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Trying to find Nemo: quantifying sea anemone and anemonefish abundances on central and southern mid-shelf reefs on the Great Barrier Reef, Australia
Abstract
Information on the abundance of species targeted for the marine aquarium trade is needed to help elucidate what levels of exploitation may be sustainable. Accordingly, this study documents the abundance and diversity of anemonefishes and their host sea anemones, which are highly sought after in the trade, using timed swims at seven mid-shelf reefs on the Great Barrier Reef, Australia. Three species of anemone (Entacmaea quadricolor n = 49, Heteractis magnifica n = 7, Stichodactyla mertensii n = 3), and five species of anemonefishes were found (Amphiprion akindynos n = 12, A. perideraion n = 29, A. melanopus n = 11, Premnas biaculeatus n = 2). Many of the surveys sites (58%) did not have anemones or anemonefishes, and at sites where they were present, numbers were generally low. Given these findings, it is essential that collection is carefully regulated to prevent localised extinctions and ensure that reproductive success is not adversely impacted.
... Interest in the extinction risk and conservation of anemonefishes might not have begun in 2003, but the Disney movie Finding Nemo sparked an interest in the conservation status of the very small coral reef fishes that continues today. The movie is directly quoted in the titles of numerous papers, including "Finding Nemo" (Ollerton et al. 2007), "Losing Nemo" , "Not Finding Nemo" (Nanninga et al. 2015), and "Trying to Find Nemo" (Scott and Baird 2015). There is a website dedicated to saving Nemo (www .savingnemo ...
... For whatever reason, the anemones that host anemonefishes are never particularly abundant on coral reefs. Hence, they almost always have low population densities resulting from naturally low densities of hosts (Srinivasan et al. 1997;Scott and Baird 2015;Steinberg et al. 2020;Hayashi et al. 2019b). Highly specialized species are even more likely to exhibit low abundance when their preferred habitats are rare (Jones et al. 2002;Munday 2004). ...
... Some species of host anemone, such as the highly conspicuous magnificent anemone Hecteractis magnifica, survive with or without anemonefish, suggesting they are facultative mutualists (Fautin 1992;Holbrook and Schmitt 2005). Other species, such as the relatively cryptic but widespread bubble-tip anemone Entacmaea quadricolor, are often unoccupied on subtropical reefs, but are rarely (if ever) unoccupied on tropical reefs (Scott et al. 2011;Scott and Baird 2014). The difference in occupancy is probably related to the geographic distribution of anemone predators such as corallivorous butterflyfish (Godwin and Fautin 1992;Porat and Chadwick-Furman 2004). ...
... Entacmaea quadricolor, the dominant species of anemone on the GBR (Hobbs et al. 2013;Scott and Baird 2014), has been commercially collected in the region for at least 45 yr, which may have contributed to observed population declines in high-use areas (Jones et al. 2008;Frisch and Hobbs 2009). Unlike most other anemones, which are typically solitary and host relatively small groups of anemonefish (Fautin and Allen 1997), E. quadricolor can form vast colonies (up to 362 polyps) that host large groups of anemonefish: 50 or more individuals in the case of the cinnamon anemonefish Amphiprion melanopus (Richardson et al. 1997a;Frisch and Hobbs 2009). ...
Intimate knowledge of both partners in a mutualism is necessary to understand the ecology and evolution of each partner, and to manage human impacts that asymmetrically affect one of the partners. Although anemonefishes and their host anemones are iconic mutualists and widely sought by ornamental fisheries, the degree to which anemones depend on anemonefishes, and thus the colony-level effects of collecting anemonefishes, is not well understood. We tracked the size and abundance of anemone Entacmaea quadricolor and anemonefish Amphiprion melanopus colonies for 3 yr after none, some, or all of the resident anemonefish were experimentally removed. Total and partial removal of anemonefish had rapid and sustained negative effects on growth, reproduction and survival of anemones, as well as cascading effects on recruitment and productivity of anemonefish in the remaining colony. As predicted, total removal of anemonefish caused acute declines in size and abundance of anemones, although most anemone colonies (76 %) slowly resumed growth and reproduction after the arrival of anemonefish recruits, which subsequently grew and defended the hosts. Partial removal of anemonefish had similar but typically less severe effects on anemones. Remarkably, the colony-level effects on anemones and anemonefish were proportional to the size and number of anemonefish that were experimentally removed. In particular, anemone survival and anemonefish productivity were highest when one or more adult anemonefish remained in the colony, suggesting that adult fish not only enhanced the protection of anemones, but also increased the recruitment and/or survival of conspecifics. We conclude that the relationship between E. quadricolor and A. melanopus is not only obligate, but also demographically rigid and easily perturbed by anemonefish fisheries. Clearly, these two species must be managed together as a unit and with utmost precaution. To this end, we propose several tangible management actions that will help to minimize fishing effects.
... consisting of more than ten individuals) were challenging and time-consuming, we first counted the total number of individual host anemones and measured ten randomly selected individuals to obtain the average size of the individuals within that colony (Hobbs et al. 2013). The species and the number of resident anemonefish were also recorded but individual fish < 3.5 cm in total length (TL) were not counted because they were highly cryptic (Scott and Baird 2015). There was no background anemone bleaching data prior to the warming event in this study but it was reasonable to assume that all host anemones were fully pigmented as we did not observe any bleaching during our reef surveys in March 2016 at the same sites. ...
Thermally-induced bleaching events pose significant impacts on coral reefs but current understanding of the bleaching effects on host sea anemones and mutualistic anemonefishes is limited compared to those of scleractinian corals and their associates. Such information is especially lacking in Southeast Asia, despite the region harbouring the highest diversity of host anemones and anemonefishes. In this study, we documented bleaching prevalence and recovery of host anemones and quantified changes in anemonefish abundance at two coral reefs in Singapore during and after the 2016 mass bleaching event. Of the 260 host anemones surveyed, 16% were bleached in July 2016. All Entacmaea quadricolor bleached, in contrast to Heteractis magnifica (1%) and Stichodactyla mertensii (0%). Five months after the warming event, the bleached E. quadricolor had significant size reductions at both sites despite 10% of them regaining pigmentation. In March 2017, recovery rates of E. quadricolor significantly differed between the study sites. Recovered host anemones increased in size while the bleached ones remained the same or continued shrinking. The between-site differences in recovery of bleached E. quadricolor influenced the abundance of associated Amphiprion frenatus, highlighting the importance of bleaching status and associated host anemone size in supporting viable anemonefish populations. Our study represents the first quantitative assessment of anemone bleaching and post-bleaching recovery in Southeast Asia. Considering the increasing frequency and severity of extreme warming events, our findings stress an urgent need to understand climate change impacts on non-scleractinian host organisms and their associates to implement effective management and enhance reef biodiversity conservation.
... Over the past few decades, advances in technology have increased the demand by home aquarists for organisms such as corals, corallimorpharians, and sea anemones that were previously difficult to maintain. Although these species contribute to greater appreciation and understanding of reef ecosystems in more than two million homes and public aquaria worldwide, their collection can degrade reef health through loss of biodiversity (Wabnitz et al. 2003;Thornhill 2012) and overfishing (Shuman et al. 2005;Scott and Baird 2015). This is particularly challenging for longlived species such as some sea anemones, whose populations are unlikely to recover from overcollection (Gasparini et al. 2005). ...
The marine aquarium trade in the United States operates primarily in Florida, and though the trade’s effects on many marine taxa are largely unknown, local declines have been observed for some harvested species. To reverse local declines in the abundance of the giant Caribbean sea anemone Condylactis gigantea, state managers prohibited harvest of this popular aquarium organism in late 2012. To assess the recovery of C. gigantea following the moratorium, we monitored relative abundance at 45 fixed locations in South Florida from 2013 to 2016. Seventeen of the sites were locations provided to us by commercial aquarium-trade collectors. The remaining sites were locations at which C. gigantea was presumably not being exploited. We found increased densities at only 4 of those 17 sites, while densities at the remaining sites remained unchanged. We also examined genome-wide single nucleotide polymorphism data to assess genetic diversity and population structure of 82 individuals from seven locations (three collection and four non-collection locations) across South Florida. Observed genetic diversity was comparable in all locations. But the location in the eastern Gulf of Mexico showed a significant FIS value, suggesting inbreeding that might be attributed to a small number of occupants. Condylactis gigantea is generally well mixed across South Florida, though a relatively weak pattern of genetic differentiation was detected. These results suggest limited reproductive success and dispersal that is restricted by hydrological and geographical barriers. We highlight the importance of periodic population and genetic monitoring to assess changes in relative abundance and genetic diversity.
... Most commonly, fish are collected via SCUBA using hand nets and barrier nets that reduce physical impact and stress to the fish. Yet, even with these controls in place, many populations are still declining (Jones et al. 2008;Frisch et al. 2009;Scott and Baird 2015). As an economically wealthy country, Australia should be leading the conservation management strategies for both conservation aquaculture and collection and import of aquarium species from the wild. ...
... As reflected by our findings, a sea anemone's ability to undergo asexual reproduction is species-specific and dependant on the ecological conditions found at each habitat throughout a particular species' range (Sebens, 1980). In general, clusters of H. magnifica and E. quadricolor appear to be common (Brolund et al., 2004;Richardson, Harriott, & Harrison, 1997;Scott & Baird, 2015), and this seems to be consistent with our results in terms of proportions of clones found. Neither asexual reproduction nor clusters of several individuals have been documented before in S. mertensii. ...
Aim
The mutualistic relationship between anemones and anemonefishes is one of the most iconic examples of symbiosis. However, while anemonefishes have been extensively studied in terms of genetic connectivity, such information is lacking entirely for host sea anemones. Here, we provide the first information on the broad‐scale population structure and phylogeographical patterns of three species of host sea anemone, Heteractis magnifica, Stichodactyla mertensii and Entacmaea quadricolor . We evaluate if there is concordance in genetic structure across several distinct biogeographical areas within the Indo‐Pacific region and to what extent the observed patterns may concur with those found for anemonefishes.
Location
Indo‐Pacific, including the Red Sea.
Taxon
Heteractis magnifica , S. mertensii and E. quadricolor
Methods
Microsatellite markers and a combination of statistical methods including Bayesian clustering, isolation by distance (IBD), analysis of molecular variance (AMOVA) and principal components analysis (PCA) were used to determine population structure. The congruence among distance matrices (CADM) method was used to assess similarity in spatial genetic patterns among species.
Results
Significant population structure was identified in the three host anemone species. Each species is likely composed of at least two genetic clusters corresponding to two biogeographical regions, the Red Sea and the rest of the Indo‐Pacific. Two of the three anemone species seem to be experiencing admixture where the two main clusters overlap (the Maldives). IBD analyses in the Red Sea revealed differences in gene flow among species, suggesting more limited dispersal potential for E. quadricolor than for S. mertensii and H. magnifica . Clonality is documented in S. mertensii for the first time.
Main conclusions
This research documents the genetic population structure for three ecologically important host sea anemones across the Indo‐Pacific and provides valuable insights regarding their biogeography and evolution. Specifically, we found high levels of genetic divergence between populations across different biogeographical regions, suggesting different evolutionary lineages within species. At the same time, common geographical overlap of population structures suggests similar evolutionary histories among all three species. Interestingly, the observed patterns are congruent to some extent with structure reported for several anemonefish species, reflecting their close ecological association.
... Host anemones are typically rare on reefs (Dunn, 1981;Chadwick & Arvedlund, 2005;Hobbs et al., 2013;Scott & Baird, 2014) and are currently sourced entirely from the wild. High levels of harvesting from limited extraction areas have caused localized depletions (Edwards & Shepherd, 1992;Shuman et al., 2005;Madduppa et al., 2014). ...
Coral reef degradation worldwide and the concomitant increasing demand for corals to supply the marine ornamental trade have been driving the growing interest for coral aquaculture. Captive breeding and propagation of corals among aquarium hobbyists and public aquariums is a well-known and established activity. In contrast, the scientific community has poorly explored coral production methods. Nevertheless, research on coral biology has dramatically increased in the past decades and resulted in numerous scientific studies that are highly relevant to further advance coral aquaculture. Here we provide an overview of coral aquaculture with particular emphasis on ex situ production methods. A comprehensive review of current asexual and sexual propagation techniques is provided, together with qualitative aspects of corals, such as coral shape and coloration, and quantitative production parameters, such as growth and volumetric productivity. Finally, we thoroughly discuss how the manipulation of abiotic and biotic conditions can maximize coral quality and volumetric productivity.
... Additionally, a rise in diving tourism and divers physically damaging corals has negatively impacted the coral reefs (Zakai and Chadwick-Furman 2002). Restoration efforts of rearing A. bicinctus or producing host anemones in captivity with the intent of releasing them onto reefs (Maroz and Fishelson 1997;Scott and Baird 2015) do not address the reason for the decline and hence may not prove successful in the long term. Future studies and management efforts should focus on deciphering the causes of the host anemones' demise, potentially eliminating these effects and thereby enabling the recovery of the host anemones E. quadricolor and H. crispa. ...
Anemonefishes’ obligatory mutualism with sea anemones dictates their occurrence in marine habitats. We examined whether the spatial distribution, number, and size of the host anemones Heteractis crispa and Entacmaea quadricolor affected the settlement, habitat usage, and survival of the two-band anemonefish, Amphiprion bicinctus. In a 200 × 50 m study site off the coast of Israel in the Gulf of Eilat, we followed the fish and anemone populations initially in 13 censuses from October 1996 to August 1997 and follow-up censuses from 1998 to 2015. Based on size, anemonefish were categorized as adults, juveniles, or settlers. Settlers tended to cluster together but displayed significantly dispersed distributions in relation to adult individual fish and breeding pairs. Adult and juvenile anemonefish associated more with, and exhibited higher survival in, E. quadricolor. Settlers primarily inhabited H. crispa, with similar survival rates in the two anemone species. H. crispa was less occupied compared to E. quadricolor, but 95 % of the 233 anemones hosted fish during at least one census. From 1997 to 2015, anemone and anemonefish numbers plummeted by 86 % and 74 %, respectively. In 2015, all 27 remaining anemones were occupied, with most E. quadricolor inhabited by adults. The anemones left at the study site, on average, hosted more fish per anemone than those in the original population. This saturated habitat could hinder new anemonefish individuals from settling. These results indicate that if the anemone population does not recover, the anemonefish could face local extinction.
... This is combated by weak governance capacity in major source countries such as the Philippines and Indonesia and high international demand that offers few incentives to strengthen trade policies or management practices. Even in some of the best-managed reef areas of the world, such as the Great Barrier Reef, where quota restrictions, voluntary stewardship agreements and notake zones are implemented, populations of both anemone and anemonefi shes are still declining in some areas (Jones et al. 2008 ;Frisch and Hobbs 2009 ;Scott and Baird 2014 ). ...
Sea anemones are amongst the most venomous organisms on earth and yet there are species of fish and crustacea that are known to tolerate anemone venoms and live in association with them in a mutually beneficial relationship. One of natures most compelling displays of symbiotic behavior is found in the relationship between anemonefish and their sea anemone host. This relationship was first described more than a century ago and despite it being widely studied since, our understanding of the evolution of the relationship and the mechanisms and behaviors involved remains shrouded in mystery. Anemonefish (Family: Pomacentridae) comprise of a distinct group of 28 species that are able to live within sea anemones. Despite the large diversity of anemones in the tropics, only ten species are suitable as hosts for anemonefish. Within these species, only certain pairs of anemone and anemonefish are compatible and found in the wild together. This relationship is obligatory for the fish and in some cases for the anemone, meaning that the symbionts are entirely or heavily dependent on each other for survival. Symbioses between the two groups provide the following benefits: mutual protection from predators, an exchange of nutrients, improved reproductive and lifetime fitness. While past studies have explored the different patterns of host species that fish use and multiple authors have examined the mechanisms involved in protecting fish from anemone venom, how fish acquire immunity from the anemone’s stinging tentacles and why only certain anemone species are found associated with some anemonefish more often than others still remains uncertain.
... Amphiprion clarkii was the only species that spent equal time in cues from unbleached or bleached hosts versus seawater. Because host anemones are typically rare on reefs [20,[46][47][48][49], anemonefishes have relatively short pelagic larval durations of 7-22 days [50][51][52], and predation pressure is likely to be high during this time; settling on the first host encountered, even if bleached, may be beneficial as rejecting bleached habitat may mean that settlement does not occur. Our study provides laboratory-based comparative observations and insights into how anemonefishes may respond to bleaching, which are further supported by field observations, as Saenz-Agudelo et al. [19] found no evidence of A. polymnus larvae avoiding bleached anemones in the field. ...
Understanding how bleaching impacts the settlement of symbiotic habitat specialists and whether there is flexibility in settlement choices with regard to habitat quality is essential given our changing climate. We used five anemonefishes (Amphiprion clarkii, Amphiprion latezonatus, Amphiprion ocellaris, Amphiprion percula and Premnas biaculeatus) and three host sea anemones (Entacmaea quadricolor, Heteractis crispa and Heteractis magnifica) in pairedchoice flume experiments to determine whether habitat naive juveniles have the olfactory capabilities to distinguish between unbleached and bleached hosts, and how this may affect settlement decisions. All anemonefishes were able to distinguish between bleached and unbleached hosts, and responded only to chemical cues from species-specific host anemones irrespective of health status, indicating a lack of flexibility in host use. While bleached hosts were selected as habitat, this occurred only when unbleached options were unavailable, with the exception of A. latezonatus, which showed strong preferences for H. crispa regardless of health. This study highlights the potential deleterious indirect impacts of declining habitat quality during larval settlement in habitat specialists, which could be important in the field, given that bleaching events are becoming increasingly common. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
Sea Anemones that form an iconic association with anemonefishes are highly sought after by marine aquarists. Currently, no commercial culturing protocols have been established for these host anemones, and individuals are sourced from the wild, causing localized depletions in some areas of the Indo-Pacific. This chapter details the reproductive biology of sea anemones, and then outlines potential approaches to culturing host anemones, and future research and industry development needs. Characteristics that appear favorable for captive breeding through sexual reproduction include having predictable annual spawning seasons, releasing large numbers of broadcast spawned gametes that readily fertilize, and larvae with a relatively short planktonic period that settle onto a variety of substrata and require little feeding to optimize growth. Alternatively, propagation using fission, by natural or artificial means, could produce individuals throughout the year. Although, much work remains to be done, aquaculture is a possible solution for addressing concerns about overexploitation, and individuals could be used to supply the trade or restock depleted reefs.
THERE IS NONE -- this is a short note without abstract.
Between 1.5 and 2 million people worldwide are believed to keep marine aquaria. The trade which supplies this hobby with live marine animals is a global multi-million dollar industry, worth an estimated US$200-330 million annually, and operating throughout the tropics. Ornamental marine species (corals, other invertebrates and fish) are collected and transported mainly from Southeast Asia, but also increasingly from several island nations in the Indian and Pacific Oceans, to consumers in the main destination markets: the United States, the European Union (EU) and, to a lesser extent, Japan.
Very few of the species in trade are exploited directly for other purposes, and there is little doubt that aquarium animals are the highest value-added product that can be harvested from a coral reef. If managed sustainably, the trade could support jobs in predominantly rural, low-income coastal communities and so provide strong economic incentives for coral reef conservation in regions where other options for generating revenue are limited. However, damaging techniques occasionally used to collect the animals, possible over harvesting of some species and the high levels of mortality associated with inadequate handling and transport of sensitive living organisms undermine this potential, and continue to pose significant challenges to achieving sustainability. As a result the trade has seldom been free of controversy as traders try to generate a profit, conservationists try to avoid further decline in coral reefs also suffering from other pressures, and policy makers try to assemble a legislative framework that protects coral reefs without threatening a legitimate business activity or the incomes of communities engaged in aquarium fishing.
In the main, this debate has taken place without access to impartial and quantitative data on the trade and, with so many different viewpoints, achieving consensus on its impacts, and hence the identification of suitable responses, has been difficult. In 2000, the United Nations Environment Programme World Conservation Monitoring Centre (UNEP-WCMC), the Marine Aquarium Council
(MAC) and members of various aquarium trade associations
collaboration, to address this need for better information and created the Global Marine Aquarium Database (GMAD). Trade data have been obtained from wholesale exporters and importers of marine aquarium organisms, most often through copies of trade invoices, integrated and standardized into quantitative, species-specific information which has been placed in the public domain: www.unep-wcmc.org/marine/GMAD. Fifty eight companies, approximately one-fifth of the wholesalers in business, and four government management authorities have provided data to GMAD. In August 2003 the dataset contained 102,928 trade records (7.7 million imported and 9.4 million exported animals) covering a total of 2,393 species of fish, corals and invertebrates and spanning the years 1988 to 2003. These data have permitted the most accurate quantitative estimates to date of the size of the global trade in marine ornamental fish and corals, and the first ever estimates for invertebrates other than corals, a previously overlooked section of the industry.
FISH
A total of 1,471 species of fish are traded worldwide with the best estimate of annual global trade ranging between 20 and 24 million individuals. Damselfish (Pomacentridae) make up almost half of the trade, with species of angelfish (Pomacanthidae), surgeonfish (Acanthuridae), wrasses (Labridae), gobies (Gobiidae) and butterflyfish (Chaetodontidae) accounting for approximately another 25-30 per cent. The most traded species are the blue-green damselfish (Chromis viridis), the clown anemonefish (Amphiprion ocellaris), the whitetail dascyllus (Dascyllus aruanus), the sapphire devil (Chrysiptera cyanea) and the threespot dascyllus (Dascyllus trimaculatus). The ten most
traded species account for about 36 per cent of all fish traded for the years 1997 to 2002. Trade data, correlated with aquarium suitability information, indicate that two species known not to acclimatize well to aquarium conditions are nonetheless very commonly traded. They are the bluestreak cleaner wrasse (Labroides dimidiatus: GMAD records 87,000 worldwide imports of this species from 1997 to 2002) and the mandarin fish (Synchiropus splendidus: GMAD records 11,000 live individuals exported to the EU in the same period). Data further indicate that species characterized as ‘truly unsuitable’, mainly due to their restricted dietary requirements, such as the foureye butterflyfish (Chaetodon capistratus), the harlequin filefish (Oxymonacanthus longisrostris) and the Hawaiian cleaner wrasse (Labroides phtirophagus), are also commonly traded, albeit in lower numbers.
CORALS
A total of 140 species of stony coral, nearly all scleractinians, are traded worldwide, with the best estimate of annual global trade ranging between 11 and 12 million pieces. Although difficulties associated with accurate coral identification probably make species data less reliable for corals than for fish, it is clear that species in seven genera (Trachyphyllia, Euphyllia, Goniopora, Acropora, Plerogyra, Catalaphyllia) are the most popular, accounting for approximately 56 per cent of the live coral trade between 1988 and 2002. Sixty-one species of soft coral are also traded, amounting to close to 390,000 pieces per year. Sarcophyton spp. (leather/mushroom/ toadstool coral) and Dendronephthya spp. (carnation coral) are two of the most commonly traded species. However, whilst the biology of the former makes it a hardy, fast-growing and easily propagated species under
aquarium conditions, Dendronephthya spp. usually die within a few weeks, mainly due to the fact that they lack photosynthetic symbionts and rely on filtering particles and nutrients in the water column for food.
INVERTEBRATES
More than 500 species of invertebrates (other than corals) are traded as marine ornamentals, though the lack of a standard taxonomy makes it difficult to arrive at a precise figure. The best estimate of global annual trade ranges between 9 and 10 million animals, mostly molluscs, shrimps and anemones. Two groups of cleaner shrimp, Lysmata spp. and Stenopus spp., and a group of anemones, Heteractis spp., account for approximately 15 per cent of all invertebrates traded.
The relationship between characteristics of the reef environment and variations in the distribution and abundance of the anemonefishes Amphiprion akindynos and A. latezonatus was investigated at North Solitary Island, a sub-tropical rocky reef system on the east coast of Australia. During the summers of 1994 and 1995, fish densities and host sea-anemone cover were assessed on replicate 25 m transects at sites where host sea-anemones form semi-contiguous mats throughout the 6–21 m depth range. Multiple regression analyses indicated that environmental variables accounted for 65–71% and 61–80% of the variations in the number of A. akindynos and A. latezonatus among-sites, respectively. Among-habitat comparisons indicated that A. latezonatus densities were positively correlated with depth (r=0.45–0.90), whereas A. akindynos showed no consistent depth-related abundance patterns. Poor correlations (p>0.05) between the densities of each species on transect lines suggested that present-day competition was unlikely to determine the preference of A. latezonatus for deeper depths. Correlations between host sea-anemone cover and fish densities at the within-habitat (depth) scale were comparatively stronger than correlations at among-habitats in both species. These results suggest that among-habitat comparisons can confound finer scale fish-habitat associations within habitat (depth) zones. Evidence suggests that while sea-anemone cover does, to an extent, regulate the local ecology of anemonefishes, other factors are also likely to interact to limit their densities.
Global trade in marine ornamental species includes numerous countries; however, 80% of the trade involves exports from the Philippines and Indonesia to the USA. The worldwide import value of marine ornamentals is estimated at US$ 200–330 million annually. Recent concern regarding sustainability and environmental impacts on coral reefs where collection occurs has spurred debate as to how best to monitor, manage and regulate the industry. A certification programme proposed by the Marine Aquarium Council (MAC) has the potential to manage the trade efficiently by minimizing environmental impacts, thus continuing this important source of income for impoverished coastal villagers. The MAC Ecosystem and Fishery Management (EFM) Standard was established to protect fish stocks from overexploitation and will be the most difficult component of the certification programme to implement. Prerequisites for successful EFM in developing nations are local control over fisheries and accurate records to monitor catch. Collector logs were found to be a useful tool to monitor both catch per unit effort (CPUE) and catch composition from collection areas in the Philippines. Comparison of catch composition in two distinct regions of the Philippines indicated that one site was severely overfished while the other was moderately overfished. The Collection Area Management Plan required by the MAC certification programme, combined with the current legal framework in the Philippines allowing for local jurisdiction of reef resources, has the potential to prevent further overfishing in the latter region. Until sufficient ecological data can be obtained, CPUE can provide an effective means to monitor and manage the fishery within the framework of the MAC certification programme. Despite effective management plans in source nations, legislation in receiving nations may be required to help stimulate a strong market demand for certified ornamentals if the MAC certification programme is to be successful.
Anemonefishes and their host sea anemones are iconic inhabitants of coral reef ecosystems. While studies have documented their abundance in shallow-water reef habitats in parts of the Indo-Pacific, none have examined these species on mesophotic reefs. In this study, we used autonomous underwater vehicle imagery to examine the abundance and diversity of anemones and anemonefishes at Viper Reef and Hydrographers Passage in the central Great Barrier Reef at depths between 50 and 65 m. A total of 37 host sea anemones (31 Entacmaea quadricolor and 6 Heteractis crispa) and 24 anemonefishes (23 Amphiprion akindynos and 1 A. perideraion) were observed. Densities were highest at Viper Reef, with 8.48 E. quadricolor and A. akindynos per 100 m2 of reef substratum. These results support the hypothesis that mesophotic reefs have many species common to shallow-water coral reefs and that many taxa may occur at depths greater than currently recognised.
Rising sea temperatures are causing significant destruction to coral reef ecosystems due to coral mortality from thermally-induced bleaching (loss of symbiotic algae and/or their photosynthetic pigments). Although bleaching has been intensively studied in corals, little is known about the causes and consequences of bleaching in other tropical symbiotic organisms.
This study used underwater visual surveys to investigate bleaching in the 10 species of anemones that host anemonefishes. Bleaching was confirmed in seven anemone species (with anecdotal reports of bleaching in the other three species) at 10 of 19 survey locations spanning the Indo-Pacific and Red Sea, indicating that anemone bleaching is taxonomically and geographically widespread. In total, bleaching was observed in 490 of the 13,896 surveyed anemones (3.5%); however, this percentage was much higher (19-100%) during five major bleaching events that were associated with periods of elevated water temperatures and coral bleaching. There was considerable spatial variation in anemone bleaching during most of these events, suggesting that certain sites and deeper waters might act as refuges. Susceptibility to bleaching varied between species, and in some species, bleaching caused reductions in size and abundance.
Anemones are long-lived with low natural mortality, which makes them particularly vulnerable to predicted increases in severity and frequency of bleaching events. Population viability will be severely compromised if anemones and their symbionts cannot acclimate or adapt to rising sea temperatures. Anemone bleaching also has negative effects to other species, particularly those that have an obligate relationship with anemones. These effects include reductions in abundance and reproductive output of anemonefishes. Therefore, the future of these iconic and commercially valuable coral reef fishes is inextricably linked to the ability of host anemones to cope with rising sea temperatures associated with climate change.
Five of the 10 known Indo-Pacific giant anemone species were recorded on
subtidal reefs within the eastern Australian subtropics (26°37′S to
30°56′S) during surveys between 1993 and 1995. Giant anemones had a
patchy distribution among the 30 localities sampled, and species richness did
not display any latitudinal trends within this province. Spatial distribution
patterns and abundance of anemones were assessed from total counts and from
line-intercept and belt transects. Anemone abundance was significantly higher
on reefs to the leeward of the prevailing swell than on more exposed sites, at
Julian Rocks and North Solitary Island, northern NSW. Significant reductions
in anemone cover were detected among years within shallow reefal sites at
North Solitary Island, coinciding with two major storm events. The abundance
of the widespread Entacmaea quadricolor at North
Solitary Island was the highest reported worldwide. Significant differences
were detected between two morphological types of
E. quadricolor in terms of microhabitat type, oral disk
size and spatial distribution patterns. Important factors influencing the
distribution, abundance and spatial patterns of giant anemones over both large
and localized spatial scales appear to be water temperature, wave disturbance
and water depth.
The Heteractis
magnifica assemblage at the tip of the Sinai Peninsula was examined. The actinian size, location, and number of resident anemonefishes were recorded. The anemones were found at depths down to approximately 40 m and the sizes of clustering H.
magnifica and clusters were positively correlated with depth. The shallow waters of the anemone assemblage contained few mainly small, solitary actinians. There seemed to be a tendency for solitary actinians to cluster once they reached a certain size-range. The resident anemonefishes Amphiprion
bicinctus and Dascyllus
trimaculatus were present in very large numbers (approximately 250 and 1800 respectively) and the A.
bicinctus home range size was positively correlated with depth.
As the sea anemones, Entacmaea quadricolor and Heteractis crispa, provide essential habitat for obligate symbiotic anemonefish, knowledge of their reproductive biology is crucial to their effective management and conservation. This paper provides the first detailed information on the spawning times, behaviour and mode of gamete release for these host anemone species. Anemones were collected from subtropical reefs in the Solitary Islands Marine Park, eastern Australia, and monitored in outdoor flow-through seawater tanks from 2003 to 2005. Sexually reproductive anemones were either male or female, releasing their gametes into the water column for external fertilisation and development. Spawning of both sexes was predominately synchronous and was restricted to a few nights each year during the austral summer and autumn. Males generally began to release gametes prior to females, suggesting that sperm or some associated product may trigger the females to spawn. Sperm were commonly released in milky white streams or clouds, whereas eggs were released singly or in large masses. Reproductive seasonality and synchrony of gamete release suggests that spawning in both species is coordinated by similar responses of individuals to a range of environmental factors such as seawater temperature, photoperiod and lunar cycles. Incorporating knowledge of the sexual reproductive biology of host sea anemones into management and conservation programs could help ensure the viability of their populations and their resident anemonefish.
The 25 species ofAmphiprion and one ofPremnas (family Pomacentridae) are obligate symbionts of 10 species of facultatively symbiotic sea anemones. Throughout the tropical
Indo-West Pacific range of the relationship, a fish species inhabits only certain of the hosts potentially available to it.
This specificity is due to the fishes. Five fishes occupy six sea anemone species at Lizard Island, Great Barrier Reef, Australia.Entacmaea quadricolor harborsP. biaculeatus, A. melanopus andA. akindynos. Adults ofPremnas occur deeper than about 3 m in large, primarily solitary actinians; juveniles may occupy peripheral members ofEntacmaea clones in shallow water. Specimens ofA. melanopus live exclusively in clonal anemones, which are found no deeper than 3 m. Most individuals ofA. akindynos inEntacmaea are juveniles, occurring shallow and deep, in solitary anemones or at the margins of clones. Interspecific as well as intraspecific
social control of growth may be responsible for keeping fish small at clone fringes. Conspicuous specimens ofE. quadricolor depend upon their anemonefish to survive. Actinians cleared of symbionts disappeared within 24 h, probably having been eaten
by reef fishes.Entacmaea, the most abundant and widespread host actinian at Lizard Island and throughout the range of the association, is also arguably
the most attractive to anemonefishes. I believe its vulnerability to predation was a factor in its evolving whatever makes
it desirable to fishes. Experimental transfers pitted fish of one species against those of another, controlling for ecophenotype
of host, and sex, size and number of fish. Competitive superiority was in the same order as abundance and over-all host specificity:P. biaculeatus, A. melanopus, A. akindynos. At least three factors are necessary to explain patterns of species specificity - innate or learned host preference, competition,
and stochastic processes.
Social structure, growth and reproductive experience of a protandrous anemonefish,Amphiprion frenatus, were investigated on a coral reef in Okinawa, Japan. In a 67 m × 334 m study area, 24 breeding groups, 10 nonbreeding groups
and 2 groups of unknown breeding experience were found around isolated sea anemones. One group usually consisted of 2 or 3
fish. The female in a breeding group was larger than not only her mate but also all males in other breeding groups. The body
size and gonadal state of the largest individual in a nonbreeding group were intermediate between the female and male in a
breeding group. In both breeding and nonbreeding groups, the largest fish retarded growth of the second largest. After the
disappearance or removal of females, their mates took more than 1.5 years to attain the minimum functional female size (about
75 mm in standard length). This delayed sex change can be attributed to strong growth suppression by the female.
Tropical marine ornamentals comprise an increasingly important fishery worldwide. Although the potential for overexploitation
of marine ornamentals is great, few studies have addressed the population-level impacts of ornamental exploitation and few
ornamental fisheries are managed. Analysis of catch records obtained from collectors over a four-month period in the vicinity
of Cebu, Philippines, showed that anemonefish and anemones comprised close to 60% of the total catch. Underwater visual census
surveys revealed that both anemone and anemonefish densities were significantly lower in exploited areas than in protected
areas. The low density of anemones on exploited reefs accounted for over 80% of the reduced density of anemonefish at those
sites. There were similar numbers of anemonefish per unit area of anemone in protected and exploited sites; however, biomass
of anemonefish per unit area of anemone was lower in exploited areas. Reduction of anemone removals is recommended to support
the sustainable harvest of anemonefish from this region.
The symbiosis between giant sea anemones and anemonefish on coral reefs is well known, but little information exists on impacts
of this interaction on the sea anemone host. On a coral reef at Eilat, northern Red Sea, individuals of the sea anemone Entacmaea quadricolor that possessed endemic anemonefish Amphiprion bicinctus expanded their tentacles significantly more frequently than did those lacking anemonefish. When anemonefish were experimentally
removed, sea anemone hosts contracted partially. Within 1–4 h in most cases, individuals of the butterflyfish Chaetodon fasciatus arrived and attacked the sea anemones, causing them to contract completely into reef holes. Upon the experimental return
of anemonefish, the anemone hosts re-expanded. The long-term growth rate and survival of the sea anemones depended on the
size and number of their anemonefish. Over several years, sea anemones possessing small or no fish exhibited negative growth
(shrinkage) and eventually disappeared, while those with at least one large fish survived and grew. We conclude that host
sea anemones sense the presence of symbiotic anemonefish via chemical and/or mechanical cues, and react by altering their
expansion behavior. Host sea anemones that lack anemonefish large enough to defend them against predation may remain contracted
in reef holes, unable to feed or expose their tentacles for photosynthesis, resulting in their shrinkage and eventual death.
Asterisks (*...*) surround words or phrases that are to be italicized. The 26 species of anemonefishes (or clownfishes: *Amphiprion* and *Premnas*) are obligate symbionts of 10 species of sea anemones. The fish are unaffected by actinian nematocysts because of their mucus coating; whether the mucus originates with fish, anemone, or some combination has yet to be resolved. The source of their protection may bear on what happens when a post-larval fish first encounters an actinian. There is conflicting evidence about whether the fish displays acclimation behavior - then or ever. This may differ with species of both fish and anemone. Indeed, not all combinations of species interact identically, so data from one species pair may not be generalizable. An obvious manifestation of such differences is that only some combinations of species exist in nature. This specificity has at least four components: conditioned or innate preferences by the fish (the more motile and shorter-lived partner, and therefore responsible for the pattern), environmental requirements, competition by fish for hosts, and chance. One benefit of the symbiosis to the fish is obvious:its major source of protection is its anemone, which forms the core of its territory. The symbiosis has commonly been regarded as facultative for actinians. However, in at least some species, anemonefish provide protection against predatory fishes (especially chaetodontids) in the short term. Ultimately, their presence may have permitted evolution of the widely flared oral disc incapable of retraction that is characteristic of many host actinians. This unusual anatomy produces an enormous surface area to intercept light, upon which zooxanthellae depend. The intimacy of this three-way symbiosis invites investigation of the degree to which the actinians depend on their algae for fixed carbon and their fish for nitrogen and possibly other nutrients.
Eighteen species of Actiniaria and four of Corallimorpharia have been identified from waters less than 30 m deep in Madang Province. These include eight actinians host to nine species of anemonefishes.
The interaction structure of mutualistic relationships, in terms of relative specialization of the partners, is important to understanding their ecology and evolution. Analyses of the mutualistic interaction between anemonefish and their host sea anemones show that the relationship is highly nested in structure, generalist species interacting with one another and specialist species interacting mainly with generalists. This supports the hypothesis that the configuration of mutualistic interactions will tend towards nestedness. In this case, the structure of the interaction is at a much larger scale than previously hypothesized, across more than 180 degrees of longitude and some 60 degrees of latitude, probably owing to the pelagic dispersal capabilities of these species in a marine environment. Additionally, we found weak support for the hypothesis that geographically widespread species should be more generalized in their interactions than species with small ranges. This study extends understanding of the structure of mutualistic relationships into previously unexplored taxonomic and physical realms, and suggests how nestedness analysis can be applied to the conservation of obligate species interactions.
Understanding the population dynamics of host sea anemones and their symbiotic anemonefish is important given that pressures such as aquarium collecting and bleaching events are adversely impacting their abundance in some Indo–Pacific locations. We examined long-term trends in anemone and anemonefish abundance at four sites within a ‘no-take’ zone at North Solitary Island, Australia, by comparing data from 2008 to surveys done in 1994 and 1995. Species richness was stable, comprising two anemones,Entacmaea quadricolor and Heteractis crispa, and three anemonefishes, Amphiprion akindynos, A. latezonatus, and A. melanopus. In 2008, densities of the most abundant species, E. quadricolor and A. akindynos, were substantially higher than previously recorded, with increases of up to 532% and 133%, respectively. There was a strong relationship between A. akindynos densities and anemone cover, whereasA. latezonatus had higher densities in deeper waters. Densities of this species remained similar over time, although there was a decline at one site. Heteractis crispa and A. melanopus were found in comparatively low numbers. Potential reasons for the overall increase in abundance include: protection from severe swell events, the lack of major bleaching events, the ability of E. quadricolor to reproduce rapidly by asexual reproduction, and the increasing duration of marine park protection.
Recent studies on the reproductive behavior of members of the anemonefish genus Amphiprion strongly support the hypothesis that low population density, unpredictable distribution of host anemones, and increased risks from predation due to movements away from anemones have resulted in socially controlled protrandry as the reproductive strategy of anemonefishes. Tropical anemonefishes usually live around isolated anemones in social groups composed of a stable monogamous pair and from one to three ambisexual subadults or juveniles.Amphiprion clarkii at Miyake-jima, in the warm temperate waters of southern Japan, shows many differences in behavior when compared to conspecifics and other anemonefishes from the tropics. These differences include (1) clustering behavior, (2) social groupings of more than two adults, (3) lengthy travel between anemones, (4) displacement of territorial adults by invading adults from other anemones, (5) conspicuous sexual dichromatism, (6) relatively unstable monogamous pairs, (7) occasional polygamy, (8) comparatively high fecundity, and (9) short, intense breeding seasons. These differences are attributed to ecological parameters imposed by temperate waters, including reduced predator pressures, large clusters of sea anemones, and cold winter water temperatures.
Export of aquarium-fish from the Maldives began in 1980 and in 1989 almost 54,000 marine fishes, worth approximately US$ 130,000, were exported. The collection of aquarium species is confined to a relatively small area around the capital island, Malé. Estimates of annual exports of 95 species were obtained by examining packing-lists held by Maldivian Customs. In parallel, the population densities of about 70 aquarium-fish species were estimated by visual assessment. Using a number of assumptions, potential (maximum sustainable) yields for 65 of these species — those for which export data were available — were estimated for the area (530 km ² ) within a 13-km radius (one hour's journey by local boat) of Malé.
For 27 species there were some reasons for concern about the levels of exploitation, although only 12 of these species appeared to be ‘at risk’ in 1986 (the year of highest exploitation). If the assumptions made in estimating potential sustainable yields were valid, these 12 aquarium-fish species were being overexploited or exploited at levels close to maximum sustainable yields. Should the trade expand threefold, a further 12 species are considered to be potentially at risk of overexploitation. Two species of butterflyfish, Chaetodon meyeri and C. triangulum , which feed exclusively on coral polyps and generally die in captivity after a short time, were being exported in significant numbers. Both clownfishes ( Amphiprion spp.) and their host sea-anemones were being heavily exploited. Because of the symbiotic relationship between these fishes and their anemone homes, this group may be particularly susceptible to overexploitation.
Damage to branching corals may result from the collection of specimens of Dascyllus aruanus , which shelter within them. With many thousands of individuals of this species being exported each year, this could represent considerable collateral coral damage. Although levels of exploitation of ‘cleaner wrasses’ ( Labroides bicolor and L. dimidiatus ) appear well below potentially sustainable ones, it is unclear whether the health of reef fishes might locally be adversely affected in heavily exploited areas.
Monitoring and regulation of the aquarium-fish trade is discussed, together with the need for collection of catch statistics by those involved in the trade. The importance of regulation of collection techniques, of standards of facilities, and of satisfactory packaging of fish for export, is stressed. If more accurate estimates of sustainable yields are to be obtained, there needs to be monitoring of populations of key aquarium-fish species in designated collecting areas where exploitation levels are known. Until such estimates become available, the cautious approach adopted in the Maldives to estimate yields and set species-based quotas will, it is hoped, prevent local overexploitation.
Patterns of distribution and abundance of giant sea anemones and anemonefish were compared among coral reefs along the coastline of Sinai in the northern Red Sea. The sea anemones varied widely in abundance between reef areas containing different habitat types. They were rare on steep reef slopes with abundant coral cover (=low-density anemone sites, 0.09–0.68 anemones per 1000 m2 of reef area), but were common at a site containing patch reefs interspersed with sand (=high-density anemone site, 6.00–8.11 anemones per 1000 m2). Distributions of the endemic two-band anemonefish (Amphiprion
bicinctus) varied significantly between the two main host anemone species. At the high-density site, individuals of the sea anemone Heteractis
crispa either did not contain anemonefish, or were occupied by single juvenile fish as shown in previous studies. At low-density sites H.
crispa usually hosted clusters of juvenile anemonefish. In contrast, individuals of the sea anemone Entacmaea
quadricolor hosted either single adult fish (high-density site) or pairs of breeding adults (low-density sites), frequently in addition to some juvenile fish. Mechanisms that prevent anemonefish from reaching adult size and forming breeding pairs in H.
crispa may include high fish mortality above a size threshold because this host cannot adequately protect them from predation when they become large, active emigration of fish to E.
quadricolor as described in previous reports, and/or environmentally-controlled cessation of fish growth. We conclude that in the northern Red Sea, individuals of H.
crispa potentially serve as nurseries for anemonefish.
According to meta‐population models, a superior competitor and a superior disperser can coexist in a patchy environment. The two anemonefishes, a large aggressive Amphiprion clarkii Bennett and a small less‐aggressive A. perideraion Bleeker, use the same host anemone Heteractis crispa Ehrenberg on a coral reef, Okinawa, Japan, where most of the hosts disappeared after the coral bleaching in 1998. Their microhabitat (host) use and coexistence, and the quality and quantity of microhabitats were investigated in 1988, 1989, 1999 and 2000 on the coral reef. Their interspecific interaction was also examined.
Before the habitat destruction, the two species coexisted. Although A. clarkii was behaviourally dominant over A. perideraion in a cohabiting group, A. perideraion was a superior competitor in terms of site displacement, because A. perideraion could displace a microhabitat. Adult A. clarkii emigrated from a cohabiting group probably due to the high cost of interactions with adult A. perideraion . Although it is easier to defend a small area for a larger species, sharing a host with adult A. perideraion may not pay for A. clarkii because A. clarkii needs a larger area.
A. clarkii was not only a superior disperser, which was able to find a vacated host, but also a pioneer species that was able to use newly settled small hosts. Larval A. clarkii settled on such a small host because they were able to move to larger hosts for future reproduction, while A. perideraion did not settle on a small host because of low mobility after settlement. Microhabitat (host) with various sizes might have promoted their coexistence.
After the habitat destruction, the superior competitor A. perideraion went extinct locally due probably to lack of small host utilization ability. The present study implies that the difference in body size between the two competitors plays an important role in their coexistence, because species with different body sizes can have different mobility and require different amounts of resources.
The breeding of the anemonefish,Amphiprion clarkii, and the settlement of larvae were observed in temperate Japan. Spawning had two peaks near the first and the third quarter
of the moon in 1983, but did not in 1984. The clutch size varied greatly during the breeding season, with a peak from the
second half of June to the second half of July. Adult fishes inhibited larval settlement. The proportion of disappeared 0-year
olds to the total was higher in 1984 than in 1983. This difference might be mainly due to the difference in the degree of
crowding in each sea anemone. The period of larval settlement closely paralleled the breeding season. The larvae settled abundantly
around the first quarter and the third quarter of the moon in 1983, and did from the third quarter to the first quarter in
1984. In both years, the number of settled larvae was more from the full moon to the new moon than the new moon to the full
moon. The daily pattern of larval settlement did not reflect that of breeding.
The region of Madang, Papua New Guinea, has the highest reported species diversity of both anemonefishes (nine species) and
their host anemones (ten species). To determine which factors may allow so many anemonefish species to coexist at this location,
we studied their patterns of distribution, abundance, and recruitment. Population surveys at three replicate reef sites within
four zones situated at varying distances from the mainland (nearshore, mid-lagoon, outer barrier, and offshore) indicated
that each species of host anemone and anemonefish lived within a particular range of zones. Each species of anemonefish lived
primarily with one species of host. Anemonefish species that lived with the same host species usually had different distribution
patterns among zones (e.g., Amphiprion percula occupied Heteractis magnifica in nearshore zones, while A. perideraion occupied H. magnifica in offshore zones). Monitoring of natural populations showed that there were few changes (losses or recruitment) in the number
or species of fishes associated with each individual anemone over periods ranging from 3 to 9 months. Recruitment was monitored
on anemones with and without residents (resident fishes were removed) within each of three zones (nearshore, mid-lagoon, outer
barrier). Significantly more anemonefishes recruited to anemones without resident fishes than to anemones with resident fishes.
Each anemonefish species recruited to particular host species and zones. The distribution and abundance of the recruits of
each fish species among zones were positively correlated with the distribution and abundance of resident fishes in the benthic
habitat. This suggests that the spatial patterns of recruitment among zones strongly determined the distribution and abundance
patterns of the benthic populations, and they were not the result of post-recruitment mortality or movement. Coexistence of
the nine anemonefish species on the limited anemone resource was considered possible because of niche differentiation (i.e.,
differences in host and habitat utilization among zones), and the ability of two small species (i.e., Amphiprion sandaracinos and A. leucokranos) to cohabit individual anemones with other anemonefish species.
Under the general heading of symbiosis, defined originally to mean a living together of two dissimilar species, exist the sub-categories of mutualism (where both partners benefit), commensalism (where one partner benefits and the other is neutral) and parasitism (where one partner benefits and the other is harmed). The sea anemone-fish (mainly of the genus Amphiprion) symbiosis has generally been considered to benefit only the fish, and thus has been called commensal in nature. Recent field and laboratory observations, however, suggest that this symbiosis more closely approaches mutualism in which both partners benefit to some degree. The fishes benefit by receiving protection from predators among the nematocyst-laden tentacles of the sea anemone host, perhaps by receiving some form of tactile stimulation, by being less susceptible to various diseases and by feeding on anemone tissue, prey, waste material and perhaps crustacean symbionts. The sea anemones benefit by receiving protection from various predators, removal of necrotic tissue, perhaps some form of tactile stimulation, removal of inorganic and organic material from on and around the anemone, possible removal of anemone parasites, and by being provided food by some species of Amphiprion.
Nine anemonefish species were reared in the laboratory, and individuals were released in the field (Lizard Island, Australia and Madang, Papua New Guinea) at different distances and orientations away from natural (anemone species the fishes are found with in nature) and unnatural species of host anemones. Experiments were conducted to examine factors that could affect the settlement behaviors of the fishes: current velocity, distance and orientation of the fishes to the anemones, chemical vs visual cues, and presence of conspecific or heterospecific fishes. The fishes were usually attracted toward natural host species of anemones but not towards unnatural host anemone species nor to pieces of dead coral. Host selection during settlement provided the best explanation for the host specificity patterns displayed by anemonefishes in nature. The fishes used chemical cues released from the anemones to identify and locate the appropriate host species and could effectively locate the anemones from a maximum distance of 8 m downstream. Fishes released upstream or to the side of anemones (where anemone chemicals were assumed to be reduced or absent) were much less successful in locating anemones. The ability of the fishes to locate natural host anemones was strongly reduced when there was no water current. The presence of resident anemonefishes on host species of anemones did not influence the attraction behavior of anemonefishes released downstream from the anemones. Once the released fishes got close to or entered the anemones, the resident fishes would generally bite and chase them until the recruits left the anemones. Most fishes were not stung upon initial contact with the anemones.
Coral reefs have been used by humans as recreation areas and as a source of food and other products for thousands of years. The effects of humans on coral reefs are not well understood, especially on a regional or global scale. A special survey protocol called “Reef Check” was designed to be used by volunteer recreational divers, trained and led by marine scientists, and based on the use of high value, easily identified indicator organisms. During a period of 2.5 months, a global survey of over 300 reefs in 31 countries and territories indicates that few reefs remain unaffected by man, even very remote sites. Overfishing has reduced fish and invertebrate indicator organisms to low levels at most reefs, including those within marine protected areas. The ratio of live to dead coral cover was higher in the Red Sea than in other regions, indicating that reef corals are in the best condition there. In future years, by increasing the number of reefs and the frequency of surveys, the Reef Check program could provide a valuable method to detect broad-brush changes on a local, regional and global scale, as well as increasing public support for coral reef conservation.
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