bluuebunny/crossref_metadata_2025_split huggingface dataset:
The population density, growth rate and production of bream, Abramis brama, in Tjeukemeer, the Netherlands
Authors: Goldspink C. R. 
Published: January 2006

A method of estimating the population density of bream in Tjeukemeer (21.3 km2) using 16 690 introduced fish (fin‐clipped and opercular tagged) is described. Gill nets of the winter fishery proved to be a more effective method of sampling the population for marked fish than fyke nets. The population density of bream (⋝25 cm) was estimated to be 180 000. There was no significant difference between the estimates derived from fin‐clipped and opercular tagged fish. The growth rate of bream in Tjeukemeer (L∞=41 cm) is poor compared with that of bream in other waters, due to its high density and the scarcity of zoobenthos available to it.The production of bream (I–XV) is estimated to be 34 kg ha−1 of which 25% is contributed by two (1959, 1963) strong year classes. Of a total biomass of 37.5 kg ha−1 available to the fishery in 1969 only 2.7 kg ha−l was removed as yield. The average P/B ratio for the population was low (0.39). It is concluded that a major flow of energy to bream is through zooplankton.
Dietary habits of fish populations in the Lower Medway Estuary
Authors: van den Broek W. L. F. 
Published: January 2006

Populations of mainly first‐year fish overwinter in the Medway Estuary, an area offering shelter and a rich and varied food supply. In the absence of previous investigations, the present study examines the dietary habits of four fish species; gadoids Merlangius merlangus and Trisopterus luscus, and pleuronectids Platichthys flesus and Pleuronectes platessa.Gadoids fed predominantly on fast moving nektonic organisms such as brown shrimps, mysids and fish while pleuronectids preferred the slower moving tubificid and polychaete worms. Seasonal fluctuations of the dietary constituents are considered in relation to changes within the populations of both prey and predator organisms.
LDH isoenzymes in the axial muscle of the sharks Galeus melastomus and Etmopterus spinax
Authors: Totland Geir K. , Kryvi Harald , Slinde Erik 
Published: January 2006

The lactate dehydrogenase isoenzyme patterns have been studied in the axial muscles of the sharks Etmopterus and Galeus. Samples from red, intermediate and white muscle fibres were run separately on a polyacrylamide slab‐gel. Both sharks have three isoenzymes; all three are present in the red and intermediate fibres, while the white fibres contain only the two slowest‐moving isoenzymes. The red fibres of both sharks contain most of the fastest‐moving isoenzyme.The isoenzymes have a high tolerance towards urea; the slow moving isoenzyme is inhibited at about 2 m urea, the next isoenzyme at 4‐6 M urea, and some activity of the fast‐moving isoenzyme is still present at 10 M urea in the incubation medium. The LDH distribution in the fibre types is studied by histochemistry on frozen sections.
Strontium marking of hatchery‐reared coho salmon (Oncorhynchm kisutch, Walbaum)
Authors: Yamada S. Behrens , Mulligan T. J. , Fairchild S. J. 
Published: January 2006

In the management of saimonid populations it is often necessary to distinguish hatchery‐reared from wild stocks. This study examines the feasability of marking fish tissue by substituting a biologically rare element, strontium, for calcium.Sixteen‐month‐old hatchery‐reared coho salmon (Oncorhynchus kisutch, Walbaum 1792) were fed a diet, to which 10000 ppm stable strontium was added, for 60 days. Prior to their seaward migration in June 1976, the treated coho contained 32 times as much strontium in their vertebrae as did the control coho.Sixty‐eight precocious males‘jacks’ returned to the hatchery in the fall of 1976 and 1200 adults in the fall of 1977. Strontium‐treated ‘jacks’ contained 1·4 times as much strontium as did control ‘jacks’ however, treated and untreated fish could not be distinguished as adults. The reduction in the strontium concentration of the treated fish could be accounted for by growth.
The occurrence and natural alleviation of stunting in a population of roach, Rutilus rutilus (L.)
Authors: Burrough R. J. , Kennedy C. R. 
Published: January 2006

Two sudden and pronounced changes in the growth rate of roach, Rutilus rutilus (L.), in Slapton Ley, Devon, have been observed between 1972 and 1976. At first the growth rate declined to the point at which the population became stunted, then subsequently it improved again. These changes were correlated with population density; the numbers of roach were increasing during the late 1960's/early 1970's, and this increase was substantially reinforced by very strong year classes in 1972, and, to a lesser extent, in 1973. The increase in population density resulting from the strong 1972 year class was apparently adequate to accelerate the onset of the stunting observed. The improvement in growth rate in 1976 followed immediately after extensive mortalities amongst the roach during 1975, caused by an epidemic of the parasite Ligula intestinal is (L.). Some improvement in the growth of O group roach had been evident during 1975, but this was not observed in the population. Ford‐Walford plots showed a decline in the value of L after the onset of stunting in 1972.Differences in the reproductive biology of the fish were found following the alleviation of stunting; the gonads of both sexes achieved a greater relative weight, and correspondingly the fecundity of the females was higher, although this latter effect became progressively less marked with increasing size. It was not apparent amongst the largest individuals. There was also some evidence of a decline in the proportion of fish maturing at minimum size. The changes in the reproductive biology were associated with the improvement in conditions for individual fish following the decline in population density.
Some studies on the hepatic microsomal enzyme activities and steroid hormone levels in carp, Cyprinm carpio exposed for six months
Authors: Sivarajah K. , Franklin C. S. , Williams W. P. 
Published: January 2006

A short‐term study from October 1975 to April 1976 was carried out by keeping 10 carp in two separate cages (five in each) at each of the three sites, namely, Wraysbury Reservoir, Ryemeads Sewage Lagoon and Deephams Sewage Lagoon (Fish unit). Fish were not artificially fed. Blood samples were collected at monthly intervals. Activities of the following hepatic microsomal enzymes, aminopyrine demethylase, p‐nitro‐reductase, UDP‐glucurony! transferase and 1‐leucyl‐p‐naphthylamide splitting enzymes were measured; cytochrome P450 and microsomal protein contents were also estimated.The levels of androgens, oestrogens and corticoid hormones were measured in the circulating blood at monthly intervals. Results indicated that there was (a) no significant increase in the activities of all the enzymes measured except for an increase in cytochrome P450 in the fish kept at Deephams Sewage treatment works, (b) no significant increase in microsomal protein content at the three sites and (c) no significant changes in the levels of plasma androgens, oestrogens and corticoids of the circulating blood.
Aspects of the biology of Sprattus sprattm (L.) in the Medway Estuary
Authors: van den Broek W. L. F. 
Published: January 2006

Fish samples were taken monthly over an eight‐hour day period between 1973 and 1975. In addition, separate night samples were collected during 1974–75. The present study considers the sprat component of the catch and examines aspects of the fish's biology and its accumulation of chlorinated hydrocarbon compounds and heavy metals.Sprats were present on every sampling date and, generally, totals were highest during late autumn/early winter. They formed 61.1 % of the catch by numbers and 17.5% by weight. Night samples contained an unexpectedly large number of sprats and with mean lengths significantly greater than those in day samples. Changes in monthly length‐frequency distributions suggested double spawning during 1974, perhaps the result of a mild winter.Sprats were infected with two copepod ectoparasites; Lernaeenicus sprattae (Sowerby) and L. encrasicola (Turton). In each case infection was low, affecting only 6.6 and 0.9% of the population respectively. Levels of chlorinated hydrocarbons and heavy metals were also low in whole sprat tissue. Values of DDDT, dieldrin and PCBs were at a maximum in winter and minimum in spring. Heavy metal results showed no seasonal pattern.
The population density, growth rate and production of roach Rutilus mtilus (L.) in Tjeukemeer, The Netherlands
Authors: Goldspink C. R. 
Published: January 2006

A method of estimating the population density of roach in Tjeukemeer (21.3 km2) using 20 529 introduced fin‐clipped fish is described. Fyke nets proved to be an effective method of sampling the population for marked fish during the spawning season. A total of 20 277 roach were processed during the recapturing period. The population density of roach (? 14 cm) was estimated to be 1 246 458. The growth rate of roach in the lake although relatively poor (von Bertalanffy's L ∞ for males and females, 22 and 26 cm respectively) for the species was similar to that recorded in three other Friesian lakes. The mortality rate of males was higher than that of females. Logarithmic length‐weight regression analyses showed that the value of the coefficient varied both within and between the sexes, that of females being higher (range 3.03–3.375) than that of males (range 2.76–3.254). Seasonal changes in the size of the coefficient were due to a disproportionate loss of gonad weight in larger fish. The fecundity of the population was comparatively high for the species.The total production of the population was estimated to be 95 hg ha−1 of which 39 kg ha−1 was contributed by fry. In older (? IV) fish the production of females (12 kg ha−1) exceeded that (2 kg ha−1) of males, due to differences in their growth and mortality rates. The relatively poor performance of roach in Tjeukemeer, in terms of biomass and production was due to a scarcity of zoobenthos and competition from other species offish. There is no evidence either from this study or the literature that the productive potential of roach in lakes is high, even though macrophytes and detritus can be consumed in significant amounts.
Vitamin C deficiency in Channa punctatus Bloch
Authors: Mahajan C. L. , Agrawal N. K. 
Published: January 2006

The results of a series of experiments on Channa punctatus previously conditioned to a complete synthetic diet and later fed vitamin C deficient diet for 210 days followed by 30 days of recovery with fortified vitamin C ration are reported. The survival, growth, morphological abnormalities and biochemical changes in tissue ascorbic acid and cholesterol levels were studied.Deficiency of vitamin C resulted in a mortality of up to 25% and retarded growth accompanied by anorexia and loss of weight. Marked skeletal abnormalities, viz., lordosis, scoliosis and degenerative changes in the thoracic vertebrae were revealed by X‐ray studies. Biochemical investigations showed a significant decrease in blood and kidney ascorbic acid levels within a month of feeding the deficient diet. A prolonged deficiency beyond 150 days resulted in a rapid rise in the cholesterol content of the liver. These biochemical changes were reversed when vitamin C was added to the ration.
Metechinorhynchus salmonis infection and diet in the river‐spawning whitefish of the Bothnian Bay
Authors: Valtonen E. T. 
Published: January 2006

A total of 206 river‐spawning whitefish Coregonus lavaretus (L.) from the Bothnian Bay was investigated for food objects and acanthocephalans in the years 1975–78. The only acanthocephalan species found was Metechinorhynchus salmonis (Müller 1780), the total number of which was 1295.The whitefish is shown to be highly susceptible to infection by M. salmonis, with as many as 88·9% of specimens infected in a sample in June 1978, although the mean intensity was only 8·9 parasites per host. The river‐spawning whitefish does not favour the intermediate host, Pontoporeia affinis, in its summer diet in the Bothnian Bay preferring to feed on eggs and molluscs, so that the incidence of M. salmonis infection decreases to 33·3% by the middle of summer. This is further reduced in the late summer by the fast associated with the migration to their upriver spawning grounds. The fact that the other acanthocephalan inhabiting the river‐spawning whitefish in the southern Gulf of Bothnia, Echinorhynchus gadi Müller, 1776 is not to be found in the Bothnian Bay population suggests that the fish captured in spring have remained in the Bothnian Bay throughout the winter.
The population dynamics of Nemipterus marginatus (Cuvier & Val.) off Western Kalimantan, South China Sea
Authors: Pauly D. , Martosubroto P. 
Published: January 2006

The following parameter values are derived for a West Kalimantan (West Borneo) stock of the threadfin bream, Nemipterus marginatus: L
∞= 24·5 cm(L.T.), W∞= 210g, K = 0·42, t= ‐0·41 andM= 1·73.Yield‐per‐recruit curves for N. marginatus are presented. Catch per hour of N. marginatus is very low, even in the area of highest density (=3·5 kg/h at 45 m depth). Single‐species exploitation of a stock of the type represented by N. marginatus appears unfeasible and the conclusion is reached that the traditional single‐species approach in fish population dynamics—such as exemplified in this paper—does not help in formulating rational exploitation schemes.
An energy budget for juvenile thick‐lipped mullet, Crenimugil labrosus (Risso)
Authors: Flowerdew M. W. , Grove D. J. 
Published: January 2006

A series of experiments were carried out to construct an energy budget for juvenile thick lipped mullet, Crenimugil labrosus Risso. A partial factorial experimental design was used to examine the effects of temperature, fish size and meal size on growth. The maximum ration that the fish were able to ingest completely per day was found to be 0·8, 1·4 and 2·3% wet body weight (b.w.) at 13,18 and 23°C, respectively. Ingested maintenance requirements (M.R.) were estimated to be 137, 205 and 288 cal fish‐1 day‐1 at 13, 18 and 23°C, respectively. At 18deg; C, M.R. varied as 25 W1.04 cal day‐1, where W= fish weight (g). Growth rate increased with increasing temperature. Maximal conversion efficiency was 21–24% and was achieved closer to the maximum ingested ration with increasing temperature.The relationship between respiration rate and W at 18deg; C for 3‐20 g fish is described by: respiration rate (ml O2 h‐1) = 0·128 W0.976The energy cost of apparent specific dynamic action at 18deg; C was found to vary between 5·1% and 23·6% of the calorific value of the ingested meal (1% wet b.w.), mean (± S.E.)=10·2 ± 2·0%.Post mortem analyses of groups of fish fed 0·2, 0·8 and 1·5% wet b.w. meals showed a significant increase in total lipid and a significant decrease in water content with increasing ratio size. A negative correlation was found between body water content and total lipid (and calories).The mean assimilation efficiency (±s.e.) for 5–10 g mullet at 18deg; C was 73·9 ± 3·6%.The observations reported in this study were brought together to construct an energy budget for juvenile C. labrosus which was found to give a reliable prediction (within 10%) of energy demand and growth under the prevailing experimental conditions. Both gross (K1) and net (K2) growth efficiencies, based on energy values, increased with increasing ratio size up to satiation and were independent of temperature. The maximum values of K1 and K2 observed were 0·33 and 0·46, respectively. The third order efficiency (K3) appeared to be independent of temperature and ration size; mean values ranged between 0·66 and 0·84.
Effects of malachite green on leucocyte abundance in rainbow trout, Salmo gairdneri (Richardson)
Authors: Hlavek R. R. , Bulkley R. V. 
Published: January 2006

Blood counts from more than 1000 young‐of‐the‐year rainbow trout, Salmo gairdneri (Richardson), were examined to determine if static exposure to malachite green at 1·35,13·5, or 21·0 mg/1 for 25–30 min or 42·0 or 72·0 mg/1 for 5 min caused chronic leucopaenia. The major changes in fish exposed for 25–30 min came during the first 24 h. After an initial lag of 3·4 h, total leucocyte‐thrombocyte counts in both treated and control fish rapidly declined. Recovery was essentially complete 1·4 days after exposure, and no leucopaenia was noted after 14 or 28 days. Thrombocytosis developed during the first 24 h in fish exposed to the higher concentrations. Lymphopaenia and neutrophilia also developed, but abated after the 4th post‐treatment day. Leucocyte numbers in control and exposed groups were virtually the same by the 14th day. The total leucocyte‐thrombocyte counts in fish exposed for 5 min declined after 24 h, but counts were not as depressed as those in fish exposed for 30 min.Because leucocyte changes similar to those in exposed fish were evident in the controls in both experiments, we believe that the leucocyte changes in rainbow trout exposed to malachite green were a result of a nonspecific vertebrate stress syndrome, rather than of specific leucocytotoxic effect of this chemical.
An analysis of the spawning behaviour of the Arctic grayling Thymallus arcticus (Pallas) with observations on mating success
Authors: Kratt L. F. , Smith R. J. F. 
Published: January 2006

In the Fond du Lac River, adult male Arctic grayling defend territories on the spawning ground for up to 7 days. Females do not defend territories and do not exhibit agonistic behaviour during the breeding season.The behaviour patterns exhibited by Arctic grayling during spawning are virtually identical to those exhibited by European grayling. The characteristic large dorsal fin of the grayling is of major importance during the spawning act.Less than 50% of all spawning attempts proceed to completion. Interference by other fish or the improper orientation of one fish may result in one member of the spawning pair moving away. Most often however, incomplete acts are the result of the female moving away for no apparent reason. Females may initially ‘test’ males or may simply not be ready to spawn when approached by males. Homosexual spawning attempts were rarely observed.
Effect of body weight and temperature on the maximum daily food consumption of Gasterosteus aculeatus L. and Phoxinus phoxinus (L.): selecting an appropriate model
Authors: Wootton R. J. , Allen J. R. M. , Cole S. J. 
Published: January 2006

The relationships between the maximum, daily food consumption, body weight and water temperature for the stickleback, Gasterosteus aculeatus L., and the minnow, Phoxinus phoxinus (L.), were studied. The two species occupy the same lakes in mid‐Wales, but differ in that G. aculeatus has a true stomach whereas P. phoxinus lacks a true stomach.For both species, the relationship between food consumption (F) and body weight (W) could be described by the model: logeF=a + b logeW. The effect of temperature (T) could be incorporated in the form: logef=a+ b, loge W+b2logeT. These models were selected because they accounted for a high proportion of the variance in the dependent variable, and because an analysis of the residuals obtained after fitting a model showed no trends which would have signalled the inadequacy of the model.
Ecological changes in a lake fishery and their effects on a stunted roach Rutilus rutilus population
Authors: Linfield R. S. J. 
Published: January 2006

Data for two sampling years (1969/70 and 1970/71) is presented to illustrate the changing composition, density and biomass of the macroinvertebrate fauna in a South Lancashire lake. Six faunal groupings are recognised for a non‐parametric analysis of the data and significance levels are given for the between‐station and between‐year differences recorded. The mean density of macroinvertebrates (1.2 mm mesh sieve) estimated for the lake as a whole increased by 28.5% in the second year (2519 m−2‐3237 m−2) whereas the estimated mean biomass in g m−2 increased by 86% wet weight (8.61−16.01) and 196% dry weight (1.74−5.15). Molluscs contributed substantially to the increased standing crop which was accompanied by increased development of macrophytes.A comparative study of the diets of roach in two size groups in winter and summer is described. The variety of food items consumed was found to be greater than in a preliminary study in May 1969 and, for the roach sampled, the average quantity of food consumed per fish increased after the 1969/70 winter. The possible relationships between invertebrate standing crop, roach diet and previously reported changes in the growth of the roach are discussed and an explanation is offered concerning the sequence of biological changes observed in the lake.
The immune response of the brown trout Salmo trutta to lipopolysaccharide
Authors: Ingram G. A. , Alexander J. B. 
Published: January 2006

Brown trout produced high molecular weight, thermostable, dithiothreitol sensitive, non‐precipitating, complement‐fixing antibodies and agglutinins to lipopolysaccharides after intramuscular injection with adjuvant. Antibodies were first detected on Day 14 and reached maximum titres after 56 to 63 days when a single injection was given. When either a second or a third injection was administered maximum titres occurred 34 to 40 days after the injection. After each injection the titres increased significantly, and the protein concentration of the sera was significantly decreased. In cellulose acetate electrophoresis experiments those bands which migrated in the β‐ to γ‐globulin regions were increased.Antibody‐secreting and antigen‐binding cells were detected on Days 8 and 4 respectively and maxima were reached between Day 16 and Day 18. The number of cells per 106 lymphoid cells was higher in the spleen than in the kidney.
A comparison of bottom trawl catch rates in the Kenya waters of Lake Victoria
Authors: Benda R. S. 
Published: January 2006

A comparison of mean trawl catch rates (kg/h) from 128 collections in 1969 and 1970 and 63 collections in the fourth quarter of 1976 showed the following changes.

A reduction in mean total catch rates at all seven depth intervals from 1970–1976.
Reductions of 6.8, 6.1, 3.9, 6.2, 1.5, 2.9 and 5.9 times from shallow to deepest 10m depths respectively.
No Tilapiu esculenfu were collected in 1976.

The trend that emerges shows a marked reduction in mean total trawl catch rates in the Kenya waters of Lake Victoria which should sound a note of caution for proponents of a mechanized fishing industry.
An examination of the fish population in the River Trent, Nottinghamshire using angler catches
Authors: Cooper M. J. , Wheatley G. A. 
Published: January 2006

During this study, anglers caught over 580 kg of fish, comprising over 29 500 individuals of 14 species. Nine times as many gudgeon, Gobio gobio, as roach, Rutilus rutilus, were caught. Gudgeon represented 35.94% of the total catch weight compared with 44.64% for roach. The mean total catch per man‐hour was 8.9 fish and the mean catch rate was 176 g per man‐hour. Population estimates for fish longer than 12 cm for all species other than gudgeon and bleak, Alburnus alburnus, gave fish densities of 0.21 fish m−2, the roach population was 0.15 m−2, and that for dace Leuciscus leuciscus, 0.02 m−2. The population density for all sizes of all species caught was estimated to be 2.25 fish m−2.The fish biomass available to the angler was 447 kg ha−2. The rate of exploitation of the fishery over the period of sampling was high at 17%, representing an annual exploitation rate of 94%.