2.4 Exploitation of living resources in coastal lagoons

Local communities have always exploited the complex and diverse environment of lagoons to harvest fish, crustaceans and molluscs, among others. Nonetheless, many coastal lagoons have recently experienced a general decrease in fishing yields, mainly due to environmental degradation, overfishing and the lack of suitable lagoon management plans. Large water projects aimed at claiming land for agriculture, industry, harbouring, etc., have failed to consider the intrinsic value of coastal lagoon biodiversity and their related services and products.

2.4.1 Species of commercial interest

The main commercial species produced in Mediterranean coastal lagoons are the following:
? fish species: grey mullets (with 5 species: flathead grey mullet, Mugil cephalus, and thick lipped grey mullet, Chelon labrosus, Liza ramada, L. saliens and L. aurata), gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax) and spotted seabass (Dicentrarchus punctatus), eel (Anguilla anguilla), big-scale sand smelt (Atherina boyeri);
? shellfish species: Mediterranean mussel (Mytilus galloprovincialis), caramote prawn (Penaeus kerathurus), red swamp crayfish (Procambarus clarki), clams (grooved carpet shell, Ruditapes decussatus; Japanese carpet shell, R. philippinarum) and oysters (European flat oyster, Ostrea edulis, and Pacific cupped oyster, Crassostrea gigas).
Among fish species, grey mullets (Mugilidae family) are highly represented in Mediterranean coastal lagoons with five species, often making up the majority of the production of the lagoons. To give a few examples, in the Koycegiz lagoon (Turkey), grey mullets represent 78.4 percent of the production (Deniz, CR), in all the Greek coastal lagoons 56 percent
(Reizopoulou, CR) and in the Lesina lagoon (Italy) 35 percent (2003 figures, Maccaroni et al., 2005). The presence of a species or another depends on the morphological characteristics and ecology of the single species in relation to the environmental conditions present in the lagoon. For instance, adult C. labrosus prefers hard substrates and marine salinities whereas M. cephalus and L. ramada can live at low salinities, even in freshwater. Among grey mullets, the flathead grey mullet, M. cephalus, is greatly appreciated for its salted and dried egg roe, sold as a delicacy.
As a predator at the top of the food web in coastal lagoons, the European seabass, D. labrax, only represents a small percentage of the total coastal lagoons production, and restocking actions reflect this balance. Indeed, the percentage of European seabass fry in restocking actions never exceeds 5–6 percent (Ardizzone et al., 1988). The spotted seabass (Dicentrarchus punctatus) is also captured in the Bardawil lagoon (Egypt, Bardawil, FS), though it represents a minor production compared with the European seabass.

The gilthead seabream is a very rustic species, but among all lagoons species it is certainly more sensitive to low temperatures. To cope with this problem, in the northern Adriatic valli and in northern Turkey, seabreams are wintered in ad hoc culture facilities, where water temperature is kept above the lethal temperature for the species.
A comprehensive review on eel is presented in this publication by Farrugio (case study 3), and specific issues related the management of eel stocks are analyzed by Ciccotti (case study 4).
The big-scale sand smelt (Atherina boyeri) is the only euryhaline finfish species that reproduces in coastal lagoons. A. boyeri has been subject to several systematic revisions, and genetic studies indicate in fact the existence of three different species. The new name of A. lagunae has been recently proposed for the lagoon form (Milana et al., 2012).
The marbled spinefoot (Siganus rivulatus) and dusky spinefoot (S. luridus), also commonly called “rabbitfish”, are lessepsian species which have migrated to the Mediterranean via the Suez Canal and are present in Egyptian lagoons.
Other fish products are important resources of income for coastal lagoon fishers. This is the case of the greatly appreciated salted and dried egg roe obtained from the flathead grey mullet (Mugil cephalus) and commonly known as bottarga (Italian), or boutargue and poutargue (French), botarga (Spanish) (from the Arab boutharkha = dried fish eggs): this delicacy of the Mediterranean gastronomic tradition is sold in fact at high prices (up to 200 €/kg). In Greece, in the Missolonghi-Aitoliko lagoon complex, the egg roe is one of the few seafood products that can boast of the “protected designation of origin” (PDO) label.

Mullet salted egg roe (Koycegiz lagoon, Turkey), photo ©H. Deniz, 2011

In the Tsoukalio-Rodia lagoon in Greece, egg roe production has grown from 173 kg in 1975 to 2 692 kg in 2000. In the Koyceciz lagoon in Turkey, around 3 tonnes of mullet dry roe are produced yearly. Also, in Egyptian lagoons mullet egg roe (locally called “batarekh”) is produced, the one from the Bardawil lagoon (60 tonnes per year) being considered of the highest quality due to the high salinity of the lagoon; batarekh is also produced in large quantities in winter from cultures of thinlip mullet (Liza ramada) and sold at the local markets (Egypt country report). The Orbetello lagoon (Italy) has an annual production of egg roe ranging from 0.5 to 1 tonne (Lenzi, pers. comm.) and, as processing by-product, ripe females from which ovaries are removed to be salted and dried are filleted, hot smoked, and packed as high priced products.
Among other taxa, shellfish (oysters, mussels and clams) are very common in lagoon environment, representing important exploited resources that have been harvested for human consumption since ancient times throughout the Mediterranean region.
Oyster culture has been introduced by Sergius Orata in the Lucrino lake (Naples, Italy) around 100 B.C. and its production represents one of the first aquaculture trials in Mediterranean coastal lagoons. Oysters used to be a delicatessen in the ancient Roman world (Giacopini et al., 1994) and their culture under the Roman Empire lasted over five centuries. There is some evidence that the ancient Romans also practised shellfish farming in the lagoon of Diana, in Corsica (France country report).
It is interesting to note that in Mediterranean coastal lagoons, the autochthonous European flat oyster (Ostrea edulis), harvested since Roman times, has been recently replaced by the indigenous Pacific cupped oyster (Crassostrea gigas). The Pacific cupped oyster was introduced in Europe and in the Mediterranean after the drastic decline of O. edulis production in the early
1960s, due to the impact of two parasitic epizooites (Bonamia ostreae and Marteilia refringens) 
(Lapegue et al., 2007a; 2007b). Mussel culture is also practised in many Mediterranean coastal lagoons, mainly with longline systems, though in some regions fixed culture systems are still preferred.
The Pacific cupped oyster has been cultured in lake Mellah (Algeria) for several years (Algeria country report) and is still reared in small-scale culture activities in Sardinian lagoons (Marino et al, 2009) and in the Orbetello lagoon (Italy). French coastal lagoons produced 8 825 tonnes of oysters in 2010, though there has been a high mortality of young oysters since 2009, the origin of which has not yet been completely determined. This crisis has led 20 percent of the producers to change their strategy by increasing/starting the production of Mediterranean mussels (Mytilus galloprovincialis) (France country report). French Mediterranean lagoons produced 4 180 tonnes of mussels in 2010. The northern part of the Thau lagoon is divided in three zones dedicated to an intensive shell farming activity carried out by 566 producers (France country report). In Italy, the Venice lagoon has been the first mussel producer until the early 1980s with 100 licences and a production of 30-35 000 tonnes/year, which represented about 60 percent of Italian mussel production. A progressive decline followed and mussel cultures have been moved offshore along the Venetian coast to find larger spaces and better water quality, which favored highest growth rates. At present, mussel production in the Venetian lagoons reaches around 1 500–2 500 tonnes/year. Mussels are also produced in Sardinia on floating facilities called “zattere”, as well as in the Varano (Apulia) and Sabaudia lagoons (Lazio) (Italy country report). In Albania, mussel culture is only practised in the Butrinti lagoon, with a production of 1 410 tonnes in 2010 (Albania country report). Mussel culture has also been carried ou in lake Mellah in the early 1990s, with a production that reached 17 672 tonnes in 1992.

Mussel culture in the Tortoli lagoon (Sardinia, Italy), photo ©D. Crosetti, 2011
Concerning clams, two species are present and harvested today in the Mediterranean region: the grooved carpet shell (Ruditapes decussates), a Mediterranean endemic species, and the Japanese carpet shell also called Manila clam (R. philippinarum), an Asiatic species introduced in 1983, which has displaced the endemic species in many areas and currently makes up most of the Mediterranean clam production.
In Sardinia (Italy), strict rules have been established in order to guarantee the sustainable management of the local grooved carpet shell stocks and avoid the overexploitation that has led to the disappearance of the species in several Italian lagoons. In the lagoons of Sacca di Goro and Scardovari (Italy) for instance, the grooved carpet shells started to be exploited in 1969 with an annual production of 1 200 tonnes, but the stocks were soon depleted, also of their younger specimen (200 tonnes in 1970 and 70 tonnes in 1974); despite the introduction of catch quotas per fisher, stocks have never recovered. The Sacca di Goro lagoon now produces R. philippinarum and its yields represent over half of the Italian Japanese carpet shell production, mostly carried out in Italy in the northern Adriatic lagoons. The spawning of the Japanese carpet shell is induced and performed in hatcheries: about two thirds of Italian farmers collect the seed in the wild and roughly one third buy the seed from fishers, while less than 0.1 percent buy hatchery spat (Marino et al., 2009).
Crustaceans (prawns, shrimps and crabs) are also commonly found in Mediterranean lagoons and some species have a great commercial value. This is the case of the Caramote (Penaeus kerathurus), harvested in Morocco, in the Nador lagoon, and exported to

In northern African coastal lagoons, the grooved carpet clam has been cultured in Mellah lake in the 1990s with a maximum production of 27 622 tonnes reached in 1998, but the production experienced a collapse in the following years (Algeria country report). In Tunisia, in the lagoons of Bizerte, Tunis and El Bibane, clams are usually collected by women by means of traditional archaic fishing gear and, after depuration processes carried out in accordance to EU rules, most of the production is exported to Italy and Spain (Hadj Ali Salem, pers. comm.).

the Spanish market (Malouli Idrissi et al., 2003; Morocco country report), along with the peregrine shrimp (Metapenaeus stebbingi), the Kuruma prawn (Penaeus japonicas) and the green tiger prawn (P. semisulcatus) exploited in Egyptian lagoons for a total production of Penaeids that reached 5 132 tonnes in 2009 (Egypt country report). Culture trials of Caramote have been performed in the late 1980s but with no follow-up (FAO, 2011).

The crab species Carcinus mediterraneus is harvested in the Venice lagoon when moulting (soft-shell crab culture). Soft shell crabs are considered as an expensive culinary delicatessen and can fetch a price of over 80 €/kg. This traditional harvesting activity of is locally called “molechicoltura” (from moeche or moleche, soft shell crab) and is strictly confined to this area of Italy. The particular skill, handed over from father to son, consists in selecting the crabs that are going to moult in short time – recognizable by some specific morphological characteristics – from those that will not turn soft and that fishers traditionally call “crazy crabs”. Nowadays, very few fishers (around 210) carry out this activity, which has remained virtually unchanged since hundreds of years and is half way between the exploitation of wild resources and farming (see paragraph 3.1 and Italy country report).
Several crab species are also exploited: for example, the Portunus pelagicus crab is captured in Egyptian lagoons (Egypt country report), Carcinus mediterraneus is harvested in the Venice lagoon and Upogebia pusilla (locally called “kanjoc”) is manually collected in Montenegro, in the Tivat Salina lagoon, and used as a bait in sparids longline fisheries (Montenegro country report).

Soft crabs selection in the Venice lagoon (Italy), photo ©T. Galvan, 2011
In addition to fishery resources, other uses7 such as collecting small fish for local consumption, worms to be used as baits for fishing and algae as fertilizers, for alginates or pectin production (see paragraph 2.3) are additional sources
of income for fishers; unfortunately, however, the traditional activities to collect these resources, often carried out on an occasional basis and with artisanal means, are slowly disappearing among lagoon communities.

 

2.4.2 Assessment of lagoon production

It is difficult to obtain reliable and updated production data for Mediterranean coastal lagoons: very often, national official statistics do not report separate data for brackish water production; data are not updated, although coastal lagoon conditions can greatly vary, and production data on both extensive aquaculture and intensive culture within the lagoon surroundings are pooled together. Furthermore, coastal lagoon production does not easily fit into the usual marine and inland groupings under which many national fisheries departments categorize the production. Moreover, most of the catch from traditional artisanal fisheries is sold locally, and only the most valuable products are taken into account in national statistics (Kapetski, 1981). However, it is recognized that Mediterranean coastal lagoons’ productivity varies from a few to several

7 An interesting table on various products from Italian coastal lagoons is shown in the Italian country report. 20
hundred kilograms per hectare per year (kg/ha/year) and differ according to the lagoon typology and ecology (e.g. water circulation, depth, salinity, management, etc.).
Perez-Ruzafa et al. (2007) examined fishing yields on a comparative basis, expressed as annual fishing catch per lagoon surface (kg/ha/year), and related these data to some hydrographic and geomorphologic parameters of the lagoons; catches showed a significant positive correlation with the total length increase of inlets and of chlorophyll a concentration while they were negatively correlated to the increase of lagoon
depth and maximum salinity as well as, to a

Mean production of Italian lagoons amounts to about 50 kg/ha (Cataudella et al, 2001), although in some Sardinian lagoons production has reached 300 kg/ha in the 1980s and 600kg/ha in the lagoon of Tortoli (Ciccotti et al, 2012; Italy country report). Albanian lagoons have produced up to 139 kg/ha/year over the period 1980– 1990 (Albania country report). The lake Mellah has had a production of 30 kg/ha/year (calculated from data in Algeria country report). Greek coastal lagoons have an average production of 32 kg/ha/year (Greece country report).
Production in Turkey ranges from 43 kg/ha/year in the Dalyan and Pyraz lagoons to 64 kg/ha/year in the Koycegiz lagoon (Turkey country report). In specific conditions, the high fish productivity could be due to a massive migration of marine fish with good commercial size, caught subsequently to their entrance in the lagoon from the adjacent sea.
lesser extent, minimum phosphate concentration in lagoon waters. These observations could be explained by the fact that currents and hydrodynamics in lagoons are closely related to the bottom topography and,
in shallower lagoons, the bottom is usually well irradiated and winds affect the entire water column promoting the resuspension of materials, nutrients and small organisms from the sediment to the surface – a process that increases global lagoon productivity (Conde et al., 1999; Gamito et al., 2005; Perez-Ruzafa et al., 2007). These findings support the empirical observation that a great variability in fish productivity and catch composition exists between different lagoons featuring different morphologies.
At present, estimating the total production of the most important Mediterranean coastal lagoons remains difficult for all these reasons. A tentative figure as deduced from the country reports (Part 2) adds up to around 156 000 tonnes per year.

 

2.4.3 Environmental quality and lagoon production

Regardless of the intrinsic variables of lagoon production, one can reasonably affirm that a decreasing trend in yields has been observed in all Mediterranean coastal lagoons over the last 30 years and important environmental occurrences have certainly contributed to this reduction. In fact, contrary to what has been observed in the pelagic marine ecosystem, where the decline of catch is mainly due to the overexploitation of living resources, the production decline in lagoons is primarily due to habitat degradation and to changes of the lagoon’s ecological conditions in general (Mediterranean Wetlands Observatory, 2012).
Anthropogenic coastal activities are responsible for important ecosystem alterations in several ways: eutrophication, bacterial contamination, algal blooms (toxic or not), anoxia and fish mortality can influence the productivity, and sometimes the conservation and even the survival of lagoon living resources. Other causes that can affect the productivity of lagoons are: reduced juveniles recruitment due to increased fishing activities along the coasts; altered colonization dynamics and rates due to the reduction of seawater and freshwater flows; and effects of predators such as ichthyophagous birds, which have caused a significant reduction in the yields of Mediterranean coastal lagoons, especially in the last years (see paragraph 2.6.5). Additionally, a more careful and ecological management of wastewater from agriculture and urban settlements has contributed, within a certain limit, to the increase of dystrophic trends in lagoon production. Constraints affecting fisheries and aquaculture in coastal lagoons are very well known and have been extensively described in several reviews (e.g. Ardizzone et al., 1988; Marino et al., 2009).

In the lagoon of Lesina (Italy), the average production has decreased from 120–140 kg/ha in the 1940s to less than 60 kg/ha in the 1960s and to 20 kg/ha at present (Italy country report). The Tunis lagoon has been highly productive until the 1980s (up to 1 000 tonnes/year), when untreated urban waste waters were removed from the lagoon and production decreased to around 200 tonnes/year (Tunisia country report). In the Akyatan lagoon, productivity has decreased from 65 g/ha in the late 1970s to the current 4.6 g/ha (Turkey country report). As a consequence of reduced fish production, in some lagoons (e.g. Thau in France, Venice and Sacca di Goro in Italy) shellfish harvesting, a culture-based activity, has integrated and sometimes replaced traditional fisheries, at least from the socioeconomic point of view, hence becoming the main activity (Perez-Ruzafa et al, 2007).