Fisheries - Enviro Dynamics Namibia

F I S H E R I E S , M A M M A L S A N D S E A B I R D S S P E C I A L I S T S T U D Y
8.2 IMPACT 2: THE IMPACT OF THE MINING OPERATIONS ON THE ECOSYSTEM
(TROPHIC INTERACTIONS)
As commercial data are not “independent”, we used survey data as the basis for estimating the
approximate spatial distribution of the main commercial fish species. These species are used as
biological indicators of the main fish components of the ecosystem, in particular their distribution
reflects the likely trophic structure of the ecosystem in the vicinity of the MLA. Note that trophic
modelling of the Benguela ecosystem has been done although the specific application to Namibia
and the MLA in particular can only be inferred from these broad studies (Shannon, 1986). Note
also that trophic modelling is inclusive of top predators as well as species lower in the food chain
including benthic organisms removed with the substrate in the dredging process. We have
enquired regarding the status of trophic marine modelling in Namibia and the BCC but have as
yet no conclusive models or data on which to give a more informed assessment of the impacts on
the ecosystem. Equally this problem applies to all aspects of the Benguela ecosystem including
fishing and other anthropogenic effects.
The survey data (see Table 3) were analysed by visually examining the maps (Figures 27 – 38). To
determine the likely impact of mining we used it as an indicator for the distribution and
abundance of each species relative to their proximity to the MLA. The unit or index applied is
simply the cumulative catch of a particular species in the different surveys.
This rough assessment is summarized in Table 3 - i.e. the likelihood of the species listed being
found (and impacted) in the actual mining locations within the MLA. The significance of the
impact is summarised in Table 4. Note also that our data pertain only to the species recorded in
the surveys we had access to. We are aware that many more species are found in the MLA, but
that there is no data or records of these we are aware of (excluding the benthic sampling
undertaken for the phosphate pre-studies). As such the data we have had access to can only be
considered an “indicator” with no direct inference to all species potentially impacted by the
proposed dredging.
Table 3. Visually assessment of the potential impacts of phosphate mining on ecologically important
commercial fish species
Dataset Dates Species
MLA
(SP-1, SP-2 and
SP-3)
Horse mackerel No
Snoek (Thyrsites atun) No
Hake survey data 1995-2010
Bearded Goby (Sufflogobius bibarbatus)
Monk
Yes
Yes
Hake Yes
Sole (Austroglossus microlepis) Yes
Monk No
Monk survey data 2007-2010
Goby
Orange roughy (Hoplostethus atlanticus)
No
No
Sole No
Small pelagic survey data 2002-2011
Horse mackerel, anchovy, sardine and
round herring
No
Hake, monk and small pelagics
survey data combined
1995-2011 All species counted per sample station Yes
Final Report
Namibian Marine Phosphate (Pty) Ltd.
Page 59