Assessing Extinction Risk in Anemonefishes

Assessing extinction risk in anemonefishes

Maarten De Brauwer

Supervisors: Dr. Jean-Paul Hobbs Prof. Euan Harvey

This thesis is submitted in partial fulfilment of the requirements for a Bachelor of Science (Honours) SCIE4501-450 4 FNAS Research Thesis

Faculty of Natural and Agricultural Sciences The University of Western Australia

Submitted May 2014

Formatted in the style of the journal Conservation Biology Abstract Anemonefishes are coral reef icons and an important contributor to coral reef tourism and the marine ornamental trade. All 28 species have an obligate symbiotic relationship with sea anemones, which makes them vulnerable to habitat destruction. Many anemonefish species are also vulnerable due to their low abundance and/or small geographic ranges, while impacts such as climate change and over-harvesting have caused local extinctions. Despite these vulnerabilities and threats, extinction risk has not been assessed for the majority of anemonefish species. Using a global database, this study assessed the extinction risk of all 28 species of anemonefish according to criteria B1, B2, C and D of The International Union for Conservation of Nature (IUCN) Red List. This study found that 100% of species under criterion B2 and 36% of species under criterion D2 face elevated risk of extinction and satisfy criteria for being listed in IUCN threatened categories. A restricted area of occupancy (criterion B2) was the most important driver for listing species as threatened. Endemic species are most at risk, eight of which could potentially be listed as Critically Endangered. These results highlight the vulnerabilities of habitat specialists and the urgent need to formally assess the extinction risk of anemonefishes. Formal placement on the IUCN Red List is likely to lead to the development of suitable protective measures to guarantee the persistence of this coral reef icon. Furthermore, listed anemonefishes could serve as a flagship or model group for other, less studied, habitat specialists.

Key Words anemonefishes, Amphiprion, Premnas, extinction risk, endemic species, IUCN, habitat specialists, coral reefs

Table of contents

Research thesis

Acknowledgements ...... 4

Introduction ...... 5

Methods ...... 7

Results ...... 13

Discussion ...... 18

References ...... 22

Acknowledgments

Writing a research thesis is impossible to do on your own. Therefore, I would like to thank the following people without whom this thesis would never have been submitted. First and foremost, I would like to thank Eva “Boss” McClure. Without her invitation to do fieldwork I would never have returned to university study in the first place. Eva and Derek Sun were the ones who convinced me that studying in Australia was possible. Thank you.

Further, I would like to express my gratitude to my supervisors Dr Jean-Paul Hobbs and Prof Euan Harvey. JP, thank you for offering me this fantastic project and for sharing your ideas. Your support, great feedback, and advice made a world of difference. I am looking forward to working with you in the future. Also, thank you Euan for giving me the chance to pursue my dream of becoming a real marine biologist and for getting me in touch with JP.

I would like to thank the numerous people and organisations who contributed their data to this thesis: Michael Berumen, Ashley Frisch, Nick Graham, Alison Green, Andrew Halford, Alec Hughes, Jean-Paul Hobbs, Michael Kulbicki, Sangeeta Manghubhai, Tim McClanahan, Jennifer McIlwain, Maya Srinavasan, Shaun Wilson, the Western Australia Department of Parks and Wildlife, the Khaled bin Sultan Living Oceans Foundation and Reef Life Survey.

This year would never have been possible without the financial support of my parents. I owe them a huge amount of gratitude. Thank you, I promise I will come back to Belgium one day. Melanie Trapon was always there for me with moral support, feedback and thought-provoking insights in the world of academia. For interesting, prolonged lunchtime sessions that sparked my imagination and provided an outlet for frustration, thank you Emily, Kelly, Katie and James. Lastly, I’d like to thank the people in the Marine Ecology lab for being a warm and welcoming group of people. I would particularly like to thank Todd Bond, who introduced me to GIS.

All the world is a laboratory to the inquiring mind ~ Martin H. Fischer

Word Count 6352

Introduction

Coral reefs provide habitat for thousands of species, supporting more than one third of the world’s known marine biodiversity (Knowlton et al. 2010). Millions of people depend on a wide range of coral reef species for food, tourism and trade (Costanza et al. 1997; UNEP 2004). However, increasing anthropogenic impacts are threatening the future of coral reefs. Currently 20% of coral reefs have been destroyed and another 50% are at risk of collapse (Wilkinson 2006). Habitat degradation and loss leads to a reduction in the abundance of species that rely on coral reefs. The challenge is to identify the types of species that are most susceptible to these impacts, so that management strategies can be devised to mitigate the threat.

The species most vulnerable to extinction tend to be those with low abundances and small geographic ranges (Gaston 1998). Furthermore, ecological specialists are likely to be impacted more severely than generalists (McKinney 1997; Koh et al. 2004; Munday 2004). Positive associations between low abundance, small range size and specialisation mean that endemic species face a much higher risk of extinction (“triple jeopardy”: Munday (2004)). On coral reefs, species that have obligate relationships with specific habitats, such as gorgonians (Reijnen et al. 2010), sponges (Wulff 2006) and corals (Munday et al. 1997) are likely to be most at risk from habitat degradation and loss (Munday 2004). Ultimately, the disappearance of specific microhabitats inevitably leads to the disappearance of their obligate symbionts (Dulvy et al. 2003; Travis 2003; Jones et al. 2004; Munday 2004). Therefore, there is a need to identify habitat specialists that have small range sizes and low abundances because these are the species most at risk of extinction.

Anemonefishes are the best known habitat specialists on coral reefs. They are famous for their symbiotic relationship with anemones, and are among the most popular attractions for snorkel and dive tourism (Coghlan & Prideaux 2012) and the most traded species in the global marine ornamental trade (Wabnitz et al. 2003). All 28 anemonefish species live in an obligate symbiotic relationship with up to 10 species of host anemone (Fautin & Allen 1992; Allen et al. 2008; Allen et al. 2010). Anemonefishes are found in shallow reefs environments throughout the tropical and subtropical regions of the Indo-Pacific and Red Sea. Many anemonefishes are endemic to isolated parts of the world (Fautin & Allen 1992), and if these species also have low abundance, then this will greatly increase their risk of extinction.

Despite their popularity, little research has been done on the abundance of anemonefishes or the threats they face (Shuman et al. 2005; Jones et al. 2008; Hill & Scott 2012). At a local scale, collection of anemones and anemonefishes for the marine ornamental trade has caused significant declines in populations as well as local extinctions (Sin et al. 1994; Hattori 2002; Shuman et al. 2005). Host anemones usually have very low abundances on coral reefs (Richardson et al. 1997; Chadwick & Arvedlund 2005; De Brauwer et al. Appendix 2) and are susceptible to temperature induced bleaching (Jones et al. 2008; Hill & Scott 2012; Hobbs et al. 2013), which can cause mass mortality of anemones and local extinctions of anemonefish (Hattori 2002). Rising sea temperatures associated with climate change are predicted to lead to an increase in the severity and frequency of bleaching events (Hoegh-Guldberg 1999). This represents a serious global threat to the future of anemones and anemonefishes (Hobbs et al. 2013).

Determining which anemonefish species are most at risk of extinction (Hutchings 2001; Dulvy et al. 2004) is important for developing protective measures to ensure their conservation (Bellwood et al. 2004). The International Union for Conservation of Nature (IUCN) provides a valuable framework to objectively assess the extinction risk of species through the use of the Red List of Endangered Species (Rodrigues et al. 2006). The goals of the Red List are: 1) identify and document species most in need of conservation attention; and 2), provide a global index of the state of degeneration of biodiversity (Mace et al. 2008; IUCN 2014). A species’ risk of extinction is assessed using Red List criteria (e.g. geographic range size and abundance) and assigned to one of nine different categories, implying different probabilities of extinction (Fig. 1). Species considered to be endangered with extinction are placed in one of three “threatened” – categories; Vulnerable (VU), Endangered (EN) or Critically Endangered (CR). Placement into one of the threatened categories is recognition of a species’ extinction risk and can stimulate implementation of suitable conservation measures (IUCN 2014). Species which are evaluated and are not classified as threatened or extinct may fall into a lower risk category (Near Threatened, Least Concern), or may have insufficient data to be accurately assessed (Data Deficient).

Figure 1. Structure of IUCN categories. From: Red List guidelines (IUCN 2014).

As iconic species, anemonefishes have the potential to be used as both a flagship and a model group for the conservation of habitat specialists in the marine environment (Zacharias & Roff 2001; Caro et al. 2004). Despite the popularity of anemonefishes and high degree of habitat specialisation, so far only one species of anemonefish (Amphiprion sandaracinos) has been assessed using IUCN criteria and is listed as Least Concern (Curtis-Quick 2010). Since this original assessment, further data on the abundance of this species has been collected and warrants reassessment. Furthermore, the other 27 species have never been assessed and there is a need to determine which are the most vulnerable.

The aim of this study was to assess the extinction risk of all 28 species of anemonefishes using the following IUCN criteria:

 B1: Extent of occurrence  B2: Area of occupancy  C: Small population size and decline  D: Very small or restricted population

Methods

Study system This study investigated the distribution and abundance of anemonefishes throughout their geographic ranges. This encompassed the region from East Africa and the Red Sea to French

Polynesia and between latitudes 33° N (Japan) and 32° S (New South Wales, Australia). Abundance data for this study were collected between 1986 and 2014, with the majority of data (> 67 %, 7367 transects) collected after 2005. A total of 10974 transects were conducted on coral reefs at more than 1675 sites in 351 different locations across 34 countries (Fig.2), totalling a surveyed coral reef area of more than 3 600 000 m2. The number of transects in each major biogeographic region were: 934 in the Red Sea, 2489 in the Indian Ocean and 7551 in the Pacific Ocean (including the Indo-Australian Archipelago).

Figure 2. Map summarising the survey locations throughout the Indo-Pacific and Red Sea where anemonefish abundance was surveyed (between 1986 and 2014).

Surveys targeted all 28 species of anemonefishes. Two species (A. thiellei and A. leucokranos) were omitted from analysis, as they are thought to be hybrids (Allen & Erdmann 2012). Two other species, A. barberi and A. pacificus (Allen et al. 2010; Allen et al. 2008) have been described during the time span of this study and therefore data for these species may have been recorded as another species. Because A. barberi has a distinct geographic range, and there are no other similarly coloured species occurring in this range (Allen et al. 2008), individuals recorded as A. melanopus in this geographical area were assumed to have been A. barberi. This method was not applicable for A. pacificus because A. perideraion and A. sandarcinos potentially occur in the range of A. pacificus and are similar in colouration (Allen et al. 2010).

IUCN criteria IUCN uses five criteria to evaluate if a species should be listed in a threatened category. Due to data limitations, this study only examined the following criteria: B – geographic range, C –

small population size and decline, and D – very small or restricted population. Criterion B is split into two different criteria (B1 and B2), independent of each other and are hereafter considered as two separate criteria. This also applies for criterion D, however due to the nature of this criterion (results are dependent on criteria B2 and C, therefore avoiding further complicated calculations) it was decided to keep it as a single criterion.

Each criterion has specific thresholds that place species into one of the Red List categories. Meeting the threshold of one of the five criteria is sufficient to qualify a species for an endangered listing. If multiple criteria place the species in different categories, the species is listed in the most conservative category (i.e. highest risk of extinction). All criteria have additional conditions which need to be fulfilled in order for a species to qualify for formal placement in threatened categories (IUCN 2014). The nature of the data did not always allow for evaluation of these conditions, therefore, suggestions for listing in appropriate categories are solely based on the main criteria (Table 1). As such, the assessments of some species in this study will need to investigated further before these species can be consider for official listing status. Specifically, the criteria used in this study were:

 B1 - Extent of occurrence (EOO): EOO is defined as the area which encompasses all known, inferred and projected sites of present occurrence of a species (IUCN 2001, 2012b). To qualify for placement in threatened categories under B1, species also need to qualify for at least two of the following sub-criteria: Severely fragmented Population, Continuing Decline, or Extreme Fluctuations (IUCN 2014).  B2 - Area of occupancy (AOO): AOO is defined as the area within a species’ EOO, which is occupied by the species, excluding cases of vagrancy (IUCN 2001, 2012b). This measure represents the area of suitable habitat currently occupied by the species. To qualify for placement in threatened categories under B2, species also need to qualify for at least two of the following sub-criteria: Severely fragmented Population, Continuing Decline or Extreme Fluctuations (IUCN 2014).  C - Small population size: Population size is defined as the total number of mature individuals of the species (IUCN 2001, 2012b). The criterion specifies that if any immature individuals can quickly mature, they should be considered in the total number of mature individuals (IUCN 2014). Given that an immature anemonefish can quickly become reproductive if an individual of the breeding pair dies (Fautin & Allen 1992), the mature population size was considered to be all individuals. Also, size

estimates and reproductive status of anemonefishes were not available for the most of the survey abundance data and therefore, it is difficult to know the exact number of mature individuals. Indication of a continuing decline in the population is also necessary to quality for placement in the threatened-categories under C (IUCN 2014).  D - Very small or restricted population: This criterion defines species with very small population sizes (criterion D) or a very restricted distribution (criterion D2) that do not qualify for any of the sub-criteria under B1, B2 or C. The focus for this criterion, however, is not so much the restricted area of occupancy or population count, but the risk of a species suddenly becoming Critically Endangered or Extinct by stochastic events (e.g. cyclone, bleaching event) (IUCN 2014).

Table 1. Principal thresholds for listing species as Critically Endangered, Endangered or Vulnerable under IUCN criteria B1, B2, C and D. Units in C and D are numbers of adult individuals except where otherwise stated. AOO = Area of occupancy. Criteria Critically Endangered Endangered Vulnerable

B1: Extent of occurrence < 100 km2 < 5000 km2 < 20000 km2

B2: Area of occupancy < 10 km2 < 500 km2 < 2000 km2

C: Adult Population < 250 < 2500 < 10000

D: Small or Restricted Population < 50 < 250 < 1000 OR < 20 km2 AOO

Data analysis Data were combined and standardised into one Excel database. Before any analyses were undertaken, observations were checked for potentially misidentified species such as A. ocellaris and A. percula, which are very similar in appearance, but whose ranges do not overlap. Other obvious errors, such as species observed more than 1000 km outside their range, were removed before analysis.

Density - Data on fish abundance was first standardised to a survey area of 250 m² because this was the most commonly-used transect method. Mean density for each species was then calculated using data from all the survey locations within each species’ specific geographic range.

GIS - Each species’ geographic range was calculated using Geographic Information System (GIS) software ArcMap10.2 (Esri, California). Calculations were based on the most up to date maps of species’ ranges (Fautin & Allen 1992; Allen et al. 2008; Allen et al. 2010; Fishbase

2013) and confirmed observations in the database. The distribution of species was represented as a single polygon, except for species with a split distribution (e.g. A. akalopisos). In this case several separate polygons were created to represent the species’ distribution. Direct measures of coral reef area per country were taken from Spalding et al. (2001). The United Nations Environmental Programme and World Conservation Monitoring Centre’s (UNEP- WCMC) “Global distribution of Coral Reefs (2010)” shapefiles (Spalding et al. 2001; IMaRS-USF 2005; IMaRS-USF, IRD 2005; UNEP-WCMC, WorldFish Centre et al. 2010) were used to obtain coral reef area for species with geographical ranges that do not span entire countries.

A model was developed to create buffers of different sizes around coral reefs to represent all possible suitable habitats for anemonefishes. This model selected all coral reefs inside the geographical range of the species and created buffers of a given distance around the selected coral reefs (excluding land). The buffers were created in order to exclude unsuitable habitats such as deep water. Furthermore, the different sized buffers account for potential incompletely mapped coral reefs in the Pacific Ocean (Allen 2008) and to include anemonefish species living near coral reefs but not on them (Fautin & Allen 1992; Saenz- agudelo et al. 2011). IUCN mapping guidelines propose a 50 km buffer for coastal species, while recognising this potentially overestimates the actual EOO (IUCN Red List Training Course 2014). A 0.5 km buffer has been used by other authors when calculating ranges of coral reef fishes (Allen 2008). Both buffers avoid underestimating available coral reef habitat, but are conservative in that they probably overestimate true available habitat.

Criterion B1 - Four different methods were used to calculate the EOO per species. Coral reef areas were calculated from UNEP-WCMC coral reef shapefiles or from Spalding et al. (2001) where possible. The four methods are ordered from least to most representative:

1. Method α: The area of the species’ entire range as per Fautin & Allen 1992; Allen et al. 2008; Allen et al. 2010. This area includes unsuitable habitat such as deep water or coastal water lacking coral reefs. 2. Method β: Coral reef area within each species’ range plus a buffer of 50 km around all coral reefs. This method considerably reduces the amount of unsuitable, deep-water habitat. 3. Method γ: Coral reefs within each species’ range plus a buffer of 0.5 km around all coral reefs. This further reduces the amount of unsuitable, deeper habitat.

4. Method δ: Coral reef inside the range of each species calculated from Spalding et al. (2001). When this was not feasible (e.g. species with ranges spanning multiple countries), UNEP-WCMC Coral reef shapefiles were used in ArcMap 10.2 to calculate the area.

Criterion B2 - To calculate the total AOO, four different methods were applied. All methods - except for method α - assume AOO to be the total available area of host anemones inside the anemonefish species’ range (Fautin & Allen 1992). Coral reef areas were calculated form UNEP-WCMC Coral reef shapefiles or Spalding et al. 2001 where possible. Percent cover of host anemones on coral reefs was obtained from De Brauwer et al. (Appendix 2) and is based on 4344 transects on coral reefs throughout the Indo-Pacific and Red Sea. The estimate of host anemone percent cover used was 0.22%, which is the mean density for all ten host species globally. The density of anemones used by each anemonefish species is likely to be less since most anemonefish species (except for A. clarkii) do not use all ten species of host anemones (Fautin & Allen 1992). The four methods are ordered from least to most representative:

1. Method α: Total area of coral reef inside the range of each species. Since anemonefishes are obligate habitat specialists that only live in host anemones, this method is an overestimate of potential habitat. This is the same method as Method δ for criterion B1. 2. Method 훽: Mean percent cover of host anemones (0.22%, De Brauwer et al. Appendix 2) on coral reefs multiplied by the area of coral reef within each species’ range including a buffer of 50 km around all coral reefs. 3. Method γ: Mean percent cover of host anemones (0.22%, De Brauwer et al. Appendix 2) on coral reefs multiplied by the area of coral reefs within each species’ range including a 0.5 km buffer. 4. Method δ: Mean percent cover of host anemones (0.22%, De Brauwer et al. Appendix 2) on coral reefs multiplied by the area of coral reefs within each species’ range.

Criterion C - Three different methods were used to obtain an estimate of total adult population of a species. The overall density of anemonefish per transect area (standardised to 250 m2) was used to obtain a population estimate because data on the amount of anemonefish

per anemone was unavailable. All anemonefish surveys were conducted on coral reefs, which made it possible to use total coral reef habitat inside the species’ range as a proxy for total population size of anemonefish. The formula used to calculate population was: (density anemonefish species/250 m2) × (coral reef area). The three different methods in order of increasing representativeness are:

1. Method α: Density of anemonefish species multiplied by area of coral reef within its range including a 50 km buffer around coral reefs. 2. Method β: Density of anemonefish species multiplied by area of coral reef within its range including a 0.5 km buffer around coral reefs. 3. Method γ: Density of anemonefish species multiplied by area of coral reef within its range.

Criterion D - The methods applied on criterion D use the results obtained for criteria B2 and C. These results were then tested for the different thresholds specific to criterion D. Therefore seven possible methods were applied to D (Table 2).

Table 2. Methods used for IUCN criterion D. Method Uses results of method Applied to threshold of criterion

α Criterion B2 - α D2

β Criterion B2 - β D2

γ Criterion B2 - γ D2

δ Criterion B2 - δ D2

ε Criterion C - α D

η Criterion C - β D

θ Criterion C - γ D

Results

The mean densities of all species of anemonefish were found to be very low (Fig. 3). The species with the highest density (A. mccullochi, 1.84 individuals per 250 m2) is an endemic to the Lord Howe Island region in the South-West Pacific Ocean. A. sandaracinos had the

13 lowest density (0.01 per 250 m2) of all the observed species. Five species were not recorded in any surveys. Two species (A. chagosensis and A. chrysogaster) are endemic to the Chagos Archipelago and Mauritius respectively and no individuals were recorded in the surveys at these locations. Two other species (A. polymnus and A. sebae) were not sighted in the coral reef surveys because they inhabit anemones that occur off coral reefs (Fautin & Allen 1992; Saenz-Agudelo et al. 2011). The fifth unobserved species (A. pacificus) has only recently been described (Allen et al. 2010) and dedicated survey data was not available in its geographic range (Fiji, Samoa and Tonga).

2.50 SE)

± 2.00

( 2 2 1.50

1.00

0.50

0.00 Meandensity per250m

Anemonefish species

Figure 3. Mean density (± SE) of anemonefishes per 250 m2 within the corresponding geographic range of each species. Five species (A. chagosensis, A. chrysogaster, A. pacificus, A. polymnus and A. sebae) that were not observed are omitted.

Although the majority of species are listed as Least Concern for most criteria (Table 3), IUCN assigns a species to the highest threat category recorded for any one criterion. The criterion B2 (area of occupancy) is particularly important to listing anemonefishes in categories of elevated risk of extinction. Using the more conservative methods on criterion B2 means that all 28 species of anemonefish could potentially be listed in threatened categories – 20 species as Endangered and 8 species as Critically Endangered. For two species (A chagosensis and A. chrysogaster), criteria C and D also yielded an equally high level of listing (Critically Endangered). Overall, endemic species occupy the categories representing the highest risk of extinction.

Table 3. Overview of the most common and most conservative listings per species. The last column lists the criteria that resulted in the most conservative listing. LC = Least Concern, EN = Endangered and CR = Critically Endangered. Most common Most conservative Criteria most conservative listing listing listing A. akallopisos LC EN B2 A. akindynos LC EN B2 A. allardi LC EN B2 A. barberi LC EN B2 A. bicinctus LC EN B2 A. chagosensis LC CR B2, C, D A. chrysogaster CR CR B2, C, D A. chrysopterus LC EN B2 A. clarkii LC EN B2 A. ephippium LC EN B2 A. frenatus LC EN B2 A. fuscocaudatus LC CR B2 A. latezonatus LC CR B2 A. latifasciatus LC CR B2 A. mccullochi LC CR B2 A. melanopus LC EN B2 A. nigripes LC EN B2 A. ocellaris LC EN B2 A. omanensis LC CR B2 A. pacificus LC EN B2 A. percula LC EN B2 A. perideraion LC EN B2 A. polymnus LC EN B2 A. rubrocinctus LC CR B2 A. sandaracinos LC EN B2 A. sebae LC EN B2 A. tricinctus LC EN B2 P. biaculeatus LC EN B2

Criterion B1 – When using the more conservative methods, the calculated area of extent of occurrence decreased considerably, which increased the proportion of species placed in threatened-categories (Fig. 4). Using the least conservative estimate of species’ extent of

15 occurrence (method α), only one species (A. chrysogaster) qualifies for placement in the Vulnerable category. Using the most conservative estimates of EOO (method δ), more than half of all anemonefish species could be placed in threatened categories (Vulnerable and Endangered).

20 LC 15 VU 10 EN 5 CR

Number of species of Number 0 α β γ δ Method

Figure 4. Number of species in IUCN risk of extinction categories according to different methods applied to criterion B1. LC = Least Concern, VU = Vulnerable, EN = Endangered, CR = Critically Endangered. Methods: α: Area of range as in Fautin and Allen 1992, β: Area of 50km buffer around coral reefs in species’ range, γ: Area of 0.5km buffer around coral reefs in species’ range, δ: Area of coral reefs in range (according to Spalding et al. 2001).

Criterion B2 - The number of anemonefish species that qualified for listing in threatened categories based on area of occupancy varied considerably depending on which of the four calculation methods was used (Fig. 5). Using the least conservative calculation method (include the methods symbol in brackets), 23 species qualify as least concern and five species could potentially be listed in threatened categories (Vulnerable and Endangered). More conservative methods (methods γ and δ) would place all 28 species in one of the three threatened categories, with eight species being listed in the highest threat category (Critically Endangered).

15 LC VU 10 EN

Numberofspecies 5 CR

0 α β γ δ Method

Figure 5. Number of species in IUCN risk of extinction-categories according to different methods applied to criterion B2. LC = Least Concern, VU = Vulnerable, EN = Endangered, CR = Critically Endangered. Methods: α: Area of coral reefs in range (According to Spalding et al. 2001), β: Anemone density 0.22% × Area of 50km buffer around coral reefs in species’ range, γ: Anemone density 0.22% × Area of 0.5km buffer around coral reefs in species’ range. δ: Anemone density 0.22% × Area of coral reefs in range.

Criterion C - Estimates for the total adult populations were conducted using three methods (Fig. 6). For the majority of species, none of the three methods resulted in a listing in any threatened category. The exceptions were two species that were not recorded in any survey (A. chagosensis and A. chrysogaster), therefore resulting in a population estimate of 0 individuals, which would qualify as Critically Endangered. A further three species (A. pacificus, A. polymnus and A. sebae) were not observed either, however due to the circumstances surrounding these species (see above), placement in the Data Deficient category was considered to be appropriate.

15 LC 10 DD 5 CR

Numberofspecies 0 α β γ Method

Figure 6. Number of species in IUCN risk of extinction-categories according to different methods applied to criterion C. LC = Least Concern, DD: Data deficient, CR = Critically Endangered. Methods used were: α: Density species × area 50km buffer around coral reefs in species’ range, β: Density species × area 0.5km buffer around coral reefs in species’ range, γ: Density species × area coral reefs in species’ range.

Criterion D - Seven different methods were applied to assess listing under the D-criterion (Fig. 7). The least conservative methods yielded no species as threatened with extinction. Under the most conservative method of AOO (D2 subcategory), ten species, all of which are endemics, could qualify as Vulnerable. The most conservative estimates of population size resulted in the same two species potentially being listed as Critically Endangered.

20 DD 15 LC VU 10

Numberofspecies EN 5 CR

0 α β γ δ ε η θ Method

Figure 7. Amount of species in IUCN risk of extinction-categories according to different methods applied to criterion D. LC = Least Concern, DD: Data deficient, VU = Vulnerable, EN = Endangered, CR = Critically Endangered. Methods: α: Area of coral reefs in range (According to Spalding et al. 2001) β: Anemone density 0.22% × Area of 50km buffer around coral reefs in species’ range, γ: Anemone density 0.22% × Area of 0.5km buffer around coral reefs in species’ range. δ: Anemone density 0.22% × Area of coral reefs in range ε: Density species × area coral reefs in species’ range, η: Density species × area 50km buffer around coral reefs in species’ range, θ: Density species × area 0.5km buffer around coral reefs in species’ range.

Discussion

Objective assessments of extinction risk are a crucial step in identifying the species most vulnerable to increasing habitat loss and escalating human impacts, and therefore in greatest need of conservation management (Bellwood et al. 2004; Rodrigues et al. 2006). This study found that several species of anemonefish could qualify for listing in one of the threatened categories of the IUCN Red List. Endemic species had the highest risk of extinction and were listed due to their small area of occupancy (criteria B2). The use of different calculation methods affected the number of species listed as threatened, with the most conservative methods for determining the area of occupancy resulting in all 28 species qualifying in threatened categories.

The various methods used to calculate extent of occurrence (criterion B1) and area of occupancy (B2) provide a measure of how species are geographically distributed, and how an entire species may be affected by local threats (Mace et al. 2008). For extent of occurrence, methods γ and δ provide the most accurate representation for anemonefishes because they exclude most of the unsuitable habitat. While these methods might seem very conservative, even more conservative estimates (a buffer of 0.1 km instead of 0.5 km) have been used for the official listing of other marine habitat specialists such as the leafy seadragon (Phycodurus eques) (Connolly 2006). Determining the true area of occupancy has generally proven difficult to estimate for most marine species, because there is insufficient data on occupied locations throughout the large geographic ranges typical of most marine species (Mace et al. 2008). Obtaining this data from field surveys is important because this criterion is particularly relevant for habitat specialists (Mace et al. 2008; IUCN 2014).

The results from this study show that a limited area of occupancy is the criteria most often satisfied for listing anemonefish species in threatened categories. Therefore, impacts that reduce the amount of available habitat, rather than directly reduce the number of individuals, are likely to pose the greatest threat. For example, mortality of anemones due to bleaching events (Hobbs et al. 2013) and harvesting of host anemones for the marine ornamental trade (Wabnitz et al. 2003; Shuman et al. 2005) are likely to have a significant impact on anemonefish populations because they will reduce an already small area of occupancy. Endemic species tended to satisfy criteria for the highest threatened category (Critically Endangered) due to their extremely small area of occupancy. Therefore, endemic species should be a conservation priority, particularly if they possess other vulnerability traits associated with endemism (e.g. low genetic diversity, highly desired for marine ornamental trade). For a formal IUCN listing, species need to also satisfy two of the three additional B2 sub-criteria (severely fragmented population, continuing population decline, extreme population fluctuations) (IUCN 2014). Further field studies would be required to obtain the necessary data to address these sub-criteria, but it is likely that many of the 28 species of anemonefishes will meet the additional criteria (Sin et al. 1994; Hattori 2002, 2005; Shuman et al. 2005).

The adult population sizes (criterion C) estimated in this study do not qualify any anemonefish species for listing in any of the threatened categories, except for the two species that were not observed in surveys. The fact that many species were considered threatened

19 based on B1 and B2, but not for C is not surprising, as small population size and small geographic ranges are not necessarily linked for marine species (Hobbs et al. 2011). Thus when assessing extinction risk, population size is not always relevant, particularly when species are restricted to small habitats that are disappearing (Mace et al. 2008). A second criterion, declining population, is essential to list species under criterion C. Although this data was not available, a declining population can be inferred through a decline in habitat or habitat quality (IUCN 2014). Therefore, reported evidence of declines in host anemones (Hattori 2002, 2005; Hobbs et al. 2013; Thomas et al., in press) would fulfil this criterion.

Two endemic species could potentially qualify as Critically Endangered under criterion D (A. chagosensis and A. chrysogaster). Since they were not observed in any surveys, their estimated population is zero. Individuals of these species have been observed outside transects, indicating that further field surveys are required to obtain population estimates for these rare species. That these species were not recorded in surveys on suitable coral reef habitat indicates that the population size of these two species is probably small. At least nine endemic anemonefish species could be listed in threatened categories under criterion D2 due to their very restricted range. Under this criterion the highest possible threat level that species can be listed as is Vulnerable (IUCN 2014). A Vulnerable listing might be an underestimate for some species, but still indicates the need for protective measures. One additional criterion needs to be proven to formally use D2 for listing a species; a high risk of possible stochastic events in the future that could quickly lead to a Critically Endangered or Extinct listing (IUCN 2014). Previously recorded local extinctions of anemonefish species related to anemone bleaching (Hattori 2002) and a predicted increase in anemone bleaching events (Hobbs et al. 2013) fulfil this additional criterion (Akçakaya et al. 2006).

This study has found that many anemonefish fulfil some of the criteria for listing under IUCN threatened categories. However, further information is required to formally assess species for IUCN listing. The data that is mostly lacking is temporal data on population trends (required for criteria A, B and C). This data could be generated by adding anemonefish to existing long- term monitoring programs. Further information is also required on the changes in habitat quality and area (required for criteria A, B, C and D). Host anemones tend to be rare on coral reefs (De Brauwer et al. Appendix 2), thus, dedicated monitoring of known anemones (e.g. through tagging or mapping) would be required to obtain the necessary information on habitat changes. An unbiased assessment of threats facing these fishes and their hosts would also aid in assessment for all criteria. Obtaining all the necessary data for formal IUCN listing could

take too long to prevent serious population declines from occurring. Therefore, other factors could be used as early indications of extinction risk. Rising sea temperatures associated with climate change are a major threat to coral reef biodiversity due to the predicted increase in frequency and severity of bleaching events (Hoegh-Guldberg 1999; Hughes et al. 2003). Bleaching events can cause mortality to anemones (Hobbs et al. 2013) that can lead to local extinctions of anemonefishes (Hattori 2002). The method of using climate change and other threats to evaluate species’ extinction risk has led to one third of the world’s reef building corals being listed in IUCN threatened categories (Carpenter et al. 2008).

The high proportion of anemonefishes that meet particular criteria for listing in threatened IUCN categories (particularly due to limited area of occupancy), highlights the vulnerability of habitat specialists. Numerous marine organisms are habitat specialists (Fautin & Allen 1992; Munday et al. 1997; Wulff 2006; Wilson et al. 2008; Reijnen et al. 2010) and remain un-assessed (McClenachan et al. 2012). Assessing habitat specialists should be a conservation priority, as history reveals these types of species are among those most likely to go extinct (McKinney 1997). However, many marine habitat specialists are small and cryptic (Munday et al. 1997; Munday & Jones 1998) and cannot currently be assessed due to the lack of data on area of occupancy, size and changes in population (Chapman 1999). Until this data is available, indicators such as climate change threats or restricted ranges can aid in listing species under threatened categories (Akçakaya et al. 2006).

Anemonefishes are a model group that highlight the challenges associated with IUCN classification of marine habitat specialists and lack of data in the marine environment. Nevertheless, this study showed that 100% of species under criterion B2 and 36% of species under criterion D2 face elevated risk of extinction and satisfy criteria for being listed in IUCN threatened categories. Further data on declines in population or habitat size and future threats are required for a formal IUCN listing. Anemonefishes are one of the best-studied groups of marine habitat specialists and many lesser-known habitat specialists may also be at risk of extinction. However, this would require a shift in the focus of field surveys towards habitat specialists because there is currently insufficient data to assess and therefore manage their risk of extinction. The popularity of anemonefishes means that their listing in threatened categories could serve either as flagship or model species for assessing extinction risk and ultimately conserving habitat specialists in the marine environment.

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