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

Number of species
State of Saldanha Bay & Langebaan Lagoon 2011
Fish
presented reports since 2008. The species list and abundance of each species caught in Small Bay,
Big Bay and the Lagoon during each of the different surveys are shown in Table 9.1, Table 9.2 &
Table 9.3 respectively. Considering data from all surveys conducted to date, a greater diversity of
species have been captured in Big Bay (27) , slightly fewer in Small Bay (25) with the fewest found in
the Lagoon (19) (Table 9.1, Table 9.2 &
Table 9.3). Species richness was usually highest in Small Bay and varied little over time, although in
2009 & 2010 there was a slight reduction in the number of species caught in Small Bay, this increased
again in 2011 (Figure 9.2). Slightly more variation in the number of species caught over the period of
sampling is apparent for Langebaan lagoon and Big Bay samples with the second most diverse
samples collected from these areas during 2011 (Figure 9.2).
18
1986 1994 2005 2007 2008 2009 2010 2011
16
14
12
10
8
6
2250m 2
7200m 2
3750m 2
5600m 2
4950m 2
4275m 2
5525m 2
5400m 2
6250m 2
10500m 2
5850 m 2
7500m 2
4950m 2
1800m 2
7125m 2
7200m 2
6000m 2
11325m 2 3150 m 2
9000m 2
6150m 2
2925m 2
4
2
0
Figure 9.2.
Small Bay Big Bay Lagoon
Fish species richness during seven seine-net surveys in Saldanha Bay and Langebaan lagoon
conducted over the period 1986-2010. The total area netted in each area and survey is shown.
The actual species composition in the different areas between the surveys does change
substantially between years, but the same ubiquitous species occur in nearly all surveys in the three
areas (Table 9.1, Table 9.2 &
Table 9.3). Within Small Bay, eight species have occurred in all surveys to date, with gurnard
not captured for the first time in 2011, and pipefish only absent in the 2005 sample. Five of the 27
species recorded in Big Bay occurred in all surveys with three more, silversides False Bay klipvis and
elf only absent in one survey each (2007, 1994 and 2009 respectively). Similarly, six of the 19 species
found in the lagoon occurred in all surveys. It appears that Small Bay has the highest proportion of
“resident” species that occur there consistently, whilst a larger proportion of the Big Bay and
Langebaan Lagoon ichthyofauna occur seasonally or sporadically in these areas. Short term
fluctuations in diversity and abundance of near shore sandy beach fish communities with changes in
197
ANCHOR
e n v i r o n m en t a l