Using dissolved carbon dioxide to alter the behavior of invasive round goby

Abstract

Experimental studies evaluating the effects of food availability on the movement of free-ranging animals generally involve food supplementation rather than suppression. Both approaches can yield similar insights, but we were interested in the potential for using food suppression for the management and control of invasive predators, in particular, the brown treesnake (Boiga irregularis) on Guam. However, understanding a species' response to food resources is critical before employing such a strategy. We studied the movements of 24 radio-tagged B. irregularis initially caught within four 4-ha unfenced plots in rodent-abundant (control) and rodent-suppressed (treatment) grassland habitats over a 40-day period. Because monitoring duration differed among snakes, we also analyzed short-term (16-day) activity areas. Over the 16 days, snakes associated with rodent-suppressed plots had 86% larger activity areas (ha), 94% greater dispersal distances (m), and 43% greater movement rates (m/h) than snakes associated with control plots. Boiga irregularis moved extensively, but these movements were not always reflected in the size of the snake's total activity area. Movement rates did not differ between sexes, but snakes in above-average body condition moved greater distances per hour than those in below-average condition irrespective of treatment. Our study indicates that a relatively small prey suppression effort can cause almost immediate and significant changes in B. irregularis movement. On Guam, prey suppression might enhance control efforts by either increasing trap capture success or discouraging snakes from entering areas of conservation or management concern. However, the outcome of using prey suppression as a control tool in areas threatened with the accidental introduction of the brown treesnake is more difficult to predict and might have negative consequences such as elevated dispersal rates.

Assessment of Carbon Dioxide Piscicide Treatments

“…; Cupp et al. , ). One potential strategy to mitigate treatment avoidance would be to rapidly elevate CO 2 levels to the point where fish lose equilibrium and become heavily sedated.…”

“…For example, invasive Round Goby Neogobius melanostomus were observed losing equilibrium within minutes when exposed to >150 mg/L CO 2 (Cupp et al. ). Rapid influx of CO 2 across the blood–brain barrier results in a narcotic state where fish would be unable to physically relocate away from CO 2 piscicide treatments, and prolonged lethal exposure is imminent (Yoshikawa et al.…”

Toxicity of Carbon Dioxide to Freshwater Fishes: Implications for Aquatic Invasive Species Management

“…Progression through the strongest planes of anesthesia ultimately resulted in mortality for individuals at the highest concentrations (Figures 2 and 4, Tables 3 and 4). Fortunately, the exposure risk in management applications may be moderated by animal behavior because several studies have demonstrated that fish can sense and avoid areas with elevated CO 2 before the onset of severe physiological impairment (Donaldson et al 2016; Cupp et al 2017a, 2017b). Unlike animals in a natural environment, fish in the present study were confined within test tanks and did not have an opportunity to avoid CO 2 exposure Behavioral avoidance is an advantageous behavioral response for CO 2 as an invasive species deterrent barrier but could present challenges when administering CO 2 for lethal purposes because fish may avoid LCs if the treatment is not uniformly delivered.…”

Influence of Nutritional Status on Carbon Dioxide Tolerance and Avoidance Behavior in a Freshwater Teleost

“…), and Round Goby Neogobius melanostomus (Cupp et al. ). When deployed, CO 2 barriers could influence fish movements via two primary mechanisms.…”

“…; Cupp et al. ), allowing zones of CO 2 to (1) deter passage through a choke point as fish “choose” to swim to water with improved quality or (2) deflect organisms to a target area to facilitate harvest. Second, due to the anesthetic properties of CO 2 , if fish are forced to spend extended periods of time in elevated‐CO 2 zones—for example, if CO 2 is deployed in a confined space, such as a shipping lock—animals can lose equilibrium, and movement can be prevented.…”