Published in June 2022
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Research articles
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Mickael Teixeira Alves and Hannah J. Tidbury
Invasive non-native species management under climatic and anthropogenic pressure: application of a modelling framework (pp 259–273) |
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Mitigation of impacts from already established invasive non-native species (INNS) relies on reducing species abundance and onward spread. However, there is limited understanding
regarding the effectiveness of INNS management approaches in the short and long term, in particular in the marine environment. Further, the interplay between management and key
population drivers is not well explored. The Pacific oyster Crassostrea gigas Thunberg, 1793, also known as Magallana gigas Thunberg, 1793, is native to the north-eastern
Pacific coast of Asia and has been introduced in the UK for aquaculture purposes, with wild populations now widely established along the South coast. Concern over the potential impact
of this species has led to trial of its management, yet clear evidence to support management decisions around this species is still lacking. This study applied a modelling framework,
based on differential equations representing C. gigas life stages, to explore the effect of adult oyster population management on population persistence and density, under
changing temperatures and external larval recruitment. The outputs highlight that population control may be possible and intuitively population density is negatively correlated
with management frequency and effort. However, the exact relationship between population density and management is influenced by spawning and external recruitment. Specifically,
outputs indicate that while the effects of climate change could be counterbalanced by an increase in management effort, the impact of external recruitment can only be reduced
through management, rather than reversed. The wider application of this framework to inform INNS management decisions is discussed.
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Jun-jie Zhang, Ming-ling Cai, Li-hua Chen, Xiao-hua Lin, Jin-di Peng, Jun-dong Huang, Ling Shao and Chang-lian Peng
Photosynthetic physiological and ecological responses of the invasive Sphagneticola trilobata and the native Sphagneticola calendulacea to experimental shading (pp 274–287) |
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Affected by global climate change and human activities, biological invasion has become a serious global problem that not only occurs in cities and wastelands
but also in forests, severely endangering biodiversity. Sphagneticola trilobata (L.) Pruski, 1996, is a common invasive plant in South China that can adapt
to high light and high temperature environments, but its photosynthetic physiological response to shaded environments, such as forest margins, remains unclear.
This study investigates the photosynthetic physiology and oxidative damage of S. trilobata and the native species Sphagneticola calendulacea (L.) Pruski, 1996,
in a low-irradiance environment. The results show that, compared with the full-light group, photosynthetic gas exchange parameters (including net photosynthetic rate,
stomatal conductance and transpiration rate) and chlorophyll fluorescence parameters (maximal quantum yield and actual quantum yield of PSII) of plants in the low-light
group significantly decreased after shading, while intercellular CO2 and nonphotochemical quenching increased; of note,
S. trilobata experienced smaller changes. The malonaldehyde content of S. calendulacea increased, while phenols and the total antioxidant capacity
of S. trilobata declined more significantly than those of the native species tested. These results further indicate that, compared with S. calendulacea,
S. trilobata exhibited a lower loss in photosynthesis and less oxidative damage under shading. This may explain why S. trilobata tends to spread to forests
in South China.
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Kate Crane, Ross N. Cuthbert, Neil E. Coughlan, Louise Kregting, Neil Reid, Anthony Ricciardi, Hugh J. MacIsaac and Jaimie T.A. Dick
No time to dye: dye-induced light differences mediate growth rates among invasive macrophytes (pp 288–302) |
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Invasive, submerged macrophytes negatively alter aquatic ecosystems and biodiversity through disruption of ecological structure and functioning.
These plants are especially challenging and costly to control, with relatively few successful eradications. We examine the efficacy of dye treatments
to control three invasive, submerged macrophyte species: Elodea canadensis Michx., Elodea nuttallii (Planchon) H. St. John and
Lagarosiphon major (Ridley). Using an experimental mesocosm approach, growth rates of each species were monitored in relation to five light treatment
groups: light, 1×, 2×, 3× dye dosage, and complete darkness (range: 270 to 0 μmol·m-2·s-1). Dye presence did not negate growth in any
of the tested species, but the effects of treatments on invasive macrophyte growth rates differed across species. In dyed conditions, E. canadensis
exhibited significantly greater increases in length compared to E. nuttallii and L. major, whilst E. nuttallii and L. major
were lower and statistically similar. However, L. major significantly increased length relative to Elodea spp. in dark conditions.
Similarly, for biomass changes, Elodea spp. gained significantly more biomass than L. major under light and dyed conditions,
but not in the dark. Our findings suggest that the tested dye concentrations are not sufficient to halt the growth of these plants. However, under certain
conditions, they could potentially help to reduce densities of invasive macrophytes by slowing growth rates and reducing biomass in select species. Differential
responses to light could also help explain species replacement dynamics under varying environmental contexts. Overall, while further empirical research
is required, management actions that reduce light could help control aquatic macrophytes in combination with other actions, but could also simultaneously
mediate shifts in community assembly.
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Wesley J. Glisson, Rafael Contreras-Rangel, West M. Bishop and Daniel J. Larkin
Laboratory evaluation of copper-based algaecides for control of the invasive macroalga starry stonewort (Nitellopsis obtusa) (pp 303–325) |
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Nitellopsis obtusa ([Desvaux] J. Groves [1919]; Characeae), known as starry stonewort, is an invasive macroalga in Laurentian Great Lakes states and provinces
in North America. Because of its potential negative impacts on native ecosystems and recreation, N. obtusa has become a high-priority target for management.
However, there is a critical lack of foundational information on the efficacy of different algaecides, and concentrations thereof, for N. obtusa control.
Additionally, control of N. obtusa bulbils—asexual reproductive structures that are the main pathway for the establishment of new plants—has proven difficult.
We tested the efficacy of six commonly used copper-based algaecides, at a series of copper concentrations up to the maximum labeled rate, on N. obtusa thalli
(photosynthetic aboveground tissues) and bulbils in controlled laboratory experiments. Bulbils were placed above and below sediment in separate experiments to evaluate
whether sediment acted as a barrier to treatment. At 14 days after treatment (DAT), there were significant reductions in thalli biomass (34% and 40%) for two algaecides
at the highest concentration evaluated (1.0 mg Cu L-1) and significant thalli discoloration at 0.75 and 1.0 mg Cu L-1 for four algaecides.
There were no significant negative effects on N. obtusa thalli biomass or discoloration at lower concentrations of any product. For below-sediment bulbils,
none of the algaecides reduced N. obtusa viability compared to untreated controls by 56 DAT, and viability was significantly greater than in controls
for three different algaecides at 0.25 mg Cu L-1. For above-sediment bulbils, there was low sprouting across all algaecide treatments and untreated controls,
indicating inhospitable growing conditions. These findings provide a baseline for improvement of chemical treatment options for N. obtusa, provide guidance
for future research on N. obtusa control, and underscore the challenges in achieving sustained N. obtusa control.
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Stephanie A. Hall, Sarah E. Stewart-Clark and Elena Kupriyanova
Spatial and temporal monitoring of invasive Hydroides dianthus (Verrill, 1873) (Annelida, Serpulidae) in Eel Lake, Argyle, Nova Scotia using a species-specific molecular assay (pp 326–343) |
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In 2012, an invasion by a serpulid tubeworm, unknown to the Atlantic Canada region, caused heavy biofouling on an oyster lease in Eel Lake, Argyle, Nova Scotia. The species was
identified as Hydroides dianthus (Verrill, 1873), and this morphological identification was confirmed by comparing a newly sequenced COI gene fragment with H. dianthus
sequences available in GenBank. Heavy biofouling on the oyster lease resulted in the need to develop mitigation strategies. It was hypothesized that by understanding the spawning
behaviour and spatial/temporal patterns of H. dianthus larvae in Eel Lake, biofouling could be mitigated by determining an optimal depth that oyster cages should be maintained
at during its active spawning period. To monitor H. dianthus in Eel Lake, species-specific primers associated with the COI gene were developed. Specificity and sensitivity
of primers were tested, and the primer set H. dianthus COI4F/R was chosen for monitoring. Water samples were collected from Eel Lake from June to August 2013, and eDNA
was extracted. Spatial and temporal monitoring of H. dianthus using eDNA was completed at four sites (three fouled, one non-fouled), and at three depths (0.3 m, 1.5 m, and 3.0 m)
in Eel Lake. Water samples tested positive for H. dianthus in most sites and depths on June 20th, indicating a spawning event had occurred. Subsequently, no significant differences
between sites and depths were found and H. dianthus was detected throughout the summer in all locations and depths monitored. The mean % of positive PCR results significantly
increased from 18.7 to 65.0% from June to August. Results suggest that H. dianthus spawned frequently during a reproductive season ranging from at least June 20 to August 30
in Eel Lake at temperatures ~ 18–22 °C. The results of this study indicated that an optimal oyster cage depth for biofouling mitigation could not be determined and highlighted
the challenges to aquaculture associated with biofouling of H. dianthus.
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Adam J. Sepulveda, David R. Smith, Katherine M. O’Donnell, Nathan Owens, Brittany White, Catherine A. Richter, Christopher M. Merkes, Skylar L. Wolf, Mike Rau, Matthew E. Neilson, Wesley M. Daniel, Christine E. Dumoulin and Margaret E. Hunter
Using structured decision making to evaluate potential management responses to detection of dreissenid mussel (Dreissena spp.) environmental DNA (pp 344–368) |
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Environmental (e)DNA tools are sensitive and cost-effective for early detection of invasive species. However, the uncertainty associated with the interpretation of positive eDNA
detections makes it challenging to determine appropriate natural resource management responses. Multiple sources of error can give rise to positive detections of eDNA in a sample
when individuals of that species are not present at the site or a widespread infestation is not imminent. Acting on an erroneous eDNA inference could result in needless costs
or reductions in desirable resources. Alternatively, failure to rapidly act on eDNA results that truly indicate invader presence could compound negative impacts and lead to high,
long-term costs to manage infestations. We used a structured decision making (SDM) process, which incorporates tradeoffs and uncertainties, to evaluate appropriate response actions
following hypothetical eDNA detections of invasive dreissenid mussel (Dreissena spp.) eDNA in Jordanelle Reservoir, Utah (USA). We worked with decision-makers and stakeholders
to identify objectives and discrete management action alternatives to assess consequences and tradeoffs. Alternatives ranged from no action to intensive and expensive control efforts.
The best performing alternative was delayed containment described by immediate attempts to confirm the eDNA detections using non-molecular sampling techniques followed by mandatory
watercraft exit inspections to prevent dreissenid mussel spread to regional water bodies. Non-molecular sampling increased public support for management by demonstrating
a commitment to monitor the invasion state before action, whereas containment decreased likelihood of regional spread to other waters. Delayed containment had the lowest downside risk,
and the highest upside gains relative to other alternative actions. Sensitivity analyses showed our results to be robust to parameter and outcome uncertainty.
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William R. Budnick, Brian Roth, Lucas R. Nathan, Sara M. Thomas, Kelley Smith, Sarah N. Walker and Seth Herbst
Evaluation of five trap designs for removal of invasive red swamp crayfish (Procambarus clarkii Girard, 1852) in Southern Michigan: catch per unit effort, body size, and sex biases (pp 369–390) |
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Trapping and removing invasive crayfish is one of the most common forms of control, however gear-specific biases can limit effectiveness of such methods.
We evaluated five trapping gears (Gee’s minnow traps [GMT], pyramid traps [PYR], artificial refuge traps [ART], additional partition refuge traps [APART],
and juvenile traps [JUV]) for their effectiveness in a Procambarus clarkii Girard, 1852 (red swamp crayfish) removal effort among four Southern Michigan
ponds between May and October 2019. Our objectives were 1) determine which gear(s) produce the highest catch per unit effort (CPUE); 2) assess gears for body size
and sex biases; 3) ascertain the degree of seasonality in gear-specific catches and biases. We found that baited GMT and PYR traps substantially outperformed the ART,
APART, and JUV traps with respect to CPUE. However, catches of refuge-style traps trended positively over the season. Body size biases were prevalent, with GMT and PYR
traps consistently recording individuals > 30 mm carapace length. The ART and APART traps caught relatively smaller individuals but trended towards capturing larger
individuals later in the season. We observed no sex biases or biases between Form 1 and Form 2 males among the gears. Our findings support employing multiple gears
for crayfish removals but demonstrated that baited traps can remove more crayfish than unbaited traps (on a CPUE basis) and both can capture body size trends
by accounting for the timing of capture. Further, the lack of sex bias suggests any of these commonly used traps can be used to broadly sample females or male
reproductive forms. Based on our results and recommendations, the Michigan adaptive response strategy has adopted a combination GMT-APART strategy to maximize
CPUE while also targeting a wide range of crayfish sizes.
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Frank Huysentruyt, Karel Van Moer and Tim Adriaens
Testing the efficacy of different Larson trap designs for trapping Egyptian geese (Alopochen aegyptiacus L.) in Flanders (northern Belgium) (pp 391–405) |
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In Western Europe, the Egyptian goose is considered one of the most rapidly spreading invasive bird species. Listed as a species of Union Concern by the EU,
it is subject to restrictions and measures and European Member States are urged to develop management strategies. Since common techniques such as shooting, moult trapping and
egg control have been inadequate at lowering population numbers, there is a high demand for alternative effective control strategies. Here, we report on field trials testing
the use of walk-in traps with live decoy birds. Trials were spread out over several years to establish optimal trapping season and trap design and to explore different deployment
options. We found that in Belgium the breeding period was the optimal season for deploying traps, which suggests the territorial response is the main driver of trapping efficiency.
Land-based designs performed significantly better than other trap types at catching Egyptian geese and had far fewer by-catches. The strategy in which traps were deployed
at short intervals over various locations had the highest efficiency. We conclude that the use of land-based versions of this trap type can be a useful addition
to a wider management strategy when used on a large scale and aimed at trapping adult birds prior to breeding. Given the high effort needed for this type of trapping
and the expected effectiveness of other management techniques, the method is best combined with post breeding shooting.
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Mariah Doreen Millington, Bonnie Jane Holmes and Stephen Richard Balcombe
Systematic review of the Australian freshwater ornamental fish industry: the need for direct industry monitoring (pp 406–434) |
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Invasive species represent one of the greatest biological threats to Australian ecosystems this century. Facilitated by global interdependence,
increased connectivity, and established trade routes, the dissemination of non-native ornamental species has led to substantial establishments
in Australian waterways. Despite this, recent and ongoing research into the trade and invasive potential of non-native ornamental fish species
in Australia is lacking and well behind the global standard. Hampered by a shortage of adequate funding and an inability to make rapid policy-based
decisions due to industry influence, restrictions on trade have been slow or non-existent in recent years. Further, the development and maintenance
of accurate species trade lists as well as dedicated funding and a coordinated approach to compliance is currently inadequate across all Australian
jurisdictions. Here we aimed to identify if existing ornamental freshwater fish records from scientific literature in Australia, including veterinary
reports and zoonoses studies, were an appropriate alternative to direct industry monitoring necessary in producing comprehensive trade lists.
To test this alternative approach, we identified and collated scientific literature that had recorded captive freshwater fish in the Australian
ornamental industry. Our review identified a still inchoate scientific body of literature that is a poor substitute for direct survey approaches,
with minimal reporting evident in Australia on the freshwater ornamental fish in trade. Assessment of available species records indicated unassessed,
greylisted freshwater fish form a substantial part of the Australian ornamental industry. Nomenclature issues and potential exploitation by the ornamental
fish industry were also identified. Given the paucity of contemporary literature on the presence and abundance of traded species within Australia,
initiatives including pet store surveys and e-commerce monitoring are vital to collate a complete list of traded species necessary for management
of this non-native community. We highlight key research priorities and provide recommendations on the future management needs of the Australian freshwater
ornamental fish industry.
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Mary E. Brown, Robert H. Robins and Pamela J. Schofield
Risk assessment of chanchita Cichlasoma dimerus (Heckel, 1840), a newly identified non-native cichlid fish in Florida (pp 435–448) |
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The risk of a newly discovered non-native fish species in Florida (USA): Cichlasoma dimerus ([Heckel, 1840]; Family: Cichlidae) is assessed.
Its tolerance to cold temperatures was experimentally evaluated and information on its biology and ecology was synthesized. In the cold-temperature tolerance
experiment, temperature was lowered from 24 °C by increments of 1 °C per hour, mimicking a typical cold weather front. Fish lost equilibrium at a mean temperature
of 7.8 °C and died at 4.7 °C. Those values are lower than most other non-native fishes from the state that have been experimentally evaluated, and it appears
C. dimerus is the most cold-tolerant cichlid established in Florida. The combination of cold-temperature tolerance and other biological/ecological factors
(e.g., adult size, reproduction and parental care, diet, habitat, and other behaviors) along with the geographic range and habitat diversity of specimens vouchered
in museums, indicate C. dimerus may be able to invade many freshwater ecosystems in the state, including environmentally sensitive freshwater springs.
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Adolphe O. Debrot, Erik Boman and Hannah Madden
Case study of a Rapid Response Removal Campaign for the invasive alien green iguana, Iguana iguana (pp 449–465) |
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The Invasive Alien Green Iguana (IAGI), Iguana iguana, has spread worldwide via the pet trade, as stowaways and via other means and has become a pest species
of global concern. It also represents a major threat to the endemic Lesser Antillean Iguana, Iguana delicatissima, on St. Eustatius. Following the capture
of an adult female IAGI on St. Eustatius in early 2016, we conducted a Rapid Response Removal Campaign (RC) from April 2016 to January 2017. Three sets of directed
visual surveys totaling 409.5 observer hours and covering a combined trajectory of 114.2 km realized only a single detection of a hybrid that was later removed.
During the remainder of the campaign period, an additional four IAGI hybrids were opportunistically detected and removed thanks to park staff or community involvement.
Since the end of the campaign, eight additional detections and removals have been realized, three of which were IAGIs caught while offloading freight in the harbour
and five of which were hybrids caught in surrounding suburban areas. We suggest that at least four distinct IAGI introductions to St. Eustatius occurred between 2013
and 2020. Our results show the value of motivating and mobilizing stakeholders and the public at an early stage of an invasion. Since the program’s initiation,
eight of the 13 iguanas detected for culling were thanks to public and key stakeholder support and involvement. Four years after our campaign, the number of IAGIs
and their hybrids still appear to be limited and concentrated in and around inhabited areas. Additional removal campaigns should be initiated as soon as possible,
firmly based in public outreach, motivation and engagement. New legislation is needed to prohibit the importation, possession and harbouring of IAGIs or hybrids
and to provide a framework for long-term structural funding required for effective control and removal. Routine fumigation and rigorous inspection of arriving cargo
to eliminate the risk of stowaway IAGIs are also recommended. Culling of IAGIs is recommended for the port of St. Maarten, which serves as a major point of dispersal
of IAGIs to St. Eustatius and likely also other islands in the region.
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