Aerial and Acoustic Surveys for Mackerel - BioSonics, Inc

In June, mackerel stock distribution was governed by hydrological conditions in the region (Figure 5.1.2.2). Small
schools were found at depths 10 to 25 m in Eastern and South-Eastern part of the research area. Temperature of the
water in above areas was higher than 9°C. In the Western part of the research area, where isothermal line of 9°C was
very close to the surface, echograms from echo-sounder, showed no or very small number of mackerel schools.
Measured Nautical Area Scattering Coefficients (S A ) for 5 mile intervals varied from 1 to 30 (m 2 /nmi 2 ). Maximal
mackerel schools were registered in position 65°45’N, 4°W. Low NASCs resulted from the fact that most of the fish
avoided the vessel. Therefore, acoustic estimation of mackerel was not calculated.
The trawl method was used for estimating the biomass and distribution of mackerel schools. During the survey, the
vessel made a total of 31 trawl hauls. Mean length of fish and mean weight of mackerel were 36.06 cm, 526 g
accordingly. A preliminary result gave a biomass estimate of 720 000 tones.
During the survey, the RV “Smolensk” worked in conjunction with the research aircraft under the joint program (see
above).
69°
108 109 110
148 149 150 151
68°
113
155
112
154
153
111
152
114 115 116117
156 157 158 159 160 161 162 163 164 165 166
67°
173
172
121
171
170
120
169
119
168
118
167
122 123 124 125
174 175 176 177 178
129
128
127
126
66°
184
183
182
181
180
179
130 131 132 133
185 186 187 188 189 190 191 192 193
135
134
197
136
196
195
194
65°
137 138
198 199
- CTD
- Ï åë. òðàë
64°
-8° -6° -4° -2° 0° 2° 4°
Figure 5.1.2.1. Survey tracks, trawl and hydrographic stations RV “Smolensk”.
PGAAM Report 2004 11