Common Bottlenose Dolphins Tursiops Truncatus Research Articles

Marine open cage aquaculture in the eastern Mediterranean Sea: a new trophic resource for bottlenose dolphins

Over the last 2 decades marine open cage aquaculture in the Mediterranean Sea has grown rapidly, leading to increased productivity in the water column near fish farms. Here we investigated the effect of such increase in productivity on the common bottlenose dolphin Tursiops truncatus. We developed an ecosystem model for the inner Ionian Sea Archipelago, western Greece, to: (1) evaluate the trophic interactions between bottlenose dolphins and their surround- ing ecosystem, including cage-associated organisms; (2) investigate simultaneously 3 hypotheses that could explain bottlenose dolphin dynamics: (a) increasing fishing effort and changes in ocean productivity, (b) competition with other species, and (c) increase in number of fish farms; and (3) explore spatial trends in bottlenose dolphins distribution using the increased number of fish farms as an explanatory variable. Comparisons of model predictions with historical time-series data indicate that only the increase in number of cages and thereby in productivity near fish farms contributed to the trends observed in dolphin numbers. Spatial analysis also confirmed an increase in occurrence of these dolphins in the proximity of the farms. These outcomes suggest that high productivity in waters surrounding fish cages—within a coastal area that is markedly oligotrophic—may attract bottlenose dolphins. The present study shows that open cage aquacul- ture has benefited bottlenose dolphins by easing their way of catching prey. Further studies should be conducted in other areas of the Mediterranean Sea to investigate whether the higher occurrence of bottlenose dolphins around fish cages is a common pattern and if it is driven by the trophic status of the ecosystem or by the type of fishes that surround the cages.

First record of the Indo-Pacific bottlenose dolphin, Tursiops aduncus, in Korean waters

Bottlenose dolphins (Tursiops sp.) commonly inhabit Korean waters, including the coastal waters of Jeju Island. However, their taxonomic position was unclear because of the validity of this genus. The genus Tursiops has recently been determined to comprise two species: the common bottlenose dolphin (Tursiops truncatus) and the Indo-Pacific bottlenose dolphin (Tursiops aduncus). To confirm the taxonomic position of bottlenose dolphins frequenting the coastal waters of Jeju Island, the external morphology and osteology of specimens from Jeju Island were examined. Photographs of free-swimming individuals were also used for determining external morphological characters. The cranial and meristic measurements fell within the ranges of T. aduncus. Osteological ratios were also consistent with those of T. aduncus. The presence of a prominent ventral spot was observed among some individuals. As a result, the dolphins mainly distributed in the coastal waters of Jeju Island were identified as Indo-Pacific bottlenose dolphins (T. aduncus) in terms of their cranial characters and ventral spotting. We propose a new Korean name, ‘Nam-bang-keun-dol-go-rae’.