An age- and sex-structured assessment model for American eels (Anguilla rostrata) in the Potomac River, Maryland

2011 ◽  
Vol 68 (6) ◽  
pp. 1024-1037 ◽  
Author(s):  
Kari H. Fenske ◽  
Michael J. Wilberg ◽  
David H. Secor ◽  
Mary C. Fabrizio
Keyword(s):  
Large Scale ◽  
Assessment Model ◽  
Anguilla Rostrata ◽  
European Eel ◽  
Natural Mortality ◽  
Potomac River ◽  
Fishing Mortality ◽  
Catch Per Unit Effort ◽  
American Eel ◽  
Age And Sex

American eel ( Anguilla rostrata ) and European eel ( Anguilla anguilla ) populations have declined since the 1980s prompting concern about their status and the causes of decline, but stock assessment approaches to estimate effects of fishing on these populations are lacking. Since 1964, 16% of United States commercial American eel harvest came from the Potomac River, yet American eel abundance, production, and fishing mortality is poorly understood in this system. We developed an age- and sex-structured assessment model for 1980–2008 and compared results with the F50% biological reference point (BRP). The model included natural mortality, fishing mortality, and sex- and age-specific maturation mortality and selectivity. Between 1980 and 2008 estimated recruitment, biomass, and abundance decreased 82%–89%. In all years since 1993, the exploitation rate exceeded the F50% BRP. The model was moderately sensitive to changes in natural mortality, standard deviation for fishery and recruitment catch-per-unit-effort indices, and initial fishing mortality. The multidecadal decline in recruitment in Chesapeake eels matches those reported elsewhere for American and European eels, suggesting large-scale processes have affected anguillid eel recruitment in the North Atlantic.

Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
Curve Analysis ◽  
Anguilla Rostrata ◽  
Natural Mortality ◽  
Von Bertalanffy ◽  
Commercial Fishery ◽  
Disappearance Rate ◽  
Fishing Mortality ◽  
Catch Per Unit Effort ◽  
American Eels ◽  
Yield Per Recruit

<em>Abstract.—</em>American eels <em>Anguilla rostrata </em>were fourth in landings and third in value in the Delaware commercial finfish fisheries from 1999 to 2002. Landings and effort dropped while catch per unit effort (CPUE) varied during the period. Bait eel landings decreased more than food eel landings. The number of licensed eelers in Delaware dropped from 121 in 1997 to 77 in 2002. American eels collected from the commercial fishery ranged in length from 216 to 838 mm (mean 427 ± 133 SD), in weight from 13.6 to 820 g (mean 205 ± 205 SD), and in age from 2 to 12 years (mean 5 ± 2 SD). The length–weight relationship was <EM>W </EM>= 0.00000065 × <EM>L</EM><sup>3.18</sup>. Von Bertalanffy length-at-age parameters calculated from the sampled eels were <EM>L</EM> = 547, <em>k </em>= 0.43, and <em>t</em><sub>0</sub> = 0.38. Linearized catch curve analysis indicated an instantaneous disappearance rate of 0.59. The estimate of natural mortality (<EM>M</EM>) was 0.25, giving a fishing mortality (<EM>F</EM>) of 0.34. Yield-per-recruit analysis suggested that overfishing may be occurring in Delaware’s commercial American eel fishery.

scholarly journals SPAM (Sex-Structured Pandalus Assessment Model): a stock assessment model for Pandalus stocks

2012 ◽  
Vol 69 (4) ◽  
pp. 770-783 ◽  
Author(s):  
Hilaire Drouineau ◽  
Louise Savard ◽  
Mathieu Desgagnés ◽  
Daniel Duplisea
Keyword(s):  
Stock Assessment ◽  
Sex Change ◽  
Assessment Model ◽  
Natural Mortality ◽  
The Novel ◽  
Fishing Mortality ◽  
Novel Structure ◽  
Shrimp Fisheries ◽  
Analytical Tools ◽  
Mortality Estimates

Despite the economic importance of Pandalus shrimp fisheries, few analytical tools have been developed to assess their stocks, and traditional stock assessment models are not appropriate because of biological specificities of Pandalus species. In this context, we propose SPAM (Sex-Structured Pandalus Assessment Model), a model dedicated to protandric hermaphrodite pandalids stock assessment. Pandalids are difficult to assess because the cues affecting sex change, size at recruitment, and mortality variability are not well understood or characterized. The novel structure of the model makes it possible to adequately describe variability in natural mortality by stage and in time, as well as variability in size at sex change and recruitment. The model provides traditional stock assessment outputs, such as fishing mortality estimates and numbers of individuals, and provides in addition yearly natural mortality estimates. The model is applied to the exploited shrimp stock of Pandalus borealis in Sept-Îles (Québec, Canada) as an illustrative example of the utility of the approach.

Age and growth of the American eel (Anguilla rostrata (LeSueur)) in Newfoundland waters

1971 ◽  
Vol 49 (1) ◽  
pp. 121-128 ◽  
Author(s):  
R. W. Gray ◽  
C. W. Andrews
Keyword(s):  
Age Groups ◽  
Anguilla Anguilla ◽  
Age And Growth ◽  
Anguilla Rostrata ◽  
European Eel ◽  
Silver Eel ◽  
American Eel ◽  
Brackish Waters ◽  
American Eels ◽  
Freshwater Eels

The age (otolith readings) and growth of American eels (Anguilla rostrata (LeSueur)) from fresh and brackish waters in Newfoundland were studied. The eels in Burnt Berry Brook grew faster than eels in the other areas. The growth of young eels in brackish water was slow. Although the growth of these eels increased in subsequent age groups, freshwater eels were consistently larger at each age.The silver eel migrates after spending 12 to 13 years in Newfoundland waters. The American eel in Newfoundland is generally larger than the European eel (Anguilla anguilla L.) at the onset of migration; however, its appearance and state of maturity parallel the condition described in the European eel.

A comparison of metal concentrations in the tissues of yellow American eel (Anguilla rostrata) and European eel (Anguilla anguilla)

2016 ◽  
Vol 569-570 ◽  
pp. 1435-1445 ◽  
Author(s):  
Pauline Pannetier ◽  
Antoine Caron ◽  
Peter G.C. Campbell ◽  
Fabien Pierron ◽  
Magalie Baudrimont ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
Anguilla Rostrata ◽  
European Eel ◽  
American Eel ◽  
Metal Concentrations

Relating American Eel Anguilla rostrata abundance to environmental DNA concentration in the Bronx River

2021 ◽  
Author(s):  
Sam C. Chin ◽  
John Waldman ◽  
Mike Bednarski ◽  
Merry Camhi ◽  
Jake LaBelle ◽  
...  
Keyword(s):  
Environmental Dna ◽  
Anguilla Rostrata ◽  
American Eel ◽  
Dna Concentration ◽  
Bronx River

scholarly journals Joint regression and learning from pairwise rankings for personalized image aesthetic assessment

2021 ◽  
Author(s):  
Jin Zhou ◽  
Qing Zhang ◽  
Jian-Hao Fan ◽  
Wei Sun ◽  
Wei-Shi Zheng
Keyword(s):  
Large Scale ◽  
Assessment Model ◽  
Generic Model ◽  
Small Subset ◽  
Deep Convolutional Neural Networks ◽  
Personal Taste ◽  
Hinge Loss ◽  
Novel Approach ◽  
Large Scale Dataset ◽  
Image Pairs

AbstractRecent image aesthetic assessment methods have achieved remarkable progress due to the emergence of deep convolutional neural networks (CNNs). However, these methods focus primarily on predicting generally perceived preference of an image, making them usually have limited practicability, since each user may have completely different preferences for the same image. To address this problem, this paper presents a novel approach for predicting personalized image aesthetics that fit an individual user’s personal taste. We achieve this in a coarse to fine manner, by joint regression and learning from pairwise rankings. Specifically, we first collect a small subset of personal images from a user and invite him/her to rank the preference of some randomly sampled image pairs. We then search for the K-nearest neighbors of the personal images within a large-scale dataset labeled with average human aesthetic scores, and use these images as well as the associated scores to train a generic aesthetic assessment model by CNN-based regression. Next, we fine-tune the generic model to accommodate the personal preference by training over the rankings with a pairwise hinge loss. Experiments demonstrate that our method can effectively learn personalized image aesthetic preferences, clearly outperforming state-of-the-art methods. Moreover, we show that the learned personalized image aesthetic benefits a wide variety of applications.

scholarly journals Spatio-temporal associations of albacore CPUEs in the Northeastern Pacific with regional SST and climate environmental variables

2014 ◽  
Vol 71 (7) ◽  
pp. 1717-1727 ◽  
Author(s):  
A. Jason Phillips ◽  
Lorenzo Ciannelli ◽  
Richard D. Brodeur ◽  
William G. Pearcy ◽  
John Childers
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Environmental Variability ◽  
Southern Oscillation ◽  
Spatial Dynamics ◽  
Catch Per Unit Effort ◽  
Variable Effect ◽  
Positive Effects ◽  
The North ◽  
Additive Mixed Models

Abstract This study investigated the spatial distribution of juvenile North Pacific albacore (Thunnus alalunga) in relation to local environmental variability [i.e. sea surface temperature (SST)], and two large-scale indices of climate variability, [the Pacific Decadal Oscillation (PDO) and the Multivariate El Niño/Southern Oscillation Index (MEI)]. Changes in local and climate variables were correlated with 48 years of albacore troll catch per unit effort (CPUE) in 1° latitude/longitude cells, using threshold Generalized Additive Mixed Models (tGAMMs). Model terms were included to account for non-stationary and spatially variable effects of the intervening covariates on albacore CPUE. Results indicate that SST had a positive and spatially variable effect on albacore CPUE, with increasingly positive effects to the North, while PDO had an overall negative effect. Although albacore CPUE increased with SST both before and after a threshold year of 1986, such effect geographically shifted north after 1986. This is the first study to demonstrate the non-stationary spatial dynamics of albacore tuna, linked with a major shift of the North Pacific. Results imply that if ocean temperatures continue to increase, US west coast fisher communities reliant on commercial albacore fisheries are likely to be negatively affected in the southern areas but positively affected in the northern areas, where current albacore landings are highest.

scholarly journals Depleted marine fish stocks and ecosystem-based management: on the road to recovery, we need to be precautionary

2010 ◽  
Vol 68 (1) ◽  
pp. 212-220 ◽  
Author(s):  
Anna Gårdmark ◽  
Anders Nielsen ◽  
Jens Floeter ◽  
Christian Möllmann
Keyword(s):  
Fisheries Management ◽  
Marine Fish ◽  
Assessment Model ◽  
Fishing Mortality ◽  
Fish Stocks ◽  
The Road ◽  
Stock Status ◽  
Ecosystem Based Management ◽  
Management Plans ◽  
On The Road

Abstract Gårdmark, A., Nielsen, A., Floeter, J., and Möllmann, C. 2011. Depleted marine fish stocks and ecosystem-based management: on the road to recovery, we need to be precautionary. – ICES Journal of Marine Science, 68: 212–220. Precautionary management for fish stocks in need of recovery requires that likely stock increases can be distinguished from model artefacts and that the uncertainty of stock status can be handled. Yet, ICES stock assessments are predominantly deterministic and many EC management plans are designed for deterministic advice. Using the eastern Baltic cod (Gadus morhua) stock as an example, we show how deterministic scientific advice can lead to illusive certainty of a rapid stock recovery and management decisions taken in unawareness of large uncertainties in stock status. By (i) performing sensitivity analyses of key assessment model assumptions, (ii) quantifying the uncertainty of the estimates due to data uncertainty, and (iii) developing alternative stock and ecosystem indicators, we demonstrate that estimates of recent fishing mortality and recruitment of this stock were highly uncertain and show that these uncertainties are crucial when combined with management plans based on fixed reference points of fishing mortality. We therefore call for fisheries management that does not neglect uncertainty. To this end, we outline a four-step approach to handle uncertainty of stock status in advice and management. We argue that it is time to use these four steps towards an ecosystem-based approach to fisheries management.

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