Continental aquatic fauna
|Keywords||Continental aquatic fauna, endemic, Endangered species, introduced and invasive|
According to the National Study on Aquatic Biodiversity Continental established by Prof. M. DAKKI, Morocco is relatively rich in continental waters: natural lakes (found essentially in the Middle Atlas) or dams, rivers, merjas, ‘phreatiques’ waters... These waters harbor a Mediterranean fauna characterized by:
- A relatively high endemic total
- A richness in afro-tropical relics, witness of a hot and humid climatic past (tertiary era).
- An altitudinal distribution different from that of Europe, with a frequent ascension in the Moroccan mountains of species in common with Europe.
- A quite particular ecology, reflecting a hydrology and a Mediterranean climate, with Atlantic and Saharan influences more or less marked.
Our aquatic continental fauna includes all the aquatic macro-invertebrates from the Rotifieres until the Insects and Pisces. The inferior groups (Sponges, Cnidaires, Nemathelminthes, Tardigrades, Gastrotriches), microscopic and still not well known, are not considered.
Even though there have been numerous studies already made on continental aquatic fauna, our knowledge seem far from covering the totality of this fauna: many regions are still to be explored, while the specimens of certain groups necessitate appropriate technics which are often ignored by recent researchers.
Also, most researchers have a “fundamental” character; they consist of taxonomic, ecological and biogeographical studies. The ecological aspects most considered are those preferential (in biotypological terms and in microrepartition); they concern more rarely the biological cycle or the productivity and/or the dynamic. Analyses of biodiversity are quasi absent, except studies done within the frame of the definition of protected reservation areas of Morocco (AEFCS/BCEOM/SECA, 1995). In this last study, biodiveristy is evoked in terms of biological and ecological interests of proposed sites for conservation; one must note however that Birds constitute often the principal component of evaluation of these interest for stagnant waters, while Macroinvertebrates and Pisces have primed in the evaluation running water sites. Let us remember that several trials for inventoring (conservation or management) sites, in terms of humid zones, took place (Dakki, 1995).
Global continental aquatic fauna
The inventory (at the level of the Order), based on a selective bibliographic study, is given in Table 12. The principal results can be announced as followed:
- A relatively poor fauna, compared to that of european countries, Asia, and the entirety of the Maghreb: it has only 1575 sub-species, dividied between 646 genuses, 198 famililes, and 37 orders. One must thus consider that this inventory is not exhaustive and represents only 80% of the total real number of species and sub-species (estimated at 2000);
- The Insects, with 1140 species and sub-species, represent 72% of this fauna, with 55% divided between Dipteres and Coleopteres. The Crustaceans represent 14% only, followed by Mollusks, Annelidas, Hydracariens and Pisces, which represent only 2.8-3.3% each. The ichtyological fauna is represented at 36% by imported species. Analysis of the variety (specific richness) by group can be made by the medium number of species that each taxonomic level contains.
The intragenetic variety (the number of species and sub-species by genus) is of 2.4 on average for the entirety of the fauna, with averages even smaller with the groups of essentially running water (Plecopters, Trichopteres, Ephemeropteres, p. ex). The greatest value is among certain famililies of Dipteres, Coleopters, Heteropters, Bivalves...this result shows the existence of a great number of monospecific genuses.
The average number of species and sub-species by family is of 8 for all the fauna, with smaller number for the population of running water than for stagnant waters.
This small diversity constitutes a reason for insisting on the process of conservation, since the protection of one species will often signify the protection of all the genus, at least at the national scale.
The list is presented in Table 13. Among the 1575 ‘taxa’ known in Morocco, 136 species and sub-species are endemic to the country, or an average total of around 8.63%. An equally high proportion gives certainly originality and a great interest in biodiversity of fauna in continental waters of Morocco.
The number of endemic species is unequally divided between different groups:
- Insects: 75 endemic ‘taxa’ (or 55.2% of the total number of endemic species), divided principally between Dipters (26), Trichopters (21), Coleopters (15) and Ephemeropters (10):
- Crustaceans: 39 endemic species (28.7% of the total number), shared especially between Amphipodes (19), Isopodes (8) and Copepodes (7), with two species of Anostraces of the North African genus Tanymastigites and the two Moroccan representatives the Thermosbaenacea;
- Pisces: 11 endemic species, one of whom is extinct (Salmo pallaryi) and all the others among the Cypriniforms (8 species of the genus Barbus, 1 of the complex Varichorinus/Labeobarbus and the Moroccan forme of the Loach of river.
The remarkable presence of the endemic genuses merits a mention apart. it in particular the case, among the Turbellaries, of the monospecific genere Acromyadenium proper to the Atlas. The two species of the genus of Crustaceans Maroccoloana (Isopode) and Maghrebidiella (Amphipode) are equally proper to Morocco.
The total of endemic species (the endemic number in a group compared to the total species of this same group) varies according to the zoological group:
- The highest totals are recorded with the Crustaceans, with the Thermosbaenacea in the first row, followed by the Amphipodes (or the species of the family Metacrangonictidae are in their quasi totality endemic), then by the Isopodes, the Anostraces and the Copepodes;
- The Hydracariens show a relatively high total (around 18%), but it remains to be confirmed with more complete future studies.
- With the Insects, the total average is quite low (6.6%), but the calculated values for each order permit one to detach the Trichopteres (with 29.2%) and the Ephemeropters (with 23.8%) clearly above the other orders presented as endemic. The Coleopterans and the Dipters, while they furnish the greatest number of endemic species, present low totals (3.23-6.25% respectively); nevertheless, a finer analysis has revealed that the most concerned families of Dipters are the Blephariceridae and the Simuliidae, while for the Coleopterans, the endemism is shared between Dytiscidae, Elmidae and Hydrenidae, the highest totals belonging to the last two families.
- A respectable total is recorded (25,0%) with the Pisces1 , notably the Cypriniforms (43.5% of endemism); this notwithstanding the fact that we have not taken into account the great number of regional forms of Barbel described before as an independent species but then put again in synonymy. He also did not take into account of the different forms (variety) of autochtonous ‘Truites’ signaled in the bibliography and which has still not been the object of a precise taxonomic study.
A preliminary study of the geographic repartition of the endemics shows a high concentration at the level of the mountains of the High and Middle Atlas, each having in exclusive more than a quarter of this fauna. The Atlantic plains and plateaus are equally endemic contingent (principally in wells and dayas). The actual results concerning the Rif are still deficient and do not reflect conveniently the originality of the waters of this mountain mass, since it counts only five exclusive species.
On the ecological plan, a fundamental result can be already drawn from the observation of the preferences of endemics: endemism reaches its apogee principally among the phreaticole (stygobies), crenophiles (sources) and rhithrophiles (cold/fresh water courses of altitude) populations. Nonetheless, the courses of low altitude waters and stagnant waters (especially dayas) also have their endemics (with a not negligible contingent of tropical relics).
The real number of endemic Moroccan species is certainly higher than the one we give since, in certain groups, the studies have only just been undertaken (Hydracariens, Isopode Crustaceans, Neuropters, Coleopters, Hydraenidae and Dryopidae.... to cite a few groups which have great defiency.
The voluntary limitation of this study to Moroccan endemics does not permit fully the originality of the fauna of our continental waters; the North African west-Mediterranean endemics are equally well represented in Morocco and certain national sites are among their last refuges.
Moroccan continental humid zones have unfortunately undergone severe degradation linked to an accelerated demographic growth and an industrial and agricultural development which have had negative impacts, of aggravated increase by a prolonged drought. Among these impacts:
- Drainage: large marshy surfaces, in particularly in the Gharb, have been dried to be transformed into culture fields.
- Retention of water by dams: along with their incontestable positive impacts, the lakes of dams have often contributed (with the participation of drainage, pumping and the reduction of water contributions to the phreatic napes) to the drying of marshes and rivers which are found on their downstream side and which the coming in of water has become very irregular. Several examples can be found in the regions of Gharb - Loukkos, the Low Moulouya, the Low Smir, ‘de l’etendue d’eau’ of Iriki to the Low Draa.
- Pumping and derivation of waters destined essentially to irrigation or to the supplying of populations in drinking water.
- Pollution; industry (oil refineries, paper factories, tanneries, ‘Sugar industry’), fertilizers and pesticides. The pollution has reached today all the large rivers, though with differing degrees of impact.
- Anthropozoogenic pressure: anarchical tourism (for example around lakes and certain rivers of the Middle Atlas), eutrophic pollution by excrement of livestock.
- Overexploitation of present ressources (rush, reeds, excessive fishing at Grand Shad near the mouths of rivers...).
- Several degrees of danger have been distinguished, upon which has been added the category “extinct”:
- endangered (M): ‘taxon’ having a small chance of surviving, because of its very restricted repartition in the space (very localized endemics) and the dangers that are present on it or on its habitat; this type of ‘taxa’ demands urgent conservation measures.
- Vulnerable (V): ‘taxon’ of very strict ecological exigences (knowing that an ecological plasticity gives a greater chance of survival to the species and vice-versa) and a limited Moroccan repartition.
- Rare (R): in clear regression, but still relatively well represented in Morocco.
- Probably endangered: apparently rare, but information is too insufficient for its classification.
- Extinct (D): does not exist anymore in Morocco.
The inventory of endangered ‘taxa’ is given in Table 14. The number of rare/vulnerable ‘taxa’ is estimated at 137 species and sub-species, among which 110 are endemic to Morocco (without counting one extinct species, Salmo pallaryi) and other North Africans or west Mediterraneans. Sixteen species are considered endangered and twenty as vulnerable, while the great majority about are classed as rare. The verifications remain to be made for thirteen ‘taxa’, indicated in the present work as probably endangered, or at least rare.
The greatest number of endangered species is among the Insects: 87 (63.5% of the total number), followed by the Crustaceans (28) and the Pisces (11). The percentage of endangered species is 8.7 % for the entirety of the inventoried fauna in the country, while the total of 30-100% is recorded for several groups. The most endangered ‘taxa’ (and the greatest number of dangers) exist in the sources or the cold water courses of high altitude or in phreatic waters. This result is completely expected since the list of endangered ‘taxa’ is composed principally of endemics, ‘infeodes’ especially at the waters of mountain masses and in subterranean regions of low plains.
Only the Pisces (16 or less species, around 36% of the Moroccan ichtyological population) and two Crayfish (Decapodes Crustaceans) are concerned.
These introductions have as principal objectives the development of fishing in continental waters and, into case of Carps, the conflict against eutrophization; the conservation of these species (in terms of elements of biodiversity) is not considered for the moment. Certain ones among them (Pike, Carps, Black-Bass, Rainbow Trout...) are, in part or in totality, artificially reproduced and do not have the positive role in the biological diversity of Morocco. On the contrary, certain introductions could be ill-fated: this is probably the case of deposits realized before in Aguelmame Sidi Ali, which could be a very probable cause of the disappearing of the Trout of Pallary. It is equally to be feared that the deposits of Trout fario in the biotopes containning already the autochtonic populations do not lead to “genetic populations”, without forgetting the possibilities of competition and antagonism between local and introduced ‘taxa’.
A certain role in the conservation of the biodiversity could have been recognized at these introductions, in the measure where they should have contributed to allevating the pressure of fishing on the autochtonic species. The regression of these last species do not seem to confirm this hypothesis, exception to be made in the case of certain Barbels, for these seem to subsit thanks to their large ecological preferences and to the low “quality” that fishermen attribute to them.
Several scientific studies have shown the proliferation of filtering or detritivoric invertebrates, such as the Hydropsychides (Trichopter Insects), the Baetides (Ephemeropter Insects), the Chrionomides (Dipter Insects), the Gammarides (Amphipode Crustaceans), the Melaniides (Gasteropode Mollusks)... These animals profit from the enriching of water courses in organic matter. Also, a rise in altitude of hot water species has been noticed (see Dakki, 1987).
This phenomenon is due principally to the high perturbations (reductions) of the debit of water courses, creating a heating of the waters in high altitude. The best example among the Vertebrates is that of Barbels (Barbus callensis in particular), which rise up to 1900 meters of altitude in certain water courses (for example Guigou) considered usually as habitats for Salmonids.