sculpins at 10-13°C voluntarily consumed 15.8% of their body mass in anchovies. Gastric clearance was slow with >60% of the meal retained in the stomach at 48 h, and was not complete until 84 h. At 14-24 h post-feeding, pH was depressed by 3 units and Cl- concentration was elevated 2-fold in gastric chyme, reflecting HCl secretion, while in all sections of the intestine, pH declined by 1 pH unit but Cl- concentration remained unchanged. PCO2and total ammonia concentration were greatly elevated throughout the tract, whereas PNH3and HCO3- concentration were depressed. Intestinal HCO3- secretion rates, measured in gut sacs in vitro, were also lower in fed fish. Whole-animal O2 consumption rate was elevated approximately 2-fold for 72 h post-feeding, reflecting 'specific dynamic action', whereas ammonia and urea-N excretion rates were elevated about 5-fold. Arterial blood exhibited a modest 'alkaline tide' for about 48 h, but there was negligible excretion of metabolic base to the external seawater. PaCO2and PaO2remained unchanged. Plasma total amino acid concentration and total lipid concentration were elevated about 1.5-fold for at least 48 h, whereas small increases in plasma total ammonia concentration, PNH3and urea-N concentration were quickly attenuated. Plasma glucose concentration remained unchanged. We conclude that despite the very large meal, slow processing with high efficiency minimizes internal physiological disturbances. This differs greatly from the picture provided by previous studies on aquacultured species using synthetic diets and/or force-feeding. Questions remain about the role of the gastro-intestinal microbiome in nitrogen and acid-base metabolism.

Сведения о росте и возрасте арктического шлемоносного бычка Gymnocanthus tricuspis (Reinhardt, 1830) в Карском море

This article provides data on size-age composition and growth rate of arctic staghorn sculpin Gymnocanthus tricuspis (Reinhardt, 1830) in the Kara Sea. Sculpins aged from 1+ to 7+ years, total length (TL) 4.5–19.5 cm long, and weighing 0.8–111.0 g were registered in catches. It is known that during the first three years of life, body sizes of males and females of this species are comparable, but from the fourth year onwards, females grow much faster; that’s the reason why length and weight of fish with the same age may be significantly different. Individuals of G. tricuspis with a TL 9.0–11.0 сm and age 4+ dominated.

Характеристика прибрежной ихтиофауны губ Восточного Мурмана в летний период 2020 года

In the article was considered species composition of fish in the littoral and sublittoral zones of Yarnyshnaya and Zelenetskaya bays (Barents Sea) during summer 2020. For the first time, the kelp snailfish Liparis tunicatus was recorded in the studied water area. At whole was discovered 15 species of fish and most abundent between them is staghorn sculpin Gymnocanthus tricuspis and shorthorn sculpin Myoxocephalus scorpius. Also quantitative characteristics of the distribution for each fish species are represented. The dynamics of abundance and diversity of coastal fish communities were analyzed. Comparing of perennial data with 2020 indicates that at the present observed relatively rich species composition, low fish distribution density, low abundance of young Gadidae, but high indicators of biodiversity in coastal communities.

Northeast Pacific eelgrass fish communities characterized by environmental DNA represent local diversity and show habitat specificity

AbstractFish biodiversity is an important indicator of ecosystem health and a priority for the National Park Service in Drakes Estero, a shallow estuary within Point Reyes National Seashore, Marin County, California. However, fish diversity has yet to be described following the removal of oyster aquaculture infrastructure within Drakes Estero from 2016 to 2017. We used environmental DNA (eDNA) to characterize fish biodiversity within Drakes Estero. We amplified fish eDNA with MiFish primers and classified sequences with a 12S rRNA reference database. We identified 110 unique operational taxonomic units (OTUs, at 97% similarity) within the estuary from 40 samples across 4 sites. From these 110 OTUs, we identified 9 species and 13 taxonomic groups at the genus, family, order, or class level within the estuary. Species‐level assignments are limited by a lack of representative sequences targeted by the MiFish primers for 42% of eelgrass fishes in our region that we identified from a literature review in the Northeast Pacific (NEP) from Elkhorn Slough to Humboldt Bay. Despite this limitation, we identified some common Drakes Estero fishes with our eDNA surveys, including the three‐spined stickleback (Gasterosteus aculeatus), Pacific staghorn sculpin (Leptocottus armatus), surfperches (Embiotocidae), gobies (Gobiidae), and a hound shark (Triakidae). We also compared fish biodiversity within the estuary with that from nearby Limantour Beach, a coastal site. Limantour beach differed in community composition from Drakes Estero and was characterized by high relative abundances of anchovy (Engraulis sp.) and herring (Clupea sp.). Thus, we can distinguish estuarine and non‐estuarine sites (<10 km away) with eDNA surveys. Further, eDNA surveys accounted for greater fish diversity than seine surveys conducted at one site within the estuary. Environmental DNA surveys will likely be a useful tool to monitor fish biodiversity across eelgrass estuaries in the Northeast Pacific, especially as reference databases become better populated with regional species.

PTEROBDELLA OCCIDENTALIS N. SP. (HIRUDINIDA: PISCICOLIDAE) FOR P. ABDITOVESICULATA (MOORE, 1952) FROM THE LONGJAW MUDSUCKER, GILLICHTHYS MIRABILIS, AND STAGHORN SCULPIN, LEPTOCOTTUS ARMATUS, AND OTHER FISHES IN THE EASTERN PACIFIC.

Pterobdella occidentalis n. sp. (Hirudinida: Piscicolidae) is described from the longjaw mudsucker, Gillichthys mirabilis Cooper, 1864, and the staghorn sculpin, Leptocottus armatus Girard, 1854, in the eastern Pacific, and the diagnosis of Pterobdella abditovesiculata (Moore, 1952) from the 'o'opu 'akupa, Eleotris sandwicensis Vaillant and Sauvage, 1875, from Hawaii is amended. The morphology of both species conforms with the genus Pterobdella in possessing a spacious coelom, well-developed nephridial system, and 2 pairs of mycetomes. Originally described as Aestabdella abditovesiculata, P. occidentalis (present along the U.S. Pacific Coast), can be distinguished from most congeners by its metameric pigmentation pattern and diffuse pigmentation on the caudal sucker. Based on mitochondrial gene sequences, including cytochrome c oxidase subunit I (COI) and NADH dehydrogenase subunit I (ND1), P. occidentalis forms a distinct polyphyletic clade with Pterobdella leiostomi from the western Atlantic. Based on COI, ND1, and the 18S rRNA genes, other leech species most closely related to P. occidentalis include Pterobdella arugamensis from Iran, Malaysia, and possibly Borneo, which likely represent distinct species, and Pterobdella abditovesiculata from Hawaii, one of only a few endemic fish parasites in Hawaii. Like P. abditovesiculata, P. arugamensis, and Petrobdella amara, P. occidentalis is often found in estuarine environments, frequently infecting hosts adapted to a wide range of salinity, temperature, and oxygen. The physiological plasticity of P. occidentalis and the longjaw mudsucker host, and the ease of raising P. occidentalis in the lab, make it an excellent candidate for the study of leech physiology, behavior, and possible bacterial symbionts.

Small but Abundant: Distribution and Biology of Arctic Staghorn Sculpin Gymnocanthus tricuspis (Cottidae) in the Kara Sea

Small but Abundant: Distribution and Biology of Arctic Staghorn Sculpin Gymnocanthus tricuspis (Cottidae) in the Kara Sea

Анализ сходства состава пищи арктического шлемоносного бычка Gymnocanthus tricuspis (Reinhardt, 1830) с некоторыми непромысловыми видами рыб Карского моря

This article provides data on diet composition of arctic staghorn sculpin Gymnocanthus tricuspis (Reinhardt, 1830) in the Kara Sea in the 2012, 2015, 2016. This species is a typical benthivorous fish whose diet in the Kara Sea is based on polychaetas, isopods and cumaceans. The similarity of arctic staghorn sculpin diet with other representatives of non-commercial fish of the Kara Sea was considered. Closest trophic species were identified, such as atlantic hookear sculpin, arctic alligatorfish, spatulate sculpin.

Escaping from multiple visual threats: modulation of escape responses in Pacific staghorn sculpin (Leptocottus armatus).

Fish perform rapid escape responses to avoid sudden predatory attacks. During escape responses, fish bend their bodies into a C-shape and quickly turn away from the predator and accelerate. The escape trajectory is determined by the initial turn (stage 1) and a contralateral bend (stage 2). Previous studies have used a single threat or model predator as a stimulus. In nature, however, multiple predators may attack from different directions simultaneously or in close succession. It is unknown whether fish are able to change the course of their escape response when startled by multiple stimuli at various time intervals. Pacific staghorn sculpin (Leptocottus armatus) were startled with a left and right visual stimulus in close succession. By varying the timing of the second stimulus, we were able to determine when and how a second stimulus could affect the escape response direction. Four treatments were used: a single visual stimulus (control); or two stimuli coming from opposite sides separated by a 0 ms (simultaneous treatment), 33 ms or 83 ms time interval. The 33 ms and 83 ms time intervals were chosen to occur either side of a predicted 60 ms visual escape latency (i.e. during stage 1). The 0 ms and 33 ms treatments influenced both the escape trajectory and the stage 1 turning angle, compared with a single stimulation, whereas the 83 ms treatment had no effect on the escape trajectory. We conclude that Pacific staghorn sculpin can modulate their escape trajectory only between stimulation and the onset of the response, but the escape trajectory cannot be modulated after the body motion has started.

Seasonal and interannual variation in high-latitude estuarine fish community structure along a glacial to non-glacial watershed gradient in Southeast Alaska

Along the Gulf ofAlaska, rapid glacier retreat has driven changes in transport of freshwater, sediments, and nutrients to estuary habitats. Over the coming decades, deglaciation will lead to a temporary increase, followed by a long-term decline of glacial influence on estuaries. Therefore, quantifying the current variability in estuarine fish community structure in regions predicted to be most affected by glacier loss is necessary to anticipate future impacts. We analyzed fish community data collected monthly (April through September) over 7 years (2013–2019) from glacially influenced estuaries along the southeastern Gulf of Alaska. River delta sites within estuaries were sampled along a natural gradient of glacial to non-glacial watersheds to characterize variation in fish communities exposed to varying degrees of glacial influence. Differences in seasonal patterns of taxa richness and abundance between the most and least glacially influenced sites suggest that hydrological drivers influence the structure of delta fish communities. The most glacially influenced sites had lower richness but higher abundance overall compared to those with least glacial influence; however, differences among sites were small compared to differences across months. Two dominant species—Pacific staghorn sculpin and starry flounder—contributed most to spatial and temporal variation in community composition; however, given only small interannual differences in richness and abundance over the period of the study, we conclude that year-to-year variation at these sites is relatively low at present. Our study provides an important benchmark against which to compare shifts in fish communities as watersheds and downstream estuaries continue to transform in the coming decades.

Environmental Drivers of Nearshore Fish Community Composition and Size Structure in Glacially Influenced Gulf of Alaska Estuaries

Coastal ecosystems in Alaska are undergoing rapid change due to warming and glacier recession. We used a natural gradient of glacierized to non-glacierized watersheds (0–60% glacier coverage) in two regions along the Gulf of Alaska—Kachemak Bay and Lynn Canal—to evaluate relationships between local environmental conditions and estuarine fish communities. Multivariate analyses of fish community data collected from five sites per region in 2019 showed that region accounted for the most variation in community composition, suggesting that local effects of watershed type were masked by regional-scale variables. Seasonal shifts in community composition were driven largely by the influx of juvenile Pacific salmon (Oncorhynchus spp.) in late spring. Spatiotemporal differences among fish communities were partly explained by salinity and temperature, which accounted for 19.5% of the variation in community composition. We used a multi-year dataset from Lynn Canal (2014–2019) to examine patterns of mean length for two dominant species. Generalized additive mixed models indicated that Pacific staghorn sculpin (Leptocottus armatus) mean length varied along site-specific seasonal gradients, increasing gradually through the summer in the least glacially influenced sites and increasing rapidly to an asymptote of ~ 150 mm in the most glacially influenced sites. Starry flounder (Platichthys stellatus) mean length was more strongly related to environmental conditions, increasing with temperature and turbidity. Together, our findings suggest that community compositions of estuarine fishes show greater variation at the regional scale than the watershed scale, but species-specific variation in size distributions may indicate differences in habitat quality across watershed types within regions.

A phylogeny based on cytochrome-c oxidase gene sequences identifies sympatric Ichthyophonus genotypes in the NE Pacific Ocean.

In recent decades, evidence has accumulated to suggest that the widespread and highly variable parasite Ichthyophonus hoferi is actually a species complex. Highly plastic morphology and a general lack of defining structures has contributed to the likely underestimate of biodiversity within this group. Molecular methods are a logical next step in the description of these parasites, but markers used to date have been too conserved to resolve species boundaries. Here we use mitochondrial encoded cytochrome-c oxidase (MTCO1) gene sequences and phylogenic analysis to compare Ichthyophonus spp. isolates from several marine and anadromous fish hosts. The resulting phylogeny displays lineage separation among isolates and possible host/niche segregation not previously described. The parasite type that infects Pacific herring Clupea pallasii, Atlantic herring C. harengus, Atlantic salmon Salmo salar, and Pacific staghorn sculpin Oligocottus maculosus (Clade A) is different from that which infects Chinook salmon Oncorhynchus tshawytscha, walleye pollock Gadus chalcogrammus, Greenland halibut Reinhardtius hippoglossoides, and Pacific halibut Hippoglossus stenolepsis (Clade B). MTCO1 sequences confirmed the presence of a more divergent Ichthyophonus sp. isolated from American shad Alosa sapidissima in rivers of eastern North America (Clade C), while American shad introduced to the Pacific Ocean are infected with the same parasite that infects Pacific herring (Clade A). Currently there are no consensus criteria for delimiting species within Ichthyophonidae, but MTCO1 sequences hold promise as a potential species identifying marker and useful epizootiological tool.

ИССЛЕДОВАНИЕ ТЕХНОХИМИЧЕСКОЙ ХАРАКТЕРИСТИКИ ДАЛЬНЕВОСТОЧНОГО ШЛЕМОНОСЦА (GYMNOCANTHUS HERZENSTEINI)

The article considers the problem of the rational use of aquatic biological resources in the modern fishing process, which can be partially solved by the complex processing of hydrobionts, the by-catch being underutilized. Gobies or sculpins make about 22% of the by-catch in the catch of commercial fish species in the Far Eastern fishery basin. It is a promising fishing object, the biological value of which was studied earlier and proved in the recent studies. Despite the available reserves, gobies are not used for developing the food products or feed flour. The frequent reasons for low demand for products from such non-commercial raw materials can be: the lack of modern data on the chemical composition of the edible part, data on biological safety, methods of technological processing of raw materials and technology for obtaining food products. There are presented the study results on the size, mass and technological characteristics of Far Eastern stag-horn sculpin belonging to gobies Cottidae Gymnocanthus (Gymnocanthus Herzensteini). There is shown the relationship between the fish mass and the mass of muscle tissue, between the fish length and weight, and the fish weight and mass of the head. The yield of secondary raw materials (heads, entrails, bones, fins) has been determined. Based on the conducted chemical analysis, it was found out that Far Eastern staghorn sculpin belongs to the protein species of fish (19%) with a low lipid content (up to 2%). For the first time, the amino acid and fatty acid composition of proteins and lipids of fish muscle tissue has been investigated. It has been stated that the muscle tissue contains all essential amino acids, the rate of which is more than 100%. The objective indicators of the biological value of muscle tissue proteins were determined: the coefficients of difference between the amino acid rate, utility of amino acids, protein-water and lipid-protein coefficients were calculated. The content of macro- and micro-elements has been studied. It was inferred that the maximum permissible concentration of arsenic, cadmium, mercury and lead do not exceed the maximum permissible level.

Effects of Estuary-Wide Seagrass Loss on Fish Populations

Globally, habitat loss in coastal marine systems is a major driver of species decline, and estuaries are particularly susceptible to loss. Along the United States Pacific coast, monospecific eelgrass (Zostera marina) beds form the major estuarine vegetated habitat. In Morro Bay, California, eelgrass experienced an unprecedented decline of > 95%, from 139 ha in 2007 to < 6 ha by 2017. Fish populations were compared before and after the eelgrass decline using trawl surveys. Beach seines surveys were also conducted during the post-decline period to characterize species within and outside of remnant eelgrass beds. While the estuary-wide loss of eelgrass did not result in fewer fish or less biomass, it led to changes in species composition. The post-eelgrass decline period was characterized by increases in flatfish (mainly Citharichthys stigmaeus) and staghorn sculpin (Leptocottus armatus), and decreases in habitat specialists including bay pipefish (Syngnathus leptorhynchus) and shiner perch (Cymatogaster aggregata). There were similar trends inside and outside of remnant eelgrass patches. These findings support evidence across multiple ecosystems suggesting that the predominance of habitat-specialists predicts whether or not habitat loss leads to an overall decline in fish abundance. In addition, loss of critical habitats across seascapes can restrict population connectivity and lead to range contraction. For bay pipefish, the loss of eelgrass in Morro Bay is likely to create a population biogeographic divide. Currently, Morro Bay is dominated by flatfish and sculpins, and the longevity of this new ecosystem state will depend on future eelgrass recovery dynamics supported by ecosystem-based management approaches.

On the edge: assessing fish habitat use across the boundary between Pacific oyster aquaculture and eelgrass in Willapa Bay, Washington, USA

Estuaries are subject to diverse anthropogenic stressors, such as shellfish aquaculture, which involve extensive use of estuarine tidelands. Pacific oyster Crassostrea gigas aquaculture is a century-old practice in US West Coast estuaries that contributes significantly to the regional culture and economy. Native eelgrass Zostera marina also commonly occurs in intertidal areas where oyster aquaculture is practiced. Eelgrass is federally protected in the USA as ‘essential fish habitat’, restricting aquaculture activities within or near eelgrass. To contribute scientific information useful for management decisions, we sought to compare fish habitat use of oyster aquaculture and eelgrass, as well as the edges between these 2 habitats, in Willapa Bay, Washington, USA. Furthermore, given a recent shift towards off-bottom culture methods, in part to protect seagrasses, long-line and on-bottom oyster aquaculture habitats were compared. A combination of direct (underwater video, minnow traps) and indirect (predation tethering units, eelgrass surveys) methods were employed to characterize differences in fish habitat use. Eelgrass density declined within both aquaculture habitats but less so within long-line aquaculture. Most fish species in our study used long-line oyster aquaculture and eelgrass habitats similarly with minimal edge effects, and on-bottom aquaculture was used less than either of the other 2 habitat types. These results are consistent with previously observed positive relationships between fish abundance and vertical habitat structure, but also reveal species-specific behavior; larger mesopredators like Pacific staghorn sculpins were sighted more often in aquaculture than in interior eelgrass habitats.

Temporal and habitat differences in the juvenile demersal fish community at a marine-dominated northeast Pacific estuary

The role that west coast estuarine habitats play in the early life history of many nearshore marine fishes is poorly understood, in part due to the limited temporal sampling of estuarine habitats. To begin to understand this role, we compared the juvenile demersal fish community between two habitat types at a marine-dominated estuary on the northeast Pacific coast and examined how community structure changed temporally. Sampling occurred in Yaquina Bay, Oregon during 2008–2009, 2012–2013, and 2016–2017 at eleven sites, comprised of anthropogenic (dock) and natural (eelgrass) habitats. The juvenile fish assemblage was dominated by a few highly abundant species, including saddleback gunnel (Pholis ornata), Pacific staghorn sculpin (Leptocottus armatus), and rockfishes (Sebastes spp.), with the majority of species being marine associated. Community structure varied among years and between habitat types, with greater differences seen between habitat types than years. Docks appear to be a specialized habitat, supporting some species but with greater change in community structure over time and lower overall abundances than eelgrass. Use of docks by commercially and recreationally-exploited species, though, indicates potential importance. Community structure differences were best described by a combination of regional (Pacific Decadal Oscillation) and local (upwelling, temperature, salinity) climate variables, but correlation values are considered weak. Greater abundances and reduced change in communities over time at eelgrass sites suggests that maintaining these habitats is potentially critical for many estuary-rearing species, and temporal changes in these communities highlight the importance of long-term monitoring.

Transmission of a Freshwater Isolate of Ichthyophonus (Clade C) to Two Marine Fish Species.

The ingestion of infected prey is the most recognizable mode of transmission for Ichthyophonus, but because this mode of transmission is unidirectional from small prey fish to larger predators, it cannot sustain the parasite within or among populations nor does it explain transmission to planktivores. Recently, waterborne transmission was demonstrated in cultured Rainbow Trout Oncorhynchus mykiss, which could explain how the parasite is transmitted without piscivory. However, it is possible that this is an adaptation to aquaculture conditions, and may not occur among wild fish. To address this question, experiments were conducted to determine if a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species, as well as if transmission is possible between different marine species. Pacific Staghorn Sculpins Leptocottus armatus were fed a freshwater isolate of Ichthyophonus (clade C) and then housed with susceptible sentinel Rock Soles Lepidopsetta bilineata. Ninety two percent of the orally exposed sculpins and 30% of the sentinel soles were Ichthyophonus-positive at the end of the study, with 0% infected controls. These results demonstrate that a freshwater isolate of Ichthyophonus is infectious and pathogenic to marine species and can be transmitted in seawater in the absence of piscivory. It also provides a plausible mechanism for transmission to small prey fish and planktivores, as well as within a population of piscivores when infected prey is not available.