My research focuses on developing quantitative tools to predict the life history, distribution and abundance, and conservation status of species. Most of the tools I build focus on melding natural history, formal models of ecological processes, and modern big data approaches. Current research projects include dynamic ocean management in the Central Pacific, integrated Bayesian life history models, and pelagic shark community assembly.
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Ensemble Random Forests — How can distribution models be built when there are exceptionally few locations where a species is detected? Recent work with the NOAA PIFSC and WPRFMC has lead to the development of the Ensemble Random Forest algorithm to tackle datasets with rare and ultra-rare presences but a host of absences. This machine-learning approach is an intuitive extension to the Random Forests algorithm and has very high performance at predicting where the species is present. Published in Endangered Species Research. This model has been used to model the distribution of rare cetacean species in the Mariana Archipelago and is published in Frontiers in Marine Science.
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Basking Sharks -- The Bay of Fundy is a hyper-productive gyre system in the Northwest Atlantic and has some of the strongest tidal swings in the world. Intense phytoplankton blooms are grazed heavily by Calanus finmarchicus copepods which, as the bloom wanes, diapause in the deep-waters of the bay, Grand Manan Basin. These sinking, resting copepods form a thick layer of prey that Basking Sharks travel from the warm-waters of the Caribbean to consume. My master's research was concerned with resolving the spatial dynamics of Basking Sharks within the Bay of Fundy over the course of their visiting season (June - October). A maximum entropy distribution model was used to determine the spatial patterns from 23 years of presence-only locations. You can hear more about this research with an interview I did with CBC's Paul Castle in 2013 (on the left).
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Florida Bass Mark-Recapture — As part of my PhD, I was interested in how the Florida Bass population might respond to habitat augmentation. I took advantage of many students before me tagging individuals with Floy (see the yellow tags in the top video) and PIT tags to track the abundance of Florida Bass in lakes with and without the augmentation. I used day and night electrofishing (see the bottom video) as well as angling to mark new fish and recapture previously tagged individuals with the help of many friends, technicians, and volunteers. I found very little effect on Florida Bass population dynamics following augmentation in the time frame of my study. This was not terribly surprising as the brush piles did little to increase primary productivity in the systems and, thus, did not alleviate the density-dependent bottleneck on young-of-the-year fish.
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Lake Community Dynamics — The most laborious and enjoyable component of the Florida Lake research was conducting camera monitoring of each lake in areas with and without brush piles. With 642 camera surveys completed, 18 terabytes of video, and 9, 575 fish observed, there was a lot to analyze. In my dissertation, I was primarily concerned with changes in the hyper-local community throughout each lake. I observed that brush piles were strong habitat filters overall with the effect exacerbated in the speciose lake. Larger-bodied taxa were more likely to occupy brush piles than small body fish though fry and age-0 Florida Bass as well as Bluegill fry did occupy the brush piles following spawning season for the respective species. For the analysis, I extended a multilevel occupancy model to a multi-species variant.
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Brazilian Guitarfish — Led by Dr. Fabio Caltabellotta, I developed a Bayesian age-growth model for Pseudobatos horkelii, Pseudobatos percellens, and Zapteryx brevirostris in southern Brazil. The resulting model was used to estimate age and growth parameters for these three priority guitarfish species listed as Critically Endangered, Near Threatened, and Vulnerable by the International Union for the Conservation of Nature. Now published: doi: 10.1111/jfb.14123
![]() (Above) Bowtie sections of guitarfish vertebrae for the three Brazilian guitarfish species showing off the classic banding patterns left behind by annual growth spurts. (Left) Age-growth relationships for three Brazilian Guitarfish species. Age is on the x-axis in units of years and growth is on the y-axis in units of centimeters of total length.
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Brazilian Electric Ray — Led by Dr. Fernanda Rolim, a postdoc at Universidade Estadual Paulista in São Paolo, Brazil, I extended the Brazilian guitarfish model to estimate two-dimensional growth of Narcine brasiliensis, the Brazilian Electric Ray, in southern Brazil. The joint estimation of length-weight and age-growth parameters was added along with derivations of age at maturity, longevity, and mortality at age. A significant component was incorporating uncertainty in size at birth into the von Bertalanffy growth model.
Now published: doi: 10.1111/jfb.14378 |
![]() (Above) Silhouettes of Goblin Sharks through the ages. (top) 1898 in the description of the species by David Starr Jordan. (top middle) 1904 by King Bragança of Portugal. (top bottom) 1909 by Hussakof and the renaming of Mitsukurina to Scapanorhynchus for a time. (bottom) 1981 by Cadenat and Blache in Requins de Méditerranée et d' Atlantique.
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Goblin Shark — Led by myself and Dr. Fabio Caltabellotta, we estimated the first age-growth relationship for Goblin Sharks (Mitsukurina owstoni), one of the largest deepwater sharks. Fabio developed a method to highlight the classic banding pattern that allowed an age reading on a specimen caught in Brazil in 2008. I developed a Bayesian age-growth model that used back-calculated lengths at age from this specimen, data on maximum male sizes, and data on size at birth to estimate the first age-growth parameters for the species. We are excited to age more specimens in the future. Now published: doi.org/10.1071/MF19370
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Protected Species Bycatch — As part of a collaboration with the NOAA Pacific Islands Fisheries Science Center, NOAA Pacific Islands Regional Office, and the Western Pacific Regional Fisheries Management Council, I have worked to help model the trajectory of two populations of protected sea turtle species: western Pacific Leatherbacks and north Pacific Loggerheads. This species are caught incidentally on the Hawai'i and American Samoa pelagic longline fisheries. Using a Bayesian population trend estimation and a "take" model with demographic and fishery stochasticity, we estimated negligible impacts of the Hawai'i shallow-set, deep-set, and the American Samoa longline fishery on the two populations. Unfortunately, other external threats are negatively impacting the trend of western Pacific Leatherbacks, which are likely to go extinct before the end of the century. Our findings are published in two NOAA Technical Memorandum: TM-PIFSC-95 & TM-PIFSC-101.
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Basking Sharks as ocean loggers — Before, during, and after my master's research on the vertical movement of Basking Sharks, 13 sharks were tagged in the Bay of Fundy with time-depth recorders. In addition, these biotelemetry tags recorded ocean temperature. Led by Dr. Heather Koopman and Dr. Andrew Westgate, I performed an analysis exploring how temperatures in the Bay of Fundy had increased from 2008 to 2012 before falling again in 2013. What was particularly concerning, was this warming was throughout the entire water column and indicated extreme changes in the Bay of Fundy over this time frame. Anecdotally, the extra warm summer of 2012 was incredibly different than year's past with warm-water species moving into the bay in large numbers, such as Blue Sharks, Great White Sharks, Sperm Whales, and Ocean Sunfish. In turn, it was a hard year to find classic Bay of Fundy denizens such as North Atlantic Right Whales and Basking Sharks. Fortunately, over a banter week in late August we managed to tag three sharks and saw over 30.
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American Lobster fecundity — My undergraduate thesis contributed to a larger overall investigation of the reproductive investment of American Lobsters (Homarus americanus) in the Bay of Fundy. We measured fecundity (number of eggs), egg energy content, lipid content, and fatty acid profiles. My part was determining the egg energy content which I did using a bomb calorimeter. This scientific instrument injects pure oxygen into a canister containing a sample of lobster eggs and ignites a fire using a small cotton thread. The resulting burn raises the temperature ever so slightly in the surrounding water bath which is measured precisely and converted to calories. Our results, published in 2015, showed that fecundity was declining in American Lobsters from 2008 to 2013 and that very large lobsters were likely undergoing reproductive senescence, investing less into reproduction than smaller lobsters.
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Reproductive energetics of Blue Crabs -- Between my undergraduate and master's projects, I worked on exploring correlates of reproductive investment, egg energy content, lipid content, fatty acid profiles, and zoea size, in Blue Crabs (Callinectes sapidus). We found none of the investment measurements correlated with female size and, instead, found environmental factors to likely be responsible for the variation in reproductive investment. Our results were published in 2013 in the Journal of Crustacean Biology.
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