scholarly journals Conservation risks and portfolio effects in mixed‐stock fisheries

2021 ◽  
Author(s):  
Jonathan W. Moore ◽  
Brendan M. Connors ◽  
Emma E. Hodgson
Keyword(s):  
Mixed Stock

scholarly journals Genetic mixed-stock analysis disentangles spatial and temporal variation in composition of the West Greenland Atlantic Salmon fishery

2016 ◽  
Vol 73 (9) ◽  
pp. 2311-2321 ◽  
Author(s):  
Ian R. Bradbury ◽  
Lorraine C. Hamilton ◽  
Timothy F. Sheehan ◽  
Gerald Chaput ◽  
Martha J. Robertson ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
North American ◽  
Temporal Stability ◽  
Spatial And Temporal Variation ◽  
Published Data ◽  
The West ◽  
West Greenland ◽  
Archived Samples ◽  
Mixed Stock ◽  
Salmon Fishery

Abstract The West Greenland Atlantic Salmon (Salmo salar) fishery represents the largest remaining mixed-stock fishery for Atlantic Salmon in the Northwest Atlantic and targets multi-sea-winter (MSW) salmon from throughout North America and Europe. We evaluated stock composition of salmon harvested in the waters off West Greenland (n = 5684 individuals) using genetic mixture analysis and individual assignment to inform conservation of North American populations, many of which are failing to meet management targets. Regional contributions to this fishery were estimated using 2169 individuals sampled throughout the fishery between 2011 and 2014. Of these, 22% were identified as European in origin. Major North American contributions were detected from Labrador (∼20%), the Southern Gulf/Cape Breton (29%), and the Gaspe Peninsula (29%). Minor contributions (∼5%) were detected from Newfoundland, Ungava, and Quebec regions. Region-specific catches were extrapolated using estimates of composition and fishery catch logs and harvests ranged from 300 to 600 and 2000 to 3000 individuals for minor and major constituents, respectively. To evaluate the temporal stability of the observed fishery composition, we extended the temporal coverage through the inclusion of previously published data (1995–2006, n = 3095) and data from archived scales (1968–1998, n = 420). Examination of the complete time-series (47 years) suggests relative stability in stock proportions since the late 1980s. Genetic estimates of stock composition were significantly associated with model-based estimates of returning MSW salmon (individual years r = 0.69, and overall mean r = 0.96). This work demonstrates that the analysis of both contemporary and archived samples in a mixed-stock context can disentangle levels of regional exploitation and directly inform assessment and conservation of Atlantic Salmon in the West Greenland interceptory Atlantic Salmon fishery.

scholarly journals Modeling the implications of stock mixing and life history uncertainty of Atlantic bluefin tuna

2017 ◽  
Vol 74 (11) ◽  
pp. 1990-2004 ◽  
Author(s):  
Lisa A. Kerr ◽  
Steven X. Cadrin ◽  
David H. Secor ◽  
Nathan G. Taylor
Keyword(s):  
Temporal Distribution ◽  
Bluefin Tuna ◽  
Analytical Framework ◽  
Magnitude Distribution ◽  
Atlantic Bluefin Tuna ◽  
Age Structured ◽  
Stock Mixing ◽  
Overlap Model ◽  
Mixed Stock ◽  
Central Atlantic

Atlantic bluefin tuna (Thunnus thynnus) is currently managed as two separate eastern and western stocks, despite information indicating considerable stock mixing. Using a simulation model, we explored how scenarios of population-specific migration and uncertainty in aspects of bluefin tuna biology affect the magnitude, distribution, and mixed stock nature of the resource and catch of its associated fisheries. The analytical framework was a stochastic, age-structured, stock-overlap model that was seasonally and spatially explicit with movement of eastern- and western-origin tuna informed by tagging and otolith chemistry data. Alternate estimates of movement and assumptions regarding maturity and recruitment regime for western-origin fish were considered. Simulation of the operating model indicated considerable stock mixing in the western and central Atlantic, which resulted in differences between the stock and population view of western bluefin tuna. The relative biomass of the western population and its spatial and temporal distribution in the Atlantic was sensitive to model assumptions and configurations. Simulation modeling can provide a means to ascertain the potential consequences of stock mixing on the assessment and management of fishery resources.

scholarly journals Population structure of eulachon Thaleichthys pacificus from Northern California to Alaska using single nucleotide polymorphisms from direct amplicon sequencing

2020 ◽  
Author(s):  
Ben J. G. Sutherland ◽  
John Candy ◽  
Kayla Mohns ◽  
Olivia Cornies ◽  
Kim Jonsen ◽  
...  
Keyword(s):  
Gulf Of Alaska ◽  
Amplicon Sequencing ◽  
Fraser River ◽  
Northern California ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Southeast Alaska ◽  
Southern Us ◽  
Mixed Stock ◽  
Future Work

ABSTRACTEulachon Thaleichthys pacificus, a culturally and ecologically important anadromous smelt (Family Osmeridae), ranges from Northern California to the southeast Bering Sea. In recent decades, some populations have experienced declines. Here we use a contig-level genome assembly combined with previously published RADseq-derived markers to construct an amplicon panel for eulachon. Using this panel, we develop a filtered genetic baseline of 521 variant loci genotyped in 1,989 individuals from 14 populations ranging from Northern California through Central Alaska. Consistent with prior genetic studies, the strongest separation occurs among three main regions: from Northern California up to and including the Fraser River; north of the Fraser River to southeast Alaska; and within the Gulf of Alaska. Separating the Fraser River from southern US populations, and refining additional substructure within the central coast may be possible in mixed-stock analysis; this will be addressed in future work. The amplicon panel outperformed the previous microsatellite panel, and thus will be used in future mixed-stock analyses of eulachon in order to provide new insights for management and conservation of eulachon.

scholarly journals Importance of sample size for estimating prevalence: A case example of infectious hematopoietic necrosis viral RNA detection in mixed-stock Fraser River Sockeye salmon (Oncorhynchus nerka), British Columbia, Canada.

2020 ◽  
Author(s):  
Emilie Laurin ◽  
Julia Bradshaw ◽  
Laura Hawley ◽  
Ian A. Gardner ◽  
Kyle A Garver ◽  
...  
Keyword(s):  
British Columbia ◽  
Sample Size ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Small Sample ◽  
Viral Rna ◽  
Sample Sizes ◽  
Apparent Prevalence ◽  
Infectious Hematopoietic Necrosis ◽  
Mixed Stock

Proper sample size must be considered when designing infectious-agent prevalence studies for mixed-stock fisheries, because bias and uncertainty complicate interpretation of apparent (test)-prevalence estimates. Sample size varies between stocks, often smaller than expected during wild-salmonid surveys. Our case example of 2010-2016 survey data of Sockeye salmon (Oncorhynchus nerka) from different stocks of origin in British Columbia, Canada, illustrated the effect of sample size on apparent-prevalence interpretation. Molecular testing (viral RNA RT-qPCR) for infectious hematopoietic necrosis virus (IHNv) revealed large differences in apparent-prevalence across wild salmon stocks (much higher from Chilko Lake) and sampling location (freshwater or marine), indicating differences in both stock and host life-stage effects. Ten of the 13 marine non-Chilko stock-years with IHNv-positive results had small sample sizes (< 30 samples per stock-year) which, with imperfect diagnostic tests (particularly lower diagnostic sensitivity), could lead to inaccurate apparent-prevalence estimation. When calculating sample size for expected apparent prevalence using different approaches, smaller sample sizes often led to decreased confidence in apparent-prevalence results and decreased power to detect a true difference from a reference value.

Open Higher Order Continuous-Time Dynamic Model with Mixed Stock and Flow Data and Derivatives of Exogenous Variables

1991 ◽  
Vol 7 (3) ◽  
pp. 404-408 ◽  
Author(s):  
K. Ben Nowman
Keyword(s):  
Continuous Time ◽  
Higher Order ◽  
Flow Data ◽  
Continuous Time Model ◽  
Exogenous Variables ◽  
Time Model ◽  
Time Dynamic ◽  
Mixed Stock ◽  
Gaussian Estimation ◽  
Derivatives Of

This paper is concerned with deriving formulae for higher order derivatives of exogenous variables for use in estimating the parameters of an open secondorder continuous time model with mixed stock and flow data and first and second order derivatives of exogenous variables which are not observable. This should provide the basis for the future estimation of continuous time models in a range of applied areas using the new Gaussian estimation computer program developed by Nowman [4].

Genetic population structure and tools for the management of European sprat (Sprattus sprattus)

2020 ◽  
Vol 77 (6) ◽  
pp. 2134-2143
Author(s):  
Niall J McKeown ◽  
Piera Carpi ◽  
Joana F Silva ◽  
Amy J E Healey ◽  
Paul W Shaw ◽  
...  
Keyword(s):  
Local Adaptation ◽  
Population Connectivity ◽  
Ne Atlantic ◽  
Genetic Population ◽  
Sprattus Sprattus ◽  
Population Average ◽  
Outlier Loci ◽  
Baltic Population ◽  
Assisted Management ◽  
Mixed Stock

Abstract This study used RAD-seq-derived SNPs to explore population connectivity, local adaptation, and individual assignment in European sprat (Sprattus sprattus) and inform the alignment of management units with biological processes. FST, clustering, and outlier analyses support a genetically cohesive population spanning the Celtic Sea-English Channel-North Sea-Kattegat (NE Atlantic) region. The lack of structure among the NE Atlantic samples indicates connectivity across current management boundaries. However, the assumption of demographic panmixia is cautioned against unless verified by a multidisciplinary approach. The data confirm high genetic divergence of a Baltic population (average FST vs. NE Atlantic samples = 0.051) with signatures compatible with local adaptation in the form of outlier loci, some of which are shown to occur within exonic regions. The outliers permit diagnostic assignment of individuals between the NE Atlantic and Baltic populations and thus represent a “reduced panel” of markers for monitoring a potential mixed stock fishery within the western Baltic. Overall, this study provides information that may help refine spatial management boundaries of sprat and resources for genetic-assisted management.

scholarly journals Evaluation of methods for spawner–recruit analysis in mixed-stock Pacific salmon fisheries

2020 ◽  
Vol 77 (7) ◽  
pp. 1149-1162 ◽  
Author(s):  
Benjamin A. Staton ◽  
Matthew J. Catalano ◽  
Brendan M. Connors ◽  
Lewis G. Coggins ◽  
Michael L. Jones ◽  
...  
Keyword(s):  
State Space ◽  
Oncorhynchus Tshawytscha ◽  
Pacific Salmon ◽  
State Space Model ◽  
Reference Points ◽  
State Space Models ◽  
Space Model ◽  
Trade Offs ◽  
Salmon Fisheries ◽  
Mixed Stock

Salmon populations harvested in mixed-stock fisheries can exhibit genotypic, behavioral, and life history diversity that can lead to heterogeneity in population productivity and size. Methods to quantify this heterogeneity among populations in mixed-stock fisheries are not well-established but are critical to assessing harvest–biodiversity trade-offs when setting harvest policies. We developed an integrated, age-structured, state-space model that allows for more complete use of available data and sharing of information than simpler methods. We compared a suite of state-space models of varying structural complexity to simpler regression-based approaches and, as an example case, fitted them to data from 13 Chinook salmon (Oncorhynchus tshawytscha) populations in the Kuskokwim drainage in western Alaska. We found biological and policy conclusions were largely consistent among state-space models but differed strongly from regression-based approaches. Simulation trials illustrated our state-space models were largely unbiased with respect to spawner–recruit parameters, abundance states, and derived biological reference points, whereas the regression-based approaches showed substantial bias. These findings suggest our state-space model shows promise for informing harvest policy evaluations of harvest–biodiversity trade-offs in mixed-stock salmon fisheries.

scholarly journals Mixed-stock analyses of migratory, non-native Chinook salmon at sea and assignment to natal sites in fresh water at their introduced range in South America

2020 ◽  
Vol 22 (11) ◽  
pp. 3175-3182
Author(s):  
Selim S. Musleh ◽  
Lisa W. Seeb ◽  
James E. Seeb ◽  
Billy Ernst ◽  
Sergio Neira ◽  
...  
Keyword(s):  
South America ◽  
Fresh Water ◽  
Chinook Salmon ◽  
Introduced Range ◽  
Mixed Stock ◽  
Mixed Stock Analyses
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