The Pacific Islands Region (PIR) is home to more than half of the world’s known cetacean (whales, dolphins and porpoises) species that normally use this region on a year around, seasonal or regular basis. Cetaceans have strong cultural significance; they make up a huge component of the overall marine biodiversity, and have high economic importance for a number of ecotourism operators in the PIR. Spinner dolphins (Stenella longirostris) are one of the most commonly reported species’ in the region but due to limited research efforts, a lack of detailed understanding of their life history, geographical range, habitat of individuals, acoustic behavior and populations exists.

Information on the diurnal patterns of spinner dolphins within their resting areas has already been reported globally; and there is a growing concern on the negative impacts of ecotourism on their populations. The rapid development in the tourism industry over the past years prior to any research or management planning taking place has made it a lot difficult to implement appropriate management strategies in the PIR. The presence of ecotourism activities has altered the behavioral patterns of spinner dolphins globally; therefore more investigation is needed to further monitor the impacts of ecotourism on spinner dolphin populations in the region.

A study on “The acoustic communication patterns of a resident pod of spinner dolphins” took place at a tropical reef complex locally known as ‘Makalati’ or Moon Reef, located on the north eastern coast of Viti Levu, Tailevu, Fiji Islands. Makalati Reef falls within the ‘qoliqoli’ (traditional fishing grounds) of the Dawasamu ‘tikini’ (district) and serves as a critical resting habitat to a resident pod of spinner dolphins that visit the reef on a daily basis. The daily presence of spinner dolphins at Makalati Reef has drawn tourists and locals to this destination. A local tourism operator exists in the area and boat trips to the reef occur daily. This single operator is the only dedicated dolphin-watching venture in Fiji and plays an important role to local villages through employment and financial support.

Acoustic signals such as whistles and echolocation clicks were being monitored for this resident population at both daily and seasonal scales over a two year period. This research used a non-invasive approach which involved classifying the six different spinner dolphin whistle types and monitoring the echolocation click rates throughout the day. Part of this research was to further confirm the residency of this population and also investigate whether their resting times were disrupted by the boat traffic from the nearby eco lodge.

Over 7,960 whistles were collected using an on-board hydrophone during three different sampling periods (from September 2012 to October 2013). The whistle types were categorized into six different categories (upsweep, downsweep, concave, convex, sine and constant) with five time and frequency parameters measured from each whistle contour. The whistle rates of spinner dolphins were observed to vary with time of day, mainly increasing in acoustic production with boat presence. Over 10,000 echolocation clicks was detected using a moored passive acoustic monitoring device and the echolocation activity was investigated by regression number of clicks per hour against time of day. Clicks were detected throughout the day but there was no significant (p < 0.181) change in the clicks pattern across day and sampling periods. It is suggested that this resident pod were using echolocation as a form of communication and to coordinate group activity.

This study presents valuable data that will be used to limit the disturbance of the Makalati spinner dolphins and provide significant guidance for sustainable ecotourism management within the reef. Findings from this study further confirms their residency at Makalati Reef, and the scientific information gathered will provide management guidance for building a sustainable ecotourism operation in balance with the appropriate conservation and protection of this pod of spinner dolphins. The information gathered will also be used to convey a broad ecological sustainable plan that will directly benefit, develop and progress the evaluation of the Dawasamu district wide management plan.

Words by Samanunu Simpson