Research
Reconciling wetland conservation and large-scale agriculture:
Strategies for successfully promoting biodiversity and nature’s benefits within agriculture is good farming. In California, rice farmers flood their fields each winter, supporting millions of migratory waterbirds and other wetland-associated wildlife. Yet, as frequent droughts increase water prices, some growers are beginning to search for alternatives to winter flooding and others are transitioning away from rice entirely. This project seeks to determine whether introducing fish onto rice farms represents a viable path forward for incentivizing winter field flooding. Fish could incentivize flooding by providing growers a valuable ‘second crop’ or payments to support threatened fish, while also mitigating methane emissions. However, no studies have explored how fish interact with waterbirds in rice fields, let alone studied how the practice of introducing fish might affect rice production. Leveraging a large-scale, manipulative experiment in California rice farms, we seek to:
Quantify biological interactions between waterbirds and introduced fish, including the strength of predation, competition, and/or facilitation.
Trace the cascading effects of waterbirds and fish in flooded fields, measuring potential effects on rice yields, weed production, nutrient cycling, and straw decomposition.
Measure the degree to which fish and/or waterbirds can protect our climate.
Benefits to agriculture
We hope our work will benefit growers in at least three ways. First, our research may point the way towards strategies for harnessing biodiversity to improve yields and profits. For example, if waterbirds and fish operate in a similar manner to the co-culture systems that are common in China, then reduced weed densities and increased soil fertility could alleviate herbicide and fertilizer application rates and costs. Second, if we find fish reduce methane effluxes, then our project may also offer growers a strategy to address rising federal and state-level concerns about agricultural emissions and or offer additional ways to achieve carbon credits (e.g., California AB1496). Finally, this research may help reconcile existing tensions between growers and fish conservationists. Indeed, there is a possibility for an alternative future, where rice growers act as stewards for California’s native fishes, providing their fields as winter nurseries and reaping the benefits they provide in return.
Benefits to conservation
Each winter, millions of waterfowl overwinter in the California, utilizing the flooded rice fields that now act as surrogates for the wetlands that used to cover the Central Valley. Yet climbing water prices have led to growers to begin turning away from flooding, threatening the future and sustainability of this biodiverse agroecosystem. We seek to determine whether introducing more diversity (i.e., fish) could bolster agronomic benefits and mitigate costs such that the practice of winter field flooding may be sustained into the future. In doing so, our study may also provide a path forward for sharing farming landscapes with California’s native fish, over 80% of which are either extinct or at risk of extinction.
Harnessing a “fear” odor for invasive fish management:
The landscape of information in aquatic environments stinks – that is, aquatic organisms rely extensively on olfactory information to survive and reproduce. One such organism, the sea lamprey (Petromyzon marinus), depends on a variety of odors to guide its movement decisions during its upstream spawning migration. Among this is an alarm cue, a chemical mixture released from injuries that guides migrants around areas where predators are active. This cue elicits a marked anti-predator response in individuals exposed to injured or dead lamprey. The sea lamprey is a historically destructive invasive species in the Laurentian Great Lakes, leading to significant ecological and economic damage if left unchecked. Management efforts including dams and lamprey-specific pesticides have been largely successful but adding tools to the management toolbox is necessary due to societal pressures to reduce pesticide use and remove dams, and uncertainties regarding lamprey resistance to pesticides and frequency of dam failures. Harnessing the lamprey’s innate behavioral response to this ‘fear’ odor could be a fruitful supplementary control method by manipulating movement decisions to benefit management during the fish’s migration. The chemistry of alarm cues has proven elusive. We used behaviorally guided fractionation in controlled laboratory raceways to test behavioral reactivity to compounds believed to be a part of this cue. The knowledge gained in the study pushed us further to understanding the chemical constituents that make up the sea lamprey alarm cue mixture and will inform future studies aiming to understand the makeup of the cue. Once the chemistry is known, managers will be provided with a supplementary control technique for dually managing invasive species and species of conservation concern, and science will be provided with the first full description of a fish alarm cue mixture, aiding in the understanding of how organisms use olfaction in predator-prey dynamics.
Relevant publications:
Mensch, E.L., Dissanayake, A.A., Nair, M.G., Wagner, C.M. (2022) Sea Lamprey Alarm Cue Comprises Water- and Chloroform- Soluble Components. Journal of Chemical Ecology 48(9), 704-717. https://doi.org/10.1007/s10886-022-01384-0
Mensch, E.L., Dissanayake, A.A., Nair, M.G., Wagner, C.M. (2022) The effect of putrescine on space use and activity in sea lamprey (Petromyzon marinus). Scientific Reports 12, 17400. https://doi.org/10.1038/s41598-022-22143-x.
Genetic rescue, behavior, and conservation of fishes:
Augmenting wild populations with translocated individuals is a powerful conservation tool to achieve genetic rescue, but little is known about the role mating behavior plays in the success of augmentation efforts. We studied the behavior of male Trinidadian guppies Poecilia reticulata introduced into experimental mesocosm populations and assessed whether mating behavior influenced reproductive success. A previously published analysis of the same experiment found that populations from the one Trinidadian river (the Quare River) had higher immigrant reproductive success than populations from another river (the Marianne River), contributing to higher population fitness following augmentation. However, the reason for high immigrant reproductive success remained unclear. Our behavioral observations of a subset of those populations revealed that immigrant males from Quare (but not Marianne) performed more sexual displays and forced copulations and had marginally higher reproductive success than resident males. These results, combined with significant differences in reproductive success and population fitness reported in the previous study, suggest that mating behavior may have improved the outcome of augmentation by increasing genetic admixture. We urge wildlife managers and researchers to consider mating behavior as a factor influencing augmentation success.
Relevant publications:
- Mensch, E.L., Kronenberger, J.A., Broder, E.D., Fitzpatrick, S.W., Funk, W.C., Angeloni, L.M. (2019) A potential role for immigrant reproductive behavior in the outcome of population augmentations. Animal Conservation, 22(5), 463-471. https://doi.org/10.1111/acv.12486