13.1 Observations
13.2 Modern whaling off Mozambique
13.3 Discussion
During the cruises of “Dr. Fridtjof Nansen” sightings of dolphins and whales were recorded. The effective effort used for sightings was not constant during the project period. This is in part due to the fact that only during the first cruise (24 August 1977 - 4 October 1977) did a man with some past experience in whale observations participate.
Table 13.1. Observations of dolphins from “Dr. Fridtjof Nansen” off Mozambique between August 1977 and June 1978.
|
Date |
Position |
Depth (m) |
Number |
Remarks |
|
9.9.77 |
17°17’S, 38°53’N |
100 |
3 |
|
|
19.9.77 |
19°00’S, 36°20’E |
|
4 |
Probably Tursiops truncatus |
|
21.9.77 |
20°24’S, 35°02’E |
20 |
3 |
Probably T. truncatus |
|
27.9.77 |
26°11’S, 35°04’E |
130 |
20 |
At the Admiralte Leite Bank. Probably T.
truncatus |
|
20.10.77 |
19°00’S, 36°30’E |
30 |
3 1) |
Some dolphins |
|
25.11.77 |
18°33’S, 36°44’E |
100 |
4-5 |
Seen near the trawl |
|
30.11.77 |
24°51’S, 35°31’E |
200 |
3 1) |
Some dolphins |
|
1.12.77 |
25°14’S,
33°57’E |
255 |
20 |
|
|
22.1.78 |
18°41’S, 36°31’E |
30 |
8-10 |
|
|
13.2.78 |
17°59’S, 37°34’E |
30 |
5-10 |
|
|
16.2.78 |
17°52’S, 37°51’E |
30 |
100+ |
|
|
18.2.78 |
18°24’S, 37°26’E |
200 |
10-15 |
|
|
22.2.78 |
20°47’S, 35°36’E |
200 |
100+ |
|
|
3.3.78 |
20°02’S, 36°00’E |
200 |
100-200 |
|
|
21.5.78 |
23°06’S, 35°44’E |
230 |
3 1) |
Some dolphins |
|
9.6.78 |
25°30’S, 34°00’E |
200 |
6 |
|
1) “Some dolphins” recorded. The number in the brackets is the assumed value drawn in Fig. 13.1.The ship did not have a mast barrel from which a good outlook could be kept. Furthermore, a continous outlook for whales either from the roof of the steering house, the bridge, or the bow deck was not kept because of other important tasks. It is therefore considered likely that the observations made will only be a small part of what would have been recorded if the ship had been especially equipped and crewed for sightings of whales. The data base is thus not good enough for any reliable estimate of the number of humpbacks in the surveyed area. The handbook by LEATHERWOOD, CALDWELL and WINN (1976) was available for identification.
Table 13.2. Observations of whales from “Dr. Fridtjof Nansen” off Mozambique between August 1977 and June 1978.
|
Date |
Position |
Depth (m) |
Species |
Number |
Remarks |
|
25.8.77 |
24°41’S, 35°12’E |
40 |
Humpback |
2 |
Together. One was “sailing” with its
flukes. |
|
25.8.77 |
24°30’S, 35°24’E |
76 |
Humpback |
1 |
|
|
25.8.77 |
23°45’S, 35°50’E |
320 |
Unindentified |
12) |
|
|
20.9.77 |
19°50’S, 35°09’E |
16 |
Humpback |
2 |
Together. Approached the whales to 30 m. |
|
21.9.77 |
20°31’S, 35°13’E |
25 |
Humpback |
2 |
Together |
|
26.9.77 |
24°34’S, 36°34’E |
2500 |
Balaenoptera sp. |
1 |
Probably scared by the sonar |
|
30.9.77 |
25°04’S, 34°35’E |
100 |
Humpback |
2 |
Together |
|
30.9.77 |
25°03’S, 34057’E |
60 |
Humpback |
1 |
|
|
16.11.77 |
19°10’S, 37°10’E |
|
Unindentified |
5 |
|
|
21.5.78 |
13°21’S, 40°40’E |
30 |
Unindentified |
[1] 1) |
The blow was seen |
|
6.6.78 |
24°03’S, 35°34’E |
30 |
Unindentified |
[3] 1) |
Recorded as: Many and medium sized whales
2) |
|
7.6.77 |
24°21’S, 35°24’E |
30 |
Humpback |
1 |
Small |
1) Number not recorded. The figure in the brackets is the assumed number plotted in Fig. 13.1.Table 13.1 and 13.2 give the recordings of dolphins and whales. In Fig. 13.1 these observations are plotted together with the 200 and 2000 m isobath.2) Probably humpback because of the depth where the observations were made or because humpbacks are known to occur there at that time of the year.
Fig. 13.1. Observations of whales and dolphins.
The dolphins were poorly identified due to inexperience with these animals, but some of the smaller groups were probably Tursiops truncatus. The dolphins were commonly seen in the Sofala Bay area (Fig. 13.1). The numbers recorded are subject to considerable uncertainty. Several sightings of dolphins have not been recorded. The dolphins were only observed over the shelf or on the continental slope, although the deeper waters were regularly surveyed.
A total of 22 larger whales were observed on 12 occasions (Table 13.2). Of the 12 larger whales observed during the first cruise, 11 are recorded as humpbacks (Megaptera novacanglia).
One larger whale was observed outside the shelf. This whale seemed to be scared by the vessel, possibly by the sonar. It swam away at approximately the same speed as the ship (10 n.m. pr. h.). The observation distance was 1-1 1/2 n.m. at the minimum. This was a Balaenoptera sp., most likely a fin whale (B. physalus) or a sei whale (B. borealis).
Modern whaling off Mozambique was initiated in 1911 by two Norwegian companies (RISTING 1923, TØNNESSEN 1967, 1969). According to these authors a shore station was established at Inhambane, (Table 13.3, Fig. 13.1) and a factory ship was anchored at Angoche. At that time, before satisfactory evaporators had been developed, the whaling stations and the factory ships were dependent on freshwater supplies from land. Thus the whaling companies in Mozambique established themselves near the rivers. In 1912 four companies were engaged in whaling off Mozambique. One of them, The Mozambique Whaling Company, was running two land stations and one factory ship at Inhambane. From 1913 to 1915 only the Mozambique Whaling Company was operating. All the whaling companies were Norwegian.
From RISTING (1922), TØNNESSEN (1967, 1969) and ANON. (1931).
1) Mostly humpbacks. 2) According to Portuguese statistics. The number is probably too low. Mostly humpbacks. 3) The whaling did not start before September.The catches off Mozambique consisted almost exclusively of humpbacks. The experience among the whalers was that the abundance of whales decreased northwards. In May-July the humpbacks arrived from the Antarctic, migrating northwards off South Africa where whaling was being also carried out. The further north. the later they arrived on the grounds. The northernmost whales also started the southward migration earlier.
Fig. 13.2 shows the weekly production of whale oil by the Mozambique Whaling Company in 1913 (RISTING, 1923). This company had two land stations at Inhambane and used five catcher boats. The production in June of that year was only 1000 barrels while weekly production results are available from 1 July.
The whaling off Mozambique lasted for the five consecutive years 1911 to 1915. The stock. or at least that component of the stock which occurs over the shelf off Mozambique. was reduced, and the whaling in this area stopped for economic reasons (RISTING 1923, TØNNESSEN 1967, 1969).
In 1923 the whaling off Mozambique was resumed by one Norwegian company. It was not, however, profitable (TØNNESSEN 1969). Since 1924 whaling has not been conducted off Mozambique, although the same stocks of whales occurring off Mozambique have been exploited elsewhere. The humpbacks of Mozambique belong to the stock of humpbacks which in the southern summer feed in the Antarctic Area III south of Africa (MACKINTOSH 1965). Especially in the 1930’s large catches (1000-4000 animals) were taken from this humpback stock off South Africa and in the Antarctic (MACKINTOSH 1965). The International Whaling Commission banned the catching of humpbacks in the whole southern hemisphere in 1964.
Fig. 13.2. Weekly production of whale oil by the Mozambique Whaling Company in 1913.
All the humpbacks except one were observed in the shelf area, as defined by the 200 m isobath. Whales recorded as humpbacks were observed in the season from June to September. This is in agreement with the time of whaling activity. Although the surveys were not concentrated in the waters south of Inhambane, most of the humpbacks were seen in this area (Fig. 13.1). This is also the area that seemed to be the best whaling grounds in the past (Table 13.3).
