Wildlife observations during RV Meteor cruise M65-2:
Dakar, Senegal to Las Palmas, Canary Islands
July 4 - 26 2005
Dr Russell B Wynn
National Oceanography Centre, Southamtpon
Download this report (MS Word file, 76kB)
Click here for list of species seen on this cruise
July 4: Passage from Dakar Harbour, Senegal to 14º28’N/17º57’W (60 km WSW of Dakar, Senegal)
The cruise started in Dakar with Yellow-billed Kites flying around the ship and scavenging fish in the harbour. Once the cruise was underway, the initial passage across the shelf into deep water was disappointingly quiet. At least 20 Royal Terns and four Black Terns were noted, and also about 15 storm-petrel sp. that were too distant to identify (suspected to be Madeiran Storm-petrels). The highlight was a group of four Bottle-nosed Dolphins seen close inshore. During the evening, while arriving on station over the margin of Dakar Canyon, a larger group of oceanic dolphins comprising 10’s of animals was seen distantly, and 100-500 flying fish were noted. Surprise of the day was an Alpine Swift seen moving south, while seabirds offshore included a Wilson’s Storm-petrel and two Black Terns.
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July 5: Passage from 14º03’N/17º52’W (90 km SW of Dakar, Senegal) to 13º18’N/17º51’W (110 km W of southern Senegal)
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The day was spent undertaking southward passage along the upper slope. Two large groups of distant unidentified dolphins were seen, comprising 100’s of animals, and also a distant pod containing 10’s of Short-finned Pilot Whales. Seabirds included 35 Black Terns, mostly in two groups of 10 and 16 seen feeding over tuna shoals. All birds were in first-summer plumage except for a single second-summer/adult. In addition, a single Brown Booby attempted to land on the ship. Good numbers of flying fish and tuna were seen throughout the day, and also a single large dorado. The calm weather meant it was possible to see patches of plankton ‘soup’ in the surface waters. |
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July 6: On station at 12o35’N/18o30’W (180 km off southern Senegal)
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A tropical storm with torrential rain and strong winds heralded the start of the rainy season, and prevented any observations for much of the day. In the late afternoon single Little and Plain Swifts were seen flying around the ship, and appeared to roost on board. The Little Swift was relocated in the night clinging to a window wiper on the bridge deck! Equally surprising was a Royal Tern that appeared exhausted as it flew alongside the ship and then flopped onto the water. It quickly became waterlogged but was rescued by a crewman with a long landing net! It was boxed, force-fed some defrosted squid, and left to dry out overnight. Presumably, it had become weakened and disoriented by the storm. The swifts may also have been pushed offshore by the rain, or alternatively could have been early migrants returning south from the Cape Verde Islands. Finally, a Common Tern was seen flying around the ship in the afternoon. |
July 7: Passage from 12º40’N/18º30’W (180 km off southern Senegal) to 13º12’N/18º13’W (160 km off southern Senegal)
The Royal Tern was still alive and well in the morning, and after its release flew strongly around the ship before settling on the mast structure for several hours. It had apparently departed by late afternoon. At least six Plain Swifts were around the ship during the morning, including one stranded on the working deck that was successfully re-launched into the air from the bridge deck. A White-rumped Swift flying over mid-morning was the fourth swift species recorded since leaving Dakar! Seabirds included a single Common Tern and eight Black Terns. In the evening a distant group of dolphins was seen (note that all of the dolphins seen offshore so far have been at long range, preventing firm identification).
July 8: Passage from 13o45’N/18o16’W (150 km SW of Dakar, Senegal) to 13o56’N/18o13’W (130 km SW of Dakar, Senegal)
The only seabird noted was a first-summer Common Tern that spent several hours hunting small fish around the front of the ship.
July 9: Passage from 14º38’N/17º47’W (30 km SW of Dakar, Senegal) to station at 14º11’N/17º53’W (80 km SSW of Dakar, Senegal)
The day began over the upper part of Dakar Canyon, in sight of the Dakar Peninsula. However, there were still very few seabirds to be seen, with just 13 Black Terns noted. The surprise of the day was an Oleander Hawk-moth found on deck in the afternoon.
Oleander Hawk-moth
July 10: On station at 14o11’N/18o06’W (100 km SW of Dakar, Senegal)
During the morning sample survey not a single seabird, fish or otherwise was recorded. The only wildlife observations relate to an influx of migrant moths, with about 25 individuals of at least 10 species recorded.
July 11: Passage from 13o18’N/19o01’W (220 km SW of Dakar, Senegal) to 13o14’N/18o58’W (200 km SW of Dakar, Senegal)
Two storm-petrel sp. were seen during the morning, together with a distant group of 10-100 dolphin sp. Another five or so migrant moths were found on deck.
July 14: Passage from 14o25’N/19o05’W (170 km W of Dakar, Senegal) to 16o04’N/19o02’W (220 km NW of Dakar, Senegal)
A day of passage took the ship north of Dakar for the first time, and there was a marked change in the variety of seabirds recorded. Two Cape Verde Shearwaters, three Bulwer’s Petrels, three Fea’s Petrels, three Madeiran Storm-petrels and eight storm-petrel sp. were seen, as well as about 70 Short-finned Pilot Whales and three turtle sp. Good numbers of flying fish were seen again, but tuna were totally absent in this area.
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Bulwer's Petrel |
Maderian Storm Petrel |
July 15: Passage from 18o42’N/18o02’W (180 km SW of Cap Timiris, Mauritania) to 19o35’N/16o56’W (50 km W of Cap Timiris, Mauritania)
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During the day the Western Palearctic zoogeographical recording area was entered for the first time as the ship progressed north. The day began with a typical scatter of open ocean seabirds, including seven Leach’s, seven Wilson’s and five Madeiran Storm-petrels, seven Bulwer’s Petrels, three Cape Verde Shearwaters and 18 Black Terns. A single Arctic Skua in 2nd summer plumage was the only indication of the approaching shelf edge. Cetaceans included 20-30 Short-finned Pilot Whales, a group of 10-50 spinner dolphins, and a further three groups of dolphin sp. totalling 100’s of animals. Also of note were a turtle sp. and two Hammerhead Sharks. Flying fish were still abundant but only three fishing boats were seen, none of which was accompanied by seabirds. | |
| Around midday the winds began blowing steadily offshore, providing a reminder that we were now in the active Trade Wind belt and the start of the upwelling zone. The shelf break was reached at about 1700 hrs, and SST dropped from 26.5oC to 24.9oC within an hour (a decrease of 1.5oC). An indication of the changing water temperature was shown by the marked reduction in flying fish recorded, and also the arrival of a flotilla of at least a dozen fishing boats scattered across the sea (exploiting the fish stocks associated with the upwelling). A comparison of midnight SST indicated that the upwelled waters were about 3oC cooler than the surrounding water. The change in seabird density was staggering; up to mid-afternoon no more than 20 birds per hour were recorded, but after the upwelling zone was reached this instantly rose to 1000+ per hour. The dominant species was Wilson’s Storm-petrel, particularly around the front itself at the shelf edge. Over 1000 were estimated in the first hour of passage though the upwelling zone, including a group of over 200 sitting on the sea. |
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The largest numbers of Black Terns, literally 100’s of birds, were not counted until the outer shelf was reached, and the vast majority of these were congregated around, or flying between, trawlers in the act of recovering their catches. Roughly 90% were in 1st summer plumage. Other species seen included 10’s of Cape Verde Shearwaters, Royal and Common Terns, and also single 1st summer Sandwich and Roseate Tern. Surprisingly, the only skua noted was an immature Arctic Skua, seen harassing terns around one of the fishing boats. In general, the vast majority of seabirds on the outer shelf were associating with active fishing boats, and even those birds seen away from the boats themselves were on the move rather than feeding (most of the birds seen passing the RV Meteor did so to the rear of the ship). Only the Wilson’s Storm-petrels seemed to be unaffected by human fishing activities. Despite careful scanning, no other species of storm-petrels were observed.
Short-finned Pilot Whale
July 16: Passage from 20º01’N/17º31’W (125 km NW of Cap Timiris, Mauritania) to 20º05’N/17º32’W (125 km NW of Cap Timiris, Mauritania)
A calm start to the day provided good conditions for observations. A transect on the outer shelf began with 100’s of Wilson’s Storm-petrels and Black Terns, but really came alive at 0820 hrs when the shelf edge was reached. Several huge flocks of resting and feeding Wilson’s Storm-petrels were roughly lined up just upslope from the shelf edge, with a conservative estimate of some 2000 birds present in this small area. The true figure was probably much higher as just one of the flocks was counted in a photograph, and actually contained at least 600 birds! Most birds were sitting on the sea but those closest to the survey line took to the air en masse as the ship approached to within 100 m. A small number of Cape Verde Shearwaters were associated with the flocks at the shelf edge, and a sub-adult Gannet was seen sitting on the sea. At least three immature Arctic Skuas were also noted around the shelf edge, including one being harassed by a Long-tailed Skua. It seems likely that this dense concentration of birds was a result of the calm conditions, with nutrient-rich upwelled waters remaining concentrated at the shelf edge, rather than being mixed and dispersed across the outer shelf and upper slope.
Wilson's Storm Petrels
As the ship headed back onto the flat outer shelf, numbers of Wilson’s Storm-petrels and Black Terns decreased markedly, although hundreds of birds were still scattered over the area. Very few of the Black Terns were actively feeding, but instead appeared to be commuting between active trawlers. A quick age survey earlier in the day found that about 80-85% were birds in their 1st summer plumage, with the remainder being 2nd summer or adult birds.
Other seabirds seen during the day included small numbers of Common and Sandwich Terns, and also a single Bridled/Sooty Tern. A juvenile Swallow rested on the ship for a few minutes in the afternoon, and a butterfly sp. was also seen.
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Long-Tailed and Arctic Skuas |
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July 17: Passage from 19º53’N/17º26’W (110 km WNW of Cap Timiris, Mauritania) to 19º39’N/17º24’W (100 km WNW of Cap Timiris, Mauritania)
| An initial passage from deep water onto the shelf provided a good opportunity to quantify the changing concentration of seabirds across this transect. At water depths >1000 m, numbers of Black Terns and Wilson’s Storm-petrels were seen at a rate of 10’s per hour, with only a couple of (probably non-active) fishing boats seen and small numbers of flying fish. Most of the Black Terns were seen in a loose flock of up to 45 birds that circled repeatedly around the ship. As the uppermost slope and outer shelf was reached, numbers of Black Terns and Wilson’s Storm-petrels increased to 100’s per hour, and small numbers of Cape Verde Shearwater, Common Terns and Royal Terns appeared at the shelf edge. An immature Long-tailed Skua was seen harassing a dark immature Arctic Skua. The number of trawlers increased to five and flying fish disappeared. The highest density of birds was present on the outer shelf in association with up to 16 trawlers, with 1000’s of Black Terns concentrated in huge flocks around active boats and 100’s of Wilson’s Storm-petrels scattered loosely across the whole area. At times a steady stream of Black Terns could be watched passing across the back of our ship as they moved between trawlers. The largest single flock, containing 1000’s of birds, was associated with a pair of trawlers working in tandem. There was some evidence of feeding independent of human fishing activity, for example about 700 Black Terns were watched actively feeding in a linear flock on the outer shelf at 1230 hrs, even though five trawlers were in the vicinity. This flock was almost totally made up of the one species, and no skuas were in attendance (skuas were notable for their absence for most of the day). |
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Three-figure counts of Royal Terns and Cory's/Cape Verde Shearwaters were made in certain areas, and these species were strongly associated with trawlers, e.g. 270 Royal Terns flying around (and perched on) two trawlers at 1448 hrs, and 130 Cory's/Cape Verde Shearwaters following trawlers at the shelf edge between 1740 and 1755 hrs. The latter two species was usually seen in loose flocks of up to 80 birds, and at times would follow our ship for long periods. Other species recorded included 10’s of Common and Sandwich Terns and a total of six Bridled/Sooty Terns (including one attempting to steal food from a Black Tern), although only one distant skua sp. was seen. A Leach’s Storm-petrel was found in the after deck laboratory in the early afternoon and was released successfully; it had presumably come on board during the previous night when the lights were on and the ship was working in deeper waters offshore.
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In the later afternoon we left the upwelling zone and headed back west to deeper water. During the three days spent in the upwelling zone, estimated totals for the commonest species included 10,000 Wilson’s Storm-petrels, 10,000 Black Terns, 700 Royal Terns, 350 Cory’s/Cape Verde Shearwaters and 100 Common Terns. The numbers of Wilson’s Storm-petrels are apparently unprecedented within the Western Palearctic, although it seems likely that the Mauritania upwelling zone is a regular non-breeding site for the species and that they have just been previously overlooked in this rarely surveyed region. |
July 20: On station at 20o30’N/20o40’W (380 km W of Cap Blanc, Mauritania)
| After a couple of days of strong winds and rough seas, the weather became calmer and some observations were made. The only seabirds noted were two distant petrel sp., but migrant landbirds included two Swallows and up to eight Common Swifts, several of which appeared to roost on the ship overnight. These birds had probably been displaced by the same weather system that had pushed large amounts of Sahara dust westwards out to sea. The highlight of the day was a group of two or three Minke Whales feeding around the ship in the evening for at least two hours. |
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July 21: Passage from 20o39’N/20o55’W (380 km W of Cap Blanc, Mauritania) to 20o32’N/20o32’W (370 km W of Cap Blanc Mauritania)
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Another three Common Swifts were seen around the ship during the morning, and an exhausted bird was picked up in the early afternoon. Unfortunately it was too weak to fly, and despite attempts to give it water, it soon became moribund and died the following day. The only seabirds noted were a single Bulwer’s Petrel and up to 11 Leach’s/Madeiran Storm-petrels. Other wildlife included small numbers of flying fish, at least two shark sp., and a distant small rorqual sp. |
July 22: Passage from 21o15’N/20o40’W (380 km WNW of Cap Blanc, Mauritania) to 21o13’N/20o32’W (375 km WNW of Cap Blanc, Mauritania)
An hour of survey in the evening produced two Leach’s/Madeiran Storm-petrels and 10-100 flying fish
July 23: Passage from 20o53’N/18o40’W (160 km W of Cap Blanc, Mauritania) to 21o05’N/18o39’W (160 km WNW of Cap Blanc, Mauritania)
An hour of survey in the late afternoon in rough weather produced just three storm-petrel sp. and a few Flying Fish.
July 24: Passage from 24o06’N/18o12’W (220 km offshore Western Sahara) to 24o45’N/17o39’W (200 km offshore Western Sahara)
The only seabirds seen during the day were a Bulwer’s Petrel, three Cory’s Shearwaters and one Leach’s/Madeiran Storm-petrel. A group of cetaceans seen in the early evening contained 10-20 Short-finned Pilot Whales and 5+ dolphin sp. Good numbers of flying fish were still present.
July 25: Passage from 26o34’N/17o04’W (150 km SE of Hierro, Canary Islands) to 26o40’N/17o07’W (140 km SE of El Hierro)
Slightly more seabirds were recorded as the ship steamed north towards the Canary Islands. A total of 32 Cory’s Shearwaters and four Bulwer’s Petrels were seen during the afternoon, together with small numbers of flying fish. Most of the Cory’s Shearwaters were seen as single birds, unlike in the Mauritania upwelling zone where most were gathered in loose flocks. Other birds noted included a single Feral/Racing Pigeon and two Plain Swifts.
List of confirmed bird and cetacean species seen on this cruise
| Cory’s Shearwater | Calonectris diomedea |
| Fea’s Petrel | Pterodroma fea |
| Bulwer’s Petrel | Bulweria bulwerii |
| Wilson’s Storm-petrel | Oceanites oceanicus |
| Leach’s Storm-petrel | Oceanodroma leucorhoa |
| Madeiran Storm-petrel | Oceanodroma castro |
| Northern Gannet | Morus bassanus |
| Brown Booby | Sula leucogaster |
| Arctic Skua | Stercorarius parasiticus |
| Long-tailed Skua | Stercorarius longicaudus |
| Sandwich Tern | Sterna sandvicensis |
| Common Tern | Sterna hirundo |
| Roseate Tern | Sterna dougalii |
| Royal Tern | Sterna maxima |
| Bridled Tern | Sterna anaethetus |
| Black Tern | Chlidonias niger |
| Feral/Racing Pigeon | Columba livia |
| Common Swift | Apus apus |
| Alpine Swift | Apus melba |
| Plain Swift | Apus unicolor |
| White-rumped Swift | Apus caffer |
| Little Swift | Apus affinis |
| Barn Swallow | Hirundo rustica |
| Bottle-nosed Dolphin | Tursiops truncatus |
| Short-finned Pilot Whale | Globicephala macrorhynchus |
| Minke Whale | Balaenoptera acutorostrata |
