[Eoas-seminar] FW: Cheston Peterson - Biology Doctoral Defense - July 12th

Tue Jul 6 10:55:47 EDT 2021

I am excited to announce Cheston Peterson will be defending his doctoral dissertation "MIGRATION, HABITAT USE, AND PREDATOR-PREY DYNAMICS OF COASTAL SHARKS IN THE NORTHEAST GULF OF MEXICO" on Monday, July 12th. His seminar will begin at 2PM via the Zoom link and password below. Please join us to hear about Cheston's work in Apalachicola Bay and Florida's Big Bend!

Dean Grubbs is inviting you to a scheduled Zoom meeting.

Topic: Cheston Peterson - Doctoral Defense Seminar
Time: Jul 12, 2021 02:00 PM Eastern Time (US and Canada)

Join Zoom Meeting
https://fsu.zoom.us/j/92220842561?pwd=TVdHRVM2eWU3MlM2aERKT1kzWFpGZz09

Meeting ID: 922 2084 2561
Passcode: 073164

Abstract

Drivers of animal movement, including abiotic factors such as environmental conditions or climate and biotic factors such as species interactions and reproduction, are classic topics in ecology and relevant to both basic and applied scientific questions. Understanding phenomena such as seasonal migrations are important in fisheries management, and describing habitat use and ecological interactions is a primary goal in fisheries ecology as the field moves toward holistic, ecosystem-based approaches. Here I present the results of research investigating the drivers of movement in coastal sharks, from scales of seasonal migrations and temporal patterns of abundance to fine-scale movement of a single species as it relates to the distribution and density of its prey and predators.
I used a 10 year data set of long-term fishery-independent gillnet and longline surveys to explore the effects of abiotic variables on temporal patterns of community structure of fishes and correlates of migration at two seagrass shoals off the FSU Coastal and Marine Laboratory. I examined community structure using non-metric multidimensional scaling (NMDS) with environmental fitting, compared temporal community structure using permutational multivariate analysis of variance (PERMANOVA) of monthly catch rates in both gear types, and tested for cyclicity in community structure. I also used generalized additive models (GAMs) to explore the effects of environmental variables (e.g. temperature and photoperiod) on immigration and emigration phases of dominant taxa. I found strong seasonality and cyclicity in assemblages captured by both gear types, with depauperate winter communities and diverse assemblages in warmer month - especially late summer and fall. My results suggest temperature may determine the timing of immigration and duration of the residency period of dominant taxa, including the juvenile life stages of some coastal sharks, but photoperiod may cue immigration and emigration in adults when the purpose of those migrations includes predicable reproductive functions (e.g. parturition). I found evidence of partial migration in juvenile life stages of some coastal sharks, and hypothesize that rising temperatures due to climate change may have variable effects on residency patterns over ontogeny.
I conducted similar fishery-independent sampling in Apalachicola Bay from 2018 to 2020 during the summer to study habitat overlap in multiple life stages of a group of sympatric coastal sharks. I also used data shared with me by the Florida Fish and Wildlife Conservation Commission to explore the relationship of habitat use in coastal sharks to prey distribution and density. My analyses suggested this relationship may vary among species and life stage, as predation risk or environmental tolerances may drive habitat use in early life stages of some species. Prey distribution may be more important for dietary specialists. Interestingly, habitat use of species life stages with increasing reported dietary overlap appeared to converge.
Using acoustic telemetry, I described movement and habitat use of bull sharks (Carcharhinus leucas), bonnetheads (Sphyrna tiburo), and gafftopsail catfish (Bagre marinus) in Apalachicola Bay and St. George Sound. I used linear mixed models (LMM) to integrate the tracking information with blue crab (Calinectes sapidus) density data from the same fishery-independent surveys conducted by FWC to explore the predator-prey dynamics of blue crabs, bonnetheads, and bull sharks. All three fishes were resident throughout the summer and were philopatric. Bull sharks used more of the habitat than bonnetheads or gafftopsail catfish. Bonnetheads mainly used seagrass habitats, while gafftopsail catfish used muddy habitats around freshwater inputs. There were relationships of size and the proportion of the acoustic array each species used, with a positive correlation of size and space used in both species of sharks and a negative correlation in gafftopsail catfish, which may be driven my differences between sexes. Bonnetheads were not detected in habitats where blue crabs were most dense, but the probability of bull shark presence was highest. Results of the LMM analyses suggested a significant negative relationship of bonnethead habitat use and bull shark presence probability, as well as a significant negative relationship of the interaction of bull shark presence and salinity (bull shark presence probability was highest at sites with the lowest average salinities). These results suggest habitat use in bonnetheads may follow predictions of optimal foraging theory and the ideal free distribution under the constraint of predation risk, which may be informative in understanding the roles of predation and prey availability in the habitat use of marine mesopredators.

R. Dean Grubbs, Ph.D.
Associate Director of Research
Full Research Faculty
Florida State University Coastal and Marine Laboratory
3618 Hwy 98
St. Teresa, FL 32358
Office: 850-645-3494
email: dgrubbs2 at fsu.edu<mailto:dgrubbs2 at fsu.edu>
https://marinelab.fsu.edu/people/faculty/dean-grubbs/
https://jhupbooks.press.jhu.edu/title/shark-biology-and-conservation<https://urldefense.com/v3/__https:/jhupbooks.press.jhu.edu/title/shark-biology-and-conservation__;!!PhOWcWs!i3eH2c4l0ETSxx3oaGjZpt8gEiL4O9QHTY1v-AfGK5Hjqdu_H1jRxV1pQDWt-H0n$>
[cid:image001.jpg at 01D771D2.131DF440]

From: Dean Grubbs
Sent: Monday, June 21, 2021 6:27 PM
To: Jen Kennedy <jkennedy at bio.fsu.edu<mailto:jkennedy at bio.fsu.edu>>
Subject: Johanna Imhoff Doctoral Defense - July 2nd

Hi Jen. Is it possible to add this dissertation defense to the Bionotes?  Thank you.

Johanna Imhoff will be defending her doctoral dissertation "MERCURY CONTAMINATION AND ITS RELATION TO TROPHIC ECOLOGY AND ANTHROPOGENIC POLLUTION IN COASTAL AND DEEP SEA SHARK COMMUNITIES"

Topic: Johanna Imhoff - Doctoral Defense Seminar
Time: Jul 2, 2021 11:00 AM Eastern Time (US and Canada)

Join Zoom Meeting
https://fsu.zoom.us/j/99237614122?pwd=ZUFpOHhQWExtNCtPdGlqbmRZMGZ6dz09

Meeting ID: 992 3761 4122
Passcode: 210219

Abstract

The effect of changing anthropogenic mercury emissions on marine wildlife is of broad interest. Methylmercury can cause reproductive and neurological damage and biomagnifies in food webs. Mercury availability in the Pacific Ocean has been increasing and therefore could be expected to increase in marine fishes. In Hawaii, tunas have shown increases proportional to increasing oceanic mercury over several decades. Historical data on shark muscle mercury is also available for Hawaii, presenting an opportunity for comparison in a long-lived upper trophic level cartilaginous fish. Muscle samples were opportunistically collected from sandbar sharks in 2003-2005 for mercury analysis and comparison with published data from 1971. Mercury contamination was similar in sandbar sharks collected in the two time periods, in contrast to tunas. Sandbar sharks collected in 2003-2005 had a higher observed rate of stillborn embryos than previously documented. Since mercury can cause reproductive toxicity, muscle mercury contamination was quantified in available sandbar shark embryos. Contamination was similar in stillborn and viable embryos, indicating that mercury toxicity was likely not the cause of embryo death. Mercury does not appear to have changed in sandbar sharks and the observed frequency of stillborn sharks does not appear to be due to increasing mercury emissions over three decades.
Deep sea chondricthyans comprise nearly half of global chondrichthyan fauna but have been researched relatively less than their coastal and pelagic counterparts. As long-lived mesopredators and apex predators in their food webs, deep sea shark can bioaccumulate high levels of mercury in their tissues. Mercury was measured in six species of relatively abundant deep sea sharks in the GOM that inhabit the continental shelf edge to the continental slope. To attempt to address whether the Deepwater Horizon oil spill indirectly affected bioavailability of methylmercury in GOM, the same or closely related species were also analyzed from regions not affected by the oil spill. Overall, Mustelus sinusmexicanus had the lowest mercury among the GOM sharks analyzed, and Squalus clarkae had the highest. The remaining four species were similar to one another in their mercury contamination. Regional comparisons revealed similar contamination between M. canis canis in the GOM and M. canis insularis in Eleuthera. Eleuthera S. cubensis had similar mercury contamination to GOM S. clarkae, to which they were closer in size than GOM S. cubensis. GOM Centrophorus granulosus had higher mercury contamination than Virginia C. granulosus but this was only marginally significant. There was a slight and non-significant increase in mercury with depth in the GOM. M. canis caught on the east side of De Soto Canyon had significantly higher mercury than those caught on the west side of De Soto Canyon. The opposite pattern was seen in C. uyato, with higher mercury concentrations on the west side of the canyon, but these results may be strongly influenced by sample size for both species.
Since mercury bioaccumulation in organisms is tightly linked to biomagnification, mercury studies are often coupled with trophic ecology studies using light stable isotopes as tracers. Since animals vary in the quantity of lipids that they store in their tissues, and since the presence of lipids can affect δ13C signatures, it is necessary to explore these effects to correctly interpret δ13C results. A particular challenge for chondrichthyan fishes is that they store isotopically light nitrogenous wastes in their tissues for osmoregulation, and this can affect the interpretation of δ15N, sometimes leading to inaccurate interpretation of trophic level. The effects of lipids and nitrogenous wastes on stable isotope analysis of chondrichthyan fishes has been an important aspect of trophic ecology research on this group. The effects of lipid extraction, urea extraction, and combined lipid and urea extraction compared to bulk tissue were tested on a coastal and deep sea teleost and a coastal and deep sea elasmobranch as representatives that might be included in coast to deep sea food web studies. Since mercury analysis requires the same initial muscle tissue handling steps as stable isotope analysis (SIA), the effects of treatments on mercury quantification were also tested. The results suggest that chemical lipid extraction is necessary for accurate interpretation of SIA results in coastal and deep sea teleosts and elasmobranchs and that urea was extracted sufficiently during the lipid extraction, therefore additional urea extraction steps are not necessary. Additionally, it may be possible for researchers to use leftover treated muscle from SIA to obtain accurate mercury results. Future research on trophic ecology including SIA informed by this research may help to provide context for mercury findings in GOM deep sea sharks.

R. Dean Grubbs, Ph.D.
Associate Director of Research
Full Research Faculty
Florida State University Coastal and Marine Laboratory
3618 Hwy 98
St. Teresa, FL 32358
Office: 850-645-3494
email: dgrubbs2 at fsu.edu<mailto:dgrubbs2 at fsu.edu>
https://marinelab.fsu.edu/people/faculty/dean-grubbs/
https://jhupbooks.press.jhu.edu/title/shark-biology-and-conservation<https://urldefense.com/v3/__https:/jhupbooks.press.jhu.edu/title/shark-biology-and-conservation__;!!PhOWcWs!i3eH2c4l0ETSxx3oaGjZpt8gEiL4O9QHTY1v-AfGK5Hjqdu_H1jRxV1pQDWt-H0n$>
[cid:image004.jpg at 01D771D2.131DF440]

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.fsu.edu/pipermail/eoas-seminar/attachments/20210706/28cf1c43/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 32194 bytes
Desc: image001.jpg
URL: <http://lists.fsu.edu/pipermail/eoas-seminar/attachments/20210706/28cf1c43/attachment.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image004.jpg
Type: image/jpeg
Size: 30954 bytes
Desc: image004.jpg
URL: <http://lists.fsu.edu/pipermail/eoas-seminar/attachments/20210706/28cf1c43/attachment-0001.jpg>