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

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Fig. 2. Survey set up for the secondary platform.Survey effortEffort during the survey was divided into several types (see Table 1). Survey effort continuedthroughout all daylight hours but was suspended when the Beaufort sea state exceeded 4.5 or visibilitywas considered poor (< 1 nmile). Sightings made during bad weather or when no systematicobservations were being conducted (i.e. low and off effort) were regarded as incidental sightings. Whenobservers failed to report a sighting which was seen by others (not on watch) this was also regarded asincidental.Effort mode Abbreviation Speed Mode DescriptionTransectTFast Systematic surveys following pre-determinedTS SlowtransectsHigh Effort SFast Systematic surveys not following pre-determinedSLOW Slowtransects whilst on transitFisheries FOF Fast Data collected during non-systematic surveys thatObservations FOS Slow were specifically aimed at monitoring fisherieswithin 2 nmilesLow effort L n/a Dedicated observations made during bad weather(sea state>4.5) or when visibility was poorOff effort X n/a No dedicated observers on watchTable 1. Information and abbreviations for different survey modes conducted at either fast (~8.5 knots)or slow (~ 5.3 knots) speed of the survey vessel.Interactions with fisheriesDuring those parts of the survey focussed on monitoring fisheries, we recorded the position of the pairtrawlers hourly. We also recorded information from each cetacean sighting relating to the presence ofpelagic trawlers in the general area (within 2 nmiles), noting down bearing and distance to the vesselswith help of the ship’s radars (Furuno and Nucleus2 5000ATA). Only when the MV Esperanza waswithin good visual range of the fishing operations and with cetaceans in the area, would we repeatedlyplot sightings of dolphins and trawlers and monitored any apparent interactions between cetaceans andthe fishing operations. Data relating to the fishing vessels themselves are not presented here.In addition, a RIB (Rigid-hulled inflatable boat) was often on stand-by within several hundreds metresof the fishing vessels, before, during and after the hauling of the nets, in order to monitor by-catch and8
also to report the presence of dolphins in vicinity of the fishing operations. No dedicated watches wereconducted from the RIB. Sightings made from the RIB or the main survey vessel during suchoperations were regarded as incidental.Dead dolphinsOn several occasions floating dead dolphins were sighted and, when possible, these were retrieved bythe Greenpeace crew for detailed external morphological examinations and to make them available forlater full pathology. When a dead dolphin was sighted, the following data were collected: time, date,position, sea state, swell height, cloud, visibility, wind force, wind direction, sea surface temperature,bearing and distance to the dead dolphin. To help to retrieve the dolphin, a marker buoy wasimmediately placed in the vicinity of the animal and a RIB was launched as swiftly as possible. Usually,the dead dolphins were brought on board 1 .For each dead dolphin that was retrieved, the following features were carefully photographed: wholeanimal, dorsal fin (left and right side), both flippers, head side view, top of the head/blowhole, eyes,close-up of the beak, fluke, flanks, genital regions and any obvious scarring. In addition, those deaddolphins that were recovered and brought onboard were identified to species, their sex determined andan assessment of the maturity status was made based on length and size. In addition to this, basic bodymeasurements, body temperature measurements and detailed morphological external examinations (seeWDCS, 2004) were carried out. When body temperatures were taken a digital thermometer wasinserted via the anus using a 50cm probe (MM2050/TM-electronics) and readings were taken atdifferent depths. The dead animals were supported by custom-built ‘hammocks’ and stored in acontainer at a temperature of -5°C for three days after which the temperature was brought down andmaintained at -10°C.Photo-identificationPhotographs of live small cetaceans were taken for natural markings studies. Equipment used were (i) aCanon D20 with a Canon 70-200mm f2.8 lens or a Canon 24-70mm f2.8 lens; (ii) a Minolta Dynax D7with a Sigma 70-200mm f2.8 lens; and (iii) a Canon 300D with a Canon 35-350 f4-5.6 lens.Underwater video and photographyUnderwater footage of common dolphins wake-riding the survey vessel were collected during calmweather conditions. A custom-built underwater housing (made by G. Newman) was positioned on aflexible pole allowing live images to be seen on a screen. A Toshiba TU-48p with a Tahoma 2mm lenswas used. Footage was recorded on a Sony DVCAM recorder. In addition, a Kodak ProSLR-N (14million pixels) with a Nikon 16mm fish-eye lens was also occasionally used to allow underwater stillsphotography (used in the underwater housing).Analytical methodsThe analyses are concentrated mainly on sightings made during ‘Transect’ and ‘High Effort’ surveymodes (part 1). Re-sightings and duplicate sightings were eliminated from the main data set. Duplicatesightings (part 3) were identified on the basis of time and sub-sequent re-sightings, species ID, bestgroup size and heading of the animal(s). Radial distances and angle data were converted toperpendicular distance (see Buckland et al., 1993).The distribution of sightings and the relative abundance, (N/L) measured as the number of sightings per100km travelled (where N is the number of sightings), are presented in part 1 of this report. In addition,average distance to shore, water depth, sea surface temperature (SST) and sea state associated withsightings data were calculated and presented for different species. For comparison, we also give anoverview of data obtained during slow speed mode, although the sample sizes are much smaller thanfor fast speeds. Sightings made in vicinity of fisheries should be regarded as a separate set of data as1 Animals were lifted onto deck using a belt around the tailstock and the ship’s crane, with theexception of one occasion when the animal was lifted with a belt around the body using the ship’scrane (due to high seas it was not possible to launch a RIB for the retrieval and the survey vessel wascarefully maneuvered alongside upon which the dolphin was retrieved).9
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: Two important assumptions of line t
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 and 20: Part 2. Fisheries observationsFishi
Page 21 and 22: On the 23 rd of March, at 08:23, a
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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