A Study of Six Winter Seasons of Commercial Fishing on Lake Winnipeg, 1950–1955

1959 ◽  
Vol 16 (1) ◽  
pp. 131-145 ◽  
Author(s):  
L. C. Hewson
Keyword(s):  
Dissolved Oxygen ◽  
Age Groups ◽  
Annual Production ◽  
Average Weight ◽  
Commercial Fishing ◽  
Apparent Effect ◽  
Lake Winnipeg ◽  
Stizostedion Canadense ◽  
Average Size

Investigations of a Lake Winnipeg winter fishery for sauger, Stizostedion canadense, and yellow walleye, S. vitreum vitreum, during January and February each year revealed some significant changes in average size for two species as the season progressed, and from year to year. Average weight based on 50 to 1600 fish approximated 0.5 lb for sauger and 0.7 for walleye in most areas. Fishing success declined during the study period. A sample of the sauger catch revealed mainly age-groups III, IV and V. Fish catches appeared unrelated to either water temperatures or dissolved oxygen. Increased use of nylon nets had no apparent effect on annual production.

A Seven-year Study of the Fishery for Lake Whitefish, Coregonus clupeaformis, on Lake Winnipeg

1959 ◽  
Vol 16 (1) ◽  
pp. 107-120 ◽  
Author(s):  
L. C. Hewson
Keyword(s):  
Age Groups ◽  
Water Masses ◽  
Fishing Ground ◽  
Fishing Gear ◽  
Coregonus Clupeaformis ◽  
Inshore Water ◽  
Lake Winnipeg ◽  
Scale Reading ◽  
Temperature Changes ◽  
Average Size

A representative section of the Lake Winnipeg whitefish fishery was studied during seven summers. The average size of whitefish in samples numbering from 100 to 3,500 fish yearly varied with time and place, but trends were absent. Ages of whitefish in commercial catches, determined by scale reading, revealed three main age groups each year during six summers. Fishing success varied during 7 years and showed no indication of a trend toward better or worse fishing. Some parts of the fishing ground are but lightly exploited. Temperature changes in inshore water masses affected catches in some fishing gear.

scholarly journals Callus Age and Size of Barley (Hordeum vulgare L.) Improves Regeneration Efficiency

2015 ◽  
Vol 7 (2) ◽  
pp. 188-191 ◽  
Author(s):  
Mozidul HAQUE ◽  
SM Shahinul ISLAM
Keyword(s):  
Hordeum Vulgare ◽  
Age Groups ◽  
Average Weight ◽  
Ms Medium ◽  
Fresh Weight ◽  
Regeneration Medium ◽  
Immature Seeds ◽  
Regeneration Efficiency ◽  
Semi Solid ◽  
Callus Size

In order to improve regeneration efficiency embryos derived from immature seeds of BARI barley-6 were taken for this study. In this case callus size, age and its fresh weight were considered. Embryos sizes were classified into four groups: 0.6-1.0 mm (A), 1.1-1.5 mm (B), 1.6-2.0 mm (C) and 2.1-2.5 mm (D), and cultured to semi-solid MS medium for callus induction. Five weeks old calli were transferred to MS medium that contained 1.0 mg/l BAP + 150 mg/l L-glutamine, for regeneration. Results indicated that 1.6-2.0 mm size of embryos produced the highest callusing (56.72%) and green plantlets (42.16%), while small sized (0.6-1.0 mm) showed very poor (2.75%) callusing and no regeneration occurred. Calli were divided into three age groups e.g. early (1-3 weeks), medium (4-6 weeks) and prolonged age (7-12 weeks) and cultured to regeneration medium. To observe the effect of calli weight on regeneration, they were grouped into four categories: I (50-100 mg), II (101-150 mg), III (151-200 mg) and IV (>201 mg). The highest regeneration and rooting were recorded when the age of callus was 4-6 weeks and its weight range was 151–200 mg (III). The lowest regeneration and rooting were found when 1-3 weeks old calli were used and its average weight was 50-100 mg (I).

Production and Population Dynamics of the Crayfish Orconectes virilis in Three Michigan Lakes

1977 ◽  
Vol 34 (11) ◽  
pp. 2030-2040 ◽  
Author(s):  
Walter T. Momot ◽  
Howard Gowing
Keyword(s):  
Population Dynamics ◽  
Growth Rates ◽  
Age Groups ◽  
Mortality Rates ◽  
Reproductive Age ◽  
Annual Production ◽  
Effective Density ◽  
Orconectes Virilis ◽  
Brood Stock ◽  
Density Dependent

Fluctuations in mortality rather than in growth rates produced most of the year-to-year differences in biomass accumulation of three different populations of the crayfish Orconectes virilis. Yearly biomass changes resulted from density-dependent control of mortality and fecundity during certain portions of the life cycle. Density-dependent changes in mortality rates controlled population size for adults in all lakes and for young-of-the-year in two of the three study lakes. Growth rates were much less responsive to fluctuating densities. Disparity between the number of ovarian and attached eggs increased as density of age I+ crayfish increased. This provided a strong density regulator on fecundity. Differences occurred in the number of recruits produced by a brood stock that survive to the end of the first growing season in the various lakes. Yet the number of females surviving to reproductive age 2 yr later was strongly regulated. Strong population regulation produced two female recruits of breeding age for every two–six parental breeding females. The high biomass and production levels of crayfish discovered in West Lost Lake in 1962–63 also occurred in the other area lakes. Higher but variable levels of recruitment resulted in larger standing crops and production in West Lost lake. This resulted from less effective density controls on the mortality rates of younger age-groups in that lake. Despite great variation in biomass of from 46 to 213 kg/ha and annual production from 60 to 142 kg/ha, the annual turnover ratio of the biomass was found to vary only between 0.94 and 1.53. Key words: crayfish, Orconectes virilis, population dynamics, annual production, Michigan lakes

The weight of the thyroid and pituitary glands and its relationship with rate of gain in beef steers

1962 ◽  
Vol 58 (3) ◽  
pp. 291-294 ◽  
Author(s):  
H. C. Luitingh
Keyword(s):  
Thyroid Gland ◽  
Pituitary Gland ◽  
Age Groups ◽  
Relative Weight ◽  
Live Weight ◽  
Average Weight ◽  
Beef Steers ◽  
Absolute Weight ◽  
Thyroid Glands ◽  
Pituitary Glands

The daily live-weight gain of beef steers was not correlated with the weight of the pituitary gland. In the case of the thyroid gland a significant correlation was found between the absolute weight of the gland and the rate of gain. No correlation, however, was found between the relative weight of the thyroid gland and the rate of gain of the steers.A highly significant correlation was found between the weight of both the pituitary and thyroid glands and the live weight of the steers (r = 0·44 and r = 0·55 respectively), and the slope of the regression lines showed that the weight of the pituitary gland varied with the power of 0·34 of live weight (0·34% increase in the weight of the pituitary for every 1% increase in live weight) whilst the weight of the thyroid gland varied with the power of 0·89 of the live weight.No correlation was found between the weight of the pituitary and thyroid glands. The average weight of the pituitary was 1·89, 2·11 and 2·19 g. and the average weight of the thyroid was 16·81, 20·24 and 22·65 g. for steers of 14, 26 and 38 months respectively. The average live weights of the steers in the age groups concerned were 791, 893 and 1071 lb. respectively.

Dynamic hypoxic zones in Lake Erie compress fish habitat, altering vulnerability to fishing gears

2015 ◽  
Vol 72 (6) ◽  
pp. 797-806 ◽  
Author(s):  
Richard T. Kraus ◽  
Carey T. Knight ◽  
Troy M. Farmer ◽  
Ann Marie Gorman ◽  
Paris D. Collingsworth ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Lake Erie ◽  
Scale Effects ◽  
Stock Assessment ◽  
Fish Habitat ◽  
Fish Distribution ◽  
Commercial Fishing ◽  
Hypoxic Conditions ◽  
Fishing Gears ◽  
Catch Rates

Seasonal degradation of aquatic habitats from hypoxia occurs in numerous freshwater and coastal marine systems and can result in direct mortality or displacement of fish. Yet, fishery landings from these systems are frequently unresponsive to changes in the severity and extent of hypoxia, and population-scale effects have been difficult to measure except in extreme hypoxic conditions with hypoxia-sensitive species. We investigated fine-scale temporal and spatial variability in dissolved oxygen in Lake Erie as it related to fish distribution and catch efficiencies of both active (bottom trawls) and passive (trap nets) fishing gears. Temperature and dissolved oxygen loggers placed near the edge of the hypolimnion exhibited much higher than expected variability. Hypoxic episodes of variable durations were frequently punctuated by periods of normoxia, consistent with high-frequency internal waves. High-resolution interpolations of water quality and hydroacoustic surveys suggest that fish habitat is compressed during hypoxic episodes, resulting in higher fish densities near the edges of hypoxia. At fixed locations with passive commercial fishing gear, catches with the highest values occurred when bottom waters were hypoxic for intermediate proportions of time. Proximity to hypoxia explained significant variation in bottom trawl catches, with higher catch rates near the edge of hypoxia. These results emphasize how hypoxia may elevate catch rates in various types of fishing gears, leading to a lack of association between indices of hypoxia and fishery landings. Increased catch rates of fish at the edges of hypoxia have important implications for stock assessment models that assume catchability is spatially homogeneous.

scholarly journals Aging of the population of the Republic of Serbia and Belgrade through the prism of the relation of the age structure of the population and the age structure of household members

2010 ◽  
pp. 221-227
Author(s):  
Radmila Vicentijevic
Keyword(s):  
Young People ◽  
Old Age ◽  
Age Structure ◽  
Age Groups ◽  
Structure Of Population ◽  
Age Structure Of Population ◽  
Household Members ◽  
The Republic ◽  
Average Size ◽  
The City

The most important age structure represents an age structure of population. The results of census which was held on territory of the Republic of Serbia show that the Republic of Serbia is considered to be among the countries with the oldest population. In the last fifty year's time there was registered a constant decrease in number of young people, and constant increase in number of old people. During the period of the 80s, a number of young people from 0-14 years old was twice larger than the number of people older than 65, on the republic and the city of Belgrade's level, in the last census held in 2002 for the first time there was noticed a higher amount of people older than 65 related to population in an age from 0-14. An average old age of people in the Republic has grown from 35.8 to 40.3, and in Belgrade, which was always considered as a city of youth, it is noticed an increase in average old age from 34.9 to 40.4 years of age. Index of aging increased from 0.51 in the Republic of Serbia, 0.41 in Belgrade, to 1.01 or 1.07. In the Republic of Serbia and the city of Belgrade, for more than 50 years, the average size of household became smaller for more than one member, a number of single man households has increased for 5.5%, and participation of some old age groups in a structure of household members in a specific way shows a difficult demographic situation in Serbia and the city of Belgrade. Almost 83% of households in Central Serbia don't have even one pre-school child, and among households which have children at the age of 7, one child households form the majority. In the same period the number of households with members older than 65 has increased, so households like this in 2002 formed about 39%. Out of 435491 households in Serbia, every fifth household is named as OLD AGE HOUSEHOLD and SINGLE MAN HOUSEHOLD. .

COMPARISON OF THE REGULATION OF CALCITONIN IN SERUM OF OLD AND YOUNG BUFFALO RATS

1980 ◽  
Vol 87 (1) ◽  
pp. 73-80 ◽  
Author(s):  
SHERRY F. QUEENER ◽  
N. H. BELL ◽  
SARAH M. LARSON ◽  
D. P. HENRY ◽  
EDUARDO SLATOPOLSKY
Keyword(s):  
Serum Calcium ◽  
Age Groups ◽  
Average Weight ◽  
Adrenergic Blockade ◽  
Serum Calcitonin ◽  
Progressive Decline ◽  
Thyroid Glands ◽  
Old Rats ◽  
The Mean ◽  
Mean Concentration

Studies were carried out to characterize the secretion and the effects of calcitonin in the Buffalo rat. Mean basal concentrations of calcitonin and parathyroid hormone were significantly increased in serum of rats older than 6 months of age as compared with rats between 2 and 3 months of age. The mean concentration of calcium in serum was independent of age. In both age groups, serum calcitonin was increased by administration of calcium (1 mmol/kg body wt) or isoproterenol (100 μg/kg body wt), was diminished by β-adrenergic blockade with dl-propranolol (1 mg/kg body wt) and was not altered by either pentagastrin or glucagon (200 and 100 μg/kg body wt respectively). The average weight of the thyroid glands was significantly greater in the old than in the young animals but the mean concentration of calcitonin in the thyroids was the same. Thyroparathyroidectomy produced a transient increase followed by a fall in mean serum calcium in the old rats. In contrast, a progressive decline in the mean concentration of calcium in serum was observed after thyroparathyroidectomy in the young rats. Treatment of old animals with reserpine (2·5 mg/kg body wt) markedly depleted noradrenaline in the thyroid, lowered calcitonin in serum and converted the pattern of response of serum calcium to thyroparathyroidectomy to that observed in young animals. The results provide evidence that hypercalcitonaemia occurs in aged Buffalo rats, as does hyperparathyroidism, and that the concentrations of calcitonin in blood are modulated by β-adrenergic affectors. Glucagon and pentagastrin exhibit little if any effects on calcitonin secretion in this strain of rat regardless of age.

The Sea Garfish, Reporhamphus melanochir (Cuvier & Valenciennes) (Hemi-ramphidae), in South Australia: Breeding, Age Determination, and Growth Rate

1958 ◽  
Vol 9 (1) ◽  
pp. 60 ◽  
Author(s):  
JK Ling
Keyword(s):  
Age Groups ◽  
Age Determination ◽  
South Australia ◽  
Management Policy ◽  
Spawning Period ◽  
Catch Statistics ◽  
Average Size ◽  
First Time ◽  
Second Period ◽  
Sexually Mature

There are seven macroscopic gonad stages recognizable in male sea garfish. and eight in females with which ova diameter measurements have been correlated . In South Australia the spawning period lasts from late September to early March. and activity is most intense during October and November . A second period of breeding activity may occur in February . A few females are sexually mature at 2 years. but the majority do not spawn for the first time until the end of 3 years .This applies also to males. A latent maturation cycle is demonstrated in immature female garfish. The use of otoliths for age determination is described and the method validated by Petersen length frequency polygons. The rate of growth has been deduced from calculated intermediate lengths of younger garfish, based on an otolith lengthlfish length relation and the mean lengths of older age groups. The weight of the garfish varies as the cube of the length. Females attain a larger average size than males after the third pear. Gulf St. Vincent females grow faster than those in other regions; males, however, are variable. Application of these results to a management policy for the commercial fishery is severely restricted by the inadequate official catch statistics. However, it is recommended that netting of garfish in Coffin's Bay be prohibited, but that no change in the minimum legal length should be made for the present.

scholarly journals Changes in biological indicators of the silver bream Blicca bjoerkna at the upper part of the Volga stretch of the Kuybyshev reservoir in connection with the anthropogenic impact

2021 ◽  
Vol 265 ◽  
pp. 01015
Author(s):  
Gloria F. Glazunova ◽  
Igor F. Galanin ◽  
Andrey A. Smirnov
Keyword(s):  
Anthropogenic Impact ◽  
Biological Indicators ◽  
Control Measures ◽  
Commercial Fishing ◽  
Kuibyshev Reservoir ◽  
Kuybyshev Reservoir ◽  
Average Size

In recent years, the silver bream of the upper part of the Volga stretch of the Kuibyshev reservoir maintained a tendency to reduce the average size and weight indicators. Given the good availability of food and the fact that in the area under consideration, commercial fishing of this species has not been carried out in recent years, it can be assumed that changes in biological indicators are caused by a significant impact of anthropogenic impact in the form of individual and poaching fishing. It is necessary to strengthen control measures for such types of fishing.

Effects of Fluctuations of Lead, Temperature, and Dissolved Oxygen on the Growth of Brook Trout

1969 ◽  
Vol 26 (9) ◽  
pp. 2493-2501 ◽  
Author(s):  
D. Dorfman ◽  
W. R. Whitworth
Keyword(s):  
Dissolved Oxygen ◽  
Brook Trout ◽  
Apparent Effect ◽  
Diel Fluctuations

Slug doses of lead administered once a day 5 days/week to brook trout exposed to simultaneous diel fluctuations of dissolved oxygen and temperatures showed that concentrations of 25 mg/liter of lead reduced growth. Concentrations of 15 mg/liter had little apparent effect and concentrations of 10 mg/liter had no deleterious effects on growth.

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