Changes in the Population of Lake Whitefish (Coregonus clupeaformis) in Lake Winnipeg from 1944 to 1969

1973 ◽  
Vol 30 (11) ◽  
pp. 1667-1682 ◽  
Author(s):  
E. B. Davidoff ◽  
R. W. Rybicki ◽  
K. H. Doan
Keyword(s):  
Age Groups ◽  
Total Dissolved Solids ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Coregonus Clupeaformis ◽  
Age Composition ◽  
Lake Winnipeg ◽  
Ecological Changes ◽  
Complete Collapse ◽  
Two Age Groups

Whitefish catches have fluctuated since 1952, and except in 1964 each successive peak has decreased in magnitude. Recently the overall trend has been a diminishing fishery with increasing effort.There has been a drastic change in age composition with time. Age-groups 5, 6, and 7 accounted for 81% of the catch from 1944 to 1948, age-groups 4, 5, and 6 for 89% from 1949 to 1955, age-groups 4 and 5 for 86% from 1959 to 1968, and age-groups 3 and 4 for 88% in 1969. The fishery is now dependent upon two age-groups instead of three. Natural failure of one or more important year-classes would result in a serious decline in catch, and partial or complete collapse of this fishery.Annual survival rate decreased from 34%, 1944–48 to 12%, 1959–69. Instantaneous natural mortality rate was estimated to be 0.72, and may be overestimated. The 1938–39, 1945–47, 1949, and 1957 year-classes were strong, while the 1940–44, and 1956, 1958, and 1961 year-classes were weak. The 1959 and 1960 year-classes appeared to be somewhat above average. Examination of data on total dissolved solids and temperature indicated that ecological changes were not responsible for the decline of whitefish in Lake Winnipeg.We judge that the optimum rate of fishing has been exceeded, and that the fishery itself is largely responsible for the depleted condition of the whitefish stocks in Lake Winnipeg. Fishing effort must be reduced to the point where the fishery is again dependent upon three year-classes. This should result in higher catches, and provide less fluctuation in annual catches.

Estimation of Recruitment and Natural Mortality Rate from Age-Composition and Catch Data in British Columbia Herring Populations

1955 ◽  
Vol 12 (5) ◽  
pp. 649-681 ◽  
Author(s):  
Albert L. Tester
Keyword(s):  
Mortality Rate ◽  
Age Groups ◽  
Total Mortality ◽  
Vancouver Island ◽  
Island Population ◽  
Natural Mortality ◽  
Age Composition ◽  
Catch Data ◽  
Population Average ◽  
Stable Conditions

If absolute recruitment (R) and natural mortality rate (q) are both presumed constant in each of two or more periods of stabilized fishing, it is shown that i = q + (1/R)iC, where i is instantaneous total mortality rate and C is catch in numbers. The relationship yields approximate estimates of R and q under semi-stable conditions if "average referable C" is related to apparent i, the former derived from catch data and the latter from age-composition data for post-recruited age-groups. In the herring population, in which recruitment takes place mostly at age III but is spread from ages I to IV, the average of the catch of years x and x + 1 is referable to apparent i at ages IV to V in year x + 2, at ages V to VI in year x + 3, etc. When q increases with advancing age, it is shown that R is most accurately estimated from data for ages IV to V; q is slightly overestimated at ages IV to V and underestimated at ages VI to VII and VII to VIII. From data for periods of approximate stability in the lower east coast of Vancouver Island population, average R is estimated at about 500 million fish per year; average q appears to increase with age, ranging from about 0.4 at ages IV to V to about 0.85 at ages VII to VIII. For a recent period of stabilized intensive fishing, a rough estimate of the average initial size of the fishable stock, based on age-composition and catch data, agrees well with that estimated by another method. For populations along the west coast of Vancouver Island, q also appears to increase with advancing age; R is estimated at about 400 million fish. In an appendix it is shown that a method of estimating q from age-composition and effort data gives unsatisfactory results because effort expended in herring fishing is not proportional to rate of fishing of the stock.

Estimation of Effective Effort from Catch-at-Age Data

1993 ◽  
Vol 50 (11) ◽  
pp. 2421-2428 ◽  
Author(s):  
J. E. Paloheimo ◽  
Yong Chen
Keyword(s):  
Age Groups ◽  
Simulated Data ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
A Value ◽  
Basic Equations ◽  
Highly Correlated ◽  
High Degree ◽  
Two Age Groups

We present a method for estimating effective efforts or fishing mortality rates based on a linearized version of the catch equation. Catch-at-age for at least two age groups over a series of years is required. The method presupposes a value for natural mortality rate (M). The method is validated using simulated data with an appropriate error structure. The algorithm always converges to a set of effective efforts that are compatible with the known catches. Nevertheless, the solution to the basic equations is not unique although the different solutions are typically highly correlated. If the M assumed by the algorithm is the same as the actual M the iterated effective efforts are typically very close to the true effective efforts or fishing mortality rates. If the assumed M is too high or too low the pattern of effective efforts is still recovered to a high degree of accuracy, typically 0.90 < r < 1.00, even though M may be off by as much as 60%. When data for three or more age groups are available the method is extended to at least squares procedure that takes into account the increasing uncertainty of catches with age.

Some Methods for Estimating Exploited Populations

1966 ◽  
Vol 23 (10) ◽  
pp. 1553-1574 ◽  
Author(s):  
K. Radway Allen
Keyword(s):  
Fishing Effort ◽  
Recruitment Rate ◽  
Initial Population ◽  
Natural Mortality ◽  
Age Composition ◽  
Natural Reproduction ◽  
Final Estimate ◽  
The Mean ◽  
Reproduction Method ◽  
New Recruits

Three methods of estimating population and one of estimating recruitment are described which are suitable for use where data are available on annual age composition, the numbers caught, and the effort expended in taking a known part of the catch.The recruitment rate is estimated, as the proportion of new recruits in the recruited population, from age composition data year by year without regard to the sizes of the parent populations, and from the approximate fishing mortality rate.The "q" population method estimates q, the coefficient of catchability, by comparing the rate of disappearance of a fixed group of year-classes with the rate of accumulation of fishing effort, using the rate of disappearance with age in a similar, unexploited population to eliminate the effects of natural mortality. The annual populations are then estimated from q and the catch per unit effort.The natural mortality and reproduction method is basically a modification of the DeLury method with an allowance for natural reproduction and recruitment. It obtains a series of estimates of the base year population by considering each of the periods beginning in this year and ending in each successive subsequent year, the final estimate being the mean of this series.The expected catch method takes as unknowns the initial population and the value of q, estimates the expected catches in each year, and compares them with the actual catches. It determines the values of the initial population and q which minimize the sum of the squares of the differences.Examples are worked out in full for all methods.

Tagging Returns, Age Studies and Fluctuations in Abundance of Lake Winnipeg Whitefish, 1931–1951

1954 ◽  
Vol 11 (3) ◽  
pp. 284-309 ◽  
Author(s):  
W. A. Kennedy
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Weather Conditions ◽  
Fishing Effort ◽  
Coregonus Clupeaformis ◽  
Lake Winnipeg ◽  
Equal Strength ◽  
Age Studies ◽  
Annual Mortality ◽  
Age Determinations

On the basis of 2,003 lake whitefish, Coregonus clupeaformis, tagged in 1938, of which 126 were recovered during the next five years, there is evidence that fish released together tend to stay together for years, and that the proportion of a population captured during a certain time by a unit amount of fishing effort can fluctuate greatly (a plausible explanation is the effect of variations in weather conditions). On the basis of age determinations of 12,975 whitefish in samples taken annually from 1937 to 1951, growth rate was determined, the total annual mortality rate among fully exploited fish was calculated to be 64 per cent over several years, and it appeared that all year-classes had been of about equal strength in recent years. The generally accepted idea that fluctations in fishing success correspond to fluctuations in abundance of whitefish is probably erroneous. Possibly the Lake Winnipeg whitefish are underfished.

Changes in Mean Weight, Sea-Age Composition, and Catch-per-Unit-Effort of Atlantic Salmon (Salmo salar) Angled in the Godbout River, Quebec, 1859–1983

1986 ◽  
Vol 43 (2) ◽  
pp. 281-287 ◽  
Author(s):  
Alex T. Bielak ◽  
Geoffrey Power
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Age Groups ◽  
Fishing Effort ◽  
Commercial Fisheries ◽  
Catch Per Unit Effort ◽  
Age Composition ◽  
Atlantic Salmon Salmo Salar ◽  
The Mean ◽  
Selective Effects

A weight-age classification, based on recent catches, was retroactively applied to angled Atlantic salmon (Salmo salar) catches recorded in the log of the Godbout salmon club between 1859 and 1983. Over this period, numbers of salmon caught have fluctuated with a periodicity of 20–30 yr but catches have been maintained. There has been a big increase in fishing effort, and the proportion of two-sea-year to previously spawned fish has increased. The mean weight of these age groups has declined 0.005–0.009 kg∙yr−1. These changes are attributed to the selective effects of commercial fisheries on the stock.

scholarly journals SEBARAN KELOMPOK UMUR DAN RASIO POTENSI PEMIJAHAN BANGGAI CARDINAL (Pterapogon kauderni, Koumans 1933) MENGGUNAKAN MODEL LB-SPR DI KEPULAUAN BANGGAI SULAWESI TENGAH

2017 ◽  
Vol 22 (3) ◽  
pp. 197
Author(s):  
Sri Turni Hartati ◽  
Kamaluddin Kasim
Keyword(s):  
Reference Point ◽  
Sex Differentiation ◽  
Age Groups ◽  
Length Distribution ◽  
Relative Length ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Gonadal Maturity ◽  
Fish Samples ◽  
Spawning Potential Ratio

Banggai cardinal (Pterapogon kauderni, Koumans 1933) adalah jenis ikan endemik yang saat ini masih diperdagangkan sebagai ikan hias. Informasi biologi seperti ukuran dan estimasi kelompok umur dapat digunakan untuk mengetahui status pemanfaatan di habitat aslinya, yang diperlukan dalam upaya pengelolaan. Penelitian ini bertujuan untuk mengetahui status pemanfaatan stok Banggai cardinal melalui estimasi kelompok umur ikan dan menggunakan informasi tersebut sebagai indikator biologi (Biological Reference Point) Spawning Potential Ratio (SPR) melalui pendekatan Length-Based SPR model. Pengukuran panjang ikan dilakukan terhadap 7.014 ekor ikan sampel selama tahun 2010 hingga 2011, dan pengamatan aspek biologi seperti jenis kelamin, tingkat kematangan gonad, serta fekunditas dilakukan terhadap 394 ekor ikan sampel. Hasil penelitian menunjukkan bahwa ikan yang tertangkap berumur 10-11 bulan, dengan ukuran panjang 32,7 – 35,2 mm FL, lebih kecil dari  ukuran pertama kali matang gonad (Lm) sebesar 36,1 – 44,4 mm FL. Rata-rata Nilai SPRsebesar 44,6% masih di atas ambang batas lebih tangkap (overfishing threshold) 30%. Nilai SPR secara signifikan menurun dari 46,8% pada 2010 menjadi 40,4% pada 2011. Sebanyak 50% ikan betina matang gonad (Lm) pada ukuran 37 mm FL dan 50% tertangkap (Selectivity/SL50) pada ukuran 32 mm FL (SL50< L50). Laju penangkapan relatif terhadap mortalitas alami (F/M) sebesar 0,57 mengindikasikan bahwa upaya penangkapan (relative fishing effort) telah mencapai  57% terhadap laju kematian alaminya. Banggai cardinal (Pterapogon kaudernii) fish is an endemic species which is traded as an ornamental fish. Population parameters such as length distribution and ages of P. kaudernii are required to estimate status of the species as a part of management purposes. This study aimed to determine the stock status of Banggai cardinal through estimation of the age groups and use that information as biological reference point to estimate the Spawning Potential Ratio (SPR) through Length-Based SPR model. Length of fish samples were measured of 7,014 fish samples during the year 2010 to the year 2011 while gonadal maturity, fecundity and sex differentiation were obtained from 394 individuals fish samples. The results show that fisherman caught mostly young individual fish, aged 10-11 months with relative length 32.7 - 35.2 mm FL and at below the size of length at first maturity (Lm) of 36.1 - 44.4 mm FL. Estimation of SPR shows that stock has been in healthy status which indicated by average SPR of 44.6% which still above the overfishing threshold by 30%. However, the values of SPR were declined significantly from 46.8% in 2010 to be 40.4% in 2011. As many as 50% of mature female fish found on the size of 37 mm FL and 50% caught (Selectivity/SL50) on the size of 32 mm FL (SL50 <L50). The rate of relative fishing mortality (F) to natural mortality (F / M) of 0.57 indicates relative fishing effort has reached 57% of the rate of natural mortality. 

Less known aspects of Penaeus kerathurus (Forskål, 1775) (Decapoda, Penaeidae) obtained from the fishermen in the Sea of Marmara: age, growth, and mortality rates

Crustaceana ◽  
2020 ◽  
Vol 93 (9-10) ◽  
pp. 1185-1195
Author(s):  
M. Arslan İhsanoğlu
Keyword(s):  
Growth Parameters ◽  
Economic Value ◽  
Age Groups ◽  
Length Distribution ◽  
Total Mortality ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Sea Of Marmara ◽  
Age Composition ◽  
Important Species

Abstract Penaeus kerathurus is an important species for the fishery, thanks to its high nutritional and economic value. Therefore, this study attempts to determine the length distribution, length-weight relationship, age composition, growth parameters, and mortality rates of a population of P. kerathurus. The material was monthly collected from commercial fishermen in and around Karabiga and the Gulf of Erdek in the Sea of Marmara, between May 2018 and April 2019. The carapace length-weight relationships were calculated as W = 0.0023 × CL2.57, W = 0.0036 × CL2.46, and W = 0.0026 × CL2.56 for the females, males and both sexes combined, respectively. The population studied was distinguished into four age groups, and the tmax (= maximum theoretical age) was found to be reached at 11.9 year. The growth parameters were observed to be  = 60.9 mm; K = 0.24 year−1, and t0 = −0.58 year. The rates of total mortality (Z), natural mortality (M), fisheries mortality (F), and exploitation (E) were calculated to be 1.32, 0.43, 0.89, and 0.67, respectively. The results showed that P. kerathurus suffers from a heavy fishing pressure in the sampled area.

Dynamics and Exploitation of Lake Whitefish in Southern Georgian Bay

1966 ◽  
Vol 23 (2) ◽  
pp. 221-274 ◽  
Author(s):  
Daniel Cucin ◽  
Henry A. Regier
Keyword(s):  
Mortality Rates ◽  
Exponential Model ◽  
Fishing Effort ◽  
Natural Mortality ◽  
Coregonus Clupeaformis ◽  
Commercial Catch ◽  
Georgian Bay ◽  
Gill Nets ◽  
Size At Age ◽  
Mean Risk

Instability of the population of Coregonus clupeaformis (Mitchill) in southern Georgian Bay from 1948 to 1964 was evidently partly due to intensive fishing.The population was discrete at least from 1956 to 1964 as determined by extensive tagging. From 1948 to 1964, estimated effective fishing effort varied 10-fold and annual yields almost 20-fold, with two cycles of abundance and scarcity. Strength of 1951–59 year-classes, defined as population size at age III, varied 40-fold. In spite of the marked instability, the population was in recent years more stable than any other whitefish population in Georgian Bay or Lake Huron.Almost all the commercial catch was made with gill nets of [Formula: see text] mesh. In 1957, fishing depended largely on age VII–IX fish; by 1964, on those of age V and VI. Apparent growth rate increased during this period: in 1957 age XII fish weighed 3.4 lb; in 1964 age VI weighed 3.7 lb. From 1959 to 1964, reproduction depended largely on males age IV+ and older and longer than 17 inches, and on females age V+ and older and longer than 18 inches.Natural mortality coefficients (exponential model) averaged 0.41 for fish of the 1948–58 year-classes beyond age III. Gillnetting was largely restricted to 2 months in late spring and two in fall. In each fishing season these gill nets took about 40% of the survivors of a year-class after it became fully vulnerable, at ages V, VI, and VII during the early 1960s.Combining growth and natural mortality rates in a biomass curve indicated that individual year-classes would provide highest yields when fished intensively at age IV, or slightly earlier than they were fished in the early 1960s. Yet the only hypothesis that might explain the continued existence of a fishable population was that relatively large parts of the habitat were either legally closed or unsuitable for fishing. Evidently the fishing was intense and increasing the effort would mean risk of a population collapse.

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.

Concordance of Glucose-Based and of HbA1c-Based Diagnoses of Diabetes in Patients with Peripheral Artery Disease—A Comparison between Two Age Groups

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 1522-P
Author(s):  
CHRISTOPH H. SAELY ◽  
ALEXANDER VONBANK ◽  
CHRISTINE HEINZLE ◽  
DANIELA ZANOLIN ◽  
BARBARA LARCHER ◽  
...  
Keyword(s):  
Peripheral Artery Disease ◽  
Age Groups ◽  
Peripheral Artery ◽  
Artery Disease ◽  
Two Age Groups
Sign in / Sign up

Export Citation Format

Share Document