Report of a cetacean survey in the Western Approaches of the ...

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Fig. 6. Position of main fishing grounds based on survey observations (2004 and 2005); where thelarger (western) green block indicates the Scottish fishing ground; the smaller green block indicates theFrench fishing ground; the larger black box the main fishing ground identified during the 2004 survey;the largest blue box presents the survey area; and blue dots represent sighting positions of commondolphins (regardless the effort status).Interaction with fisheriesSightings within 2 nmiles of pelagic trawl fisheries were noted throughout the survey period. Nosightings were made during dedicated ‘Fisheries Observation’ survey modes (FOS or FOF). However,a total of 20 fisheries related (incidental) sightings were recorded comprising a total of 78 animals (seeTable 3), amongst these was one common dolphin calf. The species involved were common dolphins,bottlenose dolphins and harbour porpoises. In addition, basking sharks were sighted twice in vicinity ofpair trawlers.Interactions between fisheries and cetaceans were reported four times, involving common dolphin andunidentified dolphin. Interactions included bow-riding a RIB (in vicinity of the trawlers) and surfacingin vicinity of the nets and in vicinity of the fishing vessels. When cetaceans were seen approaching thefishing operations this was also regarded as a possible interaction. The interactions or possibleinteractions are briefly described below.On the 26 th of February at 18:38, a group of 4 common dolphins were seen from the RIB in the vicinityof non-operating trawlers. The dolphins did not interact with the RIB and were briefly seen surfacing invicinity of the fishing boats.On the 9 th of March at 13:35, a group of 5 common dolphins approached the RIB which was stationarybehind a pair of non-operating trawlers. The dolphins briefly interacted with the RIB. The dolphinswere seen in a tight group formation travelling towards the fishing vessels.On the 15 th of March at 08:13, a group of 15 unidentified dolphins were seen in a loose groupformation in vicinity of one of the trawlers which was setting the net (i.e. half way through the settingprocedure). The dolphins were then seen moving towards the fishing vessel. By the time the setting hadfinished, the dolphins had disappeared from the area.20
On the 23 rd of March, at 08:23, a group of 3 common dolphins were reported in the vicinity ofoperating trawlers which later hauled their nets at 09:54. The animals, which were seen in a loosegroup formation, were first seen in the vicinity of the survey vessel, briefly bow-riding. The dolphinswere then seen heading towards the pair of operating trawlers.Dead dolphinsDuring this expedition, a total of 9 dead dolphins, all identified as common dolphins, were foundfloating in the water. The information gathered about each of the dead dolphins, including photographsof characteristic markings have been reported elsewhere (WDCS, 2005). However, information on date,time, position, species, sex and length are summarized in Table 10.Six carcasses were found in an area of approximately 18-50 nmiles south of Plymouth Harbour, onecarcass was reported near Falmouth and two carcasses were found in the southern part of the Channel(one of which just 17 miles east of Brest, France). Dolphins 1-2 and 6-8 were retrieved and stored inthe ship’s freezer to facilitate full post-mortem at a later date (see Appendix ii). The post mortemsrevealed that a number of findings consistent with entanglement in fishing gear (by-catch) were found.These included the partial evisceration of the carcass, cutaneous netmarks, haemorrhage and evidence ofrecently ingested prey. Several of the net marks found on the carcasses of Dolphins 2, 6 and 7 wereconsistent with those made by gillnet-type fishing gear however this was not found for Dolphin 1 and 8.The post mortems provided no other evidence for cause of death for any of the dolphins other thanentanglement in fishing gear.The relatively high body temperatures of dolphins 2 and 5-7 (well above ambient sea water temperature)show that these animals died a short time before they were found.Dolphin Date Time(GMT)Position(Lat/Long)Species Sex Length(cm)1 22.02.2005 09:13 50°00.379N D. delphis ♂ 219004°15.150W2 08.03.2005 08:33 49°31.954N D. delphis ♀ 198004°20.075W3 11.03.2005 11:31 48°45.551N D. delphis ? n/a005°52.908W4 11.03.2005 15:52 48°16.481N D. delphis ? n/a004°55.918W5 15.03.2005 08:40 49°36.888N004°16.546WD. delphis ♂ 183immature6 15.03.2005 09:11 49°37.048N D. delphis ♀ 197004°15.869W7 15.03.2005 09:19 49°36.965N004°15.295WD. delphis ♂ 185immature8 17.03.2005 14:05 49°36.404N D. delphis ♂ 221004°46.291W9 26.03.2005 10:15 50°08.233N005°01.062WD. delphis ♀ 183immatureTable 10. Details on date, time, position, species, sex and length of dead dolphins found floatingduring the expedition.21
Page 1 and 2: Report of a cetacean survey in theW
Page 3 and 4: EXECUTIVE SUMMARYThe Western Approa
Page 5 and 6: INTRODUCTIONLittle is known about t
Page 7 and 8: Two important assumptions of line t
Page 9 and 10: also to report the presence of dolp
Page 11 and 12: RESULTSPart 1. Cetacean distributio
Page 13 and 14: SpeciesFAST MODENumber of sightings
Page 15 and 16: Initial sighting cuesDuring fast su
Page 17 and 18: Harbour porpoiseThe harbour porpois
Page 19: Part 2. Fisheries observationsFishi
Page 23 and 24: Fig 7. Frequency distribution of si
Page 25 and 26: The estimates of abundance generate
Page 27 and 28: Proportion of sightings by perpendi
Page 29 and 30: Proportion of sightings by componen
Page 31 and 32: Fig. 18. Histograms of perpendicula
Page 33 and 34: DISCUSSIONThe estimated corrected d
Page 35 and 36: extrapolated total estimated mortal
Page 37 and 38: Tregenza, N.J.C. and Collet, A. 199
Page 39 and 40: Dolphin 2SPECIES: Common dolphin (D
Page 41 and 42: CETACEAN POSTMORTEM REPORTDolphin 7

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