Abstract
Construction-related loss of habitat, degradation of existing habitat, noise pollution, and vessel activity are growing issues for Indo-Pacific humpback dolphins (Sousa chinensis) that occur in the shallow, near-shore, highly industrialized waters off Lantau Island, Hong Kong. We studied the occurrence of dolphins in discrete locations, fine-scale movement patterns, and dolphin behavioral activity states. Potential explanatory variables varied and included year, season, time of day, dolphin group size and behavioral activity state, proximity to construction activity, and vessel type and number. Land-based observations and theodolite tracking of dolphins and vessels were conducted from seven locations to the north of Lantau Island, Hong Kong, and marine construction activities near survey sites were identified. A total of 636 groups of dolphins were recorded, totaling 150.91 h of tracking, from 405 days of observation effort. Hurdle models were used to analyze dolphin occurrence, multivariate generalized additive models were used to analyze fine-scale movement patterns, and log-likelihood ratio and binomialzscorepost hoctests were used to analyze behavioral activity states. Dolphin occurrence was lower in historically important areas near long-term, low-intensity construction activity, and dolphin swimming speed was higher in response to vessel presence. Overall, foraging and traveling were the most frequently observed behavioral activity states and resting behavior was observed off only one location that was not in proximity to construction activities. Temporal overlap in adjacent marine construction areas may displace animals for extended periods and nearby ecologically similar habitats should be identified and designated as marine protected areas to mitigate effects of such disturbance.
Highlights
Ecosystem disturbance may be problematic for small populations of cetaceans that show high site fidelity to areas used for foraging, mating, resting, or calf rearing, where multiple industrial projects overlap (Würsig, 1989; Bejder et al, 2009)
Hong Kong is one of the most densely urbanized coastal regions in the world (Shelton et al, 2013), and ongoing development contributes to anthropogenic noise and activity in the habitats of the Indo-Pacific humpback dolphin (S. chinensis; “humpback dolphins” or “dolphins”; Jefferson et al, 2009; Karczmarski et al, 2016)
Research concentrating on the Pearl River Estuary (PRE) population of dolphins began in the early 1990s (Parsons, 1997; Jefferson, 2000), and data show that the waters around Lantau Island (Figure 1) have historically been an important habitat for dolphins (Jefferson and Hung, 2004; Marcotte et al, 2015)
Summary
Ecosystem disturbance may be problematic for small populations of cetaceans (whales, dolphins, and porpoises) that show high site fidelity to areas used for foraging, mating, resting, or calf rearing, where multiple industrial projects overlap (Würsig, 1989; Bejder et al, 2009). Artificial land (16.5 ha) for the northern landfall for TM-CLKL was formed just off Tuen Mun, which connects with the southern landfall via a subsea tunnel In addition to these projects, the Hong Kong International Airport (HKIA) is constructing a third runway to meet the needs of future air traffic growth. A proactive management approach has been recommended in Moreton Bay to provide protection to the endemic species that occur there (Chilvers et al, 2005) Based on these examples, the effects of construction activity can be measured by assessing shifts in animal behavioral activity states, and spatio-temporal presence and distribution patterns proximate to construction and related vessel activity. We analyzed S. chinensis occurrence in proximity to maritime construction activities, movement patterns in the presence and absence of vessels, and behavioral activity states in discrete locations in the waters north of Lantau Island, Hong Kong. Findings from this study can be broadly informative to areas where small cetaceans and human activity overlap, and where dolphins with small near-shore ranges overlap with heavily populated urbanized coasts where development is diverse and growing
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