Conference Presentations by Mduduzi Seakamela
Oceans and Coasts Annual Science Report, 2021
Two long-finned pilot whale Globicephala melas adults were opportunistically in the offshore w... more Two long-finned pilot whale Globicephala melas adults were opportunistically in the offshore waters south-west of Cape Point in South Africa. This one pager gives a short report on their movements that were almost exclusively along the continental shelf.
Oceans and Coasts Annual Science Report, 2021
A Cape fur seal unusual mortality event was recorded in 2021 along the west coast of South Africa... more A Cape fur seal unusual mortality event was recorded in 2021 along the west coast of South Africa. This one pager is a short account of that event including results of tests that were conducted by the State Vet.
In this report card, DEA provides brief
synopses of some results of monitoring a
suite of variabl... more In this report card, DEA provides brief
synopses of some results of monitoring a
suite of variables that range from physical
and chemical ocean properties to plankton
and other biological attributes, which have
been chosen as potentially useful
indicators of change, health and
management of South Africa’s marine and
coastal systems. On account of the brief
and stand-alone nature of the individual
reports, it has not been attempted to
provide an executive summary, which
would have resulted in considerable
duplication. Rather the reader will be able
to cast her/his eye across the broad
diversity of subject matters and rapidly
select those that are of particular interest to
the individual concerned. It should be
borne in mind that the topics that follow
are by no means an exhaustive compilation
of work that is undertaken by the
Department and collaborators but rather a
selection of some material that may be of
interest. This report is an annual
compilation of some highligted areas of
work. The 2015-16 Report Card does
however start with a brief description of
A dedicated dual-vessel cetacean survey cruise targeted humpback whales (Megaptera novaeangliae) ... more A dedicated dual-vessel cetacean survey cruise targeted humpback whales (Megaptera novaeangliae) off the
west coast of South Africa between 28 October 2014 and 8 November 2014. The overarching objective of the
cruise was the determination of the distribution of whales between Dassen Island (33° 25' 34.32" S, 18° 5'
20.04" E) and Groenriviermond (30° 51' 53.78" S, 17° 34' 40.52" E) using both vessel-based observations and
satellite telemetry. The study area incorporated areas of known humpback whale low-latitude feeding
aggregations. The survey followed an adaptive systematic parallel line-transect design within the 150m depth
contour limit. Predetermined parallel transect-survey lines were between 15 and 25 nmiles apart while
oceanographic process stations were betwenn 5 and 20 nmiles apart. Oceanographic sampling and cetacean
observations were conducted on board the RV Algoa of Department of Environmental Affairs while whale
targeted components such as tagging photo-identification and genetic sampling were conducted from the FRS
Ellen Khuzwayo provided by Department of Agriculture, Forestry and Fisheries. Three hundred and fourteen
Conductivity, Temperature, and Depth (CTD) samples and 50 Multinet samples were collected from 50
oceanographic stations, whilst the partial pressure of carbon dioxide (pCO2) was measured using an autonomous
underway measuring system. A total of 62 sightings of an estimated 80 Humpback was sighted during the
research effort on the survey. Other cetaceans sighted are dusky dolphins (14 sightings, 148 individuals) and
heaviside’s dolphins (8 sightings, 12 individuals). Satellite-linked tags were deployed on 8 adult humpback
whales and movements monitored over a three month’s period. The tagged whales locally moved between 3
known upwelling areas of southern Benguela system. During the southward migration, all the tagged whales
followed a similar and parallel migratory route towards Bouvet Island from where they dispersed.
Papers by Mduduzi Seakamela
Journal of the Acoustical Society of America, Apr 1, 2018
Humpback whales (Megaptera novaeangliae) are well known for their complex song which is culturall... more Humpback whales (Megaptera novaeangliae) are well known for their complex song which is culturally transmitted and produced by males. However, the function of singing behavior remains poorly understood. Song was observed from 57 min of acoustic recording in the presence of feeding humpback whales aggregated in the nearshore waters on the west coast of South Africa. The structural organization of the song components, lack of overlap between song units, and consistency in relative received level suggest the song was produced by one "singer." The unusual timing and location of song production adds further evidence of plasticity in song production.
Ecology and Evolution
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Scientific Reports
The cosmopolitan distribution of humpback whales (Megaptera novaeangliae) is largely driven by mi... more The cosmopolitan distribution of humpback whales (Megaptera novaeangliae) is largely driven by migrations between winter low-latitude breeding grounds and summer high-latitude feeding grounds. Southern Hemisphere humpback whales faced intensive exploitation during the whaling eras and recently show evidence of population recovery. Gene flow and shared song indicate overlap between the western (A) and eastern (B1, B2) Breeding Stocks in the South Atlantic and Indian Oceans (C1). Here, we investigated photo-identification evidence of population interchange using images of individuals photographed during boat-based tourism and research in Brazil and South Africa from 1989 to 2022. Fluke images were uploaded to Happywhale, a global digital database for marine mammal identification. Six whales were recaptured between countries from 2002 to 2021 with resighting intervals ranging from 0.76 to 12.92 years. Four whales originally photographed off Abrolhos Bank, Brazil were photographed off t...
Information on resource use and trophic dynamics of marine predators is important
for understandi... more Information on resource use and trophic dynamics of marine predators is important
for understanding their role in ecosystem functioning and predicting population-level
responses to environmental change. Where separate populations experience different
local environmental conditions, geographic variability in their foraging ecology is
often expected. Within populations, individuals also vary in morphology, physiology,
and experience, resulting in specialization in resource use. In this context, isotopic
compositions of incrementally grown tissues such as keratinous hairs offer a valuable
opportunity to study long-term
variation in resource and habitat use. We investigated
the trophic ecology of female Cape fur seals (Arctocephalus pusillus pusillus) using carbon
and nitrogen isotopic compositions of serially sampled whiskers collected at four
breeding sites along the coast of South Africa. Drawing on over 900 isotopic measurements,
we assessed geographic variability in isotopic niche width between colonies
and the degree of individual specialization. We found slight, but clear geographic differences
in isotopic ratios and isotopic niche widths, seemingly related to ecological
setting, with niche widths being proportional to the area of available shelf and shelf-slope
habitat surrounding the colony. We further identified periodic oscillations in
isotopic ratios, which likely reflect temporal patterns in foraging distribution and prey
type, linked to shifts in the availability of prey resources and their interaction with
constraints on individual females throughout their breeding cycle. Finally, individual
specialization indices revealed that each of the study populations contain specialist
individuals that utilize only a small subset of the total population niche width. The
degree of individual specialization was, however, not consistent across colonies and
may reflect an interactive influence between density-dependent
effects and habitat
heterogeneity. Overall, this study provides important information on the trophic ecology
of Cape fur seals breeding in South Africa and highlights the need to consider
geographic and individual variability when assessing the foraging ecology of marine
predators.
Scientific Reports, 2023
The cosmopolitan distribution of humpback whales (Megaptera novaeangliae) is largely driven
by mi... more The cosmopolitan distribution of humpback whales (Megaptera novaeangliae) is largely driven
by migrations between winter low-latitude breeding grounds and summer high-latitude feeding
grounds. Southern Hemisphere humpback whales faced intensive exploitation during the whaling
eras and recently show evidence of population recovery. Gene flow and shared song indicate overlap
between the western (A) and eastern (B1, B2) Breeding Stocks in the South Atlantic and Indian
Oceans (C1). Here, we investigated photo-identification evidence of population interchange using
images of individuals photographed during boat-based tourism and research in Brazil and South
Africa from 1989 to 2022. Fluke images were uploaded to Happywhale, a global digital database for
marine mammal identification. Six whales were recaptured between countries from 2002 to 2021
with resighting intervals ranging from 0.76 to 12.92 years. Four whales originally photographed off
Abrolhos Bank, Brazil were photographed off the Western Cape, South Africa (feeding grounds for B2).
Two whales originally photographed off the Western Cape were photographed off Brazil, one traveling
to the Eastern Cape in the Southwestern Indian Ocean (a migration corridor for C1) before migrating
westward to Brazil. These findings photographically confirm interchange of humpback whales across
the South Atlantic and Indian Oceans and the importance of international collaboration to understand
population boundaries.
J. Cetacean Res. Manage.
The southern right whale (Eubalaena australis; SRW) population in South Africa’s coastal waters h... more The southern right whale (Eubalaena australis; SRW) population in South Africa’s coastal waters has experienced marked changes since 2009, including altered feeding and migration behaviour, and decreased calving success. At the same time, anthropogenic activities in the area have increased. Based on this, an update on SRW mortalities and related anthropogenic factors is warranted. Building on the published information of Best et al. (2001a), data were collated on all SRW mortalities as well as non‐fatal ship‐strikes and entanglements along the South African coast between 1999 and 2019. A total of 97 SRW mortalities were recorded, including three that did not result in a stranding, of which the majority were classified as calves of the year. Most of these occurred on the Western Cape coast between the months of July to November, coinciding with the seasonal presence of the species in South African coastal waters. Eleven of these mortalities could be attributed to ship‐strikes whereas...
Polar Biology
Blue whales are rarely sighted off the coasts of South Africa due to their low numbers and offsho... more Blue whales are rarely sighted off the coasts of South Africa due to their low numbers and offshore habitat preference. Visual observations to search for marine mammals were conducted onboard a platform of opportunity during the Integrated Ecosystems Programme survey in November 2019. A cow–calf pair of blue whales Balaenoptera musculus was sighted offshore Kleinzee (30°05′02.4" S, 14°24′53.2" E) at a water depth of 1670 m on the west coast of South Africa in the southern Benguela Current System. The pair was identified as Antarctic blue whales B. m. intermedia based on the size of the cow (~ 29 m), “torpedo-shaped” body of the cow, known distribution ranges and recent acoustic data showing that pygmy blue whales B. m. brevicauda do not occur in these waters. The calf was likely born in the Benguela ecosystem given its relatively small size. This is the first sighting of Antarctic blue whale cow–calf pair in South African waters post whaling, indicating that animals might ...
<p>Dedicated observations of “super-groups” encountered on cruises in the southern Benguela... more <p>Dedicated observations of “super-groups” encountered on cruises in the southern Benguela in 2011, 2014 and 2015.</p
<p>An aerial incidental observation of a “super-group” (Observation 3 <a href="http... more <p>An aerial incidental observation of a “super-group” (Observation 3 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172002#pone.0172002.t002" target="_blank">Table 2</a>, circled in background) within a widely distributed loosely-spaced aggregation of smaller feeding sub-groups (foreground) off Dassen Island.</p
This file contains supplimentary methodology as referenced in the main text.
Biology Letters, 2022
Predators can impact prey via predation or risk effects, which can initiate trophic cascades. Giv... more Predators can impact prey via predation or risk effects, which can initiate trophic cascades. Given widespread population declines of apex predators, understanding and predicting the associated ecological consequences is a priority. When predation risk is relatively unpredictable or uncontrollable by prey, the loss of predators is hypothesized to release prey from stress; however, there are few tests of this hypothesis in the wild. A well-studied predator–prey system between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) in False Bay, South Africa, has previously demonstrated elevated faecal glucocorticoid metabolite concentrations (fGCMs) in seals exposed to high levels of predation risk from white sharks. A recent decline and disappearance of white sharks from the system has coincided with a pronounced decrease in seal fGCM concentrations. Seals have concurrently been rafting further from shore and over deeper water, a behaviour that wou...
This report provides stranding trends of whales (genus Kogia) for the areas between Strandfontein... more This report provides stranding trends of whales (genus Kogia) for the areas between Strandfontein on the West Coast and Grootbrak River on the South Coast of South Africa between 2010 and 2020 for the benefit of Municipalities, Scientists and Managers. The report is a product of Department of Environment, Forestry and Fisheries (DEFF) marine mammal health monitoring efforts under the title: "Long term monitoring of the effects of environmental changes and humans activities on the health and conservation of marine mammals (i.e. Strandings, Bycatch, Marine Debris, Fisheries Interactions, Pollution, etc.)"
Uploads
Conference Presentations by Mduduzi Seakamela
synopses of some results of monitoring a
suite of variables that range from physical
and chemical ocean properties to plankton
and other biological attributes, which have
been chosen as potentially useful
indicators of change, health and
management of South Africa’s marine and
coastal systems. On account of the brief
and stand-alone nature of the individual
reports, it has not been attempted to
provide an executive summary, which
would have resulted in considerable
duplication. Rather the reader will be able
to cast her/his eye across the broad
diversity of subject matters and rapidly
select those that are of particular interest to
the individual concerned. It should be
borne in mind that the topics that follow
are by no means an exhaustive compilation
of work that is undertaken by the
Department and collaborators but rather a
selection of some material that may be of
interest. This report is an annual
compilation of some highligted areas of
work. The 2015-16 Report Card does
however start with a brief description of
west coast of South Africa between 28 October 2014 and 8 November 2014. The overarching objective of the
cruise was the determination of the distribution of whales between Dassen Island (33° 25' 34.32" S, 18° 5'
20.04" E) and Groenriviermond (30° 51' 53.78" S, 17° 34' 40.52" E) using both vessel-based observations and
satellite telemetry. The study area incorporated areas of known humpback whale low-latitude feeding
aggregations. The survey followed an adaptive systematic parallel line-transect design within the 150m depth
contour limit. Predetermined parallel transect-survey lines were between 15 and 25 nmiles apart while
oceanographic process stations were betwenn 5 and 20 nmiles apart. Oceanographic sampling and cetacean
observations were conducted on board the RV Algoa of Department of Environmental Affairs while whale
targeted components such as tagging photo-identification and genetic sampling were conducted from the FRS
Ellen Khuzwayo provided by Department of Agriculture, Forestry and Fisheries. Three hundred and fourteen
Conductivity, Temperature, and Depth (CTD) samples and 50 Multinet samples were collected from 50
oceanographic stations, whilst the partial pressure of carbon dioxide (pCO2) was measured using an autonomous
underway measuring system. A total of 62 sightings of an estimated 80 Humpback was sighted during the
research effort on the survey. Other cetaceans sighted are dusky dolphins (14 sightings, 148 individuals) and
heaviside’s dolphins (8 sightings, 12 individuals). Satellite-linked tags were deployed on 8 adult humpback
whales and movements monitored over a three month’s period. The tagged whales locally moved between 3
known upwelling areas of southern Benguela system. During the southward migration, all the tagged whales
followed a similar and parallel migratory route towards Bouvet Island from where they dispersed.
Papers by Mduduzi Seakamela
for understanding their role in ecosystem functioning and predicting population-level
responses to environmental change. Where separate populations experience different
local environmental conditions, geographic variability in their foraging ecology is
often expected. Within populations, individuals also vary in morphology, physiology,
and experience, resulting in specialization in resource use. In this context, isotopic
compositions of incrementally grown tissues such as keratinous hairs offer a valuable
opportunity to study long-term
variation in resource and habitat use. We investigated
the trophic ecology of female Cape fur seals (Arctocephalus pusillus pusillus) using carbon
and nitrogen isotopic compositions of serially sampled whiskers collected at four
breeding sites along the coast of South Africa. Drawing on over 900 isotopic measurements,
we assessed geographic variability in isotopic niche width between colonies
and the degree of individual specialization. We found slight, but clear geographic differences
in isotopic ratios and isotopic niche widths, seemingly related to ecological
setting, with niche widths being proportional to the area of available shelf and shelf-slope
habitat surrounding the colony. We further identified periodic oscillations in
isotopic ratios, which likely reflect temporal patterns in foraging distribution and prey
type, linked to shifts in the availability of prey resources and their interaction with
constraints on individual females throughout their breeding cycle. Finally, individual
specialization indices revealed that each of the study populations contain specialist
individuals that utilize only a small subset of the total population niche width. The
degree of individual specialization was, however, not consistent across colonies and
may reflect an interactive influence between density-dependent
effects and habitat
heterogeneity. Overall, this study provides important information on the trophic ecology
of Cape fur seals breeding in South Africa and highlights the need to consider
geographic and individual variability when assessing the foraging ecology of marine
predators.
by migrations between winter low-latitude breeding grounds and summer high-latitude feeding
grounds. Southern Hemisphere humpback whales faced intensive exploitation during the whaling
eras and recently show evidence of population recovery. Gene flow and shared song indicate overlap
between the western (A) and eastern (B1, B2) Breeding Stocks in the South Atlantic and Indian
Oceans (C1). Here, we investigated photo-identification evidence of population interchange using
images of individuals photographed during boat-based tourism and research in Brazil and South
Africa from 1989 to 2022. Fluke images were uploaded to Happywhale, a global digital database for
marine mammal identification. Six whales were recaptured between countries from 2002 to 2021
with resighting intervals ranging from 0.76 to 12.92 years. Four whales originally photographed off
Abrolhos Bank, Brazil were photographed off the Western Cape, South Africa (feeding grounds for B2).
Two whales originally photographed off the Western Cape were photographed off Brazil, one traveling
to the Eastern Cape in the Southwestern Indian Ocean (a migration corridor for C1) before migrating
westward to Brazil. These findings photographically confirm interchange of humpback whales across
the South Atlantic and Indian Oceans and the importance of international collaboration to understand
population boundaries.
synopses of some results of monitoring a
suite of variables that range from physical
and chemical ocean properties to plankton
and other biological attributes, which have
been chosen as potentially useful
indicators of change, health and
management of South Africa’s marine and
coastal systems. On account of the brief
and stand-alone nature of the individual
reports, it has not been attempted to
provide an executive summary, which
would have resulted in considerable
duplication. Rather the reader will be able
to cast her/his eye across the broad
diversity of subject matters and rapidly
select those that are of particular interest to
the individual concerned. It should be
borne in mind that the topics that follow
are by no means an exhaustive compilation
of work that is undertaken by the
Department and collaborators but rather a
selection of some material that may be of
interest. This report is an annual
compilation of some highligted areas of
work. The 2015-16 Report Card does
however start with a brief description of
west coast of South Africa between 28 October 2014 and 8 November 2014. The overarching objective of the
cruise was the determination of the distribution of whales between Dassen Island (33° 25' 34.32" S, 18° 5'
20.04" E) and Groenriviermond (30° 51' 53.78" S, 17° 34' 40.52" E) using both vessel-based observations and
satellite telemetry. The study area incorporated areas of known humpback whale low-latitude feeding
aggregations. The survey followed an adaptive systematic parallel line-transect design within the 150m depth
contour limit. Predetermined parallel transect-survey lines were between 15 and 25 nmiles apart while
oceanographic process stations were betwenn 5 and 20 nmiles apart. Oceanographic sampling and cetacean
observations were conducted on board the RV Algoa of Department of Environmental Affairs while whale
targeted components such as tagging photo-identification and genetic sampling were conducted from the FRS
Ellen Khuzwayo provided by Department of Agriculture, Forestry and Fisheries. Three hundred and fourteen
Conductivity, Temperature, and Depth (CTD) samples and 50 Multinet samples were collected from 50
oceanographic stations, whilst the partial pressure of carbon dioxide (pCO2) was measured using an autonomous
underway measuring system. A total of 62 sightings of an estimated 80 Humpback was sighted during the
research effort on the survey. Other cetaceans sighted are dusky dolphins (14 sightings, 148 individuals) and
heaviside’s dolphins (8 sightings, 12 individuals). Satellite-linked tags were deployed on 8 adult humpback
whales and movements monitored over a three month’s period. The tagged whales locally moved between 3
known upwelling areas of southern Benguela system. During the southward migration, all the tagged whales
followed a similar and parallel migratory route towards Bouvet Island from where they dispersed.
for understanding their role in ecosystem functioning and predicting population-level
responses to environmental change. Where separate populations experience different
local environmental conditions, geographic variability in their foraging ecology is
often expected. Within populations, individuals also vary in morphology, physiology,
and experience, resulting in specialization in resource use. In this context, isotopic
compositions of incrementally grown tissues such as keratinous hairs offer a valuable
opportunity to study long-term
variation in resource and habitat use. We investigated
the trophic ecology of female Cape fur seals (Arctocephalus pusillus pusillus) using carbon
and nitrogen isotopic compositions of serially sampled whiskers collected at four
breeding sites along the coast of South Africa. Drawing on over 900 isotopic measurements,
we assessed geographic variability in isotopic niche width between colonies
and the degree of individual specialization. We found slight, but clear geographic differences
in isotopic ratios and isotopic niche widths, seemingly related to ecological
setting, with niche widths being proportional to the area of available shelf and shelf-slope
habitat surrounding the colony. We further identified periodic oscillations in
isotopic ratios, which likely reflect temporal patterns in foraging distribution and prey
type, linked to shifts in the availability of prey resources and their interaction with
constraints on individual females throughout their breeding cycle. Finally, individual
specialization indices revealed that each of the study populations contain specialist
individuals that utilize only a small subset of the total population niche width. The
degree of individual specialization was, however, not consistent across colonies and
may reflect an interactive influence between density-dependent
effects and habitat
heterogeneity. Overall, this study provides important information on the trophic ecology
of Cape fur seals breeding in South Africa and highlights the need to consider
geographic and individual variability when assessing the foraging ecology of marine
predators.
by migrations between winter low-latitude breeding grounds and summer high-latitude feeding
grounds. Southern Hemisphere humpback whales faced intensive exploitation during the whaling
eras and recently show evidence of population recovery. Gene flow and shared song indicate overlap
between the western (A) and eastern (B1, B2) Breeding Stocks in the South Atlantic and Indian
Oceans (C1). Here, we investigated photo-identification evidence of population interchange using
images of individuals photographed during boat-based tourism and research in Brazil and South
Africa from 1989 to 2022. Fluke images were uploaded to Happywhale, a global digital database for
marine mammal identification. Six whales were recaptured between countries from 2002 to 2021
with resighting intervals ranging from 0.76 to 12.92 years. Four whales originally photographed off
Abrolhos Bank, Brazil were photographed off the Western Cape, South Africa (feeding grounds for B2).
Two whales originally photographed off the Western Cape were photographed off Brazil, one traveling
to the Eastern Cape in the Southwestern Indian Ocean (a migration corridor for C1) before migrating
westward to Brazil. These findings photographically confirm interchange of humpback whales across
the South Atlantic and Indian Oceans and the importance of international collaboration to understand
population boundaries.
The role of top predators as indicators of marine ecosystems is widely acknowledged and monitoring of top predators assists the Department of Environmental Affairs (DEA) in its unique role of attempting to identify and monitor those potential areas of accumulation (over time) and aggregation (over space) of negative impacts on the environment. Large recent changes in the populations and distributions of some seabirds in southern Africa reflect shifts to the south and east in the distributions of their prey. Seabirds are also indicating change at South Africa’s sub-Antarctic Prince Edward Islands (PEIs). Monitoring of marine top predators has additionally proved useful in identifying thresholds of impact, beyond which the integrity of ecosystems is or maybe significantly altered. Ecotourism activities targeting marine top predators expanded rapidly in the 21st century and generate substantial revenue for South Africa. However, whereas some opportunistic, adaptable predators, e.g. seals, have a healthy conservation status, the overall conservation status of seabirds in South Africa has deteriorated. Abundant predators, such as seals, may have impacts on other species. Many of South Africa’s marine top predators travel extensive distances and hence require management at regional or international levels.