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Risso's dolphin harassment by pleasure boaters off the Island of Ischia, Central Mediterranean Sea

Authors:
Angelo Miragliuolo
Angelo Miragliuolo
Barbara Mussi at Oceanomare Delphis
Barbara Mussi
  • Oceanomare Delphis
Giovanni Bearzi at Dolphin Biology and Conservation
Giovanni Bearzi
  • Dolphin Biology and Conservation
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Abstract

An example of the impact of pleasure boating on cetaceans - in this case Risso's dolphins (Grampus griseus) - is presented to highlight the disruptive potential of unregulated human-dolphin interactions in the Mediterranean Sea. The observation took place near the Cuma submarine canyon off the island of Ischia, Italy. In this area, a school of about 20 Risso’s dolphins appeared to be seasonally “resident” and was regularly resighted nearshore, based on photo-identification data collected between 1998-2000. On 27 August 2000, a Risso’s dolphin group incuding 16 adults and 3 calves was first sighted travelling above the 300m depth contour, 0.7 miles from the Ischia coast. This group quickly became the target of an ever-increasing number of pleasure boats, and was eventually “penned” into a large coastal enclosure where about 400 boats were randomly anchored. Between 13:00-15:20 the dolphins were surrounded by up to 100 boats with their engines turned on, on a sea bottom that was only 3m deep. Harassment behaviour by pleasure boaters included heading towards the animals at high speed every time they surfaced, sudden changes of route, and continuous attempts to approach the animals at close quarters to take photographs or “interact” with them. All group members showed clear signs of distress and seemed to be unable to orientate. High-speed erratic swimming, collisions with each other, spinning and swimming in circles with short interblow intervals were recorded. Through a 2h effort, members of StudioMare managed to create an area clear of pleasure boats, and the animals were eventually allowed to head offshore. The occurrence of this kind of dramatic human-dolphin interactions is becoming everyday routine in the busy summer months. Timely management measures are clearly needed in this key area, where productive submarine canyons seem to play a role in the nearshore abundance of cetaceans.
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RISSO'S DOLPHIN HARASSMENT BY PLEASURE BOATERS
OFF THE ISLAND OF ISCHIA, CENTRAL MEDITERRANEAN SEA
Miragliuolo, A., (1) Mussi, B. (2) and Bearzi, G. (3)
(1,2) StudioMare, via D'Abundo 82, 80075 Forio d'Ischia (Napoli), Italy,
(3) Tethys Research Institute, Viale G.B. Gadio 2, 20121 Milano, Italy
Abstract:
An example of the impact of pleasure boating on cetaceans - in this case Risso's dolphins (Grampus griseus) - is
presented to highlight the disruptive potential of unregulated human-dolphin interactions in the Mediterranean Sea. The
observation took place near the Cuma submarine canyon off the island of Ischia, Italy. In this area, a school of about 20
Risso’s dolphins appeared to be seasonally “resident” and was regularly resighted nearshore, based on photo-
identification data collected between 1998-2000. On 27 August 2000, a Risso’s dolphin group incuding 16 adults and 3
calves was first sighted travelling above the 300m depth contour, 0.7 miles from the Ischia coast. This group quickly
became the target of an ever-increasing number of pleasure boats, and was eventually “penned” into a large coastal
enclosure where about 400 boats were randomly anchored. Between 13:00-15:20 the dolphins were surrounded by up
to 100 boats with their engines turned on, on a sea bottom that was only 3m deep. Harassment behaviour by pleasure
boaters included heading towards the animals at high speed every time they surfaced, sudden changes of route, and
continuous attempts to approach the animals at close quarters to take photographs or “interact” with them. All group
members showed clear signs of distress and seemed to be unable to orientate. High-speed erratic swimming, collisions
with each other, spinning and swimming in circles with short interblow intervals were recorded. Through a 2h effort,
members of StudioMare managed to create an area clear of pleasure boats, and the animals were eventually allowed to
head offshore. The occurrence of this kind of dramatic human-dolphin interactions is becoming everyday routine in the
busy summer months. Timely management measures are clearly needed in this key area, where productive submarine
canyons seem to play a role in the nearshore abundance of cetaceans.
INTRODUCTION:
Since 1991, a long-term study on the cetacean fauna off the island of Ischia has been conducted by
Studiomare. The geomorphology of the study area, including productive submarine canyons, seems
to play a role in the nearshore abundance of cetaceans - possibly attracted by local prey availability.
Risso's dolphin (Grampus griseus), striped dolphin, Stenella coeruleoalba, common dolphins,
Delphinus delphis, and bottlenose dolphins, Tursiops truncatus, are seasonally present in these
waters, used as a feeding and breeding ground (Mussi et al., 1998). The area is also used as a
feeding ground by fin whales, Balaenoptera physalus (Mussi et al., 1999).
Risso's dolphins appeared to be seasonally “resident” and was regularly resighted nearshore, based
on photo-identification data collected between 1998-2000.
THE HARASSMENT EVENT:
An example of the impact of pleasure boating on cetaceans is presented to highlight the disruptive
potential of unregulated human-dolphin interactions in the Mediterranean Sea. The observation took
place near the Cuma submarine canyon.
On Sunday 27 August, at about 10:00, dolphins were sighted by pleasure fishermen 0,7 miles off
the southern coast of Ischia. The Risso's dolphin group included 16 adults and 3 calves and was
apparently travelling above the 300m-depth contour.
By 11:00 a number of pleasure boats had joined the travelling group of dolphins. The number of
boats kept increasing (Fig. 1). At 12:00 the Harbour Master's office was alerted, and its officers
contacted StudioMare members to prevent harm to the animals.
By means of the Harbour Master's inflatable we reached the group at about 13:00. By that time, the
animals had moved to the northern side of the island, thus managing to cross and "survive" the
heavy traffic of speedboats and hydrofoils that connects the port of Ischia with the nearby city of
Naples.
StudioMare members found the Risso's dolphin group in Lacco Ameno, a large enclosure and
popular beach were about 400 boats were randomly anchored. The dolphins were surrounded by
over 100 other boats with their engine turned on (Fig. 2).
All these boats kept harassing the animals by heading towards them at high speed every time they
surfaced (Fig. 3), with sudden changes of route and continuous attempts to approach the animals at
close quarters apparently in order to take pictures or “interact” with them.
The animals were increasingly "penned" by the boats into the enclosure, and ended up on a sea
bottom that was only 3m deep. By this time, all group members showed clear signs of distress and
seemed to be unable to orientate. They swam erratically at high speed, with no directionality, often
colliding with each other. One of the at least three calves observed in the group was seen spinning
and swimming in circles, apart from the others.
"Breachings", "surfings", "tail slaps", "head stands" and "spy hops" were repeatedly performed by
several adult individuals. Inter-blow intervals were relatively short (about 60sec). As StudioMare
members tried to prevent a mass stranding by placing the inflatable boat between the animals and
the beach, the group responded by splitting in two tight subgroups, one of which included the
calves. None of the pleasure boaters appeared to realise what was really going on: they all seemed
to be excited to see the animals at close quarters.
THE RESCUE:
Through a two-hour effort, StudioMare members finally managed to create an area clear of pleasure
boats.
As soon as the "opening" was about 400m wide, the animals associated in a single tight group, and
slowly started heading offshore. The group was "escorted" at distance while it moved in safer
waters. At 16:00 the observations were stopped due to unfavourable sea conditions.
DISCUSSION:
The occurrence of this kind of dramatic human-dolphin interactions is becoming everyday routine
in the busy summer months. On the day preceding the reported observation, a disoriented and
distressed lone Risso's dolphin calf was found in the harbour of Mergellina (Naples). Moreover, the
day after the reported observation we found a freshly dead striped dolphin calf with the skull wide-
opened by a propeller strike. He was an 80cm long male.
Interestingly, national newspapers and television often provide quite a different picture to the wide
public. Regarding the Risso's dolphin event, the news reported about dolphins enjoying a "summer
party" in the coastal water of the island.
Timely management measures to protect and conserve cetaceans in this key area are clearly needed.
THANKS TO: Ischia Island Harbour Master
REFERENCES:
Mussi, B., Gabriele, R., Miragliuolo, A. e Battaglia, M., 1998. Cetacean sightings and interaction with fisheries in the
Archipelago Pontino-Campano, South Tyrrhenian sea, 1991-1995. European Research on Cetaceans -12: 63-65
Mussi, B., Miragliuolo, A., Monzini, E., Diaz Lopez, B. and Battaglia, M., 1999. - Fin whale (Balaenoptera physalus)
feeding ground in the coastal water of Ischia (archipelago Campano). European Research on Cetacean - 13: 330-335
Fig. 1 The number of pleasure boats that had joined the travelling group of dolphins kept
increasing.
Fig. 2 The dolphins were surrounded by over 100 other boats with their engine turned on.
Fig. 3 All the boats were heading towards them at high speed every time they surfaced, with
sudden changes of route and continuous attempts to approach the animals at close quarters
apparently in order to take pictures or “interact” with them.
... In almost all cases of disturbance reported, several boats were involved (WDCS 2000, Miragliuolo et al. 2001. Kruse (1991) reports that killer whales move off increasingly quickly as increasingly more boats approach them. ...
... • Interactions between pleasure craft and animals are increasing in a worrying fashion in certain cases. The observation reported by Miragliuolo et al. (2001) instances a resident group of Risso's dolphins harassed for several hours by a number of boats, a phenomenon that seems to be becoming a daily routine in the summer months. • De Stephanis et al. (2000) have shown that little delphinidae (Stenella coeruleoalba, Delphinus delphis) in the Strait of Gibraltar do not appear to see regular line transports as a danger, a fact also noted by Roussel (1999) in the same area and by Angradi et al. (1993) in the Tyrrhenian Sea. ...
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... Studies based on photo-identification in West Provence (Golf of Lyon-Mediterranean Sea) for a part of the population called "resident" showed short movements; 63% of the individuals recaptured were within 50 km (Labach et al., 2015), sometimes recaptured after up to 18 years. However, the wide-range movements for "transient" animals, up to 493 km, were also recorded (Casacci and Gannier, 2000;Miragliuolo et al., 2004;Airoldi et al., 2005;Polo et al., 2009;Remonato et al., 2018). These long-distance movements, from offshore locations to the continental slope habitat, suggest that inter-regional movements are also possible (Delrocq and Gannier, 2016). ...
Submarine canyons as key habitats to preserve Risso’s dolphin (Grampus griseus) populations in the northwestern Mediterranean Sea
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This paper summarises the occurrence of Risso’s dolphin (Grampus griseus) over 12 years (2009 to 2021) in the northwestern Mediterranean. The study was conducted off the central coast of Catalonia (NE Spain) in an area covering 8,026 km² and featuring a system of submarine canyons. The habitat is suitable for a wide diversity of species, including deep-diving cetaceans. In addition, a different dataset from other projects was included to compare distances to the coast from different periods. A visual effort of 8,756 km was carried out with the recording of 17 Risso’s dolphin sightings. The relative mean density of Risso’s dolphin was 0.0078 individuals/km² (SD 0.1, n = 17), and the densities were higher in the southern canyons than in the northern canyons. Furthermore, the distance to the coast and the depth of any sighting were compared by gathering data from different periods and surveys (first period 1985–2014; second period 2016–2021) with 34 sightings analysed. Significant differences were found related to the distance to the coast, showing a displacement of the animals to more pelagic areas between periods. The spatial distribution of Risso’s dolphins was investigated by applying a generalized additive model based on sighting data collected during standardized vessel surveys. Four predictive variables were considered, taking into account the local physiographical features. The model showed that the spatial distribution of Risso’s dolphin in the area was related to the slope and slope variation. The species showed preferences for offshore areas as significant differences were obtained in terms of the distance of sightings to the coast. This paper provides new insights into the distribution of Risso’s dolphin in the central western Mediterranean Sea and identifies the submarine canyons of northern Catalonia as an essential habitat for the species.
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... Communicated by: Thales Renato Ochotorena de Freitas regions (Cañadas et al. 2002(Cañadas et al. , 2005Gannier 2005;Azzellino et al. 2008Azzellino et al. , 2012Azzellino et al. , 2016 and to the Greek area (Frantzis and Herzing 2002;Frantzis et al. 2003;Azzolin et al. 2010). While in the Central Mediterranean Sea, information was limited to the occurrence (Notarbartolo di Sciara et al. 1993;Miragliuolo et al. 2004;Dimatteo et al. 2011;Carlucci et al. 2016) and stranding data derived from the MEDACES database (http:// medaces.uv.es/) and the Italian Stranding Network (http:// mammiferimarini.unipv.it/) . ...
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The residency pattern and site fidelity of Risso’s dolphin Grampus griseus were studied using sightings data collected during standardized vessel-based surveys carried out from 2013 to 2018 in the Gulf of Taranto (Northern Ionian Sea, Central-Eastern Mediterranean Sea). The photo-identification of 91 individuals of G. griseus and the occurrence of re-sighted dolphins up to 8 times provide the evidence that this mid-sized odontocetes persistently occurred in the study area. The presence of transient individuals, visitors, and seasonal residents in the Gulf of Taranto, along with the 29 multi-year resident Risso’s dolphins observed from 2 to 4 times on different years, indicated some degree of inter-annual variability in its temporal use of the area. Moreover, the occurrence of newborns and calves through the study period suggests the possibility to consider the Gulf of Taranto as both nursery and feeding area for females caring for their offspring. The importance of the Gulf of Taranto as critical habitat for the Risso’s dolphin as well as the common bottlenose dolphin and the striped dolphin candidates this area as potential Important Marine Mammal Area, in which enforce specific conservation measures are aimed to mitigate the anthropogenic pressure on different cetacean species according to ACCOBAMS and the MMPATF indication.
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... Ship strikes are a well-known cause of mortality for larger cetaceans, such as whales, but our direct experience documented the impact also for the smaller cetaceans, including striped and bottlenose dolphins (Mussi & Miragliuolo, 2003;Pace, Miragliuolo, & Mussi, 2006). In addition, the impact of pleasure boating on cetaceans, highlighting the disruptive potential of unregulated human-dolphin interactions, is represented by the Risso's dolphin (Grampus griseus) harassment in the study area documented in 2003 (Miragliuolo, Mussi, & Bearzi, 2004). In this study, the significant increasing trend related to depth and distance from the coast in common dolphins' encounters over the study period and the simultaneous decline in ER values may imply that animals are slowly moving away from habitats in which anthropogenic disturbance occurs. ...
The decline of short‐beaked common dolphin (Delphinus delphis) in the waters off the island of Ischia (Gulf of Naples, Italy)
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This study presents data on a local population of short‐beaked common dolphin monitored in the waters off Ischia Island (Gulf of Naples, Italy) over a 16‐year period (2000‐2015). We examine dolphin occurrence and distribution and perform photoidentification analysis. The data presented support the hypothesis that the waters around Ischia Island represent a feeding area, as well as a calving and an important nursery area for this local population, providing favourable conditions in which to give birth and raise calves. The levelling‐off of the photoidentification curves together with the continuous decline of the encounter rate lead us to believe that the area has been a hotspot for a local population (mainly resident) for years and that now this population is dying (has died) or is moving (has moved) to other locations. Several expanding human activities at sea have the potential to impact on the common dolphin in the study area, the most significant possibly being habitat disturbance and degradation (including traffic and noise pollution) and overexploitation of food resources by the fishery. The data presented in this study offer a strong argument for explicit and urgent population‐specific conservation and management strategies to be developed and applied locally for common dolphins, considering that they rely on the region for important biological processes.
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... In fact, to date the knowledge about the presence and distribution of the Risso's dolphin in the Mediterranean Sea is mainly referred to the westernmost regions [8], [9], [10], [11] and to the Greek area, [12], [13], [14]. Whilst, in the Centraleastern Mediterranean Sea information about the presence of this dolphin species was limited to occurrence [15], [12], [16], [17], [18] and stranding data derived from the MEDACES database (http://medaces.uv.es/) and the Italian Stranding Network (http://mammiferimarini.unipv.it/) [7]. ...
View
... It is more difficult to determine possible long-term negative effects of whale watching activities but some hypotheses were proposed. For example, they may have negative effect on health increasing an animal's energy expenditure or resulting in chronic levels of stress [162,163]; long-term alteration or disruption of essential behaviors, such as feeding or resting, may eventually lead to reduced reproductive rates and fitness in the long-term [144,161,[164][165][166][167]; finally, boat-related sound can be drown out or "mask" cetacean vocalizations, with impacts on communication [168]. ...
Cetaceans Value and Conservation in the Mediterranean Sea
Article
Full-text available
  • Oct 2015
This review provides an overview of the Mediterranean diversity and conservation status of cetaceans, and the value associated with their conservation and non-consumptive use. The Mediterranean Sea is one of the world's diversity hotspots; its biodiversity is increasingly under threat in the whole region and key species as cetaceans are under challenge for conservation. All the identified threats are interlinked and cumulatively contribute to the habitat degradation as well as reduced health status of the cetaceans that live there. Whales and dolphins, defined as charismatic megafauna, flag species, apex predators and bio indicators of the marine environment health are demanding social substantial changes. Needs are for spatial prioritization within a comprehensive framework for regional conservation planning, the acquisition of additional information identifying critical habitats in data-poor areas and for data deficient species, and addressing the challenges of establishing transboundary governance and collaboration in socially, culturally and politically complex conditions. This paper also examines research gaps, questions and issues (population abundance estimates, as well as the biological, ecological, physiological characteristics) surrounding cetacean species in the context of biodiversity conservation and highlights the need for targeted conservation management actions to reduce sources of disturbance by key threatening processes in the Mediterranean Sea. The ‘precautionary principle’ must be adopted at all levels in attempts to mitigate impacts and thus provides scope for the translation of the principle into operational measures. As natural entities, cetaceans have their objective intrinsic value, not humanly conferred.
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... Marks from propeller strikes were noted on the backs of whales, and there are documented ship collisions in the area involving four cetacean species, including sperm whale (Centro Studi Cetacei, 1996, 2003Mussi and Miragliuolo, 2003;Pace et al., 2006). The risk of collision is particularly great in the study area owing to its overlap with the Naples harbour traffic and the threat of boat based harassment similar to that reported by Miragliuolo et al. (2004) for Grampus griseus in the coastal waters around Ischia Island. Harassment behaviour by pleasure boaters included heading towards the animals at high speed every time they surfaced, sudden changes of route, and continuous attempts to approach the animals at close quarters to take photographs or 'interact' with them. ...
Occurrence and spatio-temporal distribution of sperm whale (Physeter macrocephalus) in the submarine canyon of Cuma (Tyrrhenian Sea, Italy)
Article
  • Jul 2014
  • AQUAT CONSERV
Boat surveys aimed at studying sperm whales in the Tyrrhenian Sea were conducted between 2002 and 2011. During 768 daily surveys, a total effort of 32 602 km was achieved within an area of 8800 km ² resulting in 92 encounters with 229 sperm whale individuals. Average encounter rates of sperm whales was 0.5 groups per 100 km ² , with a higher concentration in the vicinity of the submarine canyon of Cuma, confirming the importance for the species of this small hotspot in the Mediterranean Sea. Encounter rates increased with increasing distance from the coast. It is possible that the intense boat traffic and anthropogenic disturbance in the area may be moving animals away from the coast leading to habitat loss. The species–habitat relationship documented in this study has implications for conservation. Copyright © 2014 John Wiley & Sons, Ltd.
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Cetacean sightings and interaction with fisheries in the Archipelago Pontino-Campano, South Tyrrhenian sea
  • Jan 1991
  • 63-65
  • B Mussi
  • R Gabriele
  • A Miragliuolo
  • M Battaglia
Mussi, B., Gabriele, R., Miragliuolo, A. e Battaglia, M., 1998. Cetacean sightings and interaction with fisheries in the Archipelago Pontino-Campano, South Tyrrhenian sea, 1991-1995. European Research on Cetaceans -12: 63-65
Fin whale (Balaenoptera physalus) feeding ground in the coastal water of Ischia (archipelago Campano)
  • Jan 1999
  • 330-335
  • B Mussi
  • A Miragliuolo
  • E Monzini
  • B Diaz Lopez
  • M Battaglia
Mussi, B., Miragliuolo, A., Monzini, E., Diaz Lopez, B. and Battaglia, M., 1999. -Fin whale (Balaenoptera physalus) feeding ground in the coastal water of Ischia (archipelago Campano). European Research on Cetacean -13: 330-335