Annexes

Annex I. Participating scientific staff
Annex II. Records of fishing operations
Annex III. Results from length measurements
Annex IV. List of species
Annex V. Equipment and methods

Annex I. Participating scientific staff

From the Institute of Marine Research, Bergen:

Mr. T. Strømme (cruise leader)
Mr. H. Gjøsæter (biologist)
Mr. K. Strømsnes (research technichian)
Mr. H.P. Knutsen (instrument chief)
Mr. B. Kvinge (instrument technichian)

Mr. G. Everett (CECAF project leader), Nov 3-8

Miss V. Marques da Silva (biologist) Nov 5-6, Nov 16-27
Mrs. M.H. Vieira (biologist) Nov 28-Dec 1

Mr. G. Beven (fishing master) Nov 5-6, Nov 16-Dec 1

Annex II. Records of fishing operations

Annex II. Records of fishing operations

Annex II. Records of fishing operations (cont. 1)

Annex III. Results from length measurements

FAMILY/SPECIES	STATION	LENGTHS IN SAMPLE
		LOWEST	HIGHEST	MEAN ST.	DEV.	N
CAPROIDAE
Antigonia capros
	379	11.0	16.0	14.2	.8	89
	383	6.5	15.5	13.3	1.9	48
CARANGIDAE
Caranx crysos
	374	41.0	64.0	51.9	6.4	18
	375	43.0	63.0	52.7	6.8	8
Decapterus punctatus
	355	11.5	21.5	18.2	1.8	147
	358	12.5	19.0	14.0	1.0	117
	360	9.0	17.0	11.5	1.3	119
	369	12.5	19.0	14.3	1.1	115
	371	12.0	19.5	15.6	1.5	126
	372	17.5	23.5	21.3	1.1	107
	377	15.0	22.0	17.4	1.1	134
	380	18.0	21.0	19.4	.9	14
	381	19.0	24.0	21.1	1.1	98
	383	18.5	22.0	20.0	1.9	32
	385	8.5	18.0	11.7	2.1	96
	386	13.5	21.5	16.2	1.6	159
	387	10.0	13.5	11.2	.9	100
Decapterus rhonchus
	362	24.0	30.0	26.8	1.2	111
	371	12.0	18.0	15.5	1.8	39
	385	13.0	24.0	15.6	1.4	99
Decapterus macarellus
	350	19.0	32.0	25.2	3.9	100
	351	28.5	32.0	29.9	1.0	23
	352	21.0	33.5	28.0	2.4	53
	357	11.0	22.0	17.4	2.1	97
	371	16.5	27.0	18.7	2.0	82
	377	17.5	21.5	19.5	1.1	20
	380	17.0	28.5	20.1	1.7	150
Selar crumenophthalmus
	348	13.5	17.0	15.3	1.0	32
	357	13.5	17.5	14.7	.9	32
CLUPEIDAE
Sardinella maderensis
	357	12.0	17.0	14.5	1.2	23
	371	16.0	25.0	20.2	3.0	11
	385	17.5	26.0	22.4	1.7	35
LETRINIDAE
Lethrinus atlanticus
	367	35.0	41.0	37.8	2.0	10
LUTJANIDAE
Lutjanidae indet.
	378	41.0	48.0	45.3	2.3	8
MULLIDAE
Pseudupeneus prayensis
	355	13.5	19.5	16.2	1.3	80
	360	12.5	21.5	16.3	1.8	115
	369	14.0	22.0	18.0	1.6	104
	377	10.0	24.0	17.4	2.4	166
	388	16.0	24.5	20.0	2.2	34
POMADASYIDAE
Paraphristipoma sp.
	364	31.0	36.0	33.7	2.0	8
Pomadasys incisus
	388	20.0	24.5	22.3	1.0	41
SERRANIDAE
Cephalopholis taenopsis
	364	39.0	48.0	44.7	3.5	8
SHARKS
Rhizoprionodon acutus
	367	81.0	92.0	87.4	3.7	8
	368	66.0	85.0	80.0	6.7	7
Mustelus mustelus
	363	66.0	97.0	84.7	5.8	35
	367	80.0	96.0	86.4	5.6	16
SPARIDAE
Boops boops
	369	14.0	16.5	15.3	.7	26
	371	13.5	16.0	15.1	.6	26
	379	22.5	27.5	25.1	1.2	70
Lithognathus mormyrus
	355	21.0	30.0	25.8	2.9	14
	388	23.5	29.5	26.5	1.4	55
Pagellus acarne
	369	19.0	22.5	21.1	1.4	12
	377	19.0	31.0	25.2	1.8	122
Spondyliosoma cantharus
	351	36.0	46.0	40.3	5.1	3

Annex IV. List of species

List of species caught with R/V Dr. Fridtjof Nansen off Cape Verde Islands November 1981.

ACANTHURIDAE
	Acanthurus monroviae
ANGUILLIFORMES
BALISTIDAE
	Balistes capriscus
BELONIDAE
	Ablennes hians
BRAMIDAE
	Brama brama
CAPROIDAE
	Antigonia capros
	Capros aper
CARANGIDAE
	Caranx crysos
	Decapterus punctatus
	Decapterus rhonchus
	Decapterus macarellus
	Selar crumenophthalmus
	Seriola carpenteri
	Seriola fasciata
	Trachinotus ovatus
	Trachurus trachurus
	Uraspis secunda
CENTRACHANTIDAE
	Spicara sp.
CLUPEIDAE
	Sardinella maderensis
CONGRIDAE
	Rhechias sp.
DACTYLOPTERIDAE
	Dactylopterus volitans
FISTULARIIDAE
	Fistularia petimba
GEMPYLIDAE
	Gempylus serpens
	Neolatus tripes
	Promenthichthys prometheus
GERREIDAE
	Eucinostomus melanopterus
GONOSTOMATIDAE
	Vinciguerria sp.
HOLOCENTRIDAE
	Adioryx hastatus
LABRIDAE
	Bodianus speciosus
	Xyrichtys novacula
LETRINIDAE
	Lethrinus atlanticus
LUTJANIDAE
MACRORHAMPHOSIDAE
	Macrohamphosus scolopax
MONACANTHIDAE
	Aluterus sp.
	Aluterus punctatus
	Stefanolepis hispidus
MULLIDAE
	Pseudupeneus prayensis
	Lycodontis sp.
MYCTOPHIDAE
NOMEIDAE
	Cubiceps sp.
	Cubiceps gracilis
	Psenes sp.
PARALEPIDIDAE
	Lestidium sp.
POLYNEMIDAE
	Galeoides decadactylus
POMADASYIDAE
	Paraphristipoma sp.
	Paraphristipoma octolineatum
	Pomadasys incisus
	Pomadasys peroteti
PRIACANTHIDAE
	Priacanthus arenatus
SALPS
SCARIDAE
	Sparisoma rubripinne
SCORPAENIDAE
SERRANIDAE
	Cephalopholis taenopsis
	Epinephelus guaza
	Epinephelus alexandrinus
SHARKS
	Rhizoprionodon acutus
	Mustelus mustelus
SHRIMPS
SPARIDAE
	Boops boops
	Dentex sp.
	Dentex macrophthalmus
	Diplodus sp.
	Diplodus bellottii
	Diplodus fasciatus
	Diplodus prayensis
	Lithognathus mormyrus
	Pagellus acarne
	Pagellus bellottii
	Spondyliosoma cantharus
	Viridentex acromegalus
CEPHALOPODA
LOLIGINIDAE
	Todaropsis sp.
SYNODONTIDAE
	Synodus sp.
	Synodus saurus
	Synodus synodus
TETRAODONTIDAE
	Lagocephalus laevigatus
TRACHINIDAE
	Trachinus sp.
	Trachinus draco
TRIGLIDAE
	Chelodonichthys sp.
	Chelodonichthys lastoviza
TRICHIURIDAE
	Aphanophus sp.
ZEIDAE
	Zeus faber

Annex V. Equipment and methods

The R/V DR. FRIDTJOF NANSEN is a 150 foot stern trawler with a main engine of 1500 horsepower. The vessel is equipped for acoustic surveying, bottom and midwater trawling, hydrography and plankton observations.

The bottom trawl was a 134 foot headline shrimp trawl adapted for demersal fish trawling. The foot rope was equipped with 0.5 m rubber bobbins. Bridles of 40 m gave it a horizontal distance between the wings of about 25 m. The effective vertical opening of the net was about 6 m. The pelagic trawl was of about 120 m circumference, and the vertical opening was normally 13 m. The pelagic trawl had an inner-net of mesh size 1 cm in the cod end. Pelagic trawl operations were usually monitored by aid of a 50 kHz acoustic net sonde.

Hydrographic observations were carried out with Nansen bottles with which temperature readings and samples for salinity and oxygen determinations were collected at standard depths. The salinity was determined with an inductive salinometer and dissolved oxygen by the Winkler method.

Two Simrad EK Sounders, 120 kHz and 38 kHz, connected to QM integrators, were run continuously. Settings and performance of the two acoustic systems were:

	120 kHz	38 kHz
Basic range	0 - 100 m	0 - 100 m or 0 - 250 m
Transmitter	1/1 (330 W)	Ext. (2500 W)
Transducer (ceramic)	10° (circular)	7.5° × 8°
SL + VR	116.7 dB	139 dB (13.9.81)
Bandwith and pulse length	3 kHz, 0.6 ms	3 kHz, 0.6 ms
TVG and gain	20 logR, -0 dB	20 logR, -20 dB
Recorder gain	4	7
Integrator threshold		0.5
Ingegrator gain		20 dB (×10)
Depth intervals		According to recordings

The 38 kHz system coupled to the integrator was used for abundance estimation of fish, while the 120 kHz system was used as an additional aid during the daily analysis of the echo recordings.

Sampling and processing of catch data

For each trawl catch the weight and number of each species were estimated by sampling. Species determination was mainly based on ANON (1981) and partly on BLANCHE et al. (1970). Length measurements were frequently taken, mainly on the commercially important species. The catches and their main composition are listed in Annex II and main results from the length measurements are given in Annex III.

The echo recordings and their interpretation

Assessment of the abundance of fish resources based on acoustic observations combined with experimental fishing is a method which especially lends itself to fish found in schools or other aggregations in midwater. But there are also notable exceptions, e.g. surface schooling tunas and tuna-like species and strictly bottom dwelling fish such as rays and flounders. Any fish found very close to the bottom (½-1 m) or in the very surface layer will escape echo sounder detection. For navigational reasons the work with the R/V DR. FRIDTJOF NANSEN is limited to waters deeper than 10 m. The extreme inshore waters could thus not be covered.

Because of differences in behaviour and size, different species or groups of fish species may give rise to various types of echo-recordings. Small-sized pelagic fish are, for instance, often found in well-defined schools, the recordings of which can be distinguished from those of the often looser aggregation in which semi-demersal larger fish are often found. Such classification of the echo recordings is of considerable assistance in interpreting the acoustic observations, but a positive identification by fishing operations is still indispensable and also provides the only means of sampling fish in this type of combined survey.

Based on previous experience and on identification by fishing, the echo recordings in the surveyed waters were classified as follows:

(i) Recordings of true larger schools or dense layer mostly in upper water. These will most often derive from pelagic schooling fish usually of smaller size, e.g. clupeids, scads.

(ii) All other fish recordings which especially comprised looser aggregations of smaller and larger fish near bottom. These are ascribed to demersal or semi-demersal fish such as grunts, seabreams, groupers, croakers, bigeyes etc.

(iii) Recordings of mesopelagic fish distributed in scattering layers.

Average integrator deflection per nautical mile was calculated each five nautical mile steamed. All echo traces were evaluated daily and together with the information from the trawl catches the readings from the integrator were split in categories small pelagic fish, demersal fish, mesopelagic fish and plankton. The integrator deflection was classified in two levels scattered (1-9 mm), and slightly gathered (11-20 mm), and contour lines were drawn to distinguish between areas of different density of fish. This forms the basis for the preparation of the charts of distributions of fish. For each of the areas the mean integrator value and the area of extention were calculated and their product gives an indice of abundance for that area. The conversion factor C from index of abundance to absolute abundance is linearity dependent upon the length of the fish, and we can correct for this by multiplying the index of abundance with a length-correcting factor f, where f = l/17 (l = fish length). After summing up all indices of abundance within a region the length corrected indices are converted into fish biomass by multiplying with the C value for the fish of standard length 17 cm. For the 38 kHz system with standard settings C₁₇ = 13.6 tonnes/nm²/mm/nm.

Calculation of C-value

The relationship between target strength of 1 kg of small pelagic fish with swim bladder and the length of the fish can be written:

TS_kg = -10 log 1 - 22 dB

C = a × l

A = integrator gain

C₁ = -26.5 dB
A = 30 dB

C = 0.8 × L T/n.mile²/mm/nm (L in cm)