scholarly journals Predicting habitat to optimize sampling of Pacific sardine (Sardinops sagax)

2011 ◽  
Vol 68 (5) ◽  
pp. 867-879 ◽  
Author(s):  
Juan P. Zwolinski ◽  
Robert L. Emmett ◽  
David A. Demer
Keyword(s):  
Egg Production ◽  
Additive Model ◽  
Production Method ◽  
The United States ◽  
Seasonal Migration ◽  
Sea Surface ◽  
Sampling Effort ◽  
Potential Habitat ◽  
Pacific Sardine ◽  
Sardinops Sagax

Abstract Zwolinski, J. P., Emmett, R. L., and Demer, D. A. 2011. Predicting habitat to optimize sampling of Pacific sardine (Sardinops sagax). – ICES Journal of Marine Science, 68: 867–879. More than 40 years after the collapse of the fishery for Pacific sardine, a renewed fishery has emerged off the west coasts of the United States and Canada. The daily egg production method (DEPM) and acoustic-trawl surveys are performed annually and, to minimize the uncertainties in the estimates, sampling effort needs to be allocated optimally. Here, based on a 12-year dataset including the presence/absence of sardine eggs and concomitant remotely sensed oceanographic variables, a probabilistic generalized additive model is developed to predict spatio-temporal distributions of habitat for the northern stock of Pacific sardine in the California Current. Significant relationships are identified between eggs and sea surface temperature, chlorophyll a concentration, and the gradient of sea surface altitude. The model accurately predicts the habitat and seasonal migration pattern of sardine, irrespective of spawning condition. The predictions of potential habitat are validated extensively by fishery landings and net-sample data from the northeast Pacific. The predicted habitat can be used to optimize the time and location of the DEPM, acoustic-trawl, and aerial surveys of sardine. The method developed and illustrated may be applicable too to studies of other stocks of sardine and other epipelagic fish in other eastern boundary, upwelling regions.

scholarly journals Corroboration and refinement of a method for differentiating landings from two stocks of Pacific sardine (Sardinops sagax) in the California Current

2013 ◽  
Vol 71 (2) ◽  
pp. 328-335 ◽  
Author(s):  
David A. Demer ◽  
Juan P. Zwolinski
Keyword(s):  
California Current ◽  
Practical Method ◽  
Potential Habitat ◽  
Point Conception ◽  
Stock Biomass ◽  
Habitat Transition ◽  
Good Potential ◽  
Pacific Sardine ◽  
Sardinops Sagax ◽  
Spatio Temporal

Abstract Demer, D. A., and Zwolinski, J. P. 2014. Corroboration and refinement of a method for differentiating landings from two stocks of Pacific sardine (Sardinops sagax) in the California Current. – ICES Journal of Marine Science, 71: 328–335. Efforts to survey, assess and manage Pacific sardine (Sardinops sagax) in the California Current may depend on accurate differentiation of the purported two migrating stocks. The southern stock spans seasonally from southern Baja California, México to Point Conception, California; the northern stock spans seasonally from Punta Eugenia, México northwards to southern Alaska. Their seasonal north–south migrations are approximately synchronous within their respective domains, resulting in segregated spawning and different identities. A decade ago, a practical method was proposed for differentiating landings from the two stocks using concomitant measurements of sea-surface temperature (SST). Here, we corroborate and refine the method using regional indices of optimal and good potential habitat for the northern stock, and SST-based indices associated with the 99.9 and 100% confidence intervals of the potential habitat. For months when the index is <0.5, (i.e. when the minority of a fishing region probably includes potential northern stock habitat), the landings are attributed to the southern stock, and vice versa. We applied this method to regional monthly landings data from 2006–2011 and the results indicated that an average of 63–72 and 32–36% of the summertime landings at Ensenada, México and San Pedro, southern California were probably from the southern stock, respectively, depending on the index used. Allocation error could be reduced if the landings were evaluated on finer spatio-temporal scales, particularly during habitat-transition periods. Our method may be used to improve estimates of northern stock biomass, spatial and length distributions, recruitment, and mortality.

Use of the daily egg production method to estimate the stock size of Western Australian sardines (Sardinops sagax)

1996 ◽  
Vol 47 (6) ◽  
pp. 819 ◽  
Author(s):  
WJ Fletcher ◽  
NCH Lo ◽  
EA Hayes ◽  
RJ Tregonning ◽  
SJ Blight
Keyword(s):  
Western Australia ◽  
Egg Production ◽  
Production Method ◽  
Purse Seine ◽  
Batch Fecundity ◽  
Stock Size ◽  
Production Values ◽  
Sardinops Sagax ◽  
Western Australian ◽  
Spawning Biomass

The daily egg production method was used to estimate the spawning biomass of the sardine Sardinops sagax in the Albany region of Western Australia. Plankton surveys covering 10000 - 14000 km² were completed in July of 1991 and 1992 in three to five days using up to three boats. Adult sardines were obtained from the local purse-seine fleet. The spawning area was similar in both years at approximately 3800 km² (1100 nmile²), but the number of eggs collected was larger in 1991 with egg production values of 6.5 per 0.05 m2 day-1 compared with 3.9 per 0.05 m2 day-1 in 1992. The average batch fecundity values were similar (approximately 11000 eggs female-1) as were the proportions spawning (0.13 in 1991; 0.09 in 1992). The calculated biomass estimates were 23 121 t (CV = 0.51) and 16 121 t (CV = 0.44) in 1991 and 1992 respectively.

scholarly journals Sampling selectivity in acoustic-trawl surveys of Pacific sardine (Sardinops sagax) biomass and length distribution†

2013 ◽  
Vol 70 (7) ◽  
pp. 1369-1377 ◽  
Author(s):  
David A. Demer ◽  
Juan P. Zwolinski ◽  
George R. Cutter ◽  
Kyle A. Byers ◽  
Beverly J. Macewicz ◽  
...  
Keyword(s):  
Egg Production ◽  
Survey Methods ◽  
Length Distribution ◽  
Small Fish ◽  
Survey Results ◽  
Pacific Sardine ◽  
Sardinops Sagax ◽  
Age Structured ◽  
Harvest Quotas ◽  
Trawl Surveys

Abstract Demer, D. A., Zwolinski, J. P., Cutter, G. R. Jr, Byers, K. A., Macewicz, B. J., and Hill, K. T. Sampling selectivity in acoustic-trawl surveys of Pacific sardine (Sardinops sagax) biomass and length distribution. – ICES Journal of Marine Science, 70: . To annually assess the northern stock of Pacific sardine (Sardinops sagax) in the California Current and set harvest quotas for the US fishery, managers have used an age-structured stock synthesis model fitted with results from acoustic-trawl (ATM), daily-egg-production, and aerial-photogrammetric survey methods, fishery landing and individual-length data, and many assumed or empirically derived parameters. In these assessments, sardine landed at ports spanning from Ensenada, México to Vancouver Island, Canada were assumed to be solely from the northern stock. It was also assumed that the ATM estimates of sardine biomass were negligibly biased for the sizes of fish sampled by the survey trawls (i.e., catchability q = 1 for sardine standard length (SL) values greater than ∼17 cm). Due to these catchability and length-selectivity assumptions, the ATM- and assessment-estimated abundances are mostly similar for larger sardine. However, the assessment estimates include large abundances of small sardine (SL values less than ∼15 cm) that are not represented in either the ATM-survey results or the fishery landings, and generally did not recruit to the migrating northern stock sampled by the ATM surveys. We considered four explanations for this disparity: (i) the ATM length-selectivity assumption is correct; (ii) the non-recruiting small fish may comprise a smaller portion of the stock than indicated by the assessments; (iii) during years of low recruitment success, those size classes may be virtually completely fished by the Ensenada and San Pedro fisheries; or (iv) they may belong to the southern sardine stock. This investigation emphasizes the previously identified importance of differentiating samples from the northern and southern stocks and surveying their entire domains.

scholarly journals Measurements of natural mortality for Pacific sardine (Sardinops sagax)

2013 ◽  
Vol 70 (7) ◽  
pp. 1408-1415 ◽  
Author(s):  
Juan P. Zwolinski ◽  
David A. Demer
Keyword(s):  
United States ◽  
California Current ◽  
The United States ◽  
Assessment Model ◽  
Entire Period ◽  
Natural Mortality ◽  
Pacific Sardine ◽  
The Mean ◽  
Sardinops Sagax ◽  
The One

Abstract Zwolinski, J. P., and Demer, D. A. 2013. Measurements of natural mortality for Pacific sardine (Sardinops sagax). – ICES Journal of Marine Science, 70: . The northern stock of Pacific sardine (Sardinops sagax) in the California Current Ecosystem is periodically assessed to provide harvest guidelines for the United States and Canadian fisheries. The assessment model incorporates the estimates of abundance from acoustic-trawl method (ATM) and other surveys and many parameters including a constant value for the instantaneous natural mortality coefficient (M). Here, the ATM-estimated length-structured sardine abundances for 2006–2011 are combined to directly estimate M. The stock was dominated by the 2003, 2004, and 2005 year classes (2003–2005 cohort) from 2006 to 2010 and by the 2009 and 2010 year classes in 2011. Insignificant recruitments during 2006–2010 allowed the 2003–2005 cohort to be tracked and M to be estimated. The bootstrap distributions of estimated M encompass the assessment-assumed value of 0.4−year. The measurements suggest that M is high for a new cohort, declines during mid-life, then increases as the fish approach their longevity. The mean M for the entire period, 0.52, is 30% higher than the one currently assumed for the assessment, reflecting the steeper decline in the ATM-estimated biomass versus that in the assessment model.

Eviction and Voter Turnout: The Political Consequences of Housing Instability

2021 ◽  
pp. 003232922110507
Author(s):  
Gillian Slee ◽  
Matthew Desmond
Keyword(s):  
Voter Turnout ◽  
Causal Effect ◽  
Additive Model ◽  
The United States ◽  
Data Set ◽  
Endogeneity Bias ◽  
Political Consequences ◽  
Housing Costs ◽  
Election Results ◽  
The Impact

In recent years, housing costs have outpaced incomes in the United States, resulting in millions of eviction filings each year. Yet no study has examined the link between eviction and voting. Drawing on a novel data set that combines tens of millions of eviction and voting records, this article finds that residential eviction rates negatively impacted voter turnout during the 2016 presidential election. Results from a generalized additive model show eviction’s effect on voter turnout to be strongest in neighborhoods with relatively low rates of displacement. To address endogeneity bias and estimate the causal effect of eviction on voting, the analysis treats commercial evictions as an instrument for residential evictions, finding that increases in neighborhood eviction rates led to substantial declines in voter turnout. This study demonstrates that the impact of eviction reverberates far beyond housing loss, affecting democratic participation.

Spatiotemporal modelling for the annual egg production method of stock assessment using generalized additive models

1998 ◽  
Vol 55 (12) ◽  
pp. 2608-2621 ◽  
Author(s):  
N H Augustin ◽  
D L Borchers ◽  
E D Clarke ◽  
S T Buckland ◽  
M Walsh
Keyword(s):  
Environmental Variables ◽  
Egg Production ◽  
Survey Design ◽  
Stock Assessment ◽  
Generalized Additive Models ◽  
Production Method ◽  
Additive Models ◽  
Atlantic Mackerel ◽  
Egg Density ◽  
Survey Designs

Generalized additive models (GAMs) are used to model the spatiotemporal distribution of egg density as a function of locational and environmental variables. The main aim of using GAMs is to improve precision of egg abundance estimates needed for the annual egg production method. The application of GAMs requires a survey design with good coverage in space and time. If the only results available are from less optimal survey designs, they can be improved by using historical data for spawning boundaries. The method is applied to plankton egg survey data of Atlantic mackerel (Scomber scombrus) in 1995. The GAM-based method improves the precision of estimates substantially and is also useful in explaining complex space-time trends using environmental variables.

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