Made available in DSpace on 2015-04-17T14:55:31Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2002627 bytes, checksum: 39d7a132e006887e0b60434c90f8a6dc (MD5) Previous issue date: 2013-03-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The abundance and ecological attributes, as behavior and reproduction, of reef fishes are usually influenced by variations in habitat structure, e.g. benthic cover and structural complexity. The preference for different habitats generally varies according to the ontogenetic stage, with juveniles generally concentrated in shallow waters and adults in deeper and away from the coast areas. Abudefduf saxatilis, the sergeant-major (Pomacentridae) is a reef fish widely distributed in coastal and oceanic reef habitats in the West Atlantic. In the small and remote St. Peter and St. Paul s Archipelago (SPSPA), located on the Mid Atlantic Ridge, the sergeant-major is one of the most abundant reef fish species. The sergeant-major population of the SPSPA is morphologically and genetically distinct from other populations in West Atlantic, suggesting low genetic connectivity and self-maintenance by local reproduction. The main objectives of this study are: 1) to describe the abundance and spatial distribution of the sergeant-majors from SPSPA (tidal pools and the islands inlet) and 2) to quantitatively characterize the reproductive ecology aspects of the species on site. Data on fish and nest abundance were collected using a stationary visual census methodology. Benthic complexity was measured using a rolling stick, at the inlet and the chain link method on tide pools. Benthic cover was estimated using photo-quadrats. Data on the reproductive behavior of male guardians and the nests individual monitoring were collected by the focal animal method and photographs, respectively. The smaller sergeant-majors representatives (<2 cm in total length, TL) were recorded exclusively in the tidal pools, predator-free environments that have been identified as potential nurseries for this species in the SPSPA. No significant influences were recorded on the complexity of the substrate in the abundance and distribution of sergeant-majors in tidal pools and little or no influence of benthic coverage. In the inlet, there was a positive relationship between A. saxatilis body size and depth, with individuals sized between 2-10 cm CT concentrated on shallower strata (0-10 m depth). Individuals among 10-20 cm CT switch to occupy depths below 10 m and suffered significant influence of complexity, suggesting greater need of refuge from predators. The density of A. saxatilis nests was lower in areas with higher abundance of Stegastes sanctipauli, a territorial Pomacentridae, abundant in the archipelago, suggesting possible negative interactions as competition for territory and optimal nesting sites. Places with higher densities of nests of A. saxatilis also had higher densities of the eggs' predator Halichoeres radiatus, suggesting aggregation of this predator in areas with a greater supply of eggs. The agonistic interactions between male guardian and nests invaders were more frequent in less accessible nests, probably due to greater difficulty on detecting intruders in these nests. Factors that negatively influenced the spawning success, i.e. proportion of eggs remaining over time, were the total agonistic interactions between males and invaders, total bites by male guardian in their own nest and guardian male's size. Depth was the only factor that positively influenced the spawning success. These last results suggest that larger males probably defend spawning that is more attractive to egg's predators and egg predation significantly influences the spawning success of A. saxatilis in SPSPA. Furthermore, if the male spends more time in nest defense, the chances of foraging in areas distant from the nest are smaller, being one of the most plausible explanations for the significant influence of filial cannibalism in spawning success. The higher reproductive success at greater depths may be related to the absence of competition with other abundant territorial damsels species that spawn in shallow areas from SPSPA, specially Stegastes sanctipauli and Chromis multilineata. / A abundância e atributos ecológicos, como comportamento e reprodução, de peixes recifais são geralmente influenciados por variações na estrutura do habitat, tais como cobertura bentônica e complexidade estrutural. A preferência por diferentes habitats pode variar ontogeneticamente, com jovens geralmente concentrados em áreas rasas e adultos em áreas mais fundas e afastadas da costa. Abudefduf saxatilis, o sargentinho (Pomacentridae) é um peixe recifal amplamente distribuído em ambientes costeiros e insulares no Atlântico Ocidental. No pequeno e remoto Arquipélago de São Pedro e São Paulo (ASPSP), localizado sobre a Dorsal Meso-Atlântica, o sargentinho é uma das espécies de peixes recifais mais abundantes. A população de sargentinhos do ASPSP é morfológica e geneticamente distinta das demais populações no Atlântico Ocidental, sugerindo baixa conectividade genética e automanutenção através da reprodução local. Os objetivos principais deste estudo são: 1) descrever a abundância e distribuição espacial de sargentinhos no ASPSP (piscinas de maré e enseada do arquipélago) e 2) caracterizar quantitativamente aspectos da ecologia reprodutiva da espécie no local. Dados sobre abundância de sargentinhos e de ninhos foram coletados através de censos visuais estacionários. A complexidade do substrato foi avaliada através da metodologia do bastão, na enseada, e método da corrente nas piscinas de maré. A cobertura bentônica nas piscinas de maré foi caracterizada utilizando-se foto-quadrados. Dados sobre o comportamento reprodutivo de machos guardiões o e monitoramento de desovas em ninhos individuais foram coletados pelo método do animal focal e fotografias, respectivamente. Os menores representantes de sargentinhos (< 2 cm de comprimento total, CT) foram registrados exclusivamente nas piscinas de maré, ambientes livres de predadores que foram identificados como potenciais berçários para esta espécie no ASPSP. Não foi registrada influência significativa da complexidade do substrato na abundância e distribuição de sargentinhos nas piscinas de maré e pouca ou nenhuma influência da cobertura bentônica. Na enseada, foi registrada uma relação positiva entre profundidade e tamanho de corpo de A. saxatilis, com indivíduos entre 2-10 cm CT concentrados na faixa mais rasa (0-10 m de profundidade). Indivíduos entre 10-20 cm CT passaram a ocupar profundidades abaixo de 10 m e sofreram influência significativa da complexidade, sugerindo maior necessidade de refúgio contra predadores. A densidade de ninhos de A. saxatilis foi menor em locais com maior abundância de Stegastes sanctipauli, um pomacentrídeo territorial abundante no ASPSP, sugerindo possíveis interações negativas, como disputa por território e locais ótimos de nidificação. Locais com maiores densidades de ninhos de A. saxatilis também apresentaram maiores densidades do predador de ovos Halichoeres radiatus, sugerindo agregação deste predador em áreas com maior oferta de ovos. As interações agonísticas entre o macho guardião e invasores de ninhos foram mais frequentes em ninhos menos acessíveis, provavelmente devido a maior dificuldade em detectar invasores nestes ninhos. Os fatores que influenciaram negativamente o sucesso da desova, ou seja, proporção de ovos remanescentes ao longo do tempo, foram o total de interações agonísticas entre machos e invasores, o total de mordidas do macho guardião no próprio ninho e o tamanho do macho guardião. A profundidade foi o único fator que influenciou positivamente o sucesso da desova. Estes últimos resultados sugerem que machos maiores defendem desovas mais atrativas aos predadores de ovos e a predação de ovos influencia significativamente o sucesso de desova de A. saxatilis no ASPSP. Além disso, se o macho despende mais tempo na defesa do ninho, as chances de forragear em áreas distantes do ninho são menores, uma explicação plausível para a influência significativa do canibalismo filial no sucesso da desova. O maior sucesso reprodutivo em profundidades maiores pode estar relacionado à ausência de competição com outras espécies abundantes de donzelas territoriais que desovam em áreas rasas do ASPSP, principalmente Stegastes sanctipauli e Chromis multilineata.

This study examined the effects of the January 2010 cold spell on mangrove utilizing coral reef fishes off the southeast coast of Florida, USA, in the vicinity of Biscayne National Park (BNP). An ongoing, fishery-independent mangrove visual survey documenting fish assemblages in BNP provided data from the years 1998 to 2014 for examination. Of particular interest were the presence, abundance, and size structure for five mangrove utilizing coral reef fishes: sergeant major (Abudefduf saxatilis), yellowfin mojarra (Gerres cinereus), schoolmaster snapper (Lutjanus apodus), gray snapper (Lutjanus griseus), and great barracuda (Sphyraena barracuda). These species were selected for analysis due to their economic and ecologic importance, their potential as environmental indicators, their connectedness to multiple habitats, and their abundance within the available data set. Data were collected using a modified visual ‘belt transect’ method, consisting of 60 m2 transects running parallel to the mangrove shorelines. Data for average length of fish were reconstructed to form standard normal distributions and the resulting lengths were assigned to various age-classes to create species-specific length-frequency distributions. Variations in presence and abundance were examined across three time periods (1998-2009; 2010-2011; 2012-2014), as well as comparisons of length-frequency distributions. Following the January 2010 cold spell, the presence and abundance values for the two years immediately following the event were significantly decreased compared to the years prior to the cold spell for most of the five species at either mainland (ML) or leeward key (LK) locations. Additionally, the presence and abundance estimates typically remained statistically decreased when compared against the remaining years in the available data set. The size structures for the majority of the five species at either location, however, were not consistently significantly different between the three time periods, as was hypothesized. Instead, the analyses showed mixed results, with the size structure typically shifting towards smaller individuals immediately following the event. These findings suggest that drops in water temperature resulting from cold spells are capable of directly impacting mangrove utilizing reef fish species, albeit to varying degrees depending on various factors, such as physiological tolerances, ecological life history strategies, and habitat requirements.