Distribuição e uso de habitat por peixes recifais em um gradiente ambiental: estudo de caso em recifes areníticos

There are several abiotic factors reported in the literature as regulators of the distribution of fish species in marine environments. Among them stand out structural complexity of habitat, benthic composition, depth and distance from the coast are usually reported as positive influencers in the diversity of difentes species, including reef fish. These are dominant elements in reef systems and considered high ecological and socioeconomic importance. Understanding how the above factors influence the distribution and habitat use of reef fish communities are important for their management and conservation. Thus, this study aims to evaluate the influence of these variables on the community of reef fishes along an environmental gradient of depth and distance from shore base in sandstone reefs in the coast of state of Rio Grande do Norte, Brazil. These variables are also used for creating a simple predictive model reef fish biomass for the environment studied. Data collection was performed through visual surveys in situ, and recorded environmental data (structural complexity of habitat, type of coverage of the substrate, benthic invertebrates) and ecological (wealth, abundance and reef fish size classes). As a complement, information on the diet were raised through literature and the biomass was estimated from the length-weight relationship of each species. Overall, the reefs showed a low coverage by corals and the Shallow reefs, Intermediate I and II dominated by algae and the Funds by algae and sponges. The complexity has increased along the gradient and positively influenced the species richness and abundance. Both attributes influenced in the structure of the reef fish community, increasing the richness, abundance and biomass of fish as well as differentiating the trophic structure of the community along the depth gradient and distance from the coast. Distribution and use of habitat by recifas fish was associated with food availability. The predictor model identified depth, roughness and coverage for foliose algae, calcareous algae and soft corals as the most significant variables influencing in the biomass of reef fish. In short, the description and understanding of these patterns are important steps to elucidate the ecological processes. In this sense, our approach provides a new understanding of the structure of the reef fish community of Rio Grande do Norte, allowing understand a part of a whole and assist future monitoring actions, evaluation, management and conservation of these and other reefs of Brazil.

Estratégias tróficas do peixe traíra, Hoplias malabaricus e do peixe cascudo, Hypostomus pusarum do açude Marechal Dutra, Rio Grande do Norte, Brasil

The fish, Hoplias malabaricus (Osteichthyes: Erythrinidae) and armored catfish, Hypostomus pusarum (Loricariidae) are of freshwater origin from the neotropical region, and are considered ecologically and economically of important. This work investigated the trophic strategies, the morphology and histology of the digestive tract of these fish captured from the Marechal Dutra reservoir, Acari, the semiarid region of Rio Grande do Norte, Brazil. A total of 133 individuals of H. malabaricus and 118 specimens of H. pusarum were analyzed. The two study species occupy different levels in the food chain and spatial distribution in the water column of the reservoir. The results of this study are presented in the form of four scientific papers. The first article describes the morphology and histology of the digestive tract and the feeding habits of H. malabaricus (Bloch, 1794). This fish has a short intestine, with an intestinal coefficient of 0.72 ± 0.09. The dietary importance index indicates that H. malabaricus feeds preferentially on animal matter, especially on fish (72.8%) and prawns (27.2%). The histology of its digestive tract confirms the carnivorous feeding habit. The second article discusses about the pioneering work on the feeding strategy and the characterization of anatomy and histology of the digestive tract of H. pusarum. The intestine of this fish is long, with an intestinal coefficient of 10.8±0.7. The dietary importance index indicates that H. pusarum feeds preferentially on organic matter in decomposition (88.7%) and on filamentous microalgae and diatoms (11.3%). The third article compares the morphological aspects of the digestive tract of H. malabaricus and H. pusarum, in relation to their food habits. The arrangement of the digestive organs in both species is directly related to the shape of the peritoneal cavity and the form of the body. The short intestine of H. malabaricus and the long intestine of H. pusarum are associated with their feeding habits. The morphology of the digestive tracts of H. malabaricus and H. pusarum confirm their food habits, carnivorous and detritivorous / herbivorous, respectively. The fourth article discusses the food and reproductive aspects (length and weight, length-weight relationship, type of growth and sex ratio) of H. pusarum. This species has a negatively allometric growth, with the predominance of females in the sampled population. H. malabaricus inhabits the pelagic environment and is a carnivore, while H. pusarum, lives in the benthic environment and is characterized as a detritivore/herbivore. Each species studied shows a very different diet, without trophic competition between them. The morphological and anatomical structures of the digestive tract reflect their feeding strategy.

Aspectos biológicos do peixe-olhudo-dentinho, Synagrops bellus (Actinopterygii: Acropomatidae), da plataforma externa e talude superior do estado de São Paulo, Brasil.

Biological aspects of the blackmouth bass Synagrops bellus from the outer shelf and upper slope along the coast of São Paulo, southeastern Brazil, are presented. The species represented about 71.6% and 9.7% in number of the total catch performed by balloom trawl in the isobaths of 300m and 500m respectively. Body sizes of 266 individuals ranged between 130 and 265mm total length, with sex ratio of 55.9% males, and 44.1% females, where most individuals were in maturation stage. Twenty two food items were found, pointing out Myctophidae fishes, Penaeidea and Caridea shrimps, Brachyuran megalopae, Enoploteuthidae and Cranchiidae cephalopods, pteropods and tunicates. The intestinal coefficient increases as the body size increase, and the number of gill rakers ranged between 16 and 17. Length-weight relationship was WT = 6.0 x 10-6 x TL3.12, r2 = 0.9495. Synagrops bellus is an important link between zooplankton and micronekton, and demersal and pelagic predators in the outer shelf and upper slope in southwestern Brazilian coast.

Biologia reprodutiva da Tainha, Mugil curema valenciennes, 1836 (osteichthyes: mugilidade) nas águas costeiras do Rio Grande do Norte

The marine fish white mullet, Mugil curema Valenciennes, 1836 (Osteichthyes: Mugilidae) exhibits a wide geographical distribution, being common in the Brazilian coast and is an important component of the artisanal fisheries. The objective of this study was to investigate the reproductive biology of M. curema in the coastal waters of Rio Grande do Norte. Fish samples were captured on a monthly basis during August, 2008 to July, 2009. The fish specimens were numbered, weighed, measured, dissected and their gonads were removed, weighed, their sex and gonadal development were identified. The length-weight relationship was determined for males and females. The sex ratio, the size at first gonadal maturation and gonadosomatic index (GSI) were calculated and ovarian development was investigated using macroscopic and histological techniques. The fecundity, spawning type and the reproductive period of the species were determined. A total of 366 specimens (186 males and 180 females) were captured. The sex ratio was 1:1 and the females were heavier than males. The estimated values of the angular coefficient for both sexes suggest that the species has isometric growth. The size at which 50% of the population began the process of maturation was 25.9 cm of total length for grouped sex. The macroscopic characteristics of the ovaries showed four stages of development: immature, maturing, mature and spent. However, the microscopic characteristics of the ovaries showed five stages of development: immature, early maturing, late maturing, mature and spent. The development of oocytes indicated five phases: Chromatin-nucleolus (phase I), initial perinucleolar (phase II), final perinuclear (phase II), formation of vitelline vesicle or yolk (phase III), vitellogenic (phase IV) and complete vitellogenesis (phase V). The species has a prolonged spawning period, with two peaks coinciding with the rainy season.

Age and growth of Ray's bream (Brama brama) from the south of Portugal

Age and growth of 234 Brama brama Bonnaterre (1788) (Pisces: Bramidae) caught hy semi-pelagic longline off the south coast of Portugal (Algarve) was studied using otoliths for age determination. Samples consisted of fish varying in total length from 32 to 56 cm and in weight from 332 to 2032 g. Age classes from III to XII were represented in the catches. The von Bertalanffy growth curve was fitted and the length/weight relationship was calculated. (C) 2001 Elsevier Science B.V. All rights reserved.

Allometric study of skeleton weight, body weight and length relationship of Euryglossa orientalis (Bl. & Schn.) (Family: Soleidae) from Karachi coast

Present study deals with the family Soleidae (common sole) Euryglossa orientalis (Bl. & Schn.) of the order Pleuronectiformis from Karachi coast. Separate equation (regression line) for describing the length weight relationships for male and female combined are justified. Allometric studies were made on skeleton weight relative to the length and the weight of the fish. The regression equation 'a' and 'b' values of standard length/skeleton weight and body weight/skeleton weight are statistically significant.

The relationship of shell dimensions and shell volume to live weight and soft tissue weight in the mangrove clam, Polymesoda erosa (Solander, 1786) from northern Australia

Shell dimensions (length, height, width) and shell volume were evaluated as estimators of growth for Polymesoda erosa in northern Australia. Each parameter was a good estimator when applied to live weight (r2 values of 76-96 percent), but not to soft tissue weight (wet, dry, or ash-free dry weight) (r2 values of 13-32 percent). The b value for shell volume to weight relationship of clams collected during the dry season (June to October) was signifi cantly different than for those collected in the wet season (February to April).

The Stability of a Vertical Single-Walled Carbon Nanotube Under Its Own Weight

It has been reported recently that single carbon nanotubes were attached to AFM tips to act as nanotweezers. In order to investigate its stability, a vertical single-walled carbon nanotube (SWCNT) under its own weight is studied in this paper. The lower end of the carbon nanotube is clamped. Firstly the governing dimensionless numbers are derived by dimensional analysis. Then the theoretical analysis based on an elastic column model is carried out. Two ratios, I.e., the ratio of half wall thickness to radius (t=R) and the ratio of gravity to elastic resilience ($\rho$gR=E), and their influences on the ratio of critical length to radius are discussed. It is found that the relationship between the critical ratio of altitude to radius and ratio of half thickness to radius is approximately linear. As the dimensionless number $\rho$gR=E increases, the compressive force per unit length (weight) becomes larger, thus critical ratio of altitude to radius must become smaller to maintain stability. At last the critical length of SWCNT is calculated. The results of this paper will be helpful for the stability design of nanotweezers-like nanostructures.

Mercúrio total em Orthopristis ruber (Haemulidae) de quatro regiões costeiras do Estado do Rio de Janeiro, Brasil

O objetivo do presente estudo foi investigar as concentrações de mercúrio total (HgT) nos músculos de Orthopristis ruber de quatro ecossitemas costeiros e identificar possíveis correlações existentes entre comprimento, peso, sexo, estação do ano e índices biológicos. O HgT foi analisado nas regiões de Cabo Frio (CF, n=31), Baía de Guanabara (BG, n=61), Baía de Sepetiba (BS, n=43) e Baía da Ilha Grande (BIG, n=32), as quais apresentam diferentes níveis de degradação ambiental. A BG recebe grande quantidade de efluentes domésticos e industriais de toda região metropolitana do Rio de Janeiro e tem sido considerada como uma das áreas mais poluídas do Brasil. Já na BS, a intensa atividade metalúrgica no seu entorno faz com que esta possa ser tida com nível de degradação intermadiária, enquanto CF e BIG são duas áreas vistas como áreas bem preservadas. As concentrações de HgT foram determinadas através de CV-AAS (FIMS - 400,Perkin Elmer) - utilizando boridreto de sódio como agente redutor. Foi utilizado DORM 3 (National Research Council, Canada) como material de referência (média da recuperação DP =99,2 4,9 %). As concentrações médias de HgT DP para BIG e CF foram, respectivamente, 209,8 118,9 ng/g, e 199,9 88,2 ng/g. Estas regiões apresentaram concentrações significativamente mais elevadas, enquanto a BG mostrou concentrações intermediárias (112,9 88,0 ng/g; ANCOVA, p<0,03). Por outro lado, a BS foi a região com as menores concentrações de HgT (11,3 11,5 ng/g). Tais resultados sugerem que, mesmo sendo áreas degradadas, o HgT não está totalmente biodisponível para BG e BS. Ademais, provavelmente as correntes oceânicas são uma fonte de mercúrio para CF e BIG, carreando mercúrio biodisponível para essas áreas. Para BG análises adicionais foram feitas a fim de identificar a acumulação de HgT ao longo do desenvolvimento ontogenético de O. ruber, uma vez que as concentrações do metal foram maiores em adultos do que em juvenis (PERMANOVA, p< 0,0001). As concentrações de HgT foram positivamente relacionadas tanto com o comprimento (Spearman test; r = 0,85; p <0,001) quanto com o peso (Spearman test; r =0,85; p <0,001) dos peixes da BG, mostrando que o O.ruber acumula HgT ao longo da vida. Diferenças entre sexos foram encontradas apenas para os O. ruber da BIG, onde fêmeas (300 ng/g) apresentaram maiores concentrações de HgT que os machos (~150 ng/g). Dentre os índices biológicos analisados, o índice gonadossomático foi o de maior relevância devido sua correlação negativa entre os níveis de HgT com todos os dados em conjunto (p<0.001), tanto para fêmeas (p<0.001) quanto para machos (p<0.02), sugerindo que o mercúrio pode afetar negativamente a reprodução de O.ruber.

Reproductive biology of Otolithes cuvieri (Trewavas, 1974) from Mumbai waters

The reproductive biology of Otolithes cuvieri (Trewavas, 1974) is reported in the present communication. The size at first maturity for the females was estimated to be 275 mm. The spawning activity was observed throughout the year with two peaks occurring in April and June. Two prominent peaks of gonadosomatic index (April and June) also support the view of two major spawning. Relative fecundity ranged from 71,574 to 79,680 eggs per 100g of body weight. Relationship of fecundity with fish length, fish weight and ovary weight of the species has been established as F = -132971 + 1447.441 x L, F = 124195 + 468.798 x W and F = 250517.5 + 3369.029 x OW, respectively. Study of sex ratio by random sampling of the catches indicated the dominance of females in commercial catches of Mumbai coast.

Population dynamics of two jewfishes Jhonius argentatus and Johnieops vogleri) in the coastal waters of Bay of Bengal, Bangladesh

Population parameters of Jhonius argentatus and Johnieops vogleri in coastal waters of Bay of Bengal, Bangladesh were estimated by using FiSAT programme. The von Bertalanffy growth parameters, extreme length (cm) and growth constant K (year ·1) were found to be 46.50 and 0.59 for J. argentatus, and 33.50 and 0.85 for J.vogleri The Loc(cm) and Z/K estimates provided by Wetherall plot were 46.694 and 1.791 for J. argentatus, and 31.25 and 2.623 for J. vogleri. The annual rate of natural (M) and fishing mortality (F) were estimated as 1.12 and 0.78 for J. argentatus, and 1.56 and 1.28 for J. vogleri. Rate of exploitation (E) was estimated as 0.41 for J. argentatus and 0.45 for J. vogleri. About 80.04% of J. argentatus were found to be recruited during peak pulses (April-May) and 19.96% during lean pulses (October-November) and 85.75% J. vogleri during peak pulses (May-July) and 14.25% during lean pulses (September-October). The growth performance index(') was 3.11 for J. argentatus and 1.93 for J. vogleri. The total length and body weight relationship was found to be W = 0.0403 TL25723 for J. argentatus and W = 0.0907 TV3482 for J. vogleri.

Biology of Bombay duck, Harpodon nehereus (Ham., 1822), from Mumbai waters, India

Morphometric and meristic study of Harpodon nehereus (Hamilton, 1822) from Mumbai waters indicated that the specimens belonged to a homogenous population. Based on the meristic study, the fin formula can be written as B sub(23-269), D sub(12-139), P sub(11-139), V sub(9), A sub(13-15), C sub(19), L sub(40). Length-weight study revealed an allometric relationship, presented as Log W= -3.1362 + 3.6059 Log L. The analysis of food and feeding habits revealed the species to be voracious, carnivorous and cannibalistic, feeding mainly on Acetes spp., juveniles of H. nehereus itself, prawns and Coilia dussumieri. The feeding intensity was found to be the maximum during September and November, and also in mature specimens which may be the preparation for the ensuing spawning activity. Reproductive biology indicated two peak spawning seasons in November and March. However, the species as a whole has prolonged breeding season and spawning occurs throughout the year. Average fecundity was estimated as 314 ova/g body weight of fish and the length at which 50% of female specimens mature (Lc sub (50)) was calculated as 255 mm.

Morphometric measurements as an index for estimating yield of meat in shell fishes, 2. Mussel (Perna viridis) and clam (villorita cyprinoides)

Observations (76 nos) on height-length and whole weight-meat weight relations of mussels (Perna viridis), both wild and cultured were made. From the length of mussel the height can be worked out by the equations (logarithmic scale), 1. y = 0.360+0.988 x for wild; 2. y = 0.334+1.011 x for cultured, where x is the length (cm) and y is the height (cms). So also to any height the corresponding meat weight can be obtained by the regression equation. log w=-0.8178+1.9769 log H for wild variety (1) log w=-1.3049+2.8385 log H for culture-variety (2) where w is the meat weight (g) and H is the height (cm) of the mussel. Fourteen observations on size weight measurements of dams were made. The yield varied from 8.9 to 13%. The length-height relationship worked out for clams (Villorita sp) is y=0.485+1.005 x for length x and height y.

Population dynamics and stock assessment of the common carp (Cyprinus carpio) in Iranian waters of the Caspian Sea

In order to come up with the responsible fishing pattern of common carp, there was a need to identify some of the biological characteristics and stock assessment of carp in Iranian waters of the Caspian Sea .The fork length ,weight ,age ,growth parameters of von bertalanffy and mortality rates of common carp were estimated from oct 2006 to sept 2007.Based on the exponential relationship between length and weight in the size range 6.3-65.6 cm ,b was calculated 2.895, 2.843 and 2.925 respectively for combined sexes ,males and females. The mean condition factor was 1.9 which is close to the ideal condition.The results from measuring 3170 specimens ,were showed the first fork length of maturity was 30 cm for males and 32 cm for females. The results indicated that females were predominate and sex ratio was 0.66:1 (M:F) and chi-squares analysis showeda significant difference between males and females.(p<0.05).Length infinity and growth coefficient were calculated by three different methods as below: Length frequency analysis : k=0.17 L∞ =68.04 Age-Length Key k=0.15 L∞ =74.25 Back calculation : k=0.14 L∞ =68.4 The mortality parameters and exploitation rate were estimated as below : Z=0.73 per year M=0.31 per year F=0.42 per year E=0.56 Refer to amount of common carp catch in 2007 -08 ,biomass was calculated 9640.2 tones by jone's cohort analysis and MSY 2374.5 tones.According to analysis ,the number of common carp in the distribution area (Iranian part of the Caspian Sea ) was estimated 24 millions in the 2006-07.

The study of biological characteristics and heavy metal determination of Cd, Pb, Fe, V, Ni in the muscle, liver and gonad tissues of kingfish Scomberomorus commerson in the coastal waters of the Hormozagan Province (Persian Gulf)

Biological studies and heavy metal (Ni, v, Fe, Pb,Cd) determination in liver, gonad and muscle of Scomberomorus commerson were carried out from Oct 2006 to Sept 2007 in Hormozgan coastal waters. 599 Samples were gutted for reproduction and nutrition studies, fork length and weight were measured to nearest cm and g respectively. Meanwhile 40 samples were also investigated for heavy metal studies. All specimens were collected from two major landing sites (Bandar Lengeh & Bandar Abbas). Minimums & maximum fork length & weight were 29, 128 cm & 235 and 15350 g respectively.Isometric growth was shown according to our study and b was estimated 2.9 (overall), 2.91(male) & 2.89 (female). The average relative gut length was 0.52± 0.007 and it was determined that S. commerson is a carnivorous. More than 99 percent of gut content was different teleost fishes. Gastro somatic index had two peaks in Nov & Jan (before spawning) and with a decreased trend in July, the spawning period. Occurrence of empty stomach was estimated % 65.77. Maximum amount of condition factor was in Dec. Spawning season was started from June. The average of Absolute & relative fecundity (to weight unit) was 1217149±179315 and 178.2±15.58 respectively. Lm50% was estimated 75 cm for females. Sex ratio was 0.97: 1 (male: female). Chi- Square test showed no significant difference (p>0.05). Maximum amount of hepatosomatic index was estimated in March.Metal concentrations were determined using either Flame Atomic Absorption Spectroscopy (for Fe) or Graphite Furnace Atomic Absorption Spectroscopy (for Pb,Cd,Ni and V). The mean concentration (μg/g dry weight)of Pb,Cd,Ni,V and Fe in the liver were 0.0309, 0.0268, 0.0672, 0.0077, 2.5159 in the gonad 0.0440 ,0.0295, 0.1096, 0.0000, 1.4449 and in the muscle 0.0244, 0.0324, 0.0656, 0.0128, 1.6138 respectively. The maximum metal concentrations were below the maximum permissible limits for human consumption recommended by the USEPA, WHO and the UK. The results of Kendall's Tau-b correlation coefficient were as follows: The Liver tissue: There were significant positive linear relationships between accumulation of V, Fe, and Pb with Fork length, Pb and Fe with weight, GSI with Pb, Cd, V and 109 Fe, and a negative linear relationships between HSI with accumulation of V and Fe, Fork length, weight and GSI. The Gonad tissue: There were significant positive linear relationships between GSI with accumulation of Pb, Cd, Fe, Fork length and weight, a negative linear relationship between HSI with Fork length, weight and GSI. The Muscle tissue: There were significant positive linear relationships between accumulations of V, Fe with Fork length and weight factors and as well as GSI with Cd, V, Fe, Pb, Fork length and weight,a negative linear relationship between HSI with Fork length, weight, Cd, Fe and GSI. The results of Mann-Whitney U tests (P≤0.05) show that there were significant differences between summer and autumn from heavy metal contents in the studied tissues point of view. The only exceptions were for Ni in the liver, gonads and muscle and as well as there were significant differences between male and female from heavy metal contents in the studied tissues. The only exceptions were for Pb in muscle, Ni in liver, gonad and muscle, V in muscle, and Cd and Fe in gonads.