Ontogenetic dietary shifts of fishes in an Australian floodplain river

2005 ◽  
Vol 56 (2) ◽  
pp. 215 ◽  
Author(s):  
A. J. King
Keyword(s):  
Early Life ◽  
Native Species ◽  
Fish Larvae ◽  
Rapid Development ◽  
Food Resources ◽  
Ecological Niches ◽  
Floodplain River ◽  
First Feeding ◽  
Dietary Shifts ◽  
Australian Freshwater

The early life of fishes is marked by rapid development when individuals are thought to optimise their success through ontogeny by altering ecological niches and resources. Since most fish larvae are thought to require small prey items at first feeding, competition for potentially limiting food resources may occur between species creating a juvenile bottleneck, which may, in turn, influence future recruitment strength. The diets of the early life stages of most Australian freshwater fish are poorly known. The present study investigated the ontogenetic dietary patterns of six species of fish in an Australian floodplain river. A large proportion of first-feeding larvae of three species (Murray cod, Australian smelt and carp) were able to feed externally while still retaining their yolk sac. All species demonstrated major dietary shifts from newly hatched larvae through development into juvenile stages and adulthood. Only a few minor overlaps in diet were found, with greater overlaps commonly occurring between sequential stages of the same species, reflecting subtle ontogenetic changes. Despite two co-occurrences of an introduced and a native species using the same rearing habitat as larvae, dietary preferences did not significantly overlap, suggesting that a recruitment bottleneck caused by competition for food resources is unlikely for these species.

Early life bacterial succession under different diet regime Atlantic salmon (Salmo salar L.)

2020 ◽  
Author(s):  
Eleni Nikouli ◽  
Konstantinos Kormas ◽  
Yang Jin ◽  
Yngvar Olsen ◽  
Ingrid Bakke ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Fish Oil ◽  
Early Life ◽  
Life Stages ◽  
Early Life Stages ◽  
Bacterial Phyla ◽  
Lipid Source ◽  
First Feeding ◽  
Bacterial Succession ◽  
Dietary Treatments

Abstract Backgound: The present study investigated the effect of different lipid source in the feed on the colonization and the bacterial succession in early life stages (fertilized eggs until 93 days post first feeding) of S. salar. The two diets used in this study, FD (fish oil based diet) and VD (vegetable oil based diet), were formulated to cover the fish nutritional requirements and except the lipid source the components were identical between them.Hindgut samples collected at 0, 35, 65 and 93 days post first feeding (dpff). Moreover, fertilized eggs, yolk sac larvae, rearing water and feed were also sampled in order to assess a possible contribution of their microbiota to the colonization of the gut. To analyze the composition of the bacterial communities, the Illumina MiSeq platform was used. Results: S. salar growth variables (mean wet weight and total length) did not differ significantly during the experiment (p> 0.05) across replicate tanks and between dietary treatments. The analysis of the 16S rDNA sequencing data revealed a total of 4548 unique OTUs, affiliated in 21 bacterial phyla. Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were the dominant bacterial phyla. 13 OTUs were shared among all S. salar samples independent of life stage and diet treatment. Similarity percentages analysis (SIMPER) based on Bray–Curtis distance, showed that the average dissimilarity among the groups of the same life stages was 76.0%, whereas the average dissimilarity within groups of the same dietary treatment was 78.5% (FD) and 83.6% (VD). Conclusion: Feeding on either fish oil or vegetable oil-based diets, did not result in significant differences in the intestinal microbiota. The composition of gut microbiota did not differ significantly between the two dietary treatments, but changed with age, and each stage was characterized by different dominant bacteria. These OTUs are related to species that provide different functions and have been isolated from a variety of environments. Finally, this study revealed the occurrence of a core microbiota independent of the studied life stages and diet during the early life stages of Atlantic salmon.

Early Life History of Fishes in the San Francisco Estuary and Watershed

2004 ◽  
Keyword(s):  
San Francisco ◽  
Early Life ◽  
Fish Larvae ◽  
Accurate Determination ◽  
Early Life History ◽  
San Francisco Estuary ◽  
Larval Transport ◽  
Water Diversion ◽  
Factors Affecting ◽  
Particle Release

<em>Abstract.</em>—We used a coupled hydrodynamic-particle tracking model to assess the relative importance of factors affecting transport and entrainment risk for generalized fish larvae in Suisun Marsh in the San Francisco Estuary, California. Factors examined included location of particle release, time of particle release, vertical migration behavior, and combinations thereof. Model sensitivity was evaluated by observing particle entrainment into a water diversion in Suisun Marsh under various scenarios and compared to randomized input cases. Scenarios combining two or more factors indicated nonlinear interactions, including evidence of tidal pumping on neap tides near our test diversion. Our study suggests that accurate modeling of larval transport depends on accurate determination of fish locations, tidal and residual time scale circulation simulation, and fish behavior during early life stages. We also examined appropriate approaches to modeling these factors.

scholarly journals Negative Effects of Diurnal Changes in Acidification and Hypoxia on Early-Life Stage Estuarine Fishes

Diversity ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 25 ◽  
Author(s):  
Brooke K. Morrell ◽  
Christopher J. Gobler
Keyword(s):  
Early Life ◽  
Fish Larvae ◽  
Life Stage ◽  
Early Life Stage ◽  
Low Ph ◽  
Sensitivity Threshold ◽  
Diurnal Changes ◽  
Menidia Menidia ◽  
Negative Effects ◽  
Low Do

Estuaries serve as important nursery habitats for various species of early-life stage fish, but can experience cooccurring acidification and hypoxia that can vary diurnally in intensity. This study examines the effects of acidification (pH 7.2–7.4) and hypoxia (dissolved oxygen (DO) ~ 2–4 mg L−1) as individual and combined stressors on four fitness metrics for three species of forage fish endemic to the U.S. East Coast: Menidia menidia, Menidia beryllina, and Cyprinodon variegatus. Additionally, the impacts of various durations of exposure to these two stressors was also assessed to explore the sensitivity threshold for larval fishes under environmentally-representative conditions. C. variegatus was resistant to chronic low pH, while M. menidia and M. beryllina experienced significantly reduced survival and hatch time, respectively. Exposure to hypoxia resulted in reduced hatch success of both Menidia species, as well as diminished survival of M. beryllina larvae. Diurnal exposure to low pH and low DO for 4 or 8 h did not alter survival of M. beryllina, although 8 or 12 h of daily exposure through the 10 days posthatch significantly depressed larval size. In contrast, M. menidia experienced significant declines in survival for all intervals of diel cycling hypoxia and acidification (4–12 h). Exposure to 12-h diurnal hypoxia generally elicited negative effects equal to, or of greater severity, than chronic exposure to low DO at the same levels despite significantly higher mean DO exposure concentrations. This evidences a substantial biological cost to adapting to changing DO levels, and implicates diurnal cycling of DO as a significant threat to fish larvae in estuaries. Larval responses to hypoxia, and to a lesser extent acidification, in this study on both continuous and diurnal timescales indicate that estuarine conditions throughout the spawning and postspawn periods could adversely affect stocks of these fish, with diverse implications for the remainder of the food web.

scholarly journals Obituary notices of fellows deceased

1907 ◽  
Vol 78 (526) ◽  
Keyword(s):  
Organic Chemistry ◽  
Special Interest ◽  
Early Life ◽  
Western Europe ◽  
Rapid Development ◽  
Freedom Of Speech ◽  
Early Age ◽  
The University ◽  
German Universities ◽  
Master Builders

There are few branches of science so indelibly associated with the second half of the last century as that highly-specialised study of the compounds of carbon, which is commonly called organic chemistry. The marvellously rapid development of this branch of chemistry will ever remain one of the greatest monuments to the enthusiasm and industry of scientific workers. Amongst the master-builders of this imposing edifice, one of the most conspicuous was Johannes Wislicenus, who, over a period of more than forty years, devoted his great natural gifts and extraordinary energy to this work of construction. Although in 1853, at the early age of 18, we already find Wislicenus acting as assistant to Heintz, then Professor of Chemistry in the University of Halle, his further progress to academic distinction did not proceed on the stereotyped lines usually followed by those who succeed in gaining access to the select professional caste of the German universities. Wislicenus’ early life is, in fact, of special interest, taking us back as it does to a time when liberty and freedom of speech were ideals for which serious sacrifices had to be made even in the countries of Western Europe.

Population decline off the Japanese sardine Sardinops melanostictus owing to recruitment failures

1995 ◽  
Vol 52 (8) ◽  
pp. 1609-1616 ◽  
Author(s):  
Yoshiro Watanabe ◽  
Hiromu Zenitani ◽  
Ryo Kimura
Keyword(s):  
Early Life ◽  
Egg Production ◽  
Population Decline ◽  
Larval Abundance ◽  
Life Stages ◽  
Population Fluctuations ◽  
Early Life Stages ◽  
Japanese Sardine ◽  
First Feeding ◽  
Poor Recruitment

The Japanese sardine Sardinops melanostictus started to decline after 1989. Recruitment to age 1 population was small in four year-classes from 1988 to 1991. The population decline after 1989 resulted from recruitment failures in 4 consecutive years. Egg production was high in the years of poor recruitment. The recruitment failures were caused not by a reduction in reproductive output but by low survival between egg stage and age 1 recruitment. Abundance of post first-feeding larvae positively correlated with egg and yolksac larval abundance. Mortality at the first-feeding stage was not so variable as to destroy correlations between the abundance of early life stages. The population of age 1 recruits did not correlate with the abundance of post first-feeding larvae. Recruitment of the sardine was not fixed by the end of the first-feeding stage. Cumulative mortality through the early life stages, rather than relatively instantaneous mortality at the first-feeding stage, is thought to be responsible for the recruitment success or failure and eventual population fluctuations of the sardine.

Improving reliability in environmental DNA detection surveys through enhanced quality control

2017 ◽  
Vol 68 (2) ◽  
pp. 388 ◽  
Author(s):  
Elise M. Furlan ◽  
Dianne Gleeson
Keyword(s):  
Quality Control ◽  
Native Species ◽  
Conservation Management ◽  
Environmental Dna ◽  
Positive Control ◽  
False Negatives ◽  
Method Error ◽  
Target Dna ◽  
Species Specific ◽  
Australian Freshwater

Species-specific environmental DNA (eDNA) surveys are increasingly being used to infer species presence in an environment. Current inadequacies in quality control increase concern for false negatives, which can have serious ramifications for both the management of invasive species and the conservation of native species. eDNA surveys involve a multi-step process to sample, capture, extract and amplify target DNA from the environment. We outline various positive control options and show that many of the commonly used controls are capable of detecting false negatives arising during the amplification stage only. We suggest a secondary, generic primer, designed to co-amplify endogenous DNA sampled during species-specific eDNA surveys, constitutes a superior positive control to monitor method success throughout all stages of eDNA analysis. We develop a species-specific European carp (Cyprinus carpio) assay and a generic fish assay for use as an endogenous control for eDNA surveys in Australian freshwater systems where fish are known to be abundant. We use these assays in a multiplex on eDNA samples that are simultaneously sampled, captured, extracted and amplified. This positive control allows us to distinguish method error from informative non-amplification results, improving reliability in eDNA surveys, which will ultimately lead to better informed conservation management decisions.

Development of digestive organs and feeding ability in larvae of Japanese eel (Anguilla japonica)

1995 ◽  
Vol 52 (5) ◽  
pp. 1030-1036 ◽  
Author(s):  
Tadahide Kurokawa ◽  
Hirohiko Kagawa ◽  
Hiromi Ohta ◽  
Hideki Tanaka ◽  
Koichi Okuzawa ◽  
...  
Keyword(s):  
Digestive Tract ◽  
Early Life ◽  
Digestive Enzymes ◽  
Developmental Process ◽  
Posterior Part ◽  
Mouth Opening ◽  
Anguilla Japonica ◽  
Japanese Eel ◽  
Digestive Organs ◽  
First Feeding

As part of a study on the early life of Japanese eel, the development of the digestive organs was observed during the 13 d after hatching. The digestive tract was formed only at the pharynx at hatching; the posterior part of the duct differentiated during 1 d posthatch (DPH). Pancreas and liver started to develop at 3 DPH. Immunohistochemistry using an antibody to eel trypsinogen showed weak signals first appearing in the pancreas at 6 DPH, suggesting that the eel pancreas starts to synthesize digestive enzymes at 6 DPH. The immunohistochemical signals became strong at 7 DPH, at which time the mouth opening orientation moved from ventral to anterior, the intestine differentiated into small intestine and rectum and the yolk was absorbed. Rotifers were first observed in the digestive tract of 13-d-old larvae. We inferred from the developmental process of the digestive organs that the larvae can start feeding at 7 DPH, which is earlier than observations of first feeding.

scholarly journals Fish larvae and recruitment patterns in floodplain lagoons of the Australian Wet Tropics

2017 ◽  
Vol 68 (5) ◽  
pp. 964 ◽  
Author(s):  
Paul C. Godfrey ◽  
Angela H. Arthington ◽  
Richard G. Pearson ◽  
Fazlul Karim ◽  
Jim Wallace
Keyword(s):  
Native Species ◽  
Fish Larvae ◽  
Early Life History ◽  
Ecological Condition ◽  
Life History Stages ◽  
Saline Habitats ◽  
Wet Tropics ◽  
Recruitment Patterns ◽  
Threatened Habitats ◽  
Flood Dynamics

Floodplain lagoons in the Queensland Wet Tropics bioregion, Australia, are important and threatened habitats for fish. As part of studies to assess their ecological condition and functions, we examined patterns of occurrence of fish larvae, juveniles and adults in 10 permanent lagoons on the Tully–Murray floodplain. Lagoons contained early life-history stages of 15 of the 21 native species present, including 11 species that complete their life cycle in fresh waters and 4 that require access to saline habitats for larval development. Lagoon connectivity to the rivers, distance from the coast and flood dynamics influenced temporal variation in fish abundance, population size structures and recruitment patterns. This study and the literature show that wet, post-wet and dry-season habitats are utilised by small opportunists (e.g. Melanotaenia splendida), an equilibrium species (Glossamia aprion) and larger periodic strategists (neosilurid catfishes). Maintenance of natural seasonal patterns of flow and connectivity, and active protection of permanent floodplain lagoons from riparian and land-use disturbance, will be essential if their roles in fish recruitment are to be sustained.

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