A total of 640 and 342 hauls, with bottom and the pelagic trawl respectively, were made during the whole programme in Angola. The corresponding mean catches were 860 and 797 kg/hour.
The shelf
Restricted to the shelf between 10 and 200m, 504 and 296 pelagic hauls were made. The corresponding mean catch rates on the shelf were 840 and 740 kg/hour.
Table 11 shows the catches of the main families, distributed by 6 size classes, from no catch to >1000 kg/hour, the mean catch and the family's share of the total catch included. High catch rates were obtained especially for carangids, grunts and sparids. All hauls, both random hauls for swept-area calculations, and aimed hauls for identification purposes are included in this analysis. Similar analysis from commercial fishing activities would give catch distributions shifted to upper classes compared to those given in the table. The data will however give information on the relative strength of the different species groups and their distributional pattern with relevance to commercial fishing.
| Catch group kg/h | A | B | C | D | E | F | Mean catch | % of total catch |
|---|---|---|---|---|---|---|---|---|
| 0–30 | 1–30 | 30–100 | 100–300 | 300–1000 | > 1000 | |||
| % | % | % | % | % | % | Kg/h | % | |
| Carangidae | 24 | 32 | 18 | 13 | 7 | 6 | 213 | 26 |
| Pomadasyidae | 44 | 18 | 13 | 10 | 9 | 6 | 183 | 22 |
| Sparidae | 23 | 23 | 22 | 21 | 9 | 2 | 131 | 16 |
| Sciaenidae | 45 | 23 | 18 | 10 | 4 | 0 | 50 | 6 |
| Trichiuridae | 53 | 26 | 14 | 4 | 2 | 1 | 38 | 5 |
| Acropomidae | 90 | 3 | 4 | 2 | 1 | 0 | 16 | 2 |
| Merluccidae | 92 | 3 | 2 | 1 | 2 | 0 | 15 | 2 |
| Polynemidae | 76 | 12 | 8 | 3 | 1 | 0 | 12 | 2 |
| Albulidae | 83 | 10 | 4 | 2 | 1 | 0 | 9 | 1 |
| Balistidae | 84 | 12 | 2 | 1 | 1 | 0 | 10 | 1 |
| Clupeidae | 75 | 18 | 5 | 2 | 0 | 0 | 9 | 1 |
| Rays | 56 | 36 | 6 | 2 | 0 | 0 | 11 | 1 |
| Serranidae | 77 | 16 | 7 | 0 | 0 | 0 | 6 | 1 |
| Sharks | 78 | 16 | 5 | 1 | 0 | 0 | 8 | 1 |
| Soleidae | 89 | 10 | 1 | 0 | 0 | 0 | 7 | 1 |
| Sphyraenidae | 73 | 19 | 7 | 1 | 0 | 0 | 6 | 1 |
| Squids | 59 | 34 | 6 | 1 | 0 | 0 | 10 | 1 |
| Triglidae | 75 | 19 | 4 | 2 | 0 | 0 | 7 | 1 |
| Zeiidae | 76 | 21 | 2 | 1 | 0 | 0 | 6 | 1 |
| Other fish | 94 | 11 | ||||||
| Mean of total catches | 841 | |||||||
Deep water slope
Based on our random trawling by bottom depth strata we have estimated the expected mean catch rates on the deep water slope from Benguela to Cabinda with a 30 m wide shrimp trawl as follows (in kg/hour, speed 3 knots):
| Bottom depth zone | ||||
|---|---|---|---|---|
| Species | 200–300 | 300–400 | 400–500 | 500–600 |
| Merluccius polli | 145 | 735 | 950 | 120 |
| Chlorophthalmidae | 170 | 88 | 0 | 0 |
| Nematocarcinus africanus | 0 | 100 | 180 | 60 |
| Aristeus varidens | 5 | 10 | 115 | 10 |
| Parapenaeus longirostris | 29 | 20 | 10 | 0 |
| Squid | 5 | 5 | 30 | 10 |
| Whole catch | 705 | 1460 | 1760 | 510 |
| Commercial shrimp | 34 | 30 | 125 | 10 |
As shown in Section 3.2.4 the mean densities in the bottom depth range 200–400m are higher in area 3, compared to area 4. Separate catch rates for the two regions would give somewhat higher estimates for region 3, compared to the figures above, while region 4 would lie somewhat below in the depth zones concerned.
Generally shrimps are known to show aggregations by quite narrow depth zones, and adjusting the fishing activities to such limits would give higher catches than indicated above. Our fishing stations were however distributed over wide depth intervals, and no attempts were made to select the depth zone of highest shrimp abundance. Commercial rates must therefore be expected to lie considerably higher than our results.
Figure 1. Type of bottom over the Angolan shelf as assessed from echo diagrams. 1) Even flat bottom, 2) Uneven bottom, 3) Rough bottom and 4) Steep slope.
Figure 2. Temperature, salinity and oxygen in hydrographic profiles over the Angolan shelf in February 1985.
Figure 3. Temperature, salinity and oxygen in hydrographic profiles over the Angolab shelf in August - September 1985.
Figure 4. Distribution of pelagic fish type 1 in Regions 1 and 2 in each of the six surveys.
Figure 5a. Distribution of pelagic fish type 1 in Regions 3 and 4 in Surveys 1 – 3.
Figure 5b. Distribution of pelagic fish type 1 in Regions 3 and 4 in Surveys 4 – 6.
Figure 6. Pooled size distributions of samples of round sardinella, Regions 3 and 4 by surveys.
Figure 7. Pooled size distributions of samples of flat sardinella, Regions 3 and 4 by surveys.
Figure 8. Distribution of pelagic fish type 2 in Regions 1 and 2 in each of the six surveys.
Figure 9a. Distribution of pelagic fish type 2 in Regions 3 and 4 in Surveys 1 – 3.
Figure 9b. Distribution of pelagic fish type 2 in Regions 3 and 4 in Surveys 4 – 6.
Figure 10. Pooled size distributions of samples of Cape horse mackrel in Region 1.
Figure 11. Pooled size distributions of samples of Cunene horse mackrel, all regions by surveys.
Figure 12. Pooled size distributions of samples of bumper, lookdown, false scad, barracudas and Benguela hake in Region 3 and 4 and all surveys.
ACOUSTIC INSTRUMENTS
Two SIMRAD scientific echo sounders, 38 and 12o kHz, were used during the survey for estimation of fish density. In addition an ES 400 split beam sounder was used.
| INSTRUMENT SETTINGS | |||
|---|---|---|---|
| EK 400/38 | EK 400/120 | ES 400 | |
| Range | 0–100 or 0–250 | 0–100 | 0–25 to 0–250 |
| Transm. | High (5000. W NOM) | High (1250 W NOM) | EK/ES adapter |
| Bandwidth | 3.3 kHz | 3.3 kHz | 3.5 kHz |
| Pulselength | 1 ms | 1 ms | 1 ms |
| TVG | 20 log R | 20 log R | 40 log R |
| Attenuator | 20 dB | 0 | Fixed |
| Rec. gain | 7 | 5 | |
| Transducer | 8° × 8° ceramic or split beam | Ceramic 10 cm circular | Split beam 10° |
| Presentation mode: Compensated | |||
EK 400/38 was coupled to the digital integrator QD and to one analog integrator QM.
| QD settings: | Gain 30 dB, Threshold 10 to 26 mv. |
| QM settings: | Gain 20 dB × 10. Threshold 10. |
EK 400/120 was coupled to the other QM integrator. Gain 10 dB × 10. Threshold 0.
ES 400 was connected to an Epson printer for hardcopy of the size distribution diagram (histogram).
Calibration on standard copper sphere. (Porto Alexandre 10.08.1985).
| EK 400/38: | SL + VR = 140.8 dB (Transd. 8° × 8°) |
| EK 400/38-ES: | SL + VR = 137.3 dB (Split beam transm.) |
Sonar
An ST sonar was used to detect fish schools close to the surface. Recorder range 0–250 m.
Calibration of instruments “Dr. Fridtjof Nansen” 1985–86
| Locality | Transducer | SL+VR | Instr.constant |
|---|---|---|---|
| 3/2/85, B.d.Tigres | 30×30 | 140,7 | |
| 28/4/85 " " | 30×30 | 140,8 | 0,94 |
| 29/4/85 " " | ES | 137,3 | 2,02 |
| 10/8/85 P.Alex. | ES | 137,3 | |
| 8/11/85 B.d.Tigres | ES | 137,1 | 2,28 |
| " " | 30×30 | 140,8 | 0,94 |
| 24/1/86 B.d.Tigres | ES | 137,0 | 2,08 |
| " " | 30×30 | 141,0 | 0,85 |
| 26/4/85 " " | ES | 136,6 | 2,41 |
Cruise 1.
From IMR Bergen:
G.Saetersdal up to 15/2 ( cruise leader)
T.Stroemme from 16/2 "
S.Myklevoll
Ø.Skaatun
I.Svellingen (instrument chief)
T.Haugland
From CIP, Luanda:
Luis Anapas Pereira
Manuel Jose Fernandes
Maria Odete Pedro Trigo
Mario Fortunato Rafael
Antonio Pacheco Neto
From FAO:
Gabriella Bianchi
Cruise 2.
From IMR Bergen:
I. Svellingen up to 15/5 (cruise leader)
O. Haldorson (cruise leader from 15/5)
K. Pittman
H. Ullabust (from 15/5)
T. Haugland (instrument chief)
From CIP, Luanda:
Luis Anapas Pereira
Mario Fortunato Rafael
Francisco Almeida
Cruise 3.
From IMR, Bergen:
G. Sætersdal (up to 28 August, cruise leader)
I. Svellingen (Instrument chief and cruise leader from 28 August)
S. Mykievoll (till 28 August)
J.H. Vølstad
From CIP:
Tomantima Mbengwi
Alfonso. Leelo
Cruise 4.
From IMR, Bergen:
T. Strømme (cruise leader)
K. Hansen
K. Pittman
A. Roald
E. Øvretveit
From CIP, Luanda:
Victória Barros Neto (to 26 Nov)
Antonio Pacheco Neto (to 26 Nov)
Isaac Miguel Sebastiao (to 26 Nov)
Tomatima M'Bengui (from 27 Nov)
Francisco de Almeida (from 27 Nov)
Cruise 5.
| G. Swteradul | Cruise leader | (-22/2) | IMR |
| I. Svellingen | " " | (22/2-10/3) | IMR |
| A. Abella | FAO | ||
| J. Vølstad | IMR | ||
| T. Haugland | IMR | ||
| E. Molvær | IMR | ||
| A. De Fontes | CIP | ||
| A. Pacheco Nato | 14/2 | CIP | |
| Sra. D. Cardoso | 14/2 | University, Luanda | |
| Tomantima M'Bengui | 15/2 | CIP | |
| Sra. I. DeJesus | 15/2 | CIP | |
| I. Miguel Sebastiao | 14/2 | CIP |
Cruise 6.
From IMR, Bergen:
T. Strømme (cruise leader to 15 May)
S. Myklevoll (cruse leader from 18 May)
H. Ullebust
R. Edwards
T. Haugland
E. Molvær
From CIP, Luanda:
19 April - 12 May
Antonio de Fontes Pereira
Isaac Miguel Sebastiao
Bazika Bomba
12 May - 7 June
Tomatima M'Bengui
Antonio Pacheco Neto
Pedro Ponzo
| Scientific name | FAO English name | Local name* |
|---|---|---|
| ACROPOMATIDAE | ||
| Synagrops microlepis | Thinlip splitfin | Dentinho |
| ALBULIDAE | ||
| Pterothrissus belloci | Longfin bonefish | |
| BALISTIDAE | ||
| Balistes capriscus | Grey triggerfish | Cangulo, Peixe-porco |
| CARANGIDAE | ||
| Caranx spp. | Jacks | Xareu |
| Chloroscombrus chrysurus | Atlantic bumper | Cambele, Camalesso |
| Decapterus rhonchus | False scad | Charro-amarelo |
| Selene dorsalis | African lookdown | Condombolo, Peixe-prata |
| Trachurus capensis | Cape horse mackerel | Carapau, Chicharro etc. |
| Trachurus trecae | Cunene horse mackerel | Carapau do Cunene, Charro, etc. |
| CHLOROPHTHALMIDAE | ||
| Chlorophthalmus spp. | Atlantic greeneye | |
| CLUPEIDAE | ||
| Sardinella aurita | Round sardinella | Lombuda, Sardinela, Sardinha etc. |
| Sardinella maderensis | Madeiran sardinella, Flat sardinella | Palheta, Sardinela etc. |
| Sardinops ocellata | Southern African Pilchard | Sardinha-do-reino, Arinca do Cabo |
| MERLUCCIIDAE | ||
| Merluccius capensis | Cape hake | Pescada-do-Cabo |
| Merluccius polli | Benguela hake | Pescada-de-Angola |
| POLYNEMIDAE | ||
| Galeoides decadactylus | Lesser African threadfin | Barbudo |
| POMADASYIDAE | ||
| Brachydeuterus auritus | Bigeye grunt | Colo-colo, Camutungo |
| Pomadasys incisus | Bastard grunt | Bolo-bolo, Roncador |
| SCIAENIDAE | ||
| Atractoscion aequidens | African weakfish | Corvina-de-boca-amarela |
| Argyrosomus spp. | Southern meagre | Corvina-legítima |
| Pseudotholitus senegalensis | Cassava croaker | Corvina-branca, Guemba |
| Pseudotholitus typus | Longneck croaker | Corvina-branca |
| Umbrina canariensis | Canary drum | Calafate, Corvina |
| SCOMBRIDAE | ||
| Scomber japonicus | Chub mackerel | Cavala, Sarda |
| Scomberomorus tritor | West African Spanish mackerel | Peixe-serra, Serra |
| SOLEIDAE | ||
| Dicologoglossa cuneata | Wedge sole | Linguado |
| SPARIDAE | ||
| Dentex angolensis | Angola dentex | Dentão |
| Dentex canariensis | Canary dentex | Dentão-quissanga, Pargo |
| Dentex congoensis | Congo dentex | Dentão |
| Dentex gibbosus | Pink dentex | Capatão-de-bandeira, Pargo-boi |
| Dentex macrophthalmus | Large-eye dentex | Cachucho, Breca |
| Diplodus sargus | White seabream (Cape) | Sargo-mariquita |
| Pagellus bellottii | Red pandora | Tico-tico, Bica, Breca |
| Sparus caeruleostictus | Bluespotted seabream | Pargo-ruço |
| TRICHIURIDAE | ||
| Trichiurus lepturus | Largehead hairtail | Lírio, Espada |
| SHRIMPS | ||
| Aristeus varidens | Striped red shrimp | |
| Nematocarcinus africanus | African spider shrimp | |
| Parapenaeus longirostris | Deepwater rose shrimp |
* From Sanchez, Peixes de Angola
| Annex 1. | Course tracks with fishing- and hydrographic |
| stations. | |
| Annex 2. | Records of fishing stations. |
| Annex 3. | Catch data by species with reference to fishing |
| stations. Catch per hour in brackets. | |
| Annex 4. | Processed length data by species and samples. |
| Annex 5. | Length frequency distributions by species and |
| samples. | |
| Annex 6. | Pooled length frequency diagrams by species, |
| regions and surveys. | |
| Annex 7. | Summary tables of catch compositions by species |
| or family groupings by regions and surveys and | |
| total data for all pelagic hauls, shelf bottom | |
| trawl, and deep water hauls separately. | |
| Annex 8. | List of all species caught, Latin and English |
| names. |
