Distribution of Micropogonias furnieri (Pisces: Sciaenidae) in Sepetiba Bay,Rio de Janeiro,Brazil

Distribution of Micropogonias furnieri in the Sepetiba Bay, an ecosystem highly important as rearing ground for this species that represents 5.8% of the numerical catches by otter trawling, was analyzed based in monthly and bi-monthly samplings from two programmes (beach seines = continental margin; and otter trawl = inside of the Bay), over three annual cycles, between 1993 and 1997. Spatial comparisons were assessed by dividing the Bay in two zones for the beach seines (inner and outer Bay) and three zones for the otter trawl (inner, central and outer Bay), following depth, salinity and transparency gradient, as well as for the influence of the sea. Beach seines (30 m extension, a 10 m length x 2.5 m of height x 7 mm mesh) and otter trawls were used. Trawls covered 1.5 km and the boat (net mouth 8 m, mesh size 12 mm between opposites knots in the cod). Temperature (degree C) and salinity (p.s.u.) were taken in each sampling; depth (m) and transparency (m) were measured during the trawl. Fish from beach seine were basically young-of-the-year; in the trawl they were individuals of larger size with total length varying from 70 mm to 300 mm. Spatially, highest CPUEs were found for the continental margin in the inner Bay, and for the inside Bay, in the inner and central zones. Highly significant correlations were detected among M. furnieri abundance and low salinity, transparency and depth in the inner Bay, with no defined pattern for the continental margin. Temporally, differences in fish abundance were shown only for the second annual cycle (1996) for the continental margin, with peaks in September/October.     

Induction of oocyte maturation in the white croaker Micropogonias furnieri (Pisces: Sciaenidae) by human chorionic gonadotropin.

The present work aimed to identify the best doses of human chorionic gonadotropin (hCG) needed to induce oocyte maturation of Micropogonias furnieri and to characterize ovarian dynamics during the periovulatory period. Adult M. furnieri females with fully developed ovaries were injected intraperitoneally with four different doses of hCG. The gonadotropin response was succeeded by analyzing morphologically gonadal biopsies and following the postinjection changes in follicle diameter. Oocyte maturation was induced by three doses used: 100, 300, and 500 IU of hCG kg bw-1, and was reached 48 h after treatment with 300 and 500 IU of hCG kg bw-1, and 72 h after treatment with 100 IU of hCG kg bw-1. Concerning ovarian dynamics, only 100 and 300 IU of hCG kg bw-1 mimicked the natural ones which have a synchronic group maturation. In conclusion, the dose mimicking natural ovarian dynamics and inducing oocyte maturation more quickly is 300 IU of hCG kg bw-1.     

Steroid metabolism in vitro during final oocyte maturation in white croaker Micropogonias furnieri (Pisces: Sciaenidae).

Final oocyte maturation (FOM) is a process involving a complex set of genetical, biochemical, and morphological mechanisms. FOM involves the shift of a post-vitellogenic follicle to a pre-ovulated oocyte, which is necessary for fertilization by spermatozoan to occur. This process is regulated by a maturation-inducing steroid (MIS) at the follicular level. In other species of scienids fish the MIS, a hydroxilated derivatives of progestagen 17, 20beta, 21-trihydroxy-4-pregnen-3-one (20beta-S), was identified. Although Micropogonias furnieri is the second fishery resource of Uruguay, basic knowledge about its endocrine process is very scarce. The aim of this work was to investigate what steroids are synthesized in vitro by the oocyte follicle of M. furnieri during the maturation process. Fragments of ovary (1 g) in three stages: post-vitellogenic (PV), maturing (Mtg), and mature (M) were incubated with 1 microg x g(-1) of tritiated progesterone (P) at 30, 60, and 180 min. After extraction with ethanol and dichloromethane, steroid metabolites were purified by TLC and rpHPLC. Two progesterone derivatives with identical chromatographic properties of 20beta-S and 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) were purified. In other Teleost fish these steroids are biologically active as MIS. The 17,20beta-P was clearly detected in Mtg and M stages and confirmed by enzymatic oxidation with enzyme 20beta-HSD. The 20beta-S was strongly detected in all Mtg oocytes. The results do not corroborate 20beta-S as a major hormone synthesized in the ovary in FOM as occurs in other scienid fish. A differential steroid synthesis in the advanced oocyte stages suggests that the 20beta-S is acting as a MIS in M. furnieri.     

Statistical model of variable allometric growth: otolith growth in Micropogonias furnieri(Actinopterygii, Sciaenidae)

The main objective of this study was to develop a statistical model for accurate estimates of relative growth. The method was based on identifying patterns of the residuals obtained from the Huxley's allometric equation. Three different approaches were applied: (1) growth with variable proportionality and constant allometry coefficient, (2) growth with constant proportionality and variable allometry coefficient and (3) distinct growth phases in which proportionality and allometry coefficients remained constant. The proposed statistical models were applied to the relationship of the otolith size and fish size of whitemouth croaker Micropogonias furnieri . The best fit was obtained when using approach (3). A change in the growth parameters was associated with the attainment of sexual maturity.     

Morphology of the digestive tract of the Whitemouth croaker Micropogonias furnieri (Desmarest, 1823) (Perciformes: Sciaenidae)

Studies have shown the feeding diversity of teleostean fish, which is conditioned by environmental characteristics or the biology of the different species. Analysis on the morphology of the digestive system (DS) of fish made it possible for researchers to know the food regimen of several species at different stages of life. On the other hand, it is known that food habits may lead to morphological changes in the DS the same way that different food habits may be imposed by morphological limitations of this system. Among the species of greater commercial importance in Brazil, Micropogonias furnieri is highly representative of fish in south‐eastern Brazil. Therefore, the objective of this study was to analyse the morphology of the DS of M. furnieri. Results on the morphology of the DS observed in this study were similar to the patterns determined for the morphology of teleostean fish. In this study, it was observed that the DS of the Whitemouth croaker is directly related with the shape of the peritoneal cavity; these fish showed oesophagus, stomach, pyloric caeca and intestines. The pyloric caeca showed morphological adaptations in relation to sexual maturation, with well‐developed caeca found in sexually mature animals.     

Ultrastructure and protein composition of the oocyte envelope in the whitemouth croaker (Micropogonias furnieri, Desmarest, 1823, Sciaenidae, Perciformes)

The organization, time‐course deposition and protein composition of the oocyte envelope in the whitemouth croaker, Micropogonias furnieri, were analyzed at different stages of oocyte maturation. Adult females were sampled in the Uruguayan coast of the Río de la Plata during three annual periods. Morphological organization and temporal deposition were assessed by histology and electron microscopy. Protein composition was analyzed using gel electrophoresis, followed by MALDI‐TOF‐MS. Oocyte envelope deposition starts in lipid‐yolk oocytes, reaching maximum width in fully grown oocytes when it shows a three‐layer organization. In mature oocytes, the envelope becomes narrower than in the previous stage and loses its trilaminar structure. In envelopes from fully grown oocytes, one‐dimensional gel electrophoresis revealed five bands; mature oocytes showed only three bands. Following two‐dimensional gel electrophoresis, 14 major polypeptides were detected in envelopes from fully grown oocytes. Considering that morphological and biochemical results obtained from samples of the three annual periods were remarkably similar, data reported here might provide a useful baseline to assess the future impact of pollutants on the oocyte envelope and reproductive success of whitemouth croakers inhabiting the geographic area.     

Sex ratio and size structure of Micropogonias furnieri (Desmarest, 1823) (Perciformes, Sciaenidae) in Sepetiba Bay, Rio de Janeiro, Brazil.

Sex ratio and size structure constitute basic information in assessing reproductive potential and estimating stock size in fish populations. One hundred fifty-one individuals of Micropogonias furnieri caught by experimental otter trawls, in three zones (inner, central, and outer) of Sepetiba Bay between October 1998 and September 1999 were examined. Males outnumbered females (1.3:1.0) in all zones but no significant differences were detected. Only in the outer zone (5.0:1.0) were male/female rates significantly different according to the chi-square test. No temporal differences were observed in sex ratio. Fish size ranged from 81 to 244 mm total length (TL) with significant differences in 155 to 185 mm TL size classes, where males predominated, and a slightly higher number of females were observed for the smaller size class (TL = 95-150 mm). Size distribution varied according to the zone, with juveniles predominating in the inner and adults in the outer zone. Spatial difference in size structure observed in this study indicates that the inner bay is a rearing ground during the first life-cycle period, and movement toward the sea occurs as fish increase in size.     

Food and feeding habits of Ilisha africana (Bloch) (Pisces: Clupeidae) off the Lagos coast, Nigeria

A total of 2215 specimens of Ilisha africana (Bloch) were examined for the food habits of the species off the Lagos coast, Nigeria. Their food consisted mainly of crustaceans, fish and molluscs; less important in the stomach contents were insects, annelids, chaetognaths, coelenterates, urochordates and phytoplankton. The incidence of nematodes in the stomachs was low. Monthly variation of food as well as variation with fish size and water depth were examined, as was the relationship of food composition to components of the plankton fauna. Feeding habits of I. africana were compared with those Sardinella maderensis (Lowe), Galeoides decadatylus (Bloch), Brachydeuterus auritus (Val.) and Vomer setapinnis (Mitchill); there was an overall diversity in the diets of these fish species.     

Feeding habits of the bluemouth, Helicolenus dactylopterus dactylopterus (Delaroche, 1809) (Pisces: Sebastidae) in the Portuguese coast

In order to investigate the feeding habits of Helicolenus dactylopterus dactylopterus along the continental Portuguese coast, a total of 619 individuals were sampled of which 60% contained food in their stomach and 35% had more than one prey item. Among the 81 prey items that were identified in the stomachs, benthic and benthopelagic prey prevail on this species diet. Acantephyra sp, Pasiphaea sp, mysidacea, and teleostei n.i. were the prey with the higher percent index of relative importance (%IRI) value. Three length groups (5?C20?cm, 21?C27?cm, and 28?C48?cm) were defined through cluster analysis of the mean abundance of prey items. A permutational MANOVA detected significant differences in the diet and stomach fullness index for TLG, season, and maturation stage. Smaller fishes had a generalized diet, feeding mainly on mysidacea changing their diet above 20?cm TL, where a major consumption of natantia was found. The larger individuals, >28?cm TL, present a less generalized diet with pisces as dominant prey group. Seasonally, natantia and pisces were the principal prey groups during spring and winter, respectively, while mysidacea and other crustaceans were predominant during the rest of the year. Mysidacea were also the main prey group for immature individuals while natantia and pisces were the principal prey groups to the other maturity stages. The results of this study indicate that H. d. dactylopterus has a diverse diet focused on small crustaceans such as misyds and as specimens grow shrimps and fishes become more consumed, with larger specimens having a more specialized diet. The different nutritional needs during spawning season also seemed to influence the feeding habits of H. d. dactylopterus.     

Age validation and growth of Micropogonias furnieri (Pisces – Sciaenidae) in a temporally open coastal lagoon (South‐western Atlantic – Rocha – Uruguay) based on otolith analysis

In this work 228 individuals of the whitemouth croaker Micropogonias furnieri collected in the Rocha coastal lagoon (Uruguay) from October 1997 to September 1998 were analysed. The species formed annuli in the otolith (sagitta) associated with the opaque zone (narrow opaque annulus), mainly in early winter when water temperature decreased, and reached the lowest values in July–August. The period of greatest growth occurred from December to June, partially overlapping with the spawning period (December–March) and in coincidence with the increase in marginal increment. Growth parameters determined for all individuals were K = 0.19, L _∞ = 30.2 and t₀ = ?2.12. Annual growth increments showed that individuals grew rapidly and attained over 50% of their maximum observed size in the second year of life. In the third year, individuals attained sizes of first maturity at 11–12 cm less than estimates for the Río de la Plata spawning area and coastal areas of Brazil. The increment in length‐at‐age in the Rocha coastal lagoon was smaller than in individuals inhabiting the continental shelf (up to 50 m depth).     

Community ecology of the metazoan parasites of white croaker, Micropogonias furnieri (Osteichthyes: Sciaenidae), from the coastal zone of the State of Rio de Janeiro, Brazil

One hundred specimens of white croakers, Micropogonias furnieri (Desmarest 1823) (Osteichthyes: Sciaenidae) collected from Pedra de Guaratiba (23 degrees 01'S, 43 degrees 38'W), State of Rio de Janeiro, Brazil, from September 1997 to August 1999, were necropsied to study their parasites. The majority of the fish (95%) were parasitized by metazoan. Twenty-eight species of parasites were collected. The nematodes were the 40.5% of the total number of parasites specimens collected. Dichelyne elongatus was the most dominant species. Lobatostoma ringens, Pterinotrematoides mexicanum, Corynosoma australe, D. elongatus, and Caligus haemulonis showed a positive correlation between the host's total length and parasite prevalence and abundance. The monogenean P. mexicanum had differences in the prevalence and abundance in relation to sex of the host. The mean diversity in the infracommunities of M. furnieri was H=0.499+/-0.411, with correlation with the host's total length and without differences in relation to sex of the host. One pair of ectoparasites showed positive covariation, and two pairs of endoparasites showed positive association and covariation between their prevalences and abundances, respectively. Negative association or covariations were not found. The dominance of endoparasites in the croakers parasite infracommunities reinforced the differences found in sciaenids from the South American Pacific Ocean, in which the ectoparasites are dominant.     

Fenology and life cycle of Gracilariopsis tenuifions (Gracilariaceae) at Sucre, Venezuela

The aim of this work was to determine the frequency of different reproductive phases and to induce the germination of spores from tetrasporic and cystocarpic Gracilariopsis tenuifrons from Chacopata and La Pe?a, Venezuela, under controlled laboratory conditions (temperature 22 +/- 1 degree C, 12L:12D photoperiod, salinity of 36 +/-1 PSU and irradiance of 269 microE m(-2) s(-1)). Tetrasporic individuals dominated numerically over gametophitic individuals. The proportion of vegetative algae was very low. Only cystocarpic algae were collected and the spermatangia were absent. Sporulation, germination and formation of algae suggest that they present a Polysiphonia-type life cycle. Algae with reproductive structures were not obtained in the laboratory,     

Mollusc diversity in an Arca zebra (Mollusca: Bivalvia) community, Chacopata, Sucre, Venezuela

The diversity of a subtidal epifaunal mollusk community was studied from September, 1990 to September, 1991 in Chacopata, Sucre State, Venezuela. There were 40 species (24 bivalves and 16 gastropods). The diversity indexes (H' = 2.087, J' = 0.392, 1/D = 0.528) were low when compared with other tropical zones. Monthly diversity reached its maximum in September, 1990 (1.63 bits/ind.) and July, 1991 (1.60 bits/ind.); minimum diversity occurred in June, 1991 (0.52 bits/ind.). A Log series model applied to species abundance data showed a straight line with a diversity index alpha of 5.56. Of 40 species identified, the turkeywing Arca zebra was dominant (69% in number of individuals and 72% of biomass) followed by Pinctada imbricata, Modiolus squamosus, Chama macerophyla and Anadara notabilis. The predatory snails Phyllonotus pomum, Chicoreus brevifrons and Murex recurvirostris seemed to have trophic relationships with A. zebra. The total mean biomass in wet weight (469.20 +/- 263 g m-2, shell included) was high which indicates that A. zebra, a species with a rapid growth rate, occupies a central role in the assemblage as an efficient filter feeder that converts planktonic food into available biomass, supporting one of the most important fisheries in Venezuela.     

Iron and copper in Plagioscion squamosissimus (Piscis: Sciaenidae) from the Orinoco river, Venezuela

Bauxite explotation of the Orinoco River in recent years is an important source of heavy metals discharge in the ecosystem, changing the natural biochemical flow of these elements and their concentrations in water, sediment and organisms. Iron and copper concentrations were measured in the fish Plagioscion squamosissimus in the Orinoco river, by sampling the fish population for three months (September-November 1998) in the main channel of the middle Orinoco (07 degrees 38' 21.2" N; 66 degrees 19' 10.9" W) and in Castillero lagoon (7 degrees 39' 09" N; 66 degrees 09' 00" W) with 2 and 4 cm mesh sizes. The internal organs of 30 fishes per month and site were stove-dried at 80 degrees C, pulverized and dried in disecator for 30 min to use as indicators with the acid digestion method for predicting the effect of heavy metals. We found relatively high values of iron and copper concentrations in fishes of the lagoon, and high seasonal variations in the iron concentration.     

Gametogenesis, histological gonadal cycle and in vitro fertilization in the whitemouth croaker (Micropogonias furnieri, Desmarest, 1823)

The whitemouth croaker (Micropogonias furnieri) is a demersal teleostean fish inhabiting the Atlantic Ocean from northern Venezuela to southern Argentina. In terms of biomass, the whitemouth croaker is the dominant sciaenid in the Río de la Plata and constitutes an important renewable resource for the Uruguayan and Argentinean fisheries. In the present study, analyzed were the gametogenesis and histological gonadal cycle in female and male whitemouth croakers collected at the Uruguayan coast of the Río de la Plata, between March 1997 and February 1998. In addition, the experimental conditions required to obtain mature viable gametes and achieve in vitro fertilization in this species were investigated. These studies indicate that the whitemouth croaker inhabiting the Río de la Plata is a multiple spawner, which reproduces on the Uruguayan coast between October and February. In vitro studies showed that following activation, sperm remain motile for up to 40 min, and under optimal dilution conditions that they retain a high fertilization capability for 15 min. Taken together these results could support future aquaculture research and exploitation of this species.     

Physical properties of the agar of Gracilariopsis tenuifrons (Gracilariacea) from Sucre, Venezuela

The yield, gel strength, gelling and melting temperatures of Gracilariopsis tenuifrons agar from Guayacán, Araya Peninsula, Sucre State, Venezuela were determined. Yield values with and without alkali treatment ranged from 23.22 to 39.57% and from 16.29 to 22.42% respectively, while gel strength with alkali treatment fluctuated betwen 699.31 and 1231.69 g/cm2 and without treatment varied from 278.0 to 691.06 g/cm2. Gelling and melting temperatures were in the range reported for other agarophytes. Considering gel strength, the agar quality of G. tenuifrons was higher than in other species and its exploitation in economically feasible.     

Effects of salinity and weight on routine metabolism in the juvenile croaker, Micropogonias furnieri (Desmarest 1823)

Juvenile croakers from a brackish water bay showed minimal oxygen consumption rates at salinities between 17–19.     

First record of Cynoscion regalis (Pisces,Sciaenidae) in Portuguese continental waters

The occurrence of Cynoscion regalis in Portuguese continental waters is reported for the first time, with six specimens collected in 2015 from three areas: Tagus Estuary, Sado Estuary and Praia da Vieira (central‐west coast). Analyses of morphometric and meristic characteristics confirmed all six specimens as C. regalis; further validation was obtained by sequencing a 675 bp region of the mitochondrial cytochrome c oxidase I gene. These records constitute a range extension of C. regalis into the southern north‐east Atlantic Ocean.