By applying the data gained from this photo-identification project to the Jolly-Seber population model, it has been possible to estimate the size of the bottlenose dolphin population in Boca Ciega Bay. Currently, additional techniques to assess population size are being researched and tested in an attempt to obtain more accurate population estimates. Annual population estimates make it possible to correlate changes in population abundance with various changes in the bottlenose dolphins' habitat. For example, a thirty percent increase in population over one year has been correlated with the implementation of the Florida state ban on commercial netting of inshore waters (July 1, 1995).  See below for more information regarding the Florida Net Ban.

    Foraging ecology encompasses various aspects of the bottlenose dolphin's search and procurement of sustenance. One component of this is how a dolphin finds and catches food, which is studied by examining dolphin foraging strategies and behaviors. What a dolphin eats can be investigated by analyzing prey composition and density. In addition, the study of bottlenose foraging ecology also answers questions about the habitats dolphins utilize for feeding. A variety of factors will be monitored to answer these questions, such as the physical characteristics of the feeding habitat, temporal and spatial aspects of dolphin distribution, prey and predator density, and various environmental variables. Determination of habitats associated with feeding will allow for key dolphin habitats to be pinpointed and for better conservation of these important areas.

    Photo-identification procedures that are required to identify wild animals can be very time consuming. Currently a computer aided photo-identification software program is being refined at Eckerd College to facilitate the matching process. The development of this software program provides a valuable tool to all field researchers on bottlenose dolphins and has possible applications to other marine species. This research is made possible in part by a grant from the National Marine Fisheries Service.

The Darwin Group
Zack Roberts, Dr. Kelly Debure, and Dan Wilkins
Photo by Kari Higgs
 

ACOUSTICS

Principal Researchers - Chris Matterson and Jordan Sanford

    With increasing human population growth along shoreline areas it is necessary to consider the acoustical impacts of development and increased boat traffic on bottlenose dolphin habitat. Are dolphins (animals that rely heavily on their sense of sound for communication, foraging, and navigation) being impacted by the noise pollution found in these urbanized areas? This ongoing study is currently gathering baseline acoustical data in Boca Ciega Bay. In order to pinpoint elevated levels of noise in Boca Ciega Bay it is necessary to first determine what "normal" sound levels are in this area. Future research will examine changes in dolphin behavior due to varying acoustical levels and boat activity. This research is made possible in part by a grant from the Disney Conservation Fund.

Rebecca Goodnight monitors boat traffic and dolphin distribution from the crow's nest on top of the Galbraith Marine Science Laboratory. Photo by Jason Allen

A theodolite is used to determine the location of each dolphin group. Photo by Jason Allen

    Underwater noise created by the discharge of cooling water from the
TECO Big Bend Power Station near Apollo Beach, Florida, will be recorded and compared to ambient noise levels of upper Boca Ciega Bay.  Dolphin vocalizations will be recorded in the same areas that supplied the ambient noise recordings and compared to one another based on intensities. Observations and conclusions will be made between the dolphin vocalization intensities associated with the ambient noise intensities of their respective areas.  It is hypothesized that dolphin vocalizations will be of a much higher intensity near the Big Bend Power Station than they will be on the grass flats of Upper Boca Ciega Bay. This research is made possible by a grant from the Lancy Foundation.

    In order to gain a better understanding of community structure and interaction of the bottlenose dolphins found in Boca Ciega Bay, association patterns, which measure the frequency with which individuals are seen together, are being examined. Association patterns can tell us a great deal about mother-calf pairs, male bonded pairs, female bands, and population structure. Current data suggest the presence of female band(s) (females in the same stage of their reproductive cycle) in upper Boca Ciega Bay and a relatively open population.

    On July 1, 1995 the Florida state ban on commercial netting of the inshore waters (Article 10, section 16) went into effect. The bottlenose dolphin can be used as an indicator species of ecosystem change due in part to the plasticity of its behaviors. Due to the long nature of the ECDP (entering its 8th season) it was possible to compare dolphin distribution, feeding habitat preference, and reproductive rates, both before and after the implementation of the net ban. Results indicate that a 36% increase in population size occurred from 1995 to 1996. In addition, significant increases in mean herd size (p=0.001), sightings with feeding activity (8.2%; p=0.003), and sightings with calves (10.1%; p<<0.001) have been noted. Although causality cannot be proven, these findings are strongly correlated with an increase in some inshore fish stocks due to the Florida state ban on commercial netting of the inshore waters.