Ascidians (colonial sea squirts) living on the invasive algae Gracilaria salicornia.
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.
Questions that I hope to answer include:
1) Are fish eating invertebrates or microalgae that live in the Gracilaria canopy? 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.
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 Gracilaria canopy? 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 the National Science Foundation.
