scholarly journals The unknown Baranov. Forty years of polemics over the formal theory of the life of fishes

2020 ◽  
Author(s):  
Alexei Sharov
Keyword(s):  
Stock Assessment ◽  
Formal Theory ◽  
100Th Anniversary ◽  
Natural Mortality ◽  
Population Abundance ◽  
Modern Age ◽  
Fishery Science ◽  
Points Of View ◽  
Age Structured ◽  
Scientific Debates

Abstract The year 2018 marked the 100th anniversary of the publication of paper “On the question of the biological basis of fisheries” by F.I. Baranov considered a cornerstone paper of modern fishery science. Baranov formalized population dynamics by describing changes in population abundance using differential equations, introducing the concept of instantaneous fishing and natural mortality rates, and developing his catch equation, which is the foundation of most modern age-structured stock assessment models. Baranov was the first to show the effect of fishing on population structure based on theoretical grounds. At the time of its publication, Baranov’s paper did not receive much attention in Russia and was completely unknown to scientists in the West. The second publication (On the question of the dynamics of the fishing industry, 1925) received substantial criticism from many and sparked a furious debate between Baranov and his opponents that lasted for several decades. The history and content of those debates, expressed in multiple papers by Baranov, is still largely unknown. I describe the essence of arguments by Baranov and his opponents. The story of these scientific debates reveals how different philosophical concepts and dominant points of view evolved through time.

Effects of an erroneous natural mortality rate on a simple age-structured stock assessment

1999 ◽  
Vol 56 (10) ◽  
pp. 1721-1731 ◽  
Author(s):  
William G Clark
Keyword(s):  
Mortality Rate ◽  
Stock Assessment ◽  
Natural Mortality ◽  
Structured Model ◽  
Harvest Rate ◽  
Specific Selectivity ◽  
Age Structured ◽  
Age Structured Model ◽  
Size Estimates

The abundance of many stocks is estimated by fitting an age-structured model to catch-at-age and relative abundance data from the commercial fishery and scientific surveys. The natural mortality rate used in the model is usually estimated externally and its value is uncertain. An erroneous natural mortality rate will bias the stock size estimates obtained by fitting the model and will also bias the yield calculations that are done to choose a harvest rate and recommend quotas. This paper describes the general features of both effects by analyzing a simple age-structured model fitted to artificial data. It is shown that an erroneous natural mortality rate mainly affects the estimates of fishing mortality and hence abundance but not the estimates of age-specific selectivity. Errors in estimated abundance and target harvest rate are always in the same direction, with the result that, in the short term, extremely high exploitation rates can be recommended (unintentionally) in cases where the natural mortality rate is overestimated and historical exploitation rates in the catch-at-age data are low. A conservative (low) estimate of natural mortality can avoid that danger. Long-term yield under either an FMSY or F35% strategy is not very sensitive to error in natural mortality rate unless it is grossly underestimated.

Incorporating Uncertainty into Fishery Models

2002 ◽  
Keyword(s):  
Striped Bass ◽  
Population Model ◽  
Input Data ◽  
Stock Assessment ◽  
Population Analysis ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Sources Of Uncertainty ◽  
Incorrect Model ◽  
Age Structured

<em>Abstract.—</em> A stock assessment of Atlantic striped bass <em>Morone saxatilis </em> was presented to illustrate potential sources of uncertainty in application of an age-based population model. Erroneous conclusions in stock assessment can result from incorrect model selection, input data that are not representative of the target population, and improper configuration of the selected model. Influence of incorrect input data and model configuration was investigated using striped bass catch-at-age data analyzed with a tuned virtual population analysis model (ADAPT VPA). Variations in model configurations were explored in addition to sensitivity to input parameters such as natural mortality. Violation of the assumption of constant natural mortality-at-age had a significant influence on the resulting estimates of <EM>F </EM> and stock size. Discard losses, particularly from the commercial fishery, were the largest source of uncertainty in the catch-at-age. Uncertainty due to process error in the VPA model was characterized by bootstrap realizations of the nonlinear least-squares estimates of fishing mortality. The implications associated with fishing at various <EM>F</EM> s were also examined using a stochastic projection model. A comparison of fishing mortality estimates derived from two independent models, an age-structured population model and a tag-recovery model, indicated that both methods produced equivalent results. Evaluation of the striped bass stock assessment demonstrates that uncertainty could result from a variety of sources but this variability was only partially captured within the model framework. Understanding the possible sources of uncertainty and implications in interpreting model results should benefit the analyst in providing assessment advice to managers.

Role of disease in abundance of a Pacific herring (Clupea pallasi) population

2003 ◽  
Vol 60 (10) ◽  
pp. 1258-1265 ◽  
Author(s):  
Gary D Marty ◽  
Terrance J. Quinn II ◽  
Greg Carpenter ◽  
Theodore R Meyers ◽  
Neil H Willits
Keyword(s):  
Stock Assessment ◽  
Assessment Model ◽  
Fish Mortality ◽  
Viral Hemorrhagic Septicemia Virus ◽  
Pacific Herring ◽  
Population Abundance ◽  
Total N ◽  
Clupea Pallasi ◽  
The Pacific ◽  
Age Structured

Disease significantly affects population abundance of Pacific herring (Clupea pallasi). Comprehensive epidemiological study of the Pacific herring population of Prince William Sound, Alaska, U.S.A., from 1994 to 2000 included complete necropsy examination of 230–500 fish each spring and 40–160 fish each fall (total n = 2983 fish). Mortality is best estimated, through modifications of an age-structured assessment model, using a disease index that combines the prevalence of viral hemorrhagic septicemia virus (VHSV) with the prevalence of ulcers. Risk factors for an epidemic include poor body condition and abundant recruitment before spawning in the spring. Prevalence of the pathogen Ichthyophonus hoferi increased as fish aged, but changes in I. hoferi prevalence were not related to changes in population abundance. Disease that caused an epidemic in 1998 (VHSV and ulcers) nearly disappeared from the population when changes in abundance were detected by traditional stock assessment methods in 1999. Disease significantly affects recruitment — the two lowest recruitment estimates on record, in 1994 and 1999, followed increased natural mortality of adults in 1993 and 1998.

scholarly journals Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa

2010 ◽  
Vol 67 (6) ◽  
pp. 1185-1197 ◽  
Author(s):  
C. Fernández ◽  
S. Cerviño ◽  
N. Pérez ◽  
E. Jardim
Keyword(s):  
Time Series ◽  
Stock Assessment ◽  
Reference Points ◽  
Assessment Model ◽  
Marine Science ◽  
Fishing Mortality ◽  
Change Over Time ◽  
Age Structured ◽  
Available Information ◽  
Over Time

Abstract Fernández, C., Cerviño, S., Pérez, N., and Jardim, E. 2010. Stock assessment and projections incorporating discard estimates in some years: an application to the hake stock in ICES Divisions VIIIc and IXa. – ICES Journal of Marine Science, 67: 1185–1197. A Bayesian age-structured stock assessment model is developed to take into account available information on discards and to handle gaps in the time-series of discard estimates. The model incorporates mortality attributable to discarding, and appropriate assumptions about how this mortality may change over time are made. The result is a stock assessment that accounts for information on discards while, at the same time, producing a complete time-series of discard estimates. The method is applied to the hake stock in ICES Divisions VIIIc and IXa, for which the available data indicate that some 60% of the individuals caught are discarded. The stock is fished by Spain and Portugal, and for each country, there are discard estimates for recent years only. Moreover, the years for which Portuguese estimates are available are only a subset of those with Spanish estimates. Two runs of the model are performed; one assuming zero discards and another incorporating discards. When discards are incorporated, estimated recruitment and fishing mortality for young (discarded) ages increase, resulting in lower values of the biological reference points Fmax and F0.1 and, generally, more optimistic future stock trajectories under F-reduction scenarios.

Natural mortality diagnostics for state-space stock assessment models

2021 ◽  
Vol 243 ◽  
pp. 106062
Author(s):  
Andrea M.J. Perreault ◽  
Noel G. Cadigan
Keyword(s):  
State Space ◽  
Stock Assessment ◽  
Natural Mortality

Interaction Between Stock Area, Stock Abundance, and Catchability Coefficient

1985 ◽  
Vol 42 (5) ◽  
pp. 989-998 ◽  
Author(s):  
G. H. Winters ◽  
J. P. Wheeler
Keyword(s):  
Stock Assessment ◽  
Population Decline ◽  
Clupea Harengus ◽  
Atlantic Herring ◽  
Population Abundance ◽  
Commercial Catch ◽  
Standard Manner ◽  
Clupea Harengus Harengus ◽  
The Relationship ◽  
Stock Abundance

The relationship between commercial catch-rates and population density upon which many stock assessment models depend assumes that stock area (A) is constant and independent of population abundance. Starting from a theoretical demonstration that the catchability coefficient (q) is inversely proportional to A, we establish the empirical basis of this relationship through comparisons of q and A of various Northwest Atlantic herring (Clupea harengus harengus) stocks and, in more detail, for Fortune Bay herring. For these stocks the relationship was of the form q = cA−b. For Atlantic herring stocks, levels of b were in excess of 0.80. In Fortune Bay herring, reductions in abundance were accompanied by proportional reductions in A, which in turn was inversely correlated with changes in q. School size, measured as catch per set, also declined as population levels declined but the change was not proportional. Published findings indicate that pelagic stocks in particular, and fish stocks in general, exhibit a common response of reductions in A with interactive increases in the q during periods of rapid population decline. We conclude that the conventional assumption of a constant stock area is usually violated due to the systematic interaction between A and population abundance which is reflected in an inverse relationship between stock abundance and q. Calibration of sequential population models should therefore be restricted to research vessel data collected in a standard manner and covering the distributional area of the stock.

Understanding historical summer flounder (Paralichthys dentatus) abundance patterns through the incorporation of oceanography-dependent vital rates in Bayesian hierarchical models

2019 ◽  
Vol 76 (8) ◽  
pp. 1275-1294 ◽  
Author(s):  
Cecilia A. O’Leary ◽  
Timothy J. Miller ◽  
James T. Thorson ◽  
Janet A. Nye
Keyword(s):  
Population Dynamics ◽  
Gulf Stream ◽  
Stock Assessment ◽  
Deviance Information Criterion ◽  
Information Criterion ◽  
Natural Mortality ◽  
Vital Rates ◽  
Summer Flounder ◽  
Paralichthys Dentatus ◽  
Abundance Patterns

Climate can impact fish population dynamics through changes in productivity and shifts in distribution, and both responses have been observed for many fish species. However, few studies have incorporated climate into population dynamics or stock assessment models. This study aimed to uncover how past variations in population vital rates and fishing pressure account for observed abundance variation in summer flounder (Paralichthys dentatus). The influences of the Gulf Stream Index, an index of climate variability in the Northwest Atlantic, on abundance were explored through natural mortality and stock–recruitment relationships in age-structured hierarchical Bayesian models. Posterior predictive loss and deviance information criterion indicated that out of tested models, the best estimates of summer flounder abundances resulted from the climate-dependent natural mortality model that included log-quadratic responses to the Gulf Stream Index. This climate-linked population model demonstrates the role of climate responses in observed abundance patterns and emphasizes the complexities of environmental effects on populations beyond simple correlations. This approach highlights the importance of modeling the combined effect of fishing and climate simultaneously to understand population dynamics.

scholarly journals An integrated tagging model to estimate mortality rates of Albemarle Sound – Roanoke River striped bass

2017 ◽  
Vol 74 (7) ◽  
pp. 1061-1076 ◽  
Author(s):  
Julianne E. Harris ◽  
Joseph E. Hightower
Keyword(s):  
Striped Bass ◽  
Stock Assessment ◽  
Mortality Rates ◽  
Natural Mortality ◽  
Fishing Mortality ◽  
Albemarle Sound ◽  
High Reward ◽  
Accuracy And Precision ◽  
Summer Mortality ◽  
Roanoke River

We developed an integrated tagging model to estimate mortality rates and run sizes of Albemarle Sound – Roanoke River striped bass (Morone saxatilis), including (i) a multistate component for telemetered fish with a high reward external tag; (ii) tag return components for fish with a low reward external or PIT tag; and (iii) catch-at-age data. Total annual instantaneous mortality was 1.08 for resident (458–899 mm total length, TL) and 0.45 for anadromous (≥900 mm TL) individuals. Annual instantaneous natural mortality was higher for resident (0.70) than for anadromous (0.21) fish due to high summer mortality in Albemarle Sound. Natural mortality for residents was substantially higher than currently assumed for stock assessment. Monthly fishing mortality from multiple sectors (including catch-and-release) corresponded to seasonal periods of legal harvest. Run size estimates were 499 000–715 000. Results and simulation suggest increasing sample size for the multistate component increases accuracy and precision of annual estimates and low reward tags are valuable for estimating monthly fishing mortality rates among sectors. Our results suggest that integrated tagging models can produce seasonal and annual mortality estimates needed for stock assessment and management.

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