The IUCN/SSC Shark Specialist Group
Shark News 1: June 1994
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The Fishery Status of Chimaeroids
(Chondrichthyes, Holocephali),
Summary Report
Dominique Didier
The Academy of Natural Sciences, Philadelphia
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Of the 34 known species of chimaeroids, only the three species of
callorhynchid fishes (Family Callorhynchidae) are part of a commercial
fishery. These species occur only in the Southern Hemisphere and are
fished off thecoast of New Zealand, south-eastern Australia and Tasmania,
western and southern Africa, and in South America off the coasts of Chile,
Peru, and Argentina. In these regions callorhynchids comprise a small,
but not insignificant, portion of the coastal fishery where they are
important as food fishes and sometimes frozen for export. Other species
of chimaeroids, of the Families Chimaeridae and Rhinochimaeridae, are
taken as by-catch and used forfish meal. In addition, the oil rendered from
the livers of these fishes is known to be a fine lubricant; however, further
data are unavailable regarding this aspect of their utilization.
Pacific Ratfish Hydrolagus colliei
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In New Zealand the fishery for elephant fishes Callorhinchus milii
occurs primarily off the eastern and southern coasts of the South Island,
with the major landings occurring in the Canterbury Bight region. This is
an inshore fishery (up to 150m depths) in which fishes are caught by
either bottom trawl or gill net and is comprised of two-person
operated 12-20m vessels. Elephant fishes are seasonally abundant,
coincident with spawning migrations, and the majority are fished from
the months of October to February. Recently the Maximum Constant
Yield (MCY) for C. milii was estimated to be 400t; however, data from
1983-1992 show that the fishery has consistently exceeded this level
(Duffy, 1992). Unfortunately, very little is known about the biology of
these fishes which seem to be relatively late-maturing, slow-growing
fishes with males maturing at three years and females at 4.5 year:
(Sullivan, 1978). In particular, the reproduction and spawning behavior
of all chimaeroid fishes is poorly understood and fecundity estimates are
currently unavailable. Without further data it is difficult to determine
whether or not the fishery can maintain current catch levels; however, it
is likely that this species is over-fished in New Zealand waters (Duffy
1992).
A major threat to all chimaeroid fishes is overfishing in the absence
of adequate information on population movements and fluctuations
abundance, fecundity, and life span. The only chimaeroids for which
there is a regulated fishery are the callorhynchid fishes. Other chimaeroids
are caught as a by-catch, but there are few, if any, records of the numbers
landed and/or their utilization, for example, the targeting of a non-quota
species, Hydrolagus novaezealandiae, in Cloudy Bay, New Zealand
(Duffy, 1990), and the large numbers of longnose chimaeras,
Neoharriotta pinnata and Rhinochimaera atlantica, which are caught
and not used by hake trawlers off the African coast (Campagno et al., 1989).
There is a real danger in overfishing these species without an
adequate assessment, of their population structure and the potential
consequences of such fishery practices.
A second threat to chimaeroid fishes is the potential destruction of
spawning habitats, especially habitats that are as yet undetermined to be
critical spawning areas, because very few chimaeroid spawning sites
have been positively identified. As an example, egg cases of the New
Zealand elephant fish, that were once quite abundant in trawls along the
southeastern coast of New Zealand, are currently only known from the
Mariborough sounds. This apparent shift in spawning areas may be due
to bottom trawling, but appropriate baseline data are not available to
verify this hypothesis. However, it is now apparent that the spawning sites
for C. milii may be very limited, yet pressure continues to be exerted to
utilize these critical spawning areas for commercial enterprises. The
results of such activities are unknown and one can only guess at the
potential disruption to populations of C. milii.
References:
Compagno, L.J.V., D.A. Ebert, and M.J. Smale (1989) Guide to the sharks
and rays of Southern Africa. New Holland Press, 158 pp.
Di Giacomo, E., and M. R. Perier (1991) Evaluacion de la biomasa y
explotacion comercial del pez gallo Callorhynchus callorhynchus
en el Golfo San Matias, Argentina. Frente Maritimo 9: 7-13.
Duffy, C. (1990) Comment on marine conservation issues in the
Mariborough Sounds relevant to the proposed Central/Chalanger
region fisheries management plan.
Duffy, C. (1992) Inshore 2 fishery assessment working group report.
McCregor, G.A. (1988) in Baird, G.G., and McKoy, J.L. (eds) Papers from
the workshop to review fish stock assessments for the 1987-88
New Zealand fishing year, pp.74-77.
Sullivan, K.J. (1978) Age and growth of the elephant
fish Callorhinchus milii (Elasmobranchii:
Callorhynchidae). N.Z.J. Mar. Fw. Res. 11:745-753.
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