?Trophic switch' by catfish community from predation to scavenging modulated by human food discard in an estuarine bay.

Benthic predatory catfishes are voracious and opportunistic predators and can easily shift their diet according to the availability of prey. In this study, feeding ecology of catfishes from two adjacent habitats of an estuarine bay is compared. The lower bay was relatively pristine as compared to the upper bay and was represented by two families of catfishes-Plotosidae and Ariidae, while the upper bay represented only ariid catfishes. Gut content analysis revealed that catfish predators from lower bay consumed conventional prey like teleosts and benthic invertebrates with a linear pattern of ontogenetic dietary shift. Plicofollis dussumieri and Plotosus canius occupied the position of top predators in the lower bay and were specialized feeders. Other predators like Plotosus lineatus, Arius arius, Arius jella, and Arius maculatus were generalist feeders occupying the position of mesopredators. However, in the upper bay, the catfish predators represented by Arius maculatus, Arius jella, and Arius arius predominantly fed on human discarded food. The easily available human food in the form of chicken, corn, and rice as noted from the investigated guts shows altered trophic guilds of ariid catfishes wherein only mid to large-sized catfish community was noted in this bay. A distinct "trophic switch" altered the trophic function from predation to scavenging which was observed in their feeding behavior. The anthropogenic impact in the form of unmanaged organic waste alters the role of predatory catfishes thereby restructuring the food web that may lead to unknown changes in the estuarine benthic ecosystems resulting in reduced ecosystem services.

Sexual dimorphism and reproductive biology of Cephalocassis borneensis (Siluriformes: Ariidae), a paternal mouth-brooding fish in the Mekong River.

Information on the reproductive biology of fish species is essential for fisheries management, conservation and culture potential assessment. Therefore, this study aimed to understand the sex-based morphological differences and reproductive characteristics of Cephalocassis borneensis, an ariid species with a rapid decline of wild populations. Fish samples were collected monthly from local fishermen (n = 1092) in the Vietnamese Mekong River over a year. Morphological analyses revealed that sexual dimorphism was observed in mature, but not immature, fish. The length at first maturity (Lm ) was smaller for males (11.5 cm) than for females (12.5 cm). Mature males had larger head length and pre-pectoral distance than mature females, increasing the space for oral incubation of fertilized eggs and larvae in males. Conversely, females were larger in three head parameters (head angle, head width and head depth) and three abdomen parameters (body deep, ventral fin length and distance between pectoral and ventral fin) involved in ovary development. Paternal mouth-brooding behaviour is an important reproductive strategy in C. borneensis to increase offspring survival. Monthly variations in gonado-somatic index and condition factor (K) and the presence of maturation stages indicated that C. borneensis spawns year-round, mainly in the rainy season from June to October. This species' fecundity was relatively low, from 10 to 31 eggs per female of quite large sizes (about 7.30 ± 0.68 mm in diameter). Besides, non-functional oocytes (hyaline eggs) of smaller size (<3 mm) were found in the females' ovaries. Low fecundity with large eggs and paternal care indicated that the species is an equilibrium strategist. These characteristics are critical in developing ariid species conservation plans, such as setting the time and mesh-size for fishing, and domestication programmes in artificial conditions.

Biology and ecology of sea catfish (Ariidae) of estuarine, lagoon and coastal ecosystems in West Africa.

The family Ariidae, sea catfish of the order Siluriformes, is widely distributed throughout the world, particularly in tropical and subtropical areas. The three species of Ariidae found on the coasts and estuaries of West Africa are the smoothmouth catfish Carlarius heudelotii (Valenciennes 1840), the rough-head catfish Carlarius latiscutatus (Günther 1864) and the Guinean sea catfish Carlarius parkii (Günther 1864). They have been increasingly exploited by artisanal and industrial coastal fisheries in recent decades, but there is still little information available on their ecology and biology. The aim of this study was to deepen our knowledge of these three West African Ariidae species based on a dataset collected between 1980 and 2013 during experimental fishing programmes. They were carried out in Mauritania in the Banc d'Arguin National Park, in Senegal in the Sine Saloum estuary including the Bamboung Marine Protected Area (MPA), in The Gambia in the Gambia estuary, in Guinea-Bissau in the Urok Islands MPA in the Bijagos archipelago, in Guinea in the Fatala estuary and Dangara inlet, and in Côte d'Ivoire in the Ebrié Lagoon. C. latiscutatus accounted for 65%, C. parkii for 29% and C. heudelotii for 6% of total number of Ariidae sampled. C. latiscutatus was abundant in the Sine Saloum and Gambia estuaries as well as in Guinea and Guinea-Bissau and was the only species present in the Ebrié Lagoon. C. parkii was in the majority in Mauritania. The three species were recorded in a salinity range of 0 to 50, a temperature range of 19 to 34°C, in areas 1.7 to 15 m depth, and transparency ranging from 0.1 to 4 m (Secchi disk depth). C. heudelotii was present in less saline (25 vs. 32-34), less warm (27 vs. 29°C) and less transparent (0.8 m vs. 1.6 m) waters than the two other species. The maximum sizes (453 mm, 614 mm and 525 mm for, respectively, C. heudelotii, C. latiscutatus and C. parkii) were comparable to those recorded at sea. Length-weight relationships calculated for each species showed b coefficients greater than 3. Sex ratios were always in favour of females. The number of mature individuals and their smallest size at maturity were calculated per species, sex and study area. A size of 27-28 cm at first maturity was estimated for females of C. latiscutatus. A few dozen records made it possible to describe fecundity and cases of oral incubation by females. The diet of the three species was composed of crustaceans, fish and molluscs, confirming their classification as generalist predators. Thanks to their high environmental tolerance, these sea catfish populations are able to occupy both the continental shelf and adjacent estuaries throughout their life cycle, with the exception of spawning, which generally takes place at sea.

Morphological and molecular (28S rRNA) data of monogeneans (Platyhelminthes) infecting the gill lamellae of marine fishes in the Campeche Bank, southwest Gulf of Mexico.

During the examination of 913 fish specimens belonging to four families in the Campeche Bank (Gulf of Mexico), 23 gill ectoparasitic monogenean species were found, which belong to three families: Dactylogyridae, Microcotylidae and Diclidophoridae. The species Euryhaliotremaamydrum, E.carbuncularium, E.dunlapae, E.fajeravilae, E.fastigatum, E.longibaculum, E.paracanthi, E.tubocirrus, Haliotrematoidescornigerum, H.gracilihamus, H.heteracantha, H.longihamus, H.magnigastrohamus, H.striatohamus, Hamatopedunculariabagre, Neotetraonchusbravohollisae, and N.felis (all Dactylogyridae) were found on the hosts Lutjanussynagris, L.griseus, Ariopsisfelis, Bagremarinus, Archosargusrhomboidalis, and Haemulonplumieri. Additionally, Microcotylearchosargi, Microcotyle sp., and Microcotyloidesincisa (all Microcotylidae) were found on L.griseus and A.rhomboidalis; finally, Choricotyle sp. 1, Choricotyle sp. 2, and Choricotyle sp. 3 (all Diclidophoridae) were found on H.plumieri. The prevalence, abundance, mean intensity of infection, and supplementary taxonomic revisions for all monogeneans found are provided. Partial sequences of the 28S rRNA gene were also obtained for monogeneans of ariid, sparid, and haemulid host fishes to explore their systematic position within the Monogenea. New locality and host records for some previously described species of Euryhaliotrema, Hamatopeduncularia, Microcotyle, and Choricotyle from lutjanid, ariid, sparid, and haemulid hosts were reported. The present study adds evidence supporting the interoceanic occurrence of the same monogenean species (on lutjanids) on the west-east Atlantic and Pacific Oceans (= amphiamerican species). As previously suggested, there are at least, two possibilities to explain that parasite distribution: differentiation of morphological features in these monogeneans have resulted in only slight to insignificant morphological changes developing over the extended period of 3.2 mya (when the Isthmus of Panama was closing) and/or speciation is only evident at molecular level.

Isotopic niche of the catfishes Bagre bagre and Genidens barbus in a coastal area of south-eastern Brazil / Nicho isotópico dos bagres Bagre bagre e Genidens barbus em área costeira do sudeste do Brasil

Abstract: The isotopic niche of Bagre bagre and Genidens barbus target of commercial fisheries in a marine coastal area from northern Rio de Janeiro State (~21ºS), south-eastern Brazil was compared to evaluate the feeding assimilation and the trophic relationship. The mean isotopic values of the catfishes and their food items in the δ13C-δ15N space were coherent with their respective trophic positions. The relative contributions of the food items highlighted the shrimp Xiphopenaeus kroyeri as the most assimilated item in the diet of B. bagre, while for G. barbus the model highlighted the fish Porichthys porosissimus. The absence of niche overlap together with the trophic evenness point to a reduced feeding overlap between B. bagre and G. barbus in northern Rio de Janeiro State.

Resumo: O nicho isotópico de Bagre bagre e Genidens barbus alvos de pescarias comerciais em uma área costeira marinha do norte do estado do Rio de Janeiro (~21ºS), sudeste do Brasil, foi comparado para avaliar a assimilação alimentar e a relação trófica. Os valores isotópicos médios dos bagres e de seus itens alimentares em δ13C-δ15N foram coerentes com suas respectivas posições tróficas. As contribuições relativas dos itens alimentares destacaram o camarão Xiphopenaeus kroyeri como o item mais assimilado na dieta de B. bagre, enquanto para G. barbus o modelo destacou o peixe Porichthys porosissimus. A ausência de sobreposição de nicho juntamente com a uniformidade trófica aponta para uma sobreposição alimentar reduzida entre B. bagre e G. barbus no norte do estado do Rio de Janeiro.

The complete mitochondrial genome of Arius arius (Siluriformes: Ariidae).

The threadfin sea catfish (Arius arius) belongs to the genus Arius in Ariidae. In this paper, we initially determined the complete mitochondrial genome of Arius arius. The mitochondrial genome is 16, 711 bp in length, with the base composition on the heavy strand: A - 29.67%, T - 25.38%, C - 29.70% and G - 15.25%. It has the typical vertebrate mitochondrial gene arrangement, including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region. Phylogenetic analysis showed that A. arius was clustered into the order of Siluriformes, and closely related to species in the family of Siluridae. The present study would contribute to genetic resources conservation and systematics study of A. arius.

Hábito alimentar do bagre sciades herzbergii (Siluriformes, Ariidae) da ilha dos caranguejos, Maranhão, Brasil / Feeding habits of the catfish sciades herzbergii (Siluriformes, Ariidae) in caranguejos island, Maranhão, Brazil

The article describes the feeding habits of the catfish Sciades herzbergii caught in the Crabs Island (Ilha dos Caranguejos), an important coastal area of the Maranhão state, Brazil. A total of 167 individuals were collected: 110 females and 57 males. All the stomach contents were identified to the closest taxonomic level. The frequency of occurrence, biomass, numerical frequency and index of relative importance (IRI) of food items were determined for both genders. Stomach repletion was predominant, demonstrating good feeding conditions for S. herzbergii. The main alimentary items in the diet of this catfish were crustaceans, fish, oligochaets and polychaets, and the decapods crustaceans were the most representative.

Plasma ion levels of freshwater and marine/estuarine teleosts from Southern Brazil

The purpose of this study was to investigate Na+, Cl-, K+, Ca2+, and Mg2+ levels in the plasma of freshwater and marine/estuarine teleosts collected at different salinities (0 to 34) from the estuarine and freshwater portions of the São Gonçalo channel in Southern Brazil. Any relationship between plasma ion levels and salinity and the capacity of ionic regulation of teleosts found at three or more different salinities (Genidens barbus and Micropogonias furnieri) was also investigated. Results showed no relationship between plasma ion levels and salinity when considering all species together, but the two species collected from three or more different salinities showed a significant positive relationship between plasma ion levels and salinity, indicating that G. barbus and M. furnieri have a high capacity to regulate plasma ion levels at both low and high salinities.

A proposta deste estudo foi investigar os níveis de Na+, Cl-, K+, Ca2+, and Mg2+ no plasma de teleósteos de água doce e marinhos/estuarinos coletados em diferentes salinidades (0 a 34) nas porções de água doce e estuarinas do Canal São Gonçalo, sul do Brasil. Uma possível relação entre os níveis iônicos plasmáticos e a salinidade também foi investigada bem como a capacidade de regulação iônica dos teleósteos coletados em três ou mais salinidades (Genidens barbus e Micropogonias furnieri). Os resultados mostraram que não houve relação entre os níveis iônicos no plasma com a salinidade quando considerando todas as espécies juntas, mas as duas espécies coletadas em três ou mais salinidades mostraram uma relação significativamente positiva entre níveis iônicos no plasma e salinidade, mostrando que G. barbus e M. furnieri apresentaram uma grande capacidade para regular os íons do plasma em baixas e altas salinidades.

Taxocenose de bagres marinhos (Siluriformes, Ariidae) da região estuarina de São Vicente, SP, Brasil / Taxocenose of marine catfish (Siluriformes, Ariidae) in the complex bay-estuary of São Vicente, SP, Brazil

O objetivo do trabalho foi analisar a taxocenose de bagres marinhos do complexo baía-estuário de São Vicente, SP. As coletas foram mensais, no período de setembro de 2000 a agosto de 2002, em quatro regiões do estuário. Foram capturados 3.985 exemplares, pertencentes a cinco gêneros e seis espécies, totalizando 47.807 g. A espécie Cathorops spixii apresentou a maior abundância numérica com 1.569 indivíduos amostrados. No transecto I (próximo da região costeira) foi registrada a maior riqueza e no transecto IV (estuário acima) a maior abundância com 2.602 exemplares e peso de 26.236 g. Em março de 2002 registrou-se a maior abundância com 687 indivíduos e o maior peso ocorreu em fevereiro de 2002 (8.816 g). A salinidade da água de fundo, ao longo do período de estudo, variou entre 14 e 36 e a temperatura da água variou entre 19 e 30 ºC. Na região amostrada foram capturados exemplares jovens e adultos, ocorrendo um predomínio de jovens, o que demonstra que esta área apresenta condições favoráveis para crescimento.

The purpose of this study was to analyze the taxocenose of marine catfish in the complex bay-estuary of Sao Vicente, Brazil. The sampling was done monthly from September/2000 to August/2002, in four places of the estuary. Were caught 3.985 individuals belonging for 5 genus and 6 species, totalizing 47.807 g. The specie Cathorops spixii showed the biggest plentiful with 1.569 individuals sampled. In the transect I (close to the coastal region), it was registered the biggest richness (6 species) and in the transect IV (upper estuary) the biggest number of individuals (n = 2.602) e weight of 26.236 g. In March/2002 were registered the biggest occurrence with 687 individuals and biggest weight in February/2002 (8.816 g). The bottom water salinity, in the time of study, changed between 14 and 36, and the water temperature varied between 19 and 30 ºC. In the sample place juveniles and adults' individuals were caught, a mostly juvenile which demonstrates that of this place shows favorable conditions for growth.

Ontogenetic and seasonal shifts in the diet of the pemecou sea catfish Sciades herzbergii (Siluriformes: Ariidae), from a macrotidal mangrove creek in the Curuçá estuary, Northern Brazil

The feeding ecology of pemecou sea catfish (Sciades herzbergii) was studied bimonthly from September 2003 to July 2004 in a macrotidal mangrove creek at Curuçá estuary, Brazil. Feeding activity and relative importance of prey groups were assessed in 528 and 226 specimens (6.2 to 36.0 cm total length), respectively, using stomach contents. A total of 1 820 specimens were caught. The fish left the creek with an average of 2.2 % of their body weight in prey. Feeding activity was lower in the dry season (September and November 2003) than in the rainy season (January to May 2004). The diet was dominated by Ocypodidae and Grapsidae. Feeding strategies of the pemecou sea catfish indicated a slight variation between the diets of adults and juveniles; however; the main factor leading to diversification in the diet were the seasons. Opportunistic feeding behavior was observed in the dry season, shifting to more specialized feeding in the wet season. This temporal diet shift may be explained by the environmental seasonal variations (e.g. transparency of the water, high water level) in the intertidal mangrove creek habitat. Rev. Biol. Trop. 56 (2): 861-873. Epub 2008 June 30.

Estudiamos la ecología trófica del bagre guatero Sciades herzbergii, con periodicidad bimestral, desde septiembre de 2003 a julio de 2004, en un canal de marea del estuario del río Curuçá, norte de Brasil. Del total de 1820 ejemplares capturados, analizamos la actividad alimentaría y la importancia de las diferentes fuentes de alimento por evaluación de los contenidos estomacales de 528 y 226 ejemplares (longitud corporal 6,2 a 36,0 cm), respectivamente. S. herzbergii sale del canal de marea con un valor promedio de 2,2 % de su peso corporal como alimento. El ritmo alimentario fue menor durante el período seco (septiembre a noviembre de 2003) que en el lluvioso (enero a mayo de 2004). Los análisis de los contenidos estomacales de 226 ejemplares indicaron una dieta con predominio de Ocypodidae y Grapsidae. Las estrategias alimentarías de S. herzbergii mostraron pequeñas diferencias entre las dietas de los adultos y de los jóvenes, pero la variación estacional fue el factor que mejor definió la diversificación de la dieta. En el período seco hubo un comportamiento oportunista en la alimentación, cambiando a una dieta mas especializada durante el período lluvioso. Esta variación temporal en la dieta corresponde con la variación estacional en los hábitats del canal de marea.