scholarly journals Seasonal, annual and regional variations in ichthyofaunal composition in the inner Severn Estuary and inner Bristol Channel

1997 ◽  
Vol 77 (2) ◽  
pp. 507-525 ◽  
Author(s):  
I.C. Potter ◽  
P.N. Claridge ◽  
G.A. Hyndes ◽  
K.R. Clarke
Keyword(s):  
Marine Species ◽  
Life Cycles ◽  
European Eel ◽  
Freshwater Species ◽  
Marine Waters ◽  
Faunal Composition ◽  
Severn Estuary ◽  
Power Stations ◽  
Inshore Waters ◽  
Conger Eel

Monthly samples of fish from the intake screens of power stations at Oldbury and Berkeley in the inner Severn Estuary and Hinkley Point in the inner Bristol Channel, were used to analyse the community structures of the ichthyofauna in these regions. Marine species that use the estuary as a nursery area (marine estuarine-opportunists) were very abundant in the shallow inshore waters at Oldbury. Diadromous species were more abundant in the offshore and deeper waters at Berkeley than at Oldbury. Only one of the two species that complete their life cycles in the estuary was even moderately abundant in the inner estuary and the 15 freshwater species were relatively rare. Bass and particularly the sand goby complex were more numerous in the protected, inshore waters than the more offshore waters of the estuary. With the yellow and silver stages of the European eel, the reverse situation pertained. Seasonal changes in faunal composition were more pronounced in the inshore shallow than in more offshore deeper waters of the estuary. This largely reflected the sequential immigration of large numbers of the juveniles of marine estuarine-opportunist species into the former area for relatively short periods. Although the ichthyofaunal composition in the shallows at Oldbury underwent the same pattern of cyclical variation in each of five consecutive years, the degree of intra-annual variability differed, reflecting interannual differences in the recruitment strengths of the 0+ age classes of the different marine estuarine-opportunists. These cyclical changes were not correlated strongly with either salinity or water temperature. The faunal composition of the protected inshore, more marine waters of the inner Bristol Channel differed from those in both inshore and offshore regions of the inner estuary. The species which typified the fauna of the Channel were bib, poor cod, five-bearded rockling, sole and conger eel. Although the first four of these species were relatively more abundant in these waters than in the estuary, their juveniles often made extensive use of the shallows at Oldbury. This study emphasizes that, for some marine species, the protected inshore, and more marine, waters in the Bristol Channel can act as alternative nursery areas to those provided by the inshore shallows of the Severn Estuary.

Reproduction

2017 ◽  
Author(s):  
Derek Burton ◽  
Margaret Burton
Keyword(s):  
Reproductive Behaviour ◽  
Life Cycles ◽  
Freshwater Species ◽  
Adult Fish ◽  
Reproductive Patterns ◽  
Cell Divisions ◽  
Early Stages ◽  
External Cues ◽  
Neural Factors

Interspecific fish reproductive patterns, outputs and life cycles display the greatest variability within the vertebrates. Early stages of oogenesis can be repeated in adult fish, contrasting with mammals; the pre-set sequence of cell divisions in gametogenesis is otherwise similar and is described in detail. Most fish deposit much yolk (vitellogenesis) in developing eggs. Migrations, beach-spawning and mouth-brooding are some of the interesting variations. Fertilization is predominantly external but is internal in some groups such as chondrichthyans. The omission of annual reproduction is well established in some freshwater species and the idea that this may also be the case for marine teleosts is gaining acceptance. This should be taken into account for intensively fished species. The possible roles of external cues, hormones, pheromones and neural factors acting as ‘switches’ and coordinators in gametogenesis and reproductive behaviour are discussed.

The accumulation and excretion of radioactive caesium by the plaice (Pleuronectes platessa) and the thornback ray (Raia clavata)

1971 ◽  
Vol 51 (2) ◽  
pp. 411-422 ◽  
Author(s):  
D. F. Jefferies ◽  
C. J. Hewett
Keyword(s):  
Nuclear Power ◽  
Fundulus Heteroclitus ◽  
Sea Water ◽  
Marine Species ◽  
Whole Body ◽  
Turnover Rates ◽  
Power Stations ◽  
The United Kingdom ◽  
Thornback Ray ◽  
Processing Plants

INTRODUCTIONThe caesium radionuclides, caesium-137 and caesium-134, are important constituents of aqueous radioactive effluents discharged to the environment of the United Kingdom from fuel re-processing plants and nuclear power stations (Howells, 1966; Mitchell, Harvey & Smith, 1968; Harvey, Baker & Mitchell, 1969). Their accumulation by marine fishes has been the subject of several previous studies, beginning with that of Chipman (1959) who noted that caesium-137 was accumulated in the flesh of the killifish (Fundulus heteroclitus) and that accumulation continued even after a period of 72 days. Similarly, Hiyama & Shimizu (1964) showed that the muscle of the common goby (Acanthobus flaviamus) continued to accumulate caesium-134 from sea water after periods of 30 days. Baptist & Price (1962) have examined the whole body uptake of caesium, by absorption from sea water, in two marine species, the flounder (Paralichthys dentatus) and the Atlantic croaker (Micropogon undulatus), and they also investigated the accumulation, tissue distribution and excretion of caesium-137 in the croaker, the little tuna (Euthynnus alleteratus) and the bluefish (Pomatomus saltatoux), following oral administration of single doses. These authors concluded that the heart, liver and spleen of the croaker absorbed caesium-137 from sea water at a faster rate than the muscle, and that orally administered caesium-137 was rapidly absorbed from the digestive tract. Tissue distributions were similar in the croaker, bluefish and tuna. The retention of caesium-137 in croaker tissue was described as a multiple rate process. In later experiments Hiyama & Shimizu (1969) compared turnover rates in various organs and tissues following uptake from sea water and from single injection experiments, and obtained good agreement between the values from the two methods.

scholarly journals Contrasting Toxin Selectivity between the Marine Pufferfish Takifugu pardalis and the Freshwater Pufferfish Pao suvattii

Toxins ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 470 ◽  
Author(s):  
Wei Gao ◽  
Yoko Kanahara ◽  
Misako Yamada ◽  
Ryohei Tatsuno ◽  
Hiroyuki Yoshikawa ◽  
...  
Keyword(s):  
Marine Species ◽  
The Body ◽  
Freshwater Species ◽  
Oral Gavage ◽  
Paralytic Shellfish Poison ◽  
Toxin Content ◽  
Paralytic Shellfish ◽  
Strong Contrast

To clarify the differences in toxin selectivity between marine and freshwater pufferfish, we conducted experiments in artificially reared nontoxic specimens of Takifugu pardalis (marine) and Pao suvattii (freshwater) using tetrodotoxin (TTX) and paralytic shellfish poison (PSP; decarbamoylsaxitoxin (dcSTX) or saxitoxin (STX)). T. pardalis specimens were administered feed homogenate containing TTX or dcSTX (dose of toxin, 55.2 nmol/fish) and P. suvattii specimens were administered feed homogenate containing TTX + STX (dose of each toxin, 19.2 nmol/fish) by oral gavage. The toxin content in the intestine, muscle, skin, liver, and gonads was quantified after 24 and 48 or 72 h. In T. pardalis, TTX administered into the intestine was absorbed into the body and transferred and retained mainly in the skin and liver, while dcSTX was hardly retained in the body, although it partly remained in the intestine. In strong contrast, in P. suvattii, little TTX remained in the body, whereas STX was absorbed into the body and was transferred and retained in the ovary and skin. The findings revealed that TTX/PSP selectivity differs between the marine species T. pardalis and the freshwater species P. suvattii. T. pardalis, which naturally harbors TTX, selectively accumulates TTX, and P. suvattii, which naturally harbors PSP, selectively accumulates PSP.

scholarly journals Two New Hyporheic Amphipods, Bogidiella ( Bogidiella) Cyrnensis n. sp. and Bogidiella (Medigidiella?) Paolii n. sp., from Corsica

1983 ◽  
Vol 53 (1) ◽  
pp. 82-92 ◽  
Author(s):  
F. Hovenkamp ◽  
W. Hovenkamp ◽  
J.J. van der Heide
Keyword(s):  
New Species ◽  
Marine Species ◽  
Small Rivers ◽  
Amphipod Species ◽  
Freshwater Species ◽  
The Family ◽  
The Mediterranean

Two new amphipod species of the family Bogidiellidae were found in the hyporheal of two small rivers on Corsica. Both new species, Bogidiella (Bogidiella) cyrnensis n. sp. and B. paolii n. sp. (provisionally placed in the subgenus Medigidiella, but a definitive classification will have to wait till males are found), encountered at altitudes of 135 m and 750 m, respectively, show more affinities with certain freshwater species of Sardinia than with marine species of the Mediterranean.

scholarly journals Fish communities of the Wilderness Lakes System in the southern Cape, South Africa

Koedoe ◽  
2016 ◽  
Vol 58 (1) ◽  
Author(s):  
Alexis A. Olds ◽  
Nicola C. James ◽  
M. Kyle S. Smith ◽  
Olaf L.F. Weyl
Keyword(s):  
South Africa ◽  
Key Management ◽  
Mouth Opening ◽  
Marine Species ◽  
Freshwater Species ◽  
Sediment Removal ◽  
Management Actions ◽  
System A ◽  
Artificial Mouth ◽  
Estuarine Resident

The Wilderness Lakes System, a temporarily open and closed estuary with three associated lakes situated in the southern Cape region of South Africa, was sampled using a range of sampling gears to assess the fish community. A total of 25 species were sampled throughout the system, with the highest diversity in the Touw Estuary (23 species) and the lowest in Langvlei (11 species). Estuary-associated marine species (13 species) dominated species richness with smaller proportions of estuarine resident (7 species), freshwater (3 species) and catadromous species (2 species). Estuarine resident species dominated the catch numerically. The size–class distribution of euryhaline marine species indicated that upon entering the Touw Estuary as juveniles, the fish move up the system towards Rondevlei where they appear to remain. Three freshwater species were recorded in the system, all of which are alien to the Wilderness Lakes System. Decreasing salinity in the upper lakes appears to be a driving factor in the distribution and increasing abundance of the freshwater fishes. Sampling followed a drought, with the system experiencing substantially increased levels of mouth closure compared to a similar study conducted in the 1980s. The timing of mouth opening and the degree of connectivity between the lakes influence the nursery function of the system as a whole. Management actions need to focus on improving ecological functioning of this system, in particular how mouth opening is managed, to facilitate nursery function and limit the establishment of invasive species.Conservation implications: Key management actions are required to improve fish recruitment potential into and within the system. These include maintenance of adequate marine inflow through adherence to artificial mouth breaching protocols and improving connectivity between the lakes through sediment removal from localised deposition points within the connecting channels.

scholarly journals Age composition, growth, movements, meristics and parasites of the whiting, Merlangius merlangus, in the Severn Estuary and Bristol Channel

1988 ◽  
Vol 68 (2) ◽  
pp. 295-313 ◽  
Author(s):  
I. C. Potter ◽  
D. C. Gardner ◽  
P. N. Claridge
Keyword(s):  
Irish Sea ◽  
Age Composition ◽  
Severn Estuary ◽  
Main Site ◽  
The North ◽  
The North Sea ◽  
Inshore Waters ◽  
Merlangius Merlangus ◽  
The Irish Sea ◽  
Copepod Parasites

Samples collected from power station intake screens between 1972 and 1977 have been used to study aspects of the biology of the whiting in the Severn Estuary and Bristol Channel. 0+ whiting generally started appearing in the inner estuary in July, at which time their standard length was at least 38 mm. Their numbers peaked in October and subsequently declined particularly rapidly during the wet winter of 1976/7 when salinities were frequently below 10‰. The size of 0+ whiting in the late autumn and early winter was generally less in the shallows of the Inner Severn Estuary than in neighbouring deeper waters and in the Inner Bristol Channel. Growth rates of 0 + whiting fell within the range of those recorded for the North Sea, but below those generally found in inshore waters and sea lochs on the west coast of Scotland. Following their immigration into inshore waters in the Bristol Channel and Inner Severn Estuary, young whiting became infected with the copepod parasites Lernaeocera branchialis and Clavella adunca and the metacercariae of the heterophyid digenean Cryptocotyle lingua. Prevalence of infection was less in 0+ than older fish and infection by L. branchialis caused a significant decline in condition. As whiting became larger, the main site of attachment of Clavella adunca changed gradually from the wall of the branchial chamber to the primary rakers of the first gill arch. Vertebral counts suggest that the whiting which enter the Inner Bristol Channel and Severn Estuary are not representatives of the populations found in the Irish Sea.

scholarly journals Spatial scales of interannual recruitment variations of marine, anadromous, and freshwater fish

1997 ◽  
Vol 54 (6) ◽  
pp. 1400-1407 ◽  
Author(s):  
R A Myers ◽  
G Mertz ◽  
J Bridson
Keyword(s):  
Spatial Scale ◽  
Freshwater Fish ◽  
Marine Environment ◽  
Environmental Variables ◽  
Large Scale ◽  
Spatial Scales ◽  
Marine Species ◽  
Freshwater Species ◽  
Environmental Agents

We examine the spatial scale of variability in recruitment for 11 marine, three anadromous, and five freshwater species. Generally the spatial scale of recruitment correlations for marine species is approximately 500 km, compared with less than 50 km for freshwater; anadromous species fall between these two scales. The scale for marine species is comparable with (but less than) that of the largest-scale environmental variables (and is compatible with the idea that large-scale environmental agents influence recruitment). Our results are consistent with the hypothesis that predation is a more important factor in determining recruitment in freshwater than it is in the marine environment.

Age determination and growth estimates of the white-spotted conger eel, Conger myriaster (Brevoort, 1856) in marine waters of South Korea

2017 ◽  
Vol 34 (3) ◽  
pp. 542-549 ◽  
Author(s):  
J. H. Bae ◽  
H. J. Bae ◽  
H.-M. Park ◽  
H.-S. Park ◽  
H.-G. Kim ◽  
...  
Keyword(s):  
South Korea ◽  
Age Determination ◽  
Marine Waters ◽  
Conger Myriaster ◽  
Conger Eel

Endocrine disruption in marine fish

2003 ◽  
Vol 75 (11-12) ◽  
pp. 2249-2261 ◽  
Author(s):  
P. Matthiessen
Keyword(s):  
Freshwater Fish ◽  
Endocrine Disruption ◽  
Marine Fish ◽  
Marine Environment ◽  
Population Level ◽  
Marine Species ◽  
Future Research ◽  
Freshwater Species ◽  
Top Predators

This topic reviews the whole field of endocrine disruption (ED) in marine fish and compares this with our knowledge of the situation in freshwater species. In broad terms, similar types of ED have been observed in the two groups, although effects in the marine environment tend to be less marked, presumably due to dispersion and dilution. There are, however, some data which suggest that marine fish that are top-predators can experience ED due to biomagnification of organochlorines. Processes such as smoltification, metamorphosis, and hermaphroditism, which are common in some marine species, may be particularly susceptible to ED, but have as yet been scarcely studied. As with freshwater fish, firm links to population-level effects have not yet been demonstrated, although it is not unreasonable to suppose that they are occurring in some locations. The topic concludes with some recommendations for future research.

Fossil species of the diatom genus Tetracyclus (Bacillariophyta, ‘ellipticus’ species group): morphology, interrelationships and the relevance of ontogeny

1996 ◽  
Vol 351 (1348) ◽  
pp. 1759-1782 ◽  
Keyword(s):  
Species Group ◽  
Life Cycles ◽  
Freshwater Species ◽  
Fossil Species ◽  
Variable Property ◽  
Elliptical Shape ◽  
Diatom Genus ◽  
Diatom Valve

The diatom genus Tetracyclus Ralfs (Bacillariophyta) is composed largely of extinct, freshwater species many of which have been used as stratigraphic markers across several continents under the assumption that they are relatively widespread and confined to precise geological epochs. Until recently the taxonomy of the genus relied almost exclusively on the shape and dimensions of the preserved siliceous valves. This study forms part of a revision of the entire genus. In this paper the morphology of fossils from the ‘ellipticus’ species group is discussed. Significant to this study is the relative usefulness of diatom valve dimensions and overall shape, seen here in the context of siliceous morphogenesis and the appearance of particular valve ‘shapes’ at particular stages in their life cycles. In addition, alternative ways of representing character data have been applied to establish whether the ‘ellipticus’ species group is monophyletic with respect to the genus. Results suggest that the ‘ellipticus’ species group is not monophyletic and that the elliptical shape of valves is better viewed as a variable property of ontogeny.

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