Coexistence of reef organisms in the Abrolhos Archipelago, Brazil

The first study on coexistence of reef benthic organisms in Brazilian coral reefs was done in three localities of the Abrolhos Archipelago. Organisms were recorded in concentric circle samples (10 and 20 cm in diameter) randomly laid on transects. Type and frequency of "coexistence events" between pairs of organisms were determined. Most frequent organisms (massive and branched coralline algae, Favia gravida, and Agaricia agaricites) also had many significant positive coexistence events. These results might be related to the abundances of these organisms. The most frequent coral (Siderastrea stellata), however, exhibited only a few significant coexistence events (9% of 32 tests). Since the great majority of events were positive, and since there was high variation in the species/groups involved in significant events in different localities, benthic communities of Abrolhos Archipelago may well be structured primarily by abiotic rather than biotic factors.     

Carbonate Production by Benthic Communities on Shallow Coralgal Reefs of Abrolhos Bank,Brazil

The abundance of reef builders, non-builders and the calcium carbonate produced by communities established in Calcification Accretion Units (CAUs) were determined in three Abrolhos Bank shallow reefs during the period from 2012 to 2014. In addition, the seawater temperature, the irradiance, and the amount and composition of the sediments were determined. The inner and outer reef arcs were compared. CAUs located on the inner reef shelf were under the influence of terrigenous sediments. On the outer reefs, the sediments were composed primarily of marine biogenic carbonates. The mean carbonate production in shallow reefs of Abrolhos was 579 ± 98 g m^-2 y^-1. The builder community was dominated by crustose coralline algae, while the non-builder community was dominated by turf. A marine heat wave was detected during the summer of 2013–2014, and the number of consecutive days with a temperature above or below the summer mean was positively correlated with the turf cover increase. The mean carbonate production of the shallow reefs of Abrolhos Bank was greater than the estimated carbonate production measured for artificial structures on several other shallow reefs of the world. The calcimass was higher than the non-calcareous mass, suggesting that the Abrolhos reefs are still in a positive carbonate production balance. Given that marine heat waves produce an increase of turf cover on the shallow reefs of the Abrolhos, a decrease in the cover represented by reef builders and shifting carbonate production are expected in the near future.     

Diet and foraging opportunism of the Guiana dolphin (Sotalia guianensis) in the Abrolhos Bank,Brazil

Diet analysis allows exploring how coastal dolphins interact with the environment and their role in the marine food webs. We studied the diet and feeding ecology of the Guiana dolphin, Sotalia guianensis, through analysis of stomach content from 42 animals stranded on the eastern coast of Brazil. A total of 1,336 semidigested prey items (fish, otoliths, cephalopod beaks, and crustaceans) were identified. Teleost fish comprised the most frequent food item (92% of the total), followed by cephalopods, and crustaceans. Prey belonged to 34 taxa and richness in individual stomachs varied from 1 to 15 prey taxa. Prey were generally small, but showed a significant trend to increase in size with dolphin length. The main prey of Guiana dolphins were demersal, estuarine, and sound-making fish such as catfish and sciaenids. No sex-related differences in diet were found. Diet composition varied seasonally and occurrence of prey items was coherent with breeding or high abundance periods of some fish species and squids. Our study shows the importance of demersal prey from estuarine and soft-sediment habitats to Guiana dolphin in the Abrolhos Bank and reveals that feeding habits are generalist and opportunistic, with diet reflecting the seasonal abundance and availability of prey.     

Composition and structure of reef fish communities in Paraíba State,north‐eastern Brazil

The composition and trophic structure of reef fish communities in two natural and two artificial reefs along the coast of Paraíba State in north‐eastern Brazil were investigated. A total of 114 species of fish belonging to 47 families were recorded during 120 stationary visual surveys, slightly less than half (46·55%) of which were recorded at all four surveyed localities. Most species are widely distributed on the western Atlantic coast, but several are endemic to Brazil. The greatest diversity and equitability indexes were recorded at the reefs of Sapatas and Cabeço dos Cangulos, whereas the greatest richness and abundance were found at the Queimado shipwreck. The Alvarenga shipwreck reef had the least richness, diversity and equitability. The four localities studied had very similar ichthyofaunas, especially in relation to species composition. The reefs along the Paraíba coast are considered priority conservation areas by the Brazilian Ministry of the Environment, and the information generated by this study will be useful for comparison with other reefs in the region and can be directly applied to programmes seeking to protect and manage these environments.     

Abrolhos bank reef health evaluated by means of water quality, microbial diversity, benthic cover, and fish biomass data

The health of the coral reefs of the Abrolhos Bank (Southwestern Atlantic) was characterized with a holistic approach using measurements of four ecosystem components: (i) inorganic and organic nutrient concentrations, [1] fish biomass, [1] macroalgal and coral cover and (iv) microbial community composition and abundance. The possible benefits of protection from fishing were particularly evaluated by comparing sites with varying levels of protection. Two reefs within the well-enforced no-take area of the National Marine Park of Abrolhos (Parcel dos Abrolhos and California) were compared with two unprotected coastal reefs (Sebasti?o Gomes and Pedra de Leste) and one legally protected but poorly enforced coastal reef (the "paper park" of Timbebas Reef). The fish biomass was lower and the fleshy macroalgal cover was higher in the unprotected reefs compared with the protected areas. The unprotected and protected reefs had similar seawater chemistry. Lower vibrio CFU counts were observed in the fully protected area of California Reef. Metagenome analysis showed that the unprotected reefs had a higher abundance of archaeal and viral sequences and more bacterial pathogens, while the protected reefs had a higher abundance of genes related to photosynthesis. Similar to other reef systems in the world, there was evidence that reductions in the biomass of herbivorous fishes and the consequent increase in macroalgal cover in the Abrolhos Bank may be affecting microbial diversity and abundance. Through the integration of different types of ecological data, the present study showed that protection from fishing may lead to greater reef health. The data presented herein suggest that protected coral reefs have higher microbial diversity, with the most degraded reef (Sebasti?o Gomes) showing a marked reduction in microbial species richness. It is concluded that ecological conditions in unprotected reefs may promote the growth and rapid evolution of opportunistic microbial pathogens.     

食蚊鱼（Gambusia spp.）入侵生态学研究进展

食蚊鱼(Gambusia spp.)是原产于北美洲的著名入侵物种,它对蚊类幼虫具有很强的捕食压力,被作为疟疾防治生物工具而在全世界温带和热带地区扩散.近20多年来的研究认为,食蚊鱼通过食物竞争和捕食等机制威胁引入地的无脊椎动物、鱼类、两栖类的生存,显著影响引入地的生物多样性.它们具有广泛的生境适应性、生长迅速、卵胎生、高生殖率、对生殖生态条件无特殊要求等特点.另外,它们的个体野外寿命不超过2a,种群更新速度快,种群内形成春季和夏季两个繁殖群体,并具有不同的繁殖生物学特点,因而形成复杂的世代结构.遗传上,雌鱼具有混交及能长期贮存精子的特点,能快速建立种群并克服奠基效应.这些种群通过快速适应性进化而形成一定规模的地理群体.当前,由于食蚊鱼在预防疟疾的工作中仍具有不可替代的作用,它会借助于人力的作用而继续扩散.为减轻它对非目标地区和非目标生物的影响,应进一步深入开展其入侵生态学研究.     

Community structure and diet of roving herbivorous reef fishes in the Abrolhos Archipelago, south-western Atlantic

Community structure and diet of roving herbivorous reef fishes were analysed in 13 study sites around the five islands of the Abrolhos Archipelago, north-eastern Brazil (17°58' S; 38°42' W). This area has been part of the Abrolhos Marine National Park since 1983. Abundances and diets of fishes within the families Scaridae, Acanthuridae and Kyphosidae were compared among groups of sites differing in benthic community structure and exposure regime. The abundance of roving herbivorous fishes was higher in shallower sites than in deeper sites. At all study sites, observations of total herbivorous reef fish community structure revealed that 64% of fishes were acanthurids, 33% were scarids and only 4% were kyphosids. This pattern was predominant in all study sites. The majority of fishes examined in this study had the bulk of their diet based on both algae (35–90%) and detritus (35–65%). Among groups of algae, filamentous algae were the most commonly consumed as the majority of roving herbivorous fishes in Abrolhos feed as scrapers and excavators. The exceptions were the kyphosids, which had a diet consisting primarily of macroalgae (mainly Phaeophyta), and Acanthurus coeruleus that consumed mainly turf algae and very little detritus. The data collected indicate that roving herbivorous fishes in the Abrolhos Archipelago are more abundant at calm sites where detritus and delicate algae, their major food resources, are more abundant. The results presented here, along with underwater observations, suggest that the abundance and diet of these three fish families are associated with substratum cover.     

Macroalgal susceptibility to grazing by herbivore fish Siganus spp. at Gulf of Mannar reef,Indian Ocean

Environmental Biology of Fishes - Enhancing the herbivore fish stock is envisaged as a mitigation tool to reverse the macroalgal dominance in a coral reef environment. However, identifying the key...     

Molecular and karyotypic phylogeography in the Neotropical Hoplias malabaricus (Erythrinidae) fish in eastern Brazil

The sedentary, predatory characin Hoplias malabaricus has one of the widest distributions of freshwater fishes in South America and is characterized by seven karyomorphs (A–G) that occur in sympatric and allopatric populations. Karyotypical patterns of variation in wild populations have been interpreted as evidence of multiple lineages within this nominal species, a possibility that may limit the validity of experimental data for particular karyomorphs. This study used the phylogeographic and genealogical concordance between cytogenetic (N = 49) and molecular (mitochondrial DNA) (N = 73) data on 17 samples, collected in 12 basins from south‐eastern and north‐eastern Brazil, to assess the systematic value of cytogenetic data. Cytogenetic patterns show a sex chromosome system in the 2n = 40F karyomorph. Molecular and cytogenetic data indicate a long, independent evolutionary history of karyomorphs and a coastal origin of continental populations in south‐eastern Brazil. The lack of fit with molecular clock expectations of divergence between groups is likely to be due to strong demographic fluctuations during the evolution of this species complex. The results indicate that karyotypical identification provides a reliable baseline for placing experimental studies on Hoplias spp. in a phylogenetic context.     

Ontogeny of microhabitat use and two-step recruitment in a specialist reef fish, the Browncheek Blenny (Chaenopsidae)

Ecological specialization is common on coral reefs and almost certainly contributes to the high diversity of fishes and invertebrates associated with reefs. Here, the recruitment pathway of an endemic Gulf of California fish, the Browncheek Blenny, Acanthemblemaria crockeri (Teleostei: Chaenopsidae), which specializes as an adult on vacant invertebrate tests or tubes, is reported. Like most reef fishes, Browncheek Blennies have a planktonic larval stage that leaves the reef and later settles on suitable habitat as a fully developed juvenile. These blennies follow a clear, “two-step” recruitment pathway, however, and do not reside in invertebrate tests until reaching an adult body size. Individual juveniles and adults were observed for 3 min intervals in order to develop average time budgets for this species. Members of both sexes and all post-settlement life-history stages were included in the analysis. The difference in habitat use by post-settlement juveniles and adults is striking; the average juvenile spends none of its time inside a test, and the average large adult spends all of its time inside a test. Using data on intermediate-sized individuals, the behavioral change associated with invading a test was determined to be size-cued, and it occurs between 20 and 30 mm standard length. Changes in feeding and predator avoidance behaviors are also associated with the ontogenetic shift from life in the open to life in a shelter. Addition of artificial shelters demonstrated the essential role of access to this specialized resource in the population regulation of adults but not juveniles of these blennies.     

Length-weight relationship of fish species captured around an artificial offshore reef (northern Rio de Janeiro,Brazil)

The present work provides length-weight relationships (LWRs) for fish species captured around artificial offshore reef deployed 5 km from Guaxindiba Port, northern Rio de Janeiro, Brazil. The fish were captured during two sampling periods each year between 1996 and 2017 using bottom gill nets (25 m_length × 3 m_depth; 30 mm mesh). The fish were kept on ice and the biometric data, including total length (cm) and total wet weight (g) were determined in the laboratory. A total of 16 species belonging to 10 families were analyzed with Sciaenidae being the species richest family (5 spp) in the samples. The new value of LWRs for Sphyraena guachancho and new maximum sizes recorded for seven species highlight the scarcity of information on biological aspects of South America coastal fishes. These LWRs should assist fisheries scientist and managers to complement their further studies of population parameters to improve management decisions.     

Genome sequence of the bacterioplanktonic, mixotrophic Vibrio campbellii strain PEL22A, isolated in the Abrolhos Bank

Vibrio campbellii PEL22A was isolated from open ocean water in the Abrolhos Bank. The genome of PEL22A consists of 6,788,038 bp (the GC content is 45%). The number of coding sequences (CDS) is 6,359, as determined according to the Rapid Annotation using Subsystem Technology (RAST) server. The number of ribosomal genes is 80, of which 68 are tRNAs and 12 are rRNAs. V. campbellii PEL22A contains genes related to virulence and fitness, including a complete proteorhodopsin cluster, complete type II and III secretion systems, incomplete type I, IV, and VI secretion systems, a hemolysin, and CTXΦ.     

Field verification of the use of chemical alarm cues in a coral reef fish

Chemical alarm cues function as early indicators of a predation threat and influence the outcome of predator–prey interactions in the favour of the prey animal. The tropical goby, Asterropteryx semipunctatus, responded with a stereotypical alarm response, including reduced movement and feeding, following exposure to water that contained chemical cues from injured conspecifics under natural field conditions. Gobies did not exhibit an alarm response when challenged with extracts from damaged fish from a different taxonomic family. The behavioural response in the field was similar to that observed in laboratory experiments. This study verifies the use of chemical alarm cues in a marine fish in their natural environment.     

Habitat preferences of cattail species and hybrids (Typha spp.) in eastern Canada

Interspecific hybridization is widespread in plants and is an important evolutionary process. Hybrids may be fitter than their parental species, at least under some environmental conditions, and this may lead to partitioning of taxa by habitat. In eastern Canada, two cattail species (Typha latifolia and Typha angustifolia) and their hybrid (Typha x glauca) are known to have become increasingly widespread in recent decades, although their habitat preferences and patterns of co-existence at the local scale are not well known. We quantified the occurrence of these three taxa in three different habitat types (high traffic, low traffic, and ‘natural’) at 40 different sites along a sampling route of approximately 2000 km in eastern Canada. There were no significant overall associations between habitat type and taxon, although intraspecific comparisons among sites showed that the hybrid was most likely to grow in high traffic (highly disturbed) sites. In addition, pairwise comparisons revealed significant independence of T. latifolia and T. angustifolia, although the hybrid was equally likely to co-exist with either of its parental species. The presence of the three taxa in several habitats, including highly disturbed roadside areas, is consistent with their increasingly invasive tendencies.     

Frugivory by the fish Brycon hilarii (Characidae) in western Brazil

Frugivory and seed dispersal have been poorly studied in Neotropical freshwater fishes. We studied frugivory and seed dispersal by the piraputanga fish (Brycon hilarii, Characidae) in the Formoso River, Bonito, western Brazil. We examined the stomach contents of 87 fish and found the diet of piraputanga consisted of 24% animal prey (arthropods, snails, and vertebrates), 31% seeds/fruits and 45% other plant material (algae/macrophytes/leaves/flowers). The piraputangas fed on 12 fruit species, and were considered as seed dispersers of eight species. Fruits with soft seeds larger than 10 mm were triturated, but all species with small seeds (e.g. Ficus, Psidium) and one species with large hard seed (Chrysophyllum gonocarpum) were dispersed. Piraputangas eat more fruits in the dry season just before the migration, but not during the spawning season. Fish length had a positive relation with the presence of fruits in their guts. The gallery forest of the Formoso River apparently does not have any plant species that depend exclusively on B. hilarii for seed dispersal because all fruit species are also dispersed by birds and mammals. Based on seed size and husk hardness of the riparian plant community of Formoso River, however, the piraputangas may potentially disperse at least 50% of the riparian fleshy fruit species and may be particularly important for long-distance dispersal. Therefore, overfishing or other anthropogenic disturbances to the populations of piraputanga may have negative consequences for the riparian forests in this region.     

Energy transformations by the sargassum fish,Histrio histrio (L.)

Ingestion, egestion, growth, and respiration measurements were made in the laboratory on three size-classes of the Sargassum fish, Histrio histrio(L.). Comparison of three size-classes showed changes from high growth and low respiration and assimilation in small Histrio to reduced growth and increased respiration and assimilation in larger fish. A high assimilation and growth efficiency suggest that Histrio is adapted to a food-limited environment (Sargasso Sea). Energy requirements of the smallest size-class (10–29 mm) were compared to the energy provided by their dominant food source, the Sargassum shrimp Latreutes fucorum (Fabricius) and Leander tenuicornis (Say). The annual energy requirement per individual was 1.4 times greater than the food energy available. This discrepancy is attributed to the difficulty in extrapolating laboratory studies to the field and the difficulty in obtaining adequate population size measurements of the Sargassum community fauna.     

Connectivity,diversity, and hybridization between two endemic fish species (Percilia spp.) in a complex temperate landscape

The identification of closely related species with partially overlapping distributions is fundamental for effective conservation. Here we analyzed 28 sequenced microsatellites, mtDNA sequences, and morphological data, to describe the connectivity, genetic relationship, and distribution of Percilia gillissi and Percilia irwini, two endangered species inhabiting two contiguous watersheds in Chile (Itata and Biobío). We provide evidence of discordance in the spatial distribution of the two genomes (nuclear and mitochondrial). Three large clusters were identified with microsatellites, with one cluster straddling both watersheds. Three clusters were also evident in mtDNA with one cluster straddling both watersheds and the other two restricted to the Itata watershed’s northern reaches. Analyses of both microsatellite and mtDNA identified P. gillissi in the Itata watershed northern reaches and P. irwini in the Biobío watershed. Fish were detected in the Itata watershed that carried mtDNA characteristic of P. irwini but nuclear microsatellite profiles of P. gillissi suggesting an incomplete reproductive barrier between the species and connectivity between the watersheds. Additionally, fish were identified in the Itata northern reaches carrying mtDNA haplotypes sufficiently distinct from those of P. gillissi and P. irwini to suggest the existence of higher mtDNA diversity within P. gillissi than previously recognized. Finally, there was limited support for taxonomical classification based on morphological and meristic traits in this region.