Abstract:
The vulnerability of marine fish species, particularly those inhabiting coastal waters, is an increasingly
important issue in marine conservation. Although the weedy seadragon Phyllopteryx taeniolatus (Lacepede, 1804),
a syngnathid fish endemic to southern Australia, is legally protected in New South Wales, there are no studies on
population density, habitat use and behaviour to support this protection.We investigated the abundance, sex ratios
and distribution of the weedy seadragon at three sites near Sydney, Australia. The distribution, density and sex ratios
of seadragonswere temporally stable, suggesting no large-scale seasonal migrations. Estimated population densities
varied among sites from 10 individuals per ha to 65 individuals per ha, with sex ratios close to 1 : 1. Survival rates
from one encounter to the next (approximately weekly) were high, being slightly lower for males (0.985±0.006,
mean±se) and females (0.987±0.005) compared with juveniles (1.000±0.000). All size classes and both sexes
were most common near the border of kelp and sand except when exhibiting hiding behaviour, when they were more
often found in kelp beds. Kelp beds were the least-used habitat when feeding. Pregnant males tended to hide more
often than other groups and therefore were more frequently found in kelp and kelp patches. Seadragons tended to be
solitary, although pairing and grouping behaviour was also observed. Results of the present study show that weedy
seadragons are resident in the same area throughout the year and have a strong affinity with heavily weeded rock
and/or sand habitat. It is therefore recommended that the current species-based protection laws be used in concert
with habitat-protection zones as a necessary measure to ensure the conservation of weedy seadragon populations.
