State of the Bay Report 2011-Final.pdf - Anchor Environmental

State of Saldanha Bay & Langebaan Lagoon 2011
Recommendations
The intertidal transects (and the quadrats along those transects) that were established in the
survey initiated in 2005 should continue to be monitored annually for another year but could then
be reduced in frequency to once every five years thereafter.
12.6 Fish
The current status of fish and fisheries within Saldanha Bay-Langebaan appears satisfactory. Long
term monitoring by means of experimental seine-netting has revealed no statistically significant,
negative trends since fish sampling began in 1986-87. It is likely that the major changes reflected in
the macrobenthos and concurrent reduction in the extent of eelgrass (Zostera capensis) in
Langebaan lagoon since the 1970’s (see §1 for more details on this) did have a dramatic impact on
the ichthyofauna. These changes would have caused ecosystem wide effects that included changes
in both the physical habitat (extent of eel grass, sediment structure etc) and food sources
(reductions in bivalves and polychaetes and increases in sand prawns) available to fish. This would
have likely favoured some fish species and had a negative impact on others. The abundance of two
species that tend to favour aquatic macrophyte habitats namely pipefish and super klipvis, does
appear to have declined in Langebaan lagoon since the 1986/87 sampling. However, the major
changes that probably occurred in the system would have taken place at the same time that the
changes in benthos and eelgrass took place (i.e. 1970s-1980s), and as no fish sampling took place
over this period, these are not reflected in the available data which only exists from the late 1980’s.
Fish sampling surveys should be conducted annually at the same sites selected during the
2005 study for the next two years but could then be reduced in frequency to once every five years
thereafter. This sampling should be confined to the same seasonal period each year for comparative
purposes. Additional data on daily catch records from anglers (West Coast National Park and fishing
clubs) is now being collected by Marine and Coastal Management. This initiative should be strongly
supported as it will provide invaluable information that will contribute to an improved
understanding of the overall health of fish populations in the Bay.
12.7 Birds
An alarming decrease in the abundance of both resident and migrant waders utilising Langebaan
Lagoon is evident over the past decade and is believed to be a function of increased human
utilisation of the area and possible reduction in available food. Similar declines are evident in some
bird species breeding on the offshore islands in the Bay. This is believed to be a function of
reductions in their food supply (largely pelagic fish e.g. pilchard) outside of the Bay and human
disturbance within the Bay. Encouraging increases in numbers of African Black Oystercatchers have
been observed on some of the islands in the Bay and is believed to be related to the proliferation of
alien mussels on rocky shores in the area, which constitute an important food source for these birds.
Populations of key bird species are currently monitored annually on the offshore islands
within the Saldanha Bay area, whilst bird populations in Langebaan Lagoon are monitored twice per
annum. These bird counts are conducted as part of an ongoing monitoring programme, managed by
the Avian Demography Unit of the University of Cape Town and Oceans and Coasts (Department of
Environmental Affairs). The data from these surveys should be regularly obtained from these
organisations and examined on an annual basis.
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