Oceanographic scenario and fish larval distribution off Guinea-Bissau (north-west Africa)

2014 ◽  
Vol 95 (3) ◽  
pp. 435-452 ◽  
Author(s):  
M.P. Jiménez ◽  
R.F. Sánchez-Leal ◽  
C. González ◽  
E. García-Isarch ◽  
A. García
Keyword(s):  
Surface Waters ◽  
Larval Fish ◽  
Fish Larvae ◽  
Inner Shelf ◽  
North West ◽  
Guinea Bissau ◽  
Larval Distribution ◽  
Océanographic Survey ◽  
Continental Runoff ◽  
Abundance And Diversity

This paper describes the hydrography and the larval fish assemblage of Guinea Bissau waters, and analyses the spatial distribution of the main families in relation to the oceanographic features of the area. Data were obtained during an oceanographic survey, undertaken between October and November 2008. In addition to 98 demersal fishing hauls, a total of 33 stations, located between 20 and 1000 m depth, were sampled for hydrography and ichthyoplankton. Data showed that Guinea-Bissauan surface waters are characterized by a strong thermohaline front that flows parallel to the bathymetry of the area. Warm surface waters (SST > 29°C) occupy the inner shelf, and colder (SST < 26°C), chlorophyll-a-rich waters take over the shelf break. Continental runoff seems responsible for the low salinity of the inner-shelf waters whereas the colder types bear thermohaline features typical of tropical Atlantic waters. These features define a scenario which favours the development of fish early life stages, reflected in the high abundance and diversity of fish larvae recorded. A total of 84 taxa of fish larvae were identified. Only the family Clupeidae accounted for 54.8% of the sampled larvae. Other important families were Carangidae (8.8%), Sparidae (8.4%) and Myctophidae (5.9%).

Temporal patterns in distributions of tropical fish larvae on the North West Shelf of Australia

2004 ◽  
Vol 55 (5) ◽  
pp. 473 ◽  
Author(s):  
A. Sampey ◽  
M. G. Meekan ◽  
J. H. Carleton ◽  
A. D. McKinnon ◽  
M. I. McCormick
Keyword(s):  
Southern Oscillation ◽  
Fish Larvae ◽  
Early Stage ◽  
Larval Survival ◽  
Zooplankton Biomass ◽  
Tropical Fish ◽  
North West ◽  
Larval Fishes ◽  
The North ◽  
Abundance And Diversity

Information on the temporal distributions of tropical fish larvae is scarce. Early stage larval fishes were sampled using towed bongo plankton nets at sites on the southern North West Shelf of Australia (21°49′S, 114°14′E), between October and February of 1997/98 and 1998/99. The first summer was characterised by El Niño–Southern Oscillation-driven upwelling and high primary productivity, whereas in the second summer water temperatures were warmer and primary production was lower. Benthic percoid shorefishes dominated surface assemblages in both summers and this pattern may be typical of tropical shelf environments.The abundance and diversity of larval fishes were lowest in October and increased from November through to February. Assemblages displayed weak cross-shelf patterns, with a few taxa being more abundant at inshore sites (e.g. monacanthids), whereas others were more abundant offshore (e.g. scombrids). Although the composition of assemblages remained relatively consistent, many taxa (e.g. pomacentrids and carangids) showed differences in abundance between summers. Multivariate analyses found no relationships between abundance patterns of larval fishes and biophysical variables, such as temperature, salinity, and zooplankton biomass. Thus, seasonal changes in abundance may reflect differences in the spawning activities of adult fishes and/or larval survival.

scholarly journals The Larval Fish Fauna of the “Canal de Santa Cruz” - Estuary in Northeast Brazil.

2001 ◽  
Vol 29 (2) ◽  
Author(s):  
Werner EKAU ◽  
Petra WESTHAUS-EKAU ◽  
Silvio José de MACÊDO ◽  
Christian von DORRIEN
Keyword(s):  
Larval Fish ◽  
Fish Larvae ◽  
Fish Fauna ◽  
Taxonomic Composition ◽  
Larval Abundance ◽  
Nursery Ground ◽  
Geographical Patterns ◽  
Larval Distribution ◽  
High Concentrations ◽  
Inner Channel

was investigated. The larval distribution in the channel was analysed based on 187 samples from 9 stations collected from November 1993 to May 1994. 50 of these samples were used to investigate the taxonomic composition. Larval densities varied between 0 and 376 ind. per 50 m³. Seasonal and geographical patterns were found. Both in dry and rainy season larval abundance was low at the inner channel. Except a few hauls, most samples did not exceed densities of 25 or 45 ind./50 m³, respectively. High concentrations beyond 100 ind. per 50 m³ were found at station 2, 3 and once at station 8 in the northern part and at station 7 in the southern part of the channel. Engraulidae larvae and different types of Gobiidae were the dominant groups in the channel. These two families reached almost 76% of the whole ichthyoplankton in the catches. They are followed by Achiridae, Clupeidae, Terapontidae, Sciaenidae, Tetraodontoidei, Carangidae, Syngnathidae, Cottidae (?) and Blennioidei (summing up to 95% of the caught fish larvae in the channel). Nearly all groups are found as adults in the channel. Only five families are represented exclusively by larvae: Achiriidae, Cottidae, Terapontidae, Exocoetidae and Ephippidae. From the latter, only Exocoetidae form an oceanic group. Based on the taxa composition, it is assumed, that the importance of the estuary as nursery ground for shelf and oceanic fish is low. Key words: Ichthyoplankton; estuary; larval distribution;

scholarly journals Spatio-temporal distribution of fish larvae in relation to ontogeny and water quality in the oligohaline zone of a North Brazilian estuary

2013 ◽  
Vol 13 (3) ◽  
pp. 55-63 ◽  
Author(s):  
Valérie Sarpedonti ◽  
Érica Moema Silva da Anunciação ◽  
Adriana Oliveira Bordalo
Keyword(s):  
Larval Fish ◽  
Fish Larvae ◽  
Temporal Distribution ◽  
Capital City ◽  
Rainy Period ◽  
Larval Distribution ◽  
Spatio Temporal ◽  
The City ◽  
Urban Activity ◽  
Distribution Of Fish

Larval fish assemblage in Guajará Bay was studied through four quarterly field campaigns and discussed in relation to individuals' development stages and exposure to contaminants poured out by the Pará State Capital City, Belém. Larval densities were low and diversity extremely poor with a strong dominance of clupeids, engraulids and, to a lower extent, sciaenids. The main spawning season was registered at the onset of the rainy period. Pre-flexion and flexion clupeiforms remained in the farmost stations from the city while post-flexion larvae were found near urban activity centres. Unlikely, pre-flexion and flexion sciaenids were scattered along the city waterfront. Post-flexion larvae were rare; it is suggested that sciaenids use the bay as a transitory route between their spawning grounds and more distant nursery grounds. The waters around the city of Belém showed signs of contamination. However, based on the literature, Guajará Bay environmental quality at the time of the study was suitable for fish larvae life. Nitrate with pH best explained larval distribution.

scholarly journals Fish larvae exploit edge vortices along their dorsal and ventral fin folds to propel themselves

2016 ◽  
Vol 13 (116) ◽  
pp. 20160068 ◽  
Author(s):  
Gen Li ◽  
Ulrike K. Müller ◽  
Johan L. van Leeuwen ◽  
Hao Liu
Keyword(s):  
Larval Fish ◽  
Fish Larvae ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Bony Fish ◽  
The Body ◽  
Functional Explanation ◽  
Image Velocimetry ◽  
Median Fins

Larvae of bony fish swim in the intermediate Reynolds number ( Re ) regime, using body- and caudal-fin undulation to propel themselves. They share a median fin fold that transforms into separate median fins as they grow into juveniles. The fin fold was suggested to be an adaption for locomotion in the intermediate Reynolds regime, but its fluid-dynamic role is still enigmatic. Using three-dimensional fluid-dynamic computations, we quantified the swimming trajectory from body-shape changes during cyclic swimming of larval fish. We predicted unsteady vortices around the upper and lower edges of the fin fold, and identified similar vortices around real larvae with particle image velocimetry. We show that thrust contributions on the body peak adjacent to the upper and lower edges of the fin fold where large left–right pressure differences occur in concert with the periodical generation and shedding of edge vortices. The fin fold enhances effective flow separation and drag-based thrust. Along the body, net thrust is generated in multiple zones posterior to the centre of mass. Counterfactual simulations exploring the effect of having a fin fold across a range of Reynolds numbers show that the fin fold helps larvae achieve high swimming speeds, yet requires high power. We conclude that propulsion in larval fish partly relies on unsteady high-intensity vortices along the upper and lower edges of the fin fold, providing a functional explanation for the omnipresence of the fin fold in bony-fish larvae.

scholarly journals Osmotic induction improves batch marking of larval fish otoliths with enriched stable isotopes

2014 ◽  
Vol 71 (9) ◽  
pp. 2530-2538 ◽  
Author(s):  
Emmanuel de Braux ◽  
Fletcher Warren-Myers ◽  
Tim Dempster ◽  
Per Gunnar Fjelldal ◽  
Tom Hansen ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Salmo Salar ◽  
Larval Fish ◽  
Fish Larvae ◽  
Cost Effective ◽  
Industrial Applications ◽  
Chemical Markers ◽  
Potential Applications ◽  
Recent Method ◽  
Batch Marking

Abstract Otolith marking with enriched stable isotopes via immersion is a recent method of batch marking larval fish for a range of research and industrial applications. However, current immersion times and isotope concentrations required to successfully mark an otolith limit the utility of this technique. Osmotic induction improves incorporation and reduces immersion time for some chemical markers, but its effects on isotope incorporation into otoliths are unknown. Here, we tested the effects of osmotic induction over a range of different isotope concentrations and immersion times on relative mark success and strength for 26Mg:24Mg, 86Sr:88Sr and 137Ba:138Ba on Atlantic salmon (Salmo salar) larvae. 71% and 100% mark success were achieved after 1 h of immersion for 86Sr (75 µg L−1) and 137Ba (30 µg L−1) isotopes, respectively. Compared with conventional immersion, osmotic induction improved overall mark strength for 86Sr and 137Ba isotopes by 26–116%, although this effect was only observed after 12 h of immersion and predominately for 86Sr. The results demonstrate that osmotic induction reduces immersion times and the concentrations of isotope required to achieve successful marks. Osmotically induced isotope labels via larval immersion may prove a rapid and cost-effective way of batch marking fish larvae across a range of potential applications.

scholarly journals Feeding of the Brycon cephalus, Triportheus elongatus and Semaprochilodus insignis (osteichthyes, characiformes) larvae in Solimões/Amazonas River and floodplain areas.

2002 ◽  
Vol 32 (3) ◽  
pp. 499-499 ◽  
Author(s):  
Rosseval Galdino LEITE ◽  
Carlos A.R.M. ARAUJO-LIMA
Keyword(s):  
Food Item ◽  
Prey Size ◽  
Larval Fish ◽  
Fish Larvae ◽  
Trophic Relations ◽  
Fish Feeding ◽  
Important Species ◽  
Flooded Forests ◽  
Commercially Important

Information on larval fish feeding is essential for understanding their trophic relations, including the management in conditions totally or partially controlled by humans. An experiment was designed to evaluate the larval diets of three commercially important species. Four varzea-lakes and the adjacent river were sampled with bongo and hand nets from January 1993 to November 1995. Larval diets were evaluated by length-classes and capture sites, and were tested by two factor ANOVA. The larvae were feeding in all habitats, except in the flooded forests. The three species had different diets, which varied with their length and lake. The rotifers were the main initial food item of the three species, replaced by fish larvae in Brycon cephalus, cladocerans in Triportheus elongatus and detritus in Semaprochilodus insignis. The increase of the ingestion limit, as the larvae grew, was higher than the increase in the consumed prey size for the three species.

scholarly journals Sources and mechanisms of seawater freshening at the Tsivol’ki and Sedov’ bays (Novaya Zemlya): isotope (δD, δ18О) data

2019 ◽  
Vol 59 (6) ◽  
pp. 928-938
Author(s):  
E. O. Dubinina ◽  
S. A. Kossova ◽  
A. Yu. Miroshnikov
Keyword(s):  
Surface Waters ◽  
Water Exchange ◽  
Free Water ◽  
Kara Sea ◽  
River Waters ◽  
Fresh Waters ◽  
Novaya Zemlya ◽  
Deep Waters ◽  
Continental Runoff ◽  
The Difference

Three-year monitoring of isotope (D, 18О) parameters in the waters of the Sedov and Tsivolki bays (Novaya Zemlya) was carried out. The fresh waters of the bays are originated from several sources (continental runoff, precipitations, and waters going from the archipelago). The freshening extent and sources of fresh waters are different at the different depth. The D and 18О values varies only in the surface waters which contains more than 30% of fresh component. In 2015 the surface waters of Sedov bay were represented by Ob river waters, and the surface waters of Tsivolki bay were enriched by the runoff from Novaya Zemlya. Deep waters in both bays show signs of desalination by high latitude atmospheric precipitations. These waters can be transferred to the southeast coast of Novaya Zemlya through the trenches of St. Anne and Voronin. The difference in the freshening mechanisms of the waters of Sedov and Tsivolka bays is determined by different bottom morphologies and different degrees of free water exchange with the Kara Sea.

Patterns in larval reef fish distributions and assemblages, with implications for local retention in mesoscale eddies

2018 ◽  
Vol 75 (2) ◽  
pp. 180-192 ◽  
Author(s):  
K. Shulzitski ◽  
S. Sponaugle ◽  
M. Hauff ◽  
K.D. Walter ◽  
E.K. D’Alessandro ◽  
...  
Keyword(s):  
Larval Fish ◽  
Current System ◽  
Age Distribution ◽  
Mesoscale Eddies ◽  
Larval Transport ◽  
Boundary Current ◽  
Straits Of Florida ◽  
Structuring Element ◽  
Larval Distribution ◽  
Species Specific

Benthic marine populations are often replenished by a combination of larvae from local and distant sources. To promote retention of locally spawned larvae in strong, unidirectional boundary current systems, benthic marine organisms must utilize biophysical mechanisms to minimize advective loss. We examined patterns in larval fish abundance, age distribution, and assemblage in relation to environmental variables in the Straits of Florida to better understand the factors underlying larval transport and retention in a boundary current system. Depth was the primary structuring element; larval assemblages were more distinct across vertical distances of tens of metres than they were over horizontal distances of tens to hundreds of kilometres. However, depth distributions were species-specific, and larval assemblages inside and outside of mesoscale eddies were distinct. Age distributions were consistent with the hypothesis that mesoscale eddies provide opportunities for retention. Our data indicate that the effect of eddies on larval retention is likely taxon-specific and temporally variable, as synchronization of reproductive output, larval distribution, and timing of eddy passage are prerequisite to entrainment and subsequent retention of locally spawned larvae.

scholarly journals Long-term changes of ichthyoplankton communities in an Iberian estuary are driven by varying hydrodynamic conditions

2020 ◽  
Author(s):  
M Monteiro ◽  
U M Azeiteiro ◽  
F Martinho ◽  
M A Pardal ◽  
A L Primo
Keyword(s):  
Environmental Variability ◽  
Larval Fish ◽  
Fish Larvae ◽  
Climate Change Impacts ◽  
Variable Structure ◽  
Local Environment ◽  
Strong Relationship ◽  
Marine Species ◽  
Economic Implications ◽  
Species Dominance

Abstract Ichthyoplankton assemblages are key components of estuaries worldwide, playing a vital role as nurseries for fish larvae. Nonetheless, estuaries can be highly affected by ongoing climate change. Impacts of climate variability on ichthyoplankton assemblages will have consequences for marine pelagic food webs and fish populations biology, namely recruitment. This study aims to investigate the influence of environmental variability on an interannual abundance of ichthyoplankton assemblages of the Mondego estuary (Portugal). For this, an ichthyoplankton sampling programme of 13 years (2003–2015) along six distinct sampling stations was analysed to evaluate spatial, seasonal and interannual changes of ichthyoplankton distribution over periods of wet, regular and dry conditions. The ichthyoplanktonic community was dominated by Pomatoschistus spp. across all seasons and conditions, with higher larval abundances during summer and spring. Main changes were related to species seasonality and phenology as well as an increase in the number of marine species during extreme events. The larval fish community showed a strong relationship with the regional and local environment over the study, presenting a distinct yet highly variable structure during the 2009–2013 period. Reported changes will likely trigger major changes in species dominance and abundance, with clear ecological and socio-economic implications.

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