Estuarine Ichthyoplankton Ecology in Relation to Hydrology and Zooplankton Dynamics in salt-wedge Estuary

1996 ◽  
Vol 47 (2) ◽  
pp. 99 ◽  
Author(s):  
GM Newton
Keyword(s):  
Water Temperature ◽  
Fish Larvae ◽  
River Estuary ◽  
Extended Period ◽  
Salt Wedge ◽  
Larval Stages ◽  
Black Bream ◽  
Stable Conditions ◽  
Maximum Water Temperature ◽  
High Concentrations

The ichthyoplankton assemblage of the Hopkins River estuary, Victoria, was dominated by estuarine taxa that included demersal (goby, gudgeon) and pelagic (black bream, estuary perch, anchovy) species. The two seasonal peaks in fish larvae abundance were related to (1) the spring/summer zooplankton increase that occurred after flooding of the estuary and was comprised predominantly of copepod nauplii, thereby providing a good prey field for very young fish larvae, and (2) the autumn zooplankton maxima, which would provide a wide selection of copepod stages and meroplankton and promote dietary partitioning and flexibility among older larval stages. The two peaks in fish larvae abundance occurred well before and well after the attainment of maximum water temperature in the estuary. Goby, gudgeon, estuary perch and anchovy larvae were in the plankton over an extended period coinciding with the more stable conditions of salt-wedge presence and maximum zooplankton densities. The spawning of black bream and anchovies in the estuary was clearly related to physical conditions, such as salinity and water temperature, and habitat-although spawning of both species also occurred at times of high concentrations of potential prey organisms for their larvae. Adults of all the above fish species appear to have evolved spawning strategies that are adapted to the average hydrological and biological conditions in the estuary that would lead to the enhanced survival of their larvae. With the exception of the black bream, it appears that a ubiquitous and prolonged rather than a synchronous and confined spawning strategy is more widely used by estuarine-spawning fishes in the Hopkins River estuary. This type of spawning strategy, combined with the generally high density of food available to fish larvae in estuaries, suggests that the match-mismatch hypothesis of Cushing may be less relevant in the estuarine than in the marine environment.

Spawning and early life history of a northern population of striped bass (Morone saxatilis) in the Miramichi River estuary, Gulf of St. Lawrence

1996 ◽  
Vol 74 (9) ◽  
pp. 1645-1655 ◽  
Author(s):  
Kimberly A. Robichaud-LeBlanc ◽  
Simon C. Courtenay ◽  
Andrea Locke
Keyword(s):  
Striped Bass ◽  
River Estuary ◽  
Morone Saxatilis ◽  
Early Life History ◽  
Northern Population ◽  
Salt Wedge ◽  
Larval Stages ◽  
Egg Density ◽  
History Of ◽  
St Lawrence River

Ichthyoplankton surveys between 14 May and 15 July 1992 in the tidal fresh waters of the Northwest Miramichi River, New Brunswick, provide the first description of spawning by striped bass, Morone saxatilis, in any Gulf of St. Lawrence river. Surveys showed that striped bass spawned between late May and mid-June. Most eggs were produced in a single brief peak of abundance between 31 May and 2 June at daily average surface water temperatures of 15.6–16.6 °C. Spawning occurred largely within the first 12 km of tidal fresh water above the edge of the salt wedge. Peak spawning was centred along a 2-km stretch of river directly upriver of the salt wedge. Peak densities of larval stages were found near or upstream of the area of peak egg density. Larval densities were highest near the salt wedge.

DIVERSITY OF FISH LARVAE AROUND THE ESTUARY OF THE BANYUASIN RIVER, SOUTH SUMATERA PROVINCE

2020 ◽  
Vol 6 (2) ◽  
Author(s):  
Moh. Rasyid Ridho ◽  
Enggar Patriono ◽  
Sarno Sarno ◽  
Sahira Wirda
Keyword(s):  
Initial Phase ◽  
Sampling Method ◽  
Environmental Changes ◽  
Negative Impact ◽  
Fish Larvae ◽  
River Estuary ◽  
Sampling Technique ◽  
Critical Phase ◽  
Morisita Index ◽  
Index Value

The initial phase of the fish life cycle is a critical phase associated with high mortality due to sensitivity to predators, food availability, and also environmental changes that occur in nature. Disruption of the initial stages of fish life has a negative impact on fish populations. Until now there has been no information about fish larvae around the Banyuasin River Estuary. Therefore, research is needed on the diversity of fish larvae around the Banyuasin River Estuary, South Sumatra Province. This research were used purposive sampling method, sampling technique in the form of Cruise Track Design with continuous parallel survey trajectory. Based on the results of the study found as many as 10 families consisting of 1483 individuals of fish larvae in March and 1013 individuals of fish larvae in May consisting of Engraulidae 1,601 individuals of fish larvae, Mungiloidei as many as 109 individuals, Leiognathidae 50 individuals, Chanidae 453 individuals, Scatophagidae 20 individuals , Belonidae 39 individuals, Gobioididae 5 individuals, Chandidae 183 individuals, Syngnatihidae 6 individuals, and Gobiidae 30 individuals fish larvae. The index value of fish larvae diversity is classified as medium category (March 1.02 and May 1.12), Morisita index shows the distribution pattern of fish larvae classified as a group (March 0-14.17 and May 2.43-10.40 ), and the evenness index value is in the medium category (March 0.437 and May 0.521).

Feeding behaviour of larval Ambystoma mexicanum

2011 ◽  
Vol 32 (4) ◽  
pp. 509-517 ◽  
Author(s):  
Diego de Jesus Chaparro-Herrera ◽  
S. Nandini ◽  
S.S.S. Sarma ◽  
Luis Zambrano
Keyword(s):  
Prey Species ◽  
Fish Larvae ◽  
Natural Habitat ◽  
Ambystoma Mexicanum ◽  
Larval Stages ◽  
Conservation Effort ◽  
Consistent Increase ◽  
Zooplankton Consumption ◽  
Oviparous Fish ◽  
Heterocypris Incongruens

Abstract The Axolotl, Ambystoma mexicanum, endemic to the freshwater lakes, Xochimilco and Chalco in Mexico City, feeds on zooplankton during its larval stages. We evaluated the functional response over eight weeks of A. mexicanum fed different prey items found in its natural habitat (rotifers: Brachionus havanaensis, B. calyciflorus, B. rubens and Plationus patulus; cladocerans: Moina macrocopa, Macrothrix triserialis, Alona glabra and Simocephalus vetulus; and ostracods: Heterocypris incongruens). Zooplankton consumption by A. mexicanum varied in relation to the prey species and age of the larvae. Unlike oviparous fish larvae which often feed preferentially on rotifers in the first few weeks, A. mexicanum larvae fed more on cladocerans and ostracods. Among the cladocerans offered, larval A. mexicanum consumed higher numbers of M. triserialis and M. macrocopa. Feeding on the largest cladoceran tested, S. vetulus, increased after the fifth week. There was a consistent increase in the number of ostracods Heterocypris incongruens, consumed with age, from 4 to 169 prey per larva over eight weeks. The results are discussed with relation to the importance of zooplankton diet in conservation effort of this endangered species in Lake Xochimilco.

Fickian Transport and the Dispersal of Fish Larvae in Estuaries

1982 ◽  
Vol 39 (8) ◽  
pp. 1150-1163 ◽  
Author(s):  
L. Fortier ◽  
W. C. Leggett
Keyword(s):  
Vertical Distribution ◽  
Fish Larvae ◽  
Sampling Period ◽  
Clupea Harengus ◽  
Tidal Mixing ◽  
Larval Abundance ◽  
Lawrence Estuary ◽  
Larval Stages ◽  
Diel Vertical Migrations ◽  
Average Size

We studied the regulation of ichthyoplankton dispersion in the two-layer circulation of the St. Lawrence upper estuary by determining larval abundance and vertical distribution during high frequency sampling at three stations in May, June, and July, 1979. Monthly variations in capelin (Mallotus villosus) and Atlantic herring (Clupea harengus harengus) abundance were in agreement with the seasonal trends previously reported. Capelin larvae were concentrated in the surface layer, a situation which resulted in seaward drift. No significant growth was observed over the 60-d sampling period indicating continuous recruitment to, and removal from, the sampling area. Herring larvae were concentrated in the deep layer and were carried landward. The average size of herring larvae increased from the downstream to the upstream stations. Short-term fluctuations in the abundance and vertical distribution of the two species were interpreted in terms of the Fickian representation of transport for partially mixed estuaries. The major source of variation in abundance, at a given station, was the tidal advection of horizontal gradients. Capelin larvae and herring larvae smaller than 10 mm did not actively cross the pycnocline and were not submitted to the diffusive effect of the vertical current shear. The dispersal of these larvae was apparently passive. Herring larvae larger than 10 mm performed diel vertical migrations across the pycnocline and were dispersed in the horizontal plane at a faster rate than a passive contaminant of the environment. We conclude that the Fickian approach can be profitably applied to studies of dispersal and mortality of early larval stages of fish in estuaries.Key words: ichthyoplankton, St. Lawrence estuary, dispersion, transport, vertical distribution, diel migrations, variability, abundance, tidal mixing, Fickian

scholarly journals Longitudinal Study of Total and Pathogenic Vibrio parahaemolyticus (tdh+ and/or trh+) in Two Natural Extraction Areas of Mytilus chilensis in Southern Chile

2021 ◽  
Vol 12 ◽  
Author(s):  
Cristina Bacian ◽  
Cristobal Verdugo ◽  
Katherine García ◽  
Josu Perez-Larruscain ◽  
Ignacio de Blas ◽  
...  
Keyword(s):  
Water Temperature ◽  
Vibrio Parahaemolyticus ◽  
River Estuary ◽  
Environmental Parameters ◽  
Economic Losses ◽  
Pcr Analysis ◽  
Potential Hazard ◽  
Detection Rates ◽  
Pathogenic Vibrio ◽  
Interaction Factor

Vibrio parahaemolyticus is the leading cause of seafood-associated bacterial gastroenteritis worldwide. Although different studies have focused on its pattern of variation over time, knowledge about the environmental factors driving the dynamics of this pathogen, within the Chilean territory, is still lacking. This study determined the prevalence of total and pathogenic V. parahaemolyticus strains (tdh and/or trh genes) in mussels (Mytilus chilensis) collected from two natural growing areas between 2017 and 2018, using selective agar and PCR analysis. V. parahaemolyticus was detected in 45.6% (93/204) of pooled samples from the Valdivia River Estuary. The pathogenic strains carrying the tdh and/or trh gene were detected in 11.8% (24/204): tdh in 9.8% (20/204), trh in 0.5% (1/204), and 1.5% (3/204) presented both genes. In Reloncaví Fjord, V. parahaemolyticus was detected in 14.4% (30/209) of the samples, pathogenic V. parahaemolyticus carrying the trh gene was detected in 0.5% (1/209) of the samples, while the tdh gene was not detected in the samples from this area. The total count of mauve-purple colonies typical of V. parahaemolyticus on CHROMagar was positively associated by multivariate analysis with area, water temperature, and salinity. Similarly, V. parahaemolyticus detection rates by PCR had a positive correlation with the area and water temperature. The chances of detecting total V. parahaemolyticus in the Valdivia River Estuary are significantly higher than in the Reloncaví Fjord, but inversely, during spring-summer months, the interaction factor between the area and temperature indicated that the chances of detecting V. parahaemolyticus are higher in the Reloncaví Fjord. Interestingly, this period coincides with the season when commercial and natural-growing shellfish are harvested. On the other hand, pathogenic V. parahaemolyticus tdh+ was significantly correlated with an increase of water temperature. These environmental parameters could be used to trigger a warning on potential hazard, which would influence human health and economic losses in aquaculture systems.

scholarly journals Poisoning of cattle by Senecio spp. in Brazil: a review

2018 ◽  
Vol 38 (8) ◽  
pp. 1459-1470 ◽  
Author(s):  
Welden Panziera ◽  
Saulo P. Pavarini ◽  
Luciana Sonne ◽  
Claudio S.L. Barros ◽  
David Driemeier
Keyword(s):  
Pyrrolizidine Alkaloids ◽  
Clinical Signs ◽  
Clinical Manifestations ◽  
Extended Period ◽  
Southern Brazil ◽  
Adult Cattle ◽  
Toxic Principle ◽  
Neurological Signs ◽  
Subcutaneous Edema ◽  
High Concentrations

ABSTRACT: Poisoning of cattle by plants of the Senecio genus represents an important cause of death in cattle and has important economic repercussions in southern Brazil. This review is intended to provide a detailed review of Senecio spp. intoxication in cattle and addresses issues regarding the toxic principle and pathogenesis of the disease caused by these plants and the epidemiology, clinical signs, diagnosis, control and prophylaxis of the disease. Senecio brasiliensis is the main species associated with natural intoxication of livestock in Brazil, and the number of cases associated with the ingestion of S. madagascariensis is increasing. The toxic principle of Senecio spp. comprises the hepatotoxic alkaloids of the pyrrolizidine group (pyrrolizidine alkaloids, PAs). The resulting liver lesions are chronic and irreversible and result from the inhibition of hepatocellular mitosis. Deaths of adult cattle may occur both sporadically and in larger outbreaks over an extended period of time. In cattle raising, Senecio spp. are consumed mainly during the winter, when there is a dearth of forage; at this time the poisonous Senecio species are budding and contain high concentrations of PAs. Spontaneous Senecio spp. intoxication in cattle is a chronic condition that frequently involves acute clinical manifestations. Affected cattle may present ascites, emaciation, intermittent dark diarrhea, tenesmus, rectal prolapse, and neurological signs resulting from hepatic encephalopathy. Hepatogenous photosensitization may be observed but is uncommon. Necropsy findings include dependent subcutaneous edema, ascites, and edema of the mesentery, abomasal folds, and gallbladder. The liver is firm, normal or reduced in size with a white, thick capsule. Microscopically, the hallmarks of Senecio-associated disease are varying degrees of hepatocellular megalocytosis, bile duct hyperplasia and fibrosis. Sheep are significantly more resistant to Senecio intoxication than are cattle and avidly ingest Senecio plants; therefore, the use of sheep for grazing infested pasture is recommended for preventing the associated disease in cattle.

Stratification and salt-wedge in the Seomjin river estuary under the idealized tidal influence

2017 ◽  
Vol 52 (4) ◽  
pp. 469-487 ◽  
Author(s):  
Jin Hwan Hwang ◽  
Dongmin Jang ◽  
Yong Hoon Kim
Keyword(s):  
River Estuary ◽  
Salt Wedge ◽  
Tidal Influence ◽  
Seomjin River

Creel census of amateur line fishermen in the Blackwood River estuary, Western Australia, during 1974-75

1976 ◽  
Vol 27 (4) ◽  
pp. 583 ◽  
Author(s):  
N Caputi
Keyword(s):  
Western Australia ◽  
River Estuary ◽  
Fishing Pressure ◽  
Swan Lake ◽  
Main Species ◽  
Lake Region ◽  
Black Bream ◽  
Major Species ◽  
Creel Census ◽  
Rate Of Success

A creel census was carried out from May 1974 to April 1975 on the amateur line fishermen of Blackwood River estuary, from the Swan Lakes and Deadwater to Alexandra Bridge. The estimated total fishing pressure was 76 149 fisherman hours which was mainly concentrated in the summer and autumn months. The rate of success averaged 3.86 fish per fisherman per hour fishing. The estimated harvest of fish was 287 300. In the Hardy Inlet and Swan Lake region, western sand whiting (Sillago schomburgkii) was the main species caught for most of the year, except for the autumn months when Australian herring (Arripis georgianus) was the major species. In the Blackwood River, black bream (Mylio butcheri) dominated the catch throughout the year.

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