Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—The nonnative Northern Snakehead <em>Channa argus </em>was first documented in the Potomac River system in 2004. Since then, their range in Virginia has expanded to include other rivers and numerous lakes as a result of dispersal and illegal introductions. Most Northern Snakehead lake populations were discovered after 2012. Through 2017, nearly 4,000 Northern Snakehead were collected via Virginia Department of Game and Inland Fisheries (VDGIF) electrofishing surveys, resulting in a robust dataset. These collections provided an opportunity to investigate food habits of Northern Snakehead in both lotic and lentic systems which may assist with management and a better understanding of potential community effects. Incidence of identifiable prey items (<em>n </em>= 677) was evaluated since 2004, however wet weights (<em>n </em>= 370) were not recorded until 2014. A total of 30 prey types were identified from Northern Snakehead stomachs taken from rivers, whereas 7 prey types were identified from lakes. Banded Killifish, Bluegill, and crayfish were the most abundant prey types (in order) based on frequency of occurrence for Northern Snakehead collected from rivers; whereas Bluegill, frogs, and Yellow Perch were most common in Northern Snakehead collected from lakes. Most important food types (in order) based on % wet weight for Northern Snakehead collected from rivers were Bluegill, Gizzard Shad, and Banded Killifish; whereas Bluegill, Yellow Perch, and frogs contributed the most mass for Northern Snakehead from lakes.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Understanding the diel activity of a species can shed light on potential interactions with other species and inform management practices. To understand the diel activity of Northern Snakehead <em>Channa argus</em>, feeding habits and movement patterns were observed. Two hundred seventy-three Northern Snakehead were captured by boat electrofishing during May and June of 2007 and 2008. Their gut contents were extracted and preserved. The level of digestion of each prey item was estimated from fresh (1) to >50% digested (4) or empty (5). Random forest models were used to predict feeding activity based on time of day, tide level, date, water temperature, fish total length, and sex. Diel movement patterns were assessed by implanting Northern Snakehead with radio transmitters and monitoring them every 1.5 h for 24 h in both March and July 2007. Movement rates were compared between March and July and among four daily time periods. Independent variables accounted for only 6% of the variation in feeding activity; however, temporal feeding patterns were apparent. No fresh items were observed in guts between 12:30 and 7:30 am, and the proportion of empty stomachs increased at the end of May coinciding with the onset of spawning. Overall, fish moved greater distances during the July tracking period compared to March. Fish showed a greater propensity to move during daylight hours than at night during the March tracking period. A similar but nonsignificant (<EM>P </EM>> 0.05) pattern was observed in July. Movement and feeding data both indicated greater activity during daylight hours than at night, suggesting that Northern Snakehead is a diurnal species. Based on our preliminary findings, we hypothesize that a) diurnal species are more susceptible than nocturnal species to predation by Northern Snakehead and b) Northern Snakehead are more likely to compete for food with diurnal than nocturnal predators.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—In Japan, natural populations of three snakeheads have been established: Northern Snakehead <em>Channa argus</em>, Blotched Snakehead <em>C. maculata</em>, and Small Snakehead <em>C. asiatica</em>. Historical literature indicates that <em>C. argus </em>was brought into Japan during the period of national isolation in the early modern period. After the nation’s closure period, the former two species were introduced before World War II for food resources, whereas the last was found in Japan after the war. <em>Channa argus </em>was cultured in irrigation ponds in some prefectures, but ecological invasiveness was a concern because of their predatory nature and nonindigenous origins. When new national legislation controlling invasive alien species began in 2005, three snakeheads appeared on the list of alien species requiring special attention. However, there is little evidence suggesting ecological invasiveness of snakeheads in Japan in recent years. The most recent national list of invasive species in 2016 included no snakeheads. In some water bodies, <em>C. argus </em>is actively used as the ecological agent to control other invasive alien species.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Northern Snakeheads <em>Channa argus </em>were imported by fish farmers in Arkansas for use and sale in live food markets before being banned by the state in July 2002. Farmers were advised to destroy their stock in 2002 when importation and interstate trade were federally banned under the Lacey Act (18 U.S.C § 42(a) (1)). These farmers reportedly attempted this action, but on April 14, 2008; a wild Northern Snakehead, confirmed by the Arkansas Game and Fish Commission, was captured by a local row crop farmer. An eradication plan was formulated for Fall 2008 involving several government agencies and universities. Arkansas experienced several late summer storms resulting in flood conditions during that time. The eradication effort, named Operation Mongoose, was rescheduled for March, 2009. Operation Mongoose involved the application of the fish toxicant rotenone using helicopters, Marsh Masters, boats, and ground teams to cover approximately 700 km of creeks, ditches, and backwater areas within the 20,250 ha Piney Creek watershed. The effort reduced the Northern Snakehead population in the drainage but did not eradicate them. Because this area is prone to annual flooding, range expansion of Northern Snakehead occurred. The Arkansas Game and Fish Commission tracks Northern Snakehead dispersal through reporting from the angling public. During 2017, the first confirmed range expansion outside of Arkansas occurred in Mississippi.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Northern Snakehead <em>Channa argus</em>, a species native to parts of Asia, became established in the Potomac River drainage prior to 2004. Removals by agencies appeared to do little to control abundance or limit spread into new waterways. As such, Northern Snakehead has become widespread throughout much of the Potomac River drainage in addition to many other river systems throughout the Chesapeake Bay watershed. As abundance increased within the Potomac watershed, new recreational and commercial fisheries were developed by encouragement of state and federal agencies to increase harvest. A mark–recapture program to examine growth and movement of Northern Snakehead began in 2009, as population density appeared to be increasing. In 2013, tagging methods changed to allow population size of Northern Snakehead to be estimated within selected tributaries (Little Hunting Creek (LHC) and Upper Anacostia River (UA)). From 2009–2017 we used mark–recapture angler returns and agency sampling data to view population size in context with changes in fishing mortality. The UA population linearly declined with increasing fishing mortality, while the LHC population changed very little in response to fishing mortality except for 2016 which had the lowest population estimate and highest fishing mortality. We are cautiously optimistic that exploitation may help control population growth, but recreational fishing alone is unlikely to cause significant declines in Northern Snakehead populations. Furthermore, well-established populations are likely to require high (>25%) exploitation rates to be effective.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Northern Snakehead <em>Channa argus </em>weighing 188.54 ± 13.80 g were fed live Oriental Weatherfish <em>Misgurnus anguillicaudatus </em>at five rations (starvation, 1, 2, 4% body weight per day, and satiation) at 28°C under laboratory conditions to determine its growth and energy budget in relation to ration. The specific growth rate increased linearly with increasing ration and food conversion efficiencies also tended to increase with increasing ration. The proportion of food energy lost in fecal production remained unchanged, but the proportion of food energy lost in nitrogenous excretion tended to decrease with increasing ration, while growth increased. The energy budget at satiation was: 100C = 7.01F + 4.76U + 40.13R + 48.10G, where C, F, U, R and G represent food energy, fecal energy, excretory energy, metabolism energy, and growth energy, respectively. The unbalanced error rates in the energy budget (<EM>C</EM>%) were –9.99–11.94%. Northern Snakehead fed to satiation allocated 45.5% of assimilated energy to metabolism and 54.5% to growth. Northern Snakehead has a high growth efficiency and a low metabolic expenditure, indicating both aquaculture potential and strong competitive ability for successful invasion.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—The U.S. Congress directed the U.S. Fish and Wildlife Service (USFWS) to identify, contain, and eradicate Northern Snakehead <em>Channa argus </em>in the United States. Later, the Mississippi River Basin Panel on Aquatic Nuisance Species requested that the Aquatic Nuisance Species Task Force develop a management plan to include additional snakehead species (Channidae) that are, or have the potential to become, invasive in United States waters. Objectives of the snakehead management and control plan, which was developed by USFWS and collaborators, include developing long-term adaptive management and control methods. We developed a Ricker stock-recruit model using Northern Snakehead population data collected in four northern Virginia tidal tributaries during 2009–2015 to inform management and control efforts. The resulting model functional relationship explained 93% of recruitment variability using adult stock size (mean electrofishing catch/h [CPUE] of adults) and mean river flow during May. Recruitment was quantified using boat electrofishing CPUE of age-2 fish lagged for two years, because age-0 and even age-1 fish did not appear to be fully recruited to the gear. Seventy-six percent of recruitment variation was explained by adult abundance, while an additional 17% was explained by mean river flow during May (inverse relationship). Model predictions indicated management efforts to reduce adult stock size, from the optimum of 2–4 fish/h to <0.5 fish/h, should be the most effective tool to reduce recruitment and resulting adult abundance over the long term. That level of adult abundance (approximately 12% of the mean during 2009–2015) should be the target maximum for Northern Snakehead control efforts in the study areas.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Although the origin, distribution, abundance, and spread of the Northern Snakehead <em>Channa argus </em>in the Potomac River have been studied, management and control plans for other invasive species are increasingly contested in social arenas where stakeholder values differ. Yet few investigations focus on social or ethical dimensions of the Northern Snakehead. Management actions for Northern Snakehead are currently limited to regulating possession, educating anglers, and encouraging harvest. In this paper, I examine ethical questions to guide future decisions and argue for ethical pragmatism and participatory management, which recognize stakeholder values, aim to reduce defensiveness, increases listening, and consciously cultivates a ground of mutual respect and trust among stakeholders, scientists, and managers.

Proceedings of the First International Snakehead Symposium

<em>Abstract.</em>—Relative weight and size structure indices are useful tools for fish biologists to characterize fish condition and fish size structure. However, a standard-weight (<em>W_s</em>) and size structure indices do not currently exist for Northern Snakehead <em>Channa argus</em>. We complied length-weight data from 4 established populations of Northern Snakehead in North America across five states and four drainages. We used the regression-line-percentile (RLP) method to develop a standard-weight equation for Northern Snakehead. The RLP method uses the 75th percentile as a benchmark for standard weight. Based this approach, we propose a metric standard-weight equation as log₁₀(<em>W_s</em>) = –5.142 + 3.0418 * log₁₀ (TL) with a minimum length of 200 mm; <em>W_s </em>is weight in grams and TL is total length in millimeters. For calculating proportional size distribution (PSD) we proposed the following length categories: stock, 190mm (7.5 in); quality, 340 mm (13 in); preferred, 420 mm (16.5 in); memorable, 550 mm (22 in); and trophy, 700mm (27.5 in). The population level indices developed in this study will provide fish biologists another set of tools to describe invasive Northern Snakehead populations in North America.