Last updated on 20 August 2017
Cephalopods stocks are assessed by the Fishery Committee for the Eastern Central Atlantic (FAO/CECAF) Working Group and the Mauritanian Institute of Oceanographic Research and Fisheries (IMROP). The FAO/CECAF Working Group for the Assessment of Demersal Resources (Subgroup North-between Cap Spartel and the south of Senegal) was created in 2000 and their overall objective is to contribute to the improvement of the management of demersal resources in Northwest Africa.
Research surveys and monitoring of the state of the cephalopods have been conducted and information on sampling intensity of the research surveys is available. However, there are still some data limitations regarding the artisanal fishery in Mauritania. There is still some data uncertainties, namely, on catch and effort data at specific-species level. Uncertainties in stock definition were also found. Furthermore, the most recent report available on the assessment of demersal resources in the Northern CECAF zone was from the FAO/CECAF Working Group held in 2013 (FAO 2016). It should be noted that there is a long delay between the working group session and the publication of the report.
Several demersal surveys have been conducted over the entire Mauritanian EEZ. National authorities undertook six surveys on board the R/V AL AWAM since 2009 and Spain carried out three scientific surveys between 2007 and 2009 on board the R/V VIZCONDE DE EZA. Also, the CCLME Project in collaboration with the EAF-Nansen project conducted two ecosystem surveys with the R/V DR. FRIDTJOF NANSEN in the waters off Northwest Africa from Guinea in the South to Morocco in the north (FAO 2015).
Biological sampling of the commercial the artisanal and coastal fisheries is regularly conducted at the main landing ports (Nouadhibou and Nouakchott) monitored by the IMROP. The data series of total catches from 1990 to 2012 is highly variable in terms of the catch level and data quality. For stock assessment analysis was used CPUEs of the Mauritanian ice trawlers and included data from 1999 to 2008 because the exploitation level was considered more homogeneous during that period (FAO 2016).
There is a high interannual and seasonal variability of the octopus stock biomass associated to the spring recruitment event that is associated with the coastal upwelling index and sea surface temperature (Thiaw et al. 2011).
A previous study recommended the use of state-space modelling instead of the observation error models that are usually used for octopus stock assessment in the region (Ono et al. 2012).
Last updated on 20 August 2017
CECAF Scientific Sub-Committee is responsible to provide appropriate advice to the Committee for fisheries managing decisions.
According to the most recent report available of the FAO/CECAF Working Group undertaken in 2013, maintain the fishing effort at its current level (Status quo) would lead considerable reduction in the abundance during the next 5 years. This situation will keep the catches stable during the projected period (2012-2017). The sustainable catches would fall steadily below the sustainable maximum yield (YMSY) (FAO 2016).
The 8th Working Group of the Assessment of the resources and management of the Mauritania Fisheries recommended that the fishing mortality should not exceed the 2013 level of captures (25,000 tonnes), updating and implementation of the provisional management program for the octopus fishery and organization of the working groups to evaluate the implementation and progress of the management plans (IMROP 2014).
Last updated on 20 Aug 2017
The following reference points were established in 2013 working group based on the surveys data (Source: FAO 2016).
Fcurrent/ FSYcur= 109%
Bcur/B0.1: Relationship between the estimated biomass for the last year of the series and the biomass corresponding to F0.1.
Fcur/FSYcur: Relationship between the observed fishing mortality coefficient during the last year of the series and the coefficient that would provide a sustainable yield at the current biomass level.
Fcur/FMSY: Relationship 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.
Fcur/F0.1: Relationship between the observed fishing mortality during the last year of the series and F0.1.
The maximum sustainable yield (MSY) was defined at 32,000 tonnes (IMROP 2014).
Last updated on 20 August 2017
Results from the last stock assessment (2013) indicated that the octopus stock in Cape Blanc is overexploited (Bcurrent/BMSY=92%) and overfishing is occurring (Fcurrent/FMSY=117%) (FAO 2016). However, a progressive improvement of the state of the stock has been observed as well as a reduction of the fishing mortality levels. In 2012 the ratio Fcurrent/FMSY was 125% (IMROP 2014).
Surveys data indicated low recruitment and abundance for octopus in 2010 and in early 2011 but improved considerably in early 2012 as well as the average size /weight of the individuals captured The CPUE s of the Spanish trawlers ranged from 570 kg/fishing day in 1995 to 1,100 kg/fishing day in 2012 (FAO 2016).
The most important species group in the region in terms of catch is the cephalopods, particularly octopus (Octopus vulgaris) which represented around 37% of total demersal catches during the study period. Total catch of octopus decreased, albeit with some fluctuations, from 159,000 tonnes in 1999 to 66,000 tonnes in 2012 (FAO 2016).
Even considering that upwelling system in this area creates strong yearly abundance variance, an accentuated decrease of octopus abundance have occurred since peak captures in the 1960s in the Mauritanian EEZ (Vázquez-Rowe et al. 2012). The abundance indices are highly variable but a decreasing trend has been observer: from 12 kg/30 minutes in 1990 decreased sharply to a minimum of 1.3 kg/30 minutes in 2002. From this year, the global increasing trend was observed until 2008 (8.5 kg/30 minutes) but then biomass indices declined again in 2009 and 2010 (5 kg/30 min) before stabilizing over the last two years at 7 kg/30 min. Also , the average individual weight presented a continuous decrease from 1,360 g in 1982 to 1,138 g in 2008. In 2012, the average weight has increased from 865 g in April to 1,104 g in March (FAO 2016)
In general, despite the peak observed in 1992 and 2009, landings of the octopus in Mauritanian waters presented a no clear trend. Catches of the Mauritanian freezer trawlers ranged between 5,400 to 10,400 tonnes between 2000-2012. The lowest values were observed in 2005 and 2010 but recover again in 2011 and 2012. Catches by the Mauritanian ice trawlers have declined steadily since 1993; the lowest quantity was recorded in 2010 due the effort reduction of this fleet. Spanish trawlers started their activity in 1995, reaching the 12,300 tonnes in 2000, decreasing for 6,400 tonnes in 2003 but recovering in 2004 (7,300 tonnes) and 2005 (9,300 tonnes). From 2005, catches deceased continuously reaching the 4,270 tonnes in 2012. After 2012, with the introduction of the new EU-Mauritania agreement, the cephalopods were not included in the agreement so this fishery is now only allowed to the national fleets. Catches of the artisanal fishery presented a declined after the 1992 peak decreasing until 2002 (2,470 tonnes). Thereafter catches increased until 17,820 tonnes in 2009. The catches decreased in 2010 but then increased again in the last years (FAO 2016).
Previous analysis suggested that the octopus stock off Mauritania was depleted, being less than a fifth of its virgin size (Ono et al. 2012).