Thompson Michael A.

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Michael A.

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Now showing 1 - 5 of 5
  • Article
    Bottom side-roll feeding by humpback whales (Megaptera novaeangliae) in the southern Gulf of Maine, U.S.A
    (John Wiley & Sons, 2013-07-24) Ware, Colin ; Wiley, David N. ; Friedlaender, Ari S. ; Weinrich, Mason T. ; Hazen, Elliott L. ; Bocconcelli, Alessandro ; Parks, Susan E. ; Stimpert, Alison K. ; Thompson, Michael A. ; Abernathy, Kyler
    Humpback whales (Megaptera novaeangliae) are known for the variety and complexity of their feeding behaviors. Here we report on the use of synchronous motion and acoustic recording tags (DTAGs) to provide the first detailed kinematic descriptions of humpback whales using bottom side-rolls (BSRs) to feed along the seafloor. We recorded 3,505 events from 19 animals (individual range 8–722). By animal, mean BSR duration ranged from 14.1 s to 36.2 s.; mean body roll angle from 80º to 121º, and mean pitch from 7º to 38º. The median interval between sequential BSRs, by animal, ranged from 24.0 s to 63.6 s and animals tended to maintain a consistent BSR heading during long BSR series encompassing multiple dives. BSRs were most frequent between 2200 and 0400. We identify three classes of behavior: simple side-roll, side-roll inversion, and repetitive scooping. Results indicate that BSR feeding is a common technique in the study area and there is both coordination and noncoordination between animals. We argue that this behavior is not lunge feeding as normally characterized, because animals are moving slowly through the event. The behavior also leads to vulnerability to entanglement in bottom-set fishing gear, a major mortality factor for the species.
  • Article
    Sensitivity of sand lance to shifting prey and hydrography indicates forthcoming change to the northeast US shelf forage fish complex
    (Oxford University Press, 2021-01-26) Suca, Justin J. ; Wiley, David N. ; Silva, Tammy L. ; Robuck, Anna R. ; Richardson, David E. ; Glancy, Sarah G. ; Clancey, Emily ; Giandonato, Teresa ; Solow, Andrew R. ; Thompson, Michael A. ; Hong, Peter ; Baumann, Hannes ; Kaufman, Les ; Llopiz, Joel K.
    Northern sand lance (Ammodytes dubius) and Atlantic herring (Clupea harengus) represent the dominant lipid-rich forage fish species throughout the Northeast US shelf and are critical prey for numerous top predators. However, unlike Atlantic herring, there is little research on sand lance or information about drivers of their abundance. We use intra-annual measurements of sand lance diet, growth, and condition to explain annual variability in sand lance abundance on the Northeast US Shelf. Our observations indicate that northern sand lance feed, grow, and accumulate lipids in the late winter through summer, predominantly consuming the copepod Calanus finmarchicus. Sand lance then cease feeding, utilize lipids, and begin gonad development in the fall. We show that the abundance of C. finmarchicus influences sand lance parental condition and recruitment. Atlantic herring can mute this effect through intra-guild predation. Hydrography further impacts sand lance abundance as increases in warm slope water decrease overwinter survival of reproductive adults. The predicted changes to these drivers indicate that sand lance will no longer be able to fill the role of lipid-rich forage during times of low Atlantic herring abundance—changing the Northeast US shelf forage fish complex by the end of the century.
  • Article
    High collocation of sand lance and protected top predators: implications for conservation and management
    (Wiley Open Access, 2020-10-06) Silva, Tammy L. ; Wiley, David N. ; Thompson, Michael A. ; Hong, Peter ; Kaufman, Les ; Suca, Justin J. ; Llopiz, Joel K. ; Baumann, Hannes ; Fay, Gavin
    Spatial relationships between predators and prey provide critical information for understanding and predicting climate‐induced shifts in ecosystem dynamics and mitigating human impacts. We used Stellwagen Bank National Marine Sanctuary as a case study to investigate spatial overlap among sand lance (Ammodytes dubius), a key forage fish species, and two protected predators: humpback whales (Megaptera novaeangliae) and great shearwaters (Ardenna gravis). We conducted 6 years (2013–2018) of standardized surveys and quantified spatial overlap using the global index of collocation. Results showed strong, consistent collocation among species across seasons and years, suggesting that humpback whales and great shearwater distributions are tightly linked to sand lance. We propose that identifying sand lance habitats may indicate areas where humpbacks and shearwaters aggregate and are particularly vulnerable to human activities. Understanding how sand lance influence predator distributions can inform species protection and sanctuary management under present and future scenarios.
  • Article
    Whales and waves : humpback whale foraging response and the shoaling of internal waves at Stellwagen Bank
    (John Wiley & Sons, 2015-04-02) Pineda, Jesus ; Starczak, Victoria R. ; da Silva, Jose C. B. ; Helfrich, Karl R. ; Thompson, Michael A. ; Wiley, David N.
    We tested the hypothesis that humpback whales aggregate at the southern flank of Stellwagen Bank (SB) in response to internal waves (IWs) generated semidiurnally at Race Point (RP) channel because of the presence of their preferred prey, planktivorous fish, which in turn respond to zooplankton concentrated by the predictable IWs. Analysis of synthetic aperture radar (SAR) images indicates that RP IWs approach the southern flank of SB frequently (∼62% of the images). Published reports of whale sighting data and archived SAR images point to a coarse spatial coincidence between whales and Race Point IWs at SB's southern flank. The responses of whales to IWs were evaluated via sightings and behavior of humpback whales, and IWs were observed in situ by acoustic backscatter and temperature measurements. Modeling of IWs complemented the observations, and results indicate a change of ∼0.4 m/s in current velocity, and ∼1.5 Pa in dynamic pressure near the bottom, which may be sufficient for bottom fish to detect the IWs. However, fish were rare in our acoustic observations, and fish response to the IWs could not be evaluated. RP IWs do not represent the leading edge of the internal tide, and they may have less mass-transport potential than typical coastal IWs. There was large interannual variability in whale sightings at SB's southern flank, with decreases in both numbers of sightings and proportion of sightings where feeding was observed from 2008 to 2013. Coincidence of whales and IWs was inconsistent, and results do not support the hypothesis.
  • Article
    Birds of a feather eat plastic together: high levels of plastic ingestion in Great Shearwater adults and juveniles across their annual migratory cycle
    (Frontiers Media, 2022-01-05) Robuck, Anna R. ; Hudak, Christine A. ; Agvent, Lindsay ; Emery, Gwenyth ; Ryan, Peter G. ; Perold, Vonica ; Powers, Kevin D. ; Pedersen, Johanna ; Thompson, Michael A. ; Suca, Justin J. ; Moore, Michael J. ; Harms, Craig A. ; Bugoni, Leandro ; Shield, Gina ; Glass, Trevor ; Wiley, David N. ; Lohmann, Rainer
    Limited work to date has examined plastic ingestion in highly migratory seabirds like Great Shearwaters (Ardenna gravis) across their entire migratory range. We examined 217 Great Shearwaters obtained from 2008–2019 at multiple locations spanning their yearly migration cycle across the Northwest and South Atlantic to assess accumulation of ingested plastic as well as trends over time and between locations. A total of 2328 plastic fragments were documented in the ventriculus portion of the gastrointestinal tract, with an average of 9 plastic fragments per bird. The mass, count, and frequency of plastic occurrence (FO) varied by location, with higher plastic burdens but lower FO in South Atlantic adults and chicks from the breeding colonies. No fragments of the same size or morphology were found in the primary forage fish prey, the Sand Lance (Ammodytes spp., n = 202) that supports Great Shearwaters in Massachusetts Bay, United States, suggesting the birds directly ingest the bulk of their plastic loads rather than accumulating via trophic transfer. Fourier-transform infrared spectroscopy indicated that low- and high-density polyethylene were the most common polymers ingested, within all years and locations. Individuals from the South Atlantic contained a higher proportion of larger plastic items and fragments compared to analogous life stages in the NW Atlantic, possibly due to increased use of remote, pelagic areas subject to reduced inputs of smaller, more diverse, and potentially less buoyant plastics found adjacent to coastal margins. Different signatures of polymer type, size, and category between similar life stages at different locations suggests rapid turnover of ingested plastics commensurate with migratory stage and location, though more empirical evidence is needed to ground-truth this hypothesis. This work is the first to comprehensively measure the accumulation of ingested plastics by Great Shearwaters over the last decade and across multiple locations spanning their yearly trans-equatorial migration cycle and underscores their utility as sentinels of plastic pollution in Atlantic ecosystems.