Habitat and Biology
Climatic zone: Tropical. Bottom type: Hard rocky bottom; Soft bottom muddy or muddy-sand. Depth zone: Coastal (0 m - 50 m). Horizontal distribution: Littoral. Vertical distribution: Demersal/Benthic.
The bioecology of S. caeruleostictus
in the West African region has been studied by various authors. The species is found on a large part of the continental shelf, between 10 and 80 m depth. It is most abundant between 15 and 35 m. The species prefers cooler waters (<15°C) and generally lives on hard (rocky) sandy or sandy–muddy bottoms, below the thermocline.
In West Africa, the bluespotted seabream migrates in relation to its life-cycle. These migrations happen parallel to the coast with greater amplitudes in Mauritania and Senegal. In addition, after having reached a certain size, the more coastal young individuals migrate further offshore where food is more abundant.
Jurisdictional distribution: Shared between nations
Considered a single stock: Yes
The S. caeruleostictus
species is sold under the name of bluespotted seabream. It appears to be a single stock which is exploited by the same types of fishery, industrial and artisanal. The Working Group therefore decided to assess it as a single stock.
Due to their generally elevated market value, coastal demersal resources are very sought after in all four of the northern CECAF zone countries (Morocco, Mauritania, Senegal and The Gambia). They are exploited by artisanal and industrial fleets (national and foreign). The fisheries are multi-purpose and demersal fish species often represent bycatch of other specialized fisheries such as the cephalopod, hake or shrimp fisheries.
The demersal fish to be assessed this year are the Pagellus bellottii
, Pagellus acarne
spp., Dentex macrophthalmus
, Pagrus caeruleostictus
spp. and Epinephelus aeneus
. Overall catch for these species fluctuates between around 20 000 and 37 000 tonnes.
Demersal fish resources in Morocco are exploited by a heterogeneous fleet of Moroccan cephalopod freezer trawlers (Ceph. N), coastal fishing vessels: trawlers and longliners (coastal), artisanal boats (artisanal), leased boats and Russian vessels operating under the Morocco-Russia fishing agreement. Only the longliner and some of the artisanal boats target demersal fish, other vessels catch them as bycatch.
In Mauritania exploitation of demersal resources is carried out by various types of trawler: foreign cephalopod (Ceph. E), national cephalopod (Ceph. N), foreign and national hake (Hake), foreign and national shrimp (Shrimp), foreign pelagic trawlers (Pelagic) and foreign and national demersal fish trawlers (Fish).
In Senegal demersal resources are mainly caught by artisanal boats using fishing lines. Two categories exist: motorized line canoes (MLC) carrying out daily trips and ice canoes (IC) equipped with ice that do trips lasting several days. These resources are also caught by Senegalese and foreign trawlers fishing under fishing agreements. Each of these fleets is made up of freezer and ice trawlers. The artisanal fleet is currently composed of 12 619 canoes and the number of Senegalese trawlers was 100 in 2005.
In the Gambia, it is foreign freezer trawlers (PI) and artisanal canoes that exploit demersal resources.
The Schaefer dynamic production model implemented in and Excel spreadsheet was used to assess the state of the stock and fisheries of S. caeruleostictus
. The model described in (FAO, 2007).
The catch series for S. caeruleostictus
in Mauritania and Senegal were used as a total catch series. For the abundance indices series, the Working Group decided to use the CPUE series of the Senegalese ice canoes.
Overall Assessment Results
The model provides a satisfactory fit to the data. The results show that the stock is overexploted. Current biomass is below that corresponding to B0.1. Current fishing effort is far higher than that which would produce a sustainable yield at the current biomass level (Table 1).
Table 1: Indicators on the state of the stock and fishery of Sparus caeruleostictus in the northern CECAF zone
|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|
|Mauritania + Senegal/CPUE Sengalese ice canoes||128%||65%||183%||71%||165%|
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.
Scientific AdviceFor management considerations
The Working Group recommends that fishing effort in this fishery should be reduced to bring the biomass back to a sustainable level. For this reason, the catches of S. caeruleostictus
should be monitored more closely.
Biological State and Trend
Source of information
FAO Fishery Committee for the Eastern Central Atlantic/Comité des pêches pour l’Atlantique Centre-Est. “Report of the FAO/CECAF 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 poissons demersaux – Sous-Groupe Nord” Banjul, Gambie, 6 - 14 Novembre 2007 Rome, FAO . 2010 .
The bibliographic references are available in the report included in "Source of Information".