scholarly journals Stock Reduction Analysis of Bigeye Croaker Micropogonias megalops in the Upper Gulf of California, Mexico

Fishes ◽  
2022 ◽  
Vol 7 (1) ◽  
pp. 15
Author(s):  
Ricardo Urías-Sotomayor ◽  
Guillermo Rodríguez-Domínguez ◽  
José Adán Félix-Ortiz ◽  
Gilberto G. Ortega-Lizárraga ◽  
Horacio A. Muñoz-Rubí ◽  
...  
Keyword(s):  
Model Selection ◽  
Gulf Of California ◽  
Selection Procedure ◽  
Fishing Effort ◽  
Free Access ◽  
Commercial Catch ◽  
Probable Function ◽  
Viable Solution ◽  
Stock Biomass ◽  
The One

A stock reduction analysis (SRA) of bigeye croaker Micropogonias megalops was performed based on commercial catch data. SRA solutions were restricted to a 2011 bigeye croaker stock biomass estimate of 14,412 t. The viable solution indicated a reduction in stock of 73.6% from 1983 to 2020 with an initial biomass of 22,186 t. In addition, a possible effect of hyperstability of the stock was evaluated by applying different versions of the Cobb–Douglas catch function. The most probable function based on a multi-model selection procedure was the one wherein the catch does not depend on biomass and is directly proportional to the applied fishing effort of small boats (~7 m) and vessels (~24 m). This situation suggests that in a free access regime, fishing can deplete the resource until it collapses, without observing a significant reduction in its catches until the event is very close.

scholarly journals Analysis of the corvina gulf fishery as a function of management actions in the Upper Gulf of California, Mexico

2017 ◽  
Vol 41 (3) ◽  
pp. 498-505
Author(s):  
Joaquín Humberto Ruelas-Peña ◽  
Carmen Valdez-Muñoz ◽  
Eugenio Alberto Aragón-Noriega
Keyword(s):  
Gulf Of California ◽  
Stock Assessment ◽  
Biosphere Reserve ◽  
Information Criterion ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Optimum Level ◽  
Fishing Mortality ◽  
Commercial Catch ◽  
Management Actions

The gulf corvina (Cynoscion othonopterus), is an endemic species of the Gulf of California, and its fishery is one of the most important in the Upper Gulf of California. Two dynamic biomass models (Schaefer & Pella-Tomlinson), were used to assess the state of the stock due to the lack of enough age data for a reliable full age-structured stock assessment. The models required an historical annual time-series of the abundance index (from 1993 to 2010), derived from the commercial catch and effort data. The Akaike information criterion indicates that the best model was the Schaefer model. The maximum sustainable yield (MSY), estimated with the Schaefer model was 3.100 ton, with a maximum surplus biomass (BMSY) that will allow the capture of 8.200 ton, and a fishing effort (fMSY) of 457 boats. The fishing mortality (F = 0.43) was 26% higher than the fishing mortality at the biological reference point (F0.1 = 0.34). The average biomass from 2006 to 2010 was 52% of the optimum level of the fishery (Est2006-2010 < 1). In 1999 an increase of the fishing effort accelerated the decrease of the biomass. These results indicate that the stock has not been healthy, in spite of the Biosphere Reserve decree, because the core zone has not been respected as a prohibited zone for fishing, and because of the increased fishing effort. 

scholarly journals Gradient boosting for linear mixed models

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Colin Griesbach ◽  
Benjamin Säfken ◽  
Elisabeth Waldmann
Keyword(s):  
Random Effects ◽  
Mixed Models ◽  
Selection Procedure ◽  
Classification Theory ◽  
Gradient Boosting ◽  
Random Structure ◽  
Boosting Algorithm ◽  
The One ◽  
Biased Estimates ◽  
Selection Of

Abstract Gradient boosting from the field of statistical learning is widely known as a powerful framework for estimation and selection of predictor effects in various regression models by adapting concepts from classification theory. Current boosting approaches also offer methods accounting for random effects and thus enable prediction of mixed models for longitudinal and clustered data. However, these approaches include several flaws resulting in unbalanced effect selection with falsely induced shrinkage and a low convergence rate on the one hand and biased estimates of the random effects on the other hand. We therefore propose a new boosting algorithm which explicitly accounts for the random structure by excluding it from the selection procedure, properly correcting the random effects estimates and in addition providing likelihood-based estimation of the random effects variance structure. The new algorithm offers an organic and unbiased fitting approach, which is shown via simulations and data examples.

scholarly journals The Optimal Selection for Restricted Linear Models with Average Estimator

2014 ◽  
Vol 2014 ◽  
pp. 1-13
Author(s):  
Qichang Xie ◽  
Meng Du
Keyword(s):  
Model Selection ◽  
Linear Models ◽  
Weighted Average ◽  
Selection Procedure ◽  
Information Criterion ◽  
Optimal Weights ◽  
Model Average ◽  
Squared Error ◽  
Generalized Information Criterion ◽  
Risk Investment

The essential task of risk investment is to select an optimal tracking portfolio among various portfolios. Statistically, this process can be achieved by choosing an optimal restricted linear model. This paper develops a statistical procedure to do this, based on selecting appropriate weights for averaging approximately restricted models. The method of weighted average least squares is adopted to estimate the approximately restricted models under dependent error setting. The optimal weights are selected by minimizing ak-class generalized information criterion (k-GIC), which is an estimate of the average squared error from the model average fit. This model selection procedure is shown to be asymptotically optimal in the sense of obtaining the lowest possible average squared error. Monte Carlo simulations illustrate that the suggested method has comparable efficiency to some alternative model selection techniques.

Exploitation status and stock assessment by pseudo-cohort analysis of the bluefish, Pomatomus saltatrix, in the Gulf of Gabes (Tunisia)

2007 ◽  
Vol 87 (5) ◽  
pp. 1315-1319 ◽  
Author(s):  
Khalifa Dhieb ◽  
Mohamed Ghorbel ◽  
Othman Jarboui ◽  
Abderrahmen Bouaïn
Keyword(s):  
Stock Assessment ◽  
Cohort Analysis ◽  
Fishing Effort ◽  
Individual Growth ◽  
Eastern Coast ◽  
Pomatomus Saltatrix ◽  
Gulf Of Gabes ◽  
Gulf Of Gabès ◽  
Exploitation Status ◽  
The One

The bluefish, Pomatomus saltatrix, is quite abundant in the Gulf of Gabes, off the south-eastern coast of Tunisia. It is commercially exploited by artisanal gears and trawlers all year round, and by purse seine nets from May to August (bluefish fishery season). Catches of bluefish, in the period 1996–2004 fluctuated between 365.6 t and 1240.1 t with an annual average of 805 t. This fluctuation, partially due to the migratory nature of the species, could be also attributed to the fleet activities that sometimes changed at the mercy of the operators. The analysis of the virtual population of bluefish in the Gulf of Gabes showed that, in 2002, the stock that had just recovered rightly after an excessive fishing in 1996–1997 was again subject to a fishing effort that passed its capacity (E=0.71; E>0.5). The biomass (B) estimated to be ~2178.9 t only tolerated the extraction of 713.4 t (more or less one-third of B). However, the three fleets in use removed 1029.1 t with a yield per recruit (Y/R) of 70.5 g. As a result of this over-fishing, the actual stock of bluefish in the Gulf of Gabes was characterized by individuals having a mean total length of 17.88 cm, a size which is much lower than the one at first sexual maturity (23.5 cm). The turnover (D/B) being of 75.23%, it did not allow the reconstitution of the stock. The total removals (~1639 t) due to both natural mortality (M=0.28) and fishing mortality (F=0.675) had to be compensated especially by individual growth (1534.2 t; 93.6%) because of the low weight of the recruits.

scholarly journals The Catch 22 syndrome of social scientists in the semiperiphery: Exploratory sociological observations

Sociologija ◽  
2010 ◽  
Vol 52 (4) ◽  
pp. 337-358 ◽  
Author(s):  
Marina Blagojevic ◽  
Gad Yair
Keyword(s):  
Political Organization ◽  
Academic Excellence ◽  
Free Access ◽  
Social Scientists ◽  
Scholarly Publications ◽  
The Social ◽  
Catch 22 ◽  
The One ◽  
Definition Of ◽  
Problem Setting

This paper describes the parochial predicament of the social sciences by looking at world sociology in its Janus-like face: on the one hand we focus on the intellectual, political, and sometimes even ethical compromises that social scientists in European semiperipheral countries forgo in order to gain acceptance and recognition in world sociology. On the other hand we show how these compromises paradoxically impoverish intellectual potentialities in the major centers of academic excellence too. In the analyses we focus on different interrelated facets of scholarly work where these paradoxes take shape: problem setting and conceptualization, the hierarchy of scholarly publications, the definition of excellence through citation patterns, scientific conferences, and lastly, funding schemes for research. We argue that the social and the political organization of the World System of Science jeopardizes free access to multiple and plural perspectives of the social. A potential source of ideas, theories, and paradigms is hampered by the hierarchical division of labor between scientists in the centers of science and their peers in semiperipheral countries, whose knowledge remains unutilized and sidelined.

Impact of Innovative Capital on the Global Performance of the European Union

2021 ◽  
pp. 90-124
Author(s):  
Cristina Raluca Gh. Popescu
Keyword(s):  
The Other ◽  
Free Access ◽  
The European Union ◽  
Dynamic Component ◽  
Successful Model ◽  
Global Performance ◽  
Potential Factors ◽  
And Performance ◽  
The One ◽  
Access Data

With the main objective of determining the essential factors that incorporate or enhance innovative capital, the present study, based, on the one hand, on the evaluation of the literature, allowed identifying ten potential factors and centered, on the other hand, on the analysis represented by the linear regression facilitated displaying the interdependencies between these factors and performance, thus determining the overall meaning and intensity of their contribution. In order to identify general and essential trends, to eliminate the cyclical influences of innovative capital, the present study was conducted on the basis of public and free access data contained by Eurostat, the transparency and accessibility of information being very important criteria in defining a simple and successful model, applicable for assessing the contribution of intellectual capital, in general, and its most dynamic component of innovative capital to increasing the performance of organizations.

Analysis of crab size structure and the fishing effort applied to a crab fishery in northwest Mexico

Crustaceana ◽  
2018 ◽  
Vol 91 (2) ◽  
pp. 225-237 ◽  
Author(s):  
César A. Heredia-Delgadillo ◽  
Guillermo Rodríguez-Domínguez ◽  
Raúl Pérez-González ◽  
Nicolás Castañeda-Lomas ◽  
Sergio G. Castillo-Vargasmachuca ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Size Structure ◽  
Coastal Lagoons ◽  
Low Frequency ◽  
Fishing Effort ◽  
Double Ring ◽  
Northwest Mexico ◽  
Fishing Gears ◽  
Fishery Cooperatives ◽  
Ring Net

The fishing effort of a Sinaloa crab fishery in the Gulf of California in 2014 was analysed based on fishermen’s interviews, official catches and permits, and information from a sample of fishing logbooks from five fishery cooperatives operating in four coastal lagoons that contained the daily catch from individual fishing trips. Unauthorized gear, a double-ring net (DR), was used most frequently (>70% of the fishers) for crab fishing, although authorized single-ring nets and Chesapeake traps (CT) were also used with low frequency. The estimated fishing effort was 641 boats/day in the four coastal lagoons, which was 34% more than authorized, and 818 boats/day were employed in all of Sinaloa. A total of 57 479 fishing gears were estimated for the study area, which was 49.9% greater than the maximum authorized number, and 80 822 nominal fishing gears were estimated for the entire Sinaloa crab fishery, 14.15% more than the total gear limit (70 800). The size of the mesh used in the gear was smaller than the authorized limit of 76 mm, and >50% of the catches included crabs of unlawful size. It is argued that the effort must be regulated in terms of the number of vessels, per unit time, and not the number of gears. The information from this study demonstrates a failure to monitor compliance with current regulations and thus means that other strategies for the sustainable management of the fishery, such as co-management, should be tested.

A new species of Cymbasoma (Copepoda, Monstrilloida) from the northern coast of Turkey (Black Sea) with comments on the C. longispinosum species-group

Crustaceana ◽  
2014 ◽  
Vol 87 (11-12) ◽  
pp. 1393-1410 ◽  
Author(s):  
F. Üstün ◽  
T. Terbiyik Kurt ◽  
E. Suárez-Morales
Keyword(s):  
New Species ◽  
Black Sea ◽  
Gulf Of California ◽  
Relative Length ◽  
Species Group ◽  
The Body ◽  
The Black Sea ◽  
Northern Coast ◽  
Black Sea Coast ◽  
The One

Cymbasoma sinopense sp. nov. is described from an adult female collected off the Sinop coast, in the southern Black Sea, Turkey. This is the first species of this genus recorded from the Black Sea coast of Turkey. The new species is a member of the widespread Cymbasoma longispinosum species-group, and it closely resembles C. chelemense Suárez-Morales & Escamilla, 1997 from the Yucatan Peninsula and C. californiense Suárez-Morales & Palomares-García, 1999 from the Gulf of California. This species can be distinguished by a combination of subtle characters, including the body proportions, the structure and armature of the fifth legs, the ornamentation of the genital somite, and the relative length of the ovigerous spines. A previous report of C. longispinosum from the northern Black Sea probably represented a misidentified record of C. sinopense sp. nov. The Mediterranean reports refer to a species that is different from the one of the Black Sea. Comparative comments and data including the main taxonomic characters of members of the Cymbasoma longispinosum species-group are presented. Overall, it is confirmed that records of this species from different geographic areas should be revised carefully because they could represent undescribed species. A key for the identification of the females of the currently known species assigned to the Cymbasoma longispinosum species-group is included.

Population Dynamics of the Arcto-Norwegian Cod

1967 ◽  
Vol 24 (1) ◽  
pp. 145-190 ◽  
Author(s):  
D. J. Garrod
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Group Iii ◽  
Spawning Stock ◽  
Stock Recruitment ◽  
Post War ◽  
The One ◽  
Definition Of

By reason of its geographical distribution, the Arcto-Norwegian cod (Gadus morhua) supports three distinct fisheries, two feeding fisheries in the Barents Sea and at Bear Island–Spitsbergen, and a spawning fishery off the Norway coast. In the past this diversity of fishing on the one stock has made it difficult to unify all the data to give an overall description of post-war changes in the stock. In this contribution three modifications of conventional procedures are introduced which enable this to be done. These are: (i) a system of weighting the catch per unit effort data from each fishery to a level of comparability; (ii) a more rigorous definition of the effective fishing effort on each age-group; (iii) a method of estimation of the effective fishing effort on partially recruited age-groups.Using these methods the analysis presents the effects of fishing on each fishery in the context of its effect on the total stock, and at the same time it indicates ways in which factors other than fishing may have influenced the apparent abundance of the stock. The treatment of the data is also used to derive estimates of spawning stock and recruitment of 3-year-old cod for subsequent analysis of stock–recruitment relationships.

Variation in geographic stock area, catchability, and natural mortality of ocean shrimp (Pandalus jordani): some new evidence for a trophic interaction with Pacific hake (Merluccius productus)

1995 ◽  
Vol 52 (5) ◽  
pp. 1018-1029 ◽  
Author(s):  
Robert W. Hannah
Keyword(s):  
Mortality Rates ◽  
Fishing Effort ◽  
Trophic Interaction ◽  
Natural Mortality ◽  
Commercial Catch ◽  
Merluccius Productus ◽  
Shrimp Abundance ◽  
New Evidence ◽  
Incorrect Information ◽  
Logbook Data

Interannual variation in geographic stock area, catchability, and natural mortality of age 2 ocean shrimp (Pandalus jordani) was investigated for the years 1980–1990, using commercial catch and logbook data. Stock area changed gradually from 1980–1990, but showed wide variation, demonstrating that an assumption of constant catchability is not valid for ocean shrimp. Stock area was positively correlated with total catch, suggesting that stock area increases roughly in proportion to shrimp abundance. The time series of fishing effort and effort per unit stock area were quite different, showing that fishing effort probably gives incorrect information on time trends in ocean shrimp fishing mortality. Natural mortality rates varied widely over the study period also and were positively correlated with the abundance of age 2+ Pacific hake (Merluccius productus), a known shrimp predator. The best correlations were between natural mortality rates and the number of age 2–7 Pacific hake. Hake abundance indices that included only age 3+ fish were not significantly correlated with shrimp natural mortality rates, suggesting that if a trophic interaction exists between these two species, it may be influenced by hake recruitment events.

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