Mosquito population control by aquatic predators: a global meta-analysis of predation efficacy by fish and odonate naiads

Technical Summary: Mosquito Population Control by Aquatic Predators

Problem Statement
While biological control using aquatic predators presents a sustainable alternative to chemical insecticides for mosquito management, the specific functional traits governing predation efficacy remain poorly quantified on a global scale. Existing literature often relies on broad taxonomic generalizations, and there is a lack of comprehensive data regarding how predator identity, body size, dietary guilds, and prey characteristics interact to determine consumption rates. Furthermore, the primary literature exhibits significant geographical bias, being heavily skewed toward Asia (particularly India) while under-representing Africa, the Americas, and Europe.

Methodology
This study conducted a global meta-analysis comprising 755 effect sizes drawn from 59 distinct studies. The researchers employed multilevel models to evaluate the influence of several variables on consumption rates, defined as the consumption rate (CR) in larvae per predator per hour ($larvae \cdot predator^{-1} \cdot h^{-1}$). Key variables analyzed included:

• Predator Identity: Comparing fish versus odonate (dragonfly/damselfly) naiads.
• Functional Traits: Predator body size and dietary guilds (specialists vs. generalists).
• Prey Characteristics: Specific traits of the mosquito larvae.
• Methodological Factors: Experimental design variations, including exposure time.

The analysis incorporated robust publication-bias corrections and accounted for methodological heterogeneity across different experimental designs to ensure the validity of the aggregated data.

Key Results

1. Taxonomic Identity vs. Functional Traits: Grouping predators solely by broad taxonomic identity (fish vs. naiads) obscured the central patterns in the data. While naiads generally outperformed fish in direct within-study comparisons, this difference was driven almost entirely by non-mosquitofish species, which proved to be the least efficient predator group overall.
2. Specialization over Taxonomy: Mosquitofish (Gambusia spp.) and dragonfly naiads were statistically indistinguishable in terms of predation efficacy. This indicates that dietary specialization, rather than taxonomic classification, is the stronger predictor of consumption rates.
3. Body Size Effects: Predator body size showed a strong, positive correlation with consumption rates in naiads (driven primarily by dragonflies). In contrast, body size showed no significant or even negative relationship with consumption rates in fish.
4. Methodological Artifacts: Extreme heterogeneity across studies was heavily structured by methodological traits. Specifically, exposure time acted as a severe rate-suppressor; prolonged assay durations led to a drastic underestimation of per-hour consumption rates, likely due to predator satiety or handling constraints.
5. Predictive Power: A combined model incorporating all significant ecological moderators simultaneously explained a substantial share of the between-study variance, confirming that predator-prey dynamics in these systems are highly predictable when functional traits are considered.

Significance and Claims
The paper asserts that effective biological control strategies cannot rely on broad taxonomic assumptions but must instead utilize evidence-based trait-matching. The authors claim that management programs should prioritize body size when deploying insect predators, specifically selecting the largest individuals within species known to consume mosquito larvae. Furthermore, the study advocates for favoring insectivorous fish species over generalists.

Crucially, the paper highlights a limitation in current experimental scaling: short-term laboratory assays artificially inflate efficacy estimates. Therefore, the authors conclude that multi-duration assessments are essential to accurately scale biocontrol predictions from controlled experimental arenas to complex, real-world ecosystems. The study emphasizes that while the primary literature is geographically skewed, the functional relationships identified provide a robust framework for improving mosquito control efficacy globally.