Rough-toothed dolphins and their prey will lose suitable and protected areas due to climate change

Abstract

Climate change harms marine ecosystems, causing habitat loss and shifts in biodiversity. Impacts on vital species like cetaceans disrupt biological communities, emphasizing the need to understand their spatial distribution for biodiversity conservation. Our study assessed potential changes to suitable habitats in Brazil of a key species, the rough-toothed dolphin (Steno bredanensis), and three common prey species (largehead hairtail, Trichiurus lepturus, Lebranche mullet, Mugil liza, and white mullet, Mugil curema) under two climate change scenarios in 2050 (RCP 4.5, mitigated scenario, and RCP 8.5, nonmitigated scenario). We also examined the extent to which Brazilian Marine Protected Areas (MPAs) safeguard the current and future distribution of the rough-toothed dolphin. MPAs were classified and overlaid with species distribution using the MPA Guide tool. We employed five algorithms (MaxEnt, GLM, GAM, RF, and GBM) to calibrate and test current and future ensemble distribution models. Models performance was evaluated using the Area Under the Curve (AUC) test, resulting in continuous and binary maps for interpretation. Models projected a decrease of 23-28% in suitable areas for rough-toothed dolphins, mainly in North and Northeast Brazil. Mullet species would have a 3-5% decline in their habitat, while largehead hairtail would face a 30-31% habitat loss. Only 5% of the rough-toothed dolphin suitable areas overlap with Brazilian MPAs in the current scenario, and 4.4% in both future scenarios. Regarding MPAs considered effective for conservation (fully and highly), the picture is even worse, with less than 1% overlapping with suitable areas regardless of the scenario. While most MPAs do not cover these areas entirely, they can still help mitigate the impacts of climate change on species. These results guide future conservation efforts and emphasize the need for more effective MPAs.

Full text

25th Biennial Conference on the Biology of Marine Mammals Perth, Western Australia / November 11-15
432
behavior. Survey results suggest that seal
structure density varies annually, however, seals
continue to use the Prudhoe Bay area in winter.
Rough-toothed dolphins and their prey will lose
suitable and protected areas due to climate
change
Guilherme Maricato1, Juliane do Nascimento
Ferreira2, Mariana Vale2, Israel Maciel3, Liliane
Lodi4, Fábio G. Daura-Jorge5, Lucas Milmann6,
Milton Marcondes7, Rodrigo Tardin8
1ECoMAR-UFRJ (Brazil), Brazil, 2Rio de Janeiro,
Brazil, 3Federal Rural University of Rio de Janeiro,
4Whales & Dolphins of Rio de Janeiro Project,
Brazil, 5Universidade Federal de Santa Catarina,
Florianópolis, SC, Brazil, 6Grupo de Estudos de
Mamíferos Aquáticos do Rio Grande do Sul -
GEMARS, Torres, RS, Brazil, 7Instituto Baleia
Jubarte, Caravelas, Bahia, Brazil, 8Department of
Ecology, Universidade do Estado do Rio de
Janeiro, Rio de Janeiro, Brazil
Climate change harms marine ecosystems,
causing habitat loss and shifts in biodiversity.
Impacts on vital species like cetaceans disrupt
biological communities, emphasizing the need to
understand their spatial distribution for biodiversity
conservation. Our study assessed potential
changes to suitable habitats in Brazil of a key
species, the rough-toothed dolphin (Steno
bredanensis), and three common prey species
(largehead hairtail, Trichiurus lepturus, Lebranche
mullet, Mugil liza, and white mullet, Mugil curema)
under two climate change scenarios in 2050 (RCP
4.5, mitigated scenario, and RCP 8.5, non-
mitigated scenario). We also examined the extent
to which Brazilian Marine Protected Areas (MPAs)
safeguard the current and future distribution of the
rough-toothed dolphin. MPAs were classified and
overlaid with species distribution using the MPA
Guide tool. We employed five algorithms (MaxEnt,
GLM, GAM, RF, and GBM) to calibrate and test
current and future ensemble distribution models.
Models performance was evaluated using the Area
Under the Curve (AUC) test, resulting in
continuous and binary maps for interpretation.
Models projected a decrease of 23-28% in
suitable areas for rough-toothed dolphins, mainly
in North and Northeast Brazil. Mullet species
would have a 3-5% decline in their habitat, while
largehead hairtail would face a 30-31% habitat
loss. Only 5% of the rough-toothed dolphin
suitable areas overlap with Brazilian MPAs in the
current scenario, and 4.4% in both future
scenarios. Regarding MPAs considered effective
for conservation (fully and highly), the picture is
even worse, with less than 1% overlapping with
suitable areas regardless of the scenario. While
most MPAs do not cover these areas entirely, they
can still help mitigate the impacts of climate
change on species. These results guide future
conservation efforts and emphasize the need for
more effective MPAs.
Running out of options? Habitat selection of a
coastal delphinid in an anthropogenic
seascape – reconstructing the past and
projecting the future
Leszek Karczmarski1, Scott Y. S. Chui2, Stephen
C.Y. Chan3
1Cetacea Research Institute, Hong Kong, Hong
Kong, Hong Kong S.A.R., China, 2Cetacea
Research Institute, Hong Kong, China, Hong Kong,
Hong Kong, 3Cetacea Research Institute, Hong
Kong, China, Hong Kong, Hong Kong S.A.R.,
China
Habitat selection is a fundamental process that
optimises resource acquisition, minimises
predation risk, and facilitates essential responses
to short-term disturbances and long-term habitat
deterioration. Inshore species such as Indo-
Pacific humpback dolphins are particularly
susceptible to drastic changes in coastal
environment, especially in areas such as Hong
Kong (HK) where coastal urbanization is immense
and rapid. With Resource Selection Function
(RSF) models, we examined decade-long (2010-
2020) dolphin habitat use pattern in HK to identify
its ecological and physio/oceano-graphic
determinants and quantify spatiotemporal
change(s) in response to recent coastal
infrastructure developments. We quantified the
scale and rate of coastal environmental change
since 1970s using satellite data and historic
archives. Applying our RSF findings, we modelled
dolphin occurrence probabilities in the past
(before major coastal transformation) and in the
foreseeable future upon completion of all currently
planned developments. We estimate that ~30%