摘要:

The literature pertaining to the distribution, habitat, specificity, life cycles and population biology of all the species ofEubothriumis reviewed. Records in which scolex morphology is used to identify species cannot be used as this character is too variable to be of value in specific recognition. Study of the valid records suggests thatE. crassumcomprises three races. There is a freshwater race, whose preferred host is non‐migratorySalmo trutta fario, but which also infects parr, smolts and landlocked adultS. salarand parr of migratoryS. trutta trutta.Its distribution is confined to Europe and Eurasia and is co‐extensive with that ofS. trutta:it does not occur in N. America or E. Asia. It may be carried to sea in migratory salmonids, where it dies out inS. salarbut may survive inS. trutta.Its life cycle only takes place in fresh water, and requires a copepod as the only intermediate host. Other fish species may serve as paratenic or accidental hosts. The preferred host of the marine Atlantic race ofE. crassumisS. salar, butS. truttais also infected. Its distribution is co‐extensive with that ofS. salaron both sides of the Atlantic Ocean. It may be carried into fresh water by both hosts, when its numbers decline inS. salarbut not inS. trutta.The life cycle is unknown, but infection probably takes place in marine coastal waters. The preferred hosts of the marine Pacific race are all species ofOncorhynchus, with which its distribttion is co‐extensive on both sides of the Pacific Ocean. It may also be carried into fresh water, and its life cycle is also unknown.E. salvelinicomprises two races. The European freshwater race is specific toSalvelinus alpinus, and does not infectSalmospp. Its life cycle takes place in fresh water and involves only one intermediate host, a copepod. It may be carried to sea in migratory fish, and survive to return to fresh water. The American race, found throughout North America and East Asia, infects species ofSalmo, Salvelinus, Oncorhynchus, Cristivomerand other genera. Its biology is otherwise similar to that of the European race, although its return from the sea has not yet been confirmed in America. The other species ofEubothriumare more local in their distribution, some being endemic; do not comprise different races, and infect marine and anadromous fish. Nothing is known of their biology or life cycle.Eubothriumis recognised as being a marine genus that has invaded fresh water with anadromous fish. The inability to distinguish the races ofE. crassumandE. salvelinion morphological characters, their low rate of survival in the other medium and their wide distribution renders them unsuitable as biologic

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04183.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Over a fifteen month period, beginning October, 1974, approximately 13 500 centrarchids were examined for evidence of infection with metacercaria ofClinostomum marginatum.Species checked includedLepomis macrochirus, L. gulosus, L. auritus, Pomoxis nigromaculatusandMicropterus salmoides.The study site was Par Pond (South Carolina, U.S.A.), an 1120 ha reservoir receiving thermal effluent from a nuclear production reactor. Except for the largemouth bass,M. salmoides, infection percentages among the five species were less than 1%. Among bass, infection varied seasonally, being highest from January to June. From the spring highs of approximately 25 %, the percentages dropped to lows of<10% in July and August; there was a jump in September‐October to another peak of 30% and then a steady decline through December when infection percentages were again less than 10%. Neither body condition nor length of the bass were related to infection percentage or metacercaria density. Infection percentage could not be related to the influence of thermal effluent. Infection percentages did vary from location to location within the Par Pond system. A significant rank correlation could be established between infection percentage and the amount of littoral zone present in the locality from which the bass were taken. It is suggested that the local ‘bay effects’ are the result of limited home and foraging ranges of the bass in relation to the amounts of littoral zone present in various locations of the rese

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04184.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

In this study some comparative data on the growth rate and year class composition of roach in two Cheshire meres (Rostherne and Tatton) are given. The populations are characterised by year class instability and high growth rates, both of which are most extreme in Tatton Mere. The growth of roach in Tatton Mere is the highest yet recorded from Britain.The concurrence of two (1969, 1973) strong year classes in both lakes, suggests that climate is an important factor which conditions year class strength. However, although there is some correlation between year class strength and the water temperature index (>14° C) the ultimate cause of year class variability remains obscure. There is no evidence to suggest that year class failure is due to parasitic infestation byLigula intestinalisor to predation by perch upon roach fry. Year class failure may be due to the mortality of eggs related to the time of spawning. The observed difference in growth rate between the two populations may be attributed to a difference in density caused by the disparity of year class representation in Rostherne Mere and Tatton Mere. However, despite these differences, the net biomass achieved (36–39 kg ha−1) may be similar in both lakes. Superimposed on the effects of density an influence of temperature is n

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04185.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The greater part of the literature on European fishes reports the widespread occurrence of an introduced North American catfish and identifies it asIctalurus nebulosus.Study of the literature reporting critical determinations and of specimens from Europe and Great Britain reveals the presence of two species,I nebulosusandI melas.These fishes are widely used in experimental studies, usually being obtained through aquarium‐fish dealers indirectly from continental Europe. Mostly they are incorrectly identified asI nebulosus.There is reason to believe thatI melasis the more commonly imported catfish in Britain; both species occur feral in mainland Europ

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04186.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Three groups of hatchery–reared brown trout were fed for 32 weeks with synthetic diets containing 0, 18 and 100 i.u. vitamin A palmitate g−1. Vitamin A levels in the liver of the fish at the end of the experiment were 3,50 and 300 i.u. g−1respectively. The growth rate was not significantly different between any of the three groups of fish. At all times during the investigation epidermal thickness andgoblet cell concentration were similar in the three groups but there were significant changes in goblet cell concentration within each group during the experimental period. Sexually mature males in all three groups offish contained significantly fewer epidermal goblet cells than immature fish of eithe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04187.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Juvenile fathead minnows (Pimephales promelas) were stocked in tanks at different densities and different ration levels, in two experiments, to determine effects on final population density, growth and fecundity. Length and weight of fish increased with increased food availability. Egg size was exponentially related to growth and perhaps directly to ration level. High population density appeared to limit growth and gamete development regardless of food abundance. Additionally, water volume appeared to limit numbers (tolerance density) of fish which can be supported in a specific volume of water.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04188.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Grass carp were arranged in two groups with an average individual weight of 63 g and 3 g respectively. They were maintained in circular tanks and each group size was fed one of four experimental diets consisting of Purina catfish chow pellets, 50 % catfish chow ryegrass pellets, 100% ryegrass pellets and fresh duckweed,Lemna minima.In this study a high biomass, excellent growth and satisfactory survival rates were obtained when the fish were fed duckweed; the other diets were less satisfactory. The 100% ryegrass pellets gave the least weight gains and on this diet the smaller fish showed lower survival rates and more abnormalities. The feeding experiment lasted 68 days.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04189.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Observations of the nesting behaviour of the plunder fish,Harpagifer bispinis, from laboratory tanks at Palmer Station and from diving in Arthur Harbour, Anvers Island, Antarctic Peninsula, are the first to be recorded for any antarctic fish. Females of this species construct a nest and, unless removed, guard it throughout the four month incubation period. Guards clean the eggs and protect them from predators and parasites. If a guarding female is removed from a nest, another fish assumes guard responsibilities. This species exhibits traits which are common in other antarctic forms. The sequence of reproductive events affords adults, eggs and fry a high degree of protection and allows each stage to use available resources fully.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04190.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The feeding ecology of four species of fish is described in terms of associations of body form, feeding structures, and stomach contents; and of seasonal variations in diet. Black bream,Acanthopagrus berda(Forskal, 1775), and the hair‐finned goby,Ctenogobius criniger(Valenciennes, 1837), are predominantly carnivorous; milk‐spotted toadfish,Chelonodon patoca(Hamilton‐Buchanan, 1822), largely omnivorous; and bony bream,Anodontostoma chacunda(Hamilton‐Buchanan, 1822), detritivorous. The results illustrate the role of a mangrove creek in the ecology of the four species of fish and show the mangrove creek provides a nursery forA. berdaandC.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04191.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

One hundred and fifty largemouth bass(Micropterus salmoides)were caught during the mid‐winter and mid‐summer months in Par Pond, an 1120 ha cooling reservoir located on Savannah River Plant near Aiken, SC. Equal numbers of fish were taken from ambient and thermally altered (>10° C ambient) areas of the lake. The total length and weight of each bass was noted, along with the presence or absence of lesions associated with red‐sore disease (caused by the bacterium,Aeromonas hydrophilaand the ciliate,Epistylissp.). Blood was drawn, by heart puncture, from each bass and the following haematological parameters measured: haematocrit, haemoglobin, iron, total iron‐binding capacity, thyroxine, sodium and potassium. Only the total iron‐binding capacity was significantly higher in bass with red‐sore disease; none of the other blood parameters were significantly different in infected and uninfected bass. Bass from thermally altered locations had consistently higher haematocrits during both summer and winter. Bass from thermal and ambient locations were not different with respect to iron, iron‐binding capacity, sodium or potassium levels. However, bass taken during summer months had higher levels of circulating iron than individuals in winter months. Summer bass had higher thyroxine levels than bass in winter. These results are discussed in terms of their relationship to red‐sore disease, season and the impact of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb04192.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY