Optimizing Survey Design for Determining Age Structure of Fish Stocks: an Example from British Columbia Pacific Herring (Clupea harengus pallasi)

1983 ◽  
Vol 40 (5) ◽  
pp. 588-597 ◽  
Author(s):  
J. F. Schweigert ◽  
J. R. Sibert
Keyword(s):  
Age Structure ◽  
Survey Design ◽  
Clupea Harengus ◽  
Pacific Herring ◽  
Stage Design ◽  
Fish Stocks ◽  
Cost Structures ◽  
Survey Statistics ◽  
Clupea Harengus Pallasi ◽  
Survey Designs

Sampling commercial catches of fishes is considered for the first time from the viewpoint of survey statistics. The determination of the age-structure of Pacific herring (Clupea harengus pallasi) is approached as a multistage subsampling problem. Optimum allocation of sampling resources is obtained by minimizing the product of total cost and total variance. Optimal survey designs are analyzed for a variety of reasonable cost structures for all age-classes. The most reasonable design that applies to all areas of the coast is to use a two-stage design, including a single sample of about 60 aged fish per vessel. The number of vessels to sample is a function of the required precision and available resources.

A Model for Predicting Pacific Herring (Clupea harengus pallasi) Spawn Density from Diver Observations

1982 ◽  
Vol 39 (10) ◽  
pp. 1361-1365 ◽  
Author(s):  
J. F. Schweigert ◽  
D. Fournier
Keyword(s):  
Survey Design ◽  
Stock Assessment ◽  
Clupea Harengus ◽  
Data Series ◽  
Pacific Herring ◽  
Percent Cover ◽  
Number Of Layers ◽  
Clupea Harengus Pallasi ◽  
Biological Interpretation ◽  
Sampling Survey

A series of mathematical models were examined to predict the density of Pacific herring (Clupea harengus pallasi) spawn in 1-m2 quadrats from diver observations of the dominant vegetation substrate, the number of layers of eggs on the vegetation, and the density of the vegetation in the quadrat (percent cover). The most appropriate model was chosen statistically and used to make predictions for comparison with egg counts. Outliers were identified and if a plausible biological interpretation was found, these were deleted from the data series. The model provides an efficient and precise means for estimating herring spawn density from diver observations and could be incorporated into a sampling survey design for estimating spawn abundance for stock assessment.Key words: mathematical model, Pacific herring, Clupea harengus pallasi; spawn density, stock assessment

Fixation Shrinkage of Herring Larvae: Effects of Salinity, Formalin Concentration, and Other Factors

1982 ◽  
Vol 39 (8) ◽  
pp. 1138-1143 ◽  
Author(s):  
D. E. Hay
Keyword(s):  
Clupea Harengus ◽  
Pacific Herring ◽  
Larval Size ◽  
Factors Affecting ◽  
Clupea Harengus Pallasi

The most important factors affecting the degree of larval shrinkage of Pacific herring (Clupea harengus pallasi) larvae during fixation are the salinity and formalin concentrations and initial larval size. In low formalin concentrations (2–5% formalin) shrinkage increased from less than 2% shrinkage at low salinities to about 10% shrinkage in seawater formalin. In high formalin concentrations (20–30% formalin) shrinkage was fairly uniform, ranging from about 3% shrinkage in low salinities to about 5% in seawater. Shrinkage in fixatives stored at 0, 5, 10, 20, and 30 °C was slightly higher (1–2%) at the higher temperatures. Buffering agents and starvation had no effect on shrinkage. Small, young larvae shrank relatively more than larger older larvae.Key words: herring larvae, fixation, shrinkage, formalin, salinity

Chill Stowage and Development of Rancidity in Frozen Pacific Herring, Clupea harengus pallasi

1978 ◽  
Vol 35 (4) ◽  
pp. 473-477 ◽  
Author(s):  
E. Bilinski ◽  
R. E. E. Jonas ◽  
Y. C. Lau
Keyword(s):  
Key Words ◽  
Peroxide Value ◽  
Frozen Storage ◽  
Thiobarbituric Acid ◽  
Acid Number ◽  
Clupea Harengus ◽  
Pacific Herring ◽  
Clupea Harengus Pallasi ◽  
Low Levels

Freshly caught Pacific herring, Clupea harengus pallasi, were stowed in ice or refrigerated seawater (RSW) at −0.8 °C for 0, 2, and 4 d and were then filleted and stored frozen (−28 °C) for up to 11 mo. The development of rancidity was determined using the peroxide value and the thiobarbituric acid number. During the chill stowage before freezing, the lipids from the flesh were not subjected to any significant oxidation. In Cryovac-vacuum-packed fillets the rancidity remained at low levels during the duration of frozen storage. If oxygen was present during frozen storage, chill stowage accelerated the development of rancidity and this effect was more pronounced in the case of RSW than ice, especially after 4 d of stowage. Key words: Pacific herring, Clupea harengus pallasi, rancidity, icing, refrigerated seawater, frozen storage

Alternative Harvest Strategies for Pacific Herring (Clupea harengus pallasi)

1988 ◽  
Vol 45 (5) ◽  
pp. 888-897 ◽  
Author(s):  
D. L. Hall ◽  
R. Hilborn ◽  
M. Stocker ◽  
C. J. Walters
Keyword(s):  
Management Strategies ◽  
Clupea Harengus ◽  
Pacific Herring ◽  
Harvest Rate ◽  
Strait Of Georgia ◽  
Clupea Harengus Pallasi ◽  
Current Management Strategy ◽  
Stock Recruitment ◽  
Spawning Biomass ◽  
Constant Escapement

A simulated Pacific herring (Clupea harengus pallasi) population is used to evaluate alternative management strategies of constant escapement versus constant harvest rate for a roe herring fishery. The biological parameters of the model are derived from data on the Strait of Georgia herring stock. The management strategies are evaluated using three criteria: average catch, catch variance, and risk. The constant escapement strategy provides highest average catches, but at the expense of increased catch variance. The harvest rate strategy is favored for its reduced variance in catch and only a slight decrease in mean catch relative to the fixed escapement strategy. The analysis is extended to include the effects of persistent recruitment patterns. Stock–recruitment analysis suggests that recruitment deviations are autocorrelated. Correlated deviations may cause bias in regression estimates of stock–recruitment parameters (overestimation of stock productivity) and increase in variation of spawning stock biomass. The latter effect favors the constant escapement strategy, which fully uses persistent positive recruitment fluctuations. Mean catch is depressed for the harvest rate strategy, since the spawning biomass is less often located in the productive region of the stock–recruitment relationship. The model is used to evaluate the current management strategy for Strait of Georgia herring. The strategy of maintaining a minimum spawning biomass reserve combines the safety of the constant escapement strategy and the catch variance reducing features of the harvest rate strategy.

Environmental Variation and Recruitment of Pacific Herring (Clupea harengus pallasi) in the Strait of Georgia

1985 ◽  
Vol 42 (S1) ◽  
pp. s174-s180 ◽  
Author(s):  
Max Stocker ◽  
Vivian Haist ◽  
David Fournier
Keyword(s):  
Environmental Variables ◽  
River Discharge ◽  
Clupea Harengus ◽  
Pacific Herring ◽  
Strait Of Georgia ◽  
Clupea Harengus Pallasi ◽  
Age Structured ◽  
Age Structured Model ◽  
The Relationship ◽  
Spawning Success

We used an age-structured model to estimate recruitment for the Strait of Georgia Pacific herring (Clupea harengus pallasi) population. The model used for herring is a version of the model described in Fournier and Archibald (1982. Can. J. Fish. Aquat. Sci. 39: 1195–1207), modified to include spawn survey information. Three structural assumptions are made to include the spawn data: (1) the form of the relationship between the actual spawn and the observed spawn, (2) the form of the relationship between escapement and actual spawn, and (3) the existence of a Ricker spawn–recruitment relationship, with a multiplicative environmental component. In order to determine which environmental factors had a significant effect on recruitment, we attempted to explain the residual variation from the Ricker curve with the environmental variables using exploratory correlations. Temperature, river discharge, sea level, and sunlight were examined. A multiplicative, environmental-dependent Ricker spawn–recruitment model was used to identify significant environmental variables. The model suggests a significant dome-shaped relationship between temperature and spawning success with an optimal temperature during larval stages resulting in maximum production of recruits. Also, increased spawning success is associated with increased summer river discharge. The significant environmental variables were included in the age-structured model in a stock–environment–recruitment relationship, and all model parameters were reestimated. The overall model fit improved only marginally with the inclusion of environmental variables, as indicated by the objective function value. However, the S–R component of the objective function dropped by 23% when environmental variables were included.

Factors Affecting the Distribution, Abundance, and Measurement of Pacific Herring (Clupea harengus pallasi) Spawn

1987 ◽  
Vol 44 (6) ◽  
pp. 1181-1194 ◽  
Author(s):  
D. E. Hay ◽  
A. R. Kronlund
Keyword(s):  
Survey Methods ◽  
Abiotic Factors ◽  
Early Years ◽  
Clupea Harengus ◽  
Pacific Herring ◽  
Biological Factors ◽  
Factors Affecting ◽  
Clupea Harengus Pallasi ◽  
The Mean ◽  
Stock Abundance

Records of the date, location, and magnitude of Pacific herring (Clupea harengus pallasi) spawnings in British Columbia, collected since 1928, were compiled and analysed. In the early years of spawn surveys, adjacent spawnings were often reported as single events. Gradually, this practice has changed so that each spawning has a separate record. As a consequence of this change in methods, the mean length of spawnings has decreased in recent years but the total numbers of records has increased. Estimates of mean spawning width and intensity have also changed, partly due to changing survey methods as well as changing spawning distributions. A spawn abundance index is developed to account for these temporal changes. Abiotic factors affecting the distribution and abundance of spawn deposition include sea surface temperatures and the fishery. Biological factors affecting spawn distribution and abundance are not as well defined, but it is shown that in some situations, spawn dimensions may change as a function of stock abundance.

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