Environmental Engineering Reference
In-Depth Information
species and size. In the course of the past few years Ayissi,
I. (personal observations) noted an increase in the presence
of Asian trawlers (from China, Korea, Japan) off Camer-
oon's coast, vessels with the reputation of often unsatis-
factory adherence to fisheries regulations. Between 1999
and 2009 Chinese pair-trawlers ''chalut-boeuf'' were
deployed on Cameroon's continental shelf. Pair-trawling is
well known for its devastating effects on benthic fauna and
flora (Liggins and Kennelly 1996 ).
Little or no recent data are published on catch statistics
and the status of fish stocks in Cameroon, but circumstantial
evidence suggest that these follow the general trend of
fisheries in the Eastern Central Atlantic (FAO area 34), i.e.
increasingly overexploited stocks (FAO 2011).
• Chemical pollution
Only the lower 20 km of the Sanaga River are navigable,
up to Edea, home to the second largest hydropower plant in
the country (265 MW). The ALUCAM aluminium smelter
in Edea is dependent on the Sanaga for process water and is
the single biggest energy consumer in Cameroon (Van der
Waarde 2007 ). The lower reaches of the Sanaga, including
its estuary, are sparsely populated (\20/km 2 ) with the local
population engaged in benthic bivalve harvesting from the
river and fishing. The coastline is mostly inhabited by for-
eign fishermen from Nigeria, Benin, Ghana and Togo
fishing along the coast in larger fishing boats. The alumin-
ium smelting industry produces 500,000 tonnes/year of
material in suspension in the Sanaga River (Atangana
1996 ). The impact on the river's ecology and on its estuary
near Mouanko (N 03.58867, E009.6489) is unclear. ''Red
mud'', the waste product from the extraction of aluminium
from bauxite, is highly contaminating for the environment
since it consists of a highly alkaline fine particulate con-
taining heavy metals and other pollutants (White et al.
1997 ; Pascucci et al. 2009 ). The question arises about heavy
metal toxicity among the fisher communities who subsist on
bivalves and other locally extracted sea food. Similarly, the
health of top-level marine predators such as small ceta-
ceans, which are known to accumulate contaminants, may
be at risk. The coastal beaches are also important breeding
grounds for various species of sea turtles (Ayissi 2000 ;
Ayissi et al. 2006a , b ).
Cameroon is considered to have abundant offshore nat-
ural gas resources. The country's petroleum reserves are
located offshore in the Rio-del-Rey basin, offshore and
onshore in the Douala and Kribi-Campo basins, and
onshore in the Logone-Birni basin in the northern part of the
country. Cameroon's only refinery, which is located in the
port city of Limbe, had a capacity to produce 45,000 barrels
per day (Newman 2006 ). Tankers, tugboats and other sup-
porting vessels contribute to the heavy vessel traffic around
Limbe. Evidence of the hydrocarbon exploration and pro-
duction
southern shores of the Cameroon Delta, we found consid-
erable quantities of a tar-like substance (a heavy hydro-
carbon fraction) that contaminates the sandy beaches,
apparently related to Cameroon's single most important
shipping lane which leads to the port of Douala. Locals
indicated that the fisher's community of Bolondo had
shrunk over the past decade as fishers moved out, blaming
declining fish catches. An earlier gravel road that connected
Bolondo with Mouanko, no longer maintained, has been
reclaimed by the forest. Hence, access to Bolondo is by sea
or motorbikes which drive along the beach at low tide.
North of the Ntem estuary (Campo), hydrocarbon pollution
was seen dispersed through the upper sand layers at several
sites along the shore. However, locals claimed pollution had
improved from the 1990-2000 period when major timber
exploitation along the river transported logs by tugboats
down the Ntem River and out to cargo ships anchored in
deeper water. The river and estuary was then highly
degraded by hydrocarbons but, allegedly since timber has
been transported by road, water quality had improved. No
documentation was found on this subject.
• Discarded nets
On open shores and around ports, we encountered
important quantities of various types of abandoned, lost or
discarded nets, both monofilament and multifilament. Long
after, fishing gear is lost or abandoned at sea by fishers, it
continues to ensnare fishes (so-called ghost fishing) and thus
harms the marine environment. The drifting gear also causes
entanglements of sea turtles and marine mammals (Mac
Fadyen et al. 2009 ). A nationwide awareness campaign
might help reduce abandoning of damaged nets and urge
fishers to dispose of them on land and/or incinerate them.
Alternative uses, disposal methods or recycling should be
explored. Nets also pose a hazard to propellers of vessels,
especially smaller ones. When visiting Youme I village and
spotting discarded nets, our team offered a constructive
recommendation in that sense, surprisingly well received, to
12 fishermen including their chief. Several readily
acknowledged the problem while the chief announced that
they would address it. This spontaneous reaction suggests
that with a carefully planned and implemented nationwide
educational effort, perhaps with some incentives, this serious
environmental problem may not be as intractable as it seems.
• Shipping and port construction
Heavy shipping traffic to and from the Gulf of Guinea
enters the Cameroon delta via deep-water shipping lanes
that lead to the major industrial port of Douala. Concerns
are that this waterway may be linked to hydrocarbon pol-
lution and, inevitably, underwater acoustic pollution. Vessel
collisions are also expected to constitute a significant risk to
the coastal-dwelling population of humpback whales, a
threat that has been documented near several West African
ports, e.g. in Senegal, Guinea, Côte d'Ivoire, Ghana and
industry
are
ubiquitous.
Near
Bolondo,
on
the
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