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Cunene horse mackerel - Guinea-Bissau, Guinea, Sierra Leone and Liberia
Fact Sheet Title  Fact Sheet
CECAF Scientific advice 2020
Cunene horse mackerel - Guinea-Bissau, Guinea, Sierra Leone and Liberia
Fact Sheet Citation  
Chinchard du Cunène (Trachurus trecae) - stock nord (Guinée-Bissau, Guinée, Sierra Leone et Libéria)
Owned byFood and Agriculture Organization (FAO) – ownership
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Species List:
Species Ref: en - Cunene horse mackerel, fr - Chinchard du Cunène, es - Jurel de Cunene, ru - Ставрида западноафриканская

Fishery Indicators
Production: Catch
ident Block Cunene horse mackerel - Guinea-Bissau, Guinea, Sierra Leone and Liberia
Aq Res
Biological Stock: Yes         Value: Regional
Management unit: No        Reference year: 2017
 
 
Aq Res State Trend
Aq Res State Trend
Aq Res State Trend Aq Res State Trend
Aq Res State TrendFcur/F0.1 = 125%; Fcur/FMSY = 113%Not applicable
Aq Res State TrendBcur/B0.1 = 75%; Bcur/BMSY = 83%Not applicable
Aq Res State Trend
Aq Res State TrendOverexploited

Fcur/F0.1: Ratio between the observed fishing mortality coefficient during the last year of the series and F0.1.
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 Bio
Climatic Zone: Tropical.   Depth Zone: Coastal (0 m - 50 m); Shelf - Uppershelf (up to 100 m).   Horizontal Dist: Neritic.   Vertical Dist: Pelagic.  

Geo Dist
Geo Dist: Shared between nations

Water Area Overview
Spatial Scale: Regional

Water Area Overview
Aq Res Struct
Biological Stock: Yes


The Working Group decided to consider five stocks: the northern stock (Guinea-Bissau, Guinea, Liberia and Sierra Leone) made up of Decapterus spp., Caranx spp., Trachurus trecae and other Carangidae; the western stock (Benin, Côte d’Ivoire, Ghana and Togo) made up of the same species; the central stock (Cameroon and Nigeria), consisting of other Carangidae; the São Tomé stock consisted of Decapterus spp., and Caranx spp. and the southern stock (Angola, Congo, Democratic Republic of the Congo and Gabon) consisting of Trachurus trecae, Caranx spp., other Carangidae and Decapterus spp. for the Democratic Republic of the Congo).
Exploit
 

TOTAL CATCH: For the group of Trachurus spp. species, most of the reported catches of Trachurus trecae corresponds to countries from the southern region, with an average of about 35 000 tonnes, mostly from the Angolan coast. Catches corresponding to the southern stock decreased from 61 000 tonnes in 1990 to 3 000 tonnes and 3 300 tonnes in 2004 and 2010, respectively, but about 70 000 tonnes in 2013 and more than 90 000 tonnes in 2015. In the northern and western regions (with averaged annual catches of 14 500 tonnes and 6 500 tonnes, respectively), the catches present noticeably annual oscillations. In the northern stock, high values of more than 30 000 tonnes in the were reported for 2016 and 2017, produced by the industrial fisheries off Guinea Bissau. In the case of the western stock, a record value on 23 000 tonnes occurred in 2014 (by the Ghanaian artisanal fishery) and, conversely, a very low value of about 5 000 tonnes was reported for 2017.
EFFORT: In Guinea and Sierra Leone these species are mainly fished by encircling gillnets and driftnets in the artisanal fishery. In Benin, Cameroon, Ghana, Nigeria and Togo, small carangids are mainly fished by beach seine and purse seine.
Most of the industrial fleets’ effort is concentrated in the Guinean EEZ. The large pelagic trawlers that target horse mackerel come from eastern European countries (the Russian Federation and Ukraine). The nominal effort of this fleet (fishing days) decreased overall from more than 600 fishing days in 1996 to about 400 days in 2004, then recovered and increased to 900 days in 2005 before falling again to 600 days in 2007; there was an increase to 5 600 days in 2017 (Table 5.2.2).
Some of the countries have reported problems in their fishery data and information collection system, and only six of them have updated the effort time series. São Tomé has not reported new data and the available data needs to be revised because of the establishment of the new database.
CPUE: The CPUE, in tonnes per fishing day or positive trip, is calculated for each species or group of species in each stock where data are available (Figure 5.2.2a, figure 5.2.2b, figure 5.2.2c, figure 5.2.2d, table 5.2.2b, table 5.2.2c, table 5.2.2d, and table 5.2.2e). Some of the time series of fishing effort do not have the same units of measurements over the years or between fisheries. Therefore, global CPUEs cannot be considered by stock. For Decapterus rhonchus and Trachurus trecae, the CPUE series is based on the nominal effort of the industrial demersal fleet in Guinea (northern stock). In Angola, Trachurus trecae and T. capensis can be found; thus, in processing the data for Angola together with the other countries, Trachurus spp. was used instead of T. trecae.
Fishery Indicators
TypeMeasureValueUnitTime period
ProductionCatch 21669tonnes1990
Catch 17748tonnes1991
Catch 524tonnes1992
Catch 5840tonnes1993
Catch 5627tonnes1994
Catch 7518tonnes1995
Catch 3479tonnes1996
Catch 12346tonnes1997
Catch 2269tonnes1998
Catch 1468tonnes1999
Catch 9820tonnes2000
Catch 10359tonnes2001
Catch 3758tonnes2002
Catch 13483tonnes2003
Catch 17459tonnes2004
Catch 20974tonnes2005
Catch 12445tonnes2006
Catch 11381tonnes2007
Catch 19402tonnes2008
Catch 23579tonnes2009
Catch 26424tonnes2010
Catch 13189tonnes2011
Catch 13424tonnes2012
Catch 9739tonnes2013
Catch 12807tonnes2014
Catch 18888tonnes2015
Catch 37240tonnes2016
Catch 31487tonnes2017
Bio Assess
 

Assessment year: 2018
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”.
Data

The input data on the total catches of Trachurus trecae (Cunene horse mackerel) in Guinea-Bissau, Guinea and Liberia were used for the period 1997–2017. Catches for Guinea-Bissau for the period 1998–1999 were not available. Catches for Liberia for the period 2014-2017 were not available. Data for Sierra Leone were not available.
Assays were carried out with two CPUEs as proxies to the abundance indices: one based on the industrial pelagic trawlers off Guinea and another based on industrial demersal trawlers off Guinea, the working group considered this data could better reflect the abundance of these group of species than the CPUEs due to these fleets being the ones that catch most of the species in these area. The values of the initial parameters were: Trachurus trecae northern stock: r = 0.45/year, K = 130 000 tonnes and BI/K = 60 percent.
Assess Models
Type:  Biomass-aggregated
Schaefer dynamic production model

The Schaefer dynamic production model on an Excel spreadsheet was used (model described in FAO, 2013). The model requires a time series of total catch and abundance indices of the stock. The estimates of total catch obtained by summing catches from different fleets from different countries were used by region/stock.
Results

RESULTS: The adjustment of the model to the Trachurus trecae data was considered satisfactory was the one calculated with the CPUE from the industrial demersal trawlers off Guinea. A summary of the results is presented in Table 5.6.1b and Figure 5.6.1b. The results show that current biomass (Bcur) represents 75 percent of the target biomass B0.1. The current fishing mortality (Fcur) is 125 percent of the target fishing mortality (F0.1).
DISCUSSION: The results shows that the Trachurus trecae stock is overexploited and the last year’s catches were 63 percent higher compared with those of the last ten years. If the fishing effort remains at this level with the same environmental conditions, a decrease in the biomass can be expected next year.
Sci Advice

As a precautionary measure, do not increase catches of this species above the 2014 level (13 000 tonnes), and reduce effort (FAO, 2020).
Management
Management unit: No
Sources
 
FAO. 2019. Report of the FAO/CECAF Working Group on the Assessment of Small Pelagic Fish – Subgroup South. Elmina, Ghana, 12-20 September 2018. Rapport du Groupe de travail FAO/COPACE sur l’évaluation des petits poissons pélagiques – Sous-groupe Sud. Elmina, Ghana, 12-20 septembre 2018. CECAF/ECAF Series/COPACE/PACE Séries No. 19/81. Rome.  Click to openhttp://www.fao.org/3/ca5402b/ca5402b.pdf
FAO. 2019. Fishery Committee for the Eastern Central Atlantic, Report of the eighth session of the Scientific Sub-Committee, Abidjan, Côte d’Ivoire, 23–26 October 2018 / Comité des pêches pour l’Atlantique Centre-Est Rapport de la huitième session du Sous-Comité scientifique, Abidjan, Côte d’Ivoire, 23–26 octobre 2018. FAO Fisheries and Aquaculture Report / FAO Rapport sur les pêches et l’aquaculture No. 1265. Rome.  Click to openhttp://www.fao.org/3/ca5623b/ca5623b.pdf
FAO. 2020. Report of the Twenty-Second Session of the Fishery Committee for the Eastern Central Atlantic, Libreville, Gabon, 17–19 September 2019. Rapport de la vingt-deuxième session du comité des pêches pour l’Atlantique centre-est, Libreville, Gabon, 17–19 septembre 2019. FAO Fisheries and Aquaculture Report / FAO, Rapport sur les pêches et l’aquaculture No. 1303. Rome.  Click to openhttp://www.fao.org/3/ca8000b/CA8000B.pdf
Bibliography
 
All references to figures, tables and bibliography in the text are found within the source of information.
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