| Publication Date: 03.02.2004 Publication: The Star Byline: HILARY CHIEW IMAGINE
the delight of finding your precious research specimens in the murky
waters of a seagrass bed after they went out of sight for more than 100
days. It must have been akin to finding the proverbial needle in the
haystack. Such
was the joy of seahorse researcher Choo Chee Kuang when he chanced upon
two of the 250 captive-bred seahorses released into Sg Pulai, Johor,
last September. Set
free in what was probably the first attempt at restocking seahorses in
the world, the two seahorses were discovered during the post-release
field survey of the quirky fish released when they were seven months
old. The
two specimens - a female and a male - appeared to have braved the many
hazards in the wild. One of them even swam across the open, deep
channel to the other side of the river bank. "This
latest finding is most interesting. It sheds new light on the
ecological behaviour of seahorses which were thought to be a
slow-moving and site-faithful fish. Movements could increase the risk
of predation," says Choo. From
their body tags, the two specimens were traced to the batch of 80
seahorses released in the seagrass beds between two tributaries - Sg
Redan and Sg Karang in Johor. The male specimen was found 1km from
across the release site, while the female swam 2km upstream to the
mouth of Sg Redan. Choo
adds that the duo may be the odd wanderers and more data was needed
before he could arrive at any conclusion on this unrecorded habit of
adult seahorses. Besides
the two, a second male specimen was found, but it had no body tag, thus
no study could be made on its range of movements. Headstart As
part of his three-year research project on the spotted seahorse,
Hippocampus kuda, Choo has incorporated a captive breeding programme in
the hope that given a headstart, the released creatures would stand a
better chance of survival in the wild. Two
pregnant males collected from Sg Pulai produced about 400 fries each,
and these were raised in the Fisheries Department's Brackishwater
Aquaculture Research Centre in Gelang Patah, Johor. In
captive conditions, the newborns recorded an impressive survival rate
of 80% up to the first 40 days, but eventually only half of them
remained. A strict regime of three feeding sessions per day was
introduced whereby micro-zooplankton was fed to the juveniles during
the first month. Subsequently, the diet was changed to tiny shrimps. In
selecting the fittest specimens for release, Choo omitted those that
displayed inferior physical features such as a shorter snout, a shorter
tail or were smaller in size. To
enable identification, Choo used a visual implant fluorescent elastomer
tagging system developed by a US company. This tagging system provides
externally visible internal marks for fish and other aquatic animals. The
elastomer is a thick, biocompatible liquid that is harmless when
introduced into the seahorse's body. When injected into the tissue, the
liquid turns into a pliable solid within 24 hours and is supposed to
last the lifespan of the animal. A
combination of coloured elastomers is used to produce a unique coding
system to disclose the origin of the specimen, including its parent and
location of release. The length and weight of the selected stock are
also recorded to shed light on post-release growth. Upon
reaching sexual maturity after seven months in the hatchery, the
specimens - a pair of male and female - were released at 11 different
locations. The selected sites covered a length of 20km from the lower
to the upper reaches of Sg Pulai. Although
releasing specimens from only two parents - resulting in a large number
of individuals from a genetically similar stock - into the wild is
thought to be inappropriate due to the risk of inbreeding, Choo says
the attempt should be viewed as a trial to evaluate the success of
restocking. "If a
considerable number of released seahorses are found in the first three
months, they could be transferred back to the hatchery to prevent
inbreeding. Besides, the released specimens should take a month or two
before reaching full sexual maturity, a period which is thought to be
sufficient for them to disperse and increase the chances of
encountering potential mates in the wild," says Choo. The
timing of the release will also serve another purpose - to determine
the pre-North-East monsoon migration route of the seahorse. "It
was earlier found that seahorses migrate prior to the onset of the
North-East monsoon but there was no indication of their migration
route. Thus a large number of tagged individuals released prior to the
monsoon can provide a glimpse of this movement and the distance
travelled. Carried out over a prolonged period, it may even reveal the
lifespan of seahorses in the wild," adds Choo. Seahorse research elsewhere had indicated that the species, in general, could live up to four years. Choo
has scheduled a monthly survey of up to six months before evaluating
the feasibility of restocking. Individual fitness is assessed through
visual determination of gut fullness and reproductive events, the
presence or absence of parasites or inflicted injury. As a species
where the males carry the fertilised eggs, the brooch pouch in males
expands after mating, providing a visual clue. To
date, Choo has recovered 17 tagged seahorses and all the males were
either pregnant or had already delivered, an early indication of
success. The hatchery-raised seahorses were able to find food, adapt to
their natural environment and reproduce like those in the wild. Information on the biological cycle of the seahorses is vital to any conservation programme that Choo has in mind for the fish. He
reckons that individuals released into the waters would not trigger a
food competition for the wild population. At the moment, the seagrass
beds have the capacity to accommodate the new recruits. Green, green grass of home Sg
Pulai holds the most viable H. kuda population in Peninsular Malaysia
as indicated by an earlier survey on the distribution of the various
species of seahorses. The estuary is unique in that it has a year-round
stable salinity which extends up to 20km upstream, making an ideal site
for Choo's experiment. Elsewhere
in the peninsula, the species is sparsely distributed in Kuala Merbok
in Kedah, Perak's Sg Dinding and in a shallow reef flat at Cape
Rachado, Negri Sembilan. Choo,
a masters student at Kolej Universiti Sains dan Teknologi Malaysia
(Kustem), says the experiment is also a feasibility test on the
viability of restocking to regenerate dwindling populations. The
success of the project is significant in view of developments taking
place in the home ground of the spotted seahorse. Land reclamation
works at the Port of Tanjung Pelepas have encroached into the habitat
of the seahorse, threatening the survival of the little known species. Choo
voices concern over the loss of large tracts of seagrass beds and
changes in the hydro-dynamics of the river basin due to increased
shipping traffic and the deepening of the riverbed to accommodate large
vessels. The natural tidal cycle, he says, ensures that newborns at the
river mouth are carried to the upper reaches of the estuary, while
those in the estuary are flushed out to facilitate gene exchange. "It
is believed that the Pulai estuary serves as a basin for nutrient
precipitation and is particularly important for various marine larvae
settlement. Hence reclamation works will spell disaster for the
species," Choo explains. Subjected
to accidental capture in fishing gear and targeted by the aquarium
trade in the past, the population of the H. kuda has been declining,
and is now estimated to be below 1,000. "As
their habitat continues to be desecrated, it is vital that we find
solutions that can prevent the population from collapsing below a
threshold where they may not be able to self-propagate and, hence, face
extinction. Re-stocking may be the answer to overcome this problem,"
says Choo. "The
salmon, trout, eel and many over-exploited fishes have been produced on
a large scale in the laboratory for release into the natural
environment. The degree of success is promising with improvements in
genomic techniques which increase the genetic fitness of captive-bred
specimens," adds Choo. | 
