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Bay Pipefish (Sygnathus leptorhynchus)
By Dr. Abby L.
Schwarz
Bay Pipefish
Taxonomy and description
The bay
pipefish, also known as the slender-nosed pipefish, has the
scientific name Syngnathus leptorhynchus. It is also
known by the synonym griseolineatus. The bay pipefish
is in the Order
Gasterosteiformes which
includes
seahorses, other species of pipefishes, sticklebacks,
tubesnouts and sea moths. All have armor plates of some sort
and small mouths. Members of the family
Syngnathidae,
containing 200 species of pipefishes and 25 species of
seahorses, all have characteristic armor, cryptic coloration,
and secretive
behaviour. They
lack streamlining and speed, but are nevertheless very
successful and are found world-wide in shallow marine waters
and sometimes in fresh water.
Hybridization can be an important source of novel genetic
variation, and may increase the adaptive potential of wild
populations. While hybridization has not been previously
reported in syngnathid fishes, the sympatric occurrence of
closely related species at high densities has increased
interest in the probability of interspecies mating in this
group. Five species of Syngnathus frequent eelgrass
beds along the southern California coast. Exceptionally high
levels of genetic diversity occur in southern populations of
Syngnathus leptorhynchus. For example, S.
leptorhynchus and S. auliscus occur in high
densities at a site in San Diego Bay where their population
genetics have been examined by means of microsatellite
genotyping and mitochondrial sequencing (Wilson 2006a). Adult
hybrids were not found in the study population, but analysis
of male broods indicated that mating was occurring between the
two species. The lack of pre-mating isolating mechanisms
between these two relatives suggested that hybridization may
be common in sympatric species of Syngnathus (Wilson
2006a).
The bay
pipefish is long and thin (standard length 2.5-33 cm or
longer); in fact, it is one of the most elongated species in
the genus. Females grow larger than males (Hart 1973, Bayer
1980). Scales are replaced by bony rings. There is no lateral
line canal. The snout is tube-like and the mouth is terminal.
Pelvic fins are absent in S. leptorhynchus and many
other pipefish, and the remaining fins are minute. There is
clear sexual dimorphism: the males have an abdominal brood
pouch conspicuously lacking in females. As well, only the
females have an anal fin (Hart 1973).
Bay
pipefish propel themselves by undulating the dorsal fin and
vibrating the pectoral fins while assuming various body
postures (Hart 1973). Colouration varies from pale green to
dark green or brown depending on their surroundings. Some
species can change colour to match their environment but it is
not known whether the bay pipefish is one of these.
Bay Pipefish
Distribution
Pipefishes
generally inhabit warm and temperate seas, and several species
are found in fresh water.
The bay pipefish, Syngnathus leptorhynchus, is a
near-shore Pacific coast species with an exceptionally wide
latitudinal distribution, ranging from Bahia Santa Maria, Baja
California to Prince William Sound, Alaska. S.
leptorhynchus is experiencing a range expansion at the
northern limit of its range, consistent with colonization from
southern populations (Wilson 2006b).
In British
Columbia it has been recorded from the Strait of Georgia,
Loughborough Inlet, and the Queen Charlotte Islands (Hart
1973). It is common in eelgrass meadows,
where it is effectively camouflaged by its greenish color, its
long, thin shape resembling an eelgrass leaf, and its ability
to orient itself parallel to eelgrass leaves.
It is sometimes taken in shallow offshore waters, but may be
found at depths of 30 m.
Bay Pipefish
Life history, behaviour and research
S.
leptorhynchus,
like other pipefishes, feeds on large quantities of tiny
crustaceans (e.g. amphipods, copepods, decapod larvae).
As in seahorses, the mouth acts like a vacuum cleaner, sucking
in plankton food, rather than biting its prey.
They can
suck in small crustaceans from some distance away after
locating the prey precisely with their binocular vision (Moyle
and Cech 2004).
In B.C., spawning in the bay pipefish appears to occur in late
spring and in summer. Egg-carrying males have been found as
early as late May, and young as late as August. Bay pipefish
are sex-role reversed. Hart (1973) describes an elaborate
reproductive ritual in which the male shakes himself, nods his
head, and periodically assumes a rigid vertical S position,
while the female twines herself around him and then transfers
the fertilized eggs to the male’s brood pouch.
Male
pipefish carry the developing young for several weeks. Large
males can be pregnant with over 900 young. Because this
mating system requires a high investment of energy by the
males, they can be very choosy about their mates, preferring
larger females (which produce larger eggs) (Berglund 1995).
Some species exhibit intra-female competition for males. There
is no information on this for the bay pipefish, but a report
of a female-biased sex ratio in one study population (Bayer
1980) suggests that this is a possibility.
Some
species are monogamous; others allow multiple females to lay
eggs in their pouches (Jones and Avise 1997). Bayer (2006)
states that S. leptorhynchus males mate with more than
one female, but it is not known whether a female mates with
more than one male.
Embryonic
development is completed in the male’s pouch and the young are
released at about 19 mm length (Hart 1973) as swimming
juveniles.
Several syngnathids can change sex, but S. leptorhynchus
does not appear to be one of these (Vincent et al.
1992).
Bay Pipefish
Conservation
The
greatest potential threat to pipefish is loss of eelgrass
habitat. There is no commercial fishery for pipefishes, and
many of the details of their biology and requirements are not
well known. However, like seahorses, pipefishes are collected
from the wild for the Chinese medicinal trade, although
apparently in somewhat smaller quantities. Pipefishes are
considered more medicinally potent than seahorses; ground and
mixed with various herbs, they are used for “whole-body”
treatment, whereas the less-potent seahorse is generally used
to target specific ailments. The demand for pipefishes is
currently being met by collection from the wild, but
continuing this practice will lead to the same decline of
pipefish that has occurred with seahorses (Burhans no date).
References
Bayer,
R. D.
1980. Size, seasonality and sex ratios of the bay pipefish (Syngnathus
leptorhynchus) in Oregon. Northwest Science 54:161–167.
Berglund,
A., 1995. Many mates make male pipefish choosy. Behaviour
32: 213-218.
Brunsman,
D. and F. Ratti, 1979. Coos Bay Estuary Inventory and Study.
Coos County Planning Dept, Oregon. https://scholarsbank.uoregon.edu/xmlui/handle/1794/5913.
Burhans, R.A. (no date; post-1998) Pipefish husbandry and
propagation.
http://www.utahreefs.com/articles/Pipefish_final.pdf.
(Note: Robert A. Burhans is the Aquarium Curator at the Birch
Aquarium, Scripps Institution of Oceanography, Univ. Calif.
San Diego.)
Hart, J.L., 1973. Pacific Fishes of Canada. Pp. 278-279.
Fish. Res. Bd Can., Bull. 180. 740 pp. Ottawa.
Jones,
A.G. and J.C. Avise, 1997.
Polygynandry
in the dusky pipefish Syngnathus floridae revealed by
microsatellite DNA markers. Evolution 51: 1611-1622.
Lamb, A.
and B.P. Hanby, 2005. Marine Life of the Pacific Northwest.
Harbour Publ., Madeira Park BC.
Moyle, P.B.
and J.J. Cech Jr., 2004. Fishes: An Introduction to
Ichthyology. 5e. Prentice-Hall, NJ.
Vincent,
A., I. Ahnesjo, A. Berglund and G. Rosenqvist, 1992. Pipefish
and seahorses: Are they all sex role reversed? Trends in
Ecology and Evolution 7:237–241.
Wilson,
A.B., 2006a. Interspecies mating in sympatric species of
Syngnathus pipefish.
Molecular Ecology 15 (3): 809-824.
Wilson,
A.B., 2006b. Genetic signature of recent glaciation on
populations of a near-shore marine fish species (Syngnathus
leptorhynchus). Molec. Ecology 15 (7): 1857-1871.
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