This paper summarizes the strategies of the San Francisco Bay Area Early Detection Network (BAEDN). BAEDN coordinates and implements Early Detection of and Rapid Response to infestations of target invasive plants throughout the nine county San Francisco Bay Area. Limited-distribution invasive plant species in the Bay Area were identified by analyzing occurrence records within the Calflora database. Target species were then prioritized according to whether or not they were documented as invasive and by expert opinion. Weed Heuristics: the Invasive Population Prioritization for Eradication Tool was used to prioritize the 272 known occurrences of the 73 target priority species based on relative impact, invasiveness, and feasibility of treatment. BAEDN coordinated two years of removal of these populations. Lessons learned and next steps are reviewed. As new populations and species are identified additional funds are needed to carry out coordinated evaluation, prioritization, and control efforts.

The introduced crab, Charybdis japonica, was captured in the Swan River Estuary in Western Australia during October 2012. This constitutes the second documented report of this species in Western Australia after a single specimen was reported in 2010 from a nearby estuary. Given the invasive history of this species in locations such as New Zealand, a rapid-response delimiting survey was conducted to assess the prevalence of this crab within this estuary. A large public engagement campaign was run concurrently with the delimiting survey to inform and enlist the recreational crab fishers that use the Swan River and other nearby estuaries to report any more specimens that they caught. These activities yielded a total of three specimens, all handed in by recreational fishers as a result of the public engagement campaign. All three specimens were caught within a very limited area within the estuary, approximately 8 kilometres from the entrance. The two specimens that were able to be sexed were mature males, with carapace widths of 10.1 and 10.3 mm. The very small number of specimens caught, relative to the abundant native species indicates that C. japonica may be relatively scarce in the Swan River Estuary. This result highlights the importance of engaging members of the public to help detect introduced marine pest species in the early stages of incursions.

The aquarium trade moves thousands of species around the globe, opening the door to unwanted organisms being released into fresh and marine waters, with subsequent adverse ecological and economic impacts. Unlike ballast waters, the commerce of ornamental pets and the aquarium trade have only recently been recognized as major pathways for the introduction of fish, invertebrates and plants, with online commerce in particular being a thriving business. Here, we report the results of the first study on the online aquarium trade in Italy. We examined 54 online aquarium shops and collected data about the animals and plants sold. For each species, information about its native range, reproduction, feeding habits, pathways, impacts, status in Italy and price were gathered, in order to identify previously recorded or potentially invasive species for Italy. Freshwater fish and plants represent the most sold taxa, and mainly come from the Americas. Most animals are omnivorous, and the plants can reproduce through both reproduction modalities (asexual/sexual). Half of the traded plants have already been introduced outside their native range; however, the majority of the species sold have not yet been recorded in the wild in Italy. As expected, a high percentage of the sold species are reportedly introduced due to escape/release for ornamental purposes. Data on their impact is scanty and mainly concerns the already known invasive species and their ecological damage. Although the multilevel impact exerted by invasive species is recognized worldwide, in Italy the average price of invaders is quite low, thus favoring their purchase. In addition, considering the nation’s growing number of aquarists, the probability of releasing potentially invasive species through the online trade is very high: more information, accurately presented information for buyers and stakeholders, and appropriate regulations may change this trade in order to reduce the risk of new invasions.

Effective and economical tools are needed for treating ship ballast to meet new regulatory requirements designed to reduce the introduction of invasive aquatic species from ship traffic. We tested the efficacy of hydroxide stabilization as a ballast disinfection tool in replicated, sequential field trials on board the M/V Ranger III in waters of Lake Superior. Ballast water was introduced into each of four identical 1,320 L stainless steel tanks during a simulated ballasting operation. Two tanks were treated with NaOH to elevate the pH to 11.7 and the remaining two tanks were held as controls without pH alteration. After retention on board for 14–18 h, CO2-rich gas recovered from one of two diesel propulsion engines was sparged into tanks treated with NaOH for 2 h to force conversion of NaOH ultimately to sodium bicarbonate, thereby lowering pH to about 7.1. Prior to gas sparging, the engine exhaust was treated by a unique catalytic converter/wet scrubber process train to remove unwanted combustion byproducts and to provide cooling. The contents of each tank were then drained and filtered through 35-µm mesh plankton nets to collect all zooplankton. The composition and relative survival of zooplankton in each tank were evaluated by microscopy. Zooplankton populations were dominated by rotifers, but copepods and cladocerans were observed. Hydroxide stabilization was 100% effective in killing all zooplankton present at the start of the tests. Our results suggest hydroxide stabilization has potential to be an effective and practical tool to disinfect ship ballast. Further, using CO2 released from the ship engine reduces emissions and the neutralized by product, sodium bicarbonate, can have beneficial impacts on the aquatic environment.

Restricting the spread of invasive quagga and zebra mussels by decontaminating recreational watercraft is an important management practice in Europe and the United States. These mussels impact freshwater ecosystems and leave massive economic costs of restoration for ecological services and human infrastructure for each water body they invade. The authors investigated, at the request of the California Department of Fish and Game, whether decontaminating watercraft by placement into saline waters after coming into contact with freshwater bodies infested with invasive mussels eliminates the risk of spreading the species. Evaluating whether or not this is a viable management practice is critical where zebra and quagga mussel freshwater habitats are directly connected to brackish and saline water bodies, like the Sacramento-San Joaquin River Delta (Delta), California United States of American (USA). In this study, quagga mussels were exposed to water collected from different locations within the Delta, with salinities ranging from 4 parts per thousand (ppt) to 33.4 ppt for up to fifteen days. We observed a mortality gradient correlating to salinity levels. The water with the highest salinity content killed 100% of the quagga mussels within 40 hours. One hundred percent mortality was not observed until 70 hours of exposure for quagga mussels exposed to lower salinity concentrations of 21.3 ppt and 15.3 ppt. However, 99% of mussels exposed to 4.0 ppt salinity brackish water remained alive for the 16 day duration of the study. These results are similar to mussels held in water with low salinity content similar to most freshwaters. In the Delta, salinity fluctuates naturally and travel time by boat between saline and freshwaters is a few hours or less. Therefore, it would be challenging if not impossible for watercraft operators to ensure the proper exposure time and salinity exposure. Based on these results, the authors do not recommend launching boats into salt water or brackish water prior to entry into freshwater as a decontamination option for watercraft or as a management tool for preventing invasive mussel infestations.

Fish passage facilities for reservoir dams have been used to restore habitat connectivity within riverine networks by allowing upstream passage for native species. These facilities may also support the spread of invasive species, an unintended consequence and potential downside of upstream passage structures. We documented dam passage of the invasive virile crayfish, Orconectes virilis (Hagen, 1870), at fish ladders designed for upstream passage of American eels, Anguilla rostrata (Lesueur, 1817), in the Shenandoah River drainage, USA. Ladder use and upstream passage of 11 virile crayfish occurred from 2007–2014 during periods of low river discharge (<30 m³s^–1) and within a wide range of water temperatures from 9.0–28.6 °C. Virile crayfish that used the eel ladders were large adults with a mean carapace length and width of 48.0 mm and 24.1 mm, respectively. Our data demonstrated the use of species-specific fish ladders by a non-target non-native species, which has conservation and management implications for the spread of aquatic invasive species and upstream passage facilities. Specifically, managers should consider implementing long-term monitoring of fish passage facilities with emphasis on detection of invasive species, as well as methods to reduce or eliminate passage of invasive species.

Management of silver carp Hypophthalmichthys molitrix has become a growing concern for multiple state and federal entities. Commercial fishing may have the greatest potential to control silver carp. However, for a management action to be successful, the level of exploitation required to reduce silver carp populations must be quantified. Therefore, silver carp were collected from Midwestern U.S. rivers (i.e., Upper, Middle, and Lower Mississippi, Missouri, Illinois, Ohio, and Wabash rivers) to obtain population dynamics (i.e., recruitment, growth and mortality). Parameters obtained from population demographics were used to simulate exploitation levels using a spawning potential ratio (SPR) approach to determine target size and the amount of exploitation needed to recruitment overfish silver carp within each river system. Overall, we determined that silver carp populations (regardless of river) must be exploited at a small size (i.e., 27–33% of population exploited at ≥300 mm or 33–44% exploited at ≥400 mm), in order to reduce SPR to 0.2, which is identified as a threshold for recruitment overfishing. However, an understanding of the impacts of small mesh sizes on native species and an incentive program for commercial fisherman to promote catch of small fish is needed. This study provides federal and state agencies levels of exploitation and a target size required to effectively reduce silver carp populations in multiple rivers.

The distribution and status of native and non-native crayfish are monitored across hundreds of lakes in Ontario (Canada). However, a corresponding effort has not been undertaken in flowing waters. Reliable and efficient sampling methods are essential for the detection of new aquatic invaders and tracking the spread of existing invasive species. In this study, a recent dataset for the invasive rusty crayfish (Orconectes rusticus) was used to determine whether the detection probability associated with intensive sampling by hand-capture (20 minutes) of 10 transects could be achieved with fewer transects. Results indicate that sampling more than three transects does not improve rusty crayfish detection. Monitoring designs based on three transects would reduce search effort by 140 minutes at each site; permitting greater spatial coverage or more frequent sampling.

Crayfish plague (Aphanomyces astaci) is the main problem that hinders the conservation of European crayfish species. Every year, dozens of native crayfish populations disappear due to this disease. We used an electric fish barrier to block the dispersal of infected crayfish upstream. One of the main objectives of this communication is to transfer our expertise using this equipment for improved conservation outcomes. As a result, we report a detailed description of the experience, as well as requirements, problems and opportunities of using an electric fish barrier to try to control crayfish plague in-situ.

Non-native Pterygoplichthys (Loricariidae) are increasingly introduced and established in tropical and subtropical regions worldwide. Florida (USA) has a long history of introduction of loricariid catfishes. These catfishes are of management concern, particularly when they occupy sensitive habitats such as springs and spring runs. Limiting introduction and spread is important because springs are among the most imperiled aquatic habitats in Florida and serve as thermal refuges in winter for Pterygoplichthys. Herein we report the only known eradication of an introduced loricariid catfish by direct human intervention and the only eradication of a non-native fish in Florida by means other than the fish toxicant rotenone. Vermiculated sailfin catfish (Pterygoplichthys disjunctivus) was first observed in the Rainbow River, Marion County, Florida in December 2002 but disappeared by March 2003. Occurrence was documented again in April 2006. Monthly surveys and removals were done and 28 individuals were removed from 2006 through 2008 by hand and fish spear. No additional individuals have been found since June 2008 and quarterly monitoring continues. Factors that facilitated the removal efforts included the springs’ protected status as a Florida Aquatic Preserve, on-going monitoring and control programs for invasive aquatic macrophytes, high water clarity, small numbers and spatial extent of observed Pterygoplichthys, relative isolation from other source populations, and little evidence of reproduction and recruitment. Decisions to undertake eradication or control programs for non-native fishes require consideration of the vulnerability of the site, spatial scale, habitat, interconnectivity with source populations, impacts of the non-native in the absence of management intervention, and available resources.