Ilha Formosa: Biodiversity of Cetaceans Inshore of Hualien, Eastern Taiwan

Hsin-Yi Yu|Manager of Cetacean Conservation and Research2024.03.12

Protecting marine biodiversity is a crucial global goal, as highlighted in the United Nations’ Sustainable Development Goal 14, which specifically emphasizes “conserve and sustainably use the oceans, seas, and marine resources for sustainable development." One of the indicators of this goal is to ensure the maintenance of biodiversity and prevent degradation of the marine environment. Cetaceans play diverse ecological roles, including predation and nutrient vectors. They are vital for the functioning and stability of marine ecosystems, and their species diversity and population status are essential indicators of overall marine health.

In this analysis, we examined data compiled by Kuroshio Ocean Education Foundation citizen scientists from Hualien Port whale-watching trips over the past two decades. Species, such as beaked whales (Family: Ziphiidae) and baleen whales (Mysticetes), were identified by experienced captains and crew members onboard; if the identification of uncertain cetaceans lacked description or photographic evidence, the observation record was excluded from this analysis. From 2000 to 2020, there were 8,815 observation records with confirmed latitudinal and longitudinal locations and species identification. These records encompassed 20 different cetacean species, primarily small- to medium-sized odontocetes, with occasional sightings of baleen whales. Baleen whale sightings typically occur from late spring to early summer, whereas several common small- to medium-sized dolphins, such as spinner dolphins (Stenella longirostris) and Risso’s dolphins (Grampus griseus), are observed throughout the year. Records from whale-watching trips were spread across four seasons, resulting in more survey effort and observed species than in short-term systematic surveys.

Table 1. Occurrence of cetacean in each month of the year. "O" represents the commonly observed species throughout the year. The black box indicates occasional sightings (less than five times) in that month.

Table 1. Occurrence of cetacean in each month of the year.
Fig.1. Species richness of baleen whales, deep-diving cetaceans, and Family: Delphinidae.
Fig.1. Species richness of baleen whales, deep-diving cetaceans, and Family: Delphinidae.

As seen in Fig. 1, baleen whales are predominantly found near the northern waters, inshore of Hualien, particularly on the southern side of Qixingtan (七星潭). Fishers often mention the presence of large groups of plankton or small fish near the shore during late spring, possibly attracting baleen whales for feeding. Additionally, humpback whales (Megaptera novaeangliae) may pass through this area during their northward migration. Deep-diving cetaceans, such as sperm whales (Physeter macrocephalus) and beaked whales, are located in regions with steep continental slopes where the water depth drops abruptly. These areas may serve as rich feeding grounds for cephalopods, such as squid, particularly during the nighttime.

The distribution range of dolphin species was the widest, with higher species diversity observed approximately 10 km offshore. Due to the high efforts made by whale-watching trips, cetacean sightings have increased. The complexity of the ocean floor topography and interactions with currents in this area also provides diverse marine environments for various cetacean species.

Whether baleen whales with a diet primarily consisting of plankton and small fish, more opportunistic feeders, such as killer whales (Orcinus orca) and false killer whales (Pseudorca crassidens), or deep-sea diving squid-eaters, such as sperm whales and beaked whales, each species occupies a distinct ecological niche.

Fig. 2. The diversity of cetaceans is a treasure inshore of Hualien. Protecting various cetacean species is also a key goal of the Ocean Oasis Project. (Photographed by Hsin-Yi Yu)
Fig. 2. The diversity of cetaceans is a treasure inshore of Hualien. Protecting various cetacean species is also a key goal of the Ocean Oasis Project. (Photographed by Hsin-Yi Yu)

How can we conserve cetacean biodiversity? The most crucial aspect is maintaining the health of habitats. This includes ensuring an abundance of various food sources, reducing environmental pollution, establishing safe resting areas, and minimizing disturbances along migratory paths. These measures cater to the diverse requirements of various cetacean species. Practical management activities involve reducing terrestrial pollution, monitoring the extent of ocean noise pollution, minimizing the impact of high-speed vessels and discarded fishing gear or debris on cetaceans, regulating the overall quantity of whale-watching activities, and promoting respectful interactions.

Therefore, Kuroshio Ocean Education Foundation advocates the concept of the Ocean Oasis project, which aims to preserve the healthy habitats of cetaceans around Hualien. The goal is to create an environment in which diverse cetaceans are willing to stay and thrive, ensuring that we witness various whale species every year.

 
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