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.

The larval fish assemblage of the Nornalup-Walpole Estuary, a permanently open estuary on the southern coast of Western Australia

1994 ◽  
Vol 45 (7) ◽  
pp. 1193 ◽  
Author(s):  
FJ Neira ◽  
IC Potter
Keyword(s):  
Western Australia ◽  
Fish Assemblage ◽  
Larval Fish ◽  
Fish Larvae ◽  
Marine Species ◽  
Abundant Species ◽  
Entrance Channel ◽  
Southern Coast ◽  
Outer Basin

Fish larvae were sampled in the entrance channel and in the two basins of the permanently open Nornalup-Walpole Estuary, on the southern coast of Western Australia, in each month between October 1989 and September 1990. Sampling yielded a total of 39 068 larvae belonging to 36 species and 23 families, with the engraulidid Engraulis australis (56.7%) and the gobies Pseudogobius olorum (24.4%) and Favonigobius lateralis (15.0%) being the most abundant species. Most of the larvae were caught between November and March, with the concentrations of the most abundant species reaching peaks between January and March, when water temperatures had reached 21-24�C. In terms of number of larvae, the larval fish assemblage in the basins was dominated by species that spawn within the estuary, with the larvae of these species contributing ≥98.7% to the totals at the basin sites. Although the larvae of 26 marine species were caught in the entrance channel, these were either rare or absent in the basins, except for those of the terapontid Pelates sexlineatus, which were moderately abundant in the outer basin. The fact that the larvae of most of these marine species were at the preflexion stage, and that all but three of those species had never been previously recorded as either juveniles or adults within the system, indicates that they were passively transported from outside the estuary. The absence of larvae of most of the marine teleosts that are abundant in the basins of the Nornalup-Walpole Estuary parallels the situation in the nearby and seasonally closed Wilson Inlet.

Early life history studies of prey–predator interactions: quantifying the stochastic individual responses to environmental variability

2004 ◽  
Vol 61 (4) ◽  
pp. 659-671 ◽  
Author(s):  
Pierre Pepin
Keyword(s):  
Environmental Conditions ◽  
Early Life ◽  
Environmental Variability ◽  
Prey Availability ◽  
Larval Fish ◽  
Fish Larvae ◽  
Survey Methods ◽  
Field Studies ◽  
Variable Component ◽  
Field Evidence

Laboratory evidence shows that growth and survival of larval fish are strongly affected by variations in prey and predators; field evidence, in general, does not. This discrepancy may be partly due to the mismatch of scales at which manipulative and observational studies are conducted, or perhaps field studies are somehow not detecting the variable component of the larvae or their environment. I discuss potentially important variable features of fish larvae and their environment and show how mean values can be misleading. Using data from several field studies dealing with the growth and mortality of radiated shanny (Ulvaria subbifurcata) larvae, I illustrate how observational programs can miss important variation. I show evidence of how differences among individuals may lead to varying responses to fluctuations in prey availability. I also discuss issues concerning the level of variability in environmental conditions that may be described by standard survey methods used in the study of larval fish. The examples are intended to serve as illustration of the need to better describe the underlying stochastic structure of environmental conditions to understand early life dynamics.

scholarly journals Larval Fish Assemblage Structure at Coastal Fronts and the Influence of Environmental Variability

2021 ◽  
Vol 9 ◽  
Author(s):  
Paula Pattrick ◽  
Nicolas Weidberg ◽  
Wayne S. Goschen ◽  
Jennifer M. Jackson ◽  
Christopher D. McQuaid ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Environmental Variability ◽  
Larval Fish ◽  
Fish Larvae ◽  
Fish Assemblage Structure ◽  
Larval Connectivity ◽  
Coastal Species ◽  
Pelagic Eggs ◽  
Frontal Systems ◽  
Abundance And Distribution

Within the coastal zone, oceanographic features, such as fronts, can have major effects on the abundance and distribution of larval fish. We investigated the effects of fronts on larval fish assemblages by jointly collecting physical (ADCP and CTD) and biological (larvae) data in the nearshore waters of the south coast of South Africa, on four separate neap-tide occasions. Accumulation of fish larvae at predominantly internal wave-associated fronts was observed, with higher larval densities inshore of and within the front than farther offshore. On each occasion, larvae of coastal species with pelagic eggs (Mugillidae and Sparidae) were numerically dominant at the front itself, while inshore of the front, larvae of coastal species with benthic eggs (Gobiesocidae and Gobiidae) were more abundant. Offshore catches mainly comprised Engraulidae (pelagic species with pelagic eggs) larvae, which were generally restricted to the bottom, where current velocities were onshore on each occasion. On the occasion when fast (>100 cm/s) currents prevailed, however, accumulation of the larvae of coastal species occurred offshore of the front, and larvae were mixed throughout the water column. Thus, larval occurrence at these coastal frontal systems was strongly affected by the degree of mixing by currents, which on most occasions resulted in onshore retention. The results underline the importance of frontal systems in determining the nearshore distributions of fish larvae, particularly by retaining coastal fish species in the inshore region. The environmental variability observed at these frontal systems has potential implications for larval connectivity of fish populations.

Climate-associated trends and variability in ichthyoplankton phenology from the longest continuous larval fish time series on the east coast of the United States

2020 ◽  
Vol 650 ◽  
pp. 269-287
Author(s):  
WC Thaxton ◽  
JC Taylor ◽  
RG Asch
Keyword(s):  
United States ◽  
Environmental Variability ◽  
Larval Fish ◽  
Interspecific Interactions ◽  
River Estuary ◽  
Atlantic Multidecadal Oscillation ◽  
The United States ◽  
Larval Survival ◽  
Ecological Communities ◽  
Northerly Wind

As the effects of climate change become more pronounced, variation in the direction and magnitude of shifts in species occurrence in space and time may disrupt interspecific interactions in ecological communities. In this study, we examined how the fall and winter ichthyoplankton community in the Newport River Estuary located inshore of Pamlico Sound in the southeastern United States has responded to environmental variability over the last 27 yr. We relate the timing of estuarine ingress of 10 larval fish species to changes in sea surface temperature (SST), the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, wind strength and phenology, and tidal height. We also examined whether any species exhibited trends in ingress phenology over the last 3 decades. Species varied in the magnitude of their responses to all of the environmental variables studied, but most shared a common direction of change. SST and northerly wind strength had the largest impact on estuarine ingress phenology, with most species ingressing earlier during warm years and delaying ingress during years with strong northerly winds. As SST warms in the coming decades, the average date of ingress of some species (Atlantic croaker Micropogonias undulatus, summer flounder Paralichthys dentatus, pinfish Lagodon rhomboides) is projected to advance on the order of weeks to months, assuming temperatures do not exceed a threshold at which species can no longer respond through changes in phenology. These shifts in ingress could affect larval survival and growth since environmental conditions in the estuarine and pelagic nursery habitats of fishes also vary seasonally.

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.

Temporal variation of larval fish assemblages of the Murray Mouth in prolonged drought conditions

2013 ◽  
Vol 64 (10) ◽  
pp. 932 ◽  
Author(s):  
L. B. Bucater ◽  
J. P. Livore ◽  
C. J. Noell ◽  
Q. Ye
Keyword(s):  
Fish Assemblages ◽  
Larval Fish ◽  
River System ◽  
Sampling Period ◽  
Marine Species ◽  
Flow Regulation ◽  
Nursery Areas ◽  
Transition Zones ◽  
Murray Darling Basin ◽  
Drought Conditions

Estuaries are transition zones that link freshwater and marine ecosystems and are often used as nursery areas by fish. The Murray–Darling Basin, which is heavily affected by flow regulation and water extraction, is the largest river system in Australia and terminates at the Murray Mouth estuary. Protracted drought conditions resulted in extremely low flows to the Murray Mouth that affected water condition, fish abundance, community structure and fish use of the estuary (e.g. nursery areas). The aims of the present study were to examine temporal changes in larval fish assemblages in this estuary. The assemblages were dominated by two gobiid species, Arenigobius bifrenatus and Tasmanogobius lasti. There was a noticeable absence or low abundance of freshwater, diadramous and large-bodied marine species that use this estuary for reproductive functions. Monthly differences in larval fish assemblages, between August–September and October–November, were attributed to increases in the abundances of A. bifrenatus in October and November and oscillation in T. lasti during the entire sampling period. The outcomes of the present study suggested that larval fish assemblages in drought conditions are limited to small-bodied species tolerant of high salinities and that freshwater flows are needed for the estuary to function as a nursery for other species.

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.

Ocean Sprawl

2021 ◽  
Keyword(s):  
Oil And Gas ◽  
Land Reclamation ◽  
Scale Up ◽  
Local Environment ◽  
Marine Species ◽  
Theory And Practice ◽  
Artificial Structures ◽  
Energy Devices ◽  
Ship Hulls ◽  
Ocean Sprawl

Ocean sprawl is the proliferation of engineered artificial structures in coastal and offshore marine environments. These include ship hulls; infrastructure associated with land reclamation and urbanization (e.g., seawalls, bridges, floating docks); fisheries (artificial reefs, aquaculture installations); coastal defence structures (e.g., breakwaters, groynes); resource extraction (oil and gas rigs, renewable energy devices); and shipwrecks. Only fixed permanent and semipermanent structures are considered here and ship hulls are not included. Single structures can scale up with dramatic consequences for the local environment. Extreme examples of this include: the “New Great Wall” of China—seawalls enclosing coastal wetlands covering 60 percent of the total length of the Chinese coastline; “The World”, Dubai—an archipelago of over three hundred artificial islands constructed in the shape of a world map; and the “Steel Archipelago,” which describes more than four thousand oil and gas structures in the Gulf of Mexico. The placement of these fixed artificial structures modifies the local physical and chemical environment with cascading impacts on the composition, functioning, and service provision of surrounding species, habitats, and ecosystems. These structures also provide novel habitat which can offer surface for attachment, food, and protection for myriad marine species. They can act as fish aggregating devices, attracting fishing and other human activities. These structures may also have wide-reaching impacts through acting as barriers or conduits to ecological connectivity—the movement of organisms, materials, and energy between habitat units within seascapes. An improved understanding of the biological communities associated with artificial structures, coupled with the global drive for sustainable development, is driving an explosion of research into the design of multifunctional structures with built-in secondary ecological or socioeconomic benefits. Results to date have been promising but greater integration of the fields of ecology, engineering, and social sciences is necessary to better connect theory and practice in this emerging discipline.

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.

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