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Abundância e ecologia reprodutiva de Abudefduf saxatilis (Linnaues, 1758) (Osteichthyes:Pomacentridae) no arquipélago de São Pedro e São Paulo, Brasil.Rodrigues, Laís Silva 15 March 2013 (has links)
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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.
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A Quantitative Assessment of the January 2010 Cold Spell Effect on Mangrove Utilizing Coral Reef Fishes from Biscayne National Park, FloridaEllis, Jeffrey M. 01 July 2015 (has links)
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.
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