Introduction

Effectiveness of Marine Protected Areas as a tool for restoring marine resources: Estuarine West African experienceOumar Sadioa, Jean-Marc Ecoutinb, Luis Tito de Moraisc, Monique Simierd, Jean Raffrayc and Raymond Laëe

a : IRD, CRODT/LEMAR (UBO/CNRS/IRD/Ifremer), BP 1386, Dakar, Sénégal. b : IRD, LEMAR (UBO/CNRS/IRD/Ifremer), Avenue Jean Monnet, BP 171, 34203 Sète Cedex, France. c : IRD, LEMAR (UBO/CNRS/IRD/Ifremer), BP 70, 29280 Plouzané, France. d : IRD, EME (UM2/IRD/Ifremer), Avenue Jean 

Monnet, BP 171, 34203 Sète Cedex, France. e : IRD, LEMAR (UBO/CNRS/IRD/Ifremer), Bd Sidi Abderrahman Ain Diab, Casablanca, Maroc

Faced with the growing threat of alteration and overfishing of marine resources by human and climatic pressures steadily  increasing, the establishment of marine protected areas (MPAs) appears to be a response to the conservation or restoration of biodiversity (Ecoutin et al. 2014). Bamboung MPA was created in  2004  by  the  Senegalese  government  (Breuil  2011).  This  MPA  is  protected  from  all  fishing  activities.  The  objective  of  this  study  is  to  evaluate  the effectiveness of Bamboung MPA as a tool for restoring marine resources by comparing  it to Sangako bolon which  is an area opened to all  forms of fishing activities.

Materials and methods

The two areas are in the Sine Saloum estuary in Senegal (West African tropical zone) (Fig. 1). The temporal sampling plan took into account the existence of three major hydro-climatic seasons across the Sine Saloum (Diouf 1996; Simier et al. 2004). Fish sampling was performed using a purse seine net with the same methodology in the two areas. Three surveys were conducted annually from 2008 to 2011. Fish were identified by species and then counted and weighed by species to the nearest gram for each seine haul. A subsample of up to 30 individuals per species per haul was measured to the nearest mm. Observed species were classified into bio-ecological categories end by trophic group. The bioecological indicators and the physico-chemical parameters measured were compared between the two areas.

Results

The physico-chemical parameters did not differ between the two areas. Between 2008 to 2011, 54 species belonging to 28 families were identified in the AMP against 47 species belonging to 23 families in the fished area. Median abundance and richness observed are higher in the unprotected area while the estimated biomass, the trophic level, the average size and maximum size are in favor of AMP (Tab. 1). These results corroborate those of many authors (Halpern 2003, Lester et al. 2009). The size spectra is different between the two areas (Fig. 2). According to the analysis of ecological guild, species fulfilling all their life cycle in the estuary are less present in the MPA (Fig. 3). The trophic composition analysis of the settlement of MPA highlights a major role given to the predatory and predatory especially high-level component (Fig. 4).

Tableau 1: Comparison of bio-ecological  indicators by catch per unit. BBG, Bamboung MPA and SNK, Sangako bolon, from 2008 to 2011. Bioecological indicators Area Number of

observations Mean Coefficient variation (%) Median Minimum Maximum

AbundanceBBG 60 676 381 35 0 19127

SNK 72 310 209 100 0 3929

Biomass (g)

BBG 60 24730 278 7176 0 387410

SNK 72 10589 133 6059 0 70415

RichnessBBG 60 7 55 6 1 17

SNK 72 9 35 9 0 19

Trophic Level

BBG 59 3.1 18 3.2 3 4

SNK 71 2.7 16 2.8 2 4

Mean size(mm)

BBG 59 178 43 154 82 362

SNK 71 145 22 145 96 252

Maximum size (mm)

BBG 59 428 50 390 82 1055

SNK 71 321 32 285 113 635

Discussion et conclusion

Both areas have similar water body. Then, the differences are due to the protection effect of Bamboung Bolon. Total species richness is higher in the MPA than in the fished area. From 2008 to 2011, the MPA has a positive effect on biomass, trophic level and size, and a negative effect on the abundance and richness. Estuarine affinity species lose their importance in the MPA while marine affinity species strengthen their central role in the MPA. The results clearly reflect the attraction effect of an MPA and therefore we can confirm that AMP is an effective tool for restoring marine biodiversity.

AcknowledgmentsThe results presented here are from the multidisciplinary program-related projects: Narou Heuleuk (FFEM / AFD / NGO Oceanium / IRD), AMPhore (ANR Biodiversity), CEPIA (AFD / CSRP / IUCN / IRD). The authors want to thank the fishermen and their team leader Mbaye Mbengue and the crew from research vessel Diassanga and its captain F. Sanseo. Without their help, these results could not have been obtained.

Figure 4:  Size  spectra of piscivorous, 2008  to 2011. BBG = Bamboung MPA  (blue line) and SNK = Sangako bolon (red line).

Figure 3: Size spectra of strict estuarine species, 2008 to 2011. BBG = Bamboung MPA (blue line) and SNK = Sangako bolon (red line).

Figure 1: Location and map of the delta of Sine Saloum (Senegal). Location of the Bamboung AMP and the Sangako bolon with position of their sampling  area.

Figure 2:  Size  spectra of  the fish assemblage of Bamboung MPA  (blue  line) and Sangako bolon (red line) from 2008 to 2011.