Rodman G. Getchell

Applied research by an international team was conducted on freshwater intensive recirculating aquaculture systems (RAS) at a remote desert research station in the Kingdom of Saudi Arabia. RAS biotechnical and engineering parameters for newly imported rainbow trout (Oncorhynchus mykiss) and a local variety of common carp (Cyprinus carpio) were used to predict that after 52 weeks rainbow trout with regular sorting would reach a final standing crop biomass of 50 kg/m3 for fish stocked at an average of 7.8 kg/m3 ; would be 25 kg/m3 for fish stocked at 5.0 kg/m3; and that trout would average ~860 g at both stocking densities. After 293 days, rainbow trout at the higher density averaged 835 g (range 820-843 g) at a biomass of 48.1 kg/m3, and for the lower density 864 g (850-872 g) at a biomass of 24.9 kg/m3. Crude food conversion ratios (FCRs) were below 1.0 over the last 122 days of the culture period. Sorting fish to accomplish new stocking densities meant that many healthy, juvenile trout were moved out of the RAS at each stage which were sent to stock the first pilot trout farms in the country. RAS for common carp had low water quality caused by poor solids removal during the last part of the culture period. Despite this, fish stocked at higher density (3.1 kg/m3) produced at harvest a biomass of 26.6 kg/m3 of fish averaging 682.4 g, and fish stocked at a lower density (1.5 kg/m3) produced 29.1 kg/m3 of fish averaging 857.1 g. Mortalities were low. Results were used for training and learning in challenges and opportunities of establishing RAS in remote desert areas. Based upon encouraging results a 10,000 m2 Aquaculture Centre of Excellence featuring a modern RAS combining advanced cooling systems, hatchery, growout, and aquaponics has been built in the KSA.

Objective: We investigated viral hemorrhagic septicemia virus dynamics in wild fish populations of the St. Lawrence River to compare host competency among five abundant native species and the invasive Round Goby Neogobius melanostomus following two decades of host–pathogen coevolution. To examine species’ responses to the virus and identify principal hosts as viral reservoir species, we used viral surveillance among Round Gobies, Yellow Perch Perca flavescens, Rock Bass Ambloplites rupestris, Pumpkinseed Lepomis gibbosus, Bluegill L. macrochirus, and Brown Bullhead Ameiurus nebulosus collected from the nearshore fish community in the upper St. Lawrence River during spring 2020–2021. Methods: Reverse-transcription quantitative PCR was used to detect and quantify viral nucleoprotein gene genetic material in pooled organ (i.e., liver, kidney, and spleen) and brain tissues of wild fish belonging to several susceptible host species. Results: Reverse-transcription quantitative PCR detected viral hemorrhagic septicemia virus genetic material in each species during both sampling years. There was significant variation between species in both infection prevalence and median viral titer. Invasive Round Gobies exhibited significantly higher prevalence and titers compared to any of the native species. However, some native fishes (e.g., Yellow Perch and sunfishes Lepomis spp.) presented higher infection prevalence and viral concentrations compared to the others (e.g., Rock Bass and Brown Bullhead). Conclusions: Multiple species remain susceptible to viral hemorrhagic septicemia virus under enzootic conditions; however, viral infections are distributed unevenly among host species. Invasive Round Gobies have amplified reservoir competence compared to native fish species.

The cage aquaculture industry in Lake Victoria, Kenya is growing explosively to meet increasing demand for fish, yet large‐scale fish mortalities are prevalent and pose economic shocks with catastrophic livelihood impacts. To gain a more comprehensive understanding of fish health in Lake Victoria, our study applied: (1) survey of cage farmer accounts, perceptions and responses to fish kill events; (2) rapid‐response investigation to a significant tilapia mortality event; (3) active disease surveillance; and (4) antimicrobial resistance (AMR) testing of bacterial pathogens via disk diffusion. There were 82 fish kills recalled from 2020 to 2023 with total mortalities exceeding 1.8 million tilapia; yet, only 39% of farmers reported to Kenyan institutions and 17% of farmers attempted medical treatment. Low dissolved oxygen (DO) levels and the isolation of Aeromonas jandaei , Enterobacter hormaechei and Staphylococcus epidermidis were implicated as suspected causes for a recent tilapia mortality event. Active disease surveillance detected trichodinids and monogeneans as common external parasites and identified an additional six bacterial species in tilapia ( Acinetobacter soli , Bacillus cereus , Kocuria rhizophila , Micrococcus luteus , Plesiomonas shigelloides , Staphylococcus sciuri ) previously published as fish pathogens. Furthermore, we identify AMR patterns that will support the development of host‐ and pathogen‐specific thresholds.

Chronic viral infections, such as HIV and hepatitis C virus, represent a major public health problem. Although it is well understood that neonates and adults respond differently to chronic viral infections, the underlying mechanisms remain unknown. In this study, we transferred neonatal and adult CD8+ T cells into a mouse model of chronic infection (lymphocytic choriomeningitis virus clone 13) and dissected out the key cell-intrinsic differences that alter their ability to protect the host. Interestingly, we found that neonatal CD8+ T cells preferentially became effector cells early in chronic infection compared with adult CD8+ T cells and expressed higher levels of genes associated with cell migration and effector cell differentiation. During the chronic phase of infection, the neonatal cells retained more immune functionality and expressed lower levels of surface markers and genes related to exhaustion. Because the neonatal cells protect from viral replication early in chronic infection, the altered differentiation trajectories of neonatal and adult CD8+ T cells is functionally significant. Together, our work demonstrates how cell-intrinsic differences between neonatal and adult CD8+ T cells influence key cell fate decisions during chronic infection.

Atlantic menhaden are a highly migratory marine species in the Eastern United States that suffer from seasonal chronic mortality. Affected fish show neurologic signs referred to as spinning disease, including circling at the surface and erratic corkscrew swimming before death. We investigated three similar menhaden mortality events consistent with spinning disease in coastal New Jersey and New York between 2020 and 2021 to understand the cause. A unique strain of Vibrio (Listonella) anguillarum (serogroup O3) was detected regularly in high loads, particularly in the brains of moribund fish, by both metagenomics and bacterial isolation. The most common histopathological changes in moribund fish were hemorrhagic meningitis, encephalitis, pyknosis, and karyorrhexis of hematopoietic tissues in the kidney and spleen. Whole genome sequencing of isolates from moribund fish representing a wide spatial and temporal range showed that they were nearly identical clones, suggesting it to be a pathogenic strain circulating in the population. Though V. anguillarum is believed to be the main pathogen associated with spinning disease and mortality, Yersinia ruckeri (serotype O1) was isolated from smaller numbers of fish. Considering the highly migratory nature of Atlantic menhaden throughout the eastern United States and their use as bait for other fisheries, these findings identify potential biosecurity challenges that should be considered in Atlantic salmon aquaculture, fisheries, and emerging marine aquaculture in the region.

Getchell RG, George E, Rice AN, Malatos JM, Chambers BM, Griefen A, Nieder C, Rustam LG. 2022. Effects of ultrasonic control devises on fish. Lake Reserv Manage. XX:XX–XX. Harmful algal blooms (HABs) can have serious impacts on both ecosystem services and human health, and several mitigation techniques have been developed to control them. Ultrasonic sound sources can disrupt developing algal mats, causing concern that the acoustic energy emitted from these devices may have deleterious health or behavioral effects on nearby fishes. We conducted field and laboratory studies on the effects of ultrasonic control devices on resident fishes. Field observations in Oneida Lake, New York, of the behavioral response of fish to the ultrasonic sound were conducted in shallow water using line transects, and in deeper water using hydroacoustics. No avoidance behavior was detected in either shallow or deep water while the ultrasonic devices were operating. Under controlled laboratory conditions, 7 recreationally or ecologically important fish species and local wild tadpoles were exposed to sound produced by the ultrasonic control devices for a 2 week period. No behavioral effects were noted while fish and tadpoles were monitored during the exposure interval. Finally, no significant or harmful histological or morphological alterations to the skin, fins, gills, or internal organs were observed on either fish or tadpoles when specimens were examined after the 2 week exposure period.

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.

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.