Fisheries and Resources Monitoring System

Bigeye grunt - Côte d'Ivoire, Ghana, Togo and Benin
Marine Resource  Fact Sheet
CECAF Scientific advice 2016
Bigeye grunt - Côte d'Ivoire, Ghana, Togo and Benin
Fact Sheet Citation  
Friture (Brachydeuterus auritus) - Côte d'Ivoire, Ghana, Togo et Bénin
Owned byFood and Agriculture Organization (FAO) – More
Related observationsLocate in inventorydisplay tree map
FAO Names: en - Bigeye grunt, fr - Lippu pelon, es - Burro ojón, ru - Отоперка

Fishery Indicators
Production: Catch
Geographic extent of Bigeye grunt - Côte d'Ivoire, Ghana, Togo and Benin
Main Descriptors
Considered a single stock: Yes        Spatial Scale: Regional
Management unit: Yes        Reference year: 2010
Biological State and Trend
State & Trend Descriptors
Exploitation rateFcur/F0.1 = 236% ; Fcur/FMSY = 212%Not applicable
Abundance levelBcur/B0.1 = 37% ; Bcur/BMSY = 41%Not applicable
FAO Categories
Exploitation stateOverexploited

Fcur/F0.1: Ratio between the observed fishing mortality coefficient during the last year of the series and F0.1.
Fcur/FSYcur: Ratio between the observed fishing mortality coefficient during the last year of the series and the coefficient that would give a sustainable yield at the current biomass level.
Fcur/FMSY: Ratio between the observed fishing mortality coefficient during the last year of the series and the coefficient that would give a maximum sustainable yield over the long term.
Bcur/B0.1: Ratio between the estimated biomass for the last year and the biomass corresponding to F0.1.
Bcur/BMSY: Ratio between the estimated biomass for the last year and the biomass corresponding to FMSY.
Unless otherwise indicated, the indicators were based on the Schaefer dynamic production stock assessment model.
Habitat and Biology
Climatic zone: Tropical.   Depth zone: Coastal (0 m - 50 m); Shelf - Uppershelf (up to 100 m).   Vertical distribution: Demersal.  

Geographical Distribution
Jurisdictional distribution: Shared between nations

Water Area Overview
Spatial Scale: Regional

Geo References
Resource Structure
Considered a single stock: Yes

The Working Group considered a single stock of Brachydeuterus auritus in the subregion.
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 21703tonnes1990
Catch 13082tonnes1991
Catch 12159tonnes1992
Catch 13862tonnes1993
Catch 19739tonnes1994
Catch 16015tonnes1995
Catch 15842tonnes1996
Catch 20964tonnes1997
Catch 13608tonnes1998
Catch 16581tonnes1999
Catch 13874tonnes2000
Catch 18529tonnes2001
Catch 14536tonnes2002
Catch 9847tonnes2003
Catch 30673tonnes2004
Catch 20869tonnes2005
Catch 22814tonnes2006
Catch 24634tonnes2007
Catch 11695tonnes2008
Catch 20961tonnes2009
Catch 15262tonnes2010

Assessment year: 2011
The CECAF Working Groups have adopted the following Biological Reference Points (BRPs):
- Limit Reference points: BMSY and FMSY
- Target Reference Points: B0.1 and F0.1
Stock status is assigned based on current estimates of fishing mortality (Fcur) and biomass (Bcur) relative to these target and limit reference points (Bcur/BMSY, Fcur/FMSY, Bcur/B0.1, Fcur/F0.1). The results from the stock assessment of this stock are found under the “Biological state and trend section”.
Assessment Model
Type:  Biomass-aggregated
Schaefer dynamic production model

The Working Group used the series of total catch of <i>Brachydeuterus auritus</i> for the period 1990–2010 compiled during the meeting. As an abundance index, the CPUEs of both the industrial and artisanal fisheries in the subregion were used. However the, CPUEs of the industrial fishery, the artisanal Ghanaian fishery (purse seine) and the scientific surveys carried out by the R/V DR. FRIDTJOF NANSEN were used during the last assessment. The input parameters in the spreadsheet are: r (intrinsic growth rate) = 0.99; K (initial biomass) = 30 000 tonnes and BI/K (stock biomass at the beginning of the data, compared with the initial biomass) = 71 percent.
Assessment Model
Type:  Size-structured
Length Cohort Analysis (LCA)

For the LCA model, the Working Group used the length frequency data for species/group of species of Côte d’Ivoire from 2006 to 2010. An extrapolation coefficient (total quantity of catches/total quantity of the sample) was applied to relate the length frequencies to the total catch of the zone. The FiSAT software was then used to determine the growth parameters (L∞, K, and M) for all the species. The parameters of the weight-length ratio (a and b) were obtained from the FishBase globalfish species database. The final matrix involves the individuals of lengths between 6 and 62 cm (Figure 3.3.4a of FAO, 2015).
Yield per Recruit Analysis (Y/R)
Overall Assessment Results

Production Model: The fitting of the model to the observed values was reasonable and was considered acceptable. The value of the Pearson correlation index was 0.6. The estimates of parameters defining the model show that the stock is overexploited both in terms of biomass and fishing mortality. Current biomass of the stock is 41 percent of that producing the maximum sustainable yield (Bcur/BMSY) and 37 percent of that corresponding to the target reference point, B0.1 (Bcur/B0.1). Also the fishing mortality currently applied to the stock exceeds by 136 percent that needed to bring the stock to the biomass level of B0.1 (Fcur/F0.1). Furthermore, the current fishing mortality is (thirty three) 33 percent higher than the fishing mortality that would keep the stock at its biomass level in 2010 (Fcur/FSycur) (Table 3.3.4 of FAO, 2015) [see also "Biological state and trend"] .The model gives a reasonable fit to the data of Cote d’voire, Ghana, Togo and Benin with CPUE of Ghanaian industrial trawlers. The above results indicate that the current biomass of the stock is well below the level producing the maximum sustainable yield and the target biomass of B0.1. It indicates that the stock is overexploited. Length Cohort Analysis (LCA): After the necessary adjustments, the analysis of the model is consistent with the results of the global model, that the stock is overexploited. However, the diagnosis that the stock is fully exploited resulting from the model should be treated with caution.
Scientific Advice

As a precautionary measure and while waiting to receive more precise and complete information, the Working Group recommends a reduction in fishing effort in order not to exceed the 2010 total catch (14 000 tonnes).
Management unit: Yes
Source of information
FAO. 2016. Fishery Committee for the Eastern Central Atlantic, Report of the seventh session of the Scientific Sub-Committee, Tenerife, Spain, 14–16 October 2015 / Comité des pêches pour l’Atlantique Centre-Est Rapport de la septième session du Sous-Comité scientifique. Tenerife, Espagne 14-16 octobre 2015. FAO Fisheries and Aquaculture Report / FAO Rapport sur les pêches et l’aquaculture No. 1128. Rome, Italy.  Click to open
FAO. 2015. Report of the FAO/CECAF Working Group on the Assessment of Demersal Resources – Subgroup South. Accra, Ghana, 15–24 November 2011 / Rapport du Groupe de travail FAO/COPACE sur l’évaluation des ressources démersales – Sous-groupe Sud. Accra, Ghana, 15-24 novembre 2011. CECAF/ECAF Series/COPACE/PACE Séries. No. 15/76. Rome, Italy/Italie.  Click to open
All references to figures, tables and bibliography in the text are found within the source of information.
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