Spatial variability in nursery functions along a temperate estuarine gradient: role of detrital versus algal trophic pathways

2006 ◽  
Vol 63 (8) ◽  
pp. 1848-1864 ◽  
Author(s):  
Md. Shahidul Islam ◽  
Masaru Tanaka
Keyword(s):  
Spatial Variability ◽  
Food Web ◽  
Condition Factor ◽  
River Estuary ◽  
Sea Bass ◽  
Gut Content ◽  
Feeding Intensity ◽  
Trophic Pathways ◽  
Detrital Food Web ◽  
Copepod Biomass

We aimed to identify spatial variability in estuarine trophic pathways and to elucidate their role as a nursery for juvenile fishes along Chikugo River estuary, Japan. First, we investigated distribution of larval and juvenile fishes and their diets. Using estuarine-dependent species as a model, we analyzed diets of Japanese sea bass (Lateolabrax japonicus) and conducted copepod distribution and gut fluorescence studies. To evaluate the nursery functions of spatially variable food webs, we used several indices: copepod biomass, feeding intensity, gut content biomass, growth rates, RNA/DNA ratio, condition factor, and starvation status of sea bass larvae and juveniles. We identified four different spatial distribution patterns of fishes: oligohaline, mesohaline, euryhaline, and polyhaline. Copepod assemblages and diets of fishes were completely different among the regions. Gut chlorophyll a and phaeopigment indicated that copepods in the oligohaline region depend on a detrital food web, while in the euryhaline region they depend on an algal food web. The oligohaline region had maximum turbidity, nutrients, chlorophyll pigments, and copepod biomass, and sea bass juveniles had higher feeding intensity, gut content biomass, RNA/DNA ratio, growth rate, and condition factor and lower starvation rates. This suggests that the oligohaline region, supported by a detrital food web, is an important nursery that positively influences fish growth and condition.

scholarly journals Food Web Structure and Trophic Interactions Revealed by Stable Isotope Analysis in the Midstream of the Chishui River, a Tributary of the Yangtze River, China

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 195
Author(s):  
Qiang Qin ◽  
Fubin Zhang ◽  
Fei Liu ◽  
Chunling Wang ◽  
Huanzhang Liu
Keyword(s):  
Stable Isotope ◽  
Carbon Source ◽  
Food Web ◽  
Food Chain ◽  
Yangtze River ◽  
Trophic Niche ◽  
The Yangtze River ◽  
Food Chain Length ◽  
Trophic Pathways ◽  
Chishui River

Understanding energy flow and nutrient pathways is crucial to reveal the dynamics and functions of riverine ecosystems and develop appropriate conservation strategies. In this study, we utilized stable isotopes of δ13C and δ15N to examine the fundamental characteristics of trophic position, trophic niche, and carbon source for the food web in the midstream of the Chishui River, a tributary to the Yangtze River. Our results showed that stable isotope signatures among different sorts of basal resources and consumers were significantly distinguishable and that the food chain consisted of four trophic levels, indicating the multiple trophic pathways and long food chain length here. The trophic guilds of fish were classified into four categories, in which herbivorous and carnivorous fish showed greater trophic diversity and omnivorous fish had higher trophic redundancy, which meant that there was a stable trophic niche structure in the study area. Phytoplankton and periphyton presented the largest contributions to consumers, indicating that autochthonous productivity was the dominant carbon source in the midstream of the Chishui River. Since the Chishui River is still in a natural condition without any dam constructions, the autochthonous productivity, stable trophic niche structure, multiple trophic pathways and long food chain length found here demonstrate its high conservation value. Therefore, the strategy to refrain from damming on this river should persist into the future.

Temporal variation in the weight-size relationship of the mangrove crab Ucides cordatus L. (Decapoda: Ucididae) in relation to its life cycle phases

2014 ◽  
Vol 64 (4) ◽  
pp. 333-342 ◽  
Author(s):  
Marcos de Miranda Leão Leite ◽  
Cynthia Yuri Ogawa ◽  
Carla Ferreira Rezende ◽  
José Roberto Feitosa Silva
Keyword(s):  
Life Cycle ◽  
Condition Factor ◽  
River Estuary ◽  
Total Weight ◽  
Northeastern Brazil ◽  
Annual Life Cycle ◽  
Ucides Cordatus ◽  
Mangrove Crab ◽  
Significant Difference ◽  
The Relationship

The relationship between weight and size of individuals can be used to evaluate the status of a population, which is particularly useful for natural populations that are being exploited. Ucides cordatus occurs on the Atlantic coast of the American continent, from Florida (USA) to Santa Catarina (Brazil). This species is economically very important, most of all in the Northeastern area of Brazil, as well as in the Dominican Republic and Suriname. The objective of this study was to analyze life phases (‘fattening’, ‘matumba’, ‘milk-crab’, ‘maturation’ and ‘walking’) by use of the weight-length relationships, as well as temporal variations in this condition factor for each sex of U. cordatus. For this purpose, individuals were sampled monthly for twenty-four months at the Jaguaribe River estuary, Ceará State, Northeastern Brazil. The relationship between total weight and cephalothorax width was established using regression analysis, adjusted by a power equation. The dynamics of the condition factor were analyzed for each sex using the variation of its averages related to annual life cycle; this was done for each of the previously-mentioned phases. The relationship between total weight and cephalothorax width showed an isometric growth in males and negative allometric growth in females suggesting that, for the same reference size, males are heavier than females. When considering the average of the female condition factors, these were greater than those for males during the annual life cycle, except during the ‘maturation’ phase, which is the phase with a higher demand of energetic reserves for males. Annual variation of the condition factor in females presented no significant difference.

scholarly journals Trophic structure of a nektobenthic community exploited by a multispecific bottom trawling fishery in Northeastern Brazil

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246491
Author(s):  
Alex Souza Lira ◽  
Flávia Lucena-Frédou ◽  
Frédéric Ménard ◽  
Thierry Frédou ◽  
Júlio Guazzelli Gonzalez ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Food Web ◽  
Benthic Invertebrates ◽  
Trophic Structure ◽  
Fish Fauna ◽  
Cumulative Effects ◽  
Northeastern Brazil ◽  
Population Parameters ◽  
Bottom Trawling ◽  
Trophic Pathways

We used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (δ13C) and nitrogen (δ15N) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of δ15N (fishes: 6.49–14.94‰; sources: 2.58–6.79‰) and δ13C values (fishes: -23.86 to -13.71‰; sources: -24.32 to -13.53‰), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were determined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high δ15N values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population parameters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery.

scholarly journals Functional structure of microbial food web in the Senegal River Estuary (West Africa): impact of metazooplankton

2006 ◽  
Vol 28 (2) ◽  
pp. 195-207 ◽  
Author(s):  
Marc Bouvy ◽  
Marc Pagano ◽  
Maimouna M’Boup ◽  
Patrice Got ◽  
Marc Troussellier
Keyword(s):  
West Africa ◽  
Food Web ◽  
River Estuary ◽  
Functional Structure ◽  
Microbial Food Web ◽  
Senegal River

scholarly journals Effects of experimental warming, litter species, and presence of macroinvertebrates on litter decomposition and associated decomposers in a temperate mountain stream

2015 ◽  
Vol 72 (2) ◽  
pp. 206-216 ◽  
Author(s):  
Verónica Ferreira ◽  
Eric Chauvet ◽  
Cristina Canhoto
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Litter Decomposition ◽  
Castanea Sativa ◽  
Mountain Stream ◽  
Ambient Temperatures ◽  
C Cycle ◽  
Detrital Food Web ◽  
Water Courses ◽  
Aquatic Food

Small woodland streams make the majority of water courses in most watersheds. Litter decomposition is a key ecosystem process in these shaded streams, and its response to warming can have profound consequences for food webs and the carbon (C) cycle. However, these responses can be modulated by litter identity and the structure of the detrital food web. Here we report on a manipulative study aiming at evaluating the effects of warming (+2.8 °C), litter identity (chestnut (Castanea sativa) or oak (Quercus robur) litter), and the structure of the detrital food web (presence or absence of macroinvertebrates) on litter decomposition and decomposers in a small, temperate woodland stream. Warming significantly stimulated overall (microbial- + macroinvertebrate-driven) decomposition of oak and microbial-driven decomposition of chestnut. The similar shredder densities at elevated and ambient temperatures suggest that stimulated overall decomposition of oak resulted from increased activity of macroinvertebrate individuals. Stimulated microbial-driven decomposition of chestnut resulted from higher fungal activity with warming. Stimulation of litter decomposition by warming can lead to increases in the amount of C returned to the atmosphere and to a faster disappearance of litter from the benthos, with consequences to the C cycle and aquatic food webs.

Feeding dynamics, consumption rates and daily ration of longtail tuna (Thunnus tonggol) in Australian waters, with emphasis on the consumption of commercially important prawns

2007 ◽  
Vol 58 (4) ◽  
pp. 376 ◽  
Author(s):  
Shane P. Griffiths ◽  
Gary C. Fry ◽  
Fiona J. Manson ◽  
Richard D. Pillans
Keyword(s):  
Gonad Development ◽  
Reproductive Activity ◽  
Daily Ration ◽  
Feeding Intensity ◽  
Energy Investment ◽  
Trophic Pathways ◽  
Eastern Australia ◽  
Consumption Rates ◽  
Autumn And Winter ◽  
Longtail Tuna

The feeding ecology of longtail tuna was studied in northern and eastern Australia. Diet biomass data were used to estimate daily ration and consumption of individual prey taxa, particularly penaeids targeted by Australia’s valuable Northern Prawn Fishery (NPF). Overall, the 497 stomachs contained 101 prey taxa. In both regions, small pelagic and demersal fishes comprised the majority of the diet biomass. Fish in both regions showed a marked increase in prey diversity, variation in prey composition and stomach fullness index in autumn and winter (March–August). This increase in apparently opportunistic feeding behaviour and feeding intensity showed an inverse relationship with reproductive activity, indicating a possible energy investment for gonad development. Daily ration decreased with increasing fish size, while annual consumption by fish increased with size. Total prey consumption in the Gulf of Carpentaria was estimated at 148178 t year–1. This includes 599 t year-1 of penaeids, equivalent to 11% of the annual NPF catch. This study demonstrated that longtail tuna play an important ecological role in neritic ecosystems. Their interaction with commercial fisheries highlights the need for targeted dietary studies of high order predators to better understand trophic pathways to facilitate ecosystem-based fisheries management.

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