Perspective Chapter: Mangrove Deforestation and Sustainability of Malacological Resource Exploitation in the Estuarine Ecosystem of the Saloum River Delta, Senegal

Abstract

The estuarine and mangrove ecosystem of the Saloum River Delta is a fragile natural environment. It constitutes an essential element of the estuary’s trophic enrichment characterized by the presence of multiple bolongs. The harvesting of marine mollusks (oyster, ark, cymbium) in the Saloum Delta is mainly done by adult women who represent more than 95% of the stakeholders in this sector. The human activities practiced around this ecosystem are multiple: agriculture, fishing, tourism, beekeeping, use of mangrove wood for cooking and housing, empty shells of arches in the construction of roads and houses, and the composition of aviculture food. The periods of drought in the past three decades, as well as the multiform aggressions of the environment and the populations on the environment, have profoundly modified the hydrological and bio-geochemical functioning of the mangrove ecosystem of Sine-Saloum and significantly degraded the stocks of marine mollusks.

1. Introduction

Among the objectives of the project “Valorization of Species for the Sustainable Use of Wildlife Resources in Senegal (VALUES),” implemented by IUCN in 1998, was the promotion of the sustainable use of flora, fauna, and continental waters by rural populations through appropriate national policies, planning, and investment. The case study on Mangrove deforestation and the sustainability of the exploitation of malacological resources in the estuarine ecosystem of the Saloum River falls within this framework. The mangrove ecosystem is a fragile natural environment. It is an essential element in the trophic enrichment of the estuary. The roots of the mangroves trap the organic matter that they return to the sea. The decomposition of mangrove leaves also brings organic matter to the marine environment. The mangrove is also the biotope where most of the marine mollusk’s harvested by local populations live. Mangroves play a primary role against coastal erosion by stabilizing the substrate and retaining sediments.

The human activities practiced around this ecosystem are multiple: agriculture, fishing, tourism, beekeeping, use of mangrove wood for cooking and housing, empty shells of arches in the construction of roads and houses, and composition of chicken feed (the calcium contained in the oyster shell powder makes the shell of the hen firmer). The chronic drought of the 1980s and its consequences on agriculture have created hyper-salinity and acidification of most soils in almost the entire watershed of the Sine-Saloum ecosystem and consequently the loss of biodiversity. At the socio-economic level, the disruptions caused by these series of degradation have led in recent years to a strong migration of people from inland to coastal areas and a drop in food production (agricultural, fisheries, and forestry) and income, especially for poor women, who are poorly equipped and less prepared for the intensification of exploitation and competition.

The mangrove case study provides a better understanding of the problem of the use of malacological resources in terms of the economic benefits that can be derived from them as well as in terms of the sustainability of use patterns by determining the economic and social values that the populations of the Sine-Saloum Delta attach to these resources. It attempts to assess the impacts of deforestation on the sustainability of the exploitation of marine mollusks in this environment. This study has specifically focused on: (i) proceeding to the description of the sector in order to characterize the actors, the levels of remuneration of the actors, the modes of valorization of the products, and the destination markets; (ii) identifying the level of mangrove deforestation in order to better assess the state of the resource and analyze the impacts in relation to the different uses; and (iii) assessing the impact of deforestation on the sustainability of marine shellfish harvesting and proposing management modalities.

2. Methodology

The study was based on existing data (literature review) and the collection of additional information from various mangrove stakeholders (women seafood gatherers, fish product processors, mangrove wood operators, tourism professionals, NGOs, researchers, etc.). The VALUES project database was also used. This approach made it possible to structure this study around the following axes: (i) assessment of the impacts of mangrove deforestation on the sustainable livelihoods of the various stakeholders; (ii) the typology of the different uses of malacological resources; (iii) estimation of the income that the populations derive from the exploitation of marine mollusks in the Saloum Delta; (iv) assessment of the impact of the disappearance of the mangrove forest on the living conditions of these actors in order to predict supporting actions of IUCN and other partners in a perspective of sustainability and viability of the exploitation of natural deposits of marine mollusks in the mangrove ecosystem of Sine-Saloum; and (v) the proposal of modalities for the management and sustainable use of the Sine-Saloum mangrove that could later be extended to other species and geographical areas.

3. Results and discussion

3.1 The Sine-Saloum mangrove ecosystem

The Sine-Saloum mangrove is located in the intertropical zone, between 12°30′North and 16°30′North latitude and 11°30′West and 17°30′West longitude, 150 km south of Dakar (Figure 1). The Sine-Saloum estuary covers an area of about 80,000 ha (less than 0.6% of the mangrove area in this region). Its climate, of the Sudanese type, is characterized by two distinct seasons, a seven-month dry season (November to May) and a five-month rainy season (June to October). The average annual rainfall (1951–1980) in the basin was between 880 mm in the south and 480 mm in the north [1]. Across the basin, the overall average was 828 mm in the 1950s [2]. It fell to around 500 mm in the 1980–90s. The hydrographic system of this complex consists of three main rivers: the Saloum (110 km long) to the north and northeast, the Bandiala (18 km) to the south and southeast, and the Diomboss (30 km) in between. These rivers are bordered by bolongs. These rivers are bordered by intertidal mudflats more or less colonized by mangroves.

Figure 1.

Map 1: Location map of the Saloum delta, Senegal (Source: Master2 student dissertation).

From Sangomar to Foundiougne, the Saloum channel is relatively deep (depths below 13 m are rare and, in some cases, exceed 25 m at the level of the trenches). Upstream from Foundiougne, the Saloum River crosses the Sine River and becomes very sinuous while keeping a general direction up to Kaolack. Its width is relatively small in this area, rarely exceeding 500 m. The depth also decreases, usually remaining below 5 m. The Diomboss channel is relatively deep. Funds of 10 m are regularly found there. Depths of up to 25 m are recorded in some trenches. Upstream, the Diomboss is divided into several tidal channels, locally called bolongs. Diomboss and Bandiala are characterized by a bolon network, extremely dense unlike the right side of the Saloum River. These bolongs, like the main arms, are bordered by intertidal mudflats. There is no permanent river in the Saloum Delta basin. The slope of the river is gentle, less than 0.6%. It is at the origin of the current result observed upstream. This phenomenon affects the sedimentology and hydrology of the environment [3]. This reverse mode of operation of the estuary governs the arrangement of the salt spindle and the trapping of fine particles.

A large part of the mangrove in this area, 60,000 ha, is located in the Saloum Delta Biosphere Reserve administered by the National Parks Department (DPN in French). The central part (the National Park) and part of the buffer zone are managed by the state, while the rest is managed by local communities. The park and biosphere reserve are located in the Sine and Saloum delta, and the area includes many sandy islets and lagoons, Sangomar Point with its coastal waters, and the Fathala forest. Most of the terrestrial area is covered with mangroves, forests, and saltwater streams. The mangrove that dominates here consists mainly of Rhizophora racemosa, Rhizophora mangle, Rhizophora harissonni, and Avicennia nitida.

The extension of rice cultivation and the exploitation of the forest in the Fathala region constitute a permanent threat to the mangrove [4]. The trophic richness of the Saloum estuary is related to the presence of the mangrove, the existence of very numerous bolongs, and the very flat relief due to the fact that vast areas are covered and discovered at each tidal cycle [5].

Due to the absence of floods in the Sine-Saloum River basin and a strong decrease in freshwater inflow, the trophic richness produced around mangrove vegetation hardly goes beyond its production area toward the adjacent coastal environment. As in Casamance, the main source of trophic enrichment in Sine-Saloum is the remineralization of organic matter, which comes essentially from the mangroves [6].

The mangrove is very extensive in the southern part of Sine-Saloum, where it occupies a good place in the space between the bolongs (name designating small tributaries in the Mandinka language) [7]. Along the edges of the tidal channels located in the downstream part stands the high mangrove (mangroves, 7 to 11 m high). Bare or tanned salty soils are practically absent in this zone.

The shores of the Diomboss and the zone located east of Dionewar, in the central region of the Saloum delta, are occupied by tannes and a low mangrove (2 to 8 m high).

The north of the delta is characterized by a very degraded mangrove whose tree height does not exceed 4 m. This mangrove disappears upstream of the tributary of the Saloum.

The Mollusks of the Sine-Saloum estuary can be classified in the following particular biotopes in relation to the energy of the water movements:

• Low-energy estuarine biotope with the limit of the mangroves Thais callifera, Thais forbesi, and Crassostrea gasar. The main species exploited in this group is the mangrove oyster, C. gasar. The species necessarily fixes itself on a solid substrate. This type of substrate is first provided by the mangrove’s aerial roots. However, oyster banks can be found on sandy or muddy sediments, provided that there are shells on the bottom allowing the fixation of larvae [8]. The species is present in the Saloum estuary, between Djifère and Foundiougne, in the salinity range between 40 and 60‰ [9]. Beyond 60%, the oysters disappear from the environment. Too close to the ocean (3% higher than the salinity rate of the sea, in front of Djifère), the oysters are small in size (mode between 20 and 29 mm) with quite high numbers. A little inland, for salinities of the order of 40‰, we observe large oysters (mode between 40 and 49 mm) with a tighter distribution.

• Medium-energy lagoon and biotope, at the edge of the channels and in the mid-littoral and upper infra-littoral stages, on more or less muddy sand. The characteristic species of these environments are Anadara senilis and Hemifusus morio. We also find in this biotope Conus papilionaceus and Murex cornutus associated with Zostera nana herbariums. M. cornutus as well as Cymbium pepo are also found on sandbanks [10]. Crassostrea gasar is also observed in this biotope on hard bottoms at the edge of the mangrove vegetation.

Anadara senilis accepts all types of muddy bottoms with the exception of reducing muddy sediments with a high organic matter content [11]. The species is consumed in natural deposits by perforating mollusks such as Thais forbesi, Thais callifera, birds, crabs, and rays. The larger subjects are distributed further from the coast and the smaller ones within the salinity range of 35 to 55‰. The growth of the species is low, from 0.5 to 1 mm per year. It can live for 30 years, the age at which it reaches its maximum size, 75 mm. High mortality is observed in this species starting at 10 years of age.

• A high-energy epi-marine biotope where the lagoon population associated with many marine species can be found. Natica fulminea is harvested only in this environment [12]. This species is not accessible to female harvesters.

3.2 Sector and characterization of the actors in the exploitation of marine mollusks

The harvesting of marine mollusks (oyster, ark, cymbium) in the Saloum Delta mainly involves adult women who make up more than 95% of the stakeholders in this sector. Men of all ages and young girls represent the remaining fraction. This last group of actors is mainly present in the northern part of the delta, in the island villages of Dionewar and Bossinkang (98% of stakeholders).

The average age of these adult women is around 45 years. Their husbands work in a trade related to fishing.

Unlike other marine invertebrates, the collection of mangrove oysters is based on a clear sexual specialization. It is exclusively practiced by women. They keep full control of it from harvesting to processing and wholesale and retail sales.

The organization of the picking of the ark, the oyster, and the Cymbium is not the same. The harvesting of the ark is more structured. Women operate on foot or aboard pirogues propelled by the oar. As they do not have their own boats to travel to the collection areas, they resort to borrowing or renting. These canoes travel with two to three women. Outings limited to 1 day are alternated with the processing and drying of the collected products. On the other hand, the decision to collect cymbium is much more individual.

The collection of marine invertebrates is mainly the business of local people, no longer far from their villages. Migrants from Casamance, the Gambia, and Guinea Bissau are few in number (less than 1%). We meet them particularly in Missirah.

3.3 Marine invertebrate valuation methods and destination markets

The ways of valuing oysters have not evolved much. They are cooked or grilled. Cooking is done by boiling in water; the flesh is then removed from the open shells and lightly smoked and dried on racks. The shells are also opened on a wood fire, and the detached flesh is dried directly in the sun. Packaging and transport are done in bags or basins. Drying can take 2 to 3 days depending on whether the product is baked or smoked. Nearly 80% of oyster production is processed before being marketed.

The artisanal processing of ethmalose, the main species landed in the area, yields different products including “tambadiang” (salted and dried whole fish) and “metorah” (smoked and dried fish). Salt-dried (salted, fermented, and dried fish) and guedj (fermented and dried fish) are derived from other species.

The penetration of the monetary economy in this area has favored the strong marketing of oysters and other processed products. The distribution networks depend on the nature of the products. The fresh oysters are sold to tourist centers in the area, while the processed products are largely destined for the weekly markets in the surrounding areas (Passy, Sokone), large urban centers (Kaolack, Dakar), and the sub-region (Gambia). Salt-dried and metorah, little known to Senegalese consumers, are exported to Burkina Faso and Ghana.

3.4 Relative socio-economic importance for local communities

The very important fishery in the Saloum River delta provides annual catches of about 15,000 t, of which 350 are shrimp and 2600 are marine mollusks. The arch is the main resource exploited by the harvesting activity (1634 tons), followed by the murex, oyster, and cymbium, in that order. Ethmalosa fimbriata or cobo, the main species fished in the estuary, constitutes nearly 80% of the total landings of fish and crustaceans (shrimp) in the artisanal fishery.

These mangrove oyster collection activities are highly valued in terms of food, economy, and, to a lesser extent, culture.

Oysters contribute to the protein coverage of local populations because they are consumed fresh or processed. They can even be the staple food in some localities. They are used fresh or smoked to make the sauce to accompany white rice. Having a strong cultural value, oysters are consumed in large quantities during family ceremonies. Other artisanal processed products (guedj, tambadiang, yeet) are substitutes for fresh fish and condiments to flavor dishes.

As an additional remunerative activity during the dry season, fishing and marine invertebrate gathering activities are a brake on rural exodus. They are complementary to the winter agricultural activities of the area. They take place mainly from December to June. The harvesting of marine mollusks is mainly present in the island villages and in the continental Diomboss, constituting 29 and 52% of the fishermen, respectively. The fishing units involved in the harvesting of marine invertebrates are more important in the dry season than in winter (Tables 1 and 2). The vast majority of these fishing units seek arks and oysters in the dry season (1633 and 1499 fishing units out of a total of 3218). The “touffa” is only exploited in the dry season (1274 fishing units). Still in this section, we can notice the low number of fishing units that look for yeet (368 in the dry season, 350 in the rainy season).

AREA	SITE	TOTAL				AREA	SITE	TOTAL				AREA	SITE	TOTAL
		Men	Women	TOTAL				Men	Women	TOTAL				Men	Women	TOTAL
SALOUM; CONTINENT	BIL BAMBARA	1	0	1		DIOMBOSS	BAMBOUGAR MALICK	47	88	135			KATHIOR	17	6	23
	DIOBAYE	124	0	124			BAMBOUGAR MASSAMB	0	9	9			MAR SOULOU	5	20	25
	DJILOR DJIDIACK	28	0	28		CONTINENT	BANGALERE	43	0	43			MAR FAFACO	119	21	140
	FAOYE	93	0	93		TOTAL		90	97	187			MAR LOTHIE	19	58	77
	FATICK	45	0	45			BAKADADJI	2	17	19			MAYA	34	30	64
	FAYACO	297	0	297			BANI	16	0	16			MOUNDE	48	128	176
	FAYIL 1	28	0	28		BANDIALA	DASSILAME SERER	5	1	6			NDINDE	16	7	23
	FAYIL 2	38	0	38			MEDINA SANGAKO	62	34	96			NGADIOR	79	71	150
	FELIR	70	0	70		CONTINENT	MISSIRAH	374	18	392			NIODIOR	76	52	128
	FIMELA	115	0	115			NEMABA	55	21	76		TOTAL		2472	2091	4563
	FOUNDIOUGNE	195	0	195		TOTAL		514	91	605		TOTAL		4842	2285	7127
	GAGUE CHERIF	82	0	82		ISLAND VILLAGES	BAKHALOU	48	6	54
	GAGUE MODY	2	0	2			BAKHOUSS	3	2	5
	GAMBOUL	46	0	46			BAOUT	85	54	139
	KAHONE	10	0	10			BASSAR	243	56	299
	KAOLACK	16	0	16			BASSOUL	82	39	121
	KOYLAL	15	0	15			BETENTI	605	565	1170
	LATMINGUE	32	0	32			BOSSINKANG	178	253	431
	NDAKHONGA	28	0	28			DIAMNIADIO	126	66	192
	NDANGANE DIENE	64	0	64		DIOFANDOR	26	14	40
	NDANGANE SAMBOU	343	6	349		DIOGANE	57	85	142
	NDIAFFATE TOUCOUL	11	0	11		DIONEWAR	296	227	523
	NDOLETTE	50	0	50		DIOUGNDJ	9	13	22
	NERAN	27	0	27		DJINACK	50	81	131
	NIAMDIAROKH	6	0	6		DJIRNDA	89	75	164
TOTAL		1766	6	1772			FALIA	65	88	153
							FAMBINE	77	70	147
							GOUK	20	4	24

Table 1.

Distribution by survey site and area of the number of fishers (by sex) in the Sine-Saloum region during the dry season.

AREA	SITE	TOTAL		All genders		ZONE	SITE	TOTAL		All genders		ZONE	SITE	TOTAL		All genders
		Men	Women					Men	Women					Men	Women
	BIL BAMBARA PEUL	22	0	22			BAMBOUGAR EL HADJ	52	0	52			FALIA	48	101	149
	CADDO (B. BOLONG)	12	0	12		DIOMBOSS	BAMBOUGAR MALICK	81	0	81			FAMBINE	57	22	79
	DIOBAYE	78	0	78			BAMBOUGAR MASSAMBA	52	0	52			FELIR	133	0	133
	DJILOR DJIDIAK	42	34	76		CONTINENT	BAMBOUGAR MOMATH	12	0	12			GOUK	10	2	12
	FAOYE	200	0	200			BANGALERE	24	0	24		ISLAND VILLAGES	KATHIOR	10	8	18
	FATICK	103	0	103			LERANE COLY	18	0	18			KOULOUK	5	2	7
	FAYACO	151	0	151			SOKONE	55	0	55			MAR FAFACO	82	34	116
	FAYIL 1	94	0	94		TOTAL		294	0	294			MAR LOTHIE	47	65	112
	FIMELA	38	0	38			BAKADADJI	20	0	20			MAR SOULOU	4	45	49
	FOUNDIOUGNE	298	0	298			BANI	25	0	25			MAYA	70	7	77
	GAGUE CHERIF	79	8	87			DASSILAME	22	0	22			MOUNDE	51	93	144
	GAMBOUL	24	0	24		BANDIALA	MEDINA	116	0	116			NDINDE	9	11	20
SALOUM	KAHONE	21	0	21			MEDINA SANGAKO	7	0	7			NGADIOR	68	21	89
	KAMATANE	17	0	17		CONTINENT	MISSIRAH	327	3	330			NIADIARA	2	3	5
CONTINENT	KAOLACK	23	0	23			NEMABA	59	0	59			NIODIOR	319	4	323
	KOYLAL	10	0	10			SOUKOUTA	8	0	8		TOTAL		2739	1268	4007
	LATMINGUE	7	0	7			TOUBACOUTA	97	0	97		TOTAL		6269	1319	7588
	NDAKHONGA	45	0	45		TOTAL		681	3	684
	NDANGANE SAMBOU	126	6	132			BAKHALOU	6	4	10
	NDIAFATTE	57	0	57			BAKHOUSS	10	3	13
	NDOLETTE	83	0	83			BAOUT	159	65	224
	NIAMDIAROKH	1	0	1			BASSAR	105	45	150
	PALMARIN DIAKHANOR	66	0	66		ISLAND VILLAGES	BASSOUL	48	18	66
	PALMARIN NGALLOU	358	0	358			BETENTI	444	55	499
	PALMARIN NGOUDOUMANE	32	0	32			BOSSINKANG	199	249	448
	ROKH	38	0	38			DIAMNIADIO	243	58	301
	SANDIKOLI	41	0	41			DIOFANDOR	31	5	36
	SASSARA	116	0	116			DIOGANE	84	29	113
	SIBASSOR	21	0	21			DIOGAYE	35	4	39
	SOUM	54	0	54			DIONEWAR	204	226	430
	THIANGANE	54	0	54			DJINACK BARA	71	29	100
	TOURNAL NONANE	200	0	200			DJINACK DIATAKO	16	28	44
	VELOR KEUR DE DEMBA	44	0	44			DJIRNDA	169	32	201
TOTAL		2555	48	2603

Table 2.

Distribution by survey site and environment of the number of fishers (by sex) in the Sine-Saloum region during the rainy season.

Oyster farming occupies the first place in dry farming in the centers of Dionewar (189), Bétenti (175), and Bossinkang (145). This resource remains the main product sought by the harvesting fishing units in Dionewar (234 fishing units recorded) during the rainy season. The largest numbers of fishing units oriented to the harvesting of loincloth, tufa, and yeet are recorded in the dry season at Betenti, Bossinkang (minus the tufa), and Dionewar (minus the yeet). In wintering, there is only Dionewar for the loincloth in addition to the oyster.

The distribution by the geographical area of the number of women active in harvesting is shown in Tables 3 and 4.

		Fishing			Harvesting		TOTAL		TOTAL
Areas	Men	Womens	total	Men	Womens	total	hommes	femmes
SALOUM CONTINENT	1766		1766		6		1766	6	1772
DIOMBOSS CONTINENT	90		90		97		90	97	187
BANDIALA CONTINENT	510		510	4	91		514	91	605
ISLAND VILLAGES	2453		2453	19	2091		2472	2091	4563
TOTAL	4819	0	4819	23	2285	0	4842	2285	7127

Table 3.

Distribution by gender and geographical area of the number of people active in fishing and gathering in the Sine-Saloum region during the dry season.

	Fishing			Harvesting			TOTAL		TOTAL
Areas	Men	Women	total	Men	Women	total	Men	Women
SALOUM CONTINENT	2546		2546	9	48	57	2555	48	2603
DIOMBOSS CONTINENT	254		254	40		40	294	0	294
BANDIALA CONTINENT	666		666	15	3	18	681	3	684
VILLAGES INSULAIRES	2635		2635	104	1268	1372	2739	1268	4007
TOTAL	6101	0	6101	168	1319	1487	6269	1319	7588

Table 4.

Distribution by gender and geographical area of the number of people active in fishing and gathering in the Sine-Saloum region during the rainy season.

The marine mollusk harvesting activity has seen a resurgence of interest over the past 10 years, with the entry of many women in the exploitation of this resource. In February 1999, some 2000 women were involved in shellfish exploitation in the Saloum Delta [13]. Young schoolchildren may accompany women collectors to the collection sites to earn some money to buy clothes and school supplies.

The shells are now systematically recovered in backfill and road works or calcined by open firing and crushed to provide lime with which bricks are made. These same powdered shells are also used to feed chickens. These new forms of valorization not only generate substantial incomes for the women but also stop the construction of shells piles, which used to occupy a lot of space and started to pose serious environmental problems.

Other no less important activities are associated with the mangrove environment present in the area. Thus, seaside tourism has particularly developed in the estuary of the Saloum Delta with the establishment of vacation villages, second homes, and campsites. This flourishing nature of the mangrove attracts many tourists who come to observe nature and migratory birds in their nesting sites and practice sport fishing and hunting. This activity is a source of employment for local communities and has greatly contributed to the development of local handicrafts. Tourism has also encouraged the construction of large pirogues for visitors in the Saloum bolongs.

Apiculture is a significant activity in mangrove areas. The collection of honey contributes to the improvement of rural household incomes. The exploitation is free for the indigenous populations and is mainly carried out by men.

The mangrove provides other no-less-important products. Local villagers cut firewood and make charcoal. Mangrove wood is widely used for fish smoking. This resource also provides poles to support houses and very resistant construction wood.

The information received during the semi-structured interviews highlighted the medicinal (leaves, bark), religious (sacred forests), and esthetic (necklaces made from small oyster shells) uses of the mangrove.

3.5 Price level and remuneration of the actors

Products that are not very perishable, are easy to sell, and processed by hand are in high demand on the market and at sufficiently remunerative prices.

As detailed information is not available for all the products listed, the oyster industry is used as an illustration. Thus, we note that for dried oysters, the price per kilo is 1000 to 1500 FCFA in the production centers, 2000 at the weekly markets, and 2500 FCFA in the large urban centers. The oyster lids are exported to Asian countries. The price per kilo is 40,000 FCFA at the level of the processing center. The shells are recycled and contribute more than 10% of the women’s income.

Investments in oyster harvesting activities are very basic and are limited to rudimentary instruments consisting of a cutter and a few baskets made by the women themselves.

Operating expenses are virtually nil. The dugout canoes used are propelled by oars. Women without boats rent or borrow them. Many of them use the same pirogue to make their jobs profitable. Payment is usually in kind, such as a basket of smoked oysters at the end of the season.

For a total production of 5 tons of processed products (335 tons fresh equivalent), the commercial value of oysters collected and sold in Saloum is estimated at 30 million FCFA [14].

3.6 Causes and impacts of mangrove deforestation on the estuarine ecosystem

Surveys conducted by CRODT from April to December 2000 indicate income levels between 10,000 and 50,000 CFA francs per season, with a maximum of 140,000 francs for some women.

The income generated is generally earmarked for women’s personal needs, domestic needs, family ceremonies, and childcare (clothing and schooling). Some women save their income for an entire season for an event planned well in advance. Very few sustainable investments are made from these earnings although they provide women with some financial independence.

For all fishery products taken together, the added value generated by fishing activities in this estuarine environment has been estimated at 2 billion FCFA [15].

There are no data on the real importance of mangroves in the different ecological zones of the Saloum Delta that would allow to establish a reference state to serve as a comparison of the action of factors that could lead to the disappearance of mangroves. The water balance for the period 1961–1990 has enabled various researchers to identify the factors responsible for the disappearance of the Sine-Saloum mangrove [16, 17, 18]. These include: (i) the decrease in freshwater inputs related to salinization groundwater contamination; (ii) upwelling of the tidal boundary upstream; (iii) contamination of the water column; (iv) the increase in mangrove mortality (100% recorded in Foundiougne); (v) the disappearance of Avicennia and the appearance of live tannins; and (vi) the resurgence of the phenomena of deposition and eolian reworking.

The periods of drought of the past three decades and the multiform aggressions of the populations on the environment have thus profoundly modified the hydrological and biogeochemical functioning of the mangrove ecosystem of Sine-Saloum and significantly degraded the stocks of marine mollusks. As a result, the age-old balances that have always existed between the populations and their environment have been disrupted. Thus, at the environmental level, hyper-salinity and acidification of most soils and consequently the reduction of biodiversity [19, 20, 21] have been observed throughout the Sine-Saloum catchment area, thus threatening shrimp fisheries. At the socio-economic level, the disturbances generated by these series of degradation have led to a drop in food production (agricultural, fishery, and forestry) and in the income of the populations.

In addition, there has been a decrease in the size of harvested individuals [22]. As the deposits are depleted in the immediate surroundings of the villages, women are forced to go far from their land in search of new sites. This leads to an increase in production costs, a resurgence of conflicts, and an increase in poverty, which are already accentuated in the Saloum Islands.

Beyond the fishing and gathering activities themselves, the disappearance of the Sine-Saloum mangrove has created various problems at the ecosystem level: (i) Difficulty of navigation in certain parts of the estuary and its secondary branches. Today, one can no longer access villages like Niodior or Dionewar at low tide. (ii) Narrowing of the niominkas’ agricultural space due to the progression of tannins and the decrease in water reserves. Coastal erosion is considerably reducing arable land. (iii) Displacement of populations to safer sites (case of Palmarin after the heavy storms of 1987). Villages such as Djifère, Ngallou, and Diakhanor are also threatened by coastal erosion. (iv) Threat to tourist activity—chronic food deficit of nearly 47% of primary needs for wood for energy and drinking water.

4. Recommendations

The exponential growth of the population (3%) and its needs, as well as the modification of the marine environment (rupture of the Sangomar river among others), constitutes, on the one hand, a serious threat to the preservation of the mangrove’s malacological resources and, on the other hand, a hindrance to the socio-economic development of the area because of the risks of food insecurity.

To reverse the situation, a number of management measures have been recommended, including the institution of biological rest and rotation in the collection of marine invertebrates, the restoration of the ecosystem, and the establishment of an institutional framework to ensure the sustainable management of renewable resources.

4.1 Biological recovery and rotation in collection

Biological recovery, in the true sense of the word, aims to protect juveniles and to ensure a spawning season without anthropogenic disturbance. It is to be distinguished from a reduction in fishing (or harvesting) effort over the period of the year. The establishment of a biological rest contributes to ensuring the sustainability of the resource. It is well known that traditionally, the oyster benefits from a period during which harvesting is not practiced. This period generally corresponds to the rainy season (from June to October). The measure has always been adopted, not for reasons of resource protection but rather for reasons of product quality, because sexually mature oysters are said to be milky and tasteless.

Different forums organized with the actors of marine mollusk collection have allowed the mapping of the fishing areas and the consideration of management means for the exploited resources. Rotation systems were defined for the marine mollusk collection sites (oyster, ark, murex, cymbium) in the RBDS area with a biological recovery period of 5 months (June to October), a selective harvesting period (October to January), and an access period (January to June).

The closure of harvesting areas also leads to better growth of marine mollusks and preservation of the resource with a view to ensuring significant and sustainable incomes for harvesters.

Thus, the stakeholders of oyster harvesting in the Sine-Saloum Delta have accepted the development of harvesting areas for this resource in order to improve its productivity. Beach committees were created in some villages, and shellfish harvesting sites were closed in 2001. The impact of these measures has yet to be evaluated.

Beyond the oyster, which represents the most commercially interesting resource (even other products have very high prices per kilogram), it will be necessary to consider the establishment of biological resting on the arches. This type of resource is exploited all year round at the ecosystem level. The commercial and alimentary importance of arches, their permanent availability, means that they must be the subject of a specific scientific monitoring activity that should lead to the establishment of a plan for the exploitation of the different deposits taking into account the bio-ecological knowledge of the species.

4.2 Implementation of sustainable marine invertebrate harvesting practices

The marine mollusk harvesting pressure exerted by Missirah women on oysters is estimated at 23.7% of the available stock (22). This level of exploitation is related to the oyster harvesting methods practiced by the women of this locality: (i) selective harvesting of the largest individuals; (ii) no systematic cutting of mangrove roots; (iii) only one annual passage per harvest site.

Such practices need to be systematized throughout the Sine-Saloum Delta to ensure the sustainable management of natural resources.

4.3 Restoration and rehabilitation of ecosystems

The rehabilitation of degraded habitats and the restoration of ecosystems are becoming over time increasingly important tools for preserving biodiversity and ensuring the sustainability of exploited resources. Rehabilitation aimed at restoring essential ecological functions in modified environments (by man or nature) is particularly appropriate in drought-prone areas.

More ambitious than rehabilitation, restoration aims to restore degraded environments (by man and/or nature) to their natural condition. However, since it is difficult to determine the initial condition of ecosystems and since ecosystems are constantly changing, restoration is rarely a realistic goal. Several authors argue that restoration of ecosystems do not always require intervention because, left in their natural condition, many ecosystems return to a condition close to “pre-disturbance.”

Specific mangrove reforestation actions have already taken place with very poor results, particularly in the Missirah area, under the leadership of NGOs and local youth associations. The ecological particularity of the brackish wetland of the mangrove areas added to the complexity of the reproduction and implantation of young propagules in the mud require that studies must be carried out in parallel with the field actions in order to determine the best conditions for the practice of mangrove reforestation.

4.4 Establishment of an institutional framework for the rational management of environmental resources

The management of fisheries, in terms of both the development of laws and regulations and their application, control, and monitoring, is a process that, until recently, was the exclusive responsibility of public authorities. In recent years, factors related to the scarcity of the resource, the scientific insufficiency of the resources (potentialities, catches, etc.), the resurgence of conflicts, the emergence of professional organizations, as well as the resource management problems faced by the fisheries administration have highlighted the need for concerted management of renewable resources. This approach requires the establishment of an institutional framework bringing together research, administration, NGOs, and professional organizations.

Several institutions including the DPN, DPCA, CRODT, ITA, IUCN, and FOs can be involved in this process.

The DPCA is the institutional framework in charge of putting in place the conditions to achieve the major goals assigned to inland fisheries, including the development and preservation of resources.

The task of CRODT is to monitor the evolution of the fisheries and stocks and to prepare fishery management plans that take into account both biological factors and socio-economic constraints.

The Institute of Food Technology (ITA in French) is in charge of research on the improvement of processing and packaging techniques for fishery products.

The World Conservation Union (IUCN), a leader in the management of so-called “wild” resources, can assist in the formulation of appropriate management policies.

The National Parks Department (DPN in French) manages a large part of the Saloum estuary environment and pilots several projects for the development and management of natural resources in various fields (forestry, fishing, hunting, tourism, etc.) with various national and foreign partners.

Many professional organizations have emerged in the past 10 years. The CNPS and FENAGIE-Pêche are the most representative of them.

5. Conclusions

The mangrove case study provides a better understanding of the problem of the use of malacological resources in terms of the economic benefits that can be derived from them as well as in terms of the sustainability of use patterns by determining the economic and social values that the populations of the Sine-Saloum Delta attach to these resources. The assessment of the impacts of deforestation on the sustainability of the exploitation of malacological resources led to recommendations relating to the establishment of biological resting areas, the institution of healthy practices for the collection of marine invertebrates, the restoration and rehabilitation of ecosystems, as well as the establishment of an institutional framework for the sustainable management of natural resources in the estuary complex of the Saloum Delta Biosphere Reserve.

Acknowledgments

This work was funded as part of the IUCN Senegal Values Project on Wild Forest and Fisheries Resources, the research component of which was entrusted to the Senegalese Institute for Agricultural Research ISRA. We thank them for that. We would also like to thank Dr. Bocar Sabaly BALDE for his support in the English translation of this document.

Conflict of interest

The authors declare no conflict of interest.

Appendices and nomenclature

CNPS	National Collective of Artisanal Fishermen of Senegal
CRODT	Oceanographic Research Center of Dakar-Thiaroye
DPCA	Department of Continental Fisheries and Aquaculture
DPN	Department of National Parks
FENAGIE-Pêche	National Federation of Fishing EIGs
ITA	Institute of Food Technology
PO	Professional Organizations
RBDS	Saloum Delta Biosphere Reserve
IUCN	World Conservation Union
VALUES	Valorization of species for sustainable use of sustainable resources in Senegal