Colin Kuo-Chang Wen

Ontogeny of behaviour relevant to dispersal and connectivity in the larvae of two non-reef demersal, tropical fish species

In demersal marine fishes, the dispersal of larvae determines the geographical scale of population connectivity, and larval behaviour may influence dispersal. Yet, little is known of the ontogeny of behaviours that can influence dispersal. The present study examined the development of these behaviours in pelagic larvae of tropical marine fishes (4–21 mm) that occupy non-reef habitats as adults: Eleutheronema tetradactylum (Polynemidae) and Leiognathus equulus (Leiognathidae). In the laboratory, critical speed (Ucrit) increased from 3 to 34 cm s–1 at 1.3–1.7 cm s–1 per mm of size, with the fastest larvae up to 50% faster. In situ speed increased from 4 to 25 cm s–1 at 0.7–2.2 cm s–1 per mm, and was 10–14 body length s–1 (60–90% of Ucrit). Endurance increased from 0 to >40 km at 2.4–4.7 km per mm. In the sea, orientation precision did not change ontogenetically, both species tended to swim in loops, and neither significant overall directionality nor ontogenetic change in orientation was present. Larval orientation of these non-reef species was less precise than that of reef fishes. The two species differed in depth distribution, and one ascended ontogenetically. These behaviours can potentially influence dispersal outcomes over the full size range of these larvae.

Effects of habitat modification on coastal fish assemblages.

The purpose of this study was to assess the influence of anthropogenic modification of coastal habitats on fish assemblages in Taiwan, comparing the abundance, species richness and taxonomic composition of fishes on natural v. artificial habitats. While there was no significant variation in the abundance or richness of fishes between natural and artificial habitats, the species composition of fishes in artificial habitats was significantly different from that of natural habitats. Natural reefs were characterized by greater abundance of Stethojulis spp. (Labridae), Abudefduf spp. (Pomacentridae) and Thalassoma spp. (Labridae), whereas anthropogenic habitats were dominated by Parupeneus indicus (Mullidae), Pempheris oualensis (Pempheridae) and Parapriacanthus ransonneti (Pempheridae). In general, it appears that specialist reef-associated species are being replaced with fishes that are much more generalist in their habitat-use. The loss of natural coastal habitats may threaten some species that cannot live in anthropogenically altered habitats, though the overall abundance and diversity of coastal fishes was not significantly different between natural and artificial habitats in Taiwan.

High coral cover and subsequent high fish richness on mature breakwaters in Taiwan

Breakwaters are widely used in coastal development. Breakwaters can alter habitats by undermining shallow coastal ecosystems, especially coral reefs. However, recent studies indicate that mature breakwaters can have well-developed corals and coral-associated fishes. Breakwaters with colonized corals may act as surrogates of natural coral reefs against the global coral crisis. Here, we examined the composition of corals, fishes, and benthic biota/abiota between natural reefs and mature breakwaters to evaluate the possibility of breakwaters supplementing natural reefs. We found equal or higher coral cover, fish abundance, and species richness on breakwaters. Conversely, differential coral growth forms and fish assemblages on mature breakwaters suggested the irreplaceability of natural reefs. Corals and coral reef fishes on mature man-made structures, however, may improve the resistance and resilience of coral reefs. Conclusively, despite high coral cover on mature man-made structures appropriate management (e.g., marine reserves) is still necessary to sustain the coral reefs.

Ain't no mountain high enough: the impact of severe typhoon on montane stream fishes

Typhoons are a regular occurrence in tropical Taiwan. Local flora and fauna should be adapted to typhoons, however more severe storms in the past decade most likely due to climate change have caused an apparent impact on local ecosystems and diversity. Heavy rainfall from typhoon events has been associated with declines in density and biodiversity of low altitude freshwater fish. Montane streams on the other hand are assumed to be more resilient to typhoons as these habitats receive less washed-off pollutant and is buffeted by established vegetation. However, as access to isolated montane streams, especially after a typhoon, is difficult, the effects of typhoons on these habitats are rarely studied. In this study, we overcame many obstacles to survey montane freshwater fishes in Beikeng Creek shortly after a typhoon event. We demonstrated extreme changes in physical characteristics, but little changes in chemical characteristics of the stream. We also documented the absence of the endemic Rhinogobius rubromaculatus (red spotted goby) and the crashed population of Onychostoma barbatulum, (Taiwan shovel-jaw carp) after typhoon. Although these two endemic species are expected to survive in other unaffected montane creeks and streams in the vicinity, the dramatic decline in montane fish population in Beikeng Creek suggests that conservation management may need to be reconsidered to prevent possible extinction under increasing human and natural perturbations.

Can private management compensate the ineffective marine reserves in China

Marine reserves (MRs) have emerged as a preferred method to protect coral reefs from overfishing and human disturbance. However, due to ineffective enforcement by governments, many MRs have been reduced to mere “paper parks” which fail to achieve conservation goals. This is especially true in countries such as China where compliance is low and resources dedicated to enforcement may be scarce. Privately managed marine reserves (PMMRs) may be effective in areas where government enforcement is lacking. To determine if PMMRs are a viable alternative strategy to protect coral reefs, we surveyed and compared fish assemblages and coral coverage in national MRs in Sanya, China to areas of reef privately leased to and managed by dive operators and hospitality industries. We found higher fish abundances and fish sizes in PMMR sites than in MR sites. However, while PMMRs are protected from fishing, other human impacts such as marine debris and illegal coral collection were evident in most tourist sites. Despite protection, long-term monitoring data of PMMRs revealed that in recent years, fish abundances have slightly recovered but species richness has not, indicating the need for a more comprehensive coral reef management plan. We strongly recommend coupling PMMRs with expertise supported regulations as an alternative coral reef management strategy in China.

The effects of four transplantation methods on five coral species at the Sanya Bay

Coral transplantation is considered as one of the major tools to increase coral abundance for degraded coral reefs. To investigate the effects of various methods and coral species in transplantation, coral fragments (n=902) of five coral species were transplanted by four methods at Luhuitou, the Sanya Bay, Hainan Province, China, where the reef has been over-exploited and is still threatened by human activities and natural disasters. Ten months after the transplant, the average survivorship of the transplanted corals was 45.5%. Methodologies had different effects on the transplanted corals, but none of them was efficacious for all coral species. Methodology could not change the decreasing trend for Montipora foliosa and Acropora hyacinthus, although it did slow down their decline. All transplants of A. hyacinthus and M. foliosa had high mortalities and significant decrease on survival area, while Porites andrewsi and Galaxea fascicularis had lower mortalities and partial mortalities. Only one method had significant effect on increasing survival area of G. fascicularis, same as P. andrewsi. Out of the five transplanted coral species, Pocillopora damicornis was the only species that had living tissue area increase in all applied methods, while the others had decreased live tissue area in one or more methods. The results of this study suggested that performing coral transplantation in a highly threatened area was not efficient unless the threats were diminished or erased. Moreover, proper species selection for coral transplantation is crucial, especially in a disturbed environment. Methodology, although having limited effects on improving results of coral transplantation, cannot compensate the maladjustment of vulnerable species to the stresses on the Luhuitou Reef. Coral transplantation on Luhuitou Reef should not be performed unless the stresses are under controlled, and corals with good tolerance to the environment should be considered first.