Thesis (M.Sc.). / Written for the Dept. of Biology. Title from title page of PDF (viewed 2008/07/24). Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 129-142). Also available on the World Wide Web.

The threespot damselfish, Stegastes planifrons, maintains individual territories that are clustered on coral patch reefs. My objective was to understand the effects of territory clustering on behavior and fitness. Fish with territories in the center of a cluster had (relative to edge fish): higher mating success (number of eggs), higher aggressive chase rates with conspecifics, lower chase rates to heterospecifics, lower overall chase rates, lower grazing rates by intruders, and smaller territories. Feeding rate, survivorship, and age at maturity did not vary with territory position. Therefore, central fish appeared to have higher fitness, which was probably related to the lower energetic costs of territory defense there. Center and edge territories differed in habitat complexity, and the density of potential algal competitors, egg predators, and various food and invertebrate species. These microhabitat features could provide different quality shelter, nest or feeding sites and thus might explain the positional differences in fitness. An experiment in which I changed the position of treatment fish from the center to the edge of a cluster, without altering microhabitat, showed that position per Se, and not microhabitat variation, caused the center-edge differences. Vacated space in the center of a cluster was fought over more vigorously and reoccuppied sooner than similar space on the edge. Settlement to one of two depopulated clusters was preferentially to the cluster center. These data indicated that threespots compete for the more desirable central positions. Therefore, these populations can be considered simultaneously recruitment limited (in terms of local population size) and resource limited (in terms of local reproductive output and perhaps global population size). Aggressive chases with conspecifics were lower on the cluster edge than at any distance toward the center, while chases to heterospecifics had the opposite pattern. The results of chases with conspecifics did not fit the predictions of the model by Stamps et al. (1987) . This discrepancy may be a result of habituation between territorial neighbors. / Graduation date: 1995

Little is known about the costs of relocating a territory into an established neighbourhood. In this study we investigated short-term costs of relocation in the longfin damselfish, Stegastes diencaeus, on a fringing reef in Barbados. Experimental removals of residents created vacancies, and focal observations over two days examined the intensity and duration of behavioural changes in the newcomers. Newcomers used smaller territories than original residents, and exhibited increased movement, increased agonistic behaviour and decreased foraging. The behavioural changes suggest that energetics are a major cost to relocation, but that opportunity costs, predation risk and injuries are also important. Differences between strangers and expanding neighbours support the concept of 'dear enemy' recognition, but familiarity does not influence the agonistic behaviour initiated by these newcomers. The costs reported here represent important limitations to the mobility of individuals and provide insights into the stability of fish territories.

No description available.

Thesis (M.S.)--Ohio University, August, 2003. / Title from PDF t.p. Includes bibliographical references (leaves 67-75)

Made available in DSpace on 2014-06-12T23:03:18Z (GMT). No. of bitstreams: 2 arquivo8367_1.pdf: 7600590 bytes, checksum: 0a180dbe6b6c60b9f0f5601ab51d1c62 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2004 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Apesar da reconhecida importância do ambiente recifal é consenso entre os cientistas de todo o mundo que estes ecossistemas estão atualmente sob forte pressão e em declínio. Uma parte vital do ecossistema recifal é constituída pela ictiofauna. Estima-se que de 30 a 40% dos peixes marinhos podem ser encontrados nos ambientes recifais. A família Pomacentridae ocupa lugar importante devido a grande abundância apresentada em número e espécies e por possuírem hábitos altamente especializados. Neste trabalho foram analisadas duas espécies do gênero Stegastes endêmicas do Brasil: S. rocasensis, com maior área de distribuição, ocorrendo no Atol das Rocas e no Arquipélago de Fernando de Noronha e Stegastes sanctipauli, que só ocorre no Arquipélago de São Pedro e São Paulo. A densidade, distribuição e tamanhos da população foram determinados através de censos visuais subaquáticos, além da relação entre as espécies estudadas com o substrato local. A cobertura do substrato foi estimada através do método Reef Check. Quando comparamos os dados de densidade com a caracterização do substrato deste estudo concluímos que a abundância destas espécies é fortemente influenciada tanto pela composição estrutural do ambiente como pela diversidade de cobertura. Estas duas variáveis combinadas poderiam ter capacidade de limitar o tamanho da população para estas espécies que possuem hábitos diretamente associados ao substrato. Para as duas espécies a idade foi determinada a partir da leitura de marcas de aposição em otólitos inteiros e seccionados. Os parâmetros de crescimento da curva de Von Bertalanffy foram calculados. Para S. rocasensis a idade variou entre zero e 13 anos. Para S. sanctipauli a idade variou entre zero e 15 anos. Apesar das espécies estudadas não ocorrerem em ambiente impactado com depleção de predadores, estas demonstraram alta longevidade, o que pode influenciar positivamente sua estabilidade e perpetuação mesmo sendo populações de áreas restritas. Assim poderíamos explicar a capacidade de peixes recifais endêmicos que mantêm suas populações com espécies muito abundantes e dominantes mesmo quando ocorrem em áreas restritas, como em ilhas oceânicas, ambientes fragmentados e áreas de proteção de pequeno tamanho

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.

No description available.

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.