Open sea research

This study focuses on sightings of live cetaceans at sea.

1. Documenting opportunistic sighting reports of cetaceans from sea and shore - Reports are received from various groups of people: lifeguards, surfers, private yacht owners, civilian and military marine patrol vessels and fishing vessels. In cases where species identification is not definite (cetacean expert is not present and no photographic evidence is available) an attempt is made to identify the species by close questioning of the observers, often including browsing through cetacean ID guides. In any event, the exact geographic coordinates of the sighting are taken – or failing these, the distance and bearings from a landmark on shore is used.

          Although such sightings are anecdotal, collecting them over a period of time and marking them
          on a marine chart and/or a bathymetric map (which shows the contour of the sea bed) makes
          it possible to assess the distribution of  the species, areas where there is a concentration
          of sightings which might point to preferred feeding zones, and a possible correlation between
          multiple sightings and sea bed contours such as escarpments, under-water canyons etc.
          To report sightings of marine mammals please call:
          Oz Goffman, executive director of IMMRAC: +972-50-624-1663.

2. Dedicated surveys – As a routine, IMMRAC can not perform systematic, quantitative surveys that may enable an estimation of population size. Such surveys require either an over-flight or a boat with a high platform, traveling along a route that provides systematic coverage of the surveyed area – both methods being rather expensive. Instead, IMMRAC carries out half-day surveys lasting a few hours (mostly during morning hours), either using the 6 m, semi-rigid Zodiac research boat with a crew of up to 6 people or as guests onboard yachts from the Sea-Gal Sailing Club.

          Surveys are confined to certain sea sectors, mostly in the middle of the country and to a distance of up
          to 6NM offshore, on a random course. Information on the presence of bottom-trawlers in the sector
          is available, enabling a close approach to a known source of attraction for common bottlenose dolphins
          (see below), the only species   sighted so far in these surveys. Data collection includes:

• Geographic documentation (according to GPS) of the surveying vessel's course

• Sea state  

• Sighting position of the dolphins

• Group composition and size

• General behavioral categories (traveling, resting, foraging, social interactions etc.)

• Photo ID of individuals

• Underwater acoustic recordings of the sounds made by members of the group.

• Additional observations (presence of sea water fowl etc.)
   

        This data enables the production of dolphin distribution maps, area-utilization models,
        and photographic (and hopefully acoustic signature) catalogues of individuals.
        Derived information includes home range and habitat characteristics (size, site-fidelity,
        utilization and change over time), stability of group composition, association level between
        individuals as well as rough estimation of population size by mark-recapture methods
        (the chance/rate of re-encountering recognized individuals).
 

back