Ionian Dolphin Project Eastern Ionian Sea, Greece

A long-term research and conservation project by the Tethys Research Institute

Bottlenose dolphins and common dolphins photographed by Tethys researchers in the eastern Ionian Sea.

Presentation

The Ionian Dolphin Project is a long-term research and conservation programme conducted by the Tethys Research Institute in the coastal waters of western Greece, in the eastern Ionian Sea.

In 1991 the Tethys Research Institute started a study around the island of Kalamos. Initially meant to be a long-term study on the ecology and behaviour of short-beaked common dolphin Delphinus delphis in a central Mediterranean hotspot, the study documented their sharp decline. Common dolphins declined dramatically from about 150 to 15 animals between 1995 and 2007. Today, only a few individuals can be found within a small portion of their former range. Ongoing actions by Tethys aim to facilitate their recovery in eastern Ionian Sea coastal waters. Common bottlenose dolphins Tursiops truncatus are found in the same area in relatively small numbers, but have stable trends and were studied intensively over the past decade. Ongoing monitoring allows to detect changes in population status and propose timely management measures.

In 2001, Tethys started a parallel study in the Amvrakikos Gulf, where bottlenose dolphins are the only cetacean species encountered. This study showed that about 150 dolphins live in the Gulf. Dolphins in the Gulf seem to be members of a resident community showing major behavioural and ecological differences compared to bottlenose dolphins living around Kalamos. The Gulf also inhabited by loggerhead sea turtles Caretta caretta and has a rich bird fauna including rare species. Research carried out by Tethys is documenting how the local dolphin community interacts with its environment and how human activities - particularly fishing and pollution - may influence its conservation status. This information is particularly relevant in view of the designation of the Amvrakikos Gulf as a National Park.

Research by Tethys is providing support to management efforts in the eastern Ionian Sea, through actions including:

continued monitoring of dolphin groups through field research methods including boat surveys and individual photo-identification, to detect population trends, identify critical habitat, and gain further insight into ways of mitigating the present threats;

research focusing on factors threatening the local ecosystem, particularly with regard to the impact of fishing;

public awareness initiatives (e.g. involvement of a large number of volunteers, “Dolphin Days” and other events organized locally, public presentations, lectures at local schools, video productions);

contacts and meetings with the local Authorities and fishermen organisations, aimed to a) raise awareness on the need to establish measures to protect dolphins and implement the existing regulations (e.g. with regard to illegal fishing activities); and b) identify ways to compensate any losses for fishermen or promote a progressive re-conversion of their activities;

dissemination of information in the scientific literature and provision of sound data and management proposals to international agreements and bodies concerned with the protection of marine biodiversity (e.g. ACCOBAMS, RAC-SPA, IUCN, CMS).

The area of Kalamos was proposed as Marine Protected Area (MPA) at the 3rd Meeting of the Parties to Agreement on the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and contiguous Atlantic Area (ACCOBAMS, 2007). The ACCOBAMS Scientific Committee also recommended the Parties to consider the Amvrakikos Gulf as candidate MPA. Both candidatures were based on evidence provided by Tethys.

Study areas

The study area, centred around the island of Kalamos, is situated in eastern Ionian Sea coastal waters. It is delimited by mainland Greece and the eastern coast of the island of Lefkada, and it includes the islands of Meganisi, Kalamos and Kastos. This area covers approximately 1,000 km2 of sea surface. The sea floor is mostly 50-150 m deep, with rocky coasts and shallows covered by seagrass meadows. Waters are transparent (Secchi disk readings ranging between 10-30m), oligotrophic and unaffected by significant river and agricultural runoffs.

The Amvrakikos Gulf is a semi-closed sea situated in north-western Greece, stretching over about 35 km and covering an area of approximately 400 km2 (excluding its enclosed marshes and lagoons). It is virtually a closed basin as its only link to the open Ionian Sea is a narrow strait, the Preveza channel, 370 m wide and 5 m deep in its narrowest and shallowest points. The sea floor is mostly 30 m deep (max depth 60 m) and covered with mud or sand. The waters are murky (Secchi disk readings ranging between 2-12 m), eutrophic and strongly affected by runoff from the two rivers Louros and Arachthos.

Location and detail of the study areas (light blue) situated in the eastern Ionian Sea, western Greece.

Target species

Short-beaked common dolphin Delphinus delphis

Once one of the most common cetacean species in the Mediterranean, the common dolphin has declined throughout the region during the last 30-40 years. In 2003 the Mediterranean common dolphin population was classified as Endangered in the IUCN Red List of Threatened Animals. In 2006 Mediterranean common dolphins were also included in Appendix I and II of the Convention on the Conservation of Migratory Species (Bonn Convention - CMS). The causes of this generalized decline remain poorly understood but are thought to include prey depletion and bycatch.

Largely based on the presence of common dolphins, the eastern Ionian area around the island of Kalamos has been included by the Greek Ministry of the Environment in the Natura 2000 network ("Sites of Community Importance") under the 9243 EEC “Habitats” Directive. The area around the island of Kalamos has also been identified as one where pilot conservation and management actions should be developed and implemented immediately to preserve common dolphin habitat.

In 2004 ACCOBAMS produced a Conservation Plan for Mediterranean common dolphins, where Kalamos was identified as an area of high conservation importance. The importance of the area of Kalamos was also highlighted in the IUCN 2002-2010 Conservation Action Plan for the World’s cetaceans.

Despite these designations, the formerly resident and abundant common dolphin community living around Kalamos has shown a continuous decline beginning in 1997. Encounter rates of large tuna also showed negative trends. The decline of high-order marine predators feeding on epipelagic prey was consistent with the hypothesis of prey depletion, likely resulting from intensive exploitation of local fish stocks, particularly anchovies and sardines.

Common bottlenose dolphin Tursiops truncatus

Bottlenose dolphins, the most coastal species in the Mediterranean, have been affected in numerous ways by human activities, including culling campaigns to exterminate them in historical times. In recent times, incidental mortality in fishing gear, prey depletion as a result of overfishing and habitat degradation, boat traffic, noise, and health effects caused by pollution are regarded as major threats. Based on a suspected decline of at least 30% over the last 60 years, Mediterranean bottlenose dolphins were proposed for classification as Vulnerable in a recent assessment by the World Conservation Union (IUCN) and ACCOBAMS.

A relatively stable presence of bottlenose dolphins was observed around Kalamos. About 25 animals have shown high levels of site fidelity over the past decade, while others use the area only occasionally. Their flexible feeding habits and opportunistic behaviour may allow them to withstand the effects of overfishing and habitat degradation, but they survive at low densities (approximately 0.6 groups/100km).

An abundant community of bottlenose dolphins lives in the Amvrakikos Gulf. Intensive photo-identification work showed that these dolphins have high levels of site fidelity within the Gulf. Individual movements in and out of the Gulf are limited, probably owing to dramatic differences between the shallow, highly productive, turbid waters of the Gulf and the deeper, oligotrophic, limpid Ionian Sea open waters. Encounter rates in the Amvrakikos Gulf average 7 groups/100km, and population size is about 150 individuals. These values are ten orders of magnitude higher than those found in the area of Kalamos. The Gulf is reportedly facing problems including alteration of water balance, chemical pollution, eutrophication and illegal fishing, resulting in significant ecosystem changes. However, as pointed out previously by Greek researchers Zafiropoulos and Merlini, dolphins appear to be thriving, likely due to the abundance of suitable prey – sardines in particular.

Overview of methods

Visual surveys are conducted on a daily basis by means of inflatable craft with rigid hulls powered by four-stroke outboard engines. Individual photo-identification is used to catalogue dolphins seen in the study area and obtain information on their abundance, movements (e.g. immigration/emigration), habitat use, social organisation and reproductive success.

The position, movements, group size and composition, and behaviour of the dolphins is recorded during long-lasting observation sessions, through a standard behavioural sampling routine. This information is analysed by means of GIS software.

Drifting scales lost by fish prey following predatory events performed at the surface by the dolphins are collected by means of a dip net. The scales - preserved in ethanol 80% - are analysed to identify the dolphin's prey species, by matching them with a scale atlas of known fish species collected in the study area.

The project involves the occasional collection of a limited number of skin samples obtained by means of the non-invasive "skin swabbing" method from bow-riding dolphins, by means of a pole. Skin samples undergo genetic analyses that can generate information on social organization, kinship, mating system, individual gender and identification, movement patterns, stock identity, genetic phylopatry and variability within and among populations. Samples are also obtained from stranded animals.

Marine species (including sea turtles, monk seals, tuna, mobulas, swordfish and seabirds) observed during the surveys at sea are recorded and photographed.

Stranded dolphins found in the study area are inspected, and causes of death identified whenever possible. Biological samples are taken for further investigations. Occurrence of dolphin bycatch in fishing gear is recorded.

The project includes investigations aimed to assess the dynamics of interactions between dolphins and local fisheries, the monitoring of fishing effort. It also includes public awareness and capacity building actions.

Survey effort

Surveys to monitor dolphins around Kalamos were conducted from sailing vessels between 1991-1994, and since 1995 from inflatable boats with fibreglass keels. Surveys were conducted ad libitum in early years. In recent years, pre-defined survey transects are also used for the long-term monitoring of the study areas. All survey transects around Kalamos and those within and outside of the Amvrakikos Gulf were covered at least once per month.

Research effort around Kalamos is normally conducted in the warm season and covers 4 to 7 months per year. Research in the Amvrakikos Gulf is carried out year-round since April 2006.

The Kalamos dataset, 1991 - 2007

Data around Kalamos were collected during a total of 82 months spent in the field across 17 years of research, totalling 1,826 hours spent with 1,718 dolphin groups.

A total of 1,163 daily surveys were conducted in years 1991-2007. The navigation effort totalled 67,043 km. Across 17 years, 499 sightings of common dolphins and 415 sightings of bottlenose dolphins were recorded, totalling 1,718 different groups.

In 1996 we started recording dolphin behaviour, sampled at intervals of 3 min (1996-2001) and then 6 min (2002-2007). Individual dive intervals were also timed between 1996-1999. A total of 22,981 record units (“samples”) of behaviour were recorded: 8,347 for bottlenose dolphins and 14,634 for common dolphins. These samples include position, group size and composition, group formation, directionality and speed of movement, surfacing pattern, dive duration, dolphin activity and behavioural events, presence of birds and bird data, and several other variables.

In addition, a total of 15,352 individual dive times of common dolphins and 5,071 of bottlenose dolphins were timed to investigate dolphin surfacing patterns and feeding behaviour.

Routes surveyed under favourable conditions (“on effort”) around the island of Kalamos in years 1991-2007.

The Amvrakikos dataset, 2001 - September 2007

Data in the Amvrakikos Gulf were collected during a total of 33 months spent in the field over 7 years of research, totalling 558 hours spent with dolphins.

A total of 353 daily surveys were conducted in years 2001-2007. The navigation effort totalled 15,888 km. We made 334 sightings of bottlenose dolphins, and 209 of loggerhead turtles.

Since 2005 dolphin behaviour was sampled based on 5 min observation intervals. A total of 2,857 units (“samples”) of behaviour were recorded. These samples include position, group size and composition, group formation, dolphin activity and behavioural events, presence of birds and bird data, and several other variables.

Individual dive intervals were also recorded starting in 2006, totalling 374 individual dive times, to investigate bottlenose dolphin surfacing patterns and feeding behaviour.

Routes surveyed under favourable conditions (“on effort”) within and outside of the Amvrakikos Gulf in years 2001-2007. Multiple coverage of pre-defined survey transects appear as a single line.

Dolphin encounters

The following figures show the initial positions of dolphin sightings, and dolphin movements in the study area around Kalamos and in the Amvrakikos Gulf.

Sightings of bottlenose dolphins (blue dots) and common dolphins (green triangles) around Kalamos in years 1991-2007. Only the initial position of sightings is shown.

Movements of bottlenose dolphins (blue lines) and common dolphins (green lines) around Kalamos in years 1991-2007.

Sightings of bottlenose dolphins (blue dots) in the Amvrakikos Gulf in years 2001-2007. Only the initial positions of sightings are shown.

Movements of bottlenose dolphins (blue lines) in the Amvrakikos Gulf in 2006-2007.

Photo-identification

Individual photo-identification based on long-term natural marks on the dolphins’ dorsal fins was performed extensively with cameras equipped with 70-200mm f2.8 zoom lenses. Colour transparency film (ISO 100) was used in the early phases of this study, and then digital photography was systematically adopted.

Transparencies were scanned and turned into digital images. Both transparencies and digital photos were then cropped around the dorsal fin and visible part of the body and selected using consistent criteria (e.g. entire fin visible, right angle, appropriate sharpness and resolution).

Following a quality-based selection, the total catalogue 1991-2007 included 61,278 photos on which photo-identification an other analyses were performed.

Number of dolphin photos taken around Kalamos and in the Amvrakikos Gulf in years 1991-2007. Dd = Delphinus delphis, Tt = Tursiops truncatus.

Some of the individual bottlenose dolphins photo-identified in the Amvrakikos Gulf, based on long-term natural marks on their dorsal fins.

Screen capture of one of the database programmes used for dorsal fin analyses.

Photo-identification allowed to obtain information on individual movement patterns, habitat use and preferences, reproductive success, social organization, population abundance and trends of common dolphins and bottlenose dolphins living around Kalamos and in the Amvrakikos Gulf.

Detailed information on population abundance and trends obtained from photo-identification studies is being published in several scientific articles (see Publications), and is not reported here.

Residency patterns of 143 common dolphins identified around Kalamos between 1993 - 2007, based on long-term natural marks on their dorsal fins.

Residency patterns of 98 bottlenose dolphins identified around Kalamos between 1993 - 2007, based on long-term natural marks on their dorsal fins.

Residency patterns of 138 bottlenose dolphins identified in the Amvrakikos Gulf between 2001 – June 2007, based on long-term natural marks on their dorsal fins.

Dolphin feeding ecology

To investigate the diet of dolphins around Kalamos and in the Amvrakikos Gulf, scales lost by fish prey were opportunistically collected when predatory events occurred at the surface. Drifting fish scales could be detected visually up to a depth of about 1 m due to shining as they reflected sunlight. Scales were collected by means of a dip net (mesh size 0.4 mm) and preserved into labelled vials with ethanol 80%, each vial containing one or more scales sampled in a given feeding spot.

These scales are being matched with a catalogue of scales from known fish species collected in the study area.

Fish scales sampled during surface feeding by the dolphins are used for prey identification.

Photographs and direct observations of surface foraging by dolphins also contributed to diet investigations.

A bottlenose dolphin catching a mullet in the Amvrakikos Gulf.

It must be noted that although these methods provide useful insight, they need to be sided by other diet investigation techniques (e.g. stomach content analyses on stranded animals, stable isotope and fatty acid analyses etc.) to account for feeding occurring at depth.

Kalamos area

Since 1997 a total of 79 samples of fish scales drifting at the surface following common dolphin foraging events were collected and stored for diet studies. Fish scales were also collected during surface feeding by other predators (e.g. tuna, swordfish; N=73).

Amvrakikos Gulf

A total of 177 samples of fish scales drifting at the surface following bottlenose dolphin foraging events were collected and stored for diet studies.

An alternative method for the investigation of bottlenose dolphin diet in the Amvrakikos Gulf relies on photos of seabirds (mostly seagulls and terns of several species) feeding on prey being schooled and brought to the surface by the dolphins. Seabirds often congregate in the dolphins’ feeding spots and take advantage of surface prey. Since 2005, birds catching fish near the dolphins are photographed to allow for the visual identification of fish species caught in their beak after successful predatory events.

Terns and seagulls mouthing fish schooled to the surface by bottlenose dolphins in the Amvrakikos Gulf.

Drawings courtesy of Massimo Demma