Habitat and Biology
Bottom type: Unspecified. Depth zone: Coastal (0 m - 50 m); Shelf - Uppershelf (up to 100 m); Shelf - Deepshelf (100 m - 200 m). Horizontal distribution: Neritic. Vertical distribution: Demersal/Benthic.
Jurisdictional distribution: National
Considered a single stock: No
During the 2003 meeting, the Working Group adopted the three following administrative stocks:
- Dakhla stock (26 °N–21 °N)
- Cap Blanc stock (21 °N–16 °N)
- Senegal–The Gambia stock (16 °N–12 °N)
As there was no new information on stock structure, the Working Group did not further discuss the definitions of these stocks and used them as they are.
Cephalopods are caught in northwest Africa (northern CECAF subregion) both as a target species by the specific fishery and as bycatch by the non-specific fishery. These fisheries are led by a heterogeneous fleet of vessels from the small canoes to the bottom trawlers using such fishing gears as pots, jiggers and bottom trawls. Depending on nationality and characteristic, the fishery is divided into three main components for statistical purposes: i) artisanal, ii) national industrial, iii) industrial from other countries operating under fishing agreements, the most important of which those between the European Union and nearly all the northwest African coastal countries.
The main target species in the cephalopod fisheries are the octopus (Octopus vulgaris
), the cuttlefish (Sepia
spp., Sepia hierreda
mainly and Sepia officinalis
of which the proportion decreases towards the south) and the squid (Loligo vulgaris
). Sepia bertheloti
is another quite important cuttlefish species in the subregion which is sold under the name “bobtail squid”. Generally octopus is the most abundant species and has the highest commercial value in the cephalopod fisheries, with 65 to 75 percent of total landings. Its importance decreases towards the south where it is replaced by growing proportions of Sepia hierredda
. Squid virtually disappears in landings in the south of Senegal.
Three main bottoms are found along the northwest African coast, more or less coinciding with the distribution zones of the three octopus stocks of the subregion. From north to south these are: i) the zone between Cap Bojador (26 ºN) and Cap Blanc (21 ºN); ii) the zone between Cap Blanc (21 ºN) and the mouth of the Senegal river (16 º N); and iii) the zone between the mouth of the Senegal river (16 ºN) and the border with Guinea-Bissau (12 ºN).
In Morocco the cephalopod fishery is characterized by large fluctuations in catch and effort. It can be divided into several distinct periods depending on where in the region the fleet comes from and the management measures that are in place for this fleet:
Exploitation by foreign fleets: The cephalopod fishery started at the beginning of the 60s in the Atlantic zone south of Morocco between Cap Bojador and Lagouira. At this time cephalopods (octopus, cuttlefish and squid) where only exploited by foreign fleets (Japanese, Spanish). This period saw at the beginning the best catches per unit of effort reaching between 2 and 3 tonnes per day per vessel. The economic attraction for this fishery of this species provoked an intensification in their exploitation.
Exploitation by mixed companies: The cephalopod fishery saw an intermediate phase when the Spanish fleet was joined by a Moroccan fleet in establishment. There was then a period of combined exploitation beginning in the 80s which continued until the departure of the EU fleet in 1999. The national cephalopod fishery only began to develop in 1973 with four freezer trawlers. Afterwards it saw considerable impetus and stabilized, after the freeze in investment since 1992, at around 290 active freezer trawlers. In reply to an increase in effort and to the realisation of overexploitation, a system of biological rest periods was started in 1989. These last one month, October, and correspond to the main recruitment period. Due to their distance, until 1990 the cephalopod stocks were only accessible to the Moroccan and Spanish freezer trawler operating under a series of Morocco–EU fishing agreements which ended in 1999. However, with the development of the infrastructure and the attraction of the value of the products landed since 1993, there has been a massive migration of canoes (artisanal boats) from the north towards southern zones to exploit octopus. Coastal trawlers have also joined this movement, attracted mainly by the consequences of the biological rest period.
Due to the overexploitation, the cephalopod fishery has undergone a series of management measures integrating the new fleets (artisanal and coastal), notably the regulation of trawl mesh size and the size of first catch, as well as the reduction in fishing activity in the coastal zone. Additionally since 1993 the biological rest period has increased by one month to protect the reproduction period (one month in autumn and one in spring). Since 1997, this has grown from 2 to 4 months, two months in spring and two in autumn.
Exclusively Moroccan exploitation: Since 2000 the cephalopod fishery is only composed of a very heterogeneous Moroccan fleet, subdivided into three sections (ocean-going, coastal and artisanal). The artisanal section has become an important component of the fishery. In order to offset the effects of the increase in effort, the biological rest periods have gone from 4 to 7 months. Following a large drop in production in 2001, a management plan for the octopus fishery based on an overall quota was created. 2004 is the year in which the longest biological rest period for octopus is seen, lasting 8 months.
In 2004, the fall in production necessitated a revision of the management plan, which was based partly on the reduction of the overall quota adjusted seasonally and partly on the reduction in effort of the coastal and artisanal sectors following their uncontrolled development over the last decade. The artisanal sector saw the number of vessels reduced to 2 800. For the coastal fleet (190 trawlers), only 100 trawlers are authorized to fish in the zone to the south of Cap Bojador per trip. As for the ocean-going sector, a system of individual transferable quotas has been created. The revision of the cephalopod fishery management plan also covered zoning with a demarcation of fisheries sub-units and zones where trawling is forbidden. In November 2002, the zone between 24° N and 25° N which is normally the main nursery for the Dakhla stock, where the greatest concentrations of juveniles are usually found in autumn, was declared a protected zone and therefore fishing was forbidden. This remained in place until 2005. The revision of the management plan also covered other technical aspects, notably passing from a minimum size of T8 to T7 with a tolerance threshold of 5–10 percent for T8 depending on the season and the increase in minimum mesh size to 70 mm instead of 60 mm.
Several fleets share the exploitation of cephalopod resource along the Moroccan continental shelf. They differ in their technical characteristics and above all in the level of investment and employment generated. Their strategies are tied to the dynamic of the resources and the markets.
Freezer trawler fleet: This is composed of 290 vessels which practise trawl fishing (Spanish and Korean types). They go to sea for an average of fifty days. With the setting up of the seasonal quota, the trips cover a period of between 100 and 120 days on average. The length of these vessels is between 30 and 40 metres. Their tonnage varies between 200 and 600 GRT with an engine power of 600 to 2 000 HP. During the last trips, the number of active vessels has been around 230.
EU fleet: This fleet operated under the Morocco–European Union fishing agreement from 1995 to 1999. It was mainly composed of around one hundred Spanish cephalopod trawlers. These vessels practised the Spanish technique of backwards or sideways trawl fishing using three types of conservation. The GRTs varied between 100 and 400 GRT, with an engine power of 600 to 1 000 HP. The European trawlers ceased operations on 30th November, 1999.
Coastal fresh fish fleet: This fleet is made up of around 100 vessels. The average power and tonnage of this fleet are 400 HP and 60 GRT respectively. The type of trawl used is the atomic trawl (60 mm) and a trip lasts between 6 and 10 days during which time the fish are preserved in boxes under ice. Since 2003 the presence of around one hundred longliners fishing squid and cuttlefish can also be seen, with 235 HP and an average estimated age of four years.
Small trade artisanal fishery fleet: This comprises wooden boats of less than 2 GRT and equipped with outboard motors of between 15 and 25 HP. This fishery uses passive gears: pot and jig.
The number of artisanal fishery vessels saw a notable increase between 1993 and 2002. After this time, the number of boats has not stopped decreasing following the censuses and the regulations which came into force covering this sector. Currently there are 3 000 boats. The fishery is usually practised along the coast, but the range can go beyond 20 nautical miles.
As for octopus, and for the same reasons, the Working Group used the 2001–2006 data.
The data series of total cuttlefish catch in the zone between 20°50’ N and 26 °N was used in the model and two series were used as abundance indices, the CPUE series of the Moroccan freezer cephalopod trawlers and the trawl survey abundance indices.Cap Blanc stock
The total catch series estimated by the Working Group for the region between 21º N and 16° N for 1990–2006 was used in the model as the total catch series of the Cap Blanc Sepia
spp. stock. As an abundance index series the Working Group used the CPUE series of the Mauritanian cephalopod freezer trawlers.Senegal - The Gambia stock
Total annual landing data of all fleets exploiting the Senegal–The Gambia cuttlefish stock from 1993 to 2006 were used for the analysis. Some changes were introduced on previous assessments. These concerned mainly the landing data of the Senegalese fleet which were revised in the new CRODT database. Total catch for 2005 was removed from the analysis as the CPUE value was not considered credible. The CPUE series of the Spanish freezer trawlers was used as an abundance index to fit the model. The doubts expressed by the 2004 Working Group (FAO, 2006) on the reliability of this series were resolved after investigation into the targeting of cuttlefish by this fleet (see Section 5.4.3 of this report: Abundance indices and CPUE).
Schaefer dynamic production model
The Schaefer dynamic production model implemented in and Excel spreadsheet was used to assess the state of the cuttlefish (Sepia
spp.) stocks in the subregion. The model is described in Appendix 2.
The model gives a satisfactory fit to series of trawl survey abundance indices.
Current biomass is greatly below the target biomass B0.1. Fishing effort in the last year is far greater than that which would produce the B0.1 biomass.
The Dakhla Sepia
spp. stock is overexploited. The trawl survey abundance indices show a decreasing trend. It is therefore necessary to reduce fishing mortality on this species to allow a sustained natural production of the stock.Cap Blanc stock
The model fits the data poorly and the results were judged to be unreliable.
Given the CPUEs of the Mauritanian trawlers and the abundance indices from the scientific surveys which have collapsed, the Working Group estimates that the 2004 expert opinion indicating that the stock is overexploited is still valid.Senegal - The Gambia stock
The fit of the model was judges to be acceptable. Current biomass is well below the target biomass B0.1 and fishing effort in the last year is above that which would produce the B0.1 biomass.
The assessment results are relatively reliable. They clearly show that the stock is overexploited both in biomass and fishing mortality terms. This agrees with other indicators on the fishery which show that the stock is in bad condition and that it could degrade further if the current level of exploitation is maintained.
Table 1:Indicators on the state of the stock and the fishery of Sepia spp.
|Stock/abundance index|| F cur /F SYcur|| B cur /B 0.1|| F cur /F 0.1|| B cur /B MSY|| F cur /F MSY|
|Sepia spp. (Dakhla stock)/ Moroccan surveys||273%||13%||563%||15%||507%|
|Sepia spp. Senegal–The Gambia/ Spanish trawlers||157%||31%||289%||34%||260%|
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 current biomass levels.
Bcur/B0.1: Ratio between the estimated biomass for the last year and the biomass corresponding to F0.1.
Fcur/F0.1: Ratio between the observed fishing mortality coefficient during the last year of the series and F0.
Bcur/BMSY: Ratio between the estimated biomass for the last year and the biomass coefficient corresponding to FMSY.
Fcur/FMSY: Ratio between the observed fishing mortality coefficient during the last year of the series and the coefficient giving maximum long term sustainable yield.
The Cap Blanc stock is overexploited. The results are analogous with those from previous assessments (CECAF 2004 and IMROP 2006 Working Groups). This situation is confirmed by the decrease in abundance indices and the average sizes of the octopus caught during the surveys.
Scientific Advicefor Management considerations
The cuttlefish stocks in the region (Dakhla, Cap Blanc, Senegal and The Gambia) show a very reduced biomass and a fishing pressure which is far greater than the production capacity of the stock. In most of the fisheries cuttlefish is both a target species and a bycatch of the octopus fishery. For this reason, any recommendation covering cuttlefish should also take into account eventual effects on the octopus stock. The Working Group therefore made the following recommendations:
- For the Dakhla, Cap Blanc and Senegal– The Gambia stocks, fishing effort should be reduced.
- Cuttlefish catches in the Dakhla stock by the cephalopod fishery should be followed to ensure that effort is not directed away from octopus towards cuttlefish.
Biological State and Trend
Cuttlefish - Dakhla stock
Exploitation state: OverexploitedExploitation rate: Fcur/F0.1= 563%
Abundance level: Bcur/B0.1= 13%
Cuttlefish - Cap Blanc stock
Exploitation state: Overexploited
Cuttlefish - Senegal-The Gambia stock
Exploitation state: OverexploitedExploitation rate: Fcur/F0.1= 289%
Abundance level: Bcur/B0.1= 31%
Source of information
FAO Fishery Committee for the Eastern Central Atlantic/Comité des pêches pour l’Atlantique Centre-Est. “Report of the Working group on the assessment of demersal resources, Sub-Group North” Banjul, The Gambia, from 6 to 14 November 2007. “Rapport du Groupe de travail FAO/COPACE sur l’évaluation des ressources démersales dans la zone Nord” Banjul, Gambie, du 6 au novembre 2007. Rome, FAO . 2010. .
The bibliographic references are available in the report included in "Source of Information".