State of the Bay Report 2010-Final - Anchor Environmental

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of the most common fish species caught in the three main areas of the system, namely Small Bay, Big Bay and Langebaan lagoon during each survey, were similarly calculated and presented graphically. Figure 10.1. Sampling sites within Saldanha Bay and Langebaan lagoon where seine net hauls were conducted during 2005, 2007, 2008, 2009 and 2010 sampling events, 1: North Bay west, 2: North Bay east, 3:Small craft harbour, 4: Hoedtjiesbaai, 5: Caravan site, 6: Blue water Bay, 7: Sea farm dam, 8: Spreeuwalle, 9: Lynch point, 10: Strandloper, 11: Schaapen Island, 12: Klein Oesterwal, 13: Bottelary, 14: Churchhaven, 15: Kraal aai State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 220
The average abundance of the four most ubiquitous species in the system over all survey years was calculated and plotted for each sampling site. In order to investigate changes in the entire fish community composition between sites and years, multivariate statistical analysis were conducted using the PRIMER software. Fish density data were fourth-root transformed and the Bay- Curtis similarity index was used to create similarity matrices. Relationships between sites and years were represented using multidimensional scaling and these were statistically tested using a one way or nested (sites nested within years) ANOSIM tests. The principal species contributing to dissimilarities between years or sites were identified using the SIMPER routine. 10.3 Results 10.3.1 Description of inter annual trends in fish species diversity At least thirty-six fish species have been recorded in the six seine-net surveys conducted during 1986-87, 1994, 2005, 2007-2010. This is one less than recorded previously as both sand shark species, R annulatus and R. blockii were thought to occur in the area and new research indicates that only the latter species inhabits the Bay and lagoon (Dunn & Schultz in prep.). During recent surveys three different species of goby of the genus Caffrogobius, namely: C. nudiceps, C. gilchristi and C. caffer have been identified. Due to the uncertainty surrounding identification of these species in earlier surveys, they have been grouped at the generic level for data presented in this report. 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 Figure 10.3, Table 10.1 & Table 10.2 respectively. Considering data from all surveys combined, a similar number of species have been captured in Big Bay (26) and Small Bay (26) with slightly fewer found in the Lagoon (19) (Figure 10.3, Table 10.1 & Table 10.2). 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 (Figure 10.2). Little variation in the number of species caught over the period of sampling is apparent for Langebaan lagoon and the decrease in the number of species caught in Big Bay between 2008 & 2009 noted in last year’s report appears more a result of increased diversity in 2008 catches as all the other annual surveys in Big Bay recorded similar number of species in catches (Figure 10.2). The actual species composition in the different areas between the five surveys did, however change substantially (Figure 10.3, Table 10.1 & Table 10.2). Despite the small decrease in species caught in Small Bay during the 2009 and 2010 sampling surveys, the same nine occurred in all surveys. For the first time in 2010, the Knysna sand goby was found in hauls made in Small Bay at both the campsite and Blue Water Bay sites. Five of the 25 species recorded in Big Bay occurred in all surveys with two more, silversides and elf only absent in one survey each (2007 and 2009 respectively). Similarly, only 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. This is probably related to the greater temporal variation in oceanographic conditions in Big Bay and Langebaan Lagoon than in Small Bay and to differences in habitat type. Short term fluctuations in diversity and abundance of nearshore sandy beach fish communities with changes in oceanographic conditions are the norm rather than the exception (see for e.g. Clark 1994). In the earlier surveys (1994-2008), average species richness and abundance (all species combined) was usually highest in Small Bay and lowest in Big Bay (Figure 10.2, Figure 10.4). Although this pattern still holds in the 2009 and 2010 surveys, with the average fish density in Small Bay still double that recorded for Big Bay, similar or greater average abundance was recorded in the Lagoon samples (Figure 10.4). This was mostly a result of some very large harder catches at two of the lagoon sites (Schaapen Island and Bottelary) and is simply an indication of the high variability in surf zone fish densities that will be recorded when shoaling species are part of the fish assemblage State of the Bay 2010: Saldanha Bay and Langebaan Lagoon 221
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State of the Bay 2010: Saldanha Bay
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TABLE OF CONTENTS Anchor Environmen
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11 BIRDS 234 Anchor Environmental 1
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LIST OF FIGURES Anchor Environmenta
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Anchor Environmental Figure 4.27. O
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Anchor Environmental Figure 7.3. Ch
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Anchor Environmental Figure 9.10. C
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Anchor Environmental Figure 12.1. N
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Anchor Environmental samples were c
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EXECUTIVE SUMMARY Anchor Environmen
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Anchor Environmental matter in the
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Anchor Environmental considered mos
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Anchor Environmental again in 2004,
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Anchor Environmental Populations of
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GLOSSARY Alien species An introduce
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1 INTRODUCTION Anchor Environmental
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2 STRUCTURE OF THIS REPORT Anchor E
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Anchor Environmental complicates ma
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Anchor Environmental observed deter
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Anchor Environmental 4 ACTIVITIES A
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Fish factories Small craft harbour
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Anchor Environmental Aerial photogr
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Anchor Environmental interferes wit
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Anchor Environmental Figure 4.7. Nu
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o Decrease in oxygen concentrations
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Anchor Environmental Upgrades to th
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Anchor Environmental Figure 4.9. A)
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Anchor Environmental (possibly link
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Anchor Environmental Prestedge Reti
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Anchor Environmental the constructi
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Number and types of vessels enterin
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Anchor Environmental is contained b
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Anchor Environmental include the be
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o 33 3’S o 33 10’S Saldanha Bay
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Anchor Environmental (1956) UNDER T
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Free ACtive Chlorine (mg/l) Amonia
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Faecal coliforms (org/100 ml) Chemi
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4.3.7 Storm water Anchor Environmen
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Anchor Environmental sites (concent
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Anchor Environmental Discharges fro
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Anchor Environmental Table 4.9. Det
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5 WATER QUALITY Anchor Environmenta
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Anchor Environmental Stander (1977)
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Anchor Environmental coast, result
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Anchor Environmental Construction o
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Anchor Environmental Table 5.2. Per
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Counts per 100ml of sample Counts p
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Counts per 100ml of sample 10000 10
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5.6 Trace Metal Contaminants in the
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Lead(mg/kg) Mercury (mg/kg) Cadmium
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6 SEDIMENTS 6.1 Sediment particle s
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6.1.2 Sediment Particle size result
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100% 90% 80% 70% 60% 50% 40% 30% 20
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% POC 18 16 14 12 10 8 6 4 2 0 % PO
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Percentage Percentage 1.8 1.6 1.4 1
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o 33 3’S o 33 10’S Yacht Club B
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Figure 6.12. Variation in the conce
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The concentrations of metals in sed
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concentrations are 56 and 29 times
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threshold of 1.2 mg/kg established
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Cadmium (mg/kg) 8 7 6 5 4 3 2 1 0 C
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Copper (mg/kg) 45 40 35 30 25 20 15
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16000 14000 12000 10000 8000 6000 4
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In summary, elevated trace metal co
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6.5 Summary of sediment health stat
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7.1 Long term changes in seagrass i
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7.2 Long term changes in Saltmarshe
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Figure 8.1. Benthic macrofauna samp
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Table 8.1. Depth at each of the sit
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these species usually provide the l
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(clustering of similar groups) (Meg
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The Big Bay samples BB 25 and BB29
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2007/08 dredging. Other signs of th
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Wet mass per m² Wet mass per m² 4
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Big Bay Crustaceans and polychaetes
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Page 205 and 206: Percentage Cover 80 70 60 50 40 30
Page 207 and 208: Evenness Shannon Wiener 0.9 0.8 0.7
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Page 247 and 248: 11.3 Birds of Langebaan Lagoon 11.3
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Anchor Environmental Tunley KL, Att
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State of the Bay Report 2010-Final - Anchor Environmental

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