Multi-agency perspectives on managing mangrove wetlands and the mosquitoes they produce.

A group of researchers, mosquito and coastal managers, and consultants joined together to explore issues of concern to coastal and mosquito management in mangrove forests. At a 1-day workshop in Florida, participants identified issues that are important for their roles. The issues were subsequently compiled into a matrix and the participants were asked to individually assess the importance and urgency of each. The most important issues for everyone included habitat responses to management, community attitude, public education, interaction between agencies, local connectivity, sea-level rise (SLR) loss of wetlands, and conservation. Most urgent were public education, conservation easements, local connectivity, SLR, loss of wetland, restoration, and conservation. There were differing viewpoints among the roles that appeared to be related to responsibility for and ability to influence on-ground outcomes. This is reflected in mosquito and coastal managers who viewed issues broadly and ascribed higher levels of importance and urgency to them than did researchers and consultants. We concluded that collaboration is a key issue. Barriers to collaboration include knowledge differences between agencies. Facilitators of collaboration include interaction, trust, and shared goals.

Laboratory evaluation of predation on mosquito larvae by Australian mangrove fish.

A series of laboratory experiments compared predation rates of three native eastern Australian mangrove fish species (Psuedomugil signifer, Hyseleotris galii, Pseudogobius sp.) and the exotic Gambusia holbrooki on 2nd and 4th instar Aedes vigilax larvae, in order to determine their potential as mosquito control agents in mangrove forests. All four species preyed on significant numbers of both 2nd and 4th instar larvae. All showed a similar pattern of larval consumption, gorging on larvae in the first hour of each experiment, before reducing to a relatively constant background feeding rate. Gambusia holbrooki showed the highest larval consumption rates, but is unsuitable as a mosquito control agent due to it being an exotic pest species in Australia. Of the three native species, P. signifer showed the greatest potential as a mosquito control agent, having consumption rates comparable to G. holbrooki, and was the only species that did not show a significant reduction in larval consumption in the night experiments.

Comparing Aedes vigilax Eggshell Densities in Saltmarsh and Mangrove Systems with Implications for Management.

Aedes vigilax (Skuse), a nuisance and disease vector, is prolific in intertidal wetlands in Australia. Aedine mosquitoes oviposit directly onto substrate. The eggshells are relatively stable spatially and temporally, providing an estimate of mosquito larval production. The aims of the research were to compare, at a general level, oviposition in mangroves and saltmarshes, and to compare oviposition between different habitats within mangroves and saltmarshes. The results indicated that there were no significant differences between production in mangrove and saltmarsh overall. However, within each system there were significant differences between habitat classes, with mangrove hummocks being the most productive. All classes, except for fringing mangrove forests, produced sufficient densities of eggshells (>0.05/cc) to warrant concern. While mosquito production in mangroves is known, the significantly higher production rates in the mangrove hummock habitats had not been demonstrated. This warrants improved management strategies that both specifically target these parts of mangrove systems and, secondly, addresses the longer-term potential for mangrove hummock habitats developing in the future; such as, in response to sea level rise and mangrove encroachment into saltmarsh. A strategy to increase tidal flushing within the systems would improve water quality and mitigate adverse impacts while providing a source reduction outcome.

Oviposition and larval habitat preferences of the saltwater mosquito, Aedes vigilax, in a subtropical mangrove forest in Queensland, Australia.

Our aim was to investigate the oviposition and larval habitats of the saltwater mosquito Aedes vigilax (Skuse) (Diptera: Culicidae) in a mangrove forest system in subtropical Queensland, Australia. Eggshells (indicators of oviposition) and larvae were sampled in three habitat classes that were depicted in a schematic model. Two classes were in depressions or basins, either with hummocks or dense pneumatophore substrates, both of which retained water after tidal flooding. The third class was in freely flushed mangroves that corresponded with more frequent tidal connections than the depression classes. ANOVA and Tukey-Kramer tests were used to analyze the data. The null hypotheses were rejected: the hummock class was a significant habitat based on both eggshell and larval data. The conclusion was that mosquito production in the mangrove system was distributed unevenly between habitat classes, and that the hummock class had conditions suited to the requirements of the immature stages of Ae. vigilax. This research has the potential to inform mosquito management strategies by focusing treatment on the problem habitats and underpinning habitat modifications including reducing water retention in the basins.