The pet and horticultural trades as introduction and dispersal agents of non-indigenous freshwater molluscs

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.

Turning Negatives into Positives for Pet Trading and Keeping: A Review of Positive Lists

“…The theoretical and practical benefits of positive lists for pet trading and keeping were acknowledged by civil servants during the interviews. There is support from within the academic community for positive lists as a means of aiding species conservation and protecting biodiversity [ 12 , 32 , 175 , 176 , 177 , 178 ], and from within the veterinary community for safeguarding animal welfare and preventing zoonoses and other infections [ 179 , 180 , 181 , 182 ].…”

Non‐native freshwater snails: a global synthesis of invasion status, mechanisms of introduction, and interactions with natural enemies

“…Global trade in pets and ornamental organisms has increased greatly in recent decades and has been directly linked to species invasions by numerous taxa (Lockwood et al., 2019; Padilla & Williams, 2004). Previous studies have surveyed the diversity of freshwater snail taxa offered in the aquarium trade and noted the high likelihood of the aquarium hobby as a primary vector for new aquatic snail invasions (Cowie & Robinson, 2003; Duggan, 2010; Mackie, 1999; Ng et al., 2016; Patoka et al., 2017; Yanai et al., 2017). The ease at which live aquatic animals can now be purchased online has exacerbated this trend (Olden et al., 2020).…”

“…The mechanisms were grouped into the following seven categories: (1) transport and sale associated with the freshwater aquarium hobby; (2) “hitchhiking” with ornamental aquatic vegetation, often associated with outdoor water‐gardens; (3) introductions associated with human consumption of snails, including aquaculture and field collection; (4) snails introduced as biological control agents; (5) introductions stemming from canals that connected previously isolated waterbodies; (6) transport associated with commercial shipping; and (7) movement associated with outdoor recreational activities. Because the aquarium hobby has been implicated as an important driver of non‐native snail introductions, we also quantified how many taxa from our non‐native snail list were reported from aquarium store surveys that were conducted in several different continents (Cowie & Robinson, 2003; Duggan, 2010; Mackie, 1999; Ng et al., 2016; Patoka et al., 2017; Yanai et al., 2017). Table S2 includes information on the mechanisms of introduction from both the original literature search and the aquarium store surveys.…”

“…Because the aquarium hobby has been implicated as an important driver of non-native snail introductions, we also quantified how many taxa from our non-native snail list were reported from aquarium store surveys that were conducted in several different continents (Cowie & Robinson, 2003;Duggan, 2010;Mackie, 1999;Ng et al, 2016;Patoka et al, 2017;Yanai et al, 2017). Table S2 includes information on the mechanisms of introduction from both the original literature search and the aquarium store surveys.…”

Invasive aquatic pets: failed policies increase risks of harmful invasions

“…Since November 1993, everybody in Switzerland needs a concession for releasing non-native fish and crayfish in natural and artificial water-bodies (public and privately owned), and strict legislation, however, does not prevent crime (Pöckl 1999). And in Israel, the Israeli law (National Parks and Nature Reserves Act 1998) protects all freshwater molluscs, nonnatives included such as the aquarium species giant ramshorn snail (Marisa cornuarietis), assassin snail (Anentome helena), acute bladder snail (Physella acuta) and the golden apple snail (Pomacea diffusa) (Yanai et al 2017).…”