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Stima di abbondanza di Tursiops truncatus tra La Spezia, Viareggio e Marina di Pisa attraverso cattura e ricattura fotografica

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Silvio Nuti
Silvio Nuti
Silvio Nuti
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Guido Gnone at Acquario di Genova, Fondazione Acquario di Genova
Guido Gnone
  • Acquario di Genova, Fondazione Acquario di Genova
Michela Bellingeri at Fondazione Acquario di Genova, Italy
Michela Bellingeri
  • Fondazione Acquario di Genova, Italy
Davide Bedocchi at University of Siena
Davide Bedocchi
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Stima di abbondanza di Tursiops truncatus tra La Spezia, Viareggio
e Marina di Pisa attraverso cattura e ricattura fotografica
Silvio Nuti
1*
, Guido Gnone
2
, Michela Bellingeri
3
, Davide Bedocchi
1
, Roberto Pannoncini
4
, Eleonora Manfredini
5
1
Centro CETUS,
2
Acquario di Genova,
3
Università di Genova,
4
Università di Roma “La Sapienza”,
5
Università di Parma
INTRODUZIONE
La stima di abbondanza è fondamentale per valutare lo stato di una popolazione e la sua evoluzione nel
tempo. Il presente lavoro prende in esame la tecnica di cattura e ricattura fotografica per stimare
l’abbondanza di una popolazione di tursiopi (Tursiops truncatus) nell’area compresa tra La Spezia, Viareggio
e Marina di Pisa, applicata da 2 gruppi di ricerca che operano in aree contigue: l’Acquario di Genova
(progetto Delfini Metropolitani) e il Centro CETUS.
MATERIALI E METODI
La stima di abbondanza è stata calcolata considerando ciascun avvistamento come un evento di cattura e
applicando 2 diverse tecniche statistiche per popolazioni chiuse (Schnabel, 1938; Schumacher ed
Eschmeyer, 1943). Sono state prima prodotte due stime separate (considerando due popolazioni distinte) e
poi una stima complessiva (considerando una popolazione unica). Tutti i dati analizzati sono stati raccolti nel
corso del 2005.
RISULTATI
DISCUSSIONE
Le stime dinamiche prodotte da ciascuna serie di dati risultano variabili tra una “cattura” e la successiva,
segno che il numero di animali “marcati” è insufficiente. L’aggregazione dei dati produce al contrario una
stima dinamica coerente, con intervalli di confidenza accettabili (vedi ultimi avvistamenti). La stima finale per i
2 metodi (vedi riquadro arancione) è stata ottenuta sommando la percentuale di individui non identificabili
all’ultimo valore ottenuto nella stima dinamica per dati aggregati. Da notare che la stima complessiva risulta
molto inferiore alla somma delle stime separate.
BIBLIOGRAFIA
Schnabel, Z. E. 1938. The estimation of the total fish population of a lake. Amer. Math. Mon., 45(6): 348-352.
Schumacher, F. X. & Eschmeyer, R. W. 1943. The stimation of fish population in lakes and ponds. J. Tennessee Acad. Sc., 18: 228-249.
AVV DATA TOT FOT-ID RICATT. Schumacher-
Eschmeyer Schnabel
1 15/2/05 5 4 0
2 25/2/05 6 6 1
3 16/3/05 4 2 0 65 42
4 22/3/05 20 12 1 114 87
5 16/6/05 7 4 3 45 52 28 424
6 21/6/05 6 6 1 66 67 37 334
7 23/6/05 4 1 1 58 61 35 236
8 29/6/05 12 6 1 77 75 44 243
9 25/8/05 4 2 0 91 83 49 270
10 14/9/05 20 16 1 175 136 82 392
11 15/12/05 20 11 2 209 161 101 394
108 70
C.I. (Schnabel)
75% fotoidentificabili
AVV DATA TOT FOTO-ID RICATT. Schumacher-
Eschmeyer Schnabel
1 28/4/05 10 4 0
2 12/5/05 6 5 1 40 40
3 25/5/05 15 4 3 18 19 10 950
4 26/5/05 8 3 1 22 18 10 91
5 28/5/05 11 6 3 25 21 13 62
6 25/6/05 22 8 3 32 24 15 49
7 29/7/05 12 9 3 41 27 18 49
8 6/8/05 8 2 0 46 29 20 53
9 18/8/05 5 1 0 49 30 21 55
10 1/ 9/05 3 1 1 46 32 22 58
11 4/ 9/05 13 2 1 47 33 23 58
12 23/12/05 14 7 2 61 44 31 79
127 52
C.I. (Schnabel)
41% fotoidentificabili
AVV DATA TOT FOTO-ID RICATT. Schumacher-
Eschmeyer Schnabel
1 15/2/05 5 4 0
2 25/2/05 6 6 1
3 16/3/05 4 2 0 65 42
4 22/3/05 20 12 1 114 87
5 28/4/05 10 4 0 243 131
6 12/5/05 6 5 2 105 98 49 4900
7 25/5/05 15 4 3 57 73 42 280
8 26/5/05 8 3 2 55 66 40 192
9 28/5/05 11 6 3 57 65 42 150
10 16/6/05 7 4 3 67 61 41 124
11 21/6/05 6 6 2 64 66 45 127
12 23/6/05 4 1 1 62 65 44 121
13 25/6/05 22 8 4 66 67 47 116
14 29/6/05 12 6 1 78 76 54 128
15 29/7/05 12 9 4 84 80 58 129
16 6/8/05 8 2 0 90 84 61 135
17 18/8/05 5 1 0 94 86 63 139
18 25/8/05 4 2 0 101 91 66 145
19 1/9/05 3 1 1 98 89 65 142
20 4/9/05 13 2 1 99 90 66 142
21 14/9/05 20 16 2 138 115 85 177
22 15/12/05 20 11 7 131 115 87 168
23 23/12/05 14 7 4 131 117 90 167
235 122 52% fotoidentificabili
C.I. (Schnabel)
Stima abbond anza (La Spezia)
0
50
100
150
200
250
1234567891011
Catture (avvistame nti)
N
Schnabel
Schumacher-
Eschmeyer
Stima abbondan za (Viareg gio - Marina di Pisa)
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12
Catture (avvistame nti)
N
Schnabel
Schumacher-
Eschmeyer
Stima abbon danza (La Spezia - M arina di Pisa)
0
50
100
150
200
250
300
1 2 3 4 5 6 7 8 9 10 11 12 1314 15 16 17 18 19 20 2122 23
Catture (avvistame nti)
N
Schnabel
Schumacher-
Eschmeyer
34CETUS
1359
Acquario di
Genova
CETUS
Acquario di
Genova
TOT: 93
N
Schumacher-Eschmeyer
= 252
N
schnabel
= 225
Fig. 1 – Punti di avvistamento e animali foto-ID e condivisi (griglia).
... In the Cinque Terre Natural Marine Protected Area the continental shelf is very extensive: the 100 m isobath runs at an average distance of 12 km from the coast. The entire area is usually frequented by the bottlenose dolphins [5,7]. Data collection included field work, implemented through data acquisition days conducted in the May-November 2018 period, and data analysis was performed on computer. ...
X-Band Radar for Cetacean Detection (Focus on Tursiops truncatus) and Preliminary Analysis of Their Behavior
Article
Full-text available
  • Jan 2020
Cetaceans are protected species all over the world, most of them are vulnerable, endangered, or data deficient (according to International Union for Conservation of Nature - IUCN red list). X-band radars detect the echo of the electromagnetic signal reflected by an obstacle or a ship (target). The application of X-band radar to the detection of cetaceans is a new and innovative field of research that could improve the automation of marine mammal data collection, and this is the first time in the Mediterranean Sea. The aim of this work was to test the capability of X-band radar installed along the coast (ground-based) to detect and track cetaceans in a range of approximately 2.5 nautical miles from the radar antenna. Data collection included a part of field work, implemented through the acquisition of photographic images and target’s radar detection (by the panoramic terrace Santa Maria in Corniglia), and a part, performed in the laboratory, of data analysis. The work was undertaken between May and November 2018. During this period, 30 days of monitoring were carried out (about 300 h) and about 10,000 radar images were recorded. The first results showed that we were able to recognize the target “cetacean” from the other common targets (boats, buoys, etc.) detected by the radar. In particular 70 dolphins were sighted by visual census; 12 of them were recognized on radar images. Radar images allowed extraction of dolphin dive time (between 2 and 15 s). The next step will be to allow the radar to identify the presence of marine mammals itself since it also works at night and with low visibility. This technique could complement the protection measures of cetaceans, highlighting their presence at sea even if it is impossible with waves higher than 0.8 m and over distances greater than 2.5 km.
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... Community A consists of approximately 45 individuals ( , closed population estimators -Schnabel, 1938Schumacher-Eschmeyer, 1943). Community B consists of approximately 120 individuals ( , open population estimator -Jolly, 1965Seber, 1965) Nuti et al., 2006;Frigerio, 2008). The two different communities seem very different in terms of newborn presence (A>B), average number of individuals per sighting (A>B), individual home range (A>B) and also for the amount of dorsal fin marks (A<B) Saporiti et al., 2008). ...
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Distribution, abundance, and movements of the bottlenose dolphin (Tursiops truncatus) in the Pelagos Sanctuary MPA (north‐west Mediterranean Sea)
Article
  • Jun 2011
  • AQUAT CONSERV
The Pelagos Sanctuary is the largest marine protected area of the Mediterranean Sea (87 500 km2), and is located in the north-west part of the basin. The presence of the bottlenose dolphin in this area is well documented but its distribution and abundance are not well known.The present study collected and analysed data from 10 different research groups operating in the Pelagos Sanctuary from 1994 to 2007. Photo-identification data were used to analyse the displacement behaviour of the dolphins and to estimate their abundance through mark–recapture modelling.Results show that the distribution of bottlenose dolphin is confined to the continental shelf within the 200 m isobath, with a preference for shallow waters of less than 100 m depth.Bottlenose dolphins seem to be more densely present in the eastern part of the sanctuary and along the north-west coast of Corsica.Bottlenose dolphins show a residential attitude with excursions usually within a distance of 80 km (50 km on average). A few dolphins exhibit more wide-ranging journeys, travelling up to 427 km between sub-areas.The displacement analysis identified two (sub)populations of bottlenose dolphins, one centred on the eastern part of the sanctuary and the other one around the west coast of Corsica.In 2006, the eastern (sub)population was estimated to comprise 510–552 individuals, while 368–429 individuals were estimated in the Corsican (sub)population. It was estimated that in total, 884–1023 bottlenose dolphins were living in the Pelagos Sanctuary MPA in the same year.The designation of a number of Special Areas of Conservation (SACs) under the Habitats Directive is discussed as a possible tool to protect the bottlenose dolphin in the Pelagos Sanctuary and in the whole of the Mediterranean Sea. Copyright © 2011 John Wiley & Sons, Ltd.
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