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Table 1. Myctophid species identified from cruise 1 to 6 of R/V “Dr. Fridtjof Nansen”. xx dominant on one or more cruises, x present.

Table 2. Diaphus species identified from cruise 1 to 6 of R/V “Dr. Fridtjof Nansen”.

Species	South of 10° N	North of 10° S
D. ashmeadi Fowler (?)		+
D. coeruleus Klunzinger	+	+
D. diademophilus Nafpaktitis		+
D. garmani Gilbert	+
D. lobatus Nafpaktitis		+
D. luetkeni Brauer		+
D. parri Tåning		+
D. regani Tåning		+
D. thiollierei Fowler	+	+

Table 3. Values of F and corresponding significance of analysis of variance tests of the regression of echo abundance on the distance from the shore.

+ indicate increase and - decrease in echo abundance with increasing distance.

ns not significant
* p < 0,05
** p < 0,01
*** p < 0,001

Cruise				Area
No	A	B	C	D	E	F	G	H	I
1,2	- [32]	- [31]	- [35]	- [37]	B. pterotum 30	B. fibulatum 80	S. evermanni 75	B. fibulatum 80	M. brachygnatum B. fibulatum 60
3	B. pterotum 40	B. pterotum 35	B. pterotum 35	B. fibulatum 50	S. evermanni 50	- [55]	B. fibulatum 60	- [55]	B. fibulatum 47
4	B. pterotum 32	B. pterotum 31	B. pterotum B. fibulatum 35	B. fibulatum B. pterotum 37	B. pterotum 38	B. fibulatum B. pterotum 35	B. fibulatum 37	- [38]	Diaphus spp. B. fibulatum 38
5	B. pterotum 35	B. pterotum 35	[35]	Diaphus spp. 42	B. pterotum 33	60	75	Diaphus spp. 62	Diaphus spp. 45
6	B. pterotum 32	B. pterotum 34	B. pterotum 34	Diaphus spp. 40	M. spinosum B. pterotum 31	Diaphus spp. 40	B. fibulatum 80	- [38]	M. brachygnatum 40

Table 5. Estimated abundance of mesopelagic fish in the areas investigated (in million tons).

	Area
Cruise no.	Period	A	B	C	D	E	F	G	H	I	Total area
1.2	spring 76	20	8	23	15	12	28	26	10	6	148
3	aut. 76	8	6	19	17	12	16	20	6	3	107
4	spring 77	13	7	23	15	5	11	31	5	3	113
5	summer 77	11	7	17	6	2	4	6	1	2	56
6	aut. 77	15	5	20	11	3	4	20	5	3	86
Mean		13	7	20	13	7	13	21	5	3	102

Table 6. Trawl stations with catch rates of myctophids > 400 kg/hour. P = pelagic trawl (1360 meshes), KT= krill trawl, BT= bottom trawl.

Fig. 1. The investigated area. A - I: the subareas and 1-5: the sections referred to in the text.

Fig. 2. The vertical migration observed during the diurual station in the Gulf of Oman. March 1976. 1. schools and very dence agregations. 2. dence recordings, 3. scattered recordings, a - k: refer to the echograms in Fig. 3.

Fig. 3. Echo recordings obtained during the diurnal station in the Gulf of Oman. a - k: refer to Fig. 2.

Fig. 4. Five miles averages of integrator deflection in mm per nautical mile from the diurual station in the Gulf of Oman.

Fig. 5. Vertical distribution of temperature, salinity and oxygen at the diurual station in the Gulf of Oman.

Fig. 6. Depth of DSL and vertical distribution of temperature, salinity and oxygen from two stations off Pakistan.

Fig. 7 Five miles averages of integrator deflection in mm per nautical mile along five sections.

A. section 1, off the coast of Pakistan.
B. section 2, Gulf of Oman.
C. section 3, off the Kuria Muria Islands,
D. section 4, Gulf of Aden and E. section 5, off eastern Somalia.
2 - 6: cruise number.

Fig. 7 B.

Fig. 7 C.

Fig. 7 D.

Fig. 7 E

Fig. 8. Mean integrator deflection per nautical mile in mm in the 9 subareas (A - I). 1 - 6: cruise number

Fig. 9. Map showing trawl stations giving more than 400 kg per hour trawling of mesopelagic fish.

Fig. 10. Length distribution of Benthosema pterotum caught off Pakistan.

Fig. 11. Length distribution of the light coloured Benthosema pterotum caught in the Swatch.

Fig. 12. Length distribution of Benthosema pterotum caught in the Gulf of Oman.

Fig. 13. Length distribution of Benthosema pterotum caught in the Gulf of Aden.

Fig. 14. Relation between length and number of primary zones in the otoliths of Benthosema pterotum.

Fig. 15. Diurual variation in degree of filling (A) and stage of digestion (B) of stomach contents of Benthosema pterotum caught at the diurual in the Gulf of Oman.

N: noon; 1,2,3,4: night stations; M: morning.

Fig. 16. Length distribution of Benthosema fibulatum caught off Somalia.

Fig. 17. Length distribution of Benthosema fibulatum caught in the northern Arabian Sea.

Fig. 18. Relation between length and number of primary zones in the otoliths of Benthosema fibulatum.