The pond environment has changed a lot since it was traditionally used for aquaculture. Changes like increased runoff, mangrove and algae invasion, and seawall deterioration have affected the pond’s community composition, and this is likely to have corresponding effects on the diets of  resident species. Some of these changes exert spatial effects (algae and mangroves, for instance, grow patchily in and around the pond) and others are expected to have a strong seasonal effect (runoff increases during the stormy winter months, affecting salinity and nutrient input). My project will investigate how the food web of the fishpond changes spatially and seasonally.

Moi (Polydactylus sexfilis) for sale in a Chinatown fish market.

I’m predominantly interested in fish that are important to Hawai’ian aquaculture (awa’awa, moi, and aholehole). I will gather carbon and nitrogen stable isotope data from these fish as well as primary producers (e.g., microalgae — see “Mystery of the Fuzz, May 31 — and Gracilaria salicornia, an invasive macroalgae), invertebrates (alpheids and crabs), and predators that consume both juvenile fish and invertebrates.

 Opae grazing at the sea wall. Small shrimp like this play an integral part in most estuarine food webs, which is why I’m measuring stable isotopes from these too.

Questions that I hope to answer include:

1) Are fish eating invertebrates or microalgae that live in the Gracilariacanopy? I.e., are they taking advantage of this invasive species to obtain food?
2) Are fish diets different for the same species of fish living in different parts of the pond?
3) Does food web structure change seasonally? How strongly is the pond’s food web affected by periods of winter runoff or dry summers?

I will answer these questions using a combination of stable isotope biogeochemistry, stomach content analysis, and community surveys. Eventually I will be able to build spatial models that can predict how fish diet will change over space and time within the pond. This project is part of a collaborative effort to understand the physical and biological behavior of the fishpond and provide useful information for pond managers and the ahupua’a. Besides the Donahue Lab, other groups involved in the project are the Thomas Lab (nutrient dynamics and flow regimes around G. salicornia), the Ruttenberg Lab (physical oceanography and pore-water nutrients) and the Glazer Lab (biogeochemical reactions at the sediment-water interface, including those which involve the microphytobenthic (MPB) mat).
One of my goals is to gather information that will be helpful for Paepae o He’eia in managing fish stocks in the pond.

Milkfish (Chanos chanos) at a market in Chinatown in Honolulu. Milkfish can be found in a lot of Hawaiian fishponds and have a diet similar to that of moi. They are easy to raise because they eat mostly microphytobenthos from the top of the substrate.

This research is funded by a Graduate Research Fellowship from theNational Science Foundation.

One Response to “Project”
  1. Chris says:

    It’s been a long but exciting trip from Sea Monkeys and Hedgehogs to your current studies, Megsie.
    Way to go.
    3 of my brains can fit into yours.
    Happy Birthday most intelligent, beautiful, talented Maggie.

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  • Mahalo Nui Loa

    I recently graduated from the Donahue Lab at the University of Hawai'i at Manoa and am currently a graduate student at the University of Washington. This research is funded by a Graduate Research Fellowship from the National Science Foundation, as well a scholarship from the Seattle chapter of the Achievement Rewards for College Scientists (ARCS) Foundation.
  • “Where do ecological ideas come from? …Most do not spring deductively from the minds of ecologists, like Athena from the head of Zeus. Instead, they emerge when ecologists absorb the essential spirit of individual places– their genius loci.”

    ~Mary V. Price & Ian Billick, "The Ecology of Place"
  • “Aloha is the intelligence with which we meet life.”

    ~Olana A'i, Kumu Hula

  • “I no longer say ‘Hawaiian ways of knowing’ anymore. Because people relegate that to the margins. ‘Ways of knowing,’ as if it’s a quaint, anthropologic way of describing something outside us. No, it’s ‘epistemology,’ the philosophy of knowledge. Land educates. ‘Ike ‘aina. The land of your birth educates you. This land here educates you.”

    ~Manu Meyer

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