Ana Cristina Teixeira Bonecker

Seasonal variation in fish larvae at the entrance of Guanabara Bay, Brazil

Devido a crescente acao antropica a qual esta sujeita e sua importância socio-economica, a baia de Guanabara vem despertando grande interesse na comunidade cientifica. O presente trabalho objetivou analisar a variacao quali-quantitativa temporal das larvas de peixes, relacionar a densidade das larvas com o ciclo nictemeral e verificar a influencia dos ciclos de mare. Foram realizadas coletas, em um ponto localizado na entrada da baia, em setembro de 1995 e marco de 1996. As coletas ocorreram nas mares de enchente e vazante ao longo de tres dias. Os arrastos foram obliquos, utilizando uma rede do tipo bongo com malhas de 500 µm. Foi coletado um total de 42 taxons. As familias Engraulidae (Cetengraulis edentulus e Anchoa lyolepis) e Clupeidae (Harengula jaguana) ocorreram em grandes densidades e dominaram nas duas campanhas. As maiores densidades de larvas de peixes ocorreram durante a campanha de marco, que apresentou altas temperaturas e baixas salinidades. Observou-se um padrao nictemeral em relacao a abundância de larvas, com altas densidades durante a noite e baixas durante o dia. Os altos indices de diversidade encontrados ressaltam a importância desse ecossistema para varias especies de peixes.

Occurrence and distribution of larval lanternfish (Myctophidae) from the southwest Atlantic Ocean

This study analyzes the occurrence and distribution of lanternfish (Myctophidae) larvae along the Brazilian coast (12-22oS) between 200 m and the surface. Three cruises were conducted during the spring/1998, winter/1999 and autumn/2000. A total of 3,394 lanternfish larvae were identified representing 27 species and Lepidophanes guentheri (Goode & Bean, 1896) was the most abundant. Most of the identified taxa were in the postflexion stage. Myctophid larvae were more numerous during the winter. Most taxa were distributed widely from 12-22oS, including some seamounts, and occurred mainly outside the 1,000 m isobath. Although there was no difference in the myctophid community among the coastal, oceanic and seamount regions it was significantly different during the three seasons. During the spring and autumn Hygophum reinhardtii (Lutken, 1892) was the discriminating species while in the winter there were more L. guentheri.

Larval fish of the Campos Basin, southeastern Brazil

Studies on the vertical distribution of larval fish in water masses along the Brazilian coast are very rare. The present study aimed to identify larval fish occurring in the surface (1 m) layer and at depth in four water masses of the Campos Basin, southeastern Brazil: South Atlantic Central Water (SACW) (250 m), Antarctic Intermediate Water (AAIW) (800 m), Upper Circumpolar Deep Water (UCDW) (1,200 m) and North Atlantic Deep Water (NADW) (2,300 m). Material used in this study was obtained in 2009 through nocturnal horizontal stratified hauls using a Multinet (500 μm mesh size) during both rainy (February to April) and dry periods (August to September). A total of 10,978 fish larvae comprising 169 taxa were identified during the rainy (n = 6,015) and dry (n = 4,963) periods. The number of taxa decreased as the sampling depth increased. Larvae of Clupeidae, Engraulidae and Scombridae dominated in samples collected in the surface layer, while Sternoptychidae and Myctophidae were the most representative families in SACW. The other three water masses were dominated by Gonostomatidae larvae.

Occurrence of Gobiidae larvae in a tropical Brazilian estuary, with particular emphasis on the use of size classes to categorize species guilds

The structure and seasonal dynamics of larvae of the Gobiidae family in the Mucuri Estuary (Bahia, Brazil) were studied for nine consecutive years. Sampling was conducted at three stations in the lower estuary channel, between 2002 and 2010, in relation to season, day and night and tidal variations. A total of 5802 Gobiidae larvae, representing 15 taxa (12 species and three morphotypes), were collected in the Mucuri Estuary during this time. The highest mean ± s.d. density of fish larvae, 54·7 ± 79·8 larvae 100 m(-3), was recorded during the flood tide and night sampling. Ctenogobius boleosoma was the most abundant species (68%), being dominant in the rainy and dry seasons and had a long reproductive period. This species was classed as a marine estuarine-opportunist because it was observed at high frequencies and active larvae entering the estuary between 6·1 and 12·0 mm standard length (L(S)). Gobionellus oceanicus, second in abundance (12%), occurred only in later larval stages but did not use the estuary as a preferred location for spawning, being classed a marine estuarine dependent. Microgobius carri (11%) was represented in all L(S) classes and was resident in the estuary for spawning, remaining there throughout their life cycle. The other species were considered rare due to their low densities and could not be classified in any guild.

Description and distribution of the larvae of two species of Fistulariidae (Teleostei, Syngnathiformes) in the southeastern Brazil

Fistulariidae contains the single genus, Fistularia, with four species. Two of these species are recorded from Brazil: Fistularia petimba and F. tabacaria. This study describes larvae of these two species of Fistularia, recording their distribution along the southeastern Brazilian coast, which is limited in the north by Real River (12° S) and in the south by Sao Tome Cape (22° S). Samples were collected using a bongo net with mesh apertures of 330 and 500 µm during three oceanographic cruises conducted on spring/98 (Central III), winter/99 (Bahia 1) and autumn/00 (Central IV). The net was towed obliquely and the maximum depth was 200 m. Larvae of F. petimba were the most abundant and most widely distributed within the study area, including the seamounts of the Vitoria-Trindade Ridge. Larvae of F. tabacaria were recorded only between 14° S and 21° S.

Vertical distribution of mesozooplankton and ichthyoplankton communities in the South-western Atlantic Ocean (23°14′1″S 40°42′19″W)

ana c. t. bonecker, cristina de o. dias, marcia s. de castro, pedro f. de carvalho, adriana v. araujo, rodolfo paranhos, anderson s. cabral and sergio l. c. bonecker Universidade Federal do Rio de Janeiro, Instituto de Biologia, Departamento de Zoologia, Av. Carlos Chagas Filho, 373 – Prédio do CCS, Bloco A, Sala A0-084, Ilha do Fundão – 21.941-902, Rio de Janeiro, RJ, Brasil, Universidade Federal do Rio de Janeiro, Laboratório de Hidrobiologia, Departamento de Biologia Marinha, Instituto de Biologia, Av. Carlos Chagas Filho, 373 – Prédio do CCS, Bloco A, Cidade Universitária, Ilha do Fundão – 21.941-902, Rio de Janeiro, Brasil

Can we assess the ecological status of estuaries based on larval fish assemblages

Fish larvae of four SE Brazilian estuaries were investigated to assess if the larval fish assemblages reflect the ecological status of estuaries. All samples were collected in the same water mass to guarantee similar natural water parameters, assuring that major differences among estuaries were related to anthropogenic pressures. Water temperature, oxygen, pH, chlorophyll a, faecal coliforms, nutrient load and total particulate matter were obtained at each sampling area. A pressure index was used to assess the overall anthropogenic pressures acting in each estuary. Results showed that fish larvae were sensitive to water contamination, reducing the diversity and especially exhibiting a high dominance of few species. Furthermore, this study reinforced the idea that the high sensitivity of fish larvae can increase the accuracy of the environmental assessments when tackling short-time events of hydrological controls (physical barriers and control of the freshwater input), representing an advance in the water ecological quality assessments.

Larval and juvenile development of Tatia intermedia (Siluriformes: Auchenipteridae)

This study describes the morphology, morphometry and meristic characters of larval and juvenile Tatia intermedia collected in the middle Tocantins River and some of its tributaries. Six larvae of T. intermedia were examined and they have a moderately elongate body, head slightly dorso-ventrally depressed with a convex snout, small and round eyes and a subterminal mouth. In five juvenile stages observed, the head and eye are relatively smaller than in the larval stage and the snout remains convex and mouth becomes terminal.

Larval fish collected from sound‐scattering layers in an offshore tropical area

The composition of the larval fish assemblage in the sound-scattering layer of the continental shelf waters off the coast of south-eastern Brazil (12 and 22° S), a research project that is part of the Brazilian programme Avaliação do Potencial Sustentável de Recursos Vivos na Zona Econômica Exclusiva (REVIZEE), is described. Samples were collected during daylight hours and at dusk at five oceanographic stations in the winter of 1999 using an Isaacs-Kidd Midwater Trawl (IKMT). The oceanographic stations were chosen based on the detection of plankton layers by acoustic observation. A total of 2192 larval fish were identified, comprising 52 families and 62 species. Maurolicus stehmanni (Sternoptychidae) was the most abundant species found within the study area, comprising 18·5% of all identified larvae, followed by Psilotris celsus (Gobiidae) at 10·9%.