Download The life history and ecology of seahorses in the

1
The life history and ecology of seahorses
in the Philippines
DRAFT REPORT
in support of eventual CITES implementation for seahorses in the Philippines
Compiled by Charity Mae Apale1,2 and Sarah Foster1
(1Project Seahorse and 2ZSL-PH)
(Most text extracted from a review of seahorse biology and ecology by
Foster & Vincent 2004, with updates)
Table of Contents
Introduction ........................................................................................................................................................................ 2
Seahorse taxonomy .......................................................................................................................................................... 2
Morphology and crypsis ................................................................................................................................................. 3
Species in the Philippines .............................................................................................................................................. 6
Key Characteristics/Identification ............................................................................................................................. 7
Distribution and habitat ................................................................................................................................................. 7
Density and mobility ..................................................................................................................................................... 10
Life span and mortality ................................................................................................................................................ 11
Feeding and growth ...................................................................................................................................................... 12
Reproduction ................................................................................................................................................................... 12
Reproductive timing................................................................................................................................................. 12
Timing and length of breeding season .............................................................................................................. 15
Mating patterns .......................................................................................................................................................... 15
Egg and clutch size .................................................................................................................................................... 16
Pregnancy ..................................................................................................................................................................... 16
Young and brood ....................................................................................................................................................... 17
Research needed for conservation and management ...................................................................................... 17
Distribution.................................................................................................................................................................. 17
Movement..................................................................................................................................................................... 18
Population size ........................................................................................................................................................... 18
Survival.......................................................................................................................................................................... 19
Reproduction .............................................................................................................................................................. 19
Conclusions....................................................................................................................................................................... 19
Acknowledgements ....................................................................................................................................................... 20
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References......................................................................................................................................................................... 20
Annex I. Description of seahorses in the Philippines ....................................................................................... 27
Annex II. Regional maps of seahorse species distribution with different habitats and fishing area
closures and temporal restrictions in the Philippines..................................................................................... 32
Annex III. Observed geographic distribution, depth & habitat of seahorses in the Philippines...... 51
Introduction
Seahorses (Hippocampus spp.) are among the many genera whose life histories might render
them vulnerable to overfishing or other disruptions such as habitat damage. They are generally
characterized by a sparse distribution, low mobility, small home ranges, low fecundity, lengthy parental
care and mate fidelity (Foster&Vincent 2004). In addition, the male seahorse, rather than the female,
becomes pregnant. Indeed, curiosity about this phenomenon explains why currently more is known
about reproduction than about other life-history parameters. Such life-history characteristics
(notwithstanding exceptions to these generalities) may help explain why seven seahorse species in the
Philippines are listed as „Vulnerable‟ on the 2015 IUCN Red List of Threatened Species: H. barbouri,
H. comes, H. histrix, H. kelloggi, H. kuda, H. spinosissimus, and H. trimaculatus (IUCN 2015-4). The
other three species are listed as „Data Deficient‟, which reflects substantial gaps in knowledge even for
heavily exploited seahorses, such as the pygmy seahorses: H. bargibanti, H. denise, and H. pontohi.
This report aims to synthesize existing information on seahorse life history and ecology in the
Philippines to promote management derived from the best-available biological knowledge.
Understanding seahorse life history becomes particularly important now that changes in the New
Fisheries Code or Republic Act 10654 Section 102 (b) mean that aquatic species listed on Convention
on International Trade in Endangered Species (CITES) Appendix II will now be subject to export,
unless scientific advice determines that such trade would be harmful to wild populations; all seahorse
species are listed on Appendix II of CITES (see report on „Exploitation, trade, conservation and
management of seahorses in the Philippines‟ for more on this). Assessing the sustainability of
seahorse exports under CITES, and the fisheries that catch them, requires knowledge of their biology
and ecology.
Seahorse taxonomy
Seahorses are bony fishes (teleosts), complete with gills, fins and a swim-bladder (Lourie et al 1999).
Seahorses comprise one genus (Hippocampus) of the family Syngnathidae, which otherwise
consists of about 55 genera of pipefishes, pipehorses and seadragons (Kuiter 2000). The entire family
Syngnathidae falls within the order Gasterosteiformes (Vari 1982; Fritzsche 1984; Palsson&Pietsch
1989; Nelson 1994; Orr 1995) (Figure 1).
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Morphology and crypsis
All seahorses have the same basic body morphology and function: a horse-like head positioned at a
right angle to an erect body; eyes that swivel independently; a long tubular snout (no teeth) that sucks
food; a digestive tract without a differentiated stomach (Rauther 1925; Stoskopf 1993); skin (no scales)
stretched over a series of bony plates visible as obvious rings around the trunk and tail; and a prehensile
tail (Gill 1905). Adult seahorses have no pelvic and caudal fins, and retain only one propulsive dorsal
fin, two small ear-like pectoral fins used for stabilization and steering, and a reduced anal fin
(Foster&Vincent 2004) (Figure 2).
Size is a very important biological variable and measuring the sizes of focal organisms is a vital part of
studies on growth and reproduction, ecology, behavior, habitat selection, the effects of tagging or other
experimental manipulations, as well as for systematics, population assessments and constructing
fisheries models (Lourie 2003). For studies to be repeatable and comparable it is essential that
specimens be measured using standard methods.
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Figure 2. The parts of a seahorse. Figure extracted from Loh et al 2014.
The height measurement (Ht) is commonly applied to seahorses when measuring size, particularly
when live or in a field situation (Lourie 2003). This measurement is defined as the vertical distance
from the tip of the coronet, to the tip of the outstretched tail, with the head held at right angles to the
body (Figure 3; Lourie 2003). Height is the most intuitive way to represent seahorse size but can be
difficult to measure on a dried seahorse that cannot be straightened (Lourie 2003). In the Philippines,
maximum heights recorded for seahorses ranged from the tiny H. pontohi (1.4 cm) to the large H.
kelloggi (28 cm) (Lourie et al 2004; Lourie&Kuiter 2008) (Table 1).
Table 1. Maximum heights recorded for species of Hippocampus in the Philippines
Species
Maximum recorded
height (cm)
Reference
H. pontohi
H. denise
H. bargibanti
H. barbouri
H. histrix
H. kuda
H. trimaculatus
H. spinosissimus
H. comes
H. kelloggi
1.40
2.1 0
2.40
15.0
17.0
17.0
17.0
17.2
18.7
28.0
Lourie&Kuiter 2008
Lourie&Randall 2003
Gomon 1997
Lourie et al 1999
Masuda et al 1984
Lourie et al 1999
Masuda et al 1984
Nguyen&Do 1996
Meeuwig in litt to S. Foster
Kuiter 2000
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Figure 3. Height (Ht) and standard length (SL) as measured on a seahorse (figure by S. A. Lourie).
Project Seahorse has developed a more pragmatic measure for seahorse size – torso length (TsL)
(Loh et al 2014). Torso length is the distance between the top of coronet and the base of the dorsal fin
(Figure 4), and does not require manipulating the tail into a straightened position (very difficult to do in
live animals, and impossible in dried).
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Figure 4. iSeahorse torso length (TsL) measurement and key identifying characteristics of a seahorse.
Seahorse weights vary with reproductive stage, increasing considerably for females that are carrying
eggs and for males that are pregnant (Lourie et al 2004). Some species are sexually dimorphic in
length, with males longer than females, and many are sexually dimorphic in proportions, with males
having longer tails and females‟ longer trunks (Foster&Vincent 2004).
Seahorses have excellent camouflage capabilities, with crypsis probably facilitating both prey
capture and predator avoidance. They remain virtually immobile for much of the time, can change
color over a few days or weeks to match their background better, and sometimes have long skin
filaments to blend better with their habitats. Short-term color changes may also occur during courtship
and other intra-species interactions (Foster&Vincent 2004).
Species in the Philippines
Currently, there are ten known seahorse species in the Philippines: H. barbouri (Barbour‟s
seahorse), H. bargibanti (Bargibant‟s seahorse), H. comes (Tiger tail seahorse), H. denise (Denise‟s
pygmy seahorse), H. histrix (Thorny seahorse), H. kelloggi (Kellogg‟s seahorse), H. kuda (Yellow
seahorse), H. pontohi (Pontoh‟s pygmy seahorse), H. spinosissimus (Hedgehog seahorse), and H.
trimaculatus (Three-spot seahorse) (Annex I).
There are 14 known species in SE Asia and so it is possible that the number of seahorse species in the
Philippines may increase in the future. Indeed the number of known species increased as recently as
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2013. In April of that year photographs from the Philippines of a weedy pygmy seahorse (H. pontohi)
were submitted to the iSeahorse website (www.iSeahorse.org), which gathers sightings from the public,
and have been verified as the first record of this species in the country. The seahorses were spotted near
to the island of Romblon, which is one of the provinces that surround the Verde Island Passage. This
species was previously only known to inhabit Indonesian waters. The new observation updated the
number of seahorse species known to inhabit Philippine waters to a total of ten.
Another pygmy seahorse species (H. severnsi) was spotted in Romblon, same site where divers
photographed H. pontohi. However, this species shares most meristic characters, proportions, body
ornamentation with H, pontohi (Lourie&Kuiter 2008). The only distinguishing characteristic between
the two is color, which normally is not considered as distinctive description. Project Seahorse therefore
considers H. severnsi as a synonym species to H. pontohi (Lourie et al in prep).
Key Characteristics/Identification
The ease of seahorse specimen identification varies from species to species. Very few species (e.g.,
H. bargibanti) are morphologically distinctive enough from other species to be immediately
identifiable, but many species such as H. trimaculatus, have distinguishing characteristics that allow
them to be readily identified (Lourie et al 2004). The seven common large species in the Philippines
can be broadly divided into three groups – “spiny”, “smooth”, and “pygmy”. Spiny seahorses have
spines or spikes covering their bodies, while smooth seahorses do not have (iSeahorse.org: SE Asian
Seahorse ID Guide – Annex I). Pygmy seahorses are significantly smaller than other seahorse species.
Spiny: Hippocampus barbouri is a spiny seahorse with a well-developed usually sharp eye spine and
has double cheek spines. Its similar species include spiny H. histrix, which has longer snout, shaper and
often dark-tipped body spines, and H. spinosissimus with deeper body and its cheek spines usually are
single while the nose spine is less prominent. Another spiny seahorse is H. comes, but it has rugged
spines on body, low coronet and the tail can look blotchy or striped.
Smooth: Hippocampus kelloggi and H. kuda are both smooth seahorses and are considered similar
species, however, the latter has a deeper body with fewer tail rings and more rounded coronet. Another
smooth seahorse is H. trimaculatus, which has hook-like cheek and eye spines, and sometimes has
three dark spots along back of the body.
Pygmy: The three remaining species – H. bargibanti, H. denise and H. pontohi – are pygmy seahorses
which are tiny and well camouflaged. Hippocampus denise and H. bargibanti are somewhat similar
species, but the latter has few or no tubercles, no coronet and has a longer snout. Hippocampus pontohi
is much less robust overall than H. bargibanti and lacks the latter‟s very large tubercles and bulbous
snout tip (Lourie&Kuiter 2008).
Distribution and habitat
Seahorses are found world-wide, usually in relatively shallow, coastal tropical and temperate waters.
Most species are fully marine although some live in estuaries where they experience fluctuating salinity
(Whitfield 1995). Many species in temperate and tropical regions live among seagrasses or eelgrasses
while others occur in flooded mangrove forests. Seahorses also live in soft-bottom areas where sponges
and sea squirts are abundant, and are found among coral in the tropics (Lourie et al 1999).
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Seahorses are found throughout the Philippines (Figure 5 and Annex II.1-II.18). The Philippines is
an archipelago comprised of about 7,500 islands (Mayuga 2016). The country‟s marine waters contain
important marine habitats – coral reefs, seagrass beds, and mangrove forests – and these habitats are
where seahorses are mainly found. Seahorses are found throughout the country (Figure 5) with
recorded sightings even from the northernmost region or Cagayan Valley (Annex II.3) and the
southernmost region or Soccsksargen (Annex II.15).
Project Seahorse has been active in the Philippines for almost 20 years, with activities focused on the
Danajon Bank in the central Philippines, which explains the richness of seahorse distribution data in
northeastern part of Bohol as well as the defined coverage of the coral reefs and mangrove forests
(Figure 5, Annex II.9). With the launching of iSeahorse-Philippines in 2013, Project Seahorse‟s work
scaled up to national level empowering citizens on a grander scale. Observations from citizen scientists
and submitted to iSeahorse prove that there are seahorse species recorded outside from previously
known range. Regional maps indicating the distribution of ten seahorse species in the Philippines, with
different habitats, are found at the end of this report (Annex II.1 – 18).
In the Philippines, seahorses primarily occupy inshore habitats (Annex III). Three seahorse
species (H. kuda, H. barbouri and H. histrix) are known to occur in seagrass beds, sandy sediments,
and hard and soft corals. But there are seahorse species spotted in deeper waters (H. spinosissimus, H.
kellogi and H. trimaculatus). These seahorses area usually associated with octocorals and deeper sandy
bottoms. In contrast, pygmy seahorses, H. bargibanti and H. denise live only on gorgonian sea fans
(Annex III) (Lourie et al 2003), and H. pontohi found among bryozoan, hydroid crops and specifically
the coralline algae Halimeda and hydroid Aglaphenia cupressina (Lourie&Kuiter 2008). Seahorses in
the Philippines are also found on anthropogenic habitats, for example crab traps, gill nets and
enclosure pens set on seagrass beds and coral reefs (Pajaro&Vincent 2015).
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Figure 5. Seahorse species distribution map with coastal habitats in the Philippines.
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Some seahorses change habitat and depth choice as they grow. Hippocampus comes were thought
to prefer Sargassum spp. beds in shallow subtidal environments as juveniles, and then move to adjacent
communities composed of hard corals and sponges when older (Perante et al 1998).
Most seahorses grasp holdfasts with their tail (Foster&Vincent 2004). Holdfasts could be anything
from a sponge to a branching coral, a piece of seagrass or a submerged tree branch. In the Philippines
some species exhibited preferences for particular holdfasts for example, H. comes usually grasped
sponges in communities dominated by seagrasses (J. Anticamara unpub data) while others exhibited no
obvious preference (Perante et al 2002).
Most seahorse species studied to date were active during the day. Documented diurnal species
included H. kuda (Do et al 1998, ex situ). Hippocampus comes in the Philippines may also have been
active during both day and night, but were most commonly seen at night on reefs, when they emerged
from the corals (Perante et al 2002). Hippocampus denise is more active than H. bargibanti and can be
often be seen during daytime observations swimming across the surface of the seafan on which it lives
(Lourie et al 2003).
Seahorses in the Philippines have been found as shallow as 0.5 m and as deep as 75 m (Annex III).
For example fishers reported catching seahorses at different depths (references in Annex III): H.
barbouri, and H. kuda at about 0.5 to 4 m; H. spinosissimus and H. trimaculatus from 5 to 20 m; H.
kelloggi in waters estimated to be as deep as 35 to 75 m; and H. comes was reportedly landed both in
shallow water and water as deep as 20 m.
Density and mobility
Seahorse densities tended to be low and they are patchy in distribution (Foster&Vincent 2004).
Reported seahorse densities could be similar in fished and unfished populations, but the low densities
in at least some populations probably derived from overexploitation (Foster&Vincent 2004). For
example, Filipino fishers reported patchy H. comes densities as high as 20m-2 on coral, or 10m-2 in
seagrass in the 1960s (Pajaro&Vincent 2015), while they were found at only 0.02m-2 in the late 1990s
(Perante et al 2002). Densities of H. spinosissimus were approximately five times more abundant than
H. comes, which may represent real differences in the population sizes of these niche-separated
congeners (Morgan 2007). Densities of the other seahorse species in the Philippines are unknown.
Most seahorse species studied thus far maintained individual home ranges, at least during the
breeding season (Foster&Vincent 2004). As two examples, H. comes often ranged only 1m2 on coral
reefs at night (Perante et al 2002), although they moved considerably more on seagrass beds (J.
Anticamara unpub data), and H. kuda had overlapping home ranges of 32-35 m2 in a tropical eelgrass
bed (C. Choo unpub data). While most species studied to date made limited daily movements, adults of
some species may have made seasonal migrations to deeper waters in the winter months
(Foster&Vincent 2004), including H. comes (J. Meeuwig unpub data).
Adult dispersal over large distances appeared primarily to occur when adults were cast adrift by
storms or carried away while grasping floating debris (Foster&Vincent 2004). Young seahorses are
more likely to disperse than adults. Some species were clearly planktonic immediately after birth, as
juveniles were found in plankton samples. Juveniles of other seahorse species were inferred to be
planktonic because they were positively phototactic immediately after leaving the pouch, rising to the
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surface of the water column in captivity, or not settling immediately after birth in the wild
(Foster&Vincent 2004). Philippine species that are known or inferred to be planktonic after birth
include H. bargibanti (inferred), H. comes (known with 9.66-16.58 mm pelagic duration), H. kuda
(inferred with 19-22 days pelagic duration) and H. spinosissimus (known with 6.52-23.8 mm pelagic
duration) (refs in Foster&Vincent 2004).
Recent studies of seahorse population genetic structure over a range of dispersal distances produced
conflicting results, according to species, the geographic region and the molecular marker used
(Foster&Vincent 2004). For example, H. comes in the central Philippines appeared to have restricted
gene flow based on microsatellites over a distance of 135km, through isolation by distance (Casey
1999). Deep genetic breaks were found among individuals of both H. kuda and H. trimaculatus
collected only 800 km apart in Southeast Asia based on cytochrome b sequencing (Lourie et al 2004).
In contrast, the same study of H. trimaculatus revealed identical genetic haplotypes across distances of
up to 10,000 kms along the Asian continental shelf, suggesting extensive gene flow over the 10,000
years (Lourie et al 2004). A similar study, also using cytochrome b sequencing across Southeast Asia,
shows distinct phylogenetic breaks within H. barbouri, but extensive gene flow in H. spinosissimus
(Lourie et al 2005).
Life span and mortality
Inferred life spans for seahorse species ranged from about 1 year in the very small species to an
average of 3 to 5 years for larger species (e.g. H. comes, J. Meeuwig unpub data, in situ; Morgan
2007) (Foster&Vincent 2004). As with life span, natural mortality rates were unknown for almost all
seahorse species (Foster&Vincent 2004). Hippocampus comes was estimated to have a high rate of
natural mortality (M = 2.7, Morgan&Vincent 2013).
Sub-adult and adult seahorses are presumed to have few natural predators because of their
camouflage capabilities, and unpalatable bony plates and spines (Lourie et al 1999). Predation
coinciding with high syngnathid densities suggests their predators are foraging opportunistically rather
than targeting syngnathids as prey (Kleiber et al 2010). Invertebrates, fishes, sea turtles, waterbirds and
marine mammals were all syngnathid predators (Kleiber et al 2010). Seahorses were preyed upon by
anglerfish, flatheads and sea urchins (Kuiter 2000). Predation by such pelagic fishes suggests that
seahorses may be found in the open ocean more regularly than previously thought (Kleiber et al 2010).
In one account of predation by pelagic stingray, stomach contents included both seahorses and
sargassum weed (Wilson&Beckett 1970). While predators may have ingested sargassum-associated
prey in a demersal zone, it seems more likely that the seahorses were attached to floating sargassum in
pelagic waters: such rafting of seahorses associated with floating plant material has been reported
(Sharpe 1998). A seahorse was also recorded from the stomach of a loggerhead seaturtle (Burke et al
1993), and seahorses were taken by cormorants, penguins and other water birds (Kuiter 2000). Partial
predation by crabs may be a threat to seahorses, as indicated by direct observations of seahorses with
shortened tails (Baum et al 2003; A. Vincent, pers. obs.). Predation mortality was probably greatest in
juveniles that were highly vulnerable to piscivorous fish and planktivorous organisms (J. Curtis pers
comm, A. Vincent pers obs).
Reports of disease in seahorses arose from laboratory and aquaculture observations. Health
ailments included those caused by bacteria (H. kuda, Alcaide et al 2001; Greenwell 2002), trematodes
(H. trimaculatus, Jiwei 1982) and marine leeches (H. kuda, de Silva&Fernando 1965).
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Feeding and growth
Seahorses are ambush predators, and consume primarily live, mobile prey types (James&Heck
1994; Bergert&Wainwright 1997). When feeding within the water column, they wait until prey comes
close to the mouth, whereupon, they are drawn up into the long snout with a rapid intake of water
(Foster&Vincent 2004). They ingest any organism small enough to fit into their snout; mostly small
crustaceans such as amphipods, but also fish fry and other invertebrates (Boisseau 1967; Tipton&Bell
1988; Do et al 1998; Teixeira&Musick 2001). Wild seahorses do not appear to target plants or algae
(H. trimaculatus, Do et al 1998).
Growth rates for seahorse species have not been investigated in any detail. There were few data on
growth rates in captivity, and even fewer in the wild, with none of the data covering enough of a size
range to give a clear picture of lifetime patterns of seahorse growth. The average growth of H. comes in
captivity was reported at 0.66 mm day-1 (Job et al 2006), which is substantially less than that of H.
kuda, which averaged between 0.90 and 1.53 mm day-1 in terms of standard length (Job et al 2002).
Reproduction
Available information on reproduction for Philippine seahorse species is summarized in Table 2.
Reproductive timing
Smaller seahorse species mature at younger ages than larger seahorse species. Smaller seahorse
species appeared to mature at 3 months (Strawn, 1953). Hippocampus barbouri reached maturity at 4
or 5 months (Wilson&Vincent, 1998), while many other species were thought to start breeding in the
season after birth, at 6 months to 1 year (H. kuda, Jiaxin, 1990; H. spinosissimus, H. trimaculatus,
Truong&Nga, 1995; H. comes, J.J. Meeuwig, unpubl. data).
For seahorses, body size served as a better predictor of first maturity than age of individuals
(Foster&Vincent 2004). For example, H. trimaculatus populations in the South China Sea and North
China Sea both matured at the same size, but the former were three months old while the latter were
five months old (Cai et al 1984a). Seahorse size at maturity was closely correlated with seahorse
maximum height, and seahorses showed the same relationship between size at first maturity and
maximum size as other marine teleosts (Foster&Vincent 2004).
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Table 2. Reproduction information for seahorses in the Philippines (extracted from Lourie et al 2004; Lawson 2014)
Species
Breeding Season
H. barbouri
Height
at
physical
maturity
(cm)
8.0
Height at
sexual
maturity
(cm)
8
H. bargibanti
Year round
1.3
H. comes
Year round in the
central PH
8.1
8
H. denise
Pregnant males
have been found in
February, May &
October (suggesting
a year-round
breeding season)
1.1
1.33
7.9
H. kelloggi
15.0
Breeding
year round
season
Length at
birth
(mm)
Brood
size
Young SH
12-14 days
5
10-250 in
captivity
average 2
weeks
average 2
34 from
one male
planktonic
(inferred)
Tackett in litt to Foster (2002),
Whitley (1970)
2-3 weeks
9
200-350
planktonic
immediately
after birth
Lourie in litt to Foster (2003)
Perante et al. (1998)
Perez-Oconer (2002), Warland (2003)
Lourie and Randall (2003)
Lourie et al. (1999)
14.9 – 18.6
14.0
Lawson (2014)
Lourie et al. (1999)
17 days
7
H. pontohi (H.
severnsi)
max
reported:
1405
Pelagic
duration of
larvae: 19-22
days
11
embryos
H. spinosissimus
(H. alatus)
Year
peaking
October
round,
May to
H. trimaculatus
Breeding
season
year round, peaking
March to May and
in October
Reference
Lourie et al 2004
H. histrix
H. kuda
Gestation
Duration
9.4 –
10.5
10.4
9.02
–
9.08 cm
11.6 – 12.8
cm
max
reported:
683
16 days
average 6
mm
max
reported:
1783
Truong and Doan (1994), Mi et al. (1998),
Foster and Vincent (2004),
Jiaxin (1990)
Lourie and Kuiter (2008)
Pelagic
duration of
6.52-23.8 mm
Truong and Doan (1994), Truong and Nga
(1995),
Lawson (2014), S. Morgan, unpub data
Truong&Nga (1995), Cai et al. (1984),
Foster&Vincent (2004), Nguyen& Do
(1996), Lawson (2014)
14
Conservation concern and pragmatism will dictate that the presence of a fully developed pouch
will still be a key index of sexual maturity. In seahorses the most commonly used determinant of
sexual maturity was the presence of a fully developed brood pouch in the males (Perante et al 1998;
Wilson&Vincent, 1998; Baum et al 2003). The only species that lack externally obvious pouches are
the pygmy seahorses H. bargibanti and H. denise (Lourie&Randall, 2003). While this variable allows
one to infer maturity without having to kill the animals, the developed brood pouch may not indicate
physiological maturity. In H. trimaculatus, for example, the first fully developed brood pouch appeared
at 80–90 mm Ht, but dissection of the testes revealed the size at first maturity to be 120 mm Ht (Cai et
al 1984a). As an alternative, some studies defined sexual maturity as the size of the smallest recorded
pregnant male (Nguyen&Do 1996). This method also presented problems as males may have matured
some time before they mated, especially where low seahorse densities or a skewed sex ratio reduced
mating opportunities. Such error would result in an overestimation of size at onset of maturity
(Foster&Vincent 2004). Ideally size at first maturity should be defined as size when 50% of the
males in a population first breed; this point can only be deduced from meticulous behavioral analysis
in the field or dissection of testes in destructive sampling.
Conservation concern and pragmatism also mean that female size at maturity is most likely
estimated by assuming females mature at the same size as males (Foster&Vincent 2004). Methods
for determining onset of female maturity were even more varied than those for males, and include the
size at which ovaries appeared (Kanou&Kohno 2001), the size of the smallest recorded female with
hydrated eggs (Nguyen&Do 1996) and the size of the smallest recorded female to release her eggs (Cai
et al 1984a). All these methods require either dissection of females in destructive sampling or
meticulous behavioural analysis in the field.
Overfishing assessments for seahorses can differ based on how length at maturity is defined, a
variable that is often the cornerstone of data-poor assessment methods; comparing size at maturity to
size at which 50% of specimens are retained in fishing gear is a common data-poor assessment method
for teleosts (e.g. Rueda&Defeo 2003; Foster&Vincent 2005; Kuparinen et al 2009; Foster&Vincent
2010). Length at maturity can be defined as size at physical maturity or size at onset of reproductive
activity. For seahorses, physical maturity is not always indicative of behavioural or physiological
maturity (Cai et al 1984; Morgan&Vincent 2013). Studies have shown this to be the case for H. comes
in the Philippines (Morgan&Vincent 2013), and H. kelloggi, H. spinosissimus and H. trimaculatus in
Malaysia (Lawson et al 2015) (see Table 2).
In the Malaysian study, height at first capture was either similar to or greater than height at physical
maturity for all species. This could suggest that, on average, seahorses were able to reproduce before
becoming vulnerable to capture. However, when height at first capture was compared to height at
reproductive activity, it seems that all three species were being captured well before they actually
started reproducing and are therefore unable to contribute to the next generation. Therefore, the
common practice of using external indicators of maturity for seahorses (e.g. H. trimaculatus:
Murugan et al 2009; H. kelloggi: Lourie et al 1999; H. spinosissimus: Nguyen&Do 1996) would
underestimate potential for fishing impact. Ideally, length at maturity should always be defined
as the point where reproductive activity begins. This is especially true for rare or endangered species
where maturity is often determined externally [e.g. skates and rays: Estalles et al 2011; fin whales:
Aguilar&Lockyer 1987; leatherback turtles: Stewart et al 2007] (as cited in Lawson et al 2015).
15
Timing and length of breeding season
The timing and length of the breeding season for seahorses varied with location, and could be
influenced by environmental parameters such as light, temperature and food availability (Bye
1984). Hippocampus trimaculatus had a peak in breeding from March to May in the China Sea
(Truong&Nga 1995), but bred consistently year round ex situ if temperatures were kept constant (Cai et
al 1984a). Pregnant H. comes were found year round in the Philippines, where water temperatures were
fairly constant, but with a peak in the number of pregnant males between July and December,
corresponding to the rainy season (Perante et al 2002). Any one individual animal may have mated for
only a portion of the entire breeding period (Foster&Vincent 2004).
Mating patterns
All seahorse species appeared to be monogamous within a single breeding cycle, the male
accepting eggs from only one female (Foster&Vincent 2004) (Table 3). Monogamy probably acts to
increase the reproductive success of fishes found in low densities, that have low mobility, and that
depend on camouflage as a defense against predation (Barlow 1984, 1988; Vincent&Sadler 1995).
Seahorses may have experienced increased reproductive efficiency from mating with the same partner,
resulting in larger broods and reduced time spent on courtship (Foster&Vincent 2004).
Table 3. The occurrence of social groupings and mating patterns for seahorse species found in the
Philippines. The nature of study is indicated (ex situ, in situ).
Species
H. bargibanti
H. barbouri
H. comes
H. histrix
H. denise
H. kelloggi
H. kuda
H. pontohi (H. severnsi)
Social grouping
Pairs (in situ)
Mating pattern
References
Tackett&Tackett 1997
Pairs (in situ)
Pairs (in situ)
Pairs
Monogamous
Perante et al 2002
Kuiter&Debelius 1994
Lourie&Kuiter 2008
Monogamous
Mi 1993
Lourie&Kuiter 2008
Pairs
H. spinosissimus (H. alatus)
H. trimaculatus
Monogamy, where it occurred, appeared to be reinforced by daily greetings (Foster&Vincent 2004).
Morning interactions continued all through the pregnancy, and may have helped synchronize female
egg preparation to the end of male pregnancy. On the day the male gave birth, or the next day, the
routine greeting was prolonged into a courtship and mating. Given their inferred dependence on
camouflage, it was surprising that seahorse courtships in situ were colourful, active and lengthy, lasting
up to 9 hours (Vincent&Sadler 1995).
16
Egg and clutch size
In general for seahorses, larger eggs produced larger young. A study of 11 seahorse species found
that the dry weight of individual eggs was positively correlated with the dry weight of individual young
(Vincent 1990).
Recorded female clutch sizes (total number of eggs deposited or dropped in one mating) ranged from
five (Vincent 1990) to over 1000 eggs (Teixeira&Musick 2001). Comparative analyses of clutch size
were precluded by the great variation in methods used to determine clutch size, with some studies
reporting the size of dropped clutches (Vincent 1990; Lawrence 1996), and others using histology of
the ovaries (Strawn 1958; Boisseau 1967); this latter approach is problematic because seahorse ovaries
spiral out, with eggs constantly maturing and being shed from the outer layer (Wallace&Selman 1981).
Direct measurements of egg transfer would only be possible by intrusion into the male‟s pouch,
probably through destructive sampling. The difficulty in measuring clutch size was clear from the fact
that three of the five estimates of maximum clutch size were smaller than the maximum brood size,
despite monogamy within a particular reproductive cycle, for all species.
Pregnancy
Seahorses invest heavily in the development of each of their young. During mating the female
seahorse deposits her entire clutch of eggs in the male‟s brood pouch, where they are fertilized
(ensuring paternity), whereupon the male seals the pouch shut (Foster&Vincent 2004). Both male and
female seahorses exhibit visible evidence of having mated, as the female girth diminishes and the male
pouch fills (Vincent&Sadler 1995).
Seahorse embryos develop in a marsupium that acts much like the mammalian uterus. The developing
embryos are protected and provided with oxygen through a capillary network, while the pouch acts as
an adaptation chamber with the osmolarity of the fluid inside the pouch changing from that of body
fluids to that of salt water as pregnancy progresses (Linton&Soloff 1964). The male hormone prolactin
in the pouch initiates enzymatic conversion of proteins of vitellogenic (maternal) origin which nourish
the embryos (Boisseau 1967), along with male-contributed inorganic compounds (Linton&Soloff
1964). Waste products diffuse out into the male‟s blood stream for removal (Linton&Soloff 1964).
After fertilization, the pouch becomes spongy, vascularized and distended (Wetzel&Wourms 1991).
The eggs induce pits in the wall of the pouch which become compartmentalized and then are enveloped
in epithelial tissue until the end of yolk absorption (Boisseau 1967; Wetzel&Wourms 1991).
Across seahorse species the duration of the male’s pregnancy (gestation duration) ranged from
approximately 9 to 45 days, depending on species and water temperature (Foster&Vincent 2004).
Males of all species studied to date went through several pregnancies in a single breeding season, the
number of pregnancies depending on the length of brooding and the length of the season: for example
individual male H. comes were observed to undergo repeated pregnancies during a year (Perante et al
2002).
It is possible to calculate the maximum possible number of young produced by a pair of
seahorses in a given year. Assuming that males became pregnant the day after giving birth, then the
number of days available for breeding divided by average gestation duration produces an estimate of
the maximum possible number of pregnancy events per year for a species. This multiplied by the
17
maximum possible brood size gives an estimate of the maximum annual reproductive output for a
species. Estimates ranged from approximately 388 ± 172 for H. comes (Morgan 2007) to over 29,000
young for H. kuda (Vincent&Sadler 1995).
Young and brood
At the end of pregnancy males go into labor (usually at night), actively forcing the brood out of his
pouch for hours (Vincent 1990). Young resemble miniature adult seahorses, complete with hardened
fin rays, trunk rings and pigmentation (Boisseau 1967; Gomon&Neira 1998; Mi et al 1998). They are
independent from birth and receive no further parental care.
Total reproductive success is ideally calculated as the total number of offspring that reach sexual
maturity from the lifetime output of an individual. This is the product of the number of offspring
produced per mating event, number of mating events per season, number of reproductive seasons and
offspring survival (Clutton-Brock 1988). The latter two components are very difficult to measure for
wild fish because an individual can seldom be tracked throughout its life. As a result, presumed
indicators of reproductive success that are easier to measure are employed, such as number and
size of offspring (Wootton 1990; Cole&Sadovy 1995; Vincent&Giles 2003).
Brood size is the number of young per pregnancy released by a male in one birth cycle. Males of
most seahorse species produced about 100–300 young per pregnancy (Foster&Vincent 2004). Bigger
seahorses produce more young across species; maximum reported brood size was positively related
to maximum body size across species.
Larger parents may also produce fitter young. Large parents of H. kuda are known to produce
offspring with postnatal growth that is significantly higher than the offspring from younger and smaller
parents (Dzyuba et al 2006). Under ex situ conditions, the young from larger parents also exhibited
increased rates of survivorship, relative to the young from smaller parents (Dzyuba et al 2006).
Researchers have also observed that large H. comes males produce both a greater number of young and
larger offspring than smaller fathers (S. Morgan, unpub data).
Research needed for conservation and management
Distribution
The distribution of most seahorse species in the Philippines remains poorly defined – both across
the Philippines and more specifically by depth and habitat (see Figure 5, Annex II.1-18). It is
important to understand where the seahorses are so we can evaluate overlap with both pressures (such
as fishing effort) and management measures (such as MPAs). Understanding partitioning of habitat by
size and/or age classes, or life history stage, can be important for developing management strategies,
especially when addressing the effects of non-selective fishing gear. For example, a greater
understanding of how seahorses segregate by size or sex would enable spatial management of trawling
and use of other non-selective gear to reduce indiscriminate fishing pressure on vulnerable cohorts or
classes. If reproductively active animals were concentrated in particular areas (e.g. Baum et al 2003),
then trawling could be redirected away from these regions during important breeding periods. Also, if
sub-adult seahorses were found in shallower water than adult seahorses (as is the case with H. comes in
18
the Philippines, Perante et al 1998), then elimination of trawling activities from shallow zones might
reduce the risk of recruitment overfishing.
Movement
Understanding seahorse movement is also important for evaluating pressures and the potential
utility of management responses. Seahorses may recover particularly slowly if inferences that their
limited mobility and dispersal anchor the continuum of fish movement hold true (Jennings 2000).
Nonetheless, the small home ranges of H. comes mean that existing populations will be secure within
MPAs, since only animals on the edge should be vulnerable to fishing pressure (Chapman&Kramer
2000).
Population size
There are no available population estimates for seahorses in the Philippines such that population
inferences must instead often be drawn from trade surveys (See report on “Exploitation, trade,
conservation and management of seahorses in the Philippines” for details). While fishers‟ and
traders‟ reports and records of changes in trade volumes are invaluable, they often lack information on
the effort involved in obtaining the animals, thus diminishing the worth of the data for population
estimates.
Priority research for seahorses in the Philippines includes obtaining long-term population or
catch time series. Insight into seahorse population health, the adverse impacts of stresses such as
fishing practices, and the effectiveness of management tools, can be found by monitoring seahorse
populations or catches over time for changes in any of the following parameters:
 Geographic distribution (presence/absence across space).
 Relative abundance [population size and/or catch per unit effort (CPUE)].
 Mean size of animals.
 Frequency of male pregnancy (indicates disruption of breeding activities).
 Sex ratio.
Monitoring for indicators of adverse impacts from fishing activities can occur on two levels: 1)
Population monitoring – usually consists of underwater surveys of seahorse populations (using
SCUBA or snorkel), but may also involve using pushnets or other gears to systematically survey
seahorses in shallow waters. Project Seahorse has a toolkit for underwater seahorse monitoring,
available at www.projectseahorse.org/NDF and www.iseahorse.org/trends-underwater, and can provide
guidance for Parties wishing to try other means. 2) Fisheries monitoring – monitor catches, including
discards where possible – or at least landings. The key to fisheries dependent monitoring is to collect
information on fishing effort – the data are only truly useful and dependable if they are accompanied
by a measure of effort. Project Seahorse has a toolkit for monitoring seahorse landings at ports,
available at www.projectseahorse.org/NDF and www.iseahorse.org/trends-landings. There are of
course many other approaches to fisheries dependent monitoring, such as on-board observers,
deployment of Vessel Monitoring Systems (VMS) and/or onboard cameras.
19
Survival
Data on natural mortality/survival rates of seahorses, particularly if age or stage specific, are
important parameters for modeling population viability and devising management plans
(Macpherson et al 2000), but are virtually nonexistent for most Philippines seahorses (Foster&Vincent
2004).
Fishing mortality remains virtually unknown for most seahorse populations, despite the
importance of such data in formulating catch guidelines for a sustainable fishery. Some research
indicates that fishing mortality of fish that have spawned once must be lower than natural mortality for
the fishery to be sustainable (Myers&Mertz 1998). For H. comes, even with high estimates of natural
mortality in some parts of their range, fishing mortality exceeded those rates (Martin-Smith et al 2004,
Meeuwig et al 2006). Presumably as a consequence, fishers reported that H. comes catches on one
Philippines barrier reef had declined 70% in the 10 years from 1985 to 1995 (Vincent 1996), with
associated changes in the length–frequency distribution of the catch (Perante et al 1998); more data of
greater precision are needed to determine whether fishers had begun targeting smaller seahorses or
whether the size structure of the seahorse populations had changed under exploitation. See the report
“Conservation and management of seahorses in the Philippines” for more information on fishery
impacts on seahorses in the Philippines.
Reproduction
A greater understanding of seahorse mating patterns and reproduction is important for
conservation (Foster&Vincent 2004). Exploitation could disrupt seahorse social structure by
disturbing pairs more quickly than they are established. Removing a member of a monogamous pair
could decrease short-term reproductive output, by leaving the remaining animal without a partner, and
possibly by reducing the size of its later broods if familiarity enhances brood success. Sex-selective
fishing would also have important effects, especially in monogamous populations where members
of the more abundant sex might be less likely to find a mate thereafter. More needs to be discovered
about how mating patterns respond to environmental and social parameters.
More research on age- or size-specific reproductive output could allow us to tailor fisheries plans
more usefully (Foster&Vincent 2004). For example, if further research confirmed that brood size
increased with male size, then maximum size limits might be considered for fisheries, in order to allow
the most fecund animals to continue reproduction. Realistically, however, such a management measure,
no matter how apparently desirable, might prove politically difficult to implement given that larger
seahorses fetch a higher price (Vincent 1996).
Conclusions
While present knowledge of seahorse life history for species found in the Philippines is incomplete,
existing information indicates that seahorse populations are commonly vulnerable to overexploitation,
whether direct or indirect: low population densities mean that seahorses may have trouble finding a
new partner (Allee effects: e.g. Knowlton 1992); low mobility and small home range sizes mean that
seahorses may be slow to recolonize overexploited areas (although this may be offset by planktonic
dispersal of juveniles); possible low rates of natural mortality mean that heavy fishing will place
unsustainable pressure on the population; monogamy in most species means that a widowed partner
20
may stop reproducing, at least temporarily; male brooding means that survival of the young in
marsupio depends on the survival of the male; and a small brood size limits the potential reproductive
rate of the pair (although this may be offset by frequent spawning and enhanced juvenile survival
through parental care) (Foster&Vincent 2004). Even if seahorses are returned to the water after being
caught in non-selective gear, they may still experience deleterious effects that include physical injury,
habitat damage, removal from home ranges and disturbance of pair bonds (Davis 2002; Baum et al
2003).
For example, monogamy and site fidelity may render H. comes – the most well studied seahorses
in the Philippines – particularly vulnerable to over-exploitation. Removal of one partner would
compromise the reproductive rate of the other, and over-fished areas would probably not be replenished
quickly through immigration from elsewhere. On the other hand, it‟s continuous breeding and
nocturnal activity might make H. comes less vulnerable to fishing than other seahorses with seasonal
breeding and diurnal activity (Perante et al 2002). Furthermore, the small home ranges of H. comes
reported here should mean that existing populations will be secure within MPAs, since only animals on
the edge should be vulnerable to fishing pressure (Chapman&Kramer 2000).
In the context of conservation management, variation in life history parameters across the genus
requires thorough analysis, in order to assess the relative vulnerability of different species to
exploitation and habitat damage. With such information, management initiatives can be improved for
the long-term security of wild seahorse populations (Foster&Vincent 2004).
Acknowledgements
Funding for this report was provided by SOS-Save Our Species (www.SaveOurSpecies.org), Guylian
Chocolates Belgium (www.guylian.be) and an anonymous donor.
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27
Annex I. Description of seahorses in the Philippines
Species
Description
H. barbouri (Jordan Two pairs of cheek spines
&
Richardson Prominent nose spine
1908)
Stripes on snout
Spine in front of coronet
H.
bargibanti Coronet: Rounded knob
(Whitley 1970)
Spines: Irregular bulbous tubercles
scattered over body and tail; single,
prominent rounded eye spine;
single, low rounded cheek spine
Snout: extremely short
Photo
Reference
iSeahorse:
Common
Large
Seahorses of
SE
Lourie et al
(2004)
28
H. comes (Cantor Blunt spines
1850)
Double cheek spines
Prominent nose spine
Low coronet
Striped tail (can look blotchy)
iSeahorse:
Common
Large
Seahorses of
SE
H. denise (Lourie Limited number of tubercles on the
and Randall 2003) body
Coronet: No raised coronet
Spines: none
Lourie et al
(2004)
29
H. histrix
1856)
(Kaup Long snout
Single cheek spine
Sharp spines on coronet
Prominent nose spine
Sharp, often dark-tipped
spines
body
iSeahorse:
Common
Large
Seahorses of
SE
H. kelloggi (Jordan Distinct coronet
& Snyder 1902)
Narrow body (compared to H. kuda)
Thick truck rings
Long, back-pointing, rounded cheek
spine
iSeahorse:
Common
Large
Seahorses of
SE
30
H. kuda (Bleeker Deep body (fatter compared to H.
1852)
kelloggi)
Low/round coronet
Spines are rounded bumps
iSeahorse:
Common
Large
Seahorses of
SE
H.
pontohi
severnsi)
iSeahorse.org
, Lourie and
Kuiter
(2008)
(H. Body is small and slender with a
prehensile tail
head is relatively large
eyes are prominent
moderately long snout, no bulbous
tip
tail has red bands
31
H. spinosissimus (H. Low/no nose spine
alatus)
(Weber Short snout (compared to H. histrix)
1913)
Single or double cheek spines
Blunter and shorter body spines
than H. histrix
iSeahorse:
Common
Large
Seahorses of
SE
H.
trimaculatus Low coronet
(Leach 1814)
3 dark spots (sometimes)
Hook-like cheek spine
iSeahorse:
Common
Large
Seahorses of
SE
32
Annex II. Regional maps of seahorse species distribution with delineated municipal
waters boundaries, different habitats, fishery area closures and temporal
restrictions in the Philippines.
II.1 National Capital Region (NCR)
33
II.2 Region 1 (Ilocos Region)
34
II.3 Region 2 (Cagayan Valley)
35
II.4 Region 3 (Central Luzon)
36
II.5 Region 4-A (Calabarzon)
37
II.6.1 Region 4-B (Mimaropa)
38
II.6.2 Region 4-B (Mimaropa)
39
II.7 Region 5 (Bicol Region)
40
II.8 Region 6 (Western Visayas)
41
II.9 Region 7 (Central Visayas)
42
II.10 Region 18 (Negros Island Region)
43
II.11 Region 8 (Eastern Visayas)
44
II.12 Region 9 (Zamboanga Peninsula)
45
II.13 Region 10 (Northern Mindanao)
46
II.14 Region 11 (Davao Region)
47
II.15 Region 12 (Soccsksargen)
48
II.16 Region Caraga
49
II.17 Autonomous Region in Muslim Mindanao – Eastern
50
II.18 Autonomous Region in Muslim Mindanao – Western
51
Annex III. Observed geographic distribution, depth & habitat of seahorses in the Philippines.
Species
H. barbouri
H. bargibanti
Distribution
Philippines
Depth
Max reported
depth at 10m
Habitat
shallow seagrass beds,
clinging to hard corals
Reference
Lourie et al, (2004), Kuiter
(2000), Lourie et al (1999),
Wilson and Vincent (1998)
Cuyo Island, Culion
Island, Palawan,
Zamboanga (?),
Lourie et al, 1999
Sagay, Negros
Occidental
SEAFDEC Stock Enhancement
Malapascua, Cebu
Apo Island and Dauin,
Negros Oriental
iSeahorse.org,
Philippines
Mabini, Batangas
Malapascua, Cebu
Mactan, Cebu
Anda, Bohol
Samal Island, Davao
Cabilao, Bohol
Panglao, Bohol
Puerto Galera, Oriental
Mindoro
Typically found at only known to occur on
16-40m depth
gorgonian corals of
genus Muricella
Lourie et al (2004), Tackett and
Tackett (1997), Gomon (1997)
iSeahorse.org,
52
H. comes
Masbate
Lonos, Romblon
Dauin, Negros Oriental
Philippines
Northwestern Bohol
Tablas Strait
Northern Masbate
Bantayan Island, Cebu
Malapascua, Cebu
Moalboal, Cebu
Sogod Bay
Sibulan, Neg. Or
Dumaguete City, Neg.
Or
Dauin, Neg Or.
Iloilo
Gingoog Bay
Samal Island, Davao
Bien Unido, Bohol
Typically found at
<10m depth,
maximum
reported depth
20m
Ducks Diving Romblon
atmosphereresorts.com
Lourie et al (2004), Lourie
(2001), Kuiter (2000), Perante
et al (2002), Perante et al
(1998)
coral reef, sponge
gardens, kelp, floating
Sargassum; thought to
prefer Sargassum as
juveniles, moving to
corals and sponges when
older
corals, sponges,
Perante et al (1998)
Sargassum
iSeahorse.org,
Juveniles generally used
macroalgal holdfasts;
adults used a greater
diversity of specialized
microhabitats including
branching sponges,
branching corals and tall
seagrass
Morgan and Vincent (2007)
53
H. denise
Eastern Samar, Iloilo,
Leyte, Masbate,
Northern Samar,
Quezon, Samar,
Sorsogon, Surigano
Del Norte and
Zambales
Philippines
H. histrix
Tablas Strait
Romblon Pass
Malapascua, Cebu
Moalboal, Cebu
Cebu Strait
Cabilao, Bohol
Panglao, Bohol
Samal Island, Davao
Philippines
Northwestern Bohol
Mabini, Batangas
Puerto Galera, Oriental
Mindoro
Tablas Strait
Romblon, Romblon
Daanbantayan, Cebu
Morgan and Lourie (2006),
Maypa unpublished data,
typically found at
13-90 m depth,
in association with
gorgonian seafans
identified as Annella
reticulata, Muricella sp.
And Echinogorgia sp.
Lourie et al (2004), Lourie and
Randall (2003)
iSeahorse.org,
typically found >6
m depth,
maximum
reported depth
20 m
seagrass bed, weedy
Lourie et al, 1999
rocky reefs, sponges, soft Kuiter and Debelius (1994),
bottom with soft corals
Kuiter (2000)
and sponges
sea whips, sea fans,
sponges in deeper
waters
Perante et al (1998)
iSeahorse.org,
54
H. kelloggi
Cebu Strait
Dumaguete City, Neg
Or.
Dauin, Neg Or.
Anda, Bohol
Samal Island, Davao
Puerto Princesa,
Palawan
Concepcion, Iloilo
Jagna, Bohol
Philippines
Maximum
reported depth
152 m
Northwestern Bohol
H. kuda
Jolo
Northern Cebu
(Daanbantayan),
Dumaguete City, Neg.
Or
Philippines
Philippines
typically found at
0-8 m depth,
maximum
reported depth
55 m
shallow inshore
waters up to 40-
Associated with
gorgonian corals and sea
whips, soft
in open and deeper
waters
deep water
Lourie et al ( 2004), Lourie
(2001), Choo and Liew (2003)
coastal bays and
lagoons, in seagrass and
in floating weeds, sandy
sediments in rocky
littoral zone, macroalgae
and seagrass beds,
branches, muddy
bottoms, mangroves,
estuaries, harbours,
lower reaches of rivers
(can inhabit brackish
waters)
found in mangroves,
seagrass beds, estuaries
Lourie et al (2004), Lourie
(2001), Randall (1996), Kuiter
and Debelius (1994), Lee
(1983), Kuiter (2000)
Perante et al (1998)
Lourie et al (1999)
iSeahorse.org,
Lourie et al (1999)
55
50m deep
H. pontohi (H.
severnsi)
H. spinosissimus
Northwestern Bohol
Aparri
Masinloc, Zambales
Puerto Galera, Or
Mindoro
Bantayan Island, Cebu
Danajon Bank (Bohol)
Moalboal, Cebu
Dumaguete, Neg Or
Dauin, Neg Or
Bacong, Neg Or
Siaton, Neg Or
Apo Island, Neg Or
Samal Island, Davao
Sarangani, Southern
Mindanao
Romblon, Romblon
Maigo, Lanao Del
Norte
Iloilo
Romblon, Romblon
Philippines
Holotype and
paratype
specimens found
at 16 m and 12 m
depth
respectively,
recorded
between 11-25m
Typically found at
and on steep mud
slopes; also found in
open water and attached
to drifting Sargassum up
to 20km from shore
seagrasses
Perante et al (1998)
iSeahorse.org,
Found among algae,
bryozoans, hydroid
crops and specifically
the coralline algae
Halimeda and hydroid
Aglaphenia cupressina
iSeahorse.org, Lourie and
Kuiter (2008)
octocorals, macro algae,
Lourie et al (2004), Lourie
56
(H. alatus)
H. trimaculatus
>8 m depth,
maximum
reported depth
70 m,
Cavite
Bohol (Danajon Bank)
Puerto Galera, Or
Mindoro
Malapascua, Cebu
Philippines
Bohol
not hard corals, sand but (2001), Weber and de Beaufort
not mud, near coral reefs (1922), Nguyen and Do (1996)
on sandy bottoms
muddy or sandy bottoms Lourie et al (1999)
and coral reefs
iSeahorse.org,
Typically found at
> 10 m depth,
maximum
reported depth
100 m
trawled from less
than 20 m
octocorals, macro algae,
not hard corals, gravel,
sandy bottoms around
shallow reefs, muddy
bottoms in deeper
waters
gravel and sandy bottom
habitats
Lourie et al (2004), Lourie
(2001), Choo and Liew (2003),
Nguyen and Do (2006)
Lourie et al (1999)