Witting Jan H.

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Witting
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Jan H.
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  • Preprint
    High apex predator biomass on remote Pacific islands
    ( 2006-09-06) Stevenson, Charlotte ; Katz, Laure S. ; Micheli, Fiorenza ; Block, Barbara A. ; Heiman, Kimberly W. ; Perle, Chris ; Weng, Kevin ; Dunbar, Robert B. ; Witting, Jan H.
    On coral reefs in Palmyra—a central Pacific atoll with limited fishing pressure—total fish biomass is 428 and 299% greater than on reefs in nearby Christmas and Fanning Islands. Large apex predators –groupers, sharks, snappers, and jacks larger than 50 cm in length- account for 56% of total fish biomass in Palmyra on average, but only 7% and 3% on Christmas and Fanning. These biomass proportions are remarkably similar to those previously reported for the remote and uninhabited Northwest Hawaiian Islands (NWHI) and densely populated Main Hawaiian Islands (MHI), although Palmyra’s reefs are dominated in biomass by sharks (44% of the total), whereas the NWHI by jacks (39%). Herbivorous fish biomass was also greater on Palmyra than on Christmas and Fanning (343% and 207%, respectively). These results and previous findings indicate that remote, uninhabited islands support high levels of consumers, and highlight the importance of healthy coral reef ecosystems as reference points for assessment of human impacts and establishment of restoration goals.
  • Article
    Evidence and patterns of tuna spawning inside a large no-take marine protected area
    (Nature Research, 2019-07-24) Hernández, Christina M. ; Witting, Jan H. ; Willis, Claire ; Thorrold, Simon R. ; Llopiz, Joel K. ; Rotjan, Randi
    The Phoenix Islands Protected Area (PIPA), one of the world’s largest marine protected areas, represents 11% of the exclusive economic zone of the Republic of Kiribati, which earns much of its GDP by selling tuna fishing licenses to foreign nations. We have determined that PIPA is a spawning area for skipjack (Katsuwonus pelamis), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares) tunas. Our approach included sampling larvae on cruises in 2015–2017 and using a biological-physical model to estimate spawning locations for collected larvae. Temperature and chlorophyll conditions varied markedly due to observed ENSO states: El Niño (2015) and neutral (2016–2017). However, larval tuna distributions were similar amongst years. Generally, skipjack larvae were patchy and more abundant near PIPA’s northeast corner, while Thunnus larvae exhibited lower and more even abundances. Genetic barcoding confirmed the presence of bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tuna larvae. Model simulations indicated that most of the larvae collected inside PIPA in 2015 were spawned inside, while stronger currents in 2016 moved more larvae across PIPA’s boundaries. Larval distributions and relative spawning output simulations indicated that both focal taxa spawned inside PIPA in all 3 study years, demonstrating that PIPA is protecting viable tuna spawning habitat.
  • Article
    Corrigendum
    (American Meteorological Society, 2014-12) Leslie, William R. ; Karnauskas, Kristopher B. ; Witting, Jan H.
  • Dataset
    Shipboard ADCP profiles, central equatorial Pacific Ocean, 2003-2012
    ( 2014-07-17) Karnauskas, Kristopher B. ; Witting, Jan H.
    This data set contains 23 individual NetCDF files, each containing subsurface zonal and meridional velocity profiles (along with time/space coordinates) measured by shipboard ADCP.