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

More documents

Recommendations

Info

Density (no.m -2 ) Density (no.m -2 ) CPUE (fish.angler-hour -1 ) CPUE (kg.crew-hour -1 ) State of Saldanha Bay & Langebaan Lagoon 2011 Fish White stumpnose abundance and Boat CPUE 2.0 1 1.5 Average density seine survey Average CPUE boats (+ 2 years) 0.9 0.8 0.7 0.6 1.0 0.5 0.4 0.5 0.3 0.2 0.1 0.0 2005 (2006_7) 2006 (2007_8) 2007 (2008_9) 2008 (2009_10) 2009(2010_11) 2010(2011_12) 2011(2012_13) 0 Year White stumpnose abundance and Commercial boat CPUE 2.0 1.4 1.5 Average density seine survey Average CPUE commercial boats 1.2 1 1.0 0.8 0.6 0.5 0.4 0.2 0.0 2005 (2006_7) 2006 (2007_8) 2007 (2008_9) 2008 (2009_10) 2009(2010_11) 2010(2011_12) 2011(2012_13) 0 Year Figure 9.14. Comparison between the average annual juvenile white stumpnose abundance as estimated from seine net surveys and the observed boat (inspections) and commercial (catch returns) catch-per-unit-effort two years later 216 ANCHOR e n v i r o n m en t a l
State of Saldanha Bay & Langebaan Lagoon 2011 Fish 9.4 Conclusion The current status of fish and fisheries within Saldanha Bay-Langebaan appears satisfactory. Long term monitoring by means of experimental seine-netting has revealed statistically significant differences in fish community structure between different sampling sites within years and between sampling years. A consistent long-term negative trend, since fish sampling began in 1986-87 has however, not been detected. In fact fish abundance of key species at sites within or in close proximity to the Marine Protected Area appears to be increasing. This reflects natural and human induced impacts on the adult population size, recruitment success and use of the near shore habitat by fish species; but may also be a result of the benefits of protection from exploitation and reduced disturbance at some sites due to the presence of the Langebaan MPA. Certainly, the study by Kerwath et al. (2009) demonstrated the benefits of the MPA for white stumpnose, and the protection of harders from net fishing in the MPA undoubtedly benefits this stock in the larger Bay area. The 2011 sampling event recorded remarkably good harder recruitment throughout the Saldanha Bay-Langebaan system, whilst the estimated abundance of other key species such as white stumpnose, gobies and silversides within Big Bay and Langebaan Lagoon compare favourably with data from earlier surveys. In Small Bay, however, there were clear reductions in the abundance of key species (with the exception of harders), with the lowest yet recorded black tail density and the second lowest white stumpnose density to date. This follows the trend observed in the 2010 report and it is somewhat concerning that the estimated abundance of some key species is decreasing in the areas of maximum anthropogenic disturbance within Small Bay, whilst they are increasing in other less disturbed areas of Big Bay and Langebaan lagoon. In the data set collected to date, the average density of commercially important fish such as white stumpnose was much higher at Small Bay sites compared to Big Bay and Lagoon sites (although the opposite trend was observed in 2011). Indeed the average white stumpnose density calculated from all seine net surveys to date is 0.8 fish.m -2 in Small Bay, compared with 0.1 fish.m -2 in Big Bay and 0.05 fish.m -2 in Langebaan lagoon. The juveniles of other species were similarly more abundant in Small Bay. This gives an indication of the importance of Small Bay as a nursery habitat for the fish species that support the large and growing fisheries throughout the Bay. The monetary value of the recreational fishery in Saldanha-Langebaan should not be regarded as regionally insignificant as a lot of the expenditure associated with recreational angling is taking place within Langebaan and Saldanha itself. Furthermore the popular white stumpnose fishery is undoubtedly a major draw card to the area and has probably contributed significantly to the residential property market growth the region has experienced. The value of Small Bay as a fish nursery and the economic value of the resultant fisheries should not be disregarded when considering the environmental impacts of the proposed future industrial developments within Small Bay. The monitoring record from the annual seine net surveys will prove increasingly valuable in assessing and mitigating the impacts of future developments on the regions ichthyofauna. Extending the seine net monitoring record would also facilitate analysis of the relationship between recruitment to the surfzone nursery habitat and future catches in the fisheries. Should this relationship prove robust and quantifiable, this will allow for adaptive management of the fisheries in the future as fishing effort continues to increase and at some point fishing mortality will need to be contained, if the fisheries are to remain sustainable. 217 ANCHOR e n v i r o n m en t a l
Page 1:
Saldanha Bay and Langebaan Lagoon:
Page 5 and 6:
State of Saldanha Bay & Langebaan L
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Jul-05 Sep-05 Nov-05 Jan-06 Mar-06
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Average Daily Flow (m3/day) Apr-03
Page 73 and 74:
Page 75 and 76:
Average daily flow (m 3 /day) Faeca
Page 77 and 78:
Ammonia Nitrogen (mg/l as N) Nitrat
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Volume of Effluent (kL) Jan-01 Mar-
Page 87 and 88:
Mussels Oysters Abalone Scallops Re
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Cadmium (mg/kg) Lead(mg/kg) Mercury
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Beach Width (m) State of Saldanha B
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Copper (mg/kg) Copper (mg/kg) Coppe
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
No. saltmarsh patches Saltmarsh are
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Top 10 species contributing to simi
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Proportion of total number of indiv
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198: State of Saldanha Bay & Langebaan L
Page 209 and 210: Afrolittorina knysnaensis (no/0.5 m
Page 211 and 212: Similarity Iron Ore Jetty Iron Ore
Page 215 and 216: Lynch Point State of Saldanha Bay &
Page 217 and 218: Dive School Jetty Schaapen East Sch
Page 221 and 222: High 05 High 08 High 09 High 10 Hig
Page 229 and 230: Number of species State of Saldanha
Page 235 and 236: Fish abundance (No.m -2 ) State of
Page 247: State of Saldanha Bay & Langebaan L
Page 253 and 254: Number of breeding pairs State of S
Page 265 and 266: Number of birds 1976 1977 1978 1979
Page 275 and 276: No. sites Abundance (no. ind. m -2
Page 299 and 300:
Page 301 and 302:
Page 303:
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?