scholarly journals A spatiotemporal model for snow crab (Chionoecetes opilio) stock size in the southern Gulf of St. Lawrence

2017 ◽  
Vol 74 (11) ◽  
pp. 1808-1820 ◽  
Author(s):  
Noel G. Cadigan ◽  
Elmer Wade ◽  
Anders Nielsen
Keyword(s):  
East Coast ◽  
Snow Crab ◽  
Natural Mortality ◽  
General Increase ◽  
Chionoecetes Opilio ◽  
Spatiotemporal Model ◽  
Stock Size ◽  
Stock Biomass ◽  
Survey Results ◽  
The Relationship

We develop a high-resolution spatiotemporal model of stock size and harvest rates for snow crab (Chionoecetes opilio) in the southern Gulf of St. Lawrence, which supports an economically important fishery off the east coast of Canada. It is a spatial and weekly model during 1997–2014 that utilizes within-season depletion based on catch per unit of effort (CPUE; kg·pot–1) and also biomass values from a survey designed specifically for this stock. The model is formulated in a state-space framework. The main contribution of the model is to provide a better understanding of fishery-dependent factors that affect CPUE. There is strong evidence of density dependence in the relationship with CPUE and stock biomass, in addition to a general increase in CPUE catchability over time that may be related to changes in gear soak time and spatial variation in catchability. We also find that a natural mortality rate of 0.4 provides a better fit to survey results. Model results suggest that there is no evidence of effort saturation in the fishery.

scholarly journals Time-series analysis of abundance indices of young fish

2004 ◽  
Vol 61 (2) ◽  
pp. 176-183 ◽  
Author(s):  
G. Gudmundsson
Keyword(s):  
Time Series ◽  
Time Series Analysis ◽  
Large Deviation ◽  
Natural Mortality ◽  
Cohort Size ◽  
Young Fish ◽  
Stock Size ◽  
Series Analysis ◽  
Abundance Indices ◽  
The Relationship

Abstract Catch-at-age analysis provides estimates of stock size at ages when the fish have reached catchable size. Survey indices contain information about relative cohort size at younger ages. The present analysis is concerned with survey indices of juveniles up to the youngest age where stock estimates, based on time-series analysis of catch-at-age data, are available. A stock estimate at that age from catch-at-age data is also included. A common model of the relationship between stock size and survey indices is combined with the model describing the decline of a stock by natural mortality. Random variations in natural mortality are defined separately from sampling variations and irregular catchability in the survey. The stock size and magnitudes of the random variations are estimated by the Kalman filter, which also provides predictions of future recruitment to the catchable stock. Analysis of observations of Icelandic cod reveals a large deviation from proportionality in the relationship between the index and the stock estimates in the youngest ages, but haddock data are compatible with proportionality. Variations in natural mortality during the second to fourth year of cod and the second to third year of haddock are not a major factor in variations of stock size.

Morphometry and Gonad Maturity of Male Snow Crab, Chionoecetes opilio

1992 ◽  
Vol 49 (12) ◽  
pp. 2460-2468 ◽  
Author(s):  
Michel Comeau ◽  
Gérard Y. Conan
Keyword(s):  
Carapace Width ◽  
Immature Stage ◽  
Juvenile Stage ◽  
Snow Crab ◽  
Sexual Character ◽  
Gonad Maturity ◽  
Chionoecetes Opilio ◽  
Juvenile Males ◽  
The Relationship ◽  
Determinant Factor

The relationship between chela height (CH) and carapace width (CW) of male snow crab, Chionoecetes opilio, goes through three allometric stages. The "immature stage" (mostly < 34 mm CW) evolves into a "juvenile stage" (34–120 mm CW) through a "juvenile molt" defining a change in allometry marked by an angular point around 34 mm CW. Fifty percent of males reach gonad maturity, defined by the presence of spermatophores inside the vasa deferentia, at an estimated size of 34 mm CW) The third allometric stage, "morphometrically mature," is separated from the juvenile stage by a "molt to morphometric maturity" at sizes ranging from 50 to 120 mm CW. Juvenile males have smaller claws than morphometrically mature males of the same size. This secondary sexual character is justified by a specific behavior of the males holding the pereipods of the female in one chela during precopulatory embrace. Male snow crab efficiently mate in nature with intermolt multiparous females only after reaching morphometric maturity. Therefore, the presence of spermatophores is not the sole determinant factor necessary for male copulation. Juvenile males larger than the minimum legal size of 95 mm CW are harvestable before, they may efficiently mate.

Maturity and Molt Status of Crustacea: Determining Classification without Prior Criteria

1994 ◽  
Vol 51 (2) ◽  
pp. 408-416 ◽  
Author(s):  
William G. Warren
Keyword(s):  
Iterative Procedure ◽  
A Priori ◽  
Carapace Width ◽  
Snow Crab ◽  
Data Sets ◽  
Chionoecetes Opilio ◽  
Relationship Of ◽  
The Relationship

Existing methodology for estimation is reviewed for the situation where, a priori, the existence of two or more groups can be postulated but, in contrast with discriminant analysis, there is no sample in which the correct categories are known. Such mixture models are applied to two data sets related to the maturity and molt status of snow crab, Chionoecetes opilio, namely (1) the classification of crab as morphometrically mature or immature on the basis of the chela height – carapace width relationship and (2) the determination of the number of molts of crab, during a known period at liberty, from the relationship of size at release and size at recapture of tagged animals, in the latter example, a theoretical constraint is imposed that links the relationships at the different stages. The solution is obtained by "nesting" an iterative procedure within an EM algorithm. The method permits hypotheses concerning the number of groups to be tested, including the hypothesis that the data come from a single homogenous group, and each individual is assigned a probability of belonging to a group.

scholarly journals Estimating natural mortality and egg production of snow crab Chionoecetes opilio adult females

2013 ◽  
Vol 18 (3) ◽  
pp. 261-270 ◽  
Author(s):  
H Drouineau ◽  
B Sainte-Marie ◽  
D Duplisea
Keyword(s):  
Egg Production ◽  
Snow Crab ◽  
Natural Mortality ◽  
Chionoecetes Opilio ◽  
Adult Females

scholarly journals Estimating maximum sustainable yield of snow crab (Chionoecetes opilio) off Tohoku Japan via a state-space assessment model with time-varying natural mortality

2020 ◽  
Author(s):  
Yasutoki Shibata ◽  
Jiro Nagao ◽  
Yoji Narimatsu ◽  
Eisuke Morikawa ◽  
Yuto Suzuki ◽  
...  
Keyword(s):  
State Space ◽  
Maximum Sustainable Yield ◽  
Biological Characteristics ◽  
Assessment Model ◽  
Fish Stock ◽  
Snow Crab ◽  
Sustainable Yield ◽  
Natural Mortality ◽  
Time Varying ◽  
Chionoecetes Opilio

AbstractYield from fisheries is a tangible benefit of ecosystem services and sustaining or restoring a fish stock level to achieve a maximum sustainable yield (MSY). Snow crab (Chionoecetes opilio) off Tohoku has been managed by a total allowable catch since 1996, although their abundance has not increased even after 2011, when fishing pressure rapidly decreased because of the Great East Japan Earthquake. This implies that their biological characteristics, such as recruits, natural mortality coefficient (M), and terminal molting probabilities (p), might have changed. We developed “just another state-space stock assessment model (JASAM)” to estimate the MSY of the snow crab off Tohoku, Japan, considering interannual variations in M and p. The multi-model inference revealed that M increased from 0.2 in 1997 to 0.59 in 2018, although it was not different among the instars, sex, nor terminal molt of crabs. The parameter p also increased by 1.34–2.46 times depending on the instar growth stages from 1997 to 2018. We estimated the MSYs in three scenarios, which drastically changed if M and p were set as they were in the past or at the current values estimated from this study. This result indicated that the MSY of snow crab would also be time-varying based on their time-varying biological characteristics.

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