| Project Duration | 2011-02-28 ~ 2011-12-29 |
|---|---|
| Research Title | Investigation of Species Composition,Distribution of Fish Egg and Larvae in the Lagoon of the Dongsha Atoll |
| Contracted Organization | National Parks Association, R.O.C. |
| Principal Investigator | Shao Kwang-Tsao |
| Co-Principal Investigator | Chen I-Hsiung |
| Project Participants | Tsai Su-Chen, Chen Ching-Yi, Tsai Cheng-Yi, Ko Hui-Ling, Chang Jung-Hua, Kung Yu-Hai, Chen Kuan-Te, Chang-Liao Nien-Hung |
| Keywords | Fish eggs, fish larvae, Dongsha Atoll |
| Abstract | (1) Background: Dongsha Atoll is Taiwan’s only fully developed atoll, containing diverse habitats such as coral reefs, shallow flats, sandy bottoms, and seagrass beds. Monitoring the ecological recovery and potential of coral reefs within the lagoon is a key basis for future management policies of the Marine National Park Headquarters. Although previous studies have surveyed adult coral reef fishes and published identification guides, research on early life history stages—fish eggs and larvae—has been limited. This project aimed to conduct two to four seasonal surveys within one year to understand the composition, distribution, and community structure of fish eggs and larvae in Dongsha waters. (2) Results: Three seasonal samplings were completed. In each season, four sampling stations were surveyed in the inner lagoon. In the second season, four additional stations were added at the northern and southern channel entrances of the outer atoll; in the third season, only one southern channel station was sampled. Surface and mid-water trawls were conducted for 10–15 minutes per sampling event. A total of 500,989 fish eggs and 3,906 larvae were collected. Based on morphological identification, fish eggs could only be classified into 11 taxa, mostly at the family level. Using DNA barcoding, 123 taxa were identified, including 15 families, 17 genera, and 91 species, comprising 35 families, 68 genera, and 91 species. Egg composition was dominated by Labridae and Scaridae, consistent with adult fish survey results, indicating these families are dominant species within the atoll. Both families showed spawning peaks in June across the three seasons. Community analyses revealed slight differences between inner and outer atoll areas and among seasons. Differences between inner and outer atoll egg assemblages were mainly due to certain species of Scaridae, Acanthuridae, and Labridae occurring only in the outer atoll. Seasonal differences in the inner lagoon were largely attributed to Scaridae and Labridae appearing only in summer and autumn. For larvae, morphological identification recorded 82 taxa (22 families, 27 genera, 33 species), while DNA barcoding identified 110 taxa (19 families, 25 genera, 66 species), comprising 36 families, 68 genera, and 66 species. DNA barcoding significantly improved species identification rates for both eggs and larvae. Larval assemblages were dominated by Pomacentridae and Gobiidae, differing from egg composition because these families generally produce demersal eggs rather than pelagic eggs. Higher hatching success of demersal eggs may also contribute to this pattern. Community analyses showed no significant differences among depths or between inner and outer atoll areas, but seasonal differences were observed within the inner lagoon, mainly between spring and summer–autumn. Station differences were influenced by Myctophidae species and several pelagic species, including Gempylus serpens (Gempylidae), Auxis rochei rochei (Scombridae), and Oxyporhamphus micropterus micropterus (Exocoetidae). Light traps collected 167 late-stage larvae across four seasons, dominated by Fowleria variegata, along with larvae from Schindleriidae, Gobiidae, Tripterygiidae, and Congridae. Over the year, 18 species (14 families, 21 genera) of fish eggs and 22 species (13 families, 20 genera) of larvae were recorded for which no adult records previously existed in Dongsha. In total, 37 species (23 families, 39 genera) without prior adult records were documented. Preliminary results suggest that the inner lagoon may serve as a feeding ground for some species, while surrounding seagrass beds provide settlement habitats for Labridae, Scaridae, and Apogonidae. All data were uploaded to the Dongsha Ecological Resource Database as required. (3) Major Recommendations: Maintain water exchange between the lagoon and surrounding waters to allow replenishment of nutrients and organisms, thereby sustaining biodiversity and ecological resilience. Due to frequent weather and sea condition constraints limiting field operations, strengthening vessels, equipment, and training resident personnel to conduct regular quantitative sampling is recommended. A long-term monitoring program is also necessary to provide reliable data for future management decisions. |
2011, Fish larvae, Dongsha Atoll, Fish eggs