[MARMAM] New publication on foraging ecology of South American fur seals

[Renan Lima]

Dear MARMAM community,

On behalf of my co-authors, I am pleased to announce that our newest paper
in Aquatic Ecology is now online:

"Segregation of diets by sex and individual in South American fur seals"
RC de Lima, V Franco-Trecu, TS Carrasco, P Inchausti, ER Secchi, S Botta
https://link.springer.com/article/10.1007/s10452-021-09915-9

Abstract
Trophic niche width and individual specialization among marine predators
are often subjected to seasonal constraints. Differences are expected to
arise for sexually dimorphic species exposed to distinct ecological
opportunities, as well as intrinsic differences in physiological abilities
or energetic requirements. We assess seasonal and sexual differences in
isotopic niche overlap and width and analyze inter-individual foraging
variation throughout the year of the South American fur seal (Arctocephalus
australis). We obtained chronologically ordered δ13C and δ15N data from
vibrissae of 25 males and 24 females from southern Brazil and Uruguay.
There were significant differences between sexes for both isotopes with
males showing higher values (δ13C = − 14.5 ± 0.5‰; δ15N = 18.9 ± 1.2‰) than
females (δ13C = − 15.2 ± 0.5‰; δ15N = 17.8 ± 1.2‰), but not among seasons
or years. A very small isotopic niche overlap found between sexes
(1.1–9.5%), with limited seasonal variation, likely resulted from
differences in prey consumption and foraging habitats. Compared to other
seasons, females had a wider isotopic niche in spring. While males showed
seasonal stability in the foraging niche, females showed some small
variation, which is probably influenced by central place foraging. Both
sexes had considerable interindividual variation in estimated dietary
composition and had different proportions of potential prey contribution at
the population level. These findings enlighten the knowledge of South
American fur seal trophic ecology, and how they may seasonally and
spatially shift their foraging strategies according to their distinct life
histories. It ultimately reflects in a small niche partitioning and
possibly low intraspecific competition at the species northernmost area of
occurrence in the western South Atlantic.

Please feel free to contact me via email (renan...@gmail.com) for any
questions or a pdf copy of the paper.

Best regards,
Renan Lima

-- 
MSc Renan Costa de Lima
Doutorando do Programa de Pós-Graduação em Oceanografia Biológica
Laboratório de Ecologia e Conservação da Megafauna Marinha - EcoMega
Instituto de Oceanografia
Universidade Federal do Rio Grande (FURG)
Fone: +55(53)99718994
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[MARMAM] New publication - skin lesion and mortality rates for bottlenose dolphins following a historic flood

[Christina Toms]

Dear Marmam Subscribers,
On behalf of myself and my coauthors, we are pleased to announce a recent
publication in PLOS ONE.

*Citation*:
Toms, C. N., T. Stone, and T. Och.  2021. Skin lesion and mortality rate
estimates for common bottlenose dolphins (Tursiops truncatus) in the
Florida Panhandle following a historic flood. PLOS ONE 16(10): e0257526.
https://doi.org/10.1371/journal.pone.0257526

*Abstract*: Increasing evidence links prolonged freshwater exposure to
adverse health conditions, immune deficiencies, and mortality in
delphinids. Pensacola, Florida, experienced a record-breaking flood event
in April 2014, after which, skin lesions evident of freshwater exposure
were observed on common bottlenose dolphins (*Tursiops truncatus*). Here we
assess the potential consequences of the flood on bottlenose dolphin health
and mortality. Data from an ongoing study were used to evaluate the
relationship between skin lesions (progression, prevalence, and extent) and
the flood with respect to changing environmental conditions (salinity).
Annual stranding records (2012–2016) from Alabama to the eastern Florida
Panhandle were used as an indicator of dolphin health to test the
hypothesis that the flood event resulted in increased annual mortality
rates. Although salinities remained low for several months, results suggest
that there was not the widespread skin lesion outbreak anticipated. Of the
333 unique individuals detected only 20% were seen with skin lesions. There
was a significant increase in the proportion of dolphins seen post-flood
with lesion extent above background levels (≥ 5%; *p* = 0.001), however,
there were only 11 cases with lesion extent greater than 20%. Skin lesion
prevalence increased overall following the flood (*p* < 0.001), but
pairwise comparisons revealed a delayed response with significant increases
not detected until the following fall (*p* = 0.01), several months after
salinities returned to expected levels. Regression modeling revealed no
significant effects of year, region, or year x region on mortality rates,
except in Alabama, where increased mortality rates were likely due to
residual impacts from the Deepwater Horizon Oil Spill. This study takes
advantage of a natural experiment, highlighting how little is understood
about the conditions in which prolonged freshwater exposure leads to
negative impacts on dolphin health.

The article and supplementary materials are available as open access here:
https://doi.org/10.1371/journal.pone.0257526
Or you can request a copy from me at: ct...@mote.org.

Cheers,
Christina Toms
PhD, Postdoctoral Scientist
Chicago Zoological Society's Sarasota Dolphin Research Program
Cell: 808-990-1931
ct...@mote.org
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[MARMAM] New publication on bottlenose dolphin behavioral responses to a flood event

[Christina Toms]

Dear Marmam Subscribers,
On behalf of myself and my coauthors, we are pleased to announce a recent
publication in the Journal of Zoological and Botanical Gardens.

Citation:
McBride-Kebert, S. and C. N. Toms.  2021.  Common bottlenose
dolphin, Tursiops truncatus, behavioral response to a record-breaking flood
event in Pensacola Bay, Florida. Journal of Zoological and Botanical
Gardens, 2(3):351-369

Abstract: Common bottlenose dolphins, Tursiops truncatus, can suffer health
complications from prolonged freshwater exposure; however, little is known
about how dolphins behaviorally respond to flood events. We investigated
whether dolphins mitigated their freshwater exposure by moving south
towards the estuary mouth and/or towards deeper areas with higher
salinities in response to a record-breaking flood in Pensacola Bay,
Florida. In total, 144 dolphin groups observed during 45 population dynamic
surveys were analyzed across two flood-impacted sampling sessions and
their respective seasonal control sessions. Kernel density estimates
demonstrated southern movement towards the estuary mouth during
flood-impacted sessions, but this distribution change was limited. Species
distribution models showed that dolphins did not move to deeper areas after
the flood and dolphin distribution was not substantially altered by
flood-induced salinity changes. The estuary system exhibits strongly
stratified waters with broad salinity ranges even during the flood.
Dolphins may have mitigated the severity of freshwater exposure by
capitalizing on these stratified areas as they continued to use habitat
affected by the flood. A lack of avoidance of low salinity could result in
this dolphin population being at greater risk for health problems, which
should be considered in future population management and conservation.

The article and supplementary materials can be accessed via
https://doi.org/10.3390/jzbg2030025, or you can email Shauna
McBride-Kebert, the corresponding author, at  smcbridekeb...@gmail.com.

Cheers,
Christina Toms
--
PhD, Postdoctoral Scientist
Chicago Zoological Society's Sarasota Dolphin Research Program
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[MARMAM] New publication on the effects of multiple red tide blooms on bottlenose dolphin prey

[Christina Toms]

Dear Marmam Subscribers,
On behalf of myself and my coauthors, we are pleased to announce a recent
publication in Frontiers in Marine Science.

Citation:
Berens McCabe, E. J., R. S. Wells, C. Toms, A. Barleycorn, K. A. Wilkinson,
and V. Palubok. 2021. Effects of multiple Karenia brevis red tide blooms on
a common bottlenose dolphin (Tursiops truncatus) prey fish assemblage:
Patterns of resistance and resilience in Sarasota Bay, Florida. Frontiers
in Marine Science, Marine Conservation and Sustainability, Special Topic:
The dolphins of Sarasota Bay: Lessons from 50 years of research and
conservation, 8:74. DOI: 10.3389/fmars.2021.74

Abstract: Red tide blooms caused by the toxic dinoflagellate Karenia brevis
are natural disturbance events that occur regularly along Florida’s west
coast, often resulting in massive fish kills and marine mammal, seabird,
and sea turtle mortalities. Limited prior work on the ecological effects of
red tides suggests they play an important role in structuring ecosystem
dynamics and regulating communities, however specific effects on prey
populations and potential alterations to predator-prey interactions are
unknown. We surveyed the prey fish assemblage of a top marine predator, the
common bottlenose dolphin (Tursiops truncatus), in shallow seagrass habitat
in Sarasota Bay, Florida, during 2004–2019, collecting data on prey
density, species composition, K. brevis cell densities, and environmental
variables. Across eight distinct red tide bloom events, resistance,
resilience, and the ecological effects on the prey assemblage varied
depending on bloom intensity, season, and frequency. Prey assemblage
structure showed significant and distinct short-term shifts during blooms
independent of the normal seasonal shifts in prey structure seen during
non-bloom conditions. Canonical correspondence analysis indicated a strong
influence of K. brevis density on assemblage structure. Blooms occurring
primarily in the summer were associated with less initial prey resistance
and higher than average annual catch per unit effort (CPUE) 1–3 years
following bloom cessation, with bloom frequency prolonging the time needed
to reach higher than average annual CPUE. Regardless of season, recovery to
pre-bloom prey abundances occurred within 1 year. Sample-based rarefaction
and extrapolation indicated significant differences in prey diversity among
summer bloom events. This study is a first step in identifying differences
in resistance, resilience, and the ecological effects of multiple red tide
bloom events of various temporal scales and intensity on a dolphin prey
assemblage. Improved understanding of the influence of red tides on
estuarine structural dynamics and function can better inform management,
and potentially guide mitigation efforts post-bloom.

The article and supplementary materials can be accessed via
https://www.frontiersin.org/articles/10.3389/fmars.2021.74/full
, or you can email Elizabeth Berens
McCabe, the corresponding author, at emcc...@mote.org.


Cheers,
Christina Toms
--
PhD, Postdoctoral Scientist
Chicago Zoological Society's Sarasota Dolphin Research Program
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