Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 119-124).

published_or_final_version / Ecology and Biodiversity / Master / Master of Philosophy

Videotape and audio recordings of a patch reef in Ant Atoll, Pohnpei, Micronesia were analyzed for the presence of bioacoustic activity produced by species of the teleost family Pomacentridae. The acoustic parameters of fish calls were measured and then identified as belonging to either Amphiprion melanopus or Stegastes nigricans. Visual and statistical methods of analysis were combined to compare the calls of the two species and to test for measurable differences in the acoustic parameters of their calls. Soundscape data showed similar patterns to previously observed tropical reef environments. Fish produced single or multi-pulsed calls in the frequency range of 0-1000 Hz that were often accompanied by observable behaviors such as a chases and displays of dominance. Results indicated that the species on this atoll produce similar calls that cannot be distinguished using acoustic data alone. Visual confirmation was necessary for definitive identification of sound producers and in many cases was not possible beyond the family level. Implications for passive acoustic monitoring are that acoustic data collection alone may be able to capture fish abundance but may not be sufficient to fully capture species richness in regions where populations of closely related fish have similar signals.

There is much evidence supporting the idea that pelagic larvae of coral reef fishes are active participants in their dispersal and return to a reef, however, the mechanisms used to navigate are still uncertain. It has been proposed that sensory cues, such as hearing, play a role. Sound is a potentially important cue for organisms in marine environments, especially in noisy environments like coral reefs. Sensory organs, including otolithic organs, of most coral reef fish form within the first few days of life. The auditory brainstem response (ABR) technique was used to measure hearing on a wide size range of sergeant majors (Abudefduf saxatilis). Complete audiograms were measured for 32 fish ranging in size from 11-121 mm. Significant effects of standard length on hearing thresholds at 100 and 200 Hz were detected. At these lower frequencies, thresholds increased with an increase in size. All fish were most sensitive to the lower frequencies (100-400 Hz). The frequency range that fish could detect sounds was dependent upon the size of the fish; the larger fish (>50mm) were more likely to respond to higher frequencies (1000-1600 Hz). A. saxatilis have poor hearing sensitivity in comparison to audiograms of other hearing generalists including other species of Pomacentrids. Due to the high hearing thresholds found in this study in comparison to recorded ambient reef noise, it is unlikely that sound plays a significant role in the navigation of the pelagic larvae of sergeant majors to the return of the reef from large distances.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-02-16T13:02:43Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO_FELIPE_Biblioteca.pdf: 2170000 bytes, checksum: af1703db79d97fbe8ce2535a90aa2574 (MD5) / Made available in DSpace on 2017-02-16T13:02:43Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO_FELIPE_Biblioteca.pdf: 2170000 bytes, checksum: af1703db79d97fbe8ce2535a90aa2574 (MD5) Previous issue date: 2016-05-31 / CNPq / No Brasil os estudos um dos principais focos dos estudos etológicos com peixes recifais é a espécie Stegastes fuscus (Cuvier, 1830); a mais representativa em abundância e frequência nos recifes rasos de Pernambuco. Neste contexto, este estudo teve por objetivos; (1) descrever o repertório comportamental de S. fuscus, criando etogramas descritivos e ilustrados com todos os comportamentos observados, e (2) analisar o comportamento de defesa territorial da espécie. Dez horas de observações preliminares e 68h de observações ad libitum e animal focal, e 20h de experimento in situ foram realizadas nos recifes naturais da praia de Porto de Galinhas, Ipojuca. Três áreas foram escolhias por suas características diferentes: (1) ponto do Fundo Recifal, (2) ponto da Praia, (3) ponto do Topo Recifal. As observações geraram um etograma com nove categorias comportamentais motoras: natação, alimentação, defecação, limpeza de território, limpeza do corpo, saída do território, interação social, abrigo, agonístico; e duas sonoras: pop e burr. O ponto do fundo recifal foi o de menor densidade de S. fuscus, com 0,3 peixes/m², e onde se encontraram os maiores territórios (1,45 m² em média). Os maiores valores de densidade, cobertura e locas foram encontrados no ponto da Palythoa. As regressões obtidas para o comprimento dos indivíduos e as variáveis avaliadas mostraram tendência para a relação entre o comprimento dos indivíduos e o número de locas, no ponto do fundo. Provavelmente neste pontoo mais importante para os peixes é a presença de abrigo. Foram registrados peixes afastando-se quase 10 m de seus territórios. Pode-se afirmar que área de vida da espécie está associada ao ambiente ao redor. A taxa de alimentação diminuiu conforme aumentou o número de interações agonística. O número de atos alimentares por minuto só diminuiu de forma significativa quando houve mais de dois atos agonísticos. Este ponto representa um limiar que define até onde é vantajoso para o peixe manter a defesa de territórios. Durante as observações experimentaisforam identificados sete padrões de reação aos objetos. São elas: evitar, não interagir, observar e sair, observar e aproximar-se aos poucos, observar e examinar, observar e ameaçar com display, e observar e expulsar. As diferentes respostas demonstram como o comportamento territorialista da espécie está tão associado às variações individuais e às ambientais. O presente estudo identificou três padrões comportamentais que não foram descritos anteriormente em estudos comportamentais com a família Pomacentridae. / In Brazil the major focus of ethological studies on reef fishes is Stegastes fuscus (Cuvier, 1830); the most representative fish species in abundance and frequency in the shallow reefs of Pernambuco. In this context, this study aimed; (1) describe the behavioral repertoire of S. fuscus, creating descriptive and illustrated ethograms with all the observed behaviors, and (2) to analyze the territorial defense behavior of the species. Ten hours of preliminary observations, 68h of ad libitum and focal animal observations and 20h of in situ experiment were performed on the natural reefs of Porto de Galinhas, Ipojuca. Three areas were chosen by their different characteristics: (1) Reef bottom site, (2) Beach site, (3) Reef flat site. The observations resulted in an ethogram with nine motor behavioral categories: swimming, feeding, defecation, territory maintenance, chafe, leaving the territory, social interaction, shelter antagonistic; and 2 sound: pop and burr. The point of the reef bottom has the lowest density of S. fuscus, with 0.3 fish / m², and where the larger territories were found (1.45 m² on average). The highest density, coverage and hollows values were found at the reef flat. The regressions obtained for the length of the individuals and the variables evaluated tended to find a relationship between the length of individuals and the number of hollows the reef bottom. Probably it’s more important for the fish the presence of shelter. Fish were recorded almost 10 m away of their territories. The home range of the species is associated with the environment around. The feed rate decreased as the number of agonistic interactions increased. The number of feeding acts per minute only decreased significantly when there were more than two agonistic actions per minute. This point is a threshold that defines how far it is advantageous for the fish to keep the protection areas. During the experiment it were identified seven reaction patterns to objects. They are: prevent, not interact, observe and leave, observe and approach slowly, observe and examine, observe and frontal display, and observe and leave. The different responses demonstrate how territorial behavior of the species is associated with individual and environmental variations. This study identified three behavioral patterns that have not been described previously in behavioral studies with the Pomacentridae family.

This bachelor thesis was executed as a Minor Field Study (MFS) in Malolo Lailai Island, Fiji.The Minor Field Study was funded by the state agency Swedish International DevelopmentCooperation Agency (SIDA). The thesis was written during the spring of 2023 at the RoyalInstitute of Technology (KTH) in Stockholm and the project was created and executedtogether with the organisation Corals for Conservation (C4C) located in Fiji. Coral reefs around the world are degraded due to many different anthropogenic stressors,where climate change is a major one. This has affected the reefs in Fiji as sea temperaturesare rising which is causing corals to bleach. Efforts are being made to restore the reefs whichincludes outplanting and monitoring corals in degraded reefs. As conditions in the seaschange, corals are increasingly exposed to predators and disease. Against this backgroundthis project was created in order to see if outplanting corals inside or close to a Damselfish(Stegastes nigricans) territory makes any difference to the survival rate of the corals. Theresults show that corals outplanted outside of a Damselfish territory has a higher risk ofexposure to predators as well as foragers which leads to a lower survival rate. The conclusionthat was made was that planting corals inside of a Damselfish territory therefore increases thechances of corals surviving. / Detta kandidatexamensarbete har gjorts som en Minor Field Study (MFS) på Malolo LailaiIsland, Fiji. Arbetet har blivit finansierat av Styrelsen för internationellt utvecklingssamarbete(SIDA). Arbetet skrevs under våren 2023 på Kungliga Tekniska Högskolan (KTH) iStockholm och projektet är grundat och utfört tillsammans med organisationen Corals forConservation (C4C), beläget i Fiji. Hälsan hos korallrev runt om i världen försämras allt mer på grund av flera olika antropogenastressfaktorer såsom exempelvis klimatförändringar. Detta har påverkat reven runt om Fijinegativt på grund av ökade havstemperaturer som resulterar i att koraller bleks. Flertaletåtgärder har utförts för att restaurera de korallrev som degraderats där utplantering ochövervakning av koraller är ett exempel. När förhållandena i haven ändras blir korallernaalltmer utsatta för såväl ökade temperaturer som ökad mängd predatorer och sjukdomar. Medtanke på denna bakgrund har detta projekt skapats för att se om utplacering av koraller inutieller nära ett territorium av Damselfish (Stegastes nigricans) utgör någon skillnad förkorallers överlevnadschans. Resultaten har visat att koraller som blir planterade utanförDamselfish-territoriet löper större risk att påträffa både predatorer och betare vilket leder tillatt dess levnadschanser minskar. Slutsatsen som drogs var därför att utplantering av korallerinuti ett Damselfish-territorium ökar korallernas chanser för överlevnad.

Caribbean reef ecosystems have undergone major ecological changes in the last 30 – 40 years, with the result that ecological systems once dominated by structurally complex Acropora cervicornis and Montastraea annularis corals now consist mainly of flattened carbonate substrates with macroalgal overgrowth. A need for greater understanding of coral reef ecosystems is imperative if we are to attempt to conserve them. The threespot damselfish, Stegastes planifrons, is herbivorous damselfish species ubiquitous to Caribbean reefs, where it has been termed a keystone species. Aggressive in nature, S. planifrons defends territories of around 70 cm in diameter from other roving herbivorous fish and urchins, in apparent effort to maintain the algal resources therein for its own use. The predilection of Stegastes planifrons for basing its territories on the now Critically Endangered staghorn coral, Acropora cervicornis, and the Endangered boulder coral Montastraea annularis is well known, however the likely ecological implications of this fact have not been investigated. Using a combination of experimental and observational methodologies we examine the ecological implications of coral microhabitat choice and use by S. planifrons. We also assess the magnitude of the direct and indirect effects of S. planifrons’ territorial behaviour on macroalgal dynamics both within and outside of territory confines, at the reef-wide level. We find that coral microhabitat is a more important determinant of algal community structure than damselfish presence, and that this can be explained by a previously unrecognised effect of coral microhabitat on the grazing behaviour of roving herbivorous fishes - on which S. planifrons’ territorial behaviour has little effect. In a modification of the space availability hypothesis of Williams et al (2001) we suggest that Acropora cervicornis acts as a grazing fish „exclusion zone‟, and we further hypothesise that the existence of large stands of this coral prior to the Caribbean „phase shift‟ may have acted to concentrate the grazing pressure of excluded roving fish onto the remaining areas of the reef. We further hypothesise that the loss of such „exclusion zones‟ and accompanied effective dilution of grazing pressure may have been on a scale large enough to have been a significant underlying factor in the proliferation of macroalgae seen on modern day Caribbean reefs. In the absence of demonstrable direct or indirect effects on benthic algal communities we question the continued keystone status of S. planifrons, particularly since the status 6 was originally based on interference behaviour involving the important grazing urchin Diadema antillarum, which is now functionally absent from Caribbean reefs. Implications of the context-dependant nature of keystone status are also discussed. We find that the effect of S. planifrons on coral community may be more important than its effects on benthic algal community. In examining the factors involved in habitat coral choice we establish a significant preference for 100% live coral substrate over substrates with a supply of algal food. Territory selection was followed by a high rate of coral biting – a behaviour which has previously been shown to result in coral tissue death and the fast establishment of algal turf communities on which S. planifrons likes to feed (Kaufman 1977). We also demonstrate a novel and significant association between S. planifrons presence and disease incidence its primary habitat coral, the Critically Endangered staghorn coral Acropora cervicornis, and a significant correlation between areas of fish biting and the later onset of disease. Changes to the overall role of damselfish on today's Caribbean reefs are discussed in light of these insights.