scholarly journals Applying a two-stage Bayesian dynamic model to a short lived species, the anchovy in the Aegean Sea (Eastern Mediterranean). Comparison with an Integrated Catch at Age stock assessment model.

2014 ◽  
Vol 15 (2) ◽  
pp. 350 ◽  
Author(s):  
M. GIANNOULAKI ◽  
L. IBAIBARRIAGA ◽  
K. ANTONAKAKIS ◽  
A. URIARTE ◽  
A. MACHIAS ◽  
...  
Keyword(s):  
Egg Production ◽  
Missing Values ◽  
Stock Assessment ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Production Method ◽  
Assessment Model ◽  
Two Stage ◽  
Commercial Catch ◽  
The North

Two different stock assessment models were applied to the North Aegean Sea anchovy stock (Eastern Mediterranean Sea): an Integrated Catch at age Analysis and a Bayesian two-stage biomass based model. Commercial catch data over the period 2000-2008 as well as acoustics and Daily Egg Production Method estimates over the period 2003-2008 were used. Both models results were consistent, indicating that anchovy stock is exploited sustainably in relation to an exploitation rate reference point. Further, the stock biomass appears stable or increasing. However, the limitations in age-composition data, potential problems related to misinterpretation of age readings along with the existence of missing values in the survey data seem to favour the two-stage biomass method, which is based on a simplified age structure.  

A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method

2009 ◽  
Vol 66 (9) ◽  
pp. 1999-2011 ◽  
Author(s):  
Cindy J. G. van Damme ◽  
Loes J. Bolle ◽  
Clive J. Fox ◽  
Petter Fossum ◽  
Gerd Kraus ◽  
...  
Keyword(s):  
North Sea ◽  
Egg Production ◽  
Stock Assessment ◽  
Population Analysis ◽  
Spatial Dynamics ◽  
Production Method ◽  
Southern Bight ◽  
The North ◽  
Stock Biomass ◽  
Spawning Stock

Abstract van Damme, C. J. G., Bolle, L. J., Fox, C. J., Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P. R., and Dickey-Collas, M. 2009. A reanalysis of North Sea plaice spawning-stock biomass using the annual egg production method. – ICES Journal of Marine Science, 66: 1999–2011. Uncertainty about the quality of current virtual population analysis-based stock assessment for North Sea plaice (Pleuronectes platessa) has led to various abundance indices. We compared biomass estimates from the annual egg production (AEP) method with current stock assessments based on catch-at-age to validate the current and historical perception of exploitation. The AEP method was also used to investigate the dynamics of the spatial components of plaice in the North Sea. We corrected for fecundity down-regulation and changes in sex ratio. Estimates from both methods were similar in trend and absolute biomass. On the Dogger Bank, there was a dramatic decline in biomass from 1948 and 1950 to 2004, and in the Southern Bight, the stock appeared to increase from 1987 and 1988 to 2004, although not reaching the historically high levels of 1948 or 1950. The timing of spawning of North Sea plaice does not appear to have changed throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast the spatial dynamics of heavily exploited flatfish stocks.

scholarly journals A two-stage biomass dynamic model for Bay of Biscay anchovy: a Bayesian approach

2008 ◽  
Vol 65 (2) ◽  
pp. 191-205 ◽  
Author(s):  
Leire Ibaibarriaga ◽  
Carmen Fernández ◽  
Andrés Uriarte ◽  
Beatriz A. Roel
Keyword(s):  
Dynamic Model ◽  
Bayesian Approach ◽  
Missing Values ◽  
State Space Model ◽  
Assessment Model ◽  
Bay Of Biscay ◽  
Two Stage ◽  
Commercial Catch ◽  
Historical Series ◽  
Biomass Dynamic

Abstract Ibaibarriaga, L., Fernández, C., Uriarte, A., and Roel, B. A. 2008. A two-stage biomass dynamic model for Bay of Biscay anchovy: a Bayesian approach. – ICES Journal of Marine Science, 65: 191–205. A two-stage biomass-based state-space model with stochastic recruitment processes and deterministic dynamics was developed for the Bay of Biscay anchovy population. It is fitted in a Bayesian context with posterior computations carried out using Markov chain Monte Carlo techniques. The model is tested first on a simulated dataset and the effects of different modelling assumptions and of missing values evaluated. Then, it is applied to a real historical series of commercial catch and survey data from 1987 to 2006. Results are compared with those obtained by the standard assessment model for this stock, integrated catch-at-age analysis (ICA). From the posterior distribution of biomass in the latest year (2006), the distribution of unexploited biomass in 2007 can be derived assuming the distribution of recruitment in 2007 to be a mixture of the posterior distributions of past series recruitment. Hence, the effect of different catch options on future biomass levels can be quantified in probabilistic terms. Finally, directions for possible further improvements are indicated.

Stock assessment of the blue grenadier Macruronus novaezelandiae resource off south-eastern Australia

2001 ◽  
Vol 52 (4) ◽  
pp. 701 ◽  
Author(s):  
A. E. Punt ◽  
D. C. Smith ◽  
R. B. Thomson ◽  
M. Haddon ◽  
X. He ◽  
...  
Keyword(s):  
Egg Production ◽  
Stock Assessment ◽  
Production Method ◽  
Integrated Analysis ◽  
Absolute Abundance ◽  
Commercial Catch ◽  
Eastern Australia ◽  
Class Strength ◽  
Catch Rates ◽  
Spawning Biomass

The fishery can be divided into two subfisheries (‘spawning’ and ‘non-spawning’). Commercial catch rates for the ‘non-spawning’ subfishery declined from the late 1980s to 1997, whereas those for the ‘spawning’ subfishery exhibit no obvious temporal trend. An ‘Integrated Analysis’ assessment, of the feasibility of reconciling these differing trends, uses catch (landed and discarded), catch rate, length-at-age, and catch-at-age data and estimates of absolute abundance based on the egg-production method. It emphasizes uncertainty due to model assumptions and the data included in the assessment. Use of the discard data allows more precise estimation of the magnitude of recent recruitments. Spawning biomass is estimated to have declined from a peak in 1989–91 to 1999 although fishing mortality has consistently been <6%for each subfishery. One main reason for the reduction in population size is the weakness of year-classes spawned from 1988 to 1993. Differences in catch rates between the two subfisheries can therefore be explained by interactions between the components of the population harvested by the two ‘subfisheries’, and the trends in year-class strength. A risk analysis is used to evaluate the consequences of different future levels of harvest for different assessment assumptions. Overall, the spawning biomass is predicted to increase over the next five to ten years as a result of the strong 1994 and 1995 year-classes, although the extent of this increase remains uncertain.

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.

scholarly journals A three dimensional, full life cycle, anchovy and sardine model for the North Aegean Sea (Eastern Mediterranean): Validation, sensitivity and climatic scenario simulations

2021 ◽  
Vol 22 (3) ◽  
pp. 653
Author(s):  
ATHANASIOS GKANASOS ◽  
EUDOXIA SCHISMENOU ◽  
KOSTAS TSIARAS ◽  
STYLIANOS SOMARAKIS ◽  
MARIANNA GIANNOULAKI ◽  
...  
Keyword(s):  
Temperature Increase ◽  
Eastern Mediterranean ◽  
Larval Growth ◽  
Somatic Growth ◽  
Aegean Sea ◽  
Fish Growth ◽  
Prey Concentration ◽  
The North ◽  
North Aegean ◽  
North Aegean Sea

We present the development of a 3D full-lifecycle, individual-based model (IBM) for anchovy and sardine, online coupled to an existing hydrodynamic/biogeochemical low-trophic level (LTL) model for the North Aegean Sea. It was built upon an existing 1D model for the same species and area, with the addition of a horizontal movement scheme. In the model, both species evolve from the embryonic stage (egg+yolk sac larva) to the larval, juvenile, and adult stages. Somatic growth is simulated with the use of a “Wisconsin” type bioenergetics model and fish populations with an adaptation of the ‘super individuals’ (SI) approach. For the reference simulation and model calibration, in terms of fish growth and population biomass, the 2000-2010 period was selected. Interannual biomass variability of anchovy was successfully represented by the model, while the simulated biomass of sardine exhibited low variability and did not satisfactorily reproduce the observed interannual variability from acoustic surveys. The spatial distribution of both species’ biomass was in relatively good agreement with field data. Additional single-species simulations revealed that species compete for food resources. Temperature sensitivity experiments showed that both species reacted negatively to a temperature increase. Anchovy, in particular, was more affected since its spawning and larval growth periods largely overlap with the period of maximum yearly temperature and low prey concentration. Finally, simulation experiments using IPCC climatic scenarios showed that the predicted temperature increase and zooplankton concentration decrease in the future will negatively affect anchovy, resulting in sardine prevalence.

scholarly journals The Maximum Length Record of the Blackspot Seabream (Pagellus bogaraveo Brünnich, 1768) for the Entire Aegean Sea and Turkish Territorial Waters

2020 ◽  
Vol 8 (10) ◽  
pp. 2125-2130
Author(s):  
Şenol Paruğ ◽  
Özgür Cengiz
Keyword(s):  
Stock Assessment ◽  
Biological Activities ◽  
Aegean Sea ◽  
Maximum Length ◽  
Northern Spain ◽  
Domestic Markets ◽  
Total Length ◽  
North East ◽  
The North ◽  
Pagellus Bogaraveo

The maximum length, weight, and age information of organisms in an ecosystem, moreover, the first records of migrated exotic species are essential in terms of the basis for the studies on population dynamics, stock assessment, and biological activities. Therefore, the recording of such data may be necessary for scientific databases and new related studies. The Blackspot seabream (Red seabream - Pagellus bogaraveo), which belongs to the Sparidae family, is an important seafood which is marketed fresh and frozen around the Mediterranean and the Aegean seas. Nowadays, this species has high prices depending on market demands in domestic markets as a result of overfishing and is also cultured in northern Spain. It is classified as “Near Threatened Species” in the red list due to its decreasing population trend by the IUCN. A single specimen of the Blackspot seabream with 30.7 cm in total length and 390.00 g in total weight, which was angled in the Saros Bay with a handline by a fisherman on February 08, 2019, was obtained from a fishmonger in Çanakkale. Even though there are bigger individuals in the North-east Atlantic probably depending on polar and/or deep-sea gigantism, the mentioned measurement is the proven maximum total length of this species for the Aegean Sea up to the time.

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

2009 ◽  
Keyword(s):  
New Zealand ◽  
Management System ◽  
Stock Assessment ◽  
Catch Per Unit Effort ◽  
Commercial Catch ◽  
The North ◽  
Anguilla Australis ◽  
Unit Effort ◽  
Access Rights ◽  
Quota Management

<em>Abstract.</em>—The New Zealand eel fishery comprises two species, the shortfin eel <em>Anguilla australis </em>and the New Zealand longfin eel <em>A. dieffenbachii</em>. A third species, the speckled longfin eel <em>A. reinhardtii</em>, is present in small numbers in some areas. Major fisheries in New Zealand are managed under the Quota Management System. Individual transferable quotas are set as a proportion of an annual total allowable commercial catch. The Quota Management System was introduced into the South Island eel fishery on 1 October 2000 and the North Island fishery on 1 October 2004. Freshwater eels have particular significance for customary Maori. Management policies allow for customary take and the granting of commercial access rights on introduction into the Quota Management System. Eel catches have remained relatively constant since the early 1970s. The average annual catch from 1989–1990 to 2001–2002 (fishing year) was 1,313 mt. Catch per unit effort remained constant from 1983 to 1989 and reduced from 1990 to 1999. Statistically significant declines in catch per unit effort for New Zealand longfin eel were found in some areas over the latter period. For management, an annual stock-assessment process provides an update on stock status.

scholarly journals Development, application and evaluation of a 1-D full life cycle anchovy and sardine model for the North Aegean Sea (Eastern Mediterranean)

PLoS ONE ◽  
2019 ◽  
Vol 14 (8) ◽  
pp. e0219671 ◽  
Author(s):  
Athanasios Gkanasos ◽  
Stylianos Somarakis ◽  
Kostas Tsiaras ◽  
Dimitrios Kleftogiannis ◽  
Marianna Giannoulaki ◽  
...  
Keyword(s):  
Life Cycle ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
The North ◽  
Full Life Cycle ◽  
North Aegean ◽  
Full Life ◽  
North Aegean Sea ◽  
Development Application

Age, growth and reproductive biology of the saddled seabream (Oblada melanura) in the North Aegean Sea, Eastern Mediterranean

2020 ◽  
Vol 49 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Ismail Burak Daban ◽  
Ali Ismen ◽  
Mukadder Arslan Ihsanoglu ◽  
Koray Cabbar
Keyword(s):  
Growth Parameters ◽  
Eastern Mediterranean ◽  
Length Distribution ◽  
Total Mortality ◽  
Aegean Sea ◽  
Growth Equation ◽  
Weight Relationship ◽  
The North ◽  
North Aegean Sea ◽  
First Maturity

AbstractThis study determines the length distribution, length– weight relationship, age, growth parameters, mortality rate, sex ratios, length at first maturity and reproduction of saddled seabream (Oblada melanura) collected monthly by fishermen around the Northern Aegean Sea between November 2017 and October 2018. The length–weight relationship was calculated as W=0.0091×L3.11 (R2=0.95) and positive allometric growth was found. The condition factor and GSI varied between 0.81–1.58 and 0.01–9.61, respectively. The spawning season extended from May to July and peaked in June. Total lengths at 50% maturity were 18.97 cm for males and 18.83 cm for females. Parameters of the von Bertalanffy growth equation were: L∞ =29.91 cm, K =0.27 per year, t0 =−0.82 year and age varied between 1 and 8. The instantaneous rates of total mortality (Z) and natural mortality (M) were 1.36 and 0.58 per year, respectively. Rates for fishing mortality F and exploitation E were 0.78 and 0.57 per year, respectively. The mean absolute fecundity (F) was 117 075±23 243 oocytes, ranging from 19130 to 470 132.

First insights towards the population genetic structure and the phylogeographic status of the horse mussel (Modiolus barbatus) from the eastern Mediterranean

2018 ◽  
Vol 99 (5) ◽  
pp. 1111-1118 ◽  
Author(s):  
Ioannis A. Giantsis ◽  
Athanasios Exadactylos ◽  
Konstantinos Feidantsis ◽  
Basile Michaelidis
Keyword(s):  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Genetic Profile ◽  
The North ◽  
Marine Bivalves ◽  
Geographic Populations ◽  
The North Sea ◽  
Low Levels ◽  
Asian Pacific ◽  
Horse Mussel

AbstractThe horse mussel Modiolus barbatus is a marine benthic bivalve, distributed mainly in the Mediterranean basin, that constitutes a fishery product of high economic importance and a promising candidate for aquaculture. The current study provides the first insights regarding the genetic profile of M. barbatus populations from the eastern Mediterranean, by analysis of a partial segment of the mitochondrial COI gene in individuals collected from five sampling localities within the Aegean Sea. To the best of our knowledge, the derived haplotypes represent the first DNA barcodes of M. barbatus from the entire Mediterranean region. Maximum likelihood phylogenetic analysis revealed that M. barbatus from the North Sea and M. barbatus from the eastern Mediterranean may not belong to the same species and as a consequence, there might be three species of the genus Modiolus in Europe. On the other hand, eastern Mediterranean M. barbatus haplotypes were found to be more closely related to the Asian-Pacific Modiolus species. All geographic populations analysed displayed high levels of genetic diversity, in terms of haplotype and nucleotide diversity and a considerable number of unique alleles. Divergence among populations was found at generally low levels, corresponding with the majority of pairwise Fst values not being significant. These findings suggest no population structure and high levels of gene flow, a common feature observed in marine bivalves with long pelagic larval phases.

Sign in / Sign up

Export Citation Format

Share Document