Influence of water-level variability on fish assemblage and natural reproduction following connectivity enhancement in a Typha-dominated coastal wetland, USA.

We evaluated a wetland habitat modification strategy to contrast fish assemblage structure and the production of young-of-the-year (YOY) fish between different engineered habitats (i.e., spawning pool complexes and connectivity channels) relative to unmodified lateral channels in a large drowned river mouth tributary of the St Lawrence River. Prior to habitat modifications, the coastal wetland was impaired by water level regulations and dominance of the invasive hybrid cattail, Typha × glauca, which collectively replaced or created barriers to seasonally flooded spawning habitats important to fish. Connectivity enhancements provided fish access along a wetland habitat gradient from sedge-meadows to the deeper water robust emergent main channel. Across an 8-year fish emigration dataset (2012, 2013, 2016-2021) more than 90% of all captured fish (Ntotal = 218,086 fish) were YOY and modified habitats outperformed the unmodified channels in total fish catch-per-unit-effort (CPUE) per year (both YOY and non-YOY). Spawning pool complexes had higher YOY species richness than unmodified channel habitats. Fish assemblage structure differed between the modified habitats, where connectivity channels and unmodified channels shared a more similar fish assemblage than spawning pool complexes. Modified habitats, however, supported warmer water and higher dissolved oxygen than the unmodified channels. Redundancy analysis and linear mixed-effect modelling with abiotic variables (hydrology, temperature and dissolved oxygen) showed significant effects on fish assemblage structure, species richness and CPUE of fish emigrating from the modified and unmodified habitats. Historic flooding in 2017 and 2019 was a primary driver of YOY fish production and fish assemblage structure, but also appeared to be associated with near anoxic conditions systemwide. YOY fish for several species was inversely affected by floods at spawning pool complexes, but CPUE of YOY fish for these species appeared unaffected at the connectivity channels despite low dissolved oxygen. Diversified habitat structure (i.e., connectivity channels and spawning pool complexes) offers a management option to enhance habitat for fish that allowed compensatory effects on the capture of YOY fish of several species during floods. This multifaceted outcome from the habitat modifications resulted in unique fish assemblages between the channelized and spawning pool habitat. A connectivity-based habitat enhancement strategy provides adaptability for an uncertain climatic and regulatory future for the Laurentian Great Lakes and St Lawrence River.

Use of next generation sequencing to compare simple habitat and species level differences in the gut microbiota of an invasive and native freshwater fish species.

Research on the gut microbiome of host organisms has rapidly advanced with next generation sequencing (NGS) and high-performance computing capabilities. Nonetheless, gut microbiome research has focused on mammalian organisms in laboratory settings, and investigations pertaining to wild fish gut microbiota remain in their infancy. We applied a procedure (available at https://github.com/bngallo1994) for sampling of the fish gut for use in NGS to describe microbial community structure. Our approach allowed for high bacterial OTU diversity coverage (>99.7%, Good's Coverage) that led to detection of differences in gut microbiota of an invasive (Round Goby) and native (Yellow Bullhead) fish species and collected from the upper St. Lawrence River, an environment where the gut microbiota of fish had not previously been tested. Additionally, results revealed habitat level differences in gut microbiota using two distance metrics (Unifrac, Bray-Curtis) between nearshore littoral and offshore profundal collections of Round Goby. Species and habitat level differences in intestinal microbiota may be of importance in understanding individual and species variation and its importance in regulating fish health and physiology.

Combining population genomics and forward simulations to investigate stocking impacts: A case study of Muskellunge (Esox masquinongy) from the St. Lawrence River basin.

Understanding the genetic and evolutionary impacts of stocking on wild fish populations has long been of interest as negative consequences such as reduced fitness and loss of genetic diversity are commonly reported outcomes. In an attempt to sustain a fishery, managers implemented nearly five decades of extensive stocking of over a million Muskellunge (Esox masquinongy), a native species in the Lower St. Lawrence River (Québec, Canada). We investigated the effect of this stocking on population genetic structure and allelic diversity in the St. Lawrence River in addition to tributaries and several stocked inland lakes. Using genotype by sequencing, we genotyped 643 individuals representing 22 locations and combined this information with forward simulations to investigate the genetic consequences of long-term stocking. Individuals native to the St. Lawrence watershed were genetically differentiated from stocking sources and tributaries, and inland lakes were naturally differentiated from the main river. Empirical data and simulations within the St. Lawrence River revealed weak stocking effects on admixture patterns. Our data suggest that the genetic structure associated with stocked fish was diluted into its relatively large effective population size. This interpretation is also consistent with a hypothesis that selection against introgression was in operation and relatively efficient within the large St. Lawrence River system. In contrast, smaller populations from adjacent tributaries and lakes displayed greater stocking-related admixture that resulted in comparatively higher heterozygosity than the St. Lawrence. Finally, individuals from inland lakes that were established by stocking maintained a close affinity with their source populations. This study illustrated a benefit of combining extensive genomic data with forward simulations for improved inference regarding population-level genetic effects of long-term stocking, and its relevance for fishery management decision making.

Investigation of round goby viral haemorrhagic septicaemia outbreak in New York.

Eleven viral haemorrhagic septicaemia virus (VHSV) genotype IVb isolates were sequenced, and their genetic variation explored to determine the source of a VHS outbreak on the eastern shore of Cayuga Lake. An active fish kill of round gobies (Neogobius melanostomus, Pallas) was intensively sampled at King Ferry, NY and nearby Long Point State Park in May 2017. Gross lesions observed on 67 moribund round gobies and two rock bass (Ambloplites rupestris, Rafinesque) included moderately haemorrhagic internal organs and erythematous areas on the head, flank, and fins. RT-qPCR tests for VHSV were positive for all 69 fish. Viral isolation on epithelioma papulosum cyprinid cells showed cytopathic effect characteristic of VHSV for six round goby samples from King Ferry. The complete nucleotide sequence of the VHSV IVb genomes of five Cayuga Lake round goby isolates were derived on an Illumina platform along with 2017 VHSV IVb isolates from round gobies collected from the following: Lake Erie near Dunkirk, NY; the St. Lawrence River near Clayton and Cape Vincent, NY; and Lake St. Lawrence near Massena, NY. The phylogenetic tree created from these aligned sequences and four other complete VHSV IVb genomes shows Cayuga Lake isolates are closely related to the Lake Erie isolates.

Complete sequences of 4 viral hemorrhagic septicemia virus IVb isolates and their virulence in northern pike fry.

Four viral hemorrhagic septicemia virus (VHSV) genotype IVb isolates were sequenced, their genetic variation explored, and comparative virulence assayed with experimental infections of northern pike Esox lucius fry. In addition to the type strain MI03, the complete 11183 bp genome of the first round goby Neogobius melanostomus isolate from the St. Lawrence River, and the 2013 and 2014 isolates from gizzard shad Dorosoma cepedianum die-offs in Irondequoit Bay, Lake Ontario and Dunkirk Harbor, Lake Erie were all deep sequenced on an Illumina platform. Mutations documented in the 11 yr since the MI03 index case from Lake St. Clair muskellunge Esox masquinongy showed 87 polymorphisms among the 4 isolates. Twenty-six mutations were non-synonymous and located at 18 different positions within the matrix protein, glycoprotein, non-virion protein, and RNA polymerase genes. The same 4 isolates were used to infect northern pike fry by a single 1 h bath exposure. Cumulative percent mortality varied from 42.5 to 62.5%. VHSV was detected in 57% (41/72) of the survivors at the end of the 21-d trial, suggesting that the virus was not rapidly cleared. Lesions were observed in many of the moribund and dead northern pike, such as hemorrhaging in the skin and fins, as well as hydrocephalus. Mean viral load measured from the trunk and visceral tissues of MI03-infected pike was significantly higher than the quantities detected in fish infected with the most recent isolates of genotype IVb, but there were no differences in cumulative mortality observed.

Low concentrations of contaminants in an invasive cyprinid, the rudd, in a Great Lakes Area of Concern.

The invasive, omnivorous rudd Scardinius erythrophthalmus is abundant in the upper Niagara River, a Great Lakes Area of Concern. Invasive species can alter trophic and contaminant pathways, but complex ontogenetic and seasonal diet shifts by rudds make it difficult to predict their chemical burdens relative to other fishes. We quantified concentrations of chemical residues in rudds and compared them to six fish species from various trophic levels. Rudds contained low concentrations of total dichlorodiphenyltrichloroethane (mean = 0.02 µg/g), Hg (mean = 0.03 µg/g), and polychlorinated biphenyls (mean = 0.06 µg/g); these concentrations were among the lowest for all species examined. Concentrations of aldrin, heptachlor, hexachlorobenzene, total hexachlorocyclohexanes, mirex, and total chlordanes were less than the method detection limit for all rudds examined. If reducing rudd biomass is determined to be beneficial, resource managers could consider targeted harvest, given the low concentrations of contaminant in rudds and their susceptibility to capture.

Reform requires resilience: a holistic model for success.

Ten initiatives associated with healthcare reform may alter the way healthcare organizations operate. Implementing a governance, risk, and compliance (GRC) model can help healthcare leaders deliver performance and compliance and enable enterprise resilience. Implementing GRC effectively requires a vision that's clearly supported by the management team.