**4. Whale and environmental surveys in the Indo-Pacific sector**

As explained briefly above, the causes of ecosystem changes in the Antarctic are complex. To determine those causes, long-term monitoring research programs focused on collecting biological data of krill predators, as well data on sea ice cover and environmental variables, are important. The kind of information which is used to monitor changes in the ecosystem through sea-based predators (whales) and their environment is shown in **Table 1**.

Most of the data in **Table 1**, which have been used in the studies summarized below, come from two main sources.

**89**

*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem…*

Whale abundance Systematic sighting surveys Fluctuations in the abundance of whales over

Whale distribution Systematic sighting surveys Distributions of whale species can change with

**Relevance of monitoring**

different impacts on krill

abundance

contents

higher pregnancy rates

climate change

Krill is a key species in the Antarctic ecosystem. Changes in its abundance have effects on predators and the whole ecosystem

time is important for their management. Different levels of whale abundance have

time in response to changes in abundance and/ or changes in oceanographic conditions/krill

Same as above. Index of young whale abundance

Index of body condition. Better nutritional condition (e.g. better availability through higher abundance of krill) will be reflected in thicker blubber, heavier fat and larger girth

Index of body condition. Better nutritional condition will be reflected by heavier stomach

Better nutritional conditions will be reflected in a shift of the ASM to younger ages, so that whales will be able to reproduce at younger ages

Better nutritional conditions will be reflected in

Changes in oceanographic conditions will affect the distribution and krill biomass, and in turn the abundance and distribution of whales. Changes in oceanographic conditions might be an effect of

*DOI: http://dx.doi.org/10.5772/intechopen.94323*

**Parameter How the information is** 

Krill biomass Echo-sounder and net

Whale recruitment Population dynamic

Blubber thickness, fat weight and girth

Stomach content weight

Age at sexual maturity (ASM)

Oceanographic conditions

**Table 1.**

*ecosystem.*

whales

Pregnancy rate Examination of ovaries and uterus

XCTD

sampled whales

sampled whales

Examination of the transition phase in earplugs; examination of ovaries and testis

models that use age and abundance information for

Direct measurements from

Direct measurements from

Systematic oceanographic surveys based on CTD and

**obtained?**

surveys

**4.1 JARPA and JARPAII programs**

The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) was conducted in the austral summers from 1987/88 to 2004/05, and its second phase (JARPAII) from 2005/06 to 2013/14. Both programs conducted systematic surveys in the Indo-Pacific sector (35°E-145°W) of the Antarctic using both lethal (biological sampling of a limited number of Antarctic minke whales) and non-lethal (biopsy sampling and photo-identification of large whales, oceanographic and marine debris surveys, dedicated sighting surveys) approaches. The main objectives of these programs were related to the investigation of stock structure, biological parameters and feeding ecology of Antarctic minke whales, as well the investigation of environmental pollutants in whale tissue and the environment. These surveys were conducted in the open sea because the survey vessels were not ice strengthened. Data and research outputs from JARPA and JARPAII were reviewed by IWC-organized international workshop of specialists, and they are

*Biological and ecological parameters monitored for whales and their environment to investigate changes in the* 

available in conjunction with the reports of those workshops [9, 12].


*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem… DOI: http://dx.doi.org/10.5772/intechopen.94323*

#### **Table 1.**

*Glaciers and the Polar Environment*

(mainly in Area VI) (**Figure 1**). There are some spatial overlaps between adjacent populations in the Antarctic [8]. The breeding areas for Populations 'D' and 'E' are

*Krill-eating baleen whale species in the Indo-Pacific sector of the Antarctic. Top left: humpback whale; top right: Antarctic minke whale; bottom left: fin whale; bottom right: Antarctic blue whale.*

This is one of the smallest baleen whale species with a maximum body length of more than 10 m and weight of nearly 10 tons. During the austral summer, Antarctic minke whales are distributed mainly around the pack-ice. There are at least two populations of this species in the Indo-Pacific sector of the Antarctic, the Eastern Indian Ocean population in the western part of the research area (mainly the eastern part of Area III and Area IV) (**Figure 1**), and the Western South Pacific population in the eastern part of the research area (mainly the eastern part of Area V and Area VI) (**Figure 1**) [9, 10]. Both populations interact in a transition area between approximately 100° and 160°E (eastern part of Area IV and western part of Area V) (**Figure 1**) [11]. The biological and demographic studies summarized below are based on the approximate geographic limits of these 'populations' in the case of humpback and Antarctic minke whales, and on geographical areas for those species with limited

information on population structure (Antarctic blue and fin whales).

**4. Whale and environmental surveys in the Indo-Pacific sector**

As explained briefly above, the causes of ecosystem changes in the Antarctic are complex. To determine those causes, long-term monitoring research programs focused on collecting biological data of krill predators, as well data on sea ice cover and environmental variables, are important. The kind of information which is used to monitor changes in the ecosystem through sea-based predators (whales) and

Most of the data in **Table 1**, which have been used in the studies summarized

located in West and East Australia, respectively.

their environment is shown in **Table 1**.

below, come from two main sources.

**3.4 Antarctic minke whale**

**Figure 2.**

**88**

*Biological and ecological parameters monitored for whales and their environment to investigate changes in the ecosystem.*

#### **4.1 JARPA and JARPAII programs**

The Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) was conducted in the austral summers from 1987/88 to 2004/05, and its second phase (JARPAII) from 2005/06 to 2013/14. Both programs conducted systematic surveys in the Indo-Pacific sector (35°E-145°W) of the Antarctic using both lethal (biological sampling of a limited number of Antarctic minke whales) and non-lethal (biopsy sampling and photo-identification of large whales, oceanographic and marine debris surveys, dedicated sighting surveys) approaches. The main objectives of these programs were related to the investigation of stock structure, biological parameters and feeding ecology of Antarctic minke whales, as well the investigation of environmental pollutants in whale tissue and the environment. These surveys were conducted in the open sea because the survey vessels were not ice strengthened. Data and research outputs from JARPA and JARPAII were reviewed by IWC-organized international workshop of specialists, and they are available in conjunction with the reports of those workshops [9, 12].

#### **4.2 IWC's IDCR/SOWER programs**

The IWC's International Decade for Cetacean Research (IDCR) undertook a series of Antarctic sighting cruises for assessment of Antarctic minke whales during the austral summers 1978/79–1995/96. From 1995/96 this was renamed the Southern Ocean Whale and Ecosystem Research (SOWER) program, and continued until the 2009/10 season. The primary aim of these programs was to conduct sighting surveys using the line transect method for estimating the abundance of Antarctic minke whales and other cetacean species. The survey programs have also enabled collection of biopsies, photo-identification, oceanographic and acoustic samples for studies on the ecosystem. As for JARPA and JARPAII, these surveys were conducted in the open sea because the survey vessels were not ice strengthened. Even though IDCR/SOWER surveys were conducted at a circumpolar level, it is the information from the surveys conducted in the Indo-Pacific sector, particularly in IWC Areas IV and V (see **Figure 1**), that is summarized here.

Some of the studies summarized below used biological data collected during former commercial whaling operations (by Japan and the former USSR) in the Indo-Pacific sector of the Antarctic.

## **5. Historical ecosystem changes revealed through whale demography**

#### **5.1 Trend in age at sexual maturity**

Changes in the age at sexual maturity (ASM) indicate changes in the nutritional conditions for the whales, which in turn could indicate less or more food availability in the environment. Better nutritional conditions will be reflected by a shift of the ASM to younger ages, so that whales will be able to reproduce at younger ages and as a consequence the populations will grow faster. One of the methods for determining ASM in whales is through the examination of the 'transition phase' in the earplugs [13]. The earplugs of several baleen whale stocks exhibit seasonal growth layers which have been shown for some species to indicate the age of the animals. A transition from early, irregular layers to later, more regular layers can be seen in these earplugs (the 'transition phase'), and this has been shown to indicate the age at sexual maturity of the whale [13]. Historical changes in the ASM can be investigated through the analyses of cohorts (groups of whales born in the same year).

Earplugs of Antarctic minke whales were collected during the period of commercial whaling in the early 1970's, and during the JARPA/JARPAII surveys in the Indo-Pacific sector of the Antarctic for more than 25 years. A decline in the average age at transition in Antarctic minke whales in the Eastern Indian Ocean population from roughly 11 years for the cohorts of the 1950's to roughly 7 years for the cohorts of the 1970's was evident (**Figure 3**), and this trend was similar for females and males. The ASM remained stable until the 1980's cohorts [14]. This work was subsequently updated [15] by using a large number of samples, and those authors confirmed that the ASM remained stable until the 1998 cohort at least. The same pattern was observed for the Western South Pacific population.

#### **5.2 Trend in recruitment rate and total population size**

The Scientific Committee (SC) of the IWC has been applying statistical catchat-age (SCAA) analyses to Antarctic minke whales since 2005. SCAA is a common method of fisheries stock assessment where age-structured catch data from a

**91**

for more than 25 years.

*cohorts (modified from [14]).*

**Figure 3.**

through the analyses of cohorts.

*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem…*

fishery are used to estimate quantities of interest, such as population size and natural mortality rates, employing the maximum likelihood estimation approach [16]. A summary history of the application of SCAA to Antarctic minke whale is provided

*Changes in the age at sexual maturity of Antarctic minke whale as determined from the transition phase, by cohort (Eastern Indian Ocean population). Histogram of the number of whales aged in each cohort is also showed. Age at sexual maturity changed from around 11 years in the 1950s cohorts to around 7 years in the 1970s* 

The data used when conducting assessment by SCAA on Antarctic minke whales consisted of catches, abundance estimates, length frequency data, and conditional age-at-length data. Different series of abundance estimates were used, i.e. those from the IWC's IDCR/SOWER and JARPA/JARPAII's dedicated sighting surveys in the Indo-Pacific sector of the Antarctic. The biological data mentioned above were available from the period of commercial whaling (Japan and the former USSR), and JARPA/JARPAII surveys in the Indo-Pacific sector of the Antarctic

The SCAA assessment on Antarctic minke whale included a 'reference' case and several sensitivity tests. These tests explored sensitivity to the weight assigned to the various data sources and penalties in the model fitting process, to assumptions related to vulnerability, natural mortality and catchability, and to the use or otherwise of the JARPA/JARPAII's abundance index data [18]. As in the estimation of the ASM, historical changes in recruitment and total population size can be investigated

**Figure 4** shows the temporal trend for the total size of the Eastern Indian Ocean population of Antarctic minke whales. Results presented here refer to the 'reference' case, and were robust to the sensitivity tests conducted. The population was estimated to have increased from 1930 until the early 1970's, with the population having declined subsequently and then staying stable. The increase in abundance

in [17], and an assessment of this species using SCAA is reported in [18].

*DOI: http://dx.doi.org/10.5772/intechopen.94323*

*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem… DOI: http://dx.doi.org/10.5772/intechopen.94323*

**Figure 3.**

*Glaciers and the Polar Environment*

**4.2 IWC's IDCR/SOWER programs**

Indo-Pacific sector of the Antarctic.

**5.1 Trend in age at sexual maturity**

of whales born in the same year).

The IWC's International Decade for Cetacean Research (IDCR) undertook a series of Antarctic sighting cruises for assessment of Antarctic minke whales during the austral summers 1978/79–1995/96. From 1995/96 this was renamed the Southern Ocean Whale and Ecosystem Research (SOWER) program, and continued until the 2009/10 season. The primary aim of these programs was to conduct sighting surveys using the line transect method for estimating the abundance of Antarctic minke whales and other cetacean species. The survey programs have also enabled collection of biopsies, photo-identification, oceanographic and acoustic samples for studies on the ecosystem. As for JARPA and JARPAII, these surveys were conducted in the open sea because the survey vessels were not ice strengthened. Even though IDCR/SOWER surveys were conducted at a circumpolar level, it is the information from the surveys conducted in the Indo-Pacific sector, particularly in

Some of the studies summarized below used biological data collected during former commercial whaling operations (by Japan and the former USSR) in the

**5. Historical ecosystem changes revealed through whale demography**

Changes in the age at sexual maturity (ASM) indicate changes in the nutritional conditions for the whales, which in turn could indicate less or more food availability in the environment. Better nutritional conditions will be reflected by a shift of the ASM to younger ages, so that whales will be able to reproduce at younger ages and as a consequence the populations will grow faster. One of the methods for determining ASM in whales is through the examination of the 'transition phase' in the earplugs [13]. The earplugs of several baleen whale stocks exhibit seasonal growth layers which have been shown for some species to indicate the age of the animals. A transition from early, irregular layers to later, more regular layers can be seen in these earplugs (the 'transition phase'), and this has been shown to indicate the age at sexual maturity of the whale [13]. Historical changes in the ASM can be investigated through the analyses of cohorts (groups

Earplugs of Antarctic minke whales were collected during the period of commercial whaling in the early 1970's, and during the JARPA/JARPAII surveys in the Indo-Pacific sector of the Antarctic for more than 25 years. A decline in the average age at transition in Antarctic minke whales in the Eastern Indian Ocean population from roughly 11 years for the cohorts of the 1950's to roughly 7 years for the cohorts of the 1970's was evident (**Figure 3**), and this trend was similar for females and males. The ASM remained stable until the 1980's cohorts [14]. This work was subsequently updated [15] by using a large number of samples, and those authors confirmed that the ASM remained stable until the 1998 cohort at least. The same

The Scientific Committee (SC) of the IWC has been applying statistical catchat-age (SCAA) analyses to Antarctic minke whales since 2005. SCAA is a common method of fisheries stock assessment where age-structured catch data from a

pattern was observed for the Western South Pacific population.

**5.2 Trend in recruitment rate and total population size**

IWC Areas IV and V (see **Figure 1**), that is summarized here.

**90**

*Changes in the age at sexual maturity of Antarctic minke whale as determined from the transition phase, by cohort (Eastern Indian Ocean population). Histogram of the number of whales aged in each cohort is also showed. Age at sexual maturity changed from around 11 years in the 1950s cohorts to around 7 years in the 1970s cohorts (modified from [14]).*

fishery are used to estimate quantities of interest, such as population size and natural mortality rates, employing the maximum likelihood estimation approach [16]. A summary history of the application of SCAA to Antarctic minke whale is provided in [17], and an assessment of this species using SCAA is reported in [18].

The data used when conducting assessment by SCAA on Antarctic minke whales consisted of catches, abundance estimates, length frequency data, and conditional age-at-length data. Different series of abundance estimates were used, i.e. those from the IWC's IDCR/SOWER and JARPA/JARPAII's dedicated sighting surveys in the Indo-Pacific sector of the Antarctic. The biological data mentioned above were available from the period of commercial whaling (Japan and the former USSR), and JARPA/JARPAII surveys in the Indo-Pacific sector of the Antarctic for more than 25 years.

The SCAA assessment on Antarctic minke whale included a 'reference' case and several sensitivity tests. These tests explored sensitivity to the weight assigned to the various data sources and penalties in the model fitting process, to assumptions related to vulnerability, natural mortality and catchability, and to the use or otherwise of the JARPA/JARPAII's abundance index data [18]. As in the estimation of the ASM, historical changes in recruitment and total population size can be investigated through the analyses of cohorts.

**Figure 4** shows the temporal trend for the total size of the Eastern Indian Ocean population of Antarctic minke whales. Results presented here refer to the 'reference' case, and were robust to the sensitivity tests conducted. The population was estimated to have increased from 1930 until the early 1970's, with the population having declined subsequently and then staying stable. The increase in abundance

#### **Figure 4.**

*Time trajectory of total (1+) population size for the Eastern Indian Ocean population of Antarctic minke whale (reference-case), by cohort. The dotted lines indicate 95% asymptotic confidence intervals (modified from [18]).*

was due primarily to an increase in recruitment (**Figure 5**), arising in turn from an increase in carrying capacity [18], presumably due to an increase in the abundance of krill. A similar pattern was found for the Western South Pacific population.

It is interesting to note that the increase in total population size from 1930 to the 1970's coincided roughly with the period over which the ASM decreased.

#### **5.3 Interpretation of results**

The results of this section can be summarized as following:


These historical changes in the demography of Antarctic minke whale are consistent with expectations under the krill surplus hypothesis. The harvesting of large whales in the Antarctic Ocean started in 1904, and several species of large whales such as the Antarctic blue and humpback whales were heavily depleted by

#### **Figure 5.**

*Time trajectory of recruitment for the Antarctic minke whale of the Eastern Indian Ocean population (from 1930 and from 1975) for the reference case analysis, by cohort (modified from [18]).*

**93**

CPIII).

*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem…*

the first half of the past century. Other species such as the fin whales were depleted during the second half of that century. Antarctic blue, fin and humpback whales were reduced to 5%, 21% and 2% of their original total sizes of 220,000, 490,000 and 130,000, respectively [19]. However, commercial harvesting of the Antarctic minke whales started only in the early 1970's, when the other baleen whale species

Some researchers have suggested that following the period of heavy harvesting of the large baleen whales in the Antarctic mainly during the middle decades of the past century, some 150 million tons of 'surplus' annual production of Antarctic krill became available for other krill predators, such as Antarctic minke whales, crabeater seals, fur seals, penguins and some albatrosses. These species then took advantage of this food surplus to increase their abundance. This is the so-called krill

The increased krill abundance around the middle of the past century could therefore have led to better nutritional conditions for some krill predators like the Antarctic minke whale. Although there is no direct observational evidence of improved nutritional conditions at that time, it is known that better nutritional conditions in whales may be reflected in a decrease in the age at sexual maturity. This was the case for Antarctic minke whales between approximately 1940 and 1970, which coincides with the period of depletion of some key krill-eating large whale species. This low age at sexual maturity led to an increase in the recruitment rate and total population size for minke whales over this period. The Antarctic minke whale perhaps rose to close to an increased carrying capacity resulting from a larger krill population by the 1970s, with the stock achieving this by stabilizing its age at sexual maturity at lower 7–8 years. The period of these demographic changes in Antarctic minke whales coincides with that characterized as 'favorable climate conditions and

reduced competition for krill' and linked to penguin population changes [3].

**6. Current ecosystem changes revealed through whale demography**

Commercial whaling of humpback, Antarctic blue and fin whales in the Antarctic was suspended in 1963, 1964 and 1976, respectively. As an effect of these conservation measures, the abundance of these species have increased in recent decades, i.e. there have been recoveries from past commercial harvesting. The speed of recovery varies among species and populations. The increases in abundance of the recovering species will have effects on the ecosystem as a whole. In this section the current information on abundance and abundance trends of baleen whale species is examined, as well as some aspects of current nutritional conditions, feeding ecology and biological parameters of the Antarctic minke whale, a species which

Estimates of abundance of large whales in the Antarctic are based on systematic

sighting surveys in open sea carried out under sampling methods advocated in DISTANCE [20], and the guidelines for surveys and analyses agreed by the IWC Scientific Committee (SC) [21]. Dedicated sighting surveys were carried out in the Indo-Pacific sector of the Antarctic under the JARPA/JARPAII programs using the IWC SC-agreed methodology and guidelines. Overall, the IWC SC carried out three circumpolar sighting surveys under the IDCR/SOWER programs (CPI, CPII and

benefited from the krill surplus during the last century.

**6.1 Abundance trend of baleen whales**

*DOI: http://dx.doi.org/10.5772/intechopen.94323*

were already depleted.

surplus hypothesis [1, 2].

*Whales as Indicators of Historical and Current Changes in the Marine Ecosystem… DOI: http://dx.doi.org/10.5772/intechopen.94323*

the first half of the past century. Other species such as the fin whales were depleted during the second half of that century. Antarctic blue, fin and humpback whales were reduced to 5%, 21% and 2% of their original total sizes of 220,000, 490,000 and 130,000, respectively [19]. However, commercial harvesting of the Antarctic minke whales started only in the early 1970's, when the other baleen whale species were already depleted.

Some researchers have suggested that following the period of heavy harvesting of the large baleen whales in the Antarctic mainly during the middle decades of the past century, some 150 million tons of 'surplus' annual production of Antarctic krill became available for other krill predators, such as Antarctic minke whales, crabeater seals, fur seals, penguins and some albatrosses. These species then took advantage of this food surplus to increase their abundance. This is the so-called krill surplus hypothesis [1, 2].

The increased krill abundance around the middle of the past century could therefore have led to better nutritional conditions for some krill predators like the Antarctic minke whale. Although there is no direct observational evidence of improved nutritional conditions at that time, it is known that better nutritional conditions in whales may be reflected in a decrease in the age at sexual maturity. This was the case for Antarctic minke whales between approximately 1940 and 1970, which coincides with the period of depletion of some key krill-eating large whale species. This low age at sexual maturity led to an increase in the recruitment rate and total population size for minke whales over this period. The Antarctic minke whale perhaps rose to close to an increased carrying capacity resulting from a larger krill population by the 1970s, with the stock achieving this by stabilizing its age at sexual maturity at lower 7–8 years. The period of these demographic changes in Antarctic minke whales coincides with that characterized as 'favorable climate conditions and reduced competition for krill' and linked to penguin population changes [3].
