Cetacean Sanctuary Research

Cetacean Sanctuary Research Ligurian Sea

Mediterranean Fin Whale Project

Ecology, status and conservation of pelagic cetaceans in the Pelagos Sanctuary

Target species

Fin whale (Balaenoptera physalus)

Striped dolphin (Stenella coeruleoalba)

Project location

The study area includes the continental shelf and offshore waters of the western Ligurian and Corsican Seas. Specifically, the study area is delimited by Saint Raphael (43°25’N, 6°50’E) on the French coast, Cape Mele (43°55’N, 8°10’E) on the Italian coast and Cape Corse (43°00’N, 9°25’E) and Girolata (42°20’N, 8°35’E) on the island of Corsica. This area of approximately 24,000km2 has a mean depth of 2,300m. The area is characterised by a narrow continental shelf, a marked cyclonic circulation present throughout the year, and strong upwelling currents.

The study area

Rationale behind this study / Research highlights

The fin whale (Balaenoptera physalus) is the only mysticete regularly occurring in the Mediterranean Sea. Genetic analyses performed on Mediterranean specimens revealed the existence of a recently-diverged population characterized by limited gene flow with North Atlantic conspecifics. During the summer months the species is known to concentrate in high numbers in the Corso-Ligurian Basin, described as one of the principal feeding ground for fin whales in the Mediterranean Sea.

Mediterranean fin whales face a number of actual and potential anthropogenic threats, including collisions with vessels, chemical and acoustic pollution, entanglement in fishing gear and disturbance by boats. Collision events are common in Mediterranean waters and may represent a major cause of non-natural mortality for fin whales. In fact, fin whales are the species most commonly struck by vessels worldwide.

Appropriate habitat use and distribution studies, to describe fin whales’ habitat preferences and to investigate the existence of critical habitats for this species, are therefore urgently needed to aid implementation of management measures to regulate naval traffic, fishing and whalewatching within the Sanctuary.

Some of the principal research activities undertaken by the Mediterranean Fin Whale Project since 1990 are listed below.

Habitat use and preferences of the fin whale (1990-1999)

This work has summarized ten years of fin whale effort-weighed sightings in western Ligurian Sea waters. This area plays a key role for the ecology of cetaceans, particularly for whales, representing what is considered to be one of the most important feeding grounds in the Mediterranean Basin.

During searching effort, a minimum of one observer was positioned at each side of the vessel. Observations were made preferably in flat seas and calm weather, defined as “favourable conditions”, and ceased when wind exceeded 3 Beaufort (wind speed = 5.4ms-1). Searching effort start and end times were determined by departure and arriving times, by start and end times of a sighting, by sunrise and sunset or by major changes in weather conditions.

The examined data set consisted of 73,046 km surveyed looking for cetaceans, totalling 540 sightings of fin whales, comprising 942 individuals, encountered in 870 non-consecutive days spent at sea.

Survey effort in years 1990-1999

To provide detailed information on the relative abundance of fin whales, the study area was divided into a square grid of 5 minutes of latitude by 5 minutes of longitude, with a surface area of approximately 62.5km2 each.

Sighting effort was measured by computing the length of the track line surveyed under “favourable conditions” in each 5’ by 5’ cell. Encounter rates were then calculated by dividing the number of fin whale sightings in each cell by the total distance covered under favourable conditions in the same cell. These single values provided an index of fin whale sightings per unit effort. Encounter rates for each year were obtained by averaging all the grid cells sampled on that year.

The research effort, in terms of km surveyed, during the 10-year research period covered 55.6% of the whole study area, but was mainly concentrated in the region closer to the Italian-French coasts and in the lane between the mainland and Calvi, on the island of Corsica.

Distribution of the effort

Fin whale sightings

The sightings appeared to be concentrated in the central portion of the study area, in the zone comprised between Nice, San Remo and the north-western coast of Corsica. The fin whale sightings generally reflect the distribution of the effort, with a higher number of sightings close to the continental coast of Italy and France, in the centre of the study area and along the western coast of Corsica. The encounter rate values tended to be higher in the south-western portion of the area.

Encounter rate of fin whales, weighed on effort

Generalised Linear Models were used to relate fin whale distribution to physiographic variables (mean, range and standard deviation of depth and slope, and distance from the nearest coast) and provided valuable information. Water depth was the most significant variable in describing fin whale distribution, with the vast majority of sightings occurring in waters deeper than 2,000 m.

Mean yearly whale encounter rates were also calculated and showed no significant differences in the first five years (1990-1994), but then steadily decreased between 1995-99. The steady decrease observed in the encounter rates from 1995-99 is cause for concern and stresses the need for further investigations and mitigation measures.

Encounter rates of fin whales beteen years 1989-2000

This study has demonstrated the deep water preference of fin whales in this area, emphasizing the crucial role that this part of the western Ligurian Sea plays in the ecology of Mediterranean fin whales.

These analyses were first performed only on the fin whale data set to assess their feasibility in answering the questions posed. Now their effectiveness has been demonstrated, the data on the striped dolphin (Stenella coeruleoalba), the most abundant odontocete species in the Mediterranean Sea, will be analyzed.

Work in progress is dealing with the construction of cetacean habitat prediction models, exploring the relationships between oceanographic conditions and cetacean distribution. In particular the relationship between biological parameters, including remotely sensed physical parameters (i.e. sea-surface temperature, ocean colour, wind speed), will contribute to the identification of particular areas that could be considered as critical habitats for this and other cetacean species in the Western Ligurian Sea.

References:

Panigada, S., Notarbartolo di Sciara, G., Zanardelli, M., Airoldi, S., Borsani, J.F., Jahoda, M., Pesante, G., & Revelli, E. In press. Distribution and occurrence of fin whales in the Ligurian Sea between 1990-99. European Research on Cetaceans, 15.

Panigada, S., Zanardelli, M., and Notarbartolo di Sciara, G. In press. Conservation issues concerning Mediterranean fin whales. European Research on Cetaceans, 16.

Barale, V., Panigada, S., and Zanardelli, M. 2002. Habitat preferences of fin whales (Balaenoptera physalus) in the North-western Mediterranean Sea: a comparison between in situ and remote sensing data. In: Proceedings of the Seventh International Conference on Remote Sensing for Marine and Coastal Environments, Miami, Florida, 20-22 May 2002.

Panigada, S., Zanardelli Panigada, M., and Hammond, P. In press. Distribution of fin whales in the western Ligurian Sea in relation to physiographic variables. European Research on Cetaceans, 18.

Panigada, S., Notarbartolo di Sciara, G., Zanardelli Panigada, M., Airoldi, S., Borsani J.F. and Jahoda, M. 2005. Fin whales summering in the Ligurian Sea: distribution, encounter rate, mean group size and relation to physiographic variables. Journal of Cetacean Research and Management, 7(2):137-145.

ACCOBAMS. 2006. Report of the Joint ACCOBAMS/Pelagos Workshop on Fin Whales in the Mediterranean Sea. G. Donovan, S. Panigada, C. Guinet (eds.). Monaco, 14-15 Nov. 2005. 35 pp.

Use of GIS and spatial modelling to describe and predict the presence and relative abundance of cetaceans, thus providing valuable information for the management of the area

Aim of this work in progress is to assess critical habitats for cetaceans, which is one of the main needs of the Pelagos Sanctuary for the Conservation of Mediterranean Marine Mammals. The results of this study will provide information for conservation and management in the Sanctuary.

The goal of this study is to model the habitat use and preferences of the two most abundant species in the area, fin whales and striped dolphins. In order to do so, the study area was divided into a 2’ latitude by 2’ longitude grid. The explanatory variables considered in the models are physiographic variables (mean, range and standard deviation of depth and slope, and distance from the nearest coastline) and remotely sensed data (sea surface temperature and chlorophyll a concentration). The former were calculated for each cell using GIS tools, while the latter were obtained via AVHRR and SeaWiFS sensors.

Generalized Additive Models (GAMs) with multidimensional smoothers will be used to model the distribution of fin whales and striped dolphins in relation to these variables, while Classification and Regression Trees (CART) will be used for habitat characterization. Preliminary analysis revealed that chlorophyll, SST, depth and slope appear to be important predictors of habitat use. The techniques applied to this dataset prove to be valuable tools in describing habitat use and preferences of cetaceans, and the use of the remotely sensed data, substantially improves the predictions.

References:

Panigada, S., Zanardelli, M., MacKenzie, M., Donovan, C., Mélin, F., Hammond, P.S. In press. Modelling habitat preferences for fin whales and striped dolphins in the Pelagos Sanctuary (Western Mediterranean Sea). European Research on Cetaceans, 20.

Identification of areas characterized by “high density” of cetaceans to reduce ship strikes and definition of particular zones with increased risk of collisions between ships and whales

Mediterranean fin whales are exposed to a number of threats, including direct human disturbance, anthropogenic noise, pollution and collisions with vessels. The latter represents a considerable source of concern, due to the large and increasing number of ferries and commercial ships crossing the waters of the Ligurian Sea Sanctuary daily. Evidence of collisions has been reported both for stranded and free-ranging fin whales, presenting high percentages of specimens struck by ships.

Evidence of collisions in Mediterranean fin whales from the Ligurian Sea

To assess the impact that ship strikes may have on the relatively isolated population of fin whales in the Mediterranean Sea, a review and analysis of ship collision records from 1897 to 2001 was performed. Records both from dead and photo-identified free-ranging individuals were collected. Out of 287 carcasses, 46 individuals (16.0%) were certainly killed by boats. The minimum mean annual fatal collision rate increased from 1 to 1.7 whales per year from the 1970s to the 1990s. 82.2% of the fatal strike events were reported in or adjacent to the waters of the Pelagos Sanctuary for Marine Mammals.

Ship collision records for fin whales, 1897-2001

Among 383 photo-identified whales from the same area, 9 (2.4%) presented marks that were attributed to a ship impact. The reported rates are unusually high for baleen whales. While the estimated rate of fatal strikes would not threaten the population itself, the high likelihood of unreported fatal strikes combined with other anthropogenic threats suggests an urgent need for a comprehensive, basin-wide conservation strategy for this population, including ship strike mitigation requirements. Mitigation measures might include real-time monitoring of whale presence and distribution to re-locate ferry routes to areas of lower cetacean density, and reducing ship speed in high cetacean density areas.

Future research to describe the whales’ behavior in relation to approaching vessels including controlled-exposure-experiments combined with passive tracking and multi-sensor recording devices would be helpful to further understand and avoid these interactions.

The marked offshore distribution displayed by fin whales in the Ligurian Sea may serve to encourage, insofar as it is possible, the adoption of shipping lanes closer to coasts, thus reducing commercial traffic volume in offshore waters. Cetacean distributional differences throughout the study area should be further investigated to clearly determine whether zones of lower density exist, where ship crossings should occur to minimize their impact.

References:

Pesante, G., Zanardelli, M., Panigada, S. 2000. Evidence of man-made injuries on Mediterranean fin whales. European Research on Cetaceans, 14:192-193.

Panigada, S., Pesante, G., Zanardelli, M., Capoulade, F. 2005. Are Mediterranean fin whales threatened by ship strikes? In: Abstracts of the 17th Biennial Conference on the Biology of Marine Mammals, San Diego, CA, USA, 12-16 December.

Panigada, S., Pesante, G., Zanardelli, M., Capoulade, F., Gannier, A., Weinrich, M.T. 2006. Mediterranean fin whales at risk from fatal ship strikes. Marine Pollution Bulletin, 52:1287-1298.

ACCOBAMS. 2006. Report of the Joint ACCOBAMS/Pelagos Workshop on Large Whale Ship Strikes in the Mediterranean Sea. M. Weinrich, S. Panigada, C. Guinet (eds.). Monaco, 14-15 Nov. 2005. 35 pp.

Diving and foraging behaviour of fin whales while in their principal feeding ground within the Mediterranean Sea through the use of velocity-time-depth-recorders

The aim of this research was to describe the diving behavior of fin whales while in their major feeding ground in the Mediterranean Sea, and relate it to the diel vertical upward migration of the deep scattering layer (DSL). The data were collected during the summer months within a long-term study on the ecology of the species in the area.

Tagging of fin whales

Fifteen fin whales have been tagged between 1998 and 2002, generating over 35 h of dive data. The sensors remained on the body of the whales for different periods of time, varying from few minutes to more than 8 hours. Depths of at least 500 m were recorded repeatedly, and were likely related to feeding; most of the deep dives performed by the whales presented a series of ascending and descending vertical excursions in proximity of the bottom of each dive, with amplitudes up to 50 m. These spikes have been described for fin and blue whales in the Pacific Ocean and in the Sea of Cortez, and have been interpreted as feeding lunges.

Dive profile of a tagged fin whale

Some whales showed a diving/feeding behavior related to the vertical distribution of their principal prey, by remaining close to the surface during most of the day and starting to perform deep dives in the late afternoon, in coincidence with the diel vertical migration of their prey. One whale, tagged from the afternoon to the evening, showed association to the deep scattering layer, following its migration towards the surface and presumably feeding in it.

Dive profiles of tagged fin whales

These data indicate that fin whales may forage opportunistically at deep depths in order to exploit deep prey resources. Mediterranean fin whales, in particular, may have adapted to vertical prey distribution by developing deep-diving capabilities and opportunistic behavioral patterns suited to match diel vertical migrations of their prey. These results represent the maximum depths ever directly registered for any mysticete species. Evidence of deep diving by fin whales substantially challenges our current understanding of the species’ diving capabilities. In light of the maximum depths of dives recorded here, revision is required regarding current assumptions on the feeding ecology and energetics of this and other mysticete species. In addition, the collected data indicate that feeding fin whales in the western Ligurian Sea may be good indicators of the vertical distribution of the DSL, and TDR data can also be used to track the diel vertical migration of Mediterranean krill.

References:

Panigada, S., Zanardelli, M., Canese, S. and Jahoda, M. 1999. Deep diving performances of Mediterranean fin whales. In: Abstracts of the 13th Biennial Conference on the Biology of Marine Mammals, Wailea, Maui, Hawaii, 28 Nov -3 December.

Panigada, S., Zanardelli, M., Canese, S. and Jahoda, M. 1999. How deep can baleen whales dive? Marine Ecology Progress Series 187:309-311.

Revelli, E., Panigada, S., Zanardelli, M., Azzellino, A., and Canese, S. In press. Diving behaviour of Mediterranean Fin Whales using Velocity-Time Depth Recorders. European Research on Cetaceans, 16.

Panigada, S., G. Pesante, S. Oehen and M. Zanardelli. In press. Day and night-time behaviour of fin whales in the Western Ligurian Sea. European Research on Cetaceans, 17.

Panigada, S., G. Pesante, M. Zanardelli and S. Oehen. 2003. Day and night-time behaviour of fin whales in the Western Ligurian Sea. Proceedings of the Conference Oceans 2003, September 22-26, 2003, San Diego, California. Pp 466-471.

Mark-recapture techinique applied to the fin whale in the study area

During the study period a total of 360 fin whales were positively identified, 19% of which were re-sighted, from a minimum of 2 to a maximum of 6 successive times. Recaptures occurred both in the same year and in different seasons with a maximum interval of 10 years. Mark-recapture methods were employed to estimate absolute abundance of the fin whale population present in the study area during summer months. Point estimates for the population ranged from 483 individuals to 491, considering both the time intervals. The results presented are the first fin whale abundance estimates obtained through mark-recapture methods for the Ligurian Sea and, despite the larger confidence interval due to the lower effort of the 1996-1999 period, suggest the stability of the Sanctuary population status.

New whales and re-captures positively identified in the different years of the study period.

Mark-recapture techinique applied to the fin whale in the Western Ligurian Sea: absolute abundance and survival rate estimates as conservation tools

The aim of this project, partially funded by the Whale and Dolphin Conservation Society (WDCS) is to merge in a unique, comprehensive catalogue all the photo identified fin whales provided by different research institutes within the western Ligurian Sea and Gulf of Lions, in order to reach the critical mass needed for applying advanced statistical analyses. The results of this joint project will be to demonstrate the suitability of mark-recapture methods to model the population of fin whales summering in the Pelagos Sanctuary; to achieve absolute abundance estimates and determine possible trends in population dynamics; to describe for the first time the survival rate of Mediterranean fin whales; to determine their habitat use characteristics and site fidelity; to monitor single individuals and assess movements within the feeding area; to compare line-transect surveys with mark-recapture methods. The expected results will represent a powerful tool for conservation efforts of this unique population in the Sanctuary area and in the entire Mediterranean basin.

Fin whale's response to the approach of vessels assessed through passive tracking and evaluation of the adequacy of guidelines proposed for whale watching

In order to assess the reaction of fin whales to the approaching of boats a new, non-invasive, technique of passive tracking was developed and custom-tailored for Mediterranean fin whales in their Ligurian Sea feeding grounds.
The technique is based on the simultaneous determination of:
1) position of the observation vessel,
2) laser-measured distance between the target animal and the observation vessel and
3) azimuth of the target animal, with respect to the observation vessel.

Tracking was combined with timing of the surfacing intervals and data were processed in real time
by a dedicated software (HighWhale)

From 1994 through 1999, 25 fin whales were individually studied to describe and measure short-term responses to the close approach of a fast moving inflatable craft from which biopsy samples were collected.

The research showed different, measurable short-term responses, in terms of ranging behavior and respiration intervals, to the close approach by different kind of boats.Two different swimming-surfacing patterns, supposed to be related to feeding and travelling respectively, were observed. Supposed feeding whales reacted to disturbance by changing their behavior into travelling.

Convoluted routes supposedly related to feeding tend to become linear

Two different avoidance strategies were performed simultaneously by the whales: travel at increased velocity and reduction of the time spent at the surface.

After the disturbance ceased, the surfacing activity never completely reverted to pre-disturbance conditions during one hour of post-exposure control; especially supposed feeding behavior appeared to be indefinitely suspended. Although tolerating the presence of boats, Mediterranean fin whales may actually suffer from uncontrolled human interference, especially during their feeding activities. Results demonstrate the urgent need for whale watching regulations in the Ligurian Sea, particularly as far as presumed feeding whales are concerned.

References:

Jahoda, M., Almirante, C., Azzellino, A., Panigada, S., Zanardelli, M., Canese, S. 1999. 3D tracking as a tool for studying behavior in Mediterranean fin whales (Balaenoptera physalus). In: Abstracts of the 13th Biennial Conference on the Biology of Marine Mammals, Wailea, Maui, Hawaii, 28 Nov -3 December.

Jahoda, M., Lafortuna, C.L., Biassoni, N., Almirante, C., Azzellino, A., Panigada, S., Zanardelli, M. & Notarbartolo di Sciara, G. 2003. Mediterranean fin whale's (Balaenoptera physalus) response to small vessels and biopsy sampling assessed through passive tracking and timing of respiration. Marine Mammal Science, 19(1):96-110.

Passive tracking technique employed on fin whales to evaluate the adequacy of guidelines used during whale watching in the Ligurian Sea Sanctuary

These data are also employed as baseline for the testing of proposed whale-watching codes of conduct.The technique of passive tracking has been used to test the reaction of whales approached by the same kind of inflatable, but manoevred in line with the guidelines for commercial cetacean-watching activities recommended byACCOBAMS. Preliminarily data indicate a weak reaction of the whales, if any, as compared to baseline data. Thus, passive tracking appear potentially useful for further testing the whale's reaction in relation to the "conduct" of the boat, and to different kinds of crafts. The final goal is to provide ad hoc scientific support to the future management of whale-watching in the Sanctuary, and to set the basis for adapting regulations to the ecology of the targeted population.